miR-199a-3p targets stemness-related and mitogenic signaling pathways to suppress the expansion and tumorigenic capabilities of prostate cancer stem cells
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Ruifang Liu1,2,3, Can Liu2, Dingxiao Zhang2,3,*, Bigang Liu2, Xin Chen2,3,*, Kiera Rycaj2,3,*, Collene Jeter2, Tammy Calhoun-Davis2, Yandong Li1, Tao Yang1, Junchen Wang1, Dean G. Tang1,2,3,4
1Cancer Stem Cell Institute, Research Center for Translational Medicine, East Hospital, Tongji University School of Medicine, Shanghai 200120, China
2Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Science Park, Smithville, TX 78957, USA
3Department of Pharmacology & Therapeutics, Roswell Park Cancer Institute, Buffalo, NY 14263, USA
4Centers 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
Ruifang Liu, email: email@example.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
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.
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