Synergistic effect between PPMP and other anticancer drugs in inhibiting the proliferation of tumor cells. (A-C) MCF-7, 4T1.2 or PC-3 cells were treated with various concentrations of free PPMP, free DOX or the combination of PPMP and DOX. (D-F) MCF-7, 4T1.2 or PC-3 cells were treated with various concentrations of free PPMP, free PTX or the combination of PPMP and PTX. (G-I) MCF-7, 4T1.2 or PC-3 cells were treated with various concentrations of free PPMP, free C6-ceramide or the combination of PPMP and C6-ceramide. After 48 h, the cytotoxicity was determined by MTT assay. The experiments was performed in triplicate and repeated three times. Data are presented as means ± SD.