ResearchHomeobox A 7 increases cell proliferation by up-regulation of epidermal growth factor receptor expression in human granulosa cells

Background: Homeobox (HOX) genes encode transcription factors, which regulate cell proliferation, differentiation, adhesion, and migration. The deregulation of HOX genes is frequently associated with human reproductive system disorders. However, knowledge regarding the role of HOX genes in human granulosa cells is limited. Methods: To determine the role of HOXA7 in the regulation and associated mechanisms of cell proliferation in human granulosa cells, HOXA7 and epidermal growth factor receptor (EGFR) expressions were examined in primary granulosa cells (hGCs), an immortalized human granulosa cell line, SVOG, and a granulosa tumor cell line, KGN, by real-time PCR and Western blotting. To manipulate the expression of HOXA7, the HOXA7 specific siRNA was used to knockdown HOXA7 in KGN. Conversely, HOXA7 was overexpressed in SVOG by transfection with the pcDNA3.1-HOAX7 vector. Cell proliferation was measured by the MTT assay. Results: Our results show that HOXA7 and EGFR were overexpressed in KGN cells compared to hGCs and SVOG cells. Knockdown of HOXA7 in KGN cells significantly decreased cell proliferation and EGFR expression. Overexpression of HOXA7 in SVOG cells significantly promoted cell growth and EGFR expression. Moreover, the EGF-induced KGN proliferation was abrogated, and the activation of downstream signaling was diminished when HOXA7 was knocked down. Overexpression of HOXA7 in SVOG cells had an opposite effect. Conclusions: Our present study reveals a novel mechanistic role for HOXA7 in modulating granulosa cell proliferation via the regulation of EGFR. This finding contributes to the knowledge of the pro-proliferation effect of HOXA7 in granulosa cell growth and differentiation. Background Ovarian follicular maturation represents one of the most complex and clinically important developmental processes during the reproductive life of women. Granulosa cells surround the developing oocyte, providing a critical microenvironment for follicular growth. Multiple granulosa cell dysfunctions lead to disordered ovulatory and ovarian function [1]. Moreover, granulosa cell tumors (GCTs) are serious ovarian neoplasms that can occur in women of all ages [2]. As most malignant ovarian tumors are epithelial in origin, most studies of ovarian cancer do not include GCTs [3]. Furthermore, while much is now known about the biology of normal granulosa cells [4], the molecular changes that contribute to human granulosa cell dysfunction remain to be elucidated. Homeobox (HOX) genes encode evolutionarily conserved transcription factors that are essential for embryonic morphogenesis and differentiation [5]. Mammalians have at least 39 HOX genes that are arranged in four clusters termed HOX A, B, C, and D [6]. HOX genes exert pleiotropic roles in many cell types and can regulate cell proliferation, differentiation, adhesion, and migration [7]. HOX genes play important roles in organogenesis and in the development of the human reproductive system dur* Correspondence: huanghefg@hotmail.com, peleung@interchange.ubc.ca 1 Department of Reproductive Endocrinology, Women's Hospital, School of Medicine, Zhejiang University, Hangzhou, 310006, China 2 Department of Obstetrics and Gynaecology, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, V6H 3V5,