Characterization of metastatic clones derived from a metastatic variant of mouse colon adenocarcinoma 26.

A spontaneously metastatic variant (P-26-select) was selected from the murine colon adenocarcinoma 26 after repeated (26 times) cyclic in vivo passage of tumor cells from the lungs of mice bearing s.c. tumors. Clones were established from the cultured P-26-select cell line. These clones, the parent [P-no-select (culture cell line of colon 26 without in vivo selection)] and the metastatic variant (P-26-select) were then studied using three different assays to determine their metastatic potential. These assays included experimental metastasis, spontaneous metastasis from a nonresected s.c. growing tumor, and spontaneous metastasis following the resection of a primary footpad tumor. In general, there was an agreement among the results of these three assays of metastases, i.e., if a variant was spontaneously metastatic, it was also metastatic in the other assays of metastases. However, some experimentally metastatic clones did not necessarily show a high spontaneous metastatic potential to the lung. These results might indicate that the metastatic variant (P-26-select) is populated by spontaneously metastatic clones and also by clones which possess a propensity to metastasize experimentally. The morphology and growth properties of the clones were compared also.