FIGURE 3.

ATF4 stimulates drug‐induced apoptosis by activating CHOP transcription. (A) The GSEA‐enriched ATF4 target genes from the two signatures (ATF4 sig‐1 and ATF4 sig‐2) was intersected with enriched apoptosis related genes from apoptosis signature (Apoptosis sig) to identify the implicated apoptosis related genes. (B) CHOP mRNA expression in sensitive cells (SGC7901 and BGC823) or resistant cells (SGC‐R and BGC‐R) under DDP (1.2 μg/ml) incubation for 24 h was measured by qRT‐PCR. (C) CHIP was performed to detect the binding of ATF4 to CHOP promoter in SGC7901 or BGC823 cells with DDP (1.2 μg/ml) treatment for 6 h, rabbit IgG was used as control. (D) After ATF4 over‐expression and DDP treatment for 24 h in resistant cells [SGC‐R (left) and BGC‐R (right)], CHOP mRNA level was detected by qRT‐PCR. (E) CHOP mRNA level was measured by qRT‐PCR in sensitive cells [SGC7901 (up) and BGC823 (down)] with ATF4 knockdown and DDP (1.2 μg/ml) incubation for 24 h. (F) Cell viability of SGC7901 (up) or BGC823 (down) cells with CHOP knockdown and DDP treatment for 24 h was measured by MTS assay