miR-138-5p modulates the expression of excision repair cross-complementing proteins ERCC1 and ERCC4, and regulates the sensitivity of gastric cancer cells to cisplatin

The microRNA (miR)-138-5p affects the chemotherapeutic sensitivity of several human cancer types. In the present study, the expression and regulatory mechanisms of miR-138-5p were investigated in the gastric cancer cell line SGC7901 and its cisplatin-resistant derivative SGC7901/DDP. Gene microarray and reverse transcription-quantitative polymerase chain reaction analyses revealed that miR-138-5p was expressed at significantly lower levels in SGC7901/DDP compared with SGC7901 cells. Using computational predictive algorithms, two proteins involved in the nuclear excision repair pathway were identified, excision repair cross-complementing (ERCC)1 and ERCC4, as putative miR-138-5p target genes. Western blot analysis confirmed that ERCC1 and ERCC4 expression levels were inversely proportional to miR-138-5p levels in SGC7901 and SGC7901/DDP cells. Furthermore, ERCC1 and ERCC4 were upregulated in SGC7901 cells expressing miR-138-5p-targeting short hairpin RNA and, conversely, downregulated in SGC7901/DDP cells overexpressing miR-138-5p, confirming that this miRNA regulates ERCC protein levels. Notably, miR-138-5p silencing enhanced the cisplatin resistance of SGC7901 cells, while miR-138-5p overexpression partially reversed the cisplatin resistance of SGC7901/DDP cells. Taken together, these data suggest that miR-138-5p regulates the sensitivity of gastric cancer cells to cisplatin, possibly by modulating expression of the DNA repair proteins ERCC1 and ERCC4.