In SituSteroid Sulfatase Activity in Human Epithelial Carcinoma Cells of Vaginal, Ovarian, and Endometrial Origin*

The enzymatic hydrolysis of estrone sulfate and dehydroepiandrosterone sulfate to estrone and dehydroisoandrosterone, respectively, was studied in cells that were derived from four different malignant tumors of the lower reproductive tract of women, viz. a squamous cell vaginal carcinoma, an ovarian carcinoma, and two endometrial adenocarcinomas. These cells had the capacity to hydrolyze both steroid sulfoconjugates. Estrone sulfate was more efficient as a substrate than dehydroepiandrosterone sulfate, since the amount of product formed from estrone sulfate was approximately 3-fold greater than that formed from dehydroepiandrosterone sulfate. Some kinetic parameters of steroid sulfatase were determined in the four cell types and were found to be very similar, as were the rates of hydrolysis. Sulfatase activity was linear with incubation time for at least 2 h and with cell number up to 3.2 X 10(6) cells/mL. The apparent pH optimum of steroid sulfatase, determined by the use of cell sonicates and estrone sulfate as the substrate, was between 6.0 and 7.5. The apparent Km values of steroid sulfatase for estrone sulfate in both squamous vaginal carcinoma cells and ovarian carcinoma cells were both 5 microM, and those for dehydroepiandrosterone sulfate in squamous vaginal carcinoma cells and endometrial adenocarcinoma cells were 6 and 4 microM, respectively. The optimal temperature of steroid sulfatase in squamous vaginal carcinoma cells was 50 C; at this temperature, enzymatic activity was more than twice that at 37 C. The steroid sulfatase pathway that is operative in carcinoma cells in vitro to produce free steroids from steroid sulfate precursors also may serve to produce free steroids in vaginal, endometrial, and ovarian carcinomas in vivo and, perhaps, maintain and stimulate tumor growth.