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.