• Jia-Xing Zhang, Yi Xu, Ying Gao, Cui Chen, Zhou-San Zheng, Miao Yun, Hui-Wen Weng, Dan Xie, and Sheng Ye.
• Department of Oncology, the First Affiliated Hospital, Sun Yat-sen University, No. 58, Zhongshan road II, 510080, Guangzhou, People's Republic of China.
• Mol Cancer. 2017 Jan 23; 16 (1): 18.

BackgroundThe development of chemoresistance and metastasis are the leading causes of death for gastric cancer (GC) patients, however, the molecular mechanisms involved remain unclear. Dysregulation of miRNAs is associated with a variety of disease, including GC. Recently, microarray profiling analysis revealed that miR-939 was dysregulated in human GC samples, but the role of miR-939 in GC has not been intensively investigated.MethodsIn the present study, we firstly examined the expression pattern of miR-939 in two independent cohorts of clinical GC samples: one cohort of 112 GC patients with stage I-III disease who underwent surgery followed by adjuvant chemotherapy; and another cohort of 110 GC patients with stage IV disease who received palliative chemotherapy. A series of in vivo and in vitro assays were then performed to investigate the function of miR-939 in GC.ResultsWe detected that reduced expression of miR-939 was associated with chemoresistance and increased risk of tumor recurrence in GC patients. Further function study demonstrated that overexpression of miR-939 suppressed GC cell growth, and enhanced 5-fluorouracil-induced chemosensitivity by compromising cellular growth and inducing apoptosis in vitro and in vivo. Moreover, miR-939 repressed the migration and invasion of GC cells in vitro, and diminished the occurrence of lung metastasis in vivo. We further identified solute carrier family 34 member 2 (SLC34A2) was a novel target of miR-939. Mechanistically, we elucidated that miR-939 exerted its function mainly through inhibiting SLC34A2/Raf/MEK/ERK pathway, which is activated in GC. Multivariate analysis identified miR-939, SLC34A2, and their combination as independent indicators for poor prognosis and tumor recurrence in GC patients.ConclusionOur data indicate that miR-939 acts as a tumor suppressor miRNA in GC, and miR-939/SLC34A2 axis represents a novel therapeutic strategy for future GC treatment.

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