DEAD-box RNA Helicase 39 Promotes Invasiveness and Chemoresistance of ER-positive Breast Cancer

Purpose: DDX39 is a DEAD-box RNA helicase that unwinds double-stranded RNA in an ATP-dependent manner. This study evaluated the prognostic and predictive significance of DDX39 in breast cancer (BC). Methods: The cellular proliferation, invasion, and drug cytotoxicity by DDX39 siRNA were evaluated in MCF7 (ER-positive) and MDA-MB-231 (ER-negative) cell lines. A total of 27 datasets (total 8110 accessible cases) with following-up information were collected from Asia, Europe, and North America to explore associations between DDX39 gene expression and clinical parameters of BC patients. Results: Down-regulation of DDX39 by siRNA significantly reduce the cell growth and invasion ability in MCF7 cells, but only slightly in MDA-MB-231 cells. The DDX39 mRNA level was elevated in breast adenocarcinoma compared with normal breast tissue (p<0.01). Higher DDX39 level was significantly correlated with larger tumor size (p<0.01) and poorer tumor differentiation (p<0.01). The prognostic significance of DDX39 for BC was assessed by pooled-analysis and meta-analysis. Kaplan-Meier analysis demonstrated that increased DDX39 mRNA expression was associated with poor outcomes significantly in a dose-dependent manner in ER-positive BC. The prognostic performance of DDX39 mRNA was comparable to 21-gene, 70-gene, and wound-response gene signatures, and it was superior to the TNM stage. Lower DDX39 expression was associated with reduced relative risk death on ER-positive BC with chemotherapy or radiotherapy. Inhibition of DDX39 by siRNA could significantly enhance the sensitivity of MCF-7 to doxorubicin. Conclusion: DDX39 may be a potential novel prognostic and predictive biomarker for BC patients with ER-positive status.