Gonadotropins upregulate the epidermal growth factor receptor through activation of mitogen-activated protein kinases and phosphatidyl-inositol-3-kinase in human ovarian surface epithelial cells

Abstract

Gonadotropins, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) have been implicated as probable risk factors in epithelial ovarian carcinomas, most of which are derived from ovarian surface epithelium (OSE). Since epidermal growth factor (EGF) increases the growth of ovarian surface epithelial cells, we determined the effect of gonadotropins on the expression of epidermal growth factor receptor (EGFR). We investigated the basal levels of EGFR mRNA and protein, and the mechanisms involved in the regulation of EGFR at the transcriptional and translational levels by FSH and LH. The immortalized OSE cell lines (IOSE) derived from normal OSE cells by transfecting SV40 T-antigen (IOSE-80 and IOSE-80PC, a post-crisis line) and ovarian cancer cell lines were employed. A significantly lower level of EGFR was observed in both IOSE-80 and IOSE-80PC cells when compared with the ovarian cancer cell lines, OVCAR-3 and SKOV-3. Treatment of IOSE-80PC cells with FSH and LH (10 -7 and 10 -6 g/ml) resulted in a significant increase in EGFR mRNA at 24 h and EGFR protein at 48 h, whereas the treatment with gonadotropins for 24-48 h induced a mild increase in EGFR in OVCAR-3, but not in SKOV-3 cells. In addition, IOSE-80PC cells treated with gonadotropins and EGF (10 nM) exhibited an additive stimulation of mitogenesis. Further, FSH and LH significantly increased activities of various kinases at 5-10 min, and pre-treatments with LY294002 (an inhibitor of PI3K) or PD98059 (an inhibitor of ERK1/2) partially blocked the gonadotropin-induced up-regulation of EGFR in IOSE-80PC cells. We investigated whether the effect of gonadotropins on EGFR mRNA levels is induced by increased transcription and/or by altered mRNA stability. Treatment of IOSE-80PC cells with FSH (10 -7 and 10 -6 g/ml) significantly enhanced the activity of the EGFR promoter (120 and 140% increase, respectively) at 24 h, and treatment with LH (10 -7 g/ml) for 24 h induced an increase in the activity of EGFR promoter (30%) in these cells. On the other hand, LH resulted in a significant increase in EGFR mRNA stability in the decay curves. Taken together, these results suggest that the effect of gonadotropins on the expression of EGFR may affect cell growth via ERK-1/-2 and PI3K pathways in preneoplastic ovarian surface epithelial cells, and that FSH and LH increase EGFR mRNA by different mechanisms. The former increased EGFR gene transcription essentially, whereas the latter mainly enhanced EGFR mRNA stability.

Luteinizing Hormone–Induced Up-Regulation of ErbB-2 Is Insufficient Stimulant of Growth and Invasion in Ovarian Cancer Cells

“…These data indicate that in this model system, introduction of LHR up-regulates ErbB-2, that LH incubation in LHR-expressing cells further up-regulates ErbB-2, and that this up-regulation correlates with cAMP and IP3 accumulation, variables associated with LHR activation. Although some studies have linked FSH receptor overexpression to increased ErbB-2 expression (43) and others have shown an up-regulation of EGFR by both FSH and LH (13), the data presented here represent, to the best of our knowledge, the first demonstration that LHR expression and activation upregulate ErbB-2 protein expression.…”

“…Epidemiologic evidence implicates the pituitary-derived gonadotropic hormones, follicle-stimulating hormone (FSH) and LH, in the development of ovarian cancer by correlating an increased risk of ovarian cancer with physiologic conditions resulting in increased exposure to LH and FSH, such as incessant ovulation, infertility treatments, and menopause (4,5). In vivo, LH influences cellular processes, including adhesion (6), apoptosis (7,8), anchorage-independent growth (9), angiogenesis (10), and proliferation in ovarian cancer cells or in ovarian epithelial cells, the putative precursor cell to epithelial ovarian cancer (11)(12)(13).…”

Activation of the PI3K/AKT pathway mediates FSH-stimulated VEGF expression in ovarian serous cystadenocarcinoma

“…FSH has also been shown to activate ERK and p38 mitogen-activated protein kinase (MAPK) in granulose cells [42,43]. Choi et al [44] found that FSH and LH activated MAPK and PI3K in human OSE cell. Additionally, FSH significantly upregulates the level of protein kinase Cα (PKCα) mRNA and protein, and the PKC pathway has been proposed to play a role in FSH-induced cell proliferation in ovarian cancer cells [27].…”

FSH–FSHR3–stem cells in ovary surface epithelium: basis for adult ovarian biology, failure, aging, and cancer

“…Besides the observed effect on normal ovaries, FSH treatment is also reported to activate epithelial cell proliferation and oncogenesis in several human OSE immortalized normal, neoplastic (IOSE-29, IOSE-29E, and HOSE), and ovarian cancer cell lines (OVCAR-3 and OVCA) (Schiffenbauer et al 1997, Zheng et al 2000, Syed et al 2001, Choi et al 2004, Ji et al 2004, Abd-Elaziz et al 2005. Interestingly, this effect of FSH is associated with activation of MAPK/ERK rather than via the cAMP pathway (Choi et al 2002(Choi et al , 2005. Li et al (2007) showed that FSH acts on tumorigenic mouse ovary surface epithelium cell line ID8 via the growth factor-type receptor isoform (FSHR3) to bring about proliferation via calcium signaling and the ERK pathway -distinct from the canonical cAMP pathway associated with G protein-coupled FSHR1 isoform.…”