Properties of cell lines derived from altered‐cell foci in baby mouse skin cultures

Abstract

Long-term cell lines were readily developed from a proportion of either baby mouse skin (BMS) cultures passing through colchicine-induced crisis or altered-cell foci selected from BMS cultures exposed to light and/or oxygen followed by colchicine. The developing cell lines behaved as though they passed through a continuing, profound genetic reshuffling process, which was usually lethal but which in some cases eventually yielded a gene set that favored long-term survival. Some cell lines have passed 120 cell doublings, and none has shown a second crisis or signs of senescence. As soon after isolation as measurement was possible (19-50 days) the cell lines were predominantly or entirely tetraploid or subtetraploid. Although BMS cells and all of the cell lines were density inhibited, the BMS, C14, C21 and C23 cells overgrew (formed colonies on) monolayers of the same cells in most combinations. The cell lines retained a variety of neoplastic morphological characters, although their morphology was more normal than in the original focus. No cell line, however, showed anchorage-independent growth or formed tumors in syngeneic hosts. The cell lines may all, therefore, be regarded as preneoplastic.

Enhancement of altered‐cell foci in baby mouse skin cultures by antitubulin treatment: Nuclear mechanisms

“…The background cells became fully attached and spread within 1-2 hours of removing drugs and replacing fresh, warm medium-lacking drugs, and the cultures were fully confluent again after a further 3-10 days (2-3 cell doublings). In this sense the drugs' effects were fully reversible and the cells appeared normal, but the cultures as a whole were not normal because the cell pattern was detectably more criss-cross than controls, and if subcul-tured once or twice before the development of foci, those cultures that had received colchicine entered a severe crisis that very few cells survived (Cooper et al, 1982b). Without passage but with weekly medium changes all cultures remained in good condition for at least 4-8 weeks.…”

“…Such induction seems also to depend on preexisting DNA damage, since both light and antitubulin treatment are essential for maximum numbers of altered-cell foci. It should be noted, however, that the altered-cell foci are not tumorigenic (Cooper et al, 1982b) and are therefore preneoplastic rather than fully transformed. …”

“…The chromosome numbers of the cell lines isolated from altered cell foci were mainly subtetraploid (Cooper et al, 1982b). I t therefore seemed feasible that chromosome loss had occurred after DNA doubling and nondisjunctional mitosis.…”

“…The previous section has shown that polyploid cells have appeared in large numbers within a few days of removal of antitubulin drugs, and that many or most of these cells continue to cycle in the polyploid mode. The chromosome numbers of the cell lines isolated from altered cell foci were mainly subtetraploid (Cooper et al, 1982b). I t therefore seemed feasible that chromosome loss had occurred after DNA doubling and nondisjunctional mitosis.…”