miRomics and Proteomics Reveal a miR-296-3p/PRKCA/FAK/Ras/c-Myc Feedback Loop Modulated by HDGF/DDX5/{beta}-catenin Complex in Lung Adenocarcinoma

Purpose: This study was performed to identify the detailed mechanisms by which miR-296-3p functions as a tumor suppressor to prevent lung adenocarcinoma (LADC) cell growth, metastasis, and chemoresistance.

Experimental Design: The miR-296-3p expression was examined by real-time PCR and in situ hybridization. MTT, EdU incorporation, Transwell assays, and MTT cytotoxicity were respectively performed for cell proliferation, metastasis, and chemoresistance; Western blotting was performed to analyze the pathways by miR-296-3p and HDGF/DDX5 complex. The miRNA microarray and luciferase reporter assays were respectively used for the HDGF-mediated miRNAs and target genes of miR-296-3p. The ChIP, EMSA assays, and coimmunoprecipitation combined with mass spectrometry and GST pull-down were respectively designed to analyze the DNA–protein complex and HDGF/DDX5/β-catenin complex.

Results: We observed that miR-296-3p not only controls cell proliferation and metastasis, but also sensitizes LADC cells to cisplatin (DDP) in vitro and in vivo. Mechanistic studies demonstrated that miR-296-3p directly targets PRKCA to suppress FAK–Ras-c–Myc signaling, thus stimulating its own expression in a feedback loop that blocks cell cycle and epithelial–mesenchymal transition (EMT) signal. Furthermore, we observed that suppression of HDGF–β-catenin–c-Myc signaling activates miR-296-3p, ultimately inhibiting the PRKCA–FAK–Ras pathway. Finally, we found that DDX5 directly interacts with HDGF and induces β-catenin–c-Myc, which suppresses miR-296-3p and further activates PRKCA–FAK–Ras, cell cycle, and EMT signaling. In clinical samples, reduced miR-296-3p is an unfavorable factor that inversely correlates with HDGF/DDX5, but not PRKCA.

Conclusions: Our study provides a novel mechanism that the miR-296-3p–PRKCA–FAK–Ras–c-Myc feedback loop modulated by HDGF/DDX5/β-catenin complex attenuates cell growth, metastasis, and chemoresistance in LADC. Clin Cancer Res; 23(20); 6336–50. ©2017 AACR.

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