Progesterone metabolism in adenocarcinoma of the endometrium

Important roles of the AKR1C2 and SRD5A1 enzymes in progesterone metabolism in endometrial cancer model cell lines

Endometrial cancer is the most frequently diagnosed gynecological malignancy. It is associated with prolonged exposure to estrogens that is unopposed by progesterone, whereby enhanced metabolism of progesterone may decrease its protective effects, as it can deprive progesterone receptors of their active ligand. Furthermore, the 5α-pregnane metabolites formed can stimulate proliferation and may thus contribute to carcinogenesis. The aims of our study were to: (1) identify and quantify progesterone metabolites formed in the HEC-1A and Ishikawa model cell lines of endometrial cancer; and (2) pinpoint the enzymes involved in progesterone metabolism, and delineate their roles. Progesterone metabolism studies combined with liquid chromatography-tandem mass spectrometry enabled identification and quantification of the metabolites formed in these cells. Further quantitative PCR analysis and small-interfering-RNA-mediated gene silencing identified individual progesterone metabolizing enzymes and their relevant roles. In Ishikawa and HEC-1A cells, progesterone was metabolized mainly to 20α-hydroxy-pregn-4-ene-3-one, 20α-hydroxy-5α-pregnane-3-one, and 5α-pregnane-3α/β,20α-diol. The major difference between these cell lines was rate of progesterone metabolism, which was faster in HEC-1A cells. In the Ishikawa and HEC-1A cells, expression of AKR1C2 was 110-fold and 6800-fold greater, respectively, than expression of AKR1C1, which suggests that 20-ketosteroid reduction of 5α-pregnanes and 4-pregnenes is catalyzed mainly by AKR1C2. AKR1C1/AKR1C2 gene silencing showed decreased progesterone metabolism in both cell lines, thus further supporting the significant role of AKR1C2. SRD5A1 was also expressed in these cells, and its silencing confirmed that 5α-reduction is catalyzed by 5α-reductase type 1. Silencing of SRD5A1 also had the most pronounced effects, with decreased rate of progesterone metabolism, and consequently higher concentrations of unmetabolized progesterone. Our data confirm that in model cell lines of endometrial cancer, AKR1C2 and SRD5A1 have crucial roles in progesterone metabolism, and may represent novel targets for treatment.

Metabolism and effects of progesterone in the human endometrial adenocarcinoma cell line HEC-1

Human endometrial adenocarcinoma cells (HEC-1 line) were incubated with 14C-progesterone. Four major labeled metabolites, 3 beta-hydroxy 5 alpha-pregnan-20-one, 5 alpha-pregnane-3 beta, 20 alpha-diol, 20 alpha-hydroxy-4-pregnen-3-one and 5 alpha-pregnane-3, 20-dione were separated by thin layer chromatography, further purified by high pressure liquid chromatography, and finally identified by addition of carriers and crystallization to constant specific activity. Among these metabolites, 5 alpha-pregnane-3 beta, 20 alpha-diol seems characteristic of this cell line since its formation from labeled progesterone was not detected in normal endometrium or in 2 specimens of endometrial adenocarcinoma. The growth of HEC cells was unaffected by either progesterone or medroxyprogesterone acetate, a slowly metabolized progestin, at about 10(-6) M levels but was inhibited by about 10(-5) M concentrations of these compounds.

Progesterone binding by human endometrial tissue during the proliferative and secretory phases of the menstrual cycle and by hyperplastic and carcinomatous endometrium

Cytosol receptors for progesterone were assayed in human endometrial tissue during the proliferative and secretory phases of the menstrual cycle and in the hyperplastic and carcinomatous endometrium. The assays were performed utilizing a technique involving prior treatment of the cytosol extract with dextran-coated charcoal to remove endogenous progesterone. The results showed that the progesterone receptor activity was higher during the later proliferative and early secretory phases of the menstrual cycle. Hyperplastic and carcinomatous endometrium also contained specific cytosol receptor for progesterone, and the binding activity of the hyperplastic endometria and endometrial polyps was comparable to that found during the later proliferative phase of the menstrual cycle. No apparent correlation between the progesterone receptor level and the morphologic degree of differentiation in Grades 1 and 2 adenocarcinomas of the endometrium was observed.

Effect of progesterone and estradiol-17beta on nucleic acid synthesis in vitro in carcinoma of the endometrium

Nucleic acid synthesis was studied in 26 tumor specimens, during a one-hour in vitro incubation with the addition of progesterone and estradiol-17beta. On the response scale used, deoxyribonucleic acid and ribonucleic acid synthesis decreased linearly as the logarithmic concentration of either hormone increased. Inhibition of nucleic acid synthesis was highly significant (P less than 0.001) at 80 microgram per milliliter of progesterone and at 40 microgram per milliliter of estradiol. No evidence of synergism was found when the two hormones were combined at these concentrations. In Grade I and II tumors, the effect when both hormones were combined approximated the sum of effects of the individual hormones. In Grade III tumors, little difference was seen between treatment groups.