The AKT/GSK3β-Mediated Slug Expression Contributes To Oxaliplatin Resistance In Colorectal Cancer Via Upregulation Of ERCC1

Background: Clinically,patients with colorectal cancer underwent postoperative adjuvant chemotherapy with Oxaliplatin,but the efficacy of chemotherapy was not satisfactory,mainly due to the development of drug resistance.So far,the molecular mechanisms mediating oxaliplatin resistance remain unclear.Methods: Oxaliplatin-resistant HCT116 cells was established by gradient increase of oxaliplatin at low concentration combined with intermittent induction at high concentration.Invasiveness of CRC cells and resistance to oxaliplatin and cisplatin were determined by Transwell assay and CCK8 assay,respectively.Cytoplasm and nucleus separation test and immunofluorescence staining were used to determine the location of Slug.The key genes maintaining drug-resistant phenotype,the specific mechanism of oxaliplatin upregulating Slug and the signal pathways involved were explored and verified by proteomics and western blot.Protein level of Slug and ERCC1 in clinical samples were detected by immunohistochemistry,and Kaplan-Meier analysis was used to evaluate the correlation between Slug expression level and patient prognosis.Results: We found that HCT116/OXA cells mediated the chemotherapy resistance by upregulating ERCC1 expression.Simultaneously,epithelial-mesenchymal transition phenotype and overexpression of Slug were observed in HCT116/OXA cells.Slug silencing reversed the EMT phenotype,downregulated ERCC1 expression,and weakened the resistance of drug-resistant cells to oxaliplatin.In addition,the Slug expression was significantly upregulated after oxaliplatin treatment in HCT116 and SW480 cells,and the enhanced Slug was found to enter the nucleus from cytoplasm.Further mechanistical studies revealed that oxaliplatin enhances the phosphorylation level of GSK3β by activating the AKT signaling pathway,thereby leading to the enhancement of Slug expression.Moreover,in CRC patients,co-expression of Slug and ERCC1 was observed,and Slug expression level was markedly concerned with prognosis of CRC patients.Conclusion: Oxaliplatin upregulates the expression level of Slug by activating the AKT/GSK3β signaling pathway in colorectal cancer cells,which the latter induces EMT transformation in tumor cells,and mediates the resistance of colorectal cancer cells to oxaliplatin by regulating the expression of ERCC1.Therefore,inhibition of AKT/GSK3β/Slug signaling pathway is expected to overcome both metastasis and chemotherapy resistance of CRC cells,which is benefit for the clinical effect of CRC patients.