ORIGINAL ARTICLE – TRANSLATIONAL RESEARCH AND BIOMARKERS The H3K9 Methyltransferase G9a Represses E-cadherin and is Associated with Myometrial Invasion in Endometrial Cancer Sheng-Mou Hsiao, MD 1 , Min-Wei Chen, PhD 2 , Chi-An Chen, MD 3 , Ming-Hsien Chien, PhD 4,5 , Kuo-Tai Hua, PhD 6 , Michael Hsiao, PhD 7 , Min-Liang Kuo, PhD 8 , and Lin-Hung Wei, MD, PhD 2,3 1 Department of Obstetrics and Gynecology, Far Eastern Memorial Hospital, New Taipei, Taiwan; 2 Department of Oncology, National Taiwan University Hospital, Taipei, Taiwan; 3 Department of Obstetrics and Gynecology, National Taiwan University Hospital, Taipei, Taiwan; 4 Graduate Institute of Clinical Medicine, Taipei Medical University, Taipei, Taiwan; 5 Wan Fan Hospital, Taipei Medical University, Taipei, Taiwan; 6 Graduate Institute of Toxicology, College of Medicine, National Taiwan University, Taipei, Taiwan; 7 Genomics Research Center, Academia Sinica, Taipei, Taiwan; 8 Institute of Biochemical Sciences, College of Life Science, National Taiwan University, Taipei, Taiwan ABSTRACT Background. Emerging evidence suggests that G9a, a histone methyltransferase, is involved in tumor progression and metastasis. However, the functional significance of G9a in endometrial carcinogenesis has not been defined. Methods. The differential expression of G9a in cancer and normal tissues was assessed using an array of 28 paired samples. Tissue specimens from 94 patients with endo- metrial cancer who underwent primary surgery were immunohistochemically evaluated for G9a and E-cadherin expression. To assess the biologic role of G9a in endo- metrial cancer, G9a was either stably knocked down or knocked down using a tetracycline-controllable system in endometrial cancer cells, followed by functional assays. Results. Increased G9a expression was identified in endo- metrial cancer tissues, and its expression was specifically correlated with deep myometrial invasion. Cell invasiveness was inhibited by an RNAi-mediated knockdown of G9a in invasive endometrial cancer cells in vitro and in vivo. An important mediator of G9a-induced tumor invasion is the epigenetic silencing of E-cadherin. Knockdown of G9a restored E-cadherin expression by reducing H3K9me2 lev- els and decreasing CDH1 promoter DNA methyltransferase recruitment. Knockdown of RNAi-mediated E-cadherin substantially relieved the invasion suppression imposed by G9a suppression. A significant negative correlation between G9a and E-cadherin expression was observed in endometrial cancer (Spearman’s rho, -0.27; P = 0.02). Conclusions. This study provides the first clear evidence that G9a contributes to endometrial cancer progression. Mechanistic investigations suggest that E-cadherin repres- sion mediates the effects of G9a. Targeting G9a-mediated epigenetic pathway dysregulation may be a therapeutic strategy for endometrial cancers. Histone posttranslational modifications are a funda- mental regulatory mechanism that enables epigenetic control of diverse biologic processes. Among these modi- fications, histone H3 lysine 9 (H3K9) methylation is a well- conserved epigenetic marker of heterochromatin formation and transcriptional silencing. 1 As findings show, G9a is a member of the Suv39h subgroup of SET domain-contain- ing molecules with histone lysine methyltransferase activity. 2 In vivo, G9a forms a heteromeric complex with GLP/Eu-HMTase1 that catalyzes H3K9me1 and H3K9me2 methylation at euchromatin. 3 Functional G9a analysis has shown critical roles in gametogenesis, early embryogene- sis, and lymphocyte development and activation. 4 Recent findings support a critical role of G9a in carcinogenesis. Sheng-Mou Hsiao and Min-Wei Chen have contributed equally. Electronic supplementary material The online version of this article (doi:10.1245/s10434-015-4379-5) contains supplementary material, which is available to authorized users. Ó Society of Surgical Oncology 2015 First Received: 13 August 2014 L.-H. Wei, MD, PhD e-mail: weilh1966@gmail.com Ann Surg Oncol DOI 10.1245/s10434-015-4379-5