Fig. 2. SIRT1 inhibits chemoresistance of GC cells.

a The IC50 of cisplatin was determined by MTS assays. The mean values of the IC50 are shown (n = 3). b, c The percentages of Annexin V-positive cells upon cisplatin (CDDP) treatment (1.5 µg/ml, 36 h) were examined by flow cytometry. Cells treated with NaCl were used as a control. Data are presented as mean ± SD (n = 3). d Western blot was used to analyze the expression levels of caspase-3 and cleaved caspase-3 after incubation with cisplatin for 48 h (10 µg/ml for AGS cells and 1.5 µg/ml for BGC-823 and SGC-7901 cells). e–g Stable SIRT1-overexpression/-knockdown SGC-7901 cells and the corresponding control cells were used for tumorigenesis assays. Cisplatin (5 mg/kg, every 5 days) or an equal volume of NaCl was intraperitoneally injected when the tumor volumes reached 100 mm³ (eight mice in each group). After 3 weeks, the mice were euthanized, and the tumor nodules were harvested. Representative images of the tumor nodules (e) and TUNEL staining (f, ×200, scale bars: 100 µm) are shown. The tumor volumes were measured and shown in (g) (mean ± SD, n = 8). *** represents p < 0.001.