// Guannan Zhao 1, 2, * , Qinghui Wang 3, * , Qingqing Gu 1, 2 , Wenan Qiang 4, 5 , Jian-Jun Wei 4 , Peixin Dong 6, 7 , Hidemichi Watari 6, 7 , Wei Li 3 and Junming Yue 1, 2 1 Department of Pathology and Laboratory Medicine, University of Tennessee Health Science Center, Memphis, USA 2 Center for Cancer Research, University of Tennessee Health Science Center, Memphis, USA 3 Department of Pharmaceutical Sciences, University of Tennessee Health Science Center, Memphis, USA 4 Department of Pathology, Department of Obstetrics and Gynecology, Northwestern University School of Medicine, Chicago, USA 5 Center for Developmental Therapeutics, Chemistry of Life Processes Institute, Northwestern University, Evanston, USA 6 Department of Women’s Health Educational System, Hokkaido University School of Medicine, Hokkaido University, Sapporo, Japan 7 Department of Gynecology, Hokkaido University School of Medicine, Hokkaido University, Sapporo, Japan * These authors have contributed equally to this work Correspondence to: Junming Yue, email: jyue@uthsc.edu Wei Li, email: wli@uthsc.edu Keywords: BIRC5 (survivin), CRISPR/Cas9 nickase, lentiviral vector, ovarian cancer, epithelial to mesenchymal transition Received: March 29, 2017 Accepted: September 18, 2017 Published: October 17, 2017 ABSTRACT BIRC5 encodes the protein survivin, a member of the inhibitor of apoptosis family. Survivin is highly expressed in a variety of cancers but has very low expression in the corresponding normal tissues, and its expression is often associated with tumor metastasis and chemoresistance. We report that survivin was highly expressed in ovarian cancer and strongly correlated with patient overall poor survival. For the first time, we provide experimental evidence that survivin is involved in epithelial to mesenchymal transition (EMT) in ovarian cancer cells. Lentiviral CRISPR/Cas9 nickase vector mediated BIRC5 gene editing led to the inhibition of EMT by upregulating epithelial cell marker, cytokeratin 7 and downregulating mesenchymal markers: snail2, β-catenin, and vimentin in both ovarian cancer SKOV3 and OVCAR3 cells. Consistent with this molecular approach, pharmacological treatment of ovarian cancer cells using a small molecule survivin inhibitor, YM155 also inhibited EMT in these ovarian cancer cell lines. Overexpression of BIRC5 promoted EMT in SKOV3 cells. Using molecular or pharmacological approaches, we found that cell proliferation, migration, and invasion were significantly inhibited following BIRC5 disruption in both cell lines. Inhibition of BIRC5 expression also sensitized cell responses to paclitaxel treatment. Moreover, loss of BIRC5 expression attenuated TGFβ signaling in both SKOV3 and OVCAR3 cells. Collectively, our studies demonstrated that disruption of BIRC5 expression inhibited EMT by attenuating the TGFβ pathway in ovarian cancer cells.