3-MA enhances CDDP-induced inhibition of cell proliferation. Cell proliferation inhibition ratios of MG63 cells treated with various drugs. MG63 cells were treated with CDDP (10 µg/ml), autophagy inhibitor 3-MA (6 mM), or co-treated with CDDP and 3-MA, and evaluated using an MTT assay. Results are presented as the mean ± standard error for combined data from five separate experiments. CDDP significantly increased the cell proliferation inhibition ratio of MG63 cells compared with that of untreated control cells (*P<0.05). CDDP + 3-MA significantly increased the cell proliferation inhibition ratio of MG63 cells compared with that of cells treated with CDDP alone (P<0.05). There was no significant difference between the control and 3-MA groups (P>0.05). CDDP, cisplatin; 3-MA, 3-methyladenine.