miR-199a-3p targets stemness-related and mitogenic signaling pathways to suppress the expansion and tumorigenic capabilities of prostate cancer stem cells

// Ruifang Liu 1, 2, 3 , Can Liu 2 , Dingxiao Zhang 2, 3, * , Bigang Liu 2 , Xin Chen 2, 3, * , Kiera Rycaj 2, 3, * , Collene Jeter 2 , Tammy Calhoun-Davis 2 , Yandong Li 1 , Tao Yang 1 , Junchen Wang 1 , Dean G. Tang 1, 2, 3, 4 1 Cancer Stem Cell Institute, Research Center for Translational Medicine, East Hospital, Tongji University School of Medicine, Shanghai 200120, China 2 Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Science Park, Smithville, TX 78957, USA 3 Department of Pharmacology & Therapeutics, Roswell Park Cancer Institute, Buffalo, NY 14263, USA 4 Centers for Cancer Epigenetics, Stem Cell and Developmental Biology, RNA Interference and Non-coding RNAs, and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA * These authors have contributed equally to this work Correspondence to: Ruifang Liu, email: ruifang02.liu@gmail.com Dean G. Tang, email: Dean.Tang@Roswellpark.org Keywords: prostate cancer, miR-199a-3p, CD44, c-MYC, cancer stem cells Received: May 14, 2016      Accepted: June 13, 2016      Published: July 18, 2016 ABSTRACT Human cancers exhibit significant cellular heterogeneity featuring tumorigenic cancer stem cells (CSCs) in addition to more differentiated progeny with limited tumor-initiating capabilities. Recent studies suggest that microRNAs (miRNAs) regulate CSCs and tumor development. A previous library screening for differential miRNA expression in CD44 + (and other) prostate CSC vs. non-CSC populations identified miR-199a-3p to be among the most highly under-expressed miRNAs in CSCs. In this study, we characterized the biological functions of miR-199a-3p in CD44 + prostate cancer (PCa) cells and in tumor regeneration. Overexpression of miR-199a-3p in purified CD44 + or bulk PCa cells, including primary PCa, inhibited proliferation and clonal expansion without inducing apoptosis. miR-199a-3p overexpression also diminished tumor-initiating capacities of CD44 + PCa cells as well as tumor regeneration from bulk PCa cells. Importantly, inducible miR-199a-3p expression in pre-established prostate tumors in NOD/SCID mice inhibited tumor growth. Using target prediction program and luciferase assays, we show mechanistically that CD44 is a direct functional target of miR-199a-3p in PCa cells. Moreover, miR-199a-3p also directly or indirectly targeted several additional mitogenic molecules, including c-MYC, cyclin D1 (CCND1) and EGFR. Taken together, our results demonstrate how the aberrant loss of a miRNA-mediated mechanism can lead to the expansion and tumorigenic activity of prostate CSCs, further supporting the development and implementation of miRNA mimics for cancer treatment.