Figure 5. Activation of the eIF2α-ATF4 pathway contributes to mitochondrial dysfunction-induced xCT expression and high xCT expression in cisplatin-resistant cancer cells.
A, B. Western blot analysis of the eIF2α-ATF4-xCT pathway in SC-M1 cells under oligomycin (A) and antimycin A (B) treatments for 24 h, respectively. C. Western blot analysis of the eIF2α-ATF4-xCT pathway between parental and the cisplatin-resistant gastric cancer cells. The immunoblot values were normalized to α-tubulin. The eIF2α-ATF4-xCT pathway was determined by Western blot with specific antibodies against phosphorylated eIF2α, eIF2α, ATF4, and xCT. D. The specific eIF2α siRNA (60 pmol for 4 × 105 cells in a 6-cm dish) was used to knock down eIF2α in the SC-M1CisR gastric cancer cells, and the eIF2α-ATF4-xCT pathway was analyzed by Western blot analysis. E. The eIF2α-silenced SC-M1CisR cells (sieIF2α) and the control SC-M1CisR cells were treated with cisplatin for 48 h. The cell viability was determined by SRB assay. F. The SC-M1 cells were treated with salubrinal (Sal, 30 μM) for 24 h and, the eIF2α-ATF4-xCT pathway was analyzed by Western blot analysis. The immunoblot values were normalized to α-tubulin. G. The SC-M1 cells were pre-treated with 30 μM salubrinal for 24 h, followed by co-treatment with cisplatin for 48 h. The cell viability was determined by MTT assay. Data represent the mean ± SEM of three independent experiments. *p < 0.05, compared to the control group or parental cells; & p < 0.05, compared to the individual siScr group.