SYNERGISTIC AND ANTAGONISTIC INTERACTIONS BETWEEN DOCETAXEL AND INTERFERON-BETA ON GROWTH OF HUMAN BREAST-CANCER CELLS IN-VITRO

Docetaxel and interferon-beta (IFN-beta) were tested alone and in comb ination for their antiproliferative activity against the estradiol rec eptor (ER) positive MCF-7 and the ER negative MDA-MB231 breast cancer cell lines. Cell growth inhibition was determined after a 3 day incuba tion by the sulforhodamine B assay. The antiproliferative effects of t he drug combinations were analysed using Berenbaum's hyperplane theore m to determine additive, synergistic and antagonistic effects. Docetax el was found to be equally effective in inhibiting cell growth of both cell lines. On the other hand MCF-7 cells were more sensitive to the antiproliferative activity of IFN-beta than MDA-MB231 cells. At low do cetaxel:IFN-beta molar concentration ratios a synergistic interaction was observed for MCF-7 cells, whereas an additive interaction was foun d for MDA-TMB231 cells. Higher molar ratios resulted in additive inter actions on MCF-7 and antagonistic interactions on MDA-MB231 cells. MCF -7 cells seem to be more sensitive to treatment by the combination of docetaxel and IFN-beta than the MDA-MB231 cells. Therefore an ER posit ive breast carcinoma may possibly profit by the combination of docetax el and IFN-beta, but further studies are necessary to clarify the ther apeutic usefulness and optimal scheduling of the drug combination.