BIOLOGY OF HUMAN COLON-CANCER METASTASIS

The process of metastasis is highly selective and favors the survival and growth of a few subpopulations of cells that preexist within a het erogeneous primary neoplasm. To produce metastases, tumor cells must s ucceed in invasion, embolization, survival in the circulation, arrest in a distant capillary bed, and extravasation into and multiplication in organ parenchyma. The outcome of this process depends on the intera ction of metastatic cells with multiple host factors. To assess metast atic potential accurately, it is necessary to orthotopically implant h uman tumor cells recovered from surgical specimens into nude mice. Thi s orthotopic implantation of tumor cells is invariably associated with trauma to the specific organ of implantation, which is followed by th e processes of inflammation and repair. Tissue-specific growth factors may be responsible for stimulation of tumor cells that possess specif ic surface receptors. Understanding the factors that regulate cancer m etastasis should allow for the design of rational therapy.