Orthotopic transplantation model of human gastrointestinal cancer and detection of micrometastases

AIM To establish a relevant animal model of human gastrointestinal cancer, which can be used for repetitive investigations, so as to improve our under standing and management of carcinogenesis and cancer metastasis. METHODS Intact tissues of human colorectal and pancreatic cancers were tran splanted in nude mice. The biological characteristics of the original and t he corresponding transplanted tumors were investigated by HE staining, PAS staining and immunostaining. The metastases in the livers and lungs of nude mice were investigated by immunostaining with biotinylated mab KL-1 and by RT-PCR using CK20 specific primers. RESULTS There were totally 9 of 16 surgical specimens growing in nude mice subcutaneously and/or orthotopically (4 of 6 colorectal and 5 of 10 pancrea tic cancer). Tumor cell content of the specimens and freezing of tissue spe cimens are important factors influencing the growth of transplanted tumor. In the group of fresh tumor tissues with greater than 50% tumor cell conten t, the success rate of the transplantation was 100% (3 cases of pancreatic cancer and 3 cases of colorectal cancer). The orthotopically transplanted t umors resemble the original tumor morphologically and biologically, includi ng TAA expression such as CEA by immunohistochemistry, and CEA level in the serum of mice. Ki-67 labeling index and the expression of TAA especially K -ras, 17-1A and RA-96, are associated with the potential of tumor growth in nude mice. Micrometastases in the lungs and livers of tumor bearing mice c an be detected by immunostaining with biotinylated mab KL-1 and CK20-specif ic RT-PCR. CONCLUSION An orthotopic transplantation model for human colon and pancreat ic cancer in nude mice has been set up. We have also established sensitive detection methods with CK-immunohistochemistry and CK20-RT-PCR to study xen otransplanted human cancer and its metastatic cancer cells in the liver and lung of nude mice. This study may be helpful in understanding the mechanis m of cancer metastasis and in developing new diagnostic methods and therape utic strategies for metastases including micrometastases.