Induction of a menopausal state alters the growth and histology of ovarian tumors in a mouse model of ovarian cancer.

OBJECTIVE: Ovarian cancer is often diagnosed in women after menopause when the levels of the serum gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are increased because of the depletion of growing follicles within the ovary. The ability of FSH and LH to modulate the disease has not been well studied owing to a lack of physiologically relevant models of ovarian cancer. In this study, 4-vinylcyclohexene diepoxide (VCD) was used to deplete ovarian follicles and increase the levels of circulating FSH and LH in the tgCAG-LS-TAg mouse model of ovarian cancer. METHODS: VCD-induced follicle depletion was performed either before or after induction of the oncogene SV40 large and small T-antigens in the ovarian surface epithelial cells of tgCAG-LS-TAg mice, which was mediated by the intrabursal delivery of an adenovirus expressing Cre recombinase (AdCre). RESULTS: tgCAG-LS-TAg mice injected with AdCre developed undifferentiated ovarian tumors with mixed epithelial and stromal components and some features of sex cord stromal tumors. Treatment with VCD before or after AdCre injection yielded tumors of similar histology, but with the unique appearance of Sertoli cell nests. In mice treated with VCD before the induction of tumorigenesis, the ovarian tumors tended to grow more slowly. The human ovarian cancer cell lines SKOV3 and OVCAR3 responded similarly to increased levels of gonadotropins in a second model of menopause, growing more slowly in ovariectomized mice compared with cycling controls. CONCLUSIONS: These results suggest that follicle depletion and increased gonadotropin levels can alter the histology and the rate of growth of ovarian tumors.

Ovarian tumors in rats induced by chronic 2,3,7,8-tetrachlorodibenzo-p-dioxin treatment.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a multispecies reproductive toxicant, and it has been recently classified by IARC as a known human carcinogen. Here, we report that TCDD promotes the development of ovarian tumors in an initiation-promotion model in female Sprague Dawley rats. Rats were initiated with diethylnitrosamine (DEN) or vehicle at 70 days of age. Starting 2 or 18 weeks after initiation, rats were exposed biweekly to TCDD at a daily average dose of 125 ng/kg/day for 14, 30, or 60 weeks continuously or for 30 weeks plus withdrawal periods of 16 or 30 weeks. Fifteen of 76 (20%) rats initiated with DEN and promoted with TCDD for various lengths of time developed ovarian sex cord-stromal tumors of Sertoli cell type, whereas no ovarian tumors developed in 86 rats used as vehicle controls or that received DEN alone or TCDD alone. The highest tumor incidence occurred in 6 of 14 rats (43%) after 60 weeks of continuous TCDD after DEN initiation. One of six rats developed a tumor by 30 weeks of exposure. Because most effects of TCDD can be attributed to its activation of the aryl hydrocarbon receptor (AhR), the presence and localization of AhR was determined in the rat ovary and in the ovarian tumors by reverse transcription-PCR, immunohistochemistry, and in situ hybridization. AhR was localized to oocytes, granulosa and thecal cells of growing follicles, surface epithelial cells, and epithelial cells lining single tubules in ovaries from adult control Sprague Dawley rats. Neoplastic cells in the ovarian tumors were also positive for both AhR message and protein. These results indicate that the ability of TCDD to cause ovarian tumors is dependent on initiation, length of promotion, and age of the animal when exposed and evaluated. The tumor type induced by TCDD in this experimental system is the same histological subtype as that reported from an early study of youngsters exposed during an industrial accident in Seveso, Italy.

Lectin binding sites in normal rat ovary and ENU-induced Sertoli cell tumors of the ovaries.

A panel of seven fluorescein isothiocyanate (FITC) labeled lectins were used to study the distribution of specific binding sites in histologic sections of rat ovaries and ENU-induced Sertoli cell tumors (SCT) of the ovaries. Ten SCT and 5 normal ovaries derived from Berlin Druckey IV (BD-IV) rats were examined by FITC lectins. The tissues examined were fixed in 10% buffered formalin and embedded in paraffin blocks. In normal ovaries, lectin binding sites were more uniform, ordered and consistent than in ovarian SCT where some lectin staining appeared disorderly inconsistent and varied with the degree of tumor differentiation. Two lectins, (from Triticum vulgaris [WGA] and Arachis hypogaea [PNA], uniformly stained the apices of the ovarian surface epithelium and subadjacent tunica vaginalis. The ovarian stroma, oocyte nucleus, follicular and granulosa-theca cells, stained uniformly strong with succinated Con A (from Con-canavalia ensiformis). Three lectins (from Triticum vulgaris, Ulex europeaus [UEA-1] and Arachis hypogeae) accentuated the basal lamina in the SCT and normal ovarian follicles. The zona pellucida was strongly labeled with lectin derived from Triticum vulgaris, Ricinus communis (RCA) and moderately with lectin derived from Arachis hypogeae. The oviduct ampulla exhibited an intracytoplasmic strong vesicular labeling with lectins derived from Triticum vulgare, Dolichos biflorus (DBA), Glycin max (Soybean-SBA) and Arachis hypogeae. The SCT cells showed an inconsistent, irregular labeling pattern with lectins derived from Ulex europaeus, Dolichos biflorus and Soybean mostly as a coarse granular cytoplasmic labeling. Neuraminidase digestion enhanced lectin staining with PNA in normal ovary and in SCT. This data provided at list of lectin markers for distinct components of the BD-IV rat ovary and ovarian SCT.

In vitro malignant transformation of in vivo ENU-induced rat ovarian Sertoli cell tumor (adenoma).

An N-ethyl-N-nitrosourea-induced rat ovarian Sertoli cell tumor was grown in tissue culture in Dulbecco's modified Eagle's medium (DMEM) supplemented with 25% horse serum (HS) and a hormone combination of 20 ng/ml each of hydrocortisone, insulin, and prolactin. This tissue culture derived from a nonsteroid hormone-producing tumor. Cytofluorometry and karyotyping of the nonhormone-producing tumor cell line (SCTL-1) revealed a diploid pattern for the early passage (P1), which became hyperdiploid (P10), and then aneuploid (P20). These cells had an epitheloid pattern, grew in a monolayer at early passages. After P10 the cells were transplanted into newborn rats and nude mice and resulted in high incidences of tumors (up to 100%). The cell line (SCTL-1) continued to grow in DMEM, 10% HS, and no hormone supplementation after P10. This study revealed that a benign rat ovarian Sertoli cell tumor after multiple passages in vitro underwent sequential genotypic and phenotypic changes and became highly malignant.

Experimental induction of ovarian Sertoli cell tumors in rats by N-nitrosoureas.

Spontaneous ovarian tumors are very rare in ACI, Wistar, F344 and Donryu rats; the few neoplasms found are of the granulosa/theca cell type. Ovarian tumors were also rare in these strains of rats when given high doses of N-alkyl-N-nitrosoureas continuously in the drinking water for their life-span; however, relatively high incidences of Sertoli cell tumors or Sertoli cell tumors mixed with granulosa cell tumors were induced in Donryu rats after administration of either a 400 ppm N-ethyl-N-nitrosourea solution in the drinking water for 4 weeks or as a single dose of 200 mg N-propyl-N-nitrosourea per kg body weight by stomach tube. Typical Sertoli cell tumors consisted of solid areas showing tubular formation. The tubules were lined by tall, columnar cells, with abundant, faintly eosinophilic, often vacuolated cytoplasm, and basally oriented, round nuclei, resembling seminiferous tubules in the testes. In some cases, Sertoli cell tumor elements were found mixed with areas of granulosa cells. The induction of ovarian Sertoli cell tumors in Donryu rats by low doses of nitrosoureas may provide a useful model for these tumors in man.

Induction of Sertoli cell tumors in the rat ovary by N-alkyl-N-nitrosoureas.

Relatively high incidences of Sertoli cell tumors of the ovary were induced in Donryu rats given a 400 ppm N-ethyl-N-nitrosourea solution as drinking water for 4 weeks or a single dose of 200 mg/kg N-propyl-N-nitrosourea by stomach tube. Typical Sertoli cell tumors were composed of solid areas showing tubular formation. Tubules were lined by tall, columnar cells having abundant, faintly eosinophilic, often vacuolated cytoplasm, and basally oriented round nuclei. In some cases, Sertoli cell tumors were found to be mixed with granulosa cell tumors.

Testicular (Sertoli's cell)-like tumors of the ovary induced by N-ethyl-N-nitrosourea (ENU) in rats.

N-ethyl-N-nitrosourea (ENU) administered intraperitoneally or transplacentally to Sprague-Dawley (CD) and BD-IV (Berlin Druckrey IV) rats increased the incidence (26.6%) of an uncommon ovarian tumor with testicular characteristics compared either to controls (3.0%) or rats administered diethylnitrosamine (3.3%). The induced tumors were composed of tubular structures that resembled seminiferous tubules lined by Sertoli's-like cells. The abundant electron-lucent cytoplasm of the tumor cells contained polyribosomes, lipid bodies, and mitochondria but few additional organelles. Sertoli's cell-like tumors appeared to develop from the ovarian stroma in the hilar region of the ovary. They usually were benign and resulted in unilateral enlargement of the ovary. The mean serum concentrations of testosterone, estrone, and estradiol in selected rats with ovarian tumors were elevated above mean serum values in controls. There was not a consistent direct correlation between tumor diameter and circulating hormone level. Ethyl nitrosourea-induced ovarian tumors composed of testicular (Sertoli's-like) cells will provide a reproducible animal model to investigate the histogenesis and hormone secreting properties of this unique gonadal neoplasm.