Methylation marker combination for diagnosing gastrointestinal cancer and application thereof

Abstract

The invention belongs to the technical field of biological medicine, and particularly relates to a DNA methylation marker combination for gastrointestinal cancer combined diagnosis and application of the DNA methylation marker combination. A blood sample is adopted for detection, development is convenient, and the compliance of clinical gastrointestinal cancer screening patients is improved. According to the application, the DNA methylation region related to the gastrointestinal cancer is screened, modeling is carried out in combination with a machine learning algorithm, and then a comprehensive diagnosis model is constructed by utilizing a logistic regression algorithm, so that the model not only can realize combined diagnosis of the gastrointestinal cancer, but also can carry out tissue traceability on cancer tissue, and the screening performance is remarkably improved. In an independent external verification set, the gastrointestinal cancer combined diagnosis sensitivity and specificity are 86% (95% CI: 82%-89%) and 93% (95% CI: 88%-98%) respectively, and the AUC is 0.943 (95% CI: 0.920-0.966); wherein the sensitivity of the intestinal cancer and the sensitivity of the gastric cancer are 84% (95% CI: 79%-88%) and 89% (95% CI: 84%-94%) respectively, and the AUC is 0.936 (95% CI: 0.909-0.962) and 0.954 (95% CI: 0.929-0.979) respectively; the tumor marker is obviously superior to the traditional serum tumor marker.

Description

Technical Field

[0001] This invention belongs to the field of biomedical technology, specifically relating to a combination of DNA methylation markers for combined diagnosis of gastrointestinal cancer or for tracing tissues from patients with positive combined diagnosis of gastrointestinal cancer and their application. Background Technology

[0002] Gastric cancer (GC) is the third leading cause of cancer-related death and the fifth most common type of malignant tumor worldwide (Bray F, Ferlay J, Soerjomataram I, et al. Global cancerstatistics 2018: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries[J] CA: a Cancer Journal For Clinicians, 2018, 68(6): 394-424.). Because early symptoms of gastrointestinal tumors are often subtle and insidious, most patients are already in the middle or late stages when obvious symptoms appear, and many also have lymph node metastasis. Specifically, 80% of early-stage gastric cancers are asymptomatic, while some patients may experience indigestion. The most common symptoms of advanced-stage gastric cancer are weight loss (approximately 60%) and upper abdominal pain (50%), along with anemia, loss of appetite, anorexia, and fatigue. In some developed countries, early diagnosis of gastric cancer (GC) reaches 50%, with a 5-year survival rate as high as 90% (Luo M, Li L. Clinical utility of miniprobe endoscopic ultrasonography for prediction of invasion depth of early gastric cancer: A meta-analysis of diagnostic test from PRISMA guideline [J]. Medicine (Baltimore), 2019, 98(6):e14430.). Therefore, early diagnosis of GC can significantly improve the overall survival rate of cancer patients. Early gastric cancer (EGC) is defined as a tumor lesion confined to the mucosa or submucosa, without considering regional lymph node metastasis. Studies have shown that the overall survival rate of EGC treated by endoscopy or surgery exceeds 96%, while the 5-year survival rate of advanced gastric cancer is only 20%-40%. EGC is highly heterogeneous, and most patients are asymptomatic before disease progression. Currently, EGC screening is performed using endoscopy combined with pathology, which is the gold standard for diagnosing EGC, but tissue samples must be obtained invasively through endoscopic biopsy or surgery. Many patients are unwilling to undergo this invasive intervention and prefer other testing methods.

[0003] Circulating biomarkers used for the diagnosis and prognosis of gastrointestinal tract infections (GC) include routine blood tests, biochemical assays, and tumor marker tests. These indicators are routinely obtained and non-invasive. Some tumor markers, including carcinoembryonic antigen (CEA), carbohydrate antigen 199 (CA199), and alpha-fetoprotein (AFP), are used as early detection tools, but they lack specificity for EGC, resulting in low sensitivity and specificity for early detection. Some circulating molecules (including microRNAs, lncRNAs, and cireRNAs) may offer novel strategies for EGC diagnosis, but their application in large-scale EG-C screening is limited.

[0004] Colorectal cancer (CRC) is the third most common cancer worldwide. Its incidence rises significantly from age 50, peaks at 75-80, and then declines slowly. However, colorectal cancer in young people under 30 is not uncommon. Early-onset colorectal cancer (EO-CRC), defined as CRC diagnosed before the age of 50, is a significant risk factor. Compared to older patients, younger CRC patients have a higher risk of local or distant metastasis. The causes are multifaceted, including family history and / or hereditary cancer syndromes, as well as lifestyle and environmental factors.

[0005] Colorectal cancer has an insidious onset, initially showing only a positive fecal occult blood test. Later symptoms may include changes in bowel habits and stool characteristics, abdominal pain, and a rectal mass discovered on digital rectal examination. Other symptoms may include anemia, low-grade fever, progressive weight loss, cachexia, and ascites. Unexplained weight loss and anemia are also frequently reported. By the time these symptoms appear, the disease is often no longer in its early stages, and most gastrointestinal cancer patients only seek medical attention after symptoms appear. This is partly due to insufficient patient awareness and a lack of risk consciousness, and partly because the symptoms are nonspecific; for example, hemorrhoid bleeding can easily be confused with colorectal cancer. Therefore, the survival rate for patients with colorectal cancer is currently low.

[0006] Gastrointestinal cancer (GCCR) is a common malignant tumor in clinical practice, with high incidence and mortality rates. Diagnostic methods for GCCR mainly include imaging examinations, endoscopy, pathological examination, tumor marker testing, and recently developed molecular biological examinations. Pathological diagnosis is mostly performed when the tumor has progressed to a certain stage, relying on tumor burden, and the process is complex. Endoscopy is the gold standard for GCCR screening, but as an invasive procedure, it requires advanced equipment and technology, has poor patient compliance, and is difficult to implement on a large scale. Furthermore, as an invasive procedure, it is not suitable for early screening. Current oncology decision-making tools are limited, which may lead to overdiagnosis, false positives, and low specificity (especially for serum biomarkers such as CA125). Traditional serum tumor markers such as CEA and CA19-9 have low accuracy, especially for early GCCR or precancerous lesions, resulting in unsatisfactory screening performance. Traditional clinical diagnosis relies mainly on imaging examinations, which are not suitable for early screening and diagnosis. Molecular biology and instrumental diagnostic methods in cancer management are designed for screening, early detection, risk stratification, selection of effective treatments, monitoring of treatment response, and prevention of disease recurrence. Early detection rates and prognoses are significantly improved when patients proactively undergo gastrointestinal cancer screening even when asymptomatic. Therefore, new methods for diagnosing gastrointestinal cancer are urgently needed. Summary of the Invention

[0007] This invention discovers that by screening DNA methylation regions associated with gastrointestinal cancer and combining them with machine learning algorithms for modeling, a comprehensive diagnostic model is constructed using logistic regression. This model not only enables the joint diagnosis of gastrointestinal cancer but also allows for tissue tracing of cancerous tissues, significantly improving screening performance. Based on this, this invention was completed.

[0008] In a first aspect, the present invention provides a combination of DNA methylation region markers for the combined diagnosis of patients with gastrointestinal cancer, wherein the DNA methylation regions are shown below (chromosome: start position - termination position (positive and negative strands), model coefficients; reference genome is hg19): chr1:101005348-101005457(+),-0.0005; chr1:111822043-111822068(+),-0.0257; chr1:115880340-115880444(+),0.0046; chr1:115880774-115880918(+),0.0750; chr1:1267541-1267655(+),-0.0309; chr1:146544255-146544336(+),-0.0031; chr1:156616751-156616858(+),0.0480; chr1:156616757-156616858(+),0.0629; chr1:179712359-179712461(+),-0.0581; chr1:200007570-200007623(+),-0.0551; chr1:210111614-210111717(+),0.0514; chr1:210861187-210861240(+),-0.0572; chr1:228196347-228196464(+),-0.0064; chr1:231297871-231298065(+),-0.0206; chr1:237205214-237205384(+),0.0325; chr1:2984735-2984923(+),0.0622; chr1:3567263-3567362(+),-0.0055; chr1:37500489-37500604(-),-0.0026; chr1:57889475-57889560(+),-0.0386; chr1:57890544-57890636(+),0.0617; chr1:58715450-58715630(+),-0.0345; chr1:91189140-91189226(+),0.0350; chr1:942439-942554(-),0.0201; chr1:969213-969306(+),0.0088; chr10:101292437-101292507(+),0.0167; chr10:102821760-102821863(+),-0.0416; chr10:104170638-104170718(+),-0.0270; chr10:104535792-104535854(+),0.0010; chr10:11206792-11206892(+),-0.0022; chr10:11298996-11299109(+),-0.0419; chr10:118897355-118897465(+),-0.0903; chr10:124907383-124907460(+),0.0735; chr10:125425608-125425787(+),0.0149; chr10:129534131-129534182(+),-0.0249; chr10:129534217-129534227(+),-0.0321; chr10:129535249-129535448(+),-0.0337; chr10:133110253-133110449(+),0.0314; chr10:133945888-133945989(-),0.1011; chr10:21799262-21799340(+),0.0236; chr10:2992148-2992213(+),-0.0370; chr10:42863495-42863594(+),0.0496; chr10:497316-497377(+),0.0162; chr10:50817603-50817691(-),0.0568; chr10:5735301-5735376(+),0.0782; chr10:60936417-60936494(+),0.0073; chr10:63213323-63213396(+),-0.0668; chr10:7453507-7453688(+),0.0813; chr10:8096985-8097087(+),0.0547; chr10:92616821-92616922(+),0.0690; chr10:94825771-94825874(+),0.0082; chr11:125036365-125036480(-),0.0245; chr11:128563614-128563740(+),0.0046; chr11:1364958-1365050(+),-0.0533; chr11:19463880-19463962(+),-0.0465; chr11:32450101-32450178(+),0.0946; chr11:89867679-89867799(+),0.0483; chr12:103351959-103352020(+),-0.0010; chr12:111472276-111472432(+),-0.0026; chr12:114838688-114838866(+),0.0585; chr12:114847088-114847247(+),-0.0350; chr12:31079601-31079694(+),0.0059; chr12:58014758-58014901(+),0.0513; chr12:75601803-75601863(+),0.0186; chr13:112723421-112723529(+),0.0073; chr13:112760028-112760137(+),0.0138; chr13:28503166-28503254(+),0.0074; chr13:37005452-37005551(+),0.0447; chr13:43148278-43148376(+),0.0348; chr13:50701592-50701695(+),0.0840; chr13:50706583-50706740(+),-0.0684; chr13:79181525-79181613(+),-0.0561; chr13:84452930-84453027(+),0.0023; chr13:95365416-95365509(+),0.0830; chr13:96204764-96204930(+),-0.0073; chr14:102247977-102248168(+),-0.0264; chr14:29235136-29235244(+),0.0944; chr14:52734431-52734619(+),0.0034; chr14:60973773-60973848(+),-0.0138; chr14:70346126-70346223(+),0.0001; chr14:77737530-77737638(-),0.0937; chr15:35047355-35047467(+),0.0041; chr15:55880900-55881023(+),-0.0182; chr15:60297636-60297747(+),0.0453; chr15:83316143-83316320(+),0.0000; chr15:86233163-86233265(+),-0.0609; chr16:215788-215904(+),0.0089; chr16:22825046-22825131(+),0.0252; chr16:22825046-22825195(+),-0.0342; chr16:23847259-23847369(+),0.0032; chr16:23847913-23848052(+),-0.0011; chr16:3355458-3355649(+),0.0788; chr16:54969087-54969202(+),0.0659; chr16:6533106-6533219(+),-0.0065; chr16:87441478-87441597(+),-0.0339; chr17:21281441-21281538(+),0.0498; chr17:26699109-26699216(+),-0.0015; chr17:32907337-32907485(-),-0.0313; chr17:37381380-37381565(+),0.0357; chr17:38347738-38347910(+),0.0353; chr17:43339416-43339594(+),-0.0083; chr17:57642721-57642782(+),0.0523; chr17:6616768-6616955(+),-0.0005; chr17:71161157-71161242(+),-0.0181; chr17:71161157-71161273(+),-0.0326; chr17:71161160-71161356(+),-0.0012; chr17:73696459-73696509(+),-0.0613; chr18:11752447-11752637(+),-0.0753; chr18:12911263-12911456(+),0.0608; chr18:43913655-43913782(+),-0.0006; chr18:49868176-49868270(+),-0.0208; chr18:70210374-70210483(+),0.0211; chr18:74962039-74962220(+),-0.0454; chr18:76739185-76739275(+),-0.0035; chr18:9707978-9708064(+),0.0009; chr19:12624368-12624466(+),-0.0192; chr19:18901666-18901751(+),0.0034; chr19:19322596-19322778(+),-0.0367; chr19:21657691-21657756(+),0.0158; chr19:30016073-30016224(+),-0.0565; chr19:30019604-30019741(+),0.0453; chr19:34113353-34113549(+),0.0989; chr19:34113992-34114145(+),0.0269; chr19:37407118-37407310(+),-0.0018; chr19:48947507-48947589(-),0.0025; chr19:54481368-54481469(+),0.0399; chr19:55864365-55864432(+),-0.0703; chr19:57683743-57683885(+),0.0322; chr19:58446745-58446832(+),-0.0466; chr19:59092612-59092711(+),-0.0218; chr19:59092612-59092713(+),-0.0090; chr2:105470463-105470559(-),0.0154; chr2:109746080-109746196(+),-0.0168; chr2:111876660-111876844(+),0.0460; chr2:154728978-154729150(+),0.0537; chr2:154728979-154729151(-),-0.0352; chr2:158300389-158300485(+),0.0740; chr2:164593182-164593290(+),-0.0037; chr2:175199771-175199881(+),0.0146; chr2:175208534-175208649(+),-0.0079; chr2:175208535-175208650(-),-0.0662; chr2:176936377-176936526(+),-0.0073; chr2:176987367-176987468(+),0.0074; chr2:177014849-177014966(+),0.0634; chr2:177014909-177014959(+),0.0031; chr2:177014962-177014962(+),0.0253; chr2:177014966-177014966(+),0.0555; chr2:182322168-182322349(+),-0.0038; chr2:182548728-182548820(+),-0.0419; chr2:186603317-186603436(+),0.1254; chr2:187713531-187713615(+),0.1319; chr2:198650887-198651076(+),0.0012; chr2:200327284-200327391(-),0.0985; chr2:200333935-200334085(+),-0.0332; chr2:219736167-219736343(+),0.0441; chr2:220313414-220313521(+),0.0846; chr2:45155175-45155274(+),-0.0242; chr2:45161274-45161361(+),0.0084; chr2:45161485-45161598(+),0.0327; chr2:63284536-63284574(+),-0.0486; chr2:71115928-71116067(+),-0.0167; chr2:71134586-71134728(+),-0.0812; chr2:74726809-74726894(+),-0.0376; chr2:79823717-79823775(+),-0.0541; chr2:80531590-80531701(+),0.0036; chr2:98963526-98963585(+),0.0474; chr20:21694778-21694882(+),0.0749; chr20:25065319-25065512(+),0.0158; chr20:34894558-34894699(+),0.0056; chr20:37434060-37434246(+),-0.0126; chr20:39316972-39317131(+),0.1057; chr20:41818269-41818356(+),0.0067; chr20:41818270-41818357(-),0.0049; chr20:41818358-41818358(+),0.0035; chr20:43439365-43439545(+),-0.0003; chr20:44657849-44658033(+),0.0180; chr20:54580583-54580678(-),0.0496; chr20:58180518-58180676(+),0.0550; chr20:59047467-59047504(+),0.0217; chr20:61885162-61885362(+),0.0015; chr20:61885236-61885382(+),0.0050; chr21:32253729-32253791(+),-0.0373; chr21:36042323-36042420(+),0.0028; chr21:38378539-38378654(+),-0.0601; chr22:17082492-17082591(+),-0.0205; chr22:48885347-48885527(+),0.0378; chr3:124860685-124860774(-),0.0013; chr3:125076278-125076419(+),-0.0096; chr3:128211444-128211625(+),0.0775; chr3:129694156-129694255(+),0.0668; chr3:147077593-147077636(+),-0.0196; chr3:147077671-147077671(+),-0.0154; chr3:147106536-147106615(+),0.0549; chr3:147136879-147136974(+),0.0604; chr3:14852659-14852829(+),-0.0013; chr3:187387552-187387740(+),0.0286; chr3:192126735-192126914(+),0.0024; chr3:22413862-22414048(+),-0.0044; chr3:36422016-36422160(-),-0.0413; chr3:68981828-68981912(+),0.0866; chr4:110223999-110224179(+),-0.0096; chr4:113444246-113444347(+),0.0253; chr4:134070291-134070441(+),0.0359; chr4:154710353-154710429(+),-0.0458; chr4:156680311-156680489(+),-0.0018; chr4:165878038-165878140(-),0.0266; chr4:174452401-174452520(+),0.0134; chr4:184826879-184827046(+),0.0136; chr4:185940824-185940933(+),-0.0642; chr4:37246791-37246892(+),-0.0401; chr4:4864738-4864833(+),0.0034; chr4:4866439-4866510(+),-0.0261; chr4:55991752-55991943(+),-0.0084; chr4:56685918-56686028(+),-0.0379; chr4:5710278-5710372(+),0.0743; chr4:6009978-6010164(+),0.0296; chr4:779476-779644(+),-0.0065; chr4:93226349-93226479(+),-0.0310; chr4:93227164-93227276(+),-0.0023; chr4:93227173-93227298(+),-0.0337; chr5:113698463-113698564(+),0.0461; chr5:134363516-134363637(+),-0.0597; chr5:136834419-136834526(+),0.0312; chr5:140180964-140181120(+),0.0518; chr5:140235578-140235586(+),0.0452; chr5:140235596-140235680(+),0.0245; chr5:140501277-140501412(+),0.0316; chr5:140616432-140616495(+),-0.0251; chr5:140619567-140619586(+),0.0827; chr5:140750132-140750260(+),0.0581; chr5:140778363-140778456(+),0.0072; chr5:140793394-140793474(-),0.0622; chr5:140794921-140795036(+),-0.0029; chr5:140810051-140810161(+),0.0399; chr5:140810337-140810519(+),-0.0171; chr5:140810707-140810902(+),-0.0809; chr5:140811003-140811189(+),0.0946; chr5:140811253-140811314(+),0.0270; chr5:150400298-150400395(+),-0.0084; chr5:1594239-1594343(+),0.0350; chr5:178017824-178017937(+),0.0147; chr5:178772285-178772385(+),0.0026; chr5:1876140-1876312(-),-0.0488; chr5:2756101-2756209(+),0.0126; chr5:36693315-36693389(+),-0.0020; chr5:36693316-36693390(-),0.0174; chr5:37838271-37838462(+),0.0248; chr5:38258351-38258441(+),0.0084; chr5:38258451-38258451(+),-0.0465; chr5:63257038-63257131(-),-0.0238; chr5:83679842-83679992(+),0.0011; chr5:87974388-87974464(+),-0.0387; chr6:105388635-105388731(+),0.0318; chr6:105388636-105388732(-),0.0736; chr6:105389544-105389599(+),0.0242; chr6:106429545-106429610(+),-0.0016; chr6:12750205-12750312(+),0.0096; chr6:133561886-133561993(+),-0.0456; chr6:154360648-154360763(+),-0.0110; chr6:1594362-1594466(+),-0.0703; chr6:166074730-166074837(+),0.0025; chr6:166259960-166260013(-),-0.0466; chr6:25652351-25652383(+),0.1015; chr6:25652390-25652467(+),0.0660; chr6:28602881-28603037(+),-0.0625; chr6:28956719-28956804(+),0.0136; chr6:29521507-29521696(-),-0.0297; chr6:29760705-29760805(+),0.0002; chr6:32064053-32064246(+),-0.0481; chr6:32064054-32064240(-),0.0105; chr6:32064161-32064345(+),0.0506; chr6:392463-392652(+),-0.0070; chr6:62996627-62996702(+),-0.0302; chr6:72596076-72596176(+),0.0161; chr6:84418339-84418529(+),0.0042; chr6:84418625-84418820(+),-0.0007; chr6:84562836-84562986(+),-0.0589; chr6:84563330-84563485(+),0.0015; chr7:101006223-101006312(+),-0.0464; chr7:12151615-12151694(+),0.0224; chr7:134143408-134143588(+),0.0011; chr7:145813009-145813107(-),-0.0392; chr7:153445143-153445227(-),0.0259; chr7:153584609-153584662(+),0.0669; chr7:154861985-154862073(+),0.0509; chr7:155255303-155255415(+),-0.0271; chr7:155302286-155302439(+),-0.0313; chr7:157405932-157406128(+),0.0848; chr7:158362870-158362983(+),0.0693; chr7:19157613-19157777(+),-0.0057; chr7:19813204-19813300(-),-0.0097; chr7:43153143-43153311(+),-0.0032; chr7:4832112-4832271(+),-0.0140; chr7:63361049-63361178(+),0.0779; chr7:63924688-63924770(+),0.0665; chr7:79082017-79082131(+),0.0014; chr7:88389247-88389342(+),0.0269; chr7:97361201-97361201(+),-0.0571; chr7:97361241-97361294(+),0.0661; chr7:97361748-97361814(+),0.0305; chr8:128306933-128306986(+),-0.0048; chr8:145107102-145107282(+),0.0525; chr8:17271006-17271119(+),-0.0017; chr8:38326278-38326373(+),0.0463; chr8:53477783-53477975(+),-0.0552; chr8:53852599-53852677(+),0.0075; chr8:54790449-54790617(-),0.0768; chr8:58906997-58907185(+),-0.0024; chr8:72469457-72469561(-),0.0707; chr8:85095995-85096056(+),0.0355; chr8:93114861-93115008(+),-0.0552; chr9:95571917-95572015(+),0.0539.

[0009] Furthermore, the combined diagnosis of gastrointestinal cancer patients is performed using formula (I), which is as follows: Equation (I); Where p is the combined diagnostic score; x is the methylation level of the i-th region; a is the coefficient of the i-th region; and b is the cutoff value, with the cutoff value for the combined diagnostic model being -0.3235.

[0010] In a second aspect, the present invention provides the application of DNA methylation region markers in constructing a model for the combined diagnosis of gastrointestinal cancer patients; the DNA methylation regions are as shown in the first aspect of the present invention.

[0011] Furthermore, the model for the combined diagnosis of gastrointestinal cancer patients was constructed using a logistic regression algorithm.

[0012] Furthermore, the model for the combined diagnosis of gastrointestinal cancer patients uses formula (I) for combined diagnosis, as follows: Equation (I); Where p is the combined diagnostic score; x is the methylation level of the i-th region; a is the coefficient of the i-th region; and b is the cutoff value, with the cutoff value for the combined diagnostic model being -0.3235.

[0013] Furthermore, when the combined diagnostic score is ≥0.7045, the patient is considered to be positive for gastrointestinal cancer.

[0014] Thirdly, the present invention provides a combined diagnostic model for gastrointestinal cancer, wherein the combined diagnostic model uses formula (I) for combined diagnosis, and formula (I) is as follows: Equation (I); Where p is the combined diagnostic score; x is the methylation level of the i-th region; a is the coefficient of the i-th region; and b is the cutoff value, with the cutoff value for the combined diagnostic model being -0.3235.

[0015] Furthermore, when the combined diagnostic score is ≥0.7045, the patient is determined to be positive for gastrointestinal cancer.

[0016] Furthermore, the DNA methylation region at the methylation region level is as shown in the first aspect of the present invention.

[0017] Fourthly, this invention provides a combination of DNA methylation region markers for tissue tracing in patients with positive combined diagnostic results for gastrointestinal cancer. The DNA methylation regions are shown below (chromosome: start position - end position (positive and negative strands), model coefficients; reference genome is hg19): chr10:102821615-102821760(+),0.0972; chr10:102821760-102821863(+),0.5378; chr10:110084660-110084660(+),-0.0101; chr10:11059485-11059577(+),0.1803; chr10:11206756-11206870(+),-0.0023; chr10:125751892-125751983(+),-0.0964; chr10:126135176-126135176(+),-0.2675; chr10:128839223-128839268(+),-0.4072; chr10:134407859-134407942(+),-0.4237; chr10:134936768-134936952(+),-0.3069; chr10:1444541-1444644(+),-0.0402; chr10:18429261-18429357(+),-0.0033; chr10:3848384-3848384(+),-0.1028; chr10:42863495-42863594(+),0.2987; chr10:84719878-84719878(+),-0.4264; chr10:90343087-90343266(+),-0.4462; chr10:92616821-92616922(+),0.1977; chr11:116781288-116781303(+),-0.4244; chr11:1577982-1578096(+),0.1354; chr11:32450101-32450178(+),0.1031; chr11:64140993-64141100(+),-0.0874; chr11:65352249-65352361(+),0.0724; chr11:65408468-65408566(+),-0.4074; chr11:93586725-93586779(+),0.6223; chr11:94965294-94965452(+),0.5301; chr12:108168987-108169087(+),-0.4854; chr12:117470875-117471008(+),-0.5256; chr12:20521953-20521984(+),-0.4218; chr12:3947996-3948103(+),-0.5159; chr12:42682155-42682248(+),-0.1198; chr12:52626831-52626996(+),0.4033; chr12:52695568-52695659(+),0.0038; chr12:54867371-54867454(+),0.0710; chr12:64062485-64062588(+),0.0667; chr13:105792252-105792399(+),0.0329; chr13:112630580-112630695(+),0.0495; chr13:113229295-113229334(+),-0.0620; chr13:114261808-114261945(+),-0.0305; chr13:114814086-114814269(+),-0.1133; chr13:24807829-24807902(+),0.2099; chr13:46742691-46742802(+),0.4641; chr13:46742722-46742802(+),0.2958; chr13:79168546-79168613(+),0.4630; chr13:96204486-96204538(+),0.2446; chr13:114814644-114814725(-),-0.2457; chr14:36988118-36988316(+),-0.0634; chr14:60981173-60981254(+),0.2314; chr14:65068414-65068504(+),-0.0675; chr14:73929570-73929597(+),-0.4206; chr14:94211818-94211818(+),-0.0164; chr15:21995905-21996010(+),-0.1613; chr15:31115806-31115883(+),-0.0319; chr15:41695378-41695434(+),-0.3231; chr15:57592036-57592109(+),0.3200; chr15:73371746-73371777(+),-0.0744; chr15:78556880-78556988(+),-0.0560; chr15:99409411-99409548(+),-0.4970; chr15:99644973-99645065(+),-0.1252; chr15:99645031-99645189(+),-0.4031; chr16:1032704-1032813(+),-0.1430; chr16:1143467-1143583(+),-0.0745; chr16:16463448-16463550(+),-0.2147; chr16:32214126-32214243(+),0.4874; chr16:49902279-49902383(+),0.0509; chr16:53407722-53407808(+),-0.2238; chr16:5486224-5486268(+),0.1094; chr16:67686881-67687000(+),-0.3527; chr16:7703876-7703947(+),-0.1115; chr16:88844377-88844511(+),0.1408; chr17:1686671-1686791(+),-0.3267; chr17:1839990-1840090(+),0.1172; chr17:1961238-1961346(+),0.0748; chr17:40664817-40664940(+),0.3777; chr17:56736698-56736814(+),0.0153; chr17:57642721-57642782(+),-0.0543; chr17:77721583-77721680(+),0.2778; chr17:77970135-77970193(+),-0.4630; chr17:79058765-79058953(+),-0.3541; chr17:81020155-81020268(+),0.0347; chr17:47301643-47301839(-),-0.4527; chr17:56327070-56327219(-),0.0085; chr18:19756935-19757022(+),0.0614; chr18:35145983-35146142(+),0.0000; chr19:14276879-14276921(+),-0.3621; chr19:1468376-1468466(+),0.2639; chr19:1524352-1524449(+),0.2912; chr19:17409380-17409380(+),0.1858; chr19:36800795-36800878(+),0.5242; chr19:37329795-37329956(+),-0.0151; chr19:38713144-38713341(+),0.1636; chr19:48206028-48206119(+),-0.0566; chr19:52514445-52514445(+),0.1829; chr19:55864365-55864432(+),-0.1679; chr19:56510897-56511059(+),0.1288; chr19:58629780-58629871(+),-0.0435; chr19:58952150-58952275(+),0.3525; chr19:681413-681532(+),-0.5265; chr19:852990-853077(+),-0.3836; chr1:1052600-1052664(+),-0.1112; chr1:1109580-1109676(+),0.7246; chr1:121260880-121260987(+),0.1424; chr1:147806141-147806231(+),-0.2979; chr1:149399899-149400002(+),0.3912; chr1:155220137-155220318(+),-0.0027; chr1:16085371-16085466(+),0.0021; chr1:19600378-19600484(+),-0.3721; chr1:200211351-200211412(+),-0.2202; chr1:202091865-202091933(+),-0.5375; chr1:2058881-2058997(+),-0.3355; chr1:214328927-214328927(+),-0.4523; chr1:231297600-231297627(+),0.2970; chr1:235805308-235805500(+),-0.4010; chr1:25257500-25257599(+),-0.0378; chr1:34630844-34630999(+),-0.1203; chr1:906428-906518(+),-0.4635; chr1:91182726-91182821(+),-0.1616; chr1:95179390-95179461(+),-0.0831; chr1:969767-969922(+),-0.0072; chr1:223936750-223936921(-),0.1101; chr20:34249256-34249284(+),-0.7203; chr20:35448345-35448426(+),0.5571; chr20:37355218-37355288(+),0.6217; chr20:45179345-45179413(+),0.0418; chr20:54824550-54824646(+),-0.0512; chr20:60540388-60540388(+),-0.1573; chr20:60540469-60540486(+),-0.1645; chr20:61148853-61148952(+),-0.0134; chr20:44657778-44657886(-),0.8005; chr21:42799066-42799191(+),0.0569; chr21:46074556-46074651(+),-0.2504; chr22:29076076-29076237(+),0.0786; chr22:38610728-38610840(+),-0.3446; chr22:51169920-51170018(+),-0.0022; chr2:128432961-128433113(+),-0.7507; chr2:16805059-16805111(+),0.0637; chr2:176994996-176995102(+),0.1854; chr2:228670471-228670606(+),-0.3971; chr2:228670481-228670606(+),-0.3342; chr2:231855440-231855620(+),-0.0807; chr2:233323868-233323957(+),0.0235; chr2:23749087-23749151(+),-0.1099; chr2:241719559-241719678(+),-0.1085; chr2:39319447-39319447(+),-0.3423; chr2:43054655-43054735(+),0.0558; chr2:47382366-47382557(+),0.3247; chr2:63283937-63284038(+),-0.1813; chr2:87036908-87037000(+),0.1165; chr2:9549245-9549336(+),0.2988; chr3:11537591-11537626(+),0.5794; chr3:142666439-142666543(+),-0.2328; chr3:149388151-149388180(+),-0.4188; chr3:155394292-155394303(+),0.2918; chr3:181441513-181441623(+),-0.5377; chr3:181444485-181444580(+),-0.0363; chr3:196705855-196705970(+),0.2446; chr3:37940037-37940044(+),0.4209; chr3:61550540-61550687(+),0.5871; chr3:75445459-75445600(+),-0.4330; chr3:99357581-99357626(+),0.3264; chr3:129407531-129407549(-),-0.3681; chr3:142666440-142666544(-),-0.0854; chr4:1004247-1004289(+),-0.3553; chr4:100738066-100738222(+),-0.4564; chr4:101438778-101438836(+),-0.2542; chr4:183935046-183935104(+),0.1450; chr4:87515380-87515579(+),-0.1843; chr5:107167398-107167498(+),-0.0739; chr5:1123034-1123123(+),-0.1479; chr5:115152851-115152938(+),0.0867; chr5:121647923-121648117(+),0.0036; chr5:124034239-124034288(+),0.0601; chr5:140214100-140214179(+),0.0537; chr5:140502891-140502903(+),-0.0061; chr5:140502918-140502975(+),0.2235; chr5:141242687-141242742(+),-0.3330; chr5:157098465-157098557(+),-0.2737; chr5:1594501-1594638(+),-0.2058; chr5:35919491-35919491(+),-0.1063; chr5:37837377-37837555(+),0.4285; chr5:40681794-40681990(+),-0.0070; chr6:105388624-105388731(+),-0.1501; chr6:117586483-117586593(+),-0.4364; chr6:143586006-143586006(+),-0.3659; chr6:158399108-158399203(+),-0.4167; chr6:166232960-166233106(+),-0.4302; chr6:167524238-167524296(+),-0.6199; chr6:29593382-29593490(+),-0.4392; chr6:29704545-29704545(+),-0.4907; chr6:30227967-30228063(+),-0.0516; chr6:31857007-31857100(+),0.0874; chr6:32009327-32009422(+),-0.1232; chr6:44773667-44773754(+),0.0538; chr6:7847437-7847496(+),-0.5400; chr6:25652352-25652460(-),-0.2905; chr6:32064054-32064247(-),-0.5971; chr7:1311498-1311575(+),-0.3327; chr7:1337106-1337204(+),0.0329; chr7:155283738-155283817(+),-0.1038; chr7:157406032-157406186(+),-0.1405; chr7:157691177-157691208(+),-0.7094; chr7:158352173-158352211(+),-0.0723; chr7:1604448-1604524(+),0.0305; chr7:19157650-19157777(+),-0.0188; chr7:27204639-27204732(+),-0.1162; chr7:4287212-4287276(+),0.2124; chr7:45002418-45002582(+),-0.2852; chr7:45002651-45002810(+),-0.1964; chr7:601257-601446(+),0.4147; chr7:906726-906799(+),0.2407; chr7:100807411-100807599(-),0.3871; chr7:1112980-1113108(-),-0.0833; chr7:158531641-158531695(-),-0.1322; chr8:103540766-103540879(+),-0.2519; chr8:10587935-10588071(+),0.1174; chr8:11561628-11561758(+),-0.0326; chr8:120058164-120058222(+),0.4292; chr8:144359234-144359334(+),-0.2928; chr8:145555844-145555974(+),-0.1827; chr8:18744378-18744513(+),-0.1777; chr8:1992498-1992606(+),0.2455; chr8:2075696-2075841(+),0.8527; chr8:2263237-2263427(+),-0.3316; chr8:26307416-26307504(+),0.0289; chr8:58906986-58907140(+),0.0618; chr8:58906997-58907185(+),0.0102; chr8:67344571-67344763(+),-0.0113; chr8:71135804-71135895(+),-0.1917; chr8:975247-975385(+),0.3308; chr9:139716115-139716224(+),-0.1570; chr9:140311820-140312018(+),-0.6809.

[0018] Furthermore, the tissue tracing of patients with a positive combined diagnosis of gastrointestinal cancer is performed using formula (II), which is as follows: Formula (II); Where p is the probability value predicted as colorectal cancer; x is the methylation level of the i-th region; a is the coefficient of the i-th region; and b is the cutoff value, with the cutoff value for the tissue origination model being -0.3443.

[0019] Furthermore, the tissue tracing of patients with positive combined diagnosis of gastrointestinal cancer showed a probability value of 1-p for predicting gastric cancer.

[0020] Fifthly, the present invention provides the application of a combination of DNA methylation region markers in constructing a model for tracing the origin of tissues from patients with positive combined diagnostic results for gastrointestinal cancer; the DNA methylation regions are as shown in the fourth aspect of the present invention.

[0021] Furthermore, the model for tracing the tissues of patients with positive combined diagnoses of gastrointestinal cancer was constructed using a logistic regression algorithm.

[0022] Furthermore, the tissue source tracing of the patients with a positive combined diagnosis of gastrointestinal cancer is performed using formula (II), which is as follows: Formula (II); Where p is the probability value predicted as colorectal cancer; x is the methylation level of the i-th region; a is the coefficient of the i-th region; and b is the cutoff value, with the cutoff value for the tissue origination model being -0.3443.

[0023] Furthermore, the tissue tracing model for patients with positive combined diagnosis of gastrointestinal cancer predicts a probability of 1-p for gastric cancer.

[0024] Sixthly, the present invention provides a tissue tracing model for patients with a positive combined diagnosis of gastrointestinal cancer, wherein the tissue tracing for patients with a positive combined diagnosis of gastrointestinal cancer uses formula (II) for tissue tracing, and formula (II) is as follows: Formula (II); Where p is the probability value predicted as colorectal cancer; x is the methylation level of the i-th region; a is the coefficient of the i-th region; and b is the cutoff value, with the cutoff value for the tissue origination model being -0.3443.

[0025] Furthermore, the tissue tracing model for patients with positive combined diagnosis of gastrointestinal cancer predicts a probability of 1-p for gastric cancer.

[0026] Furthermore, the DNA methylation region at the methylation region level is as shown in the fourth aspect of the present invention.

[0027] Beneficial effects This application uses blood samples for testing, which is convenient to carry out and improves patient compliance in clinical gastrointestinal cancer screening.

[0028] This application discovers that by screening DNA methylation regions associated with gastrointestinal cancer and combining them with machine learning algorithms for modeling, a comprehensive diagnostic model is constructed using logistic regression. This model can not only achieve joint diagnosis of gastrointestinal cancer but also trace the origin of cancerous tissue, significantly improving screening performance. In the validation set, the sensitivity and specificity for joint diagnosis of gastrointestinal cancer were 91% (95% CI: 84%-99%) and 100% (95% CI: 100%-100%), respectively, with an AUC of 0.979 (95% CI: 0.955-1.000). The sensitivity for colorectal cancer and gastric cancer were 90% (95% CI: 79%-100%) and 93% (95% CI: 84%-100%), respectively, with AUCs of 0.988 (95% CI: 0.969-1.000) and 0.971 (95% CI: 0.929-1.000), respectively. In the independent external validation set, the sensitivity and specificity of the combined diagnosis of gastrointestinal cancer were 86% (95% CI: 82%-89%) and 93% (95% CI: 88%-98%), respectively, with an AUC of 0.943 (95% CI: 0.920-0.966). Specifically, the sensitivity for colorectal cancer and gastric cancer were 84% (95% CI: 79%-88%) and 89% (95% CI: 84%-94%), respectively, with AUCs of 0.936 (95% CI: 0.909-0.962) and 0.954 (95% CI: 0.929-0.979), respectively, which were significantly better than traditional serum tumor markers. In the validation set, the tissue origination model achieved 100% (95% CI: 100%–100%) and 83% (95% CI: 69%–97%) accuracy for colorectal cancer and gastric cancer tissue origination, respectively; in the independent external validation set, the accuracy was 83% (95% CI: 78%–88%) and 71% (95% CI: 65%–78%) for colorectal cancer and gastric cancer, respectively. Attached Figure Description

[0029] Figure 1 This is a roadmap for combined diagnostic techniques for gastrointestinal cancer.

[0030] Figure 2 Box plots and ROC curves of the combined diagnostic model for gastrointestinal cancer on the training set.

[0031] Note: A is the box plot of the gastrointestinal cancer combined diagnostic model on the training set; B is the ROC curve of the gastrointestinal cancer combined diagnostic model on the training set; CRC represents colorectal cancer; GC represents gastric cancer.

[0032] Figure 3 Box plots and ROC curves for the combined diagnostic model for gastrointestinal cancer on the validation set.

[0033] Note: A is the box plot of the gastrointestinal cancer combined diagnostic model on the validation set; B is the ROC curve of the gastrointestinal cancer combined diagnostic model on the validation set; CRC represents colorectal cancer; GC represents gastric cancer.

[0034] Figure 4 Box plots and ROC curves for the combined diagnostic model for gastrointestinal cancer on an independent external validation set.

[0035] Note: A is a box plot of the combined diagnostic model for gastrointestinal cancer on an independent external validation set; B is the ROC curve of the combined diagnostic model for gastrointestinal cancer on an independent external validation set; C is the ROC curve of stage 0-II gastrointestinal cancer, stage 0-II gastric cancer, and stage 0-II colorectal cancer; CRC represents colorectal cancer; GC represents gastric cancer; D is the ROC curve of the combined diagnostic model for gastrointestinal cancer and traditional serum tumor markers.

[0036] Figure 5 This is a technical route for tissue tracing in patients with positive combined diagnoses of gastrointestinal cancer.

[0037] Figure 6 Stacked area plot and ROC curve of tissue source tracing model for patients with positive combined diagnosis of gastrointestinal cancer on the training set.

[0038] Note: A is the stacked area plot of the tissue source tracing model for patients with positive combined diagnosis of gastrointestinal cancer in the training set; B is the ROC curve of the tissue source tracing model for patients with positive combined diagnosis of gastrointestinal cancer in the training set; CRC represents colorectal cancer; GC represents gastric cancer.

[0039] Figure 7 Stacked area plot and ROC curve of tissue source tracing model for patients with positive combined diagnosis of gastrointestinal cancer on the validation set.

[0040] Note: A is the stacked area plot of the tissue source tracing model for patients with positive combined diagnosis of gastrointestinal cancer on the validation set; B is the ROC curve of the tissue source tracing model for patients with positive combined diagnosis of gastrointestinal cancer on the validation set; CRC represents colorectal cancer; GC represents gastric cancer.

[0041] Figure 8 Stacked area plot and ROC curve of tissue tracing model for patients with positive combined diagnosis of gastrointestinal cancer on independent external validation set.

[0042] Note: A is the stacked area plot of the tissue source tracing model for patients with positive combined diagnosis of gastrointestinal cancer on the independent external validation set; B is the ROC curve of the tissue source tracing model for patients with positive combined diagnosis of gastrointestinal cancer on the independent external validation set; CRC represents colorectal cancer; GC represents gastric cancer. Detailed Implementation

[0043] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the embodiments described below can be combined with each other as long as they do not conflict with each other.

[0044] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0045] Example 1: Sorting Criteria and Sample Selection A. Inclusion criteria 1. Age range: 30-80 years old; 2. Subjects are able to undergo endoscopic and other related examinations; 3. Healthy control group requires negative endoscopy and / or pathology results, no other cancers, and exclusion of patients with gastrointestinal cancer and precancerous lesions found in previous endoscopic examinations. 4. Patients with different stages of gastric or intestinal cancer must be diagnosed by endoscopy and / or pathological examination, have no concurrent malignant tumors in other systems or organs, and have not undergone surgery, radiotherapy, or chemotherapy before blood collection. 5. After fully understanding the nature of this study, the relevant examination methods, and the risks that may be involved in participating in this study, the participants were able to understand and voluntarily sign the informed consent form.

[0046] B. Exclusion Criteria 1. Blood sample volume is too small, with plasma volume less than 4 mL, making DNA methylation detection impossible; 2. Incomplete information on blood samples (including sample collection time, sample number, subject's age, gender, medical history, imaging results, gastroscopy and pathology results, etc.); 3. Blood sample testing quality control is not up to standard, including samples that are not collected and processed in accordance with requirements, samples that have been repeatedly frozen and thawed, hemolyzed, or contaminated with microorganisms, samples tested using reagents with quality problems (including expired, contaminated, or improperly stored reagents), and other human errors in the test process; 4. Pregnant women, breastfeeding women, or women of childbearing age who are planning to conceive; 5. The researchers believed there were any circumstances that would make them unsuitable for inclusion.

[0047] C. Sample selection for the combined diagnostic model of gastrointestinal cancer Plasma samples were collected from 91 healthy controls, 96 colorectal cancer patients, and 97 gastric cancer patients according to the inclusion and exclusion criteria. DNA methylation was detected using the Twist Human Methylome Panel (approximately 123 Mb, covering 84.2% of CpG island sites in the human genome). The plasma samples were randomly divided into training and validation sets at a ratio of 7:3. The training set included 66 healthy controls, 67 patients with colorectal cancer, and 68 patients with gastric cancer. The validation set included 25 healthy controls, 29 patients with colorectal cancer, and 29 patients with gastric cancer.

[0048] Plasma samples from 113 healthy controls, 225 colorectal cancer patients, and 161 gastric cancer patients, which were collected according to inclusion and exclusion criteria and were different from the training and validation sets, were used for DNA methylation testing as an independent external validation set.

[0049] D. Selection of tissue samples for the source tracing model of patients with positive combined diagnosis of gastrointestinal cancer Plasma samples were collected from 96 patients with colorectal cancer and 97 patients with gastric cancer according to the inclusion and exclusion criteria. DNA methylation was detected using the Twist Human Methylome Panel (approximately 123 Mb, covering 84.2% of CpG island sites in the human genome). The plasma samples were randomly divided into training and validation sets at a ratio of 7:3. The training set included 67 patients with colorectal cancer and 68 patients with gastric cancer; The validation set included 29 patients with colorectal cancer and 29 patients with gastric cancer.

[0050] Plasma samples from 225 colorectal cancer patients and 161 gastric cancer patients, which were collected according to inclusion and exclusion criteria and were different from the training and validation sets, were used for DNA methylation testing as an independent external validation set.

[0051] Example 2: Screening DNA methylation biomarkers related to the combined diagnosis of gastrointestinal cancer from public databases DNA methylation data (Illumina Infinium Human Methylation 450 BeadChip, GSE103186) from 392 colorectal cancer tissues, 104 adjacent colorectal tissues, 383 gastric cancer tissues, and 63 adjacent gastric tissues were downloaded from the public databases TCGA (The Cancer Genome Atlas) and GEO (Gene Expression Omnibus). The DNA methylation data were analyzed using the ChAMP package in R to screen for DNA methylation sites that showed significant differences between cancerous and adjacent tissues. p<0.05, |Δβ|≥0.2), and remove DNA methylation sites located on the X and Y chromosomes, finally obtaining 39661 DNA methylation sites with significant differences in colorectal cancer tissues and 43872 DNA methylation sites with significant differences in gastric cancer tissues. The union of these results yielded 59528 DNA methylation sites related to the joint diagnosis of gastrointestinal cancer.

[0052] Example 3: Combined Diagnostic Model for Gastrointestinal Cancer A. Screening for DNA methylation regions related to the combined diagnosis of gastrointestinal cancer from plasma samples in the training set. For 59,528 DNA methylation sites related to the joint diagnosis of gastrointestinal cancer screened from public databases, in the training set, DNA methylation sites were merged into regions according to the rule that the distance between adjacent CpGs was less than 50 and the Pearson correlation coefficient was greater than 0.5. A Wilcoxon test was used to analyze the differences between 66 healthy controls and 135 gastrointestinal cancer patients (67 with colorectal cancer and 68 with gastric cancer). p The criteria of <0.05 and |Δβ|≥0.01 were used to screen out 17,614 significantly different DNA methylation regions. Then, LASSO feature screening was performed to obtain 311 DNA methylation regions related to the combined diagnosis of gastrointestinal cancer (see the first aspect of the present invention).

[0053] B. Constructing a combined diagnostic model for gastrointestinal cancer using plasma samples from the training set. Logistic regression was used to model 311 DNA methylation regions using machine learning. After model screening, 10-fold cross-validation was used to determine the model hyperparameters. Then, the joint diagnostic score for each sample was calculated according to the standard logistic regression formula (I). The threshold of 0.7045, corresponding to the largest Yaoden index, was taken as the threshold of the joint diagnostic model. A joint diagnostic score ≥ 0.7045 was considered positive for gastrointestinal cancer, and a joint diagnostic score < 0.7045 was considered negative for gastrointestinal cancer.

[0054] The standard logistic regression formula is as follows: Equation (I); Where p is the combined diagnostic score; x is the methylation level of the i-th region; a is the coefficient of the i-th region; and b is the cutoff value, with the cutoff value for the combined diagnostic model being -0.3235.

[0055] C. Validate the performance of the combined diagnostic model for gastrointestinal cancer using plasma samples from the validation set. Using the combined diagnostic model for gastrointestinal cancer determined by the training set above, the standard logistic regression formula (Ⅰ) was used to calculate the combined diagnostic scores of 25 healthy controls and 58 patients with gastrointestinal cancer (29 with colorectal cancer and 29 with gastric cancer) in the validation set. The combined diagnostic results of negative and positive were obtained by comparing them with the threshold of 0.7045.

[0056] D. Validating the performance of the combined diagnostic model for gastrointestinal cancer using independent external validation set plasma samples. Plasma samples from 113 healthy controls, 225 colorectal cancer patients, and 161 gastric cancer patients were collected according to inclusion and exclusion criteria. DNA methylation was performed as an independent external validation set. A gastrointestinal cancer co-diagnostic model was used to calculate the co-diagnostic score for each sample in the independent external validation set. By comparing the score with a threshold of 0.7045, negative and positive co-diagnostic results were obtained to further evaluate the detection performance.

[0057] E. Results of traditional serum tumor markers CEA, CA19-9, CA72-4, AFP, and CA125 detection Samples with results for traditional serum tumor markers CEA, CA19-9, CA72-4, AFP, and CA125 were screened from plasma samples in an independent external validation set, resulting in 152 samples, including 35 healthy controls, 85 colorectal cancer patients, and 32 gastric cancer patients. The detection performance was assessed based on these results.

[0058] F. Test Results In the training set, the combined diagnostic results were compared with clinical diagnostic results. The sensitivity and specificity of the combined diagnostic model for gastrointestinal cancer in the training set were 96% (95% CI: 93%-99%) and 100% (95% CI: 100%-100%), respectively (see Table 1), with an AUC of 1.000 (95% CI: 1.000-1.000) (see Table 1). Figure 2 The sensitivities for colorectal cancer and gastric cancer were 96% (95% CI: 91%-100%) and 97% (95% CI: 93%-100%), respectively (see Table 1), with AUCs of 1.000 (95% CI: 1.000-1.000) for both (see Table 1). Figure 2 ).

[0059] In the validation set, the combined diagnostic results were compared with clinical diagnostic results. The sensitivity and specificity of the combined diagnostic model for gastrointestinal cancer in the validation set were 91% (95% CI: 84%-99%) and 100% (95% CI: 100%-100%), respectively (see fourth aspect of the invention), and the AUC was 0.979 (95% CI: 0.955-1.000) (see...). Figure 3 The sensitivities for colorectal cancer and gastric cancer were 90% (95% CI: 79%-100%) and 93% (95% CI: 84%-100%), respectively (see Table 1), with AUCs of 0.988 (95% CI: 0.969-1.000) and 0.971 (95% CI: 0.929-1.000), respectively (see Table 1). Figure 3 ).

[0060] In the independent external validation set, the combined diagnostic results were compared with clinical diagnostic results, and the sensitivity and specificity of the combined diagnostic model for gastrointestinal cancer in the independent external validation set were determined to be 86% (95% CI: 82%-89%) and 93% (95% CI: 88%-98%), respectively (see Table 1), with an AUC of 0.943 (95% CI: 0.920-0.966) (see Table 1). Figure 4 The sensitivity for colorectal cancer and gastric cancer was 84% ​​(95% CI: 79%-88%) and 89% (95% CI: 84%-94%), respectively (see Table 1), with AUCs of 0.936 (95% CI: 0.909-0.962) and 0.954 (95% CI: 0.929-0.979), respectively (see Table 1). Figure 4 ).

[0061] The combined diagnostic model for gastrointestinal cancer showed a sensitivity of 82% (95% CI: 76%-88%) in 154 cases of stage 0-II gastrointestinal cancer on an independent external validation set (see Table 1), and an AUC of 0.930 (95% CI: 0.900-0.960) (see Table 1). Figure 4 Among them, the sensitivity for 101 cases of stage 0-II colorectal cancer and 53 cases of stage 0-II gastric cancer was 82% (95% CI: 75%-90%) and 81% (95% CI: 71%-92%), respectively (see Table 1), and the AUC was 0.925 (95% CI: 0.890-0.960) and 0.941 (95% CI: 0.904-0.977), respectively (see Table 1). Figure 4 ).

[0062] like Figure 4 As shown, the diagnostic efficacy of the present application's diagnostic model for gastrointestinal cancer was compared with that of traditional serum tumor markers. The AUC of the combined diagnostic model for gastrointestinal cancer was 0.938 (95% CI: 0.891-0.986), which was significantly better than that of traditional serum tumor markers (AUC ranged from the lowest CEA 0.461 (95% CI: 0.370-0.553) to the highest CA125 0.838 (95% CI: 0.776-0.900).

[0063] Example 4: Screening DNA methylation markers related to tissue tracing from patients with positive combined diagnoses of gastrointestinal cancer in public databases DNA methylation data (Illumina Infinium Human Methylation 450 BeadChip, GSE103186) from 392 colorectal cancer tissues, 104 adjacent colorectal tissues, 383 gastric cancer tissues, and 63 adjacent gastric tissues were downloaded from the public databases TCGA (The Cancer Genome Atlas) and GEO (Gene Expression Omnibus). Differential analysis was performed on 496 intestinal tissues and 446 gastric tissues using the R package ChAMP to screen for DNA methylation sites showing significant differences between intestinal and gastric tissues. p <0.05, |Δβ|≥0.2), and remove DNA methylation sites located on the X and Y chromosomes, finally obtaining 2100 hypermethylated sites in intestinal tissue and 5086 hypermethylated sites in gastric tissue. The union of these sites yielded 7186 DNA methylation sites related to tissue tracing in gastrointestinal cancer tissue.

[0064] Example 5: Tissue source tracing model for patients with positive combined diagnosis of gastrointestinal cancer A. Screening for DNA methylation regions in tissues of patients with positive combined diagnoses of gastrointestinal cancer from plasma samples in the training set. For 7186 tissue-related DNA methylation sites in gastrointestinal cancer tissues screened from public databases, DNA methylation sites were merged into regions in the training set according to the rule that adjacent CpG distances were less than 50 and Pearson correlation coefficients were greater than 0.5. A Wilcoxon test was used to analyze the differences between 67 colorectal cancer cases and 68 gastric cancer cases. p The criteria of <0.05 and |Δβ|≥0.01 were used to screen out 1381 significantly different DNA methylation regions, and then LASSO feature screening was performed to obtain 230 DNA methylation regions that were related to the tissue of gastrointestinal cancer positive patients (see the fourth aspect of the present invention).

[0065] B. Constructing a tissue source model for patients with positive combined diagnosis of gastrointestinal cancer using plasma samples from the training set. A logistic regression algorithm was used to model 230 DNA methylation regions using machine learning. After model selection, 10-fold cross-validation was used to determine the model hyperparameters. Then, the probability p of each sample being predicted as colorectal cancer and the probability 1-p of being predicted as gastric cancer were calculated according to the standard logistic regression formula. If the probability of being predicted as colorectal cancer is greater than the probability of being predicted as gastric cancer, the sample is classified as colorectal cancer; if the probability of being predicted as colorectal cancer is less than the probability of being predicted as gastric cancer, the sample is classified as gastric cancer.

[0066] The standard logistic regression formula is as follows: Formula (II); Where p is the combined diagnostic score; x is the methylation level of the i-th region; a is the coefficient of the i-th region; and b is the cutoff value, with the cutoff value for the tissue tracing model being -0.3443.

[0067] C. Validate the performance of the tissue tracing model for patients with positive combined diagnosis of gastrointestinal cancer using plasma samples. Using the tissue tracing model of patients with positive combined diagnosis of gastrointestinal cancer determined by the above training set, the standard logistic regression formula (II) was used to calculate the probability that 29 cases of colorectal cancer and 29 cases of gastric cancer in the validation set were predicted as colorectal cancer and gastric cancer, respectively. By comparing the probability magnitudes, the prediction results of colorectal cancer and gastric cancer were obtained.

[0068] D. Validating the performance of the tissue tracing model for patients with positive combined diagnosis of gastrointestinal cancer using independent external validation set plasma samples. Plasma samples from 225 colorectal cancer patients and 161 gastric cancer patients were collected according to inclusion and exclusion criteria. DNA methylation analysis was performed to create an independent external validation set. A tissue source tracing model for patients with a combined positive diagnosis of gastrointestinal cancer was used to calculate the probability of each sample in the independent external validation set being predicted as having colorectal or gastric cancer. By comparing the probability values, the prediction results for colorectal and gastric cancer were obtained. The predicted probability values ​​of the gastrointestinal cancer source tracing model are summarized below: Predicted probability values ​​for colorectal cancer samples in training set 1-67 (colorectal cancer p, gastric cancer (1-p)): 0.9976(0.0024)、1.0000(0.0000)、0.9987(0.0013)、0.9980(0.0020)、0.9997(0.0003)、0.9994(0.0006)、0.9983(0.0017)、0.9978(0.0022)、0.9970(0.0030)、0.9979(0.0021)、0.9994(0.0006)、0.9972(0.0028)、0.9964(0.0036)、0.9971(0.0029)、0.9963(0.0037)、0.9954(0.0046)、0.9967(0.0033)、0.9998(0.0002)、0.9998(0.0002)、0.9985(0.0015)、0.9989(0.0011)、1.0000(0.0000)、0.9999(0.0001)、0.9985(0.0015)、0.9978(0.0022)、0.9998(0.0002)、0.9982(0.0018)、0.9967(0.0033)、0.9991(0.0009)、1.0000(0.0000)、0.9956(0.0044)、0.9972(0.0028)、0.9977(0.0023)、0.9980(0.0020)、0.9996(0.0004)、0.9971(0.0029)、0.9976(0.0024)、0.9957(0.0043)、0.9931(0.0069)、0.9973(0.0027)、0.9968(0.0032)、0.9943(0.0057)、0.9979(0.0021)、0.9997(0.0003)、0.9990(0.0010)、0.9999(0.0001)、0.9975(0.0025)、0.9997(0.0003)、0.9997(0.0003)、0.9971(0.0029)、0.9998(0.0002)、0.9998(0.0002)、1.0000(0.0000)、0.9984(0.0016)、1.0000(0.0000)、0.9987(0.0013)、1.0000(0.0000)、1.0000(0.0000)、0.9995(0.0005)、0.9994(0.0006)、0.9992(0.0008)、0.9995(0.0005)、0.9970(0.0030)、0.9997(0.0003)、1.0000(0.0000)、1.0000(0.0000)、0.9991(0.0009).

[0069] Predicted probability values ​​for gastric cancer samples in training set 68-135 (colorectal cancer p, gastric cancer (1-p)): 0.0106(0.9894)、0.0042(0.9958)、0.0094(0.9906)、0.0176(0.9824)、0.0220(0.9780)、0.0266(0.9734)、0.0000(1.0000)、0.0277(0.9723)、0.0304(0.9696)、0.0384(0.9616)、0.0369(0.9631)、0.0560(0.9440)、0.0383(0.9617)、0.0060(0.9940)、0.0027(0.9973)、0.0135(0.9865)、0.0308(0.9692)、0.0281(0.9719)、0.0085(0.9915)、0.0181(0.9819)、0.0000(1.0000)、0.0064(0.9936)、0.0000(1.0000)、0.0519(0.9481)、0.0265(0.9735)、0.0098(0.9902)、0.0172(0.9828)、0.0122(0.9878)、0.0054(0.9946)、0.0064(0.9936)、0.0002(0.9998)、0.0083(0.9917)、0.0025(0.9975)、0.0214(0.9786)、0.0544(0.9456)、0.0215(0.9785)、0.0076(0.9924)、0.0560(0.9440)、0.0115(0.9885)、0.0003(0.9997)、0.0236(0.9764)、0.0383(0.9617)、0.0035(0.9965)、0.0453(0.9547)、0.0032(0.9968)、0.0179(0.9821)、0.0225(0.9775)、0.0266(0.9734)、0.0001(0.9999)、0.0002(0.9998)、0.0041(0.9959)、0.0277(0.9723)、0.0155(0.9845)、0.0000(1.0000)、0.0002(0.9998)、0.0196(0.9804)、0.0186(0.9814)、0.0016(0.9984)、0.0175(0.9825)、0.0031(0.9969)、0.0067(0.9933)、0.0738(0.9262)、0.0248(0.9752)、0.0025(0.9975)、0.0424(0.9576)、0.0265(0.9735)、0.0504(0.9496), 0.0339 (0.9661).

[0070] Predicted probability values ​​for colorectal cancer samples in validation sets 136-164 (colorectal cancer p, gastric cancer (1-p)): 0.5106 (0.4894), 0.9947 (0.0053), 0.8428 (0.1572), 0.6264 (0.3736), 0.9995 (0.0005), 0.9534 (0.0466), 0.9997 (0.0003), 1.0000 (0.0000), 0.8917 (0.1083), 0.9998 (0.0002), 0.9654 (0.0346), 0.9993 (0.0007), 0.9958 (0.0042), 0.9955 (0.0045) 0.6173 (0.3827), 0.9977 (0.0023), 0.9215 (0.0785), 0.8824 (0.1176), 0.7818 (0.2182), 0.5459 (0.4541), 0.6564 (0.3436), 0.9999 (0.0001), 1.0000 (0.0000), 0.9704 (0.0296), 0.9706 (0.0294), 0.9996 (0.0004), 0.9962 (0.0038), 1.0000 (0.0000). 0.8835 (0.1165).

[0071] Predicted probabilities of gastric cancer samples in validation set 165-193 (p for colorectal cancer, (1-p) for gastric cancer): 0.7974 (0.2026), 0.0544 (0.9456), 0.5961 (0.4039), 0.0005 (0.9995), 0.0180 (0.9820), 0.5205 (0.4795), 0.0076 (0.9924), 0.0040 (0.9960), 0.0192 (0.9808), 0.5637 (0.4363), 0.0001 (0.9999), 0.0074 (0.9926), 0.0002 (0.9998), 0.1015 (0.8985) 0.0002 (0.9998), 0.4155 (0.5845), 0.0419 (0.9581), 0.0597 (0.9403), 0.0051 (0.9949), 0.0009 (0.9991), 0.0003 (0.9997), 0.0034 (0.9966), 0.0059 (0.9941), 0.0440 (0.9560), 0.0021 (0.9979), 0.0000 (1.0000), 0.2554 (0.7446), 0.9451 (0.0549) 0.0001 (0.9999).

[0072] Predicted probabilities for colorectal cancer samples in independent external validation set 194-418 (colorectal cancer p, gastric cancer (1-p)): 0.8499(0.1501)、0.9302(0.0698)、0.9070(0.0930)、0.8791(0.1209)、0.4412(0.5588)、0.6874(0.3126)、0.9539(0.0461)、0.9984(0.0016)、0.9991(0.0009)、0.9536(0.0464)、0.9982(0.0018)、0.9975(0.0025)、0.9754(0.0246)、0.5494(0.4506)、0.3780(0.6220)、0.6198(0.3802)、0.9472(0.0528)、0.9927(0.0073)、0.8471(0.1529)、0.8730(0.1270)、0.0318(0.9682)、0.9837(0.0163)、0.7959(0.2041)、0.8992(0.1008)、0.9984(0.0016)、0.6055(0.3945)、0.9990(0.0010)、0.9789(0.0211)、0.9999(0.0001)、0.9855(0.0145)、0.8310(0.1690)、0.9589(0.0411)、0.9987(0.0013)、0.9985(0.0015)、0.9724(0.0276)、0.7577(0.2423)、0.9502(0.0498)、0.5360(0.4640)、0.9324(0.0676)、0.1797(0.8203)、0.1011(0.8989)、0.8146(0.1854)、0.9850(0.0150)、0.9268(0.0732)、0.9354(0.0646)、0.8465(0.1535)、0.5941(0.4059)、0.9884(0.0116)、0.9134(0.0866)、0.7705(0.2295)、0.2576(0.7424)、0.0191(0.9809)、0.6537(0.3463)、0.9995(0.0005)、0.5372(0.4628)、0.2914(0.7086)、0.2546(0.7454)、0.8123(0.1877)、0.9894(0.0106)、0.6207(0.3793)、0.9508(0.0492)、0.6608(0.3392)、0.1610(0.8390)、0.9964(0.0036)、0.9717(0.0283)、0.5483(0.4517)、0.7141(0.2859)、0.9205(0.0795)、0.5088(0.4912)、0.9921(0.0079)、0.5153(0.4847)、0.6646(0.3354)、0.5000(0.5000)、0.6366(0.3634)、0.9928(0.0072)、0.9983(0.0017)、0.6862(0.3138)、0.6638(0.3362)、0.6983(0.3017)、0.6988(0.3012)、0.5190(0.4810)、0.9954(0.0046)、0.9982(0.0018)、0.5606(0.4394)、0.8471(0.1529)、0.9248(0.0752)、0.6783(0.3217)、0.5413(0.4587)、0.9751(0.0249)、0.7719(0.2281)、0.8446(0.1554)、0.9528(0.0472)、0.5447(0.4553)、0.9965(0.0035)、0.9824(0.0176)、0.9966(0.0034)、0.7465(0.2535)、0.8540(0.1460)、0.1260(0.8740)、0.8873(0.1127)、0.7153(0.2847)、0.9538(0.0462)、0.9992(0.0008)、0.2035(0.7965)、0.6395(0.3605)、0.7955(0.2045)、0.9771(0.0229)、0.9767(0.0233)、0.9997(0.0003)、0.9789(0.0211)、0.9999(0.0001)、0.9663(0.0337)、0.9851(0.0149)、0.6629(0.3371)、0.9964(0.0036)、0.9787(0.0213)、0.9882(0.0118)、0.9323(0.0677)、0.8785(0.1215)、0.6588(0.3412)、0.7019(0.2981)、0.9717(0.0283)、0.0003(0.9997)、0.9977(0.0023)、0.0232(0.9768)、0.9779(0.0221)、0.5660(0.4340)、0.9041(0.0959)、0.9296(0.0704)、0.1578(0.8422)、0.6881(0.3119)、0.8313(0.1687)、0.5125(0.4875)、0.9812(0.0188)、0.5852(0.4148)、0.5036(0.4964)、0.0242(0.9758)、0.9763(0.0237)、0.9738(0.0262)、0.9653(0.0347)、0.9806(0.0194)、0.9819(0.0181)、0.7632(0.2368)、0.6915(0.3085)、0.9972(0.0028)、0.5716(0.4284)、0.5815(0.4185)、0.5004(0.4996)、0.1687(0.8313)、0.6773(0.3227)、0.7813(0.2187)、0.9775(0.0225)、1.0000(0.0000)、0.3228(0.6772)、0.5051(0.4949)、1.0000(0.0000)、0.6670(0.3330)、0.2137(0.7863)、0.6424(0.3576)、0.5147(0.4853)、0.6794(0.3206)、0.0036(0.9964)、0.9264(0.0736)、0.6262(0.3738)、0.5882(0.4118)、0.1820(0.8180)、0.9959(0.0041)、0.7714(0.2286)、0.0748(0.9252)、0.3952(0.6048)、0.5953(0.4047)、0.9949(0.0051)、0.0028(0.9972)、0.2644(0.7356)、0.6887(0.3113)、0.9778(0.0222)、1.0000(0.0000)、0.5288(0.4712)、0.6369(0.3631)、0.5039(0.4961)、0.6729(0.3271)、0.1608(0.8392)、0.2199(0.7801)、1.0000(0.0000)、1.0000(0.0000)、0.5238(0.4762)、0.5183(0.4817)、0.7770(0.2230)、0.9665(0.0335)、0.0131(0.9869)、0.0778(0.9222)、0.9734(0.0266)、0.6268(0.3732)、0.5133(0.4867)、0.5377(0.4623)、0.6067(0.3933)、0.6653(0.3347)、0.9999(0.0001)、0.6125(0.3875)、0.6839(0.3161), 0.4433(0.5567), 0.7337(0.2663), 0.2943(0.7057), 0.8633(0.1367), 0.9620(0.0380), 0.9267(0.0733), 0.6538(0.3462), 0.8106(0.1894), 0.0035(0.9965), 0.3260(0.6740), 0.7797(0.2203), 0.9952(0.004) 8), 0.5416 (0.4584), 0.8779 (0.1221), 0.0806 (0.9194), 0.5575 (0.4425), 0.7767 (0.2233), 1.0000 (0.0000), 0.9351 (0.0649), 0.1680 (0.8320), 0.0370 (0.9630), 0.5972 (0.4028), 0.9985 (0.0015), 0.0338 (0.9662). 0.2945 (0.7055).

[0073] Predicted probabilities of gastric cancer samples in the independent external validation set 419-579 (colorectal cancer p, gastric cancer (1-p)): 0.4690(0.5310)、0.0296(0.9704)、0.0011(0.9989)、0.0205(0.9795)、0.1919(0.8081)、0.0354(0.9646)、0.2991(0.7009)、0.5526(0.4474)、0.0080(0.9920)、0.6030(0.3970)、0.6479(0.3521)、0.0363(0.9637)、0.2805(0.7195)、0.0013(0.9987)、0.0046(0.9954)、0.2844(0.7156)、0.7966(0.2034)、0.0328(0.9672)、0.0072(0.9928)、0.5778(0.4222)、0.9866(0.0134)、0.0012(0.9988)、0.4415(0.5585)、0.5354(0.4646)、0.0011(0.9989)、0.0041(0.9959)、0.2392(0.7608)、0.0027(0.9973)、0.0461(0.9539)、0.0000(1.0000)、0.0030(0.9970)、0.9845(0.0155)、0.8024(0.1976)、0.0322(0.9678)、0.0026(0.9974)、0.3127(0.6873)、0.0062(0.9938)、0.2272(0.7728)、0.3419(0.6581)、0.3706(0.6294)、0.0000(1.0000)、0.5524(0.4476)、0.5971(0.4029)、0.0491(0.9509)、0.5312(0.4688)、0.4139(0.5861)、0.2522(0.7478)、0.6868(0.3132)、0.5225(0.4775)、0.0492(0.9508)、0.0001(0.9999)、0.4253(0.5747)、0.2921(0.7079)、0.6500(0.3500)、0.0000(1.0000)、0.0042(0.9958)、0.0000(1.0000)、0.2881(0.7119)、0.5616(0.4384)、0.0144(0.9856)、0.5936(0.4064)、0.0096(0.9904)、0.6196(0.3804)、0.7092(0.2908)、0.5749(0.4251)、0.0575(0.9425)、0.0001(0.9999)、0.2944(0.7056)、0.0000(1.0000)、0.5073(0.4927)、0.0013(0.9987)、0.0874(0.9126)、0.0929(0.9071)、0.5290(0.4710)、0.2708(0.7292)、0.5235(0.4765)、0.0001(0.9999)、0.0132(0.9868)、0.7674(0.2326)、0.0017(0.9983)、0.0037(0.9963)、0.0003(0.9997)、0.0937(0.9063)、0.8911(0.1089)、0.0185(0.9815)、0.0011(0.9989)、0.0450(0.9550)、0.9203(0.0797)、0.0002(0.9998)、0.6091(0.3909)、0.3900(0.6100)、0.5927(0.4073)、0.0372(0.9628)、0.5139(0.4861)、0.0004(0.9996)、0.4851(0.5149)、0.4149(0.5851)、0.6159(0.3841)、0.8906(0.1094)、0.0016(0.9984)、0.0065(0.9935)、0.2984(0.7016)、0.0952(0.9048)、0.0007(0.9993)、0.0597(0.9403)、0.0027(0.9973)、0.0576(0.9424)、0.0050(0.9950)、0.0068(0.9932)、0.0002(0.9998)、0.0113(0.9887)、0.0202(0.9798)、0.0318(0.9682)、0.1039(0.8961)、0.0371(0.9629)、0.4002(0.5998)、0.0449(0.9551)、0.0321(0.9679)、0.0021(0.9979)、0.0231(0.9769)、0.0395(0.9605)、0.0597(0.9403)、0.0083(0.9917)、0.3490(0.6510)、0.4870(0.5130)、0.2260(0.7740)、0.1787(0.8213)、0.1665(0.8335)、0.5020(0.4980)、0.1039(0.8961)、0.9837(0.0163)、0.3293(0.6707)、0.6010(0.3990)、0.7320 (0.2680), 0.8828 (0.1172), 0.0027 (0.9973), 0.0000 (1.0000), 0.0006 (0.9994), 0.0000 (1.0000), 0.6355 (0.3645), 0.5280 (0.4720), 0.0518 (0.9482), 0.0008 (0.9992), 0.7790 (0.2210), 0.1772 (0.8228), 0.5888 (0.4112), 0.1153 (0. 8847), 0.0147 (0.9853), 0.4493 (0.5507), 0.0022 (0.9978), 0.0047 (0.9953), 0.0039 (0.9961), 0.9902 (0.0098), 0.7482 (0.2518), 0.0000 (1.0000), 0.5337 (0.4663), 0.1900 (0.8100), 0.9738 (0.0262), 0.7657 (0.2343), 0.5838 (0.4162), . 0.0159 (0.9841).

[0074] E. Test Results In the training set, the predicted results were compared with clinical diagnoses, and the accuracy of predicting gastrointestinal cancer in the training set was determined to be 100% (95% CI: 100%–100%) (see Table 2), with an AUC of 1.000 (95% CI: 1.000–1.000) (see Table 2). Figure 6 The accuracy for colorectal cancer and gastric cancer was 100% (95% CI: 100%−100%) (see Table 2).

[0075] In the validation set, the predicted results were compared with clinical diagnostic results, and the accuracy of the tissue tracing model for patients with positive combined diagnoses of gastrointestinal cancer was determined to be 91% (95% CI: 84%–99%) (see Table 2); the AUC was 0.974 (95% CI: 0.941–1.000) (see Table 2). Figure 7 The accuracy rates for colorectal cancer and gastric cancer were 100% (95% CI: 100%–100%) and 83% (95% CI: 69%–97%), respectively (see Table 2).

[0076] The predicted results were compared with clinical diagnoses, and the accuracy of the prediction for gastrointestinal cancer on the independent external validation set was determined to be 78% (95% CI: 74%–82%) (see Table 2); the AUC was 0.846 (95% CI: 0.807–0.885) (see Table 2). Figure 8The accuracy rates for colorectal cancer and gastric cancer were 83% (95% CI: 78%–88%) and 71% (95% CI: 65%–78%), respectively (see Table 2).

[0077]

Claims

1. A combination of DNA methylation region biomarkers for the combined diagnosis of gastrointestinal cancer patients, wherein the DNA methylation regions are shown below (chromosome: start position - stop position (positive and negative strands), model coefficients; reference genome is hg19): chr1:101005348-101005457(+),-0.0005; chr1:111822043-111822068(+),-0.0257; chr1:115880340-115880444(+),0.0046; chr1:115880774-115880918(+),0.0750; chr1:1267541-1267655(+),-0.0309; chr1:146544255-146544336(+),-0.0031; chr1:156616751-156616858(+),0.0480; chr1:156616757-156616858(+),0.0629; chr1:179712359-179712461(+),-0.0581; chr1:200007570-200007623(+),-0.0551; chr1:210111614-210111717(+),0.0514; chr1:210861187-210861240(+),-0.0572; chr1:228196347-228196464(+),-0.0064; chr1:231297871-231298065(+),-0.0206; chr1:237205214-237205384(+),0.0325; chr1:2984735-2984923(+),0.0622; chr1:3567263-3567362(+),-0.0055; chr1:37500489-37500604(-),-0.0026; chr1:57889475-57889560(+),-0.0386; chr1:57890544-57890636(+),0.0617; chr1:58715450-58715630(+),-0.0345; chr1:91189140-91189226(+),0.0350; chr1:942439-942554(-),0.0201; chr1:969213-969306(+),0.0088; chr10:101292437-101292507(+),0.0167; chr10:102821760-102821863(+),-0.0416; chr10:104170638-104170718(+),-0.0270; chr10:104535792-104535854(+),0.0010; chr10:11206792-11206892(+),-0.0022; chr10:11298996-11299109(+),-0.0419; chr10:118897355-118897465(+),-0.0903; chr10:124907383-124907460(+),0.0735; chr10:125425608-125425787(+),0.0149; chr10:129534131-129534182(+),-0.0249; chr10:129534217-129534227(+),-0.0321; chr10:129535249-129535448(+),-0.0337; chr10:133110253-133110449(+),0.0314; chr10:133945888-133945989(-),0.1011; chr10:21799262-21799340(+),0.0236; chr10:2992148-2992213(+),-0.0370; chr10:42863495-42863594(+),0.0496; chr10:497316-497377(+),0.0162; chr10:50817603-50817691(-),0.0568; chr10:5735301-5735376(+),0.0782; chr10:60936417-60936494(+),0.0073; chr10:63213323-63213396(+),-0.0668; chr10:7453507-7453688(+),0.0813; chr10:8096985-8097087(+),0.0547; chr10:92616821-92616922(+),0.0690; chr10:94825771-94825874(+),0.0082; chr11:125036365-125036480(-),0.0245; chr11:128563614-128563740(+),0.0046; chr11:1364958-1365050(+),-0.0533; chr11:19463880-19463962(+),-0.0465; chr11:32450101-32450178(+),0.0946; chr11:89867679-89867799(+),0.0483; chr12:103351959-103352020(+),-0.0010; chr12:111472276-111472432(+),-0.0026; chr12:114838688-114838866(+),0.0585; chr12:114847088-114847247(+),-0.0350; chr12:31079601-31079694(+),0.0059; chr12:58014758-58014901(+),0.0513; chr12:75601803-75601863(+),0.0186; chr13:112723421-112723529(+),0.0073; chr13:112760028-112760137(+),0.0138; chr13:28503166-28503254(+),0.0074; chr13:37005452-37005551(+),0.0447; chr13:43148278-43148376(+),0.0348; chr13:50701592-50701695(+),0.0840; chr13:50706583-50706740(+),-0.0684; chr13:79181525-79181613(+),-0.0561; chr13:84452930-84453027(+),0.0023; chr13:95365416-95365509(+),0.0830; chr13:96204764-96204930(+),-0.0073; chr14:102247977-102248168(+),-0.0264; chr14:29235136-29235244(+),0.0944; chr14:52734431-52734619(+),0.0034; chr14:60973773-60973848(+),-0.0138; chr14:70346126-70346223(+),0.0001; chr14:77737530-77737638(-),0.0937; chr15:35047355-35047467(+),0.0041; chr15:55880900-55881023(+),-0.0182; chr15:60297636-60297747(+),0.0453; chr15:83316143-83316320(+),0.0000; chr15:86233163-86233265(+),-0.0609; chr16:215788-215904(+),0.0089; chr16:22825046-22825131(+),0.0252; chr16:22825046-22825195(+),-0.0342; chr16:23847259-23847369(+),0.0032; chr16:23847913-23848052(+),-0.0011; chr16:3355458-3355649(+),0.0788; chr16:54969087-54969202(+),0.0659; chr16:6533106-6533219(+),-0.0065; chr16:87441478-87441597(+),-0.0339; chr17:21281441-21281538(+),0.0498; chr17:26699109-26699216(+),-0.0015; chr17:32907337-32907485(-),-0.0313; chr17:37381380-37381565(+),0.0357; chr17:38347738-38347910(+),0.0353; chr17:43339416-43339594(+),-0.0083; chr17:57642721-57642782(+),0.0523; chr17:6616768-6616955(+),-0.0005; chr17:71161157-71161242(+),-0.0181; chr17:71161157-71161273(+),-0.0326; chr17:71161160-71161356(+),-0.0012; chr17:73696459-73696509(+),-0.0613; chr18:11752447-11752637(+),-0.0753; chr18:12911263-12911456(+),0.0608; chr18:43913655-43913782(+),-0.0006; chr18:49868176-49868270(+),-0.0208; chr18:70210374-70210483(+),0.0211; chr18:74962039-74962220(+),-0.0454; chr18:76739185-76739275(+),-0.0035; chr18:9707978-9708064(+),0.0009; chr19:12624368-12624466(+),-0.0192; chr19:18901666-18901751(+),0.0034; chr19:19322596-19322778(+),-0.0367; chr19:21657691-21657756(+),0.0158; chr19:30016073-30016224(+),-0.0565; chr19:30019604-30019741(+),0.0453; chr19:34113353-34113549(+),0.0989; chr19:34113992-34114145(+),0.0269; chr19:37407118-37407310(+),-0.0018; chr19:48947507-48947589(-),0.0025; chr19:54481368-54481469(+),0.0399; chr19:55864365-55864432(+),-0.0703; chr19:57683743-57683885(+),0.0322; chr19:58446745-58446832(+),-0.0466; chr19:59092612-59092711(+),-0.0218; chr19:59092612-59092713(+),-0.0090; chr2:105470463-105470559(-),0.0154; chr2:109746080-109746196(+),-0.0168; chr2:111876660-111876844(+),0.0460; chr2:154728978-154729150(+),0.0537; chr2:154728979-154729151(-),-0.0352; chr2:158300389-158300485(+),0.0740; chr2:164593182-164593290(+),-0.0037; chr2:175199771-175199881(+),0.0146; chr2:175208534-175208649(+),-0.0079; chr2:175208535-175208650(-),-0.0662; chr2:176936377-176936526(+),-0.0073; chr2:176987367-176987468(+),0.0074; chr2:177014849-177014966(+),0.0634; chr2:177014909-177014959(+),0.0031; chr2:177014962-177014962(+),0.0253; chr2:177014966-177014966(+),0.0555; chr2:182322168-182322349(+),-0.0038; chr2:182548728-182548820(+),-0.0419; chr2:186603317-186603436(+),0.1254; chr2:187713531-187713615(+),0.1319; chr2:198650887-198651076(+),0.0012; chr2:200327284-200327391(-),0.0985; chr2:200333935-200334085(+),-0.0332; chr2:219736167-219736343(+),0.0441; chr2:220313414-220313521(+),0.0846; chr2:45155175-45155274(+),-0.0242; chr2:45161274-45161361(+),0.0084; chr2:45161485-45161598(+),0.0327; chr2:63284536-63284574(+),-0.0486; chr2:71115928-71116067(+),-0.0167; chr2:71134586-71134728(+),-0.0812; chr2:74726809-74726894(+),-0.0376; chr2:79823717-79823775(+),-0.0541; chr2:80531590-80531701(+),0.0036; chr2:98963526-98963585(+),0.0474; chr20:21694778-21694882(+),0.0749; chr20:25065319-25065512(+),0.0158; chr20:34894558-34894699(+),0.0056; chr20:37434060-37434246(+),-0.0126; chr20:39316972-39317131(+),0.1057; chr20:41818269-41818356(+),0.0067; chr20:41818270-41818357(-),0.0049; chr20:41818358-41818358(+),0.0035; chr20:43439365-43439545(+),-0.0003; chr20:44657849-44658033(+),0.0180; chr20:54580583-54580678(-),0.0496; chr20:58180518-58180676(+),0.0550; chr20:59047467-59047504(+),0.0217; chr20:61885162-61885362(+),0.0015; chr20:61885236-61885382(+),0.0050; chr21:32253729-32253791(+),-0.0373; chr21:36042323-36042420(+),0.0028; chr21:38378539-38378654(+),-0.0601; chr22:17082492-17082591(+),-0.0205; chr22:48885347-48885527(+),0.0378; chr3:124860685-124860774(-),0.0013; chr3:125076278-125076419(+),-0.0096; chr3:128211444-128211625(+),0.0775; chr3:129694156-129694255(+),0.0668; chr3:147077593-147077636(+),-0.0196; chr3:147077671-147077671(+),-0.0154; chr3:147106536-147106615(+),0.0549; chr3:147136879-147136974(+),0.0604; chr3:14852659-14852829(+),-0.0013; chr3:187387552-187387740(+),0.0286; chr3:192126735-192126914(+),0.0024; chr3:22413862-22414048(+),-0.0044; chr3:36422016-36422160(-),-0.0413; chr3:68981828-68981912(+),0.0866; chr4:110223999-110224179(+),-0.0096; chr4:113444246-113444347(+),0.0253; chr4:134070291-134070441(+),0.0359; chr4:154710353-154710429(+),-0.0458; chr4:156680311-156680489(+),-0.0018; chr4:165878038-165878140(-),0.0266; chr4:174452401-174452520(+),0.0134; chr4:184826879-184827046(+),0.0136; chr4:185940824-185940933(+),-0.0642; chr4:37246791-37246892(+),-0.0401; chr4:4864738-4864833(+),0.0034; chr4:4866439-4866510(+),-0.0261; chr4:55991752-55991943(+),-0.0084; chr4:56685918-56686028(+),-0.0379; chr4:5710278-5710372(+),0.0743; chr4:6009978-6010164(+),0.0296; chr4:779476-779644(+),-0.0065; chr4:93226349-93226479(+),-0.0310; chr4:93227164-93227276(+),-0.0023; chr4:93227173-93227298(+),-0.0337; chr5:113698463-113698564(+),0.0461; chr5:134363516-134363637(+),-0.0597; chr5:136834419-136834526(+),0.0312; chr5:140180964-140181120(+),0.0518; chr5:140235578-140235586(+),0.0452; chr5:140235596-140235680(+),0.0245; chr5:140501277-140501412(+),0.0316; chr5:140616432-140616495(+),-0.0251; chr5:140619567-140619586(+),0.0827; chr5:140750132-140750260(+),0.0581; chr5:140778363-140778456(+),0.0072; chr5:140793394-140793474(-),0.0622; chr5:140794921-140795036(+),-0.0029; chr5:140810051-140810161(+),0.0399; chr5:140810337-140810519(+),-0.0171; chr5:140810707-140810902(+),-0.0809; chr5:140811003-140811189(+),0.0946; chr5:140811253-140811314(+),0.0270; chr5:150400298-150400395(+),-0.0084; chr5:1594239-1594343(+),0.0350; chr5:178017824-178017937(+),0.0147; chr5:178772285-178772385(+),0.0026; chr5:1876140-1876312(-),-0.0488; chr5:2756101-2756209(+),0.0126; chr5:36693315-36693389(+),-0.0020; chr5:36693316-36693390(-),0.0174; chr5:37838271-37838462(+),0.0248; chr5:38258351-38258441(+),0.0084; chr5:38258451-38258451(+),-0.0465; chr5:63257038-63257131(-),-0.0238; chr5:83679842-83679992(+),0.0011; chr5:87974388-87974464(+),-0.0387; chr6:105388635-105388731(+),0.0318; chr6:105388636-105388732(-),0.0736; chr6:105389544-105389599(+),0.0242; chr6:106429545-106429610(+),-0.0016; chr6:12750205-12750312(+),0.0096; chr6:133561886-133561993(+),-0.0456; chr6:154360648-154360763(+),-0.0110; chr6:1594362-1594466(+),-0.0703; chr6:166074730-166074837(+),0.0025; chr6:166259960-166260013(-),-0.0466; chr6:25652351-25652383(+),0.1015; chr6:25652390-25652467(+),0.0660; chr6:28602881-28603037(+),-0.0625; chr6:28956719-28956804(+),0.0136; chr6:29521507-29521696(-),-0.0297; chr6:29760705-29760805(+),0.0002; chr6:32064053-32064246(+),-0.0481; chr6:32064054-32064240(-),0.0105; chr6:32064161-32064345(+),0.0506; chr6:392463-392652(+),-0.0070; chr6:62996627-62996702(+),-0.0302; chr6:72596076-72596176(+),0.0161; chr6:84418339-84418529(+),0.0042; chr6:84418625-84418820(+),-0.0007; chr6:84562836-84562986(+),-0.0589; chr6:84563330-84563485(+),0.0015; chr7:101006223-101006312(+),-0.0464; chr7:12151615-12151694(+),0.0224; chr7:134143408-134143588(+),0.0011; chr7:145813009-145813107(-),-0.0392; chr7:153445143-153445227(-),0.0259; chr7:153584609-153584662(+),0.0669; chr7:154861985-154862073(+),0.0509; chr7:155255303-155255415(+),-0.0271; chr7:155302286-155302439(+),-0.0313; chr7:157405932-157406128(+),0.0848; chr7:158362870-158362983(+),0.0693; chr7:19157613-19157777(+),-0.0057; chr7:19813204-19813300(-),-0.0097; chr7:43153143-43153311(+),-0.0032; chr7:4832112-4832271(+),-0.0140; chr7:63361049-63361178(+),0.0779; chr7:63924688-63924770(+),0.0665; chr7:79082017-79082131(+),0.0014; chr7:88389247-88389342(+),0.0269; chr7:97361201-97361201(+),-0.0571; chr7:97361241-97361294(+),0.0661; chr7:97361748-97361814(+),0.0305; chr8:128306933-128306986(+),-0.0048; chr8:145107102-145107282(+),0.0525; chr8:17271006-17271119(+),-0.0017; chr8:38326278-38326373(+),0.0463; chr8:53477783-53477975(+),-0.0552; chr8:53852599-53852677(+),0.0075; chr8:54790449-54790617(-),0.0768; chr8:58906997-58907185(+),-0.0024; chr8:72469457-72469561(-),0.0707; chr8:85095995-85096056(+),0.0355; chr8:93114861-93115008(+),-0.0552; chr9:95571917-95572015(+),0.0539.

2. The biomarker combination as described in claim 1, wherein the combined diagnosis of gastrointestinal cancer patients is performed using formula (I), which is as follows: Equation (I); in, p is the combined diagnostic score; x is the methylation level of the i-th region; a is the coefficient of the i-th region; b is the cutoff value, and the cutoff value of the combined diagnostic model is -0.3235; the DNA methylation regions of the methylation level are as described in claim 1.

3. This invention provides the application of DNA methylation region markers in constructing a model for the combined diagnosis of gastrointestinal cancer patients; the DNA methylation region is as described in claim 1; the model for the combined diagnosis of gastrointestinal cancer patients is constructed using a logistic regression algorithm; the model for the combined diagnosis of gastrointestinal cancer patients uses formula (I) for combined diagnosis, and when the combined diagnosis score is ≥0.7045, the patient is determined to be positive for gastrointestinal cancer; formula (I) is as follows: Equation (I); in, p is the combined diagnostic score; x is the methylation level of the i-th region; a is the coefficient of the i-th region; b is the cutoff value, and the cutoff value of the combined diagnostic model is -0.3235.

4. A combined diagnostic model for gastrointestinal cancer, wherein the combined diagnostic model uses formula (Ⅰ) for combined diagnosis, the formula being as follows: Equation (I); in, p is the combined diagnostic score; x is the methylation level of the i-th region; a is the coefficient of the i-th region; b is the cutoff value, and the cutoff value of the combined diagnostic model is -0.3235; the DNA methylation regions of the methylation level are as described in claim 1.

5. In the combined diagnostic model for gastrointestinal cancer as described in claim 4, when the combined diagnostic score is ≥0.7045, the patient is determined to be positive for gastrointestinal cancer.

6. A combination of DNA methylation region markers for tissue tracing in patients with positive combined diagnostic results for gastrointestinal cancer, wherein the DNA methylation regions are shown below (chromosome: start position - stop position (positive and negative strands), model coefficients; reference genome is hg19): chr10:102821615-102821760(+),0.0972; chr10:102821760-102821863(+),0.5378; chr10:110084660-110084660(+),-0.0101; chr10:11059485-11059577(+),0.1803; chr10:11206756-11206870(+),-0.0023; chr10:125751892-125751983(+),-0.0964; chr10:126135176-126135176(+),-0.2675; chr10:128839223-128839268(+),-0.4072; chr10:134407859-134407942(+),-0.4237; chr10:134936768-134936952(+),-0.3069; chr10:1444541-1444644(+),-0.0402; chr10:18429261-18429357(+),-0.0033; chr10:3848384-3848384(+),-0.1028; chr10:42863495-42863594(+),0.2987; chr10:84719878-84719878(+),-0.4264; chr10:90343087-90343266(+),-0.4462; chr10:92616821-92616922(+),0.1977; chr11:116781288-116781303(+),-0.4244; chr11:1577982-1578096(+),0.1354; chr11:32450101-32450178(+),0.1031; chr11:64140993-64141100(+),-0.0874; chr11:65352249-65352361(+),0.0724; chr11:65408468-65408566(+),-0.4074; chr11:93586725-93586779(+),0.6223; chr11:94965294-94965452(+),0.5301; chr12:108168987-108169087(+),-0.4854; chr12:117470875-117471008(+),-0.5256; chr12:20521953-20521984(+),-0.4218; chr12:3947996-3948103(+),-0.5159; chr12:42682155-42682248(+),-0.1198; chr12:52626831-52626996(+),0.4033; chr12:52695568-52695659(+),0.0038; chr12:54867371-54867454(+),0.0710; chr12:64062485-64062588(+),0.0667; chr13:105792252-105792399(+),0.0329; chr13:112630580-112630695(+),0.0495; chr13:113229295-113229334(+),-0.0620; chr13:114261808-114261945(+),-0.0305; chr13:114814086-114814269(+),-0.1133; chr13:24807829-24807902(+),0.2099; chr13:46742691-46742802(+),0.4641; chr13:46742722-46742802(+),0.2958; chr13:79168546-79168613(+),0.4630; chr13:96204486-96204538(+),0.2446; chr13:114814644-114814725(-),-0.2457; chr14:36988118-36988316(+),-0.0634; chr14:60981173-60981254(+),0.2314; chr14:65068414-65068504(+),-0.0675; chr14:73929570-73929597(+),-0.4206; chr14:94211818-94211818(+),-0.0164; chr15:21995905-21996010(+),-0.1613; chr15:31115806-31115883(+),-0.0319; chr15:41695378-41695434(+),-0.3231; chr15:57592036-57592109(+),0.3200; chr15:73371746-73371777(+),-0.0744; chr15:78556880-78556988(+),-0.0560; chr15:99409411-99409548(+),-0.4970; chr15:99644973-99645065(+),-0.1252; chr15:99645031-99645189(+),-0.4031; chr16:1032704-1032813(+),-0.1430; chr16:1143467-1143583(+),-0.0745; chr16:16463448-16463550(+),-0.2147; chr16:32214126-32214243(+),0.4874; chr16:49902279-49902383(+),0.0509; chr16:53407722-53407808(+),-0.2238; chr16:5486224-5486268(+),0.1094; chr16:67686881-67687000(+),-0.3527; chr16:7703876-7703947(+),-0.1115; chr16:88844377-88844511(+),0.1408; chr17:1686671-1686791(+),-0.3267; chr17:1839990-1840090(+),0.1172; chr17:1961238-1961346(+),0.0748; chr17:40664817-40664940(+),0.3777; chr17:56736698-56736814(+),0.0153; chr17:57642721-57642782(+),-0.0543; chr17:77721583-77721680(+),0.2778; chr17:77970135-77970193(+),-0.4630; chr17:79058765-79058953(+),-0.3541; chr17:81020155-81020268(+),0.0347; chr17:47301643-47301839(-),-0.4527; chr17:56327070-56327219(-),0.0085; chr18:19756935-19757022(+),0.0614; chr18:35145983-35146142(+),0.0000; chr19:14276879-14276921(+),-0.3621; chr19:1468376-1468466(+),0.2639; chr19:1524352-1524449(+),0.2912; chr19:17409380-17409380(+),0.1858; chr19:36800795-36800878(+),0.5242; chr19:37329795-37329956(+),-0.0151; chr19:38713144-38713341(+),0.1636; chr19:48206028-48206119(+),-0.0566; chr19:52514445-52514445(+),0.1829; chr19:55864365-55864432(+),-0.1679; chr19:56510897-56511059(+),0.1288; chr19:58629780-58629871(+),-0.0435; chr19:58952150-58952275(+),0.3525; chr19:681413-681532(+),-0.5265; chr19:852990-853077(+),-0.3836; chr1:1052600-1052664(+),-0.1112; chr1:1109580-1109676(+),0.7246; chr1:121260880-121260987(+),0.1424; chr1:147806141-147806231(+),-0.2979; chr1:149399899-149400002(+),0.3912; chr1:155220137-155220318(+),-0.0027; chr1:16085371-16085466(+),0.0021; chr1:19600378-19600484(+),-0.3721; chr1:200211351-200211412(+),-0.2202; chr1:202091865-202091933(+),-0.5375; chr1:2058881-2058997(+),-0.3355; chr1:214328927-214328927(+),-0.4523; chr1:231297600-231297627(+),0.2970; chr1:235805308-235805500(+),-0.4010; chr1:25257500-25257599(+),-0.0378; chr1:34630844-34630999(+),-0.1203; chr1:906428-906518(+),-0.4635; chr1:91182726-91182821(+),-0.1616; chr1:95179390-95179461(+),-0.0831; chr1:969767-969922(+),-0.0072; chr1:223936750-223936921(-),0.1101; chr20:34249256-34249284(+),-0.7203; chr20:35448345-35448426(+),0.5571; chr20:37355218-37355288(+),0.6217; chr20:45179345-45179413(+),0.0418; chr20:54824550-54824646(+),-0.0512; chr20:60540388-60540388(+),-0.1573; chr20:60540469-60540486(+),-0.1645; chr20:61148853-61148952(+),-0.0134; chr20:44657778-44657886(-),0.8005; chr21:42799066-42799191(+),0.0569; chr21:46074556-46074651(+),-0.2504; chr22:29076076-29076237(+),0.0786; chr22:38610728-38610840(+),-0.3446; chr22:51169920-51170018(+),-0.0022; chr2:128432961-128433113(+),-0.7507; chr2:16805059-16805111(+),0.0637; chr2:176994996-176995102(+),0.1854; chr2:228670471-228670606(+),-0.3971; chr2:228670481-228670606(+),-0.3342; chr2:231855440-231855620(+),-0.0807; chr2:233323868-233323957(+),0.0235; chr2:23749087-23749151(+),-0.1099; chr2:241719559-241719678(+),-0.1085; chr2:39319447-39319447(+),-0.3423; chr2:43054655-43054735(+),0.0558; chr2:47382366-47382557(+),0.3247; chr2:63283937-63284038(+),-0.1813; chr2:87036908-87037000(+),0.1165; chr2:9549245-9549336(+),0.2988; chr3:11537591-11537626(+),0.5794; chr3:142666439-142666543(+),-0.2328; chr3:149388151-149388180(+),-0.4188; chr3:155394292-155394303(+),0.2918; chr3:181441513-181441623(+),-0.5377; chr3:181444485-181444580(+),-0.0363; chr3:196705855-196705970(+),0.2446; chr3:37940037-37940044(+),0.4209; chr3:61550540-61550687(+),0.5871; chr3:75445459-75445600(+),-0.4330; chr3:99357581-99357626(+),0.3264; chr3:129407531-129407549(-),-0.3681; chr3:142666440-142666544(-),-0.0854; chr4:1004247-1004289(+),-0.3553; chr4:100738066-100738222(+),-0.4564; chr4:101438778-101438836(+),-0.2542; chr4:183935046-183935104(+),0.1450; chr4:87515380-87515579(+),-0.1843; chr5:107167398-107167498(+),-0.0739; chr5:1123034-1123123(+),-0.1479; chr5:115152851-115152938(+),0.0867; chr5:121647923-121648117(+),0.0036; chr5:124034239-124034288(+),0.0601; chr5:140214100-140214179(+),0.0537; chr5:140502891-140502903(+),-0.0061; chr5:140502918-140502975(+),0.2235; chr5:141242687-141242742(+),-0.3330; chr5:157098465-157098557(+),-0.2737; chr5:1594501-1594638(+),-0.2058; chr5:35919491-35919491(+),-0.1063; chr5:37837377-37837555(+),0.4285; chr5:40681794-40681990(+),-0.0070; chr6:105388624-105388731(+),-0.1501; chr6:117586483-117586593(+),-0.4364; chr6:143586006-143586006(+),-0.3659; chr6:158399108-158399203(+),-0.4167; chr6:166232960-166233106(+),-0.4302; chr6:167524238-167524296(+),-0.6199; chr6:29593382-29593490(+),-0.4392; chr6:29704545-29704545(+),-0.4907; chr6:30227967-30228063(+),-0.0516; chr6:31857007-31857100(+),0.0874; chr6:32009327-32009422(+),-0.1232; chr6:44773667-44773754(+),0.0538; chr6:7847437-7847496(+),-0.5400; chr6:25652352-25652460(-),-0.2905; chr6:32064054-32064247(-),-0.5971; chr7:1311498-1311575(+),-0.3327; chr7:1337106-1337204(+),0.0329; chr7:155283738-155283817(+),-0.1038; chr7:157406032-157406186(+),-0.1405; chr7:157691177-157691208(+),-0.7094; chr7:158352173-158352211(+),-0.0723; chr7:1604448-1604524(+),0.0305; chr7:19157650-19157777(+),-0.0188; chr7:27204639-27204732(+),-0.1162; chr7:4287212-4287276(+),0.2124; chr7:45002418-45002582(+),-0.2852; chr7:45002651-45002810(+),-0.1964; chr7:601257-601446(+),0.4147; chr7:906726-906799(+),0.2407; chr7:100807411-100807599(-),0.3871; chr7:1112980-1113108(-),-0.0833; chr7:158531641-158531695(-),-0.1322; chr8:103540766-103540879(+),-0.2519; chr8:10587935-10588071(+),0.1174; chr8:11561628-11561758(+),-0.0326; chr8:120058164-120058222(+),0.4292; chr8:144359234-144359334(+),-0.2928; chr8:145555844-145555974(+),-0.1827; chr8:18744378-18744513(+),-0.1777; chr8:1992498-1992606(+),0.2455; chr8:2075696-2075841(+),0.8527; chr8:2263237-2263427(+),-0.3316; chr8:26307416-26307504(+),0.0289; chr8:58906986-58907140(+),0.0618; chr8:58906997-58907185(+),0.0102; chr8:67344571-67344763(+),-0.0113; chr8:71135804-71135895(+),-0.1917; chr8:975247-975385(+),0.3308; chr9:139716115-139716224(+),-0.1570; chr9:140311820-140312018(+),-0.6809.

7. The biomarker combination as described in claim 6, wherein tissue tracing of the patient with a positive combined diagnosis of gastrointestinal cancer is performed using formula (II), which is as follows: Formula (II); in, p is the probability value predicted as colorectal cancer; x is the methylation level of the i-th region; a is the coefficient of the i-th region; b is the cutoff value, and the cutoff value of the tissue tracing model for patients with positive combined diagnosis of gastrointestinal cancer is -0.3443; the probability value predicted as gastric cancer in the tissue tracing model for patients with positive combined diagnosis of gastrointestinal cancer is 1-p; the DNA methylation region of the methylation level is as described in claim 6.

8. Application of DNA methylation region marker combination in constructing a model for tissue tracing of patients with positive combined diagnosis of gastrointestinal cancer; wherein the DNA methylation region is as described in claim 6; the model for tissue tracing of patients with positive combined diagnosis of gastrointestinal cancer is constructed using a logistic regression algorithm; the tissue tracing of patients with positive combined diagnosis of gastrointestinal cancer uses formula (II) for tissue tracing, wherein formula (II) is as follows: Formula (II); in, p is the probability value predicted as colorectal cancer; x is the methylation level of the i-th region; a is the coefficient of the i-th region; b is the cutoff value, and the cutoff value of the tissue tracing model for patients with positive combined diagnosis of gastrointestinal cancer is -0.3443; the probability value predicted as gastric cancer by the tissue tracing model for patients with positive combined diagnosis of gastrointestinal cancer is 1-p.

9. A tissue tracing model for patients with a positive combined diagnosis of gastrointestinal cancer, wherein the tissue tracing for patients with a positive combined diagnosis of gastrointestinal cancer uses formula (II) for tissue tracing, and formula (II) is as follows: Formula (II); in, p is the probability value predicted as colorectal cancer; x is the methylation level of the i-th region; a is the coefficient of the i-th region; b is the cutoff value, and the cutoff value of the tissue tracing model for patients with positive combined diagnosis of gastrointestinal cancer is -0.3443; the probability value predicted as gastric cancer by the tissue tracing model for patients with positive combined diagnosis of gastrointestinal cancer is 1-p; the DNA methylation region of the methylation level is as described in claim 6.

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