Homeobox A7 increases cell proliferation by up-regulation of epidermal growth factor receptor expression in human granulosa cells

Abstract

BackgroundHomeobox (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.MethodsTo 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.ResultsOur 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.ConclusionsOur 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.

Epidermal growth factor differentially regulates activin subunits in the zebrafish ovarian follicle cells via diverse signaling pathways

“…Recently, a study in the medaka showed that like the situation in mammals, the activation of EGFR induced phosphorylation of both MAPK3/1 and Akt in mouse melanocytes expressing medaka egfra upon treatment with medaka EGF ligands, such as HB-EGF (Laisney et al, 2010). To understand EGFR signaling and to tease out the mechanisms underlying EGF-regulated expression of activin subunits in the zebrafish ovary, we investigated several intracellular pathways that had been reported in mammals to mediate EGFR signaling, including MAPK3/1 (Su et al, 2002;Reizel et al, 2010;Sabri et al, 2011), p38 MAPK (Hsieh et al, 2011Sabri et al, 2011), PKC (Fan et al, 2009b;Suzuki et al, 2008) and PI3K (Zhang et al, 2010;Yan et al, 2009;Sabri et al, 2011) pathways, using both pharmacological and Western blot approaches. These four pathways were chosen also because they had been shown to regulate the functions of granulosa cells, cumulus cells and theca cells as well as final oocyte maturation.…”

“…Other pathways have also been implicated in EGF signaling in the ovary of different species. EGF has been reported to activate PI3K/Akt in human granulosa cells (Zhang et al, 2010), PKC in the chicken ovary (Woods et al, 2007), and p38 MAPK in ovarian cancer cells (Zhou et al, 2007). To understand the intracellular signaling mechanisms that underlie EGF stimulation of activin subunits in the zebrafish ovary, we undertook this study using pharmacological approach, Western blot and immunohistochemical (IHC) staining, and our results provide evidence that EGF signaling in the ovary involves activin system and it controls the expression of three activin subunits via diverse signal transduction pathways.…”

The Role ofHoxGenes in Female Reproductive Tract Development, Adult Function, and Fertility

“…HOXA7 modulates granulosa cell growth and proliferation not only via the regulation of the epidermal growth factor receptor (EGFR), but also forms dimers with the HOX gene cofactor pre-B-cell leukemia transcription factor 2 (PBX2) to bind the specific promoter regions in the human granulosa cells. HOXA7 plays an important role in ovarian follicular maturation (Ota et al 2008;Zhang et al 2010). …”

Sensitivity of human granulosa cell tumor cells to epidermal growth factor receptor inhibition

“…Similarly, it has previously been shown that AG1478 treatment (another EGFR inhibitor) reduced KGN cell number (Zhang et al 2010). EGFR inhibitors also induced the activation of caspase-3/7 in GCT cells at similar concentrations as the observed reduction in cell viability, suggesting that the decrease in cell viability is caused by apoptosis.…”

“…Total EGFR protein expression in GCT tissue samples and in GCT cell lines, the KGN and COV434, has been demonstrated earlier (Leibl et al 2006, Nosov et al 2009, Zhang et al 2010, Jamieson & Fuller 2012, Nofech-Mozes et al 2012, Wang et al 2012. In primary and recurrent GCTs, EGFR expression localizes to the cell membrane and cytoplasm (Leibl et al 2006, Nosov et al 2009, Nofech-Mozes et al 2012, Wang et al 2012 and has been suggested to predict GCT recurrence.…”