Steroidogenic factor-1 regulates the rate of proliferation of normal and neoplastic rat ovarian surface epithelial cells in vitro

Genetic and epigenetic alterations of steroidogenic factor‑1 in ovarian tumors

Steroidogenic factor-1 (SF-1), the product of the NR5A1 gene, is an essential transcription factor that is known to regulate steroidogenesis in ovarian epithelia, including the synthesis of progesterone, a suppressor of ovarian cancer. Expression of the SF-1 protein, a potential ovarian tumor suppressor, has been demonstrated in normal OSE cells, but is lost in most ovarian tumors and ovarian tumor cell lines. We examined loss of heterozygosity (LOH) and promoter methylation as potential mechanisms that may explain the loss of SF-1 protein in ovarian tumor tissues. Genotyping of three NR5A1 SNPs in matched tumor/normal tissues identified LOH in 16/36 (44%) of the ovarian tumors successfully analyzed, and somatic mutations (gain of allele) in 10% of the tumors. Furthermore, a methylation-sensitive restriction enzyme method was used to demonstrate statistically significant (p<0.0001) increase in the frequency of NR5A1 gene methylation in ovarian tumors (36/46; 78%) versus normal ovaries (1/11; 9%). These data suggest that the SF-1 encoding gene exhibits frequent genetic (LOH/base substitution) and epigenetic (methylation) somatic alterations in ovarian tumors. These data also present novel molecular mechanisms that may explain the loss of SF-1 protein in ovarian tumors, and its potential role in ovarian carcinogenesis.

Increased steroidogenic factor-1 dosage triggers adrenocortical cell proliferation and cancer

Steroidogenic factor-1 (SF-1/Ad4BP; NR5A1), a nuclear receptor transcription factor, has a pivotal role in adrenal and gonadal development in humans and mice. A frequent feature of childhood adrenocortical tumors is SF-1 amplification and overexpression. Here we show that an increased SF-1 dosage can by itself augment human adrenocortical cell proliferation through concerted actions on the cell cycle and apoptosis. This effect is dependent on an intact SF-1 transcriptional activity. Gene expression profiling showed that an increased SF-1 dosage regulates transcripts involved in steroid metabolism, the cell cycle, apoptosis, and cell adhesion to the extracellular matrix. Consistent with these results, increased SF-1 levels selectively modulate the steroid secretion profile of adrenocortical cells, reducing cortisol and aldosterone production and maintaining dehydroepiandrosterone sulfate secretion. As a model to understand the mechanisms of transcriptional regulation by increased SF-1 dosage, we studied FATE1, coding for a cancer-testis antigen implicated in the control of cell proliferation. Increased SF-1 levels increase its binding to a consensus site in FATE1 promoter and stimulate its activity through modulation of the recruitment of specific cofactors. On the other hand, sphingosine, which can compete with phospholipids for binding to SF-1, had no effect on the SF-1 dosage-dependent increase of adrenocortical cell proliferation and expression of the FATE1 promoter. In mice, increased Sf-1 dosage produces adrenocortical hyperplasia and formation of tumors expressing gonadal markers (Amh, Gata-4), which originate from the subcapsular region of the adrenal cortex. Gene expression profiling revealed that genes involved in cell adhesion and the immune response and transcription factor signal transducer and activator of transcription-3 (Stat3) are differentially expressed in Sf-1 transgenic mouse adrenals compared with wild-type adrenals. Our studies reveal a critical role for SF-1 dosage in adrenocortical tumorigenesis and constitute a rationale for the development of drugs targeting SF-1 transcriptional activity for adrenocortical tumor therapy.

Immunolocalization of nuclear transcription factors, DAX-1 and Ad4BP/SF-1, in human common epithelial ovarian tumors: correlations with StAR and steroidogenic enzymes in epithelial ovarian carcinoma

Intratumoral steroidogenesis is considered to play important roles in the biologic behavior of common epithelial ovarian carcinoma. Recent studies have demonstrated the important roles of Ad4BP/SF-1 and DAX-1 in regulation of steroidogenesis. In this study, we evaluated DAX-1, Ad4BP/SF-1, StAR, and steroidogenic enzyme expressions and their correlations in epithelial ovarian carcinomas to evaluate the possible roles of these factors in regulation of intratumoral steroid metabolism and/or production. Immunolocalization of DAX-1, Ad4BP/SF-1, StAR, and steroidogenic enzymes were examined in 90 epithelial ovarian carcinomas. mRNA expression of these proteins was evaluated using real-time polymerase chain reaction (PCR) in 23 cases for further characterization. DAX-1 and Ad4BP/SF-1 immunoreactivity was detected predominately in the nuclei of tumor cells, whereas that of StAR and steroidogenic enzymes was present in the cytoplasm. We detected a significant positive correlation between StAR and steroidogenic enzymes immunoreactivity and Ad4BP/SF-1 and statistically inversed correlation with DAX-1. A positive statistical correlation was detected between intratumoral stromal Ad4BP/SF-1 immunoreactivity and clinicopathologic parameters of carcinoma patients. Results of real-time PCR analysis were correlated with those of immunohistochemical studies. The status of intratumoral DAX-1, Ad4BP/SF-1, and StAR and steroidogenic enzymes in epithelial cells and intratumoral stromal cells of epithelial ovarian carcinoma may contribute in the progression and/or aggressiveness of these tumors.

Ovarian surface epithelium: biology, endocrinology, and pathology

The epithelial ovarian carcinomas, which make up more than 85% of human ovarian cancer, arise in the ovarian surface epithelium (OSE). The etiology and early events in the progression of these carcinomas are among the least understood of all major human malignancies because there are no appropriate animal models, and because methods to culture OSE have become available only recently. The objective of this article is to review the cellular and molecular mechanisms that underlie the control of normal and neoplastic OSE cell growth, differentiation, and expression of indicators of neoplastic progression. We begin with a brief discussion of the development of OSE, from embryonic to the adult. The pathological and genetic changes of OSE during neoplastic progression are next summarized. The histological characteristics of OSE cells in culture are also described. Finally, the potential involvement of hormones, growth factors, and cytokines is discussed in terms of their contribution to our understanding of the physiology of normal OSE and ovarian cancer development.

Hepatocyte growth factor disrupts cell contact and stimulates an increase in type 3 inositol triphosphate receptor expression, intracellular calcium levels, and apoptosis of rat ovarian surface epithelial cells

The present studies revealed that hepatocyte growth factor (HGF) disrupts cell contact, increases both type 3 IP3 receptor and intracellular calcium ([Ca2+]i) levels and induces apoptosis of rat ovarian surface epithelial cells (ROSE-179 cells). Type 3 IP3 receptor was only increased in cells that lost cell contact. Disrupting cell contact by depleting extracellular calcium (Ca2+) also resulted in an increase in [Ca2+]i levels and an increase in apoptosis. These responses were prevented by the addition of 0.7 mM Ca2+. Actinomycin D and cycloheximide prevented apoptosis that resulted from Ca2+ removal. In situ hybridization studies revealed that type 3 IP3 receptor was expressed at relatively low levels by ROSE-179 cells cultured with Ca2+ but at high levels in the absence of Ca2+. ROSE-179 cells cultured in Ca2+-free medium with type 3 IP3 receptor antisense oligonucleotide lost cell contact but did not show an increase in either type 3 IP3 receptor protein, [Ca2+]i, or apoptosis. The nonsense oligonucleotide did not alter these responses to Ca2+ removal. Thus, the disruption of cell contact by either HGF or Ca2+ depletion increases the expression of type 3 IP3 receptor, which causes an increase in [Ca2+]i and the apoptotic death of ROSE-179 cells.