Tumorigenicity associated with loss of differentiation and of response to insulin in the adipogenic cell line 1246.

The adipogenic cell line 1246, which grows and differentiates in defined medium, stringently requires insulin for both processes. From this cell line, insulin-independent variants were isolated and characterized. Unlike 1246 cells, the variant cell lines proliferate without insulin, have lost their differentiation ability, produce factor(s) able to replace insulin to stimulate 1246 cell growth but not differentiation and are tumorigenic. Because of these properties, this system is appropriate to examine the correlation (if any) between the loss of response to an extra-cellular factor and of ability to differentiate, and between the production of endogenous growth factor and the acquisition of tumorigenic properties.