Ovarian epithelial tumor growth promotion by follicle-stimulating hormone and inhibition of the effect by luteinizing hormone.

OBJECTIVES

The role of gonadotropins in ovarian epithelial cancer development is still controversial. Follicle-stimulating hormone receptor (FSHR) status in ovarian epithelial tumors (OETs) and their presumed precursor lesions has never been studied in detail. The objective of this study was to examine whether FSHR is expressed in OETs and to investigate the possible different roles of the gonadotropins in ovarian cancer development.

METHODS

Twenty ovarian epithelial inclusions (entrapments or invaginations of ovarian surface epithelium) from benign ovaries and 60 OETs including 12 cystadenomas, 18 borderline tumors, and 30 carcinomas were examined for FSHR expression by using reverse transcription polymerase chain reaction (RT-PCR), in situ hybridization (ISH), and immunohistochemistry (IHC). We also studied the mitogenic activity of FSH on two FSH and luteinizing hormone (LH) receptor-positive ovarian epithelial carcinoma cell lines (AO and 3AO) and on the modifying effect of LH on this activity. Growth-stimulating effects of the gonadotropins were tested in vitro with measurement of cell numbers, S-phase by flow cytometry, and changes in the cellular proliferative marker Ki-67.

RESULTS

Positive FSHR mRNA expression by RT-PCR (the most sensitive method) was found in 100% of epithelial inclusions, 100% of cystadenomas, 94% of borderline tumors, and 60% of carcinomas. There was a nonstatistically significant trend of decreasing positivity with increasing carcinoma grade. ISH and IHC gave similar, but somewhat less sensitive, results. A dose-response effect was seen with FSH, with a 1.6-fold increase in cell numbers with a maximally stimulating FSH concentration of 40 IU/L for a period of 48 h. These proliferative cellular effects were not observed when the cells were stimulated by LH in the range 1 to 100 IU/L. Most significantly, the growth stimulating effects of FSH could be blocked by the simultaneous administration of LH.

CONCLUSIONS

FSHR is present in the majority of ovarian epithelial inclusions and OETs. The steady decline of FSHR expression from benign cystadenoma to borderline tumor to carcinoma suggests that FSH may be needed in early ovarian cancer development. Gonadotropins, FSH and LH, may have different roles in ovarian cancer cell proliferation. FSH, not LH, may be an important ovarian epithelial cell growth-promoting factor. The "opposing" effect of LH on FSH stimulation may explain why high FSH levels at postmenopausal ages are not associated with great increases in ovarian cancer risk.