Early resection of primary orthotopically-growing human colon tumor in nude mouse prevents liver metastasis: further evidence for patient-like hematogenous metastatic route.

We have developed an orthotopic transplant model of human cancer to immunodeficient mice utilizing microsurgical techniques with intact tissue. The resulting transplanted human tumors grow locally and metastasize in a clinical-like pattern. However, there has been no definitive evidence in colon cancer that the human tumors metastasize via hematogenous route in nude mice. In the present study, in order to obtain definitive evidence of physiological spread of the human tumors, the primary tumors were resected 10 days after the initial orthotopic transplantation to the nude mice. The resection prevented metastases from forming, demonstrating that metastases of the human colon cancers occur after 10 days and by physiological and non-seeding mechanisms in the transplanted nude mice.