The in vitro interaction of RA-233 and several interferons on human cell lines

The antiproliferative effects of six different human interferons were examined in two human cell lines: HM7 (human melanoma cell line) and MDA-MB-231 (human breast carcinoma cell line). A dose-response curve was developed for each interferon in which the maximum dose applied gave at least 30% growth inhibition of control values after 96-128 hours of continuous exposure. An amount of RA-233 which caused 25% growth inhibition (0.05 mg for both HM7 and MDA-MB-231 cell lines) was added to the cultures with various doses of each interferon. The inhibitory effects of RA-233 and each interferon were additive at low concentrations. In no case was a synergistic effect observed. Unlike with human fibroblast interferon, we could not show a synergistic inhibitory effect between RA 233 and any of the six different interferons on these two human epithelial tumor cell lines.