STEROIDOGENIC FACTOR-I REGULATES THE RATE OF PROLIFERATION OF NORMAL AND NEOPLASTIC RAT OVARIAN SURFACE EPITHELIAL-CELLS IN-VITRO

Steroidogenic factor-1 (SF-1) is a transcription factor that is expres sed by many cell types within the ovary and has been shown to inhibit granulosa cell proliferation. The present studies were designed to det ermine whether: 1) SF-1 is expressed by primary and transformed rat ov arian surface epithelial cells (i.e. ROSE cells); and 2) SF-1 expressi on effects the proliferation of both normal and neoplastic ROSE cells. These studies used immature, gonadotropin-primed and mature rat ovari es, as well as ROSE-179 cells from early passages (EP) and late passag es (LP), T-sv-40 transformed ROSE cells, and T-ras transformed ROSE ce lls. In situ hybridization studies demonstrated that SF-1 was detected in the surface epithelium of rat ovaries, independent of age or gonad otropin treatment. Further, Northern blot and quantitative in situ hyb ridization studies revealed that significant amounts of SF-1 messenger RNA (mRNA) were present in EP-ROSE-179 cells but not in the other cel l lines. Interestingly, EP-ROSE-179 cells proliferated at a significan tly slower rate than the other cell lines. Further, SE-1 mRNA levels w ere higher in EP-ROSE-179 cells in the G(0)/G(1) stage than in the S-, G(2)/M stage of the cell cycle. These observations suggest that a cau se and effect relationship exists between the level of SF-1 expression and cell proliferation. To test this hypothesis, LP, T-sv-40, and T-r as ROSE cells were transfected with either control vector or SF-1 expr ession vector. Forty-eight hours after transfection, SF-1 expression w as assessed by in situ hybridization, and the fold increase in cell nu mber/24 h was determined. For each cell line, about 30% of the cells w ere successfully transfected. The fold increase in the number of cells observed after transfection with the SF-1 expression vector was signi ficantly less than the increase in cell number after transfection with the control vector (P < 0.05). To confirm that; the forced expression of SF-1 prevented proliferation, LP cells were cotransfected with a g reen fluorescent protein (GFP) expression vector and either control ve ctor or SF-1 expression vector. This study demonstrated that virtually none of the GFP/SF-1-transfected cells proliferated over a 24-h perio d, whereas GFP/Control vector-transfected cells proliferated. Further, approximately 40% of the GFP/SF-1-transfected cells underwent apoptos is after 24 h of culture in serum-supplemented medium. These data demo nstrate that: 1) normal ovarian surface epithelial cells express SF-1; 2) SF-1 is also expressed by EP-ROSE-179 cells, but its expression se ems to be suppressed when the cells enter the cell cycle; 3) LP-, T-sv , and T-ras ROSE cells do not express SF-1 mRNA; and 4) the inability to express SF-1 is associated with an increase in cell proliferation. Finally, forced SF-1 expression interferes with serum-induced prolifer ation and leads to apoptosis.