Recombinant interferon-alpha 2b affects proliferation, steroid receptors and sensitivity to tamoxifen of cultured breast cancer cells (CG-5).

Exposure of CG-5 human breast cancer cells to recombinant interferon (IFN)-alpha 2b results in a significative inhibition of cell proliferation; this is observed when cells are cultured in their standard conditions and is not modified if serum concentration present in the culture medium is lowered. Estrogen receptors are increased in CG-5 cells following a 5 day treatment with concentrations of IFN-alpha 2b ranging from 10 to 1000 IU/ml of culture medium. Progesterone receptors seem to be more influenced by a longer treatment with the drug (7 days). The Kd of both receptors is not modified by the exposure of cells to IFN-alpha 2b. Finally, the antiproliferative effect of tamoxifen on CG-5 cells is amplified by the simultaneous addition to culture medium of IFN-alpha 2b even at very low concentrations.