EZH2 promotes colorectal cancer stem-like cell expansion by activating p21cip1-Wnt/β-catenin signaling

// Jian-Fang Chen 1, * , Xi Luo 1, * , Li-Sha Xiang 2 , Hong-Tao Li 1 , Lin Zha 1 , Ni Li 1 , Jian-Ming He 1 , Gan-Feng Xie 1 , Xiong Xie 1 , Hou-Jie Liang 1 1 Department of Oncology and Southwest Cancer Center, Southwest Hospital, Third Military Medical University, Chongqing, China 2 State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Sichuan, China * These authors have contributed equally to this work Correspondence to: Hou-Jie Liang, email: lianghoujie@sina.com Keywords: EZH2, cancer stem-like cell, colorectal cancer, cell cycle, p21 cip1 Received: December 18, 2015 Accepted: April 24, 2016 Published: May 9, 2016 ABSTRACT Because colorectal cancer (CRC) stem-like cells (CCS-like cells) contribute to poor patient prognosis, these cells are a potential target for CRC therapy. However, the mechanism underlying the maintenance of CCS-like cell properties remains unclear. Here, we found that patients with advanced stage CRC expressed high levels of polycomb group protein enhancer of zeste homologue 2 (EZH2). High expression of EZH2 in tumor tissues correlated with poor patient prognosis. Conversely, silencing EZH2 reduced CRC cell proliferation. Surprisingly, EZH2 was more highly expressed in the CCS-like cell subpopulation than in the non-CCS-like cell subpopulation. EZH2 knockdown significantly reduced the CD133 + /CD44 + subpopulation, suppressed mammosphere formation, and decreased the expression of self-renewal-related genes and strongly impaired tumor-initiating capacity in a re-implantation mouse model. Gene expression data from 433 human CRC specimens from TCGA database and in vitro results revealed that EZH2 helped maintain CCS-like cell properties by activating the Wnt/β-catenin pathway. We further revealed that p21 cip1 –mediated arrest of the cell cycle at G1/S phase is required for EZH2 activation of the Wnt/β-catenin pathway. Moreover, the specific EZH2 inhibitor EPZ-6438, a clinical trial drug, prevented CRC progression. Collectively, these findings revealed EZH2 maintaining CCS-like cell characteristics by arresting the cell cycle at the G1/S phase. These results indicate a new approach to CRC therapy.