Decitabine and Cisplatin are Synergistic to Exert Anti-Tumor Effect on Gastric Cancer via Inducing Sox2 DNA Demethylation

BACKGROUND: Cisplatin is a vital chemotherapy regimen for gastric cancer (GC), while partial response is observed (approximately 40%) because of drug resistance. Thus, it is urgent to improve drug sensitivity to improve the therapeutic effect of cisplatin on GC. PURPOSE: The study was performed to explore the synergistic effect of decitabine and cisplatin in GC. MATERIALS AND METHODS: Cancer and matched adjacent tissues from patients with GC were obtained and quantitative real-time PCR (qRT-PCR), Western blot and immunohistochemistry were performed to evaluate Sox2 expression level. Methylation-specific PCR (MSP) was performed to assess the effect of 5-aza-2ʹ-deoxycytidine (5-Aza-CdR) on Sox2 promoter. Cell proliferation assay, scratch-wound migration assay and Transwell invasion ability were performed to assess the effect of 5-Aza-CdR on proliferation, migration and invasion ability. Meantime, the effect of 5-Aza-CdR was also investigated in gastric cell lines BGC-823 and nude mouse xenograft tumor model. Finally, the anti-cancer effect of decitabine, cisplatin and their combination treatment were investigated in a BGC-823 and nude mouse xenograft tumor model, Sox2 methylation level, Sox2 expression of BGC-823 and xenograft tumors were analyzed by MSP, qRT-PCR and Western blot. RESULTS: Sox2 expression was significantly associated with different differentiated degrees, depth of invasion (0.0011), lymph node metastasis (0.0013), and TNM stage (0.0002). Next, methylation inhibitor 5-Aza-CdR restored Sox2 expression to promote proliferation, migration and invasion in vitro and in vivo. Finally, cisplatin and decitabine was found to be synergistic to inhibit proliferation of xenograft tumors. Likewise, cisplatin and decitabine were also synergistic to induce Sox2 DNA demethylation to promote Sox2 mRNA and protein expression in BGC-823 and xenograft tumors. CONCLUSION: Cisplatin and decitabine could be synergistic to induce Sox2 DNA demethylation to promote expression of the Sox2 gene, which exerted an anti-tumor effect on GC. It may suggest an insight for innovative therapeutics of GC.