Thioridazine reverses trastuzumab resistance in gastric cancer by inhibiting S-phase kinase associated protein 2-mediated aerobic glycolysis

Figure 3 Thioridazine increases the primary susceptibility of gastric cancer cells to trastuzumab in vitro and in vivo. A and B: HGC27-R and SGC7901-R cells were treated with phosphate-buffered saline (PBS), thioridazine (5 μM), trastuzumab (5 μg/mL), or thioridazine (5 μM) plus trastuzumab (5 μg/mL) for 24 h. S-phase kinase associated protein 2 (Skp2) expression was determined by western blotting; C and D: HGC27 and SGC7901 cells were treated with trastuzumab (10 μg/mL) or thioridazine (2.5 μM) alone or in combination for 48 h. Proliferation activity was evaluated by cell counting kit-8 assays; E and F: HGC27 and SGC7901 cells were treated with trastuzumab (10 μg/mL) or thioridazine (2.5 μM) alone or in combination for various times. The expression of Skp2 and Parp was analyzed by western blotting; G and H: HGC27 cells were treated with trastuzumab (10 μg/mL) or thioridazine (2.5 μM) alone or in combination for 24 h, followed by an apoptosis assay, quantitative results; I-K: Nude mice were injected s.c. with 0.1 mL of an HGC27 cell suspension (3 × 10⁷ cells/mL) in the right upper flank. The mice were treated with PBS, trastuzumab (0.5 mg/kg), thioridazine (25 mg/kg), or trastuzumab (0.5 mg/kg) plus thioridazine (25 mg/kg) daily by intraperitoneal (i.p.) injection beginning 7 d after cell implantation. After two weeks of drug administration, the mice were sacrificed. Primary tumors were excised, photographed, and weighed. Western blot analysis was used to assess Skp2 expression in primary tumors. ^aP < 0.05; ^bP < 0.01. Thior: Thioridazine; Trast: Trastuzumab.