Expression Of SRD5A2 Research Articles

Increased expression of androgen receptor (AR) and enzymes involved in androgen synthesis in metastatic prostate cancer: Targets for novel personalized therapies

5002 Background: Androgen receptor (AR) signaling remains active in castration-resistant prostate cancer (CRPC) despite castrate levels of circulating androgens. This is indicated by continuous expression of androgen-responsive genes and is due to mechanisms that include: increased AR expression; AR mutations allowing promiscuous activation by alternative ligands; and increased intratumoral androgen levels, resulting from in situ steroidogenesis. Methods: Gene expression profiles of 30 normal prostate tissue samples, 131 primary prostate carcinomas (PCas) and 16 metastatic PCas, generated using Affymetrix Exon arrays, were interrogated for levels of 40 mRNAs encoding AR, SHBG, 28 enzymes involved in androgen synthesis and 10 enzymes involved in androgen inactivation. For individual tumors, a transcript was considered to be overexpressed or underexpressed when its levels were >2 SDs higher or lower, respectively, than its average levels in normal tissue. Results: Metastatic PCas expressed higher average transcript levels for AR and several steroidogenic enzymes, including SRD5A1 and SRD5A3, than primary PCas and normal prostate tissue. Expression of SRD5A2, CYP3A4, CYP3A5, and CYP3A7 mRNAs was decreased both in primary and metastatic tumors compared to normal prostate tissue. In analysis involving AR and 28 steroidogenic transcripts in individual tumors, all (16/16) metastatic PCas overexpressed at least one transcript (range: 2–14, median: 5 transcripts) compared to normal tissue, while 100/131 (76%) primary PCas overexpressed at least one transcript (range: 2–16, median: 2). Conclusions: Metastatic PCas overexpress AR and several steroidogenic enzymes, while they express lower levels of the androgen-inactivating enzymes CYP3A4, CYP3A5, and CYP3A7. These data highlight the role of AR and the androgen synthetic pathway as a therapeutic target in CRPC. Novel antiandrogens (MDV3100) and CYP17 inhibitors (abiraterone) are already in clinical trials in CRPC. Overexpression of AR or steroidogenic enzymes may serve as a biomarker (e.g. by detection via RT-PCR in circulating tumor cells) to predict for sensitivity to these agents and guide patient selection for participation in clinical trials. No significant financial relationships to disclose.

Bioconversion of norethisterone, a progesterone receptor agonist into estrogen receptor agonists in osteoblastic cells

A number of clinical studies have demonstrated that norethisterone (NET), a potent synthetic progestin, restores postmenopausal bone loss, although its mode of action on bone cells is not fully understood, while the effect of naturally occurring progesterone in bone has remained controversial. A recent report claims that the potent effects of NET on osteoblastic cell proliferation and differentiation, mimicking the action of estrogens, are mediated by non-phenolic NET derivatives. To determine whether osteoblasts possess the enzymes required to bioconvert a progesterone receptor (PR) agonist into A-ring reduced metabolites with affinity to bind estrogen receptor (ER), we studied the in vitro metabolism of [(3)H]-labeled NET in cultured neonatal rat osteoblasts and the interaction of its metabolic conversion products with cytosolic -osteoblast ER, employing a competition analysis. Results indicated that NET was extensively bioconverted (36.4%) to 5 alpha-reduced metabolites, including 5 alpha-dihydro NET, 3 alpha,5 alpha-tetrahydro NET (3 alpha,5 alpha-NET) and 3beta,5 alpha-tetrahydro NET (3beta,5 alpha-NET), demonstrating the activities of 5 alpha-steroid reductase and two enzymes of the aldo-keto reductases family. Expression of Srd5a1 in neonatal osteoblast was well demonstrated, whereas Srd5a2 expression was not detected. The most striking finding was that 3beta,5 alpha-NET and 3 alpha,5 alpha-NET were efficient competitors of [(3)H]-estradiol for osteoblast ER binding sites, exhibiting affinities similar to that of estradiol. The results support the concept that the interplay of 5 alpha-steroid reductase and aldo-keto reductases in osteoblastic cells, acting as an intracrine modulator system is capable to bioconvert a PR agonist into ER agonists, offering an explanation of the molecular mechanisms NET uses to enhance osteoblastic cell activities.

Maintenance of Intratumoral Androgens in Metastatic Prostate Cancer: A Mechanism for Castration-Resistant Tumor Growth

Therapy for advanced prostate cancer centers on suppressing systemic androgens and blocking activation of the androgen receptor (AR). Despite anorchid serum androgen levels, nearly all patients develop castration-resistant disease. We hypothesized that ongoing steroidogenesis within prostate tumors and the maintenance of intratumoral androgens may contribute to castration-resistant growth. Using mass spectrometry and quantitative reverse transcription-PCR, we evaluated androgen levels and transcripts encoding steroidogenic enzymes in benign prostate tissue, untreated primary prostate cancer, metastases from patients with castration-resistant prostate cancer, and xenografts derived from castration-resistant metastases. Testosterone levels within metastases from anorchid men [0.74 ng/g; 95% confidence interval (95% CI), 0.59-0.89] were significantly higher than levels within primary prostate cancers from untreated eugonadal men (0.23 ng/g; 95% CI, 0.03-0.44; P < 0.0001). Compared with primary prostate tumors, castration-resistant metastases displayed alterations in genes encoding steroidogenic enzymes, including up-regulated expression of FASN, CYP17A1, HSD3B1, HSD17B3, CYP19A1, and UGT2B17 and down-regulated expression of SRD5A2 (P < 0.001 for all). Prostate cancer xenografts derived from castration-resistant tumors maintained similar intratumoral androgen levels when passaged in castrate compared with eugonadal animals. Metastatic prostate cancers from anorchid men express transcripts encoding androgen-synthesizing enzymes and maintain intratumoral androgens at concentrations capable of activating AR target genes and maintaining tumor cell survival. We conclude that intracrine steroidogenesis may permit tumors to circumvent low levels of circulating androgens. Maximal therapeutic efficacy in the treatment of castration-resistant prostate cancer will require novel agents capable of inhibiting intracrine steroidogenic pathways within the prostate tumor microenvironment.

Expression of 5-a reductase type 1 (SRD5A1) in breast cancer: Association with tumor molecular subtypes and patient characteristics

22170 Background: Preliminary reports indicate that dutasteride can suppress progesterone transformation into 5-alpha pregnane by SRD5A1 in breast cancer, resulting in suppression of cell proliferation and detachment. The aim of this study was to investigate SRD5A1 expression according to the breast cancer subtypes and patient characteristics. Methods: SRD5A1 mRNA expression levels were investigated in three breast cancer data sets consisting of a 64 genes Qrt-PCR data set (STB, 168 patients) and two micro-arrays data sets (295 and 286 patients). Results: SRD5A1 mRNA expression was found to be significantly higher in estrogen receptor (ER) negative tumors including the Basal like and HER2-positive subtypes. Moreover, elevated SRD5A1 were found to be associated with pre-menopausal status of the patients, high tumor grade and poor clinical outcome. Conclusions: SRD5A1 mRNA expression was found to be associated with ER-negative breast cancer phenotypes mainly found in tumors obtained from pre-menopausal women. Possible effects of dutasteride as well as a better characterization of 5-alpha pregnane receptors should be further investigated in these subtypes of breast cancer. No significant financial relationships to disclose.

Aromatase, steroid-5-alpha-reductase type 1 and type 2 mRNA expression in gonads and in brain of Xenopus laevis during ontogeny

The key enzymes involved in the production of endogenous sex steroids are steroid-5-alpha-reductase and aromatase converting testosterone (T) into dihydrotestosterone (DHT) and into estradiol (E2), respectively. To gain more insights into the molecular mechanisms of sexual differentiation of amphibians, we determined the mRNA expression of steroid-5-alpha-reductase type1 (Srd5a1), type2 (Srd5a2) and aromatase (Aro) during ontogeny starting from the egg and ending after completion of metamorphosis in Xenopus laevis. Expression of all three enzymes was measured by means of semi-quantitative RT-PCR, determining for the first time Srd5a1 and Srd5a2 mRNA expression in amphibians. mRNA was analyzed in whole body homogenates from stage 12 to 48, while brain and gonads with kidney were studied separately from stage 48 to 66. Different ontogenetic mRNA expression patterns were observed for all genes analyzed, revealing early mRNA expression of Srd5a1 already in the egg at stage 12 whereas Srd5a2 and Aro was detected at stage 39. Sex-specific mRNA expressions of Srd5a2 and of Aro were determined in the gonads with kidney but not in brain. Srd5a2 was two-fold higher expressed in testes than in ovaries while Aro mRNA was ten-fold higher in ovaries. No gender-specific mRNA expression was observed for Srd5a1 in gonads and in brain. The ontogenetic patterns of Aro, Srd5a1 and Srd5a2 suggest that these genes are involved in sexual differentiation of gonads and brain already in early developmental stages. Especially in gonads Srd5a2 seems to be important for physiological regulation of testis development while Aro is associated with the development of ovaries.

Impaired Dihydrotestosterone Catabolism in Human Prostate Cancer: Critical Role of AKR1C2 as a Pre-Receptor Regulator of Androgen Receptor Signaling

We previously reported the selective loss of AKR1C2 and AKR1C1 in prostate cancers compared with their expression in paired benign tissues. We now report that dihydrotestosterone (DHT) levels are significantly greater in prostate cancer tumors compared with their paired benign tissues. Decreased catabolism seems to account for the increased DHT levels as expression of AKR1C2 and SRD5A2 was reduced in these tumors compared with their paired benign tissues. After 4 h of incubation with benign tissue samples, (3)H-DHT was predominantly catabolized to the 5alpha-androstane-3alpha,17beta-diol metabolite. Reduced capacity to metabolize DHT was observed in tumor samples from four of five freshly isolated pairs of tissue samples, which paralleled loss of AKR1C2 and AKR1C1 expression. LAPC-4 cells transiently transfected with AKR1C1 and AKR1C2, but not AKR1C3, were able to significantly inhibit a dose-dependent, DHT-stimulated proliferation, which was associated with a significant reduction in the concentration of DHT remaining in the media. R1881-stimulated proliferation was equivalent in all transfected cells, showing that metabolism of DHT was responsible for the inhibition of proliferation. PC-3 cells overexpressing AKR1C2 and, to a lesser extent, AKR1C1 were able to significantly inhibit DHT-dependent androgen receptor reporter activity, which was abrogated by increasing DHT levels. We speculate that selective loss of AKR1C2 in prostate cancer promotes clonal expansion of tumor cells by enhancement of androgen-dependent cellular proliferation by reducing DHT metabolism.

Expression of progesterone metabolizing enzyme genes (AKR1C1, AKR1C2, AKR1C3, SRD5A1, SRD5A2) is altered in human breast carcinoma

BackgroundRecent evidence suggests that progesterone metabolites play important roles in regulating breast cancer. Previous studies have shown that tumorous tissues have higher 5α-reductase (5αR) and lower 3α-hydroxysteroid oxidoreductase (3α-HSO) and 20α-HSO activities. The resulting higher levels of 5α-reduced progesterone metabolites such as 5α-pregnane-3,20-dione (5αP) in tumorous tissue promote cell proliferation and detachment, whereas the 4-pregnene metabolites, 4-pregnen-3α-ol-20-one (3αHP) and 4-pregnen-20α-ol-3-one (20αDHP), more prominent in normal tissue, have the opposite (anti-cancer-like) effects. The aim of this study was to determine if the differences in enzyme activities between tumorous and nontumorous breast tissues are associated with differences in progesterone metabolizing enzyme gene expression.MethodsSemi-quantitative RT-PCR was used to compare relative expression (as a ratio of 18S rRNA) of 5αR type 1 (SRD5A1), 5αR type 2 (SRD5A2), 3α-HSO type 2 (AKR1C3), 3α-HSO type 3 (AKR1C2) and 20α-HSO (AKR1C1) mRNAs in paired (tumorous and nontumorous) breast tissues from 11 patients, and unpaired tumor tissues from 17 patients and normal tissues from 10 reduction mammoplasty samples.ResultsExpression of 5αR1 and 5αR2 in 11/11 patients was higher (mean of 4.9- and 3.5-fold, respectively; p < 0.001) in the tumor as compared to the paired normal tissues. Conversely, expression of 3α-HSO2, 3α-HSO3 and 20α-HSO was higher (2.8-, 3.9- and 4.4-fold, respectively; p < 0.001) in normal than in tumor sample. The mean tumor:normal expression ratios for 5αR1 and 5αR2 were about 35–85-fold higher than the tumor:normal expression ratios for the HSOs. Similarly, in the unmatched samples, the tumor:normal ratios for 5αR were significantly higher than the ratios for the HSOs.ConclusionsThe study shows changes in progesterone metabolizing enzyme gene expression in human breast carcinoma. Expression of SRD5A1 (5αR1) and SRD5A2 (5αR2) is elevated, and expression of AKR1C1 (20α-HSO), AKR1C2 (3α-HSO3) and AKR1C3 (3α-HSO2) is reduced in tumorous as compared to normal breast tissue. The changes in progesterone metabolizing enzyme expression levels help to explain the increases in mitogen/metastasis inducing 5αP and decreases in mitogen/metastasis inhibiting 3αHP progesterone metabolites found in breast tumor tissues. Understanding what causes these changes in expression could help in designing protocols to prevent or reverse the changes in progesterone metabolism associated with breast cancer.

Regulation of HSD17B1 and SRD5A1 in Lymphocytes

We previously reported lymphocyte expression of genes encoding enzymes required for steroid metabolism; however, only 17β-HSD and 5α-reductase showed significant enzyme activity. We now investigate regulation of lymphocyte expression for genes encoding 17β-HSD and 5α-reductase. Cultured human T and B lymphoid cell lines and peripheral blood mononuclear cells were treated with known regulators of steroidogenic gene expression including forskolin, PMA, ionomycin, various steroids, interleukin (IL)-4, and IL-6. Treatment with 10 or 50 μM forskolin resulted in a 20–60% reduction of expression for HSD17B1 (encoding 17β-HSD I) in T and B lymphoid cell lines and peripheral blood mononuclear cells, although such a change was not observed in the expression of SRD5A1 (encoding 5α-reductase I). No significant changes were found when cells were treated for 24 h with various concentrations of PMA or ionomycin. Incubation with 10−9 to 10−7 M androstenedione or estradiol increased expression of HSD17B1, while testosterone decreased the expression of this gene. SRD5A1 expression was increased in the presence of 5α-DHT although no consistent changes were observed when the cells were treated with testosterone. Other steroids, including dexamethasone, progesterone, and 6-hydroxypregnanolone, produced no effects on expression of either HSD17B1 or SRD5A1. Treatment with 0.1–10 ng/ml of IL-4 or IL-6 also did not effect significant changes in gene expression. These data implicate the involvement of the cAMP–protein kinase signal transduction pathway in regulating lymphocyte expression of HSD17B1. Furthermore, it appears that lymphocyte HSD17B1 and SRD5A1 are regulated to some extent by specific steroids.