Microscopic metastasis of a human lung carcinoma cell line in athymic nude mice: isolation of a metastatic variant.

A human lung carcinoma cell line, UCP3, was carried as subcutaneous xenotransplants in athymic mice. Autopsies of these animals showed rare foci of microscopically visible metastases to any of the other organs. A metastatic variant, 522, was established serendipitously in vitro as a continuous cell line by blind isolation of the pulmonary metastatic foci, at the time of autopsy, from the lungs of the animals that carried subcutaneous xenotransplants of the parental cell line. The parental UCP3 and the metastatic variant 522 were examined by karyotypic and isoenzyme analysis and shown to be human and related. The metastatic variant, 522, metastasizes spontaneously from subcutaneous sites (like the parental UCP3). However, it forms larger subcutaneous xenotransplants and forms more metastatic foci in the lungs of the animals than does the parental cell line. Comparisons of the cell surface glycolipids show many similarities and a few differences. This model system may now be used for further investigations into the processes of metastasis of this human neoplasm.