Phenotypic changes of Ab hamster melanoma during long-term culture

Cells of the Ab hamster amelanotic melanoma in primary cell culture have previously been shown to melanize rapidly, detach from the glass substratum and lose the ability to proliferate in vitro. Recent work demonstrates that when the Ab cells are subcultured prior to a complete loss of proliferative ability, the above processes occur in the 1-3 passages. In about half of our attempts, long-term cultures of Ab cells could be established from the few cells which remained attached to the glass during one of these first passages and resumed proliferation after a several-week period. The established long-term cultures showed a very low degree of melanization. Tumors which ensued from a reimplantation into hamsters of cells from one established long-term culture differed markedly from the original Ab melanoma in their phenotypic properties.