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The 17beta-hydroxysteroid dehydrogenase (17betaHSD) enzyme system governs important redox reactions at the C17 position of steroid hormones. Different 17betaHSD types (no. 1-4) have been identified to date in peripheral human tissues, such as placenta, testis, and breast. However, there is little information on their expression and activity in either normal or malignant prostate. In the present work, we have inspected pathways of 17beta-oxidation of either androgen or estrogen in human prostate cancer cells (LNCaP, DU145, and PC3) in relation to the expression of messenger RNAs (mRNAs) for 17betaHSD types 1-4. These cell systems feature distinct steroid receptor status and response to hormones. We report here that high expression levels of 17betaHSD4 were consistently observed in all three cell lines, whereas even greater amounts of 17betaHSD2 mRNA were detected solely in PC3 cells. Neither 17betaHSD1 nor 17betaHSD3 mRNAs could be detected in any cell line. From a metabolic standpoint, intact cell analysis showed a much lower extent of 17beta-oxidation of both androgen [testosterone (T)] and estrogen [estradiol (E2)] in LNCaP and DU145 cells compared to PC3 cells, where a greater precursor degradation and higher formation rates of oxidized derivatives (respectively, androstenedione and estrone) were observed. Using subcellular fractionation, we have been able to differentiate among 17betaHSD types 1-4 on the basis of their distinct substrate specificities and subcellular localization. This latter approach gave rise to equivalent results. PC3 cells, in fact, displayed a high level of microsomal activity with a low E2/T activity ratio and approximately equal apparent Km values for E2 and T, suggesting the presence of 17betaHSD2. Dehydrogenase specific activity with both E2 and T was also detected, although at lower levels, in LNCaP and DU145 cells. No evidence for reductase activity could be obtained in either the soluble or microsomal fraction of any cell line. As comparable expression levels of 17betaHSD4 were seen in the three cell lines, 17betaHSD2 is a likely candidate to account for the predominant oxidative activity in PC3 cells, whereas 17betaHSD4 may account for the lower extent of E2 oxidation seen in both LNCaP and DU145 cells. This is the first report on the expression of four different 17betaHSD types in human prostate cancer cells. It ought to be emphasized that for the first time, analysis of different 17betaHSD activities in either intact or fractionated cells harmonizes with the expression of relevant mRNAs species.

Estriol-3-sulfate (E3S) is present in human breast cyst fluid (BCF) in median levels of 8.7-10.4 nmol/L, yet is barely detectable in the serum (less than 0.034 nmol/L). The source of this huge concentration of E3S is unknown. It may accumulate from blood by active transport or be synthesized and concentrated within the cyst. Since estrone sulfate (E1S) and its possible precursor, dehydroepiandrosterone sulfate (DHEAS) are elevated in BCF, E3S may originate via 16 alpha-hydroxylation of E1S. The present study examined the correlations between the levels of DHEAS and E1S with those of E3S in BCF. The sodium and potassium ions were also quantified and related to the steroid concentrations. By linear regression analysis of log-normalized data there was a highly significant correlation between the concentrations of E1S and E3S (n = 355, r = 0.690, P less than 0.001) and between DHEAS and E3S (n = 361, r = 0.577, P less than 0.001). The BCF were classified according to their K/Na ion ratios: type 1, greater than 1.0, type II, less than 0.25, and type III, 0.25-1.0. By Student's t test, the concentrations of E3S differed between each BCF Type (P less than 0.002). This was also true for E1S and DHEAS. Type 1 cysts were associated with the highest estrogen sulfate levels and type II with the lowest levels. The possible physiological importance of this observation resides in reports that the BCF type expressing the highest steroid concentrations has been related to an aporcine-like epithelial lining of the cyst wall and a somewhat higher risk for developing breast cancer. The results suggest that E3S in BCF may originate from E1S, but alternate mechanisms are not precluded.