(A, D) OCM1 and M619 cells were seeded in 96-well plates and treated with increasing doses of pemetrexed or cisplatin for 36 hours. Cell survival was estimated using an SRB assay. The expression of proteins related to apoptosis in the pemetrexed or cisplatin group was examined by western blotting. (B, E) To perform a dose-gradient assay, cells were treated with increasing doses of pemetrexed or cisplatin for 36 hours. (C, F) To perform a time-gradient assay, cells were treated with 2.5 μmol/L pemetrexed or 5 μmol/L cisplatin for the indicated time, then, western blotting analysis was used to determine the expression levels of apoptosis-related proteins. CF: cleaved form. CFs: plural of cleaved form. All data are presented as the mean ± S.D.