[Selection for affinity to lung tissue in cell populations of experimental neoplasms]

Cell populations of eight experimental tumors (murine and rat rhabdomyosarcomas induced with 20-methylcholantrene, transplantable murine rhabdomyosarcoma A-7, and transplantable rat lymphosarcoma) have been selected for the affinity of their cells to lung tissue. The level of the affinity was measured as the number of lung nodules per 100 000 tumor cells injected intravenously. A 3-4-fold selection appeared to be non-effective, whereas 10-fold or more prolonged selections resulted in a gradual enhancement of the affinity of tumor cells to lung tissue. Thus, the transplantable murine and rat rhabdomyosarcomas were obtained with an increased capacity of their cells of yielding lung nodules. The affinity of rat rhabdomyosarcoma was 200-300 times higher after 40 steps of selection compared to the initial tumor affinity. With the rhabdomyosarcoma of CC57W mice, the affinity increased by 5 times after 20 steps of selection. Using our technique of selection (without an in vitro cultivation), the capacity of cells of persisting in lung tissue and yielding lung nodules looks likely as a quantitative character with a rather low heritability. It has been concluded that in cell populations of tumors examined there are only a few genetic population variations in cell capacity of making non-random metastases.