COMPARATIVE EFFECT OF EMBRYONIC MOUSE FIBROBLASTS (BALB C-3T3) ON THEPROLIFERATION 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 e mbryonic 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, C E 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 si gnificant inhibitory effect was observed. For both CE and CM the actio n was dose-dependent. In the T-47D cells, the CM can abolish the inhib itory effect provoked by the potent antiestrogen ICI 164,384. It is co ncluded that mouse embryonic BALB/c-3T3 cells contain factors which ca n stimulate or inhibit the growth of human mammary cancer cells.