Double minutes in a cell line from mouse fibroblasts grown under nonselective conditions. Suppression of a double minute‐free sideline by in vivo environment

摘要

Normal lung fibroblasts of the mouse, started in serial in vivo culture in January 1983, underwent transformation in June into a vigorously growing cell line that had a hypertriploid stemline and a hypertetraploid sideline. The stemline had new markers, some with additional C-bands, and double minutes (DM): the sideline had few markers and no DM. By the end of 1983, the stemline gradually lost all DM and acquired one long homogeneously staining region (HSR). A tumorigenicity test in August 1983 gave rise to a tumor that was subsequently carried in serial culture and studied in frequent fixations. The sojourn in the animal host had induced lasting effects on the chromosomes. The most conspicuous effect was total loss of sideline cells and consequent presence of DM in practically all cells. Three problems were taken up for discussion: (1) The unexpected formation of DM in a cell line of normal origin and without known selective pressure; (2) the elimination of all DM-less cells from the tumor, suggesting correlation between DM and tumor formation; and (3) the possibly stimulative action on cell viability of markers with extra C-bands, expressed in their tendency to accumulate in cell clones and stemlines.