miR-199a and miR-199b stimulate the progression of diffuse gastric cancer through direct targeting of Frizzled-6

Abstract

There is no pathological difference between early and advanced diffuse gastric cancer (DGC), particularly in the gastric mucosa. In this study, we tried to identify microRNAs (miRNAs) as diagnostic biomarkers that can differentiate between early and advanced DGC. miRNA expression profiling was performed by NanoString nCounter method in human DGC tumors. miR-199a and miR-199b (miR-199a/b) were particularly up-regulated in advanced DGC compared with early DGC. Ectopic expression of miR-199a/b accelerated growth, viability, and motility of SNU601, human GC cells, and expedited tumor development in a mouse xenograft model. miR-199a/b also inhibited cell adhesion. Through 3’-UTR luciferase assay, Frizzled-6 (FZD6) was confirmed as a direct target of miR-199a/b. siRNA-mediated depletion of FZD6 increased cell growth and motility and addback of FZD6 restored cell growth, motility, and adhesion. To explore their clinicopathological roles in patients, miR-199a/b levels were measured by in situ hybridization in human DGC tumor sections. High miR-199a/b was correlated with advanced lymphovascular invasion, advanced T stages, and lymph node metastasis. Collectively, miR-199a/b promote the progression of DGC via targeting FZD6. These results imply that miR-199a/b can be used as diagnostic and prognostic biomarkers of DGC.