Synergism between R115777 and paclitaxel or docetaxel in R115777-resistant MM cells. RPMI8226/R5 cells were treated with drugs for 72 hours before MTT assays. Results represent means and standard deviations of 4 independent experiments. (A,C) R115777 enhanced the cytotoxic effects of paclitaxel or docetaxel. (B,D) Isobologram based on data from panels A and C, showing synergism between R115777 and paclitaxel or docetaxel.