Correlation between the in vitro interaction of tumor cells with an organ environment and metastatic behavior in vivo.

The purpose of this study was to determine whether the in vitro interaction of tumor cells with an organ fragment correlated with organ colonization in vivo. Several clones of the K-1735 melanoma that exhibit different potentials for lung colonization or the heterogeneous M-5076 reticulum cell sarcoma which preferentially colonizes the liver, were used. The simultaneous subcutaneous implantation of a lung fragment with high lung-colonizing K-1735 cells stimulated the production of tumors, but this was not the case with the M-5076 cells, which do not colonize the lungs after intravenous injection. The ability of the tumor cells to survive in vitro in a lung fragment correlated with their capacity to produce lung tumor colonies after intravenous injection. Moreover, lung-conditioned medium stimulated the growth of lung-colonizing K-1735-M2 cells but not liver-colonizing M-5076 cells. Collectively, the data suggest that tissue-mediated growth stimulation may be one of the factors influencing the metastatic pattern and potential of tumor cells.