Helicase POLQ-like (HELQ) as a novel indicator of platinum-based chemoresistance for epithelial ovarian cancer

Objective: To investigate the role of HELQ in chemo-resistance of epithelial ovarian carcinoma (EOC), which is a critical factor of patients' prognosis. Methods: Immunohistochemistry, survival analysis of our 87 EOC patients and bioinformatics analysis of The Cancer Genome Atlas (TCGA) datasets (Nature, 2011) disclosed the clinical importance of HELQ expression. Quantitative reverse transcription polymerase chain reaction (qRT-PCR), and Western Blot analyses of EOC tissue were used to confirm it. Ectopic overexpression and RNA interference knockdown of HELQ were carried out in OVCAR3 and A2780 cell lines, respectively, to determine the effect of altered HELQ expression on cellular response to cisplatin by CCK8 assay. The DNA repair capacity of these cells was evaluated by using host-cell reactivation assay. Western Blot analyses were carried out to determine the effect of HLEQ on the DNA repair genes by using cells with altered HELQ expression. Results: HELQ expression associates with response of EOC patients to platinum-based chemotherapy and their overall survival (OS), disease free survival (DFS). HELQ overexpression or knockdown, respectively, increased and decreased the cellular resistance to cisplatin, DNA repair activity, and expression of DNA repair proteins of Nucleotide excision repair (NER) pathway. Conclusions: HELQ plays an important role in regulating the expression of DNA repair proteins NER pathway which, in turn, contributes to cellular response to cisplatin and patients' response to platinum-based chemotherapy. Our results demonstrated that HELQ could serve as a novel indicator for chemo-resistance of EOC, which can predict the prognosis of the disease.