Targeted valine-induced polypeptide, polypeptide therapeutic agent and application of polypeptide therapeutic agent

Abstract

The invention relates to a polypeptide targeted to valine induction, a polypeptide therapeutic agent and application thereof, the polypeptide targeted to a valine induction section is designed based on an SE14 structural domain of valine binding protein HDAC6, the amino acid sequence of the SE14 structural domain is as shown in SEQ ID NO.1, and the amino acid sequence of the polypeptide is as shown in any one of SEQ ID NO.2-SEQ ID NO.8; according to the present invention, the polypeptide is taken into the cell by using the cell-penetrating peptide, the polypeptide is combined with the valine to release the protein HDAC6 combined with the valine, and the HDAC6 not combined with the valine enters the cell nucleus to achieve the tumor inhibition effect, such that the tumor progress is inhibited by formulating the polypeptide specifically targeting the valine induction, and the tumor inhibition effect is provided; the compound has important research significance and application value in preparation of medicines for preventing and / or treating tumors.

Description

Technical Field

[0001] The present invention relates to the field of biomedicine, in particular to the field of polypeptide drug technology, and specifically to a polypeptide targeting valine sensing, a polypeptide therapeutic agent and applications thereof. Background Art

[0002] Peptides are widely used in tumor treatment. They inhibit the occurrence and development of tumors through various mechanisms. The following is the current application status and research progress of some peptides in tumor treatment.

[0003] Tumor-targeting peptides: Peptides can be used as tumor-targeting carriers to achieve precise positioning of tumor cells through specific peptide sequences. For example, a peptide containing the arginine-glycine-aspartic acid sequence (RGD) can target the integrin αvβ3 receptor, which is a receptor highly expressed on the surface of various tumors and in neovascular endothelial cells.

[0004] Stimulus-responsive peptide materials: These peptides can achieve precise drug release under specific stimulation in the tumor microenvironment, such as enzyme stimulation, pH change or redox stimulation. For example, matrix metalloproteinase (MMPs) responsive peptides can use highly expressed MMPs in the tumor microenvironment to trigger drug release.

[0005] Enzyme-responsive peptides: Specific peptide sequences can be hydrolyzed by specific proteases, which provides the possibility of constructing enzyme-responsive peptide carriers. For example, MMPs-responsive peptides can be used to construct MMPs-responsive peptide diagnostic and therapeutic systems.

[0006] pH-responsive peptides: Taking advantage of the slightly acidic environment of tumor tissue, we design a pH-responsive drug delivery system. These peptides carry a negative charge under physiological conditions, which prevents them from being internalized by normal cells. However, in the tumor microenvironment, the charge changes, which promotes the internalization of tumor cells.

[0007] Redox-responsive peptides: Taking advantage of the fact that the concentration of glutathione (GSH) in tumor cells is higher than that in normal cells, redox-responsive drug delivery systems are designed. These peptides release drugs in the reducing environment inside the cell.

[0008] Peptide anti-tumor drugs: Peptide drugs show unique advantages in tumor treatment, such as inducing tumor cell apoptosis, activating anti-tumor immune response, inducing tumor cell necrosis and inhibiting tumor angiogenesis. For example, Microcolin H is a marine peptide molecule that exerts anti-tumor activity by acting on phosphatidylinositol transporter α / β (PITPα / β).

[0009] Peptide vaccines: Peptide vaccines activate or enhance the body's own anti-tumor immunity by expressing specific tumor antigens. For example, 3D189 (galinpepimut-S, GPS) is a peptide vaccine targeting WT1 protein and has entered a phase III global multicenter clinical trial for patients with acute myeloid leukemia (AML).

[0010] These research advances indicate that peptides have great potential for application in tumor treatment. In the future, more peptide drugs may be developed to provide more treatment options for cancer patients.

[0011] However, there are no peptide drugs targeting amino acid sensing to date, but there are new strategies for tumor treatment, namely peptides targeting protein-protein interactions and molecular degraders targeting amino acid sensing.

[0012] In terms of peptide development targeting protein interactions, existing studies have identified STRN3 as an essential regulatory subunit of protein phosphatase 2A (PP2A) that recruits MST1 / 2 and promotes its dephosphorylation, leading to YAP activation. The study also found that upregulation of STRN3 in gastric cancer is associated with YAP activation and poor prognosis. Based on this mechanistic understanding and with the help of structure-guided medicinal chemistry, the study developed a highly selective peptide inhibitor, STRN3-derived Hippo-activating peptide or SHAP, which can disrupt the STRN3-PP2Aa interaction and reactivate the Hippo tumor suppressor, inhibit YAP activation, and have anti-tumor effects in vivo.

[0013] In terms of targeted amino acid sensing anti-tumor strategies, existing studies have found that arginine, as a second messenger molecule, binds to RBM39 and controls the expression of metabolic genes, mediating upregulation of asparagine synthesis, leading to enhanced arginine uptake, creating a positive feedback loop to maintain high arginine levels and carcinogenic metabolism, and ultimately promoting the occurrence of liver tumors. Treatment with the molecular glue degrader indisulam can block the metabolic reprogramming of RBM39 that promotes the development of liver cancer, suggesting that RBM39 is a therapeutic target for liver cancer.

[0014] With the in-depth research in the field of amino acid sensing, amino acid sensing plays an important role in the occurrence and development of tumors. At present, there is a molecular glue degrader indisulam targeting the arginine sensing protein RBM39, which can inhibit the development of liver cancer. However, as a molecular glue degrader, indisulam will degrade the entire RBM39 protein, which will affect other functions of RBM39, not just the function of targeting arginine sensing, so it will lead to low specificity of targeted sensing. So far, there is still no peptide drug targeting amino acid sensing. Summary of the invention

[0015] The purpose of the present invention is to provide a polypeptide targeting valine sensing, a polypeptide therapeutic agent and its application to address at least one of the deficiencies in the prior art, so as to solve the problems existing in the related art such as low specificity of targeted sensing and the lack of polypeptide drugs targeting amino acid sensing.

[0016] To achieve the above object, the technical solution adopted by the present invention is:

[0017] The first aspect of the present invention is to provide a polypeptide targeting valine sensing, wherein the polypeptide is designed based on the SE14 domain of the valine binding protein HDAC6, wherein the amino acid sequence of the SE14 domain is shown in SEQ ID NO.1.

[0018] Further, SEQ ID NO.1:

[0019] LTQDQPSEAATGGATLAQTISEAAIGGAMLGQTTSEEAVGGATPDQTTSEETVGGAILDQTT SEDAVGGATLGQTTSEEAVGGATLAQTTSEAAMEGATLDQTTSEEAPGGT

[0020] Furthermore, the polypeptide comprises an amino acid sequence as shown in any one of SEQ ID NO.2 to SEQ ID NO.8.

[0021] Further, SEQ ID NO. 2: TLAQTISEAAIGGA;

[0022] SEQ ID NO.3: MLGQTTSEEAVGGA;

[0023] SEQ ID NO.4: TPDQTTSETVGGA;

[0024] SEQ ID NO.5: ILDQTTSEDAVGGA;

[0025] SEQ ID NO.6: TLGQTTSEEAVGGA;

[0026] SEQ ID NO.7: TLAQTTSEAAMEGA;

[0027] SEQ ID NO.8: TLDQTTSEEAPGGT.

[0028] Furthermore, the amino acid sequence of the polypeptide is shown in SEQ ID NO.5.

[0029] Furthermore, the polypeptide is connected to a cell-penetrating peptide, and the sequence of the cell-penetrating peptide is shown in SEQ ID NO.9.

[0030] Further, SEQ ID NO.9: YGRKKRRQRRRA.

[0031] Furthermore, the method for preparing the polypeptide comprises the following steps:

[0032] S1. Construct a domain truncation of the valine-binding protein HDAC6, and determine the binding segment that binds to valine by in vitro and in vivo pull-down experiments combined with biotin-modified valine;

[0033] S2. obtaining the binding constant between valine and the binding segment by a warm titration calorimetry experiment;

[0034] S3. By using a molecular docking method, the binding force between valine and the binding segment is simulated, and the sequences are classified according to the sequence and the binding force, and the polypeptides are synthesized;

[0035] S4. Design a cell-penetrating peptide in front of the polypeptide to enable the polypeptide to enter the cell.

[0036] Furthermore, the binding segment that binds to valine is the SE14 domain of HDAC6.

[0037] The second aspect of the present invention is to provide a polypeptide therapeutic agent targeting valine sensing, wherein the polypeptide therapeutic agent comprises any polypeptide as described in the first aspect.

[0038] Furthermore, the polypeptide therapeutic agent also includes a valine restricted diet; wherein the valine diet is used to limit the intake of valine, and the valine intake is 0.4% to 8% of the total food intake.

[0039] Furthermore, in the polypeptide therapeutic agent, the polypeptide further comprises a cell-penetrating peptide, and the sequence of the cell-penetrating peptide is shown in SEQ ID NO.9.

[0040] Furthermore, in the valine restricted diet, the mass percentage of the valine intake to the total food intake is preferably 0.41%.

[0041] In a specific embodiment, when the subject is a mouse, in the valine-restricted diet, the valine intake is 0.41% of the total food intake (consumed in the form of admixture with feed), and the intake of the polypeptide with cell-penetrating peptide is 10 mg / kg (once a day). It is understood that when it is used for other animals or humans, its dosage can be adaptively adjusted based on safety and efficacy.

[0042] Furthermore, the cell-penetrating peptide is preferably SEQ ID NO.9, and the polypeptide sequence is preferably SEQ ID NO.5, that is, the polypeptide sequence with the cell-penetrating peptide is YGRKKRRQRRRA-ILDQTTSEDAVGGA.

[0043] Furthermore, in the therapeutic agent, the polypeptide competitively binds to valine in the cell, thereby inhibiting the binding of valine to its sensor protein HDAC6, so that HDAC6 plays the role of a drug that inhibits tumor growth.

[0044] The third aspect of the present invention is to provide an application of a polypeptide as described in any one of the first aspect or a polypeptide therapeutic agent as described in any one of the second aspect, wherein the application is selected from at least one of the following applications: application in the preparation of a preparation that competitively binds to valine, application in the preparation of a drug for preventing and / or treating tumors.

[0045] Furthermore, the drugs include drugs that inhibit the occurrence and development of tumors.

[0046] Furthermore, the tumor includes colorectal cancer.

[0047] The present invention adopts the above technical solution, and has the following technical effects compared with the prior art:

[0048] The present invention analyzes the specific mechanism of action of valine sensing to obtain the specific segment binding to valine; designs the valine binding segment and the cell-penetrating peptide so that the polypeptide targeting the valine reaction can enter the cell; the targeted valine sensing polypeptide entering the cell can bind to the excess valine in the cell, thereby inhibiting the binding of valine to its sensing protein HDAC6, causing HDAC6 to play a role in inhibiting tumors, thereby providing a new strategy for tumor treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are only used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0050] Figure 1 is a schematic diagram of a domain truncation of the valine binding protein HDAC6 in one embodiment of the present invention;

[0051] Figure 2 This is a diagram showing the experimental results of pull-down of different domain truncations and biotin-modified valine in one embodiment of the present invention;

[0052] Figure 3 This is a result diagram of a pull-down experiment of SE14 protein and biotin-modified valine in one embodiment of the present invention;

[0053] Figure 4 is a result diagram of the binding constant between the SE14 domain and valine in an isothermal titration calorimetry experiment in one embodiment of the present invention;

[0054] Figure 5 is a schematic diagram of the amino acid sequences of seven polypeptides designed based on the SE14 domain of HDAC6 in one embodiment of the present invention;

[0055] Figure 6 This is a graph showing the electrochemical experimental results of three polypeptides, SE14-1, SE14-2, and SE14-4, with valine in one embodiment of the present invention;

[0056] Figure 7 This is a diagram showing the design results of three polypeptides, SE14-1, SE14-2 and SE14-4, connected to a transmembrane peptide (TAT) in one embodiment of the present invention;

[0057] Figure 8 This is a result diagram of a pulldown experiment of biotinylated valine as endogenous and polypeptide TAT-SE14-4 in one embodiment of the present invention;

[0058] Fig. 9 This is a diagram showing the results of a tumor sphere formation experiment of a colorectal cancer cell line HCT116 administered with polypeptide TAT-SE14-4 in one embodiment of the present invention;

[0059] Fig.10 This is a result diagram of the efficacy of the polypeptide TAT-SE14-4 targeting valine sensing and its combination with valine restricted diet in the treatment of colorectal cancer in one embodiment of the present invention. DETAILED DESCRIPTION

[0060] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without creative work belong to the scope of protection of the present invention. The experimental methods without specific conditions in the following embodiments are usually measured according to national standards. The experimental materials without the source indicated in the following embodiments are all commercially available raw materials. The equipment used in each step in the following embodiments is conventional equipment. If there is no corresponding national standard, it is carried out according to the general international standards, conventional conditions, or according to the conditions recommended by the manufacturer. Unless otherwise specified, all parts are weight parts and all percentages are mass percentages. Unless otherwise defined or specified, all professional and scientific terms used in the present invention have the same meaning as those familiar to those skilled in the art. In addition, any method and material similar or equal to the recorded content can be applied to the method of the present invention.

[0061] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention is further described below in conjunction with the drawings and specific embodiments, but is not intended to be a limitation of the present invention.

[0062] Those without special marking of manufacturers in the embodiments of the present invention can be obtained through conventional commercial purchase.

[0063] The present invention is described below by way of example.

[0064] Example 1 - Identification of the SE14 domain that binds to the critical region of valine

[0065] This embodiment is a preferred embodiment for obtaining and identifying the key region for binding valine.

[0066] This example determines the key region for binding to valine through truncation pull-down experiments, isothermal titration calorimetry experiments, molecular docking simulation experiments, and electrochemical experiments. The specific steps are as follows:

[0067] (1) Construct different domain truncations of the valine-binding protein HDAC6.

[0068] (2) In vitro and in vivo pull-down experiments with biotin-modified valine were performed to determine the region that can bind to valine. The binding constant of valine to the binding domain was further obtained through thermometric titration calorimetry experiments.

[0069] (3) The binding force between valine and the binding segment was simulated by molecular docking, and the sequences were classified and synthesized according to the sequence and binding force.

[0070] (4) The three segments of the synthesized polypeptide were subjected to electrochemical experiments with valine. The binding conditions of valine and the polypeptide were obtained by analyzing the linear scanning voltammogram.

[0071] like Figure 1 As shown, different domain truncations of the valine-binding protein HDAC6 include NLS structure, NES1 structure, DAC1 structure, DAC2 structure, SE14 structure, NES2 structure, and HUB structure.

[0072] like Figure 2 As shown, through experiments with different domain truncations of the protein and biotin-modified valine pull-down, it was found that the SE14 domain of HDAC6 can specifically bind to valine. The SE14 domain is selected from the 905-1016 segment of the valine-binding protein HDAC6, wherein the amino acid sequence of the SE14 domain is shown in SEQ ID NO.1 below:

[0073] LTQDQPSEAATGGATLAQTISEAAIGGAMLGQTTSEEAVGGATPDQTTSEETVGGAILDQT TSEDAVGGATLGQTTSEEAVGGATLAQTTSEAAMEGATLDQTTSEEAPGGT

[0074] In this example, the purified SE14 protein was subjected to a pull-down experiment with biotin-modified valine, and it was found that the SE14 domain could bind to valine. The results are as follows: Figure 3 shown.

[0075] like Figure 4 As shown, the binding of SE14 domain to valine and the binding constants of the two were further determined by isothermal titration calorimetry experiments.

[0076] In this example, sequence analysis revealed that the SE14 domain of HDAC6 is composed of seven tetradecapeptide repeats containing serine (Ser) and glutamic acid (Glu), such as Figure 5 As shown; 7 polypeptides were synthesized according to the sequences and binding forces, and their amino acid sequences and names are shown in Table 1 below; and the binding energies of the 7 polypeptides with valine were analyzed in turn by molecular docking, and the results are shown in Table 2.

[0077] Table 1 Amino acid sequences and names of seven polypeptides

[0078] Serial number name Amino acid sequence SEQ ID NO.2 SE14-1 TLAQTISEAAIGGA SEQ ID NO.3 SE14-2 MLGQTTSEEAVGGA SEQ ID NO.4 SE14-3 TPDQTTSEETVGGA SEQ ID NO.5 SE14-4 ILDQTTSEDAVGGA SEQ ID NO.6 SE14-5 TLGQTTSEEAVGGA SEQ ID NO.7 SE14-6 TLAQTTSEAAMEGA SEQ ID NO.8 SE14-7 TLDQTTSEEAPGGT

[0079] Table 2 Binding energy of heptapeptide and valine

[0080] SE14 peptide Binding Energy SE14-1 11.2449 SE14-2 18.1358 SE14-3 11.1818 SE14-4 12.4612 SE14-5 12.5137 SE14-6 13.1622 SE14-7 14.2261

[0081] Based on the above results, the conserved binding energy of the sequences was comprehensively analyzed, and three peptides (SE14-1, SE14-2, and SE14-4) were selected for electrochemical experiments with valine. The results are as follows: Figure 6 As shown. Figure 6 It can be seen that peptide SE14-4 has the strongest binding ability with valine.

[0082] In summary, the SE14 domain of HDAC6 can bind to valine, and the SE14-4 polypeptide has the strongest binding ability.

[0083] Example 2 - Preparation and verification of valine-binding polypeptides

[0084] This example is a method for preparing a better valine-targeted sensing polypeptide SE14.

[0085] In this example, based on the binding ability of the valine-binding polypeptides in Example 1, the three polypeptides SE14-1, SE14-2 and SE14-4 were selected, and the competitive pull-down experiment confirmed that the SE14-4 polypeptide had the strongest ability to bind to valine. The specific steps are as follows:

[0086] (1) Design a cell-penetrating peptide before the Control and SE14 peptides, such as Figure 7 As shown, the polypeptide can enter the cell. The sequence of the cell-penetrating peptide is SEQ ID NO.9: YGRKKRRQRRRA. The polypeptide was synthesized by Jier Biochemical Co., Ltd.

[0087] (2) Treat cells with different TAT-SE14 peptides (TAT-SE14-1, TAT-SE14-2 and TAT-SE14-4) 6 hours in advance, and perform endogenous pull-down experiments using biotinylated valine. The obtained samples were subjected to a protein blotting experiment, specifically, the obtained protein samples were added to the loading buffer, the samples were loaded into the SDS-PAGE gel, the separated proteins were transferred from the gel to the nitrocellulose membrane, the membrane was blocked with a blocking solution (5% skim milk), the membrane was incubated with a specific primary antibody of the target protein overnight, and then incubated with a secondary antibody labeled with horseradish peroxidase for 1 hour, and the target protein was visualized by chemiluminescence. The results are shown in FIG. Figure 8 As shown, by analyzing the binding strength between valine and HDAC6 protein, it was found that the peptide TAT-SE14-4 had the strongest ability to competitively block the binding of valine to HDAC6.

[0088] From the above test results, it can be seen that the polypeptide TAT-SE14-4 can play a role in competitively binding to valine in cells.

[0089] Example 3 - Application of peptides targeting valine sensing in tumor treatment

[0090] In this example, the valine-sensing targeting polypeptide TAT-SE14-4 with better binding ability obtained in Example 2 was used for experiments.

[0091] This example uses a colorectal cancer cell line HCT116 (purchased from the Chinese Academy of Sciences cell bank) tumor sphere formation experiment and a HCT116 cell nude mouse subcutaneous tumor model to verify the therapeutic effect of TAT-SE14-4 polypeptide at the cellular level and animal level. The specific steps are as follows:

[0092] (1) HCT116 cells were digested and counted, and then 200 cells / well were inoculated into a 96-well plate for culturing tumor spheres. Ten replicate wells were made for each group, and different volumes (0 μL, 1 μL, 5 μL, 10 μL, 50 μL) of TAT-SE14-4 polypeptide were added to make the final concentrations (0 μmol, 1 μmol, 5 μmol, 10 μmol, 50 μmol), respectively. The concentration of valine in the experimental groups (Control group and polypeptide treatment group) was 0.8 mM, and the valine restriction group (0 mM) was used as a positive control. After 7-14 days, the number of tumor spheres was counted according to the growth of the tumor spheres. The results are as follows. Fig. 9 As shown, by analyzing the morphology of tumor spheres and the number of spheres, it was found that the sphere-forming ability of HCT116 cells weakened with the increase of polypeptide concentration.

[0093] (2) Construction of subcutaneous tumor transplantation model in nude mice (purchased from Shanghai Slake Experimental Animal Co., Ltd.): 5-week-old nude mice were used in this experiment, and 5×10 6 HCT116 colorectal cancer cells (purchased from the Chinese Academy of Sciences Cell Bank) were used when the tumor volume reached 50 mm 3 (length × width × width × 1 / 2), the mice were randomly divided into groups.

[0094] The mice were randomly divided into Fig.10 The different treatment groups described in: 0.82% valine, 0.82% valine + TAT-SE14-4, 0.41% valine and 0.41% valine + TAT-SE14-4. The above percentage of valine is the mass percentage of valine intake to the total feed intake, and the treatment method of different concentrations of valine is to customize different concentrations of valine in the feed to limit the valine intake of mice. The mice were fed with customized feed until the end of the experiment. The amount of polypeptide used was 10 mg of polypeptide injected intraperitoneally per Kg of mouse, and the treatment frequency was daily administration. Tumor volume and mouse weight were measured once a week until the end.

[0095] Depend on Fig.10 It can be seen that after statistically analyzing the growth curve and tumor weight, it was found that the 0.82% valine + TAT-SE14-4 treatment group could significantly inhibit the occurrence and development of colorectal cancer compared with the 0.82% valine control group, and the 0.41% valine + TAT-SE14-4 group had the best colorectal cancer inhibition effect.

[0096] In summary, the present invention designs a polypeptide by targeting the valine sensing segment, and uses the cell-penetrating peptide TAT to bring the polypeptide into the cell. The polypeptide releases the protein HDAC6 bound to valine by binding to valine; HDAC6 not bound to valine enters the cell nucleus and exerts a tumor-suppressing effect. The advantage is that by formulating a polypeptide specifically targeting valine sensing, the progression of the tumor is inhibited. It has important research significance and application value in the preparation of preparations that competitively bind to valine and in the preparation of drugs for preventing and / or treating tumors, especially in the prevention and treatment of colorectal cancer.

[0097] The above description is only a preferred embodiment of the present invention, and does not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A polypeptide targeting valine sensing, characterized in that The polypeptide is designed based on the SE14 domain of the valine-binding protein HDAC6, wherein the amino acid sequence of the SE14 domain is shown in SEQ ID NO.

1.

2. The polypeptide according to claim 1, characterized in that The polypeptide comprises an amino acid sequence as shown in any one of SEQ ID NO.2 to SEQ ID NO.

8.

3. The polypeptide according to claim 2, characterized in that The amino acid sequence of the polypeptide is shown in SEQ ID NO.

5.

4. The polypeptide according to claim 2, characterized in that The polypeptide is connected to a cell-penetrating peptide, and the sequence of the cell-penetrating peptide is shown in SEQ ID NO.

9.

5. The polypeptide according to claim 1, characterized in that The preparation method of the polypeptide comprises the following steps: S1. Construct a domain truncation of the valine-binding protein HDAC6, and determine the binding segment that binds to valine by in vitro and in vivo pull-down experiments combined with biotin-modified valine; S2. obtaining the binding constant between valine and the binding segment by a warm titration calorimetry experiment; S3. By using a molecular docking method, the binding force between valine and the binding segment is simulated, and the sequences are classified according to the sequence and the binding force, and the polypeptides are synthesized; S4. Design a cell-penetrating peptide in front of the polypeptide to enable the polypeptide to enter the cell.

6. A polypeptide therapeutic agent targeting valine induction, characterized in that: The polypeptide therapeutic agent comprises the polypeptide according to any one of claims 1 to 5.

7. The polypeptide therapeutic agent according to claim 6, characterized in that: The polypeptide therapeutic agent also includes a valine restricted diet; wherein the valine diet is used to restrict the intake of valine, and the valine intake is 0.4% to 8% of the total food intake.

8. A use of the polypeptide according to any one of claims 1 to 5 or the polypeptide therapeutic agent according to any one of claims 6 to 7, characterized in that: The application is selected from at least one of the following applications: application in preparing a preparation for competitively binding valine, and application in preparing a drug for preventing and / or treating tumors.

9. The use according to claim 8, characterized in that: The drugs include drugs that inhibit the occurrence and development of tumors.

10. The use according to claim 8, characterized in that: The tumors include colorectal cancer.

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