The invention relates to colon targeting recombinant
toxin as well as a preparation method and application thereof, and belongs to the colon targeting recombinant
toxin prepared by using
genetic engineering. The colon targeting recombinant
toxin has an
amino acid sequence as shown in SEQID No.2, pET28a is used as an
expression vector, and BL21(DE3) is used as an expression host, so that a BL21(DE3)(pET28a-rCCK96-104PE38KDEL) recombinant
engineering bacterial strain is constructed; and 6-poly-L-
histidine labels are carried, so that purification is facilitated. A Ni-NTA
metal-chelating affinity column is used, and a specificity
cutting method for rTEV enzymes is combined, so that only through two-step purification, rCCK96-104PE38KDEL recombination
protein being high in activity, high in purity and free from redundant sequences can be obtained, and the purity is 95% or above;
in vitro cell experiment, purified rCCK96-104PE38KDEL
recombinant immunotoxin can specifically kill colon
cancer cells with high expression, can restrain proliferation and
diffusion of
cancer cells, and does not have any damaging effect on normal cells and other non-CCK2R high-expression
tumor cells; and therefore, the rCCK96-104PE38KDEL conforms to conditions as
tumor targeting drugs, and a new direction is provided for treatment of the colon cancers.