Fig. 3

Tunicamycin increases chemotherapy-induced cell death by aggravating ER stress and enhancing apoptosis. a Survival of GC cells measured by CCK-8 after treatment with monotherapy (Adr) or dual therapy (Adr and Tu) for 48 h. Adr, adriamycin; the concentrations of Tu were 0/0.2/0.4/0.8 μg/ml. ns, non-significant; *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001 (green, +Tu 0.2 versus standard; red, +Tu 0.4 versus standard; blue, +Tu 0.8 versus standard). b Apoptotic cells detected by flow cytometry. Cells were subjected to monotherapy (Adr, 0.25/8 μg/ml for SGC7901 and SGC7901/ADR, respectively) or dual therapy (Adr, same as the former; Tu, 0.8 μg/ml for both) for 48 h before the apoptosis assay. ns, non-significant; ***P < 0.001, ****P < 0.0001. The corresponding FCM graphs were shown in Additional file 7: Figure S6. c Changes in UPR-related genes assayed by PCR array in SGC7901/ADR (dual therapy group versus monotherapy group). Group (A & T), dual therapy with Adr (8 μg/ml) and Tu (0.8 μg/ml) for 48 h; Group (A), monotherapy with Adr (8 μg/ml) for 48 h, the control group. The colored dots represent over-expressed or under-expressed genes; the black dots represent unchanged genes. P < 0.05. d Expressions of proteins involved in the UPR and apoptosis signaling determined by WB in SGC7901 and SGC7901/ADR. Cells were subjected to the same treatments as above (3b) before protein extraction. All proteins were normalized to β-actin. e Expression levels of CHOP, Cl-PARP and Cl-caspase 3 in SGC7901/ADR detected by IF after treatment with monotherapy or dual therapy for 48 h. The concentrations of drugs were the same as those in 3c. (400 ×; scale bar, 50 μm)