Influence of Organ Environment on the Growth, Selection, and Metastasis of Human Colon Carcinoma Cells in Nude Mice

The purpose of these studies was to determine whether the biological and metastatic behaviors of tumor cells isolated from fresh surgical specimens of human colon carcinomas are influenced by the isolation method and the organ site of implantation and growth in nude mice. Three surgical specimens were obtained from three different patients. Two tumors were primary human colorectal carcinomas (HCC) classified as Dukes9 B2 (KM12) and Dukes9 D stages (KM20), and the third was from a liver metastasis (KM23). The tumors were enzymatically dissociated, and viable cells were implanted into the subcutis or spleen of different nude mice or were established in culture. Tumors developed in both sites of implantation, but hepatic metastases were found only in those nude mice that received splenic implantations of HCC cells. Cells from Dukes9 D stage tumors produced more hepatic disease than cells from the Dukes9 B tumor. Cells of the parental KM12C (culture) were injected into the spleen or cecum of nude mice to produce experimental and spontaneous hepatic metastases, respectively. HCC lesions were harvested from livers of nude mice and established as individual cell lines in culture. This procedure yielded cell lines KM12SM (spontaneous metastasis) and KM12L1 (experimental metastasis). The selection cycle for cells implanted into the spleen was repeated three more times to produce the cell line designated KM12L4. Cells of the parental KM12C and the three selected variants were injected into nude mice by different routes: i.v., s.c. into the cecum, and into the spleen. Subsequent to implantation into the spleen, all cell lines were shown to be tumorigenic. Cells from the selected KM12L4 and KM12SM lines produced a significantly higher number of experimental liver metastases than the parental cells. Moreover, subsequent to the injection into the cecum, cells of the once-selected KM12SM (for spontaneous metastasis) produced a higher incidence of spontaneous liver metastasis than all other lines. The human origin of all the lines was confirmed by isoenzyme and karyotype analyses. The two highly metastatic lines (KM12L4 and KM12SM) were tetraploid and produced elevated levels of type IV collagenolytic activity. Collectively, the results demonstrate that the orthotopic implantation of HCC cells into the appropriate organ environment can be used for efficient isolation and for study of metastatic subpopulations of cells from human colon carcinoma.