Comparative effect of embryonic mouse fibroblasts (Balb/c-3T3) on the proliferation of hormone-dependent (T-47D) and hormone-independent (MDA-MB-231) human breast cancer cell lines.

The effects of cellular extracts (CE) and conditioned medium (CM) of embryonic mouse BALB/c-3T3 (clone A 31) cells on the proliferation and DNA content of hormone-dependent T-47D and hormone-independent MDA-MB-231 breast cancer cell lines were explored. After 6 days of culture, CE and CM provoke an intense proliferative effect in T-47D cells which correlates with DNA content. In contrast, in the MDA-MB-231 cells a significant inhibitory effect was observed. For both CE and CM the action was dose-dependent. In the T-47D cells, the CM can abolish the inhibitory effect provoked by the potent antiestrogen ICI 164,384. It is concluded that mouse embryonic BALB/c-3T3 cells contain factors which can stimulate or inhibit the growth of human mammary cancer cells.