Reductive 17beta-hydroxysteroid dehydrogenases which synthesize estradiol and inactivate dihydrotestosterone constitute major and concerted players in ER+ breast cancer cells

Synthesis and Systematic Investigation of Lepidiline A and Its Gold(I), Silver(I), and Copper(I) Complexes Using In Vitro Cancer Models and Multipotent Stem Cells

The imidazole alkaloid lepidiline A from the root of Lepidium meyenii has a moderate to low in vitro anticancer effect. Our aim was to extend cytotoxicity investigations against a panel of cancer cells, including multidrug-resistant cancer cells, and multipotent stem cells. Lepidiline A is a N-heterocyclic carbene precursor, therefore a suitable ligand source for metal complexes. Thus, we synthesized lepidiline A and its copper(I), gold(I), and silver(I) complexes and tested them against ovarian, gastrointestinal, breast, and uterine cancer cells and bone marrow-derived and adipose-derived mesenchymal stem cells. Lepidiline A and its copper complex demonstrated moderate cytotoxicity, while silver and gold complexes exhibited significantly enhanced and consistent cytotoxicity against both cancer and stem cell lines. ABCB1 in the multidrug-resistant uterine sarcoma line conferred significant resistance against lepidiline A and the copper-lepidiline A complex, but not against the silver and gold complexes. Our results indicate that only the copper complex induced a significant and universal increase in the production of reactive oxygen species within cells. In summary, binding of metal ions to lepidiline A results in enhanced cytotoxicity with the nature of the metal ion playing a critical role in determining its properties.

The multi-specific human 17 beta-hydroxysteroid dehydrogenase type 7: Non-competitive inhibitors can target different catalyses to facilitate breast cancer treatment

Human 17β-hydroxysteroid dehydrogenase type 7 (17β-HSD7), a special multifunctional enzyme, activates the estrogen estrone while inactivating the potent androgen dihydrotestosterone. Thus, this enzyme has become an ideal target for hormone-dependent breast cancer treatment, as its inhibition leads to estradiol reduction and dihydrotestosterone restoration. However, a particular concern has arisen related to an additional role in cholesterol biosynthesis, as inhibition of the enzyme may lead to undesirable side effects. Our findings demonstrate that the available enzyme inhibitors are non-competitive. Among these, many such as INH81, are specific toward sex-hormone conversion, whereas others represented by 4-bromo-ethynylestradiol, are more specific for zymosterone reduction occurring during cholesterol biosynthesis. The binding of non-competitive inhibitors does not affect the substrate binding on the enzyme. This is the first demonstration of non-competitive inhibitors acting selectively on different catalyses, thereby facilitating inhibitor uses for breast cancer treatment. We aim to quickly communicate the novel results.

Molecular docking, synthesis and anticancer activity of thiosemicarbazone derivatives against MCF-7 human breast cancer cell line

BACKGROUND

The aim of this study was to synthesize and evaluate anticancer activity of 2-hydroxy benzaldehyde and 4-hydroxy benzaldehyde thiosemicarbazone (2-HBTSc and 4-HBTSc) against MCF-7 breast cancer cell line.

MATERIALS AND METHODS

The ligands were prepared and characterized by UV vis, IR and NMR. MTT assay was used to assess viability of cells. RNA isolation, extraction and cDNA synthesis were done. Then all groups were subjected to RT-qPCR using Gene expression specific primers. Also, western blot protein expression and molecular docking were done. Two-way ANOVA with Tukey post-hoc test was employed to test the significance using GraphPad Prism.

RESULTS

The IC₅₀ values were 3.36μg/ml and 3.60μg/ml for 2-HBTSc and 4-HBTSc treated MCF-7 tumor cells respectively. Tumor cell growth inhibition ranged from 38 to 49.27% in 4-HBTSc treated cells, and 19 to 25% in 2-HBTSc treated cells with increase in doses 5 μg/ml to 20 μg/ml. The protein and gene expression result showed a significant upregulation in tumor suppressor and apoptosis inducing genes while, oncogene activity was significantly downregulated. Specifically, BRCA2 and pRB gene showed the highest expression in 4-HBTSc and 2-HBTSc treated cells respectively. Conversely, RAS oncogene was downregulated significantly. Docking result showed that both 2-HBTSc and 4-HBTSc have the potential to inhibit Estrogen Receptor Alpha Ligand Binding Domain, Human 17-Beta-hydroxysteroid dehydrogenase type 1 mutant protein and Human Topoisomerase II alpha that are expressed more during Breast Cancer.

CONCLUSION

The findings of this study imply that the test compound has potential for further study.

Association between miR-27a rs895819 polymorphism and breast cancer susceptibility: Evidence based on 6118 cases and 7042 controls

BACKGROUND

Polymorphism in miR-27a rs895819 has been associated with breast cancer (BC) risk, but studies have reported inconsistent results. This meta-analysis investigated the possible association between miR-27a rs895819 polymorphism and BC risk.

METHODS

PubMed, EMBASE, Google Scholar, and the Chinese National Knowledge Infrastructure (CNKI) databases were systematically searched to identify relevant studies in English and Chinese. Meta-analyses were performed to examine the association between miR-27a rs895819 and BC susceptibility.

RESULTS

A total of 16 case-control studies involving 6118 cases and 7042 controls were included. Analysis using five genetic models suggested no significant association between miR-27a rs895819 polymorphism and BC risk in the total population, or specifically in Asian or Chinese subpopulations. In the Caucasian subpopulation, however, the G-allele and AG genotype at rs895819 were significantly associated with decreased BC risk according to the allelic model (OR 0.90, 95% CI 0.84-0.97, P = .004) and heterozygous model (OR 0.89, 95% CI 0.81-089, P = .02), while the wild-type AA genotype was significantly associated with increased BC risk according to the dominant model (OR 1.13, 95% CI 1.03-1.24, P = .007).

CONCLUSION

These results indicate that among Caucasians, the wild-type AA genotype at rs895819 may confer increased susceptibility to BC, while the G-allele and AG genotype may be protective factors. These conclusions should be verified in large, well-designed studies.

Synthesis of New Thioureas Derivatives and Evaluation of Their Efficacy as Proliferation Inhibitors in MCF-7 Breast Cancer Cells by Using 99mTc-MIBI Radiotracer

BACKGROUND AND OBJECTIVES

Anti-tumor activity of some thioureas derivatives is well documented in literature and received considerable attention. The present study aims to synthesize and characterize some novel thioureas and carbonylthioureas as anti-tumor agents for MCF-7 breast cancer cells in vitro and in vivo.

MATERIALS AND METHODS

Several 1-allyl-3-(substituted phenyl), N,N'-(phenylene) bis(3- allyldithithiourea) and 1-cyclopropanecarbonyl-3-(substituted phenyl)-thioureas derivatives were synthesized and confirmed by FT-IR spectroscopy, NMR and 13C-NMR. Anti-tumor activity of these compounds was determined by various in vitro and in vivo assays including; MTT, tumor volume measurement as well as,99mTc-MIBI tumor uptake in MCF-7 tumor bearing nude mice.

RESULTS

Among all of the synthesized compounds, some thioureas derivatives [3i] and [4b] at 100 nM concentration exhibited significant inhibitory effects on the proliferation of MCF-7 cell in vitro. However, this inhibition was not observed in HUVEC human endothelial normal cells. In vivo anti-tumor effects of the synthesized compounds on MCF-7 xenograft mouse models demonstrated a reduction in the tumor volume for various concentrations between 2 to 10 mg/kg after 21 days. These effects were comparable with Tamoxifen as standard anti-estrogen drug. According to the 99mTc-MIBI biodistribution result, treatment of MCF-7 bearing nude mice with both [3i] and [4b] compounds at the maximum concentration (10 mg/kg) can lead to a significant decrease of 99mTc- MIBI tumor uptake.

CONCLUSION

Compounds [3i] and [4b] suppressed the growth of MCF-7 cells in the xenograft nude mice at the doses that were well-tolerated. Our study suggests that these new compounds with their significant anti-tumor effects, may serve as useful candidates for breast cancer therapy.

Steroid enzyme and receptor expression and regulations in breast tumor samples - A statistical evaluation of public data

In spite of the significant progress of estrogen-dependent breast cancer (BC) treatment, aromatase inhibitor resistance is a major problem limiting the clinical benefit of this frontier endocrine-therapy. The aim of this study was to determine the differential expression of steroid-converting enzymes between tumor and adjacent normal tissues, as well as their correlation in modulating intratumoral steroid-hormone levels in post-menopausal estrogen-dependent BC. RNA sequencing dataset (n = 1097) of The-Cancer-Genome-Atlas (Breast Invasive Carcinoma) retrieved through the data portal of Genomic Data Commons was used for differential expressions and expression correlation analyses by Mann-Whitney U and Spearman's rank test, respectively. The results showed significant up-regulation of 17β-HSD7 (2.50-fold, p < 0.0001) in BC, supporting its effect in sex-hormone control. Besides, suppression of 11β-HSD1 expression (-8.29-fold, p < 0.0001) and elevation of 11β-HSD2 expression (2.04-fold, p < 0.0001) provide a low glucocorticoid environment diminishing BC anti-proliferation. Furthermore, 3α-HSDs were down-regulated (-1.59-fold, p < 0.01; -8.18-fold, p < 0.0001; -33.96-fold, p < 0.0001; -31.85-fold, p < 0.0001 for type 1-4, respectively), while 5α-reductases were up-regulated (1.41-fold, p < 0.0001; 2.85-fold, p < 0.0001; 1.70-fold, p < 0.0001 for type 1-3, respectively) in BC, reducing cell proliferation suppressers 4-pregnenes, increasing cell proliferation stimulators 5α-pregnanes. Expression analysis indicates significant correlations between 11β-HSD1 with 3α-HSD4 (r = 0.605, p < 0.0001) and 3α-HSD3 (r = 0.537, p < 0.0001). Significant expression correlations between 3α-HSDs were also observed. Our results systematically present the regulation of steroid-converting enzymes and their roles in modulating the intratumoral steroid-hormone levels in BC with a vivid 3D-schema, supporting novel therapy targeting the reductive 17β-HSD7 and proposing a new combined therapy targeting 11β-HSD2 and 17β-HSD7.

Multiple catalytic activities of human 17β-hydroxysteroid dehydrogenase type 7 respond differently to inhibitors

Cholesterol biosynthesis is a multistep process in mammals that includes the aerobic removal of three methyl groups from the intermediate lanosterol, one from position 14 and two from position 4. During the demethylations at position 4, a 3-ketosteroid reductase catalyses the conversion of both 4-methylzymosterone and zymosterone to 4-methylzymosterol and zymosterol, respectively, restoring the alcoholic function of lanosterol, which is also maintained in cholesterol. Unlike other eukaryotes, mammals also use the same enzyme as an estrone reductase that can transform estrone (E1) into estradiol (E2). This enzyme, named 17β-hydroxysteroid dehydrogenase type 7 (HSD17B7), is therefore a multifunctional protein in mammals, and one that belongs to both the HSD17B family, which is involved in steroid-hormone metabolism, and to the family of post-squalene cholesterol biosynthesis enzymes. In the present study, a series of known inhibitors of human HSD17B7's E1-reductase activity have been assayed for potential inhibition against 3-ketosteroid reductase activity. Surprisingly, the assayed compounds lost their inhibition activity when tested in HepG2 cells that were incubated with radiolabelled acetate and against the recombinant overexpressed human enzyme incubated with 4-methylzymosterone (both radiolabelled and not). Preliminary kinetic analyses suggest a mixed or non-competitive inhibition on the E1-reductase activity, which is in agreement with Molecular Dynamics simulations. These results raise questions about the mechanism(s) of action of these possible inhibitors, the enzyme dynamic regulation and the interplay between the two activities.

Transcriptome of 17β-hydroxysteroid dehydrogenase type 2 plays both hormone-dependent and hormone-independent roles in MCF-7 breast cancer cells

Breast cancer is a major cause of cancer-related death for women in western countries. 17β-Hydroxysteroid dehydrogenases (17β-HSDs) play important roles in the last step of sex-hormone activation and the first step of sex-hormone inactivation. 17β-HSD2 is responsible for oxidizing the sex hormones. We used microarray technology to analyze the effect of 17β-HSD2 on the MCF-7 cell transcript profile after knocking down 17β-HSD2. Five hundred forty-two genes were regulated 1.5-fold or higher after treatment with 17β-HSD2 siRNA. Knocking down 17β-HSD2 interrupted nucleosome assembly. Pathway-Act-Network analysis showed that the MAPK and apoptosis signaling pathways were most regulated. In the gene-gene interaction network analysis, UGT2B15, which is involved in hormone metabolism, was the most regulated core gene. FOS, GREB1, and CXCL12 were the most regulated genes, and CXCL12 was related to tumor migration. Following 17β-HSD2 knock-down, the cell viability decreased to 75.9%. The S-phase percentage decreased by 19.4%, the Q2-phase percentage in cell apoptosis testing increased by 1.5 times, and cell migration decreased to 66.0%. These results were consistent with our gene chip analysis and indicated that 17β-HSD2 plays both hormone-dependent and hormone-independent enzymatic roles. In-depth investigations of this enzyme on the genomic level will help clarify its related molecular mechanisms.

Comparison of the roles of estrogens and androgens in breast cancer and prostate cancer

Breast cancer (BC) and prostate cancer (PC) are the second most common malignant tumors in women and men in western countries, respectively. The risks of death are 14% for BC and 9% for PC. Abnormal estrogen and androgen levels are related to carcinogenesis of the breast and prostate. Estradiol stimulates cancer development in BC. The effect of estrogen on PC is concentration-dependent, and estrogen can regulate androgen production, further affecting PC. Estrogen can also increase the risk of androgen-induced PC. Androgen has dual effects on BC via different metabolic pathways, and the role of the androgen receptor (AR) in BC also depends on cell subtype and downstream target genes. Androgen and AR can stimulate both primary PC and castration-resistant PC. Understanding the mechanisms of the effects of estrogen and androgen on BC and PC may help us to improve curative BC and PC treatment strategies.

Mutual regulations and breast cancer cell control by steroidogenic enzymes: Dual sex-hormone receptor modulation upon 17β-HSD7 inhibition

Reductive 17β-hydroxysteroid dehydrogenases (17β-HSDs) and 11β-hydroxysteroid dehydrogenase 2 (11β-HSD2) play crucial roles in respectively regulating steroids and glucocorticoids for the progression of hormone-dependent breast cancer. Most studies focused on the function and individual regulation of these enzymes. However, mutual regulation of these enzymes and the induced modulation on the estrogen and androgen receptors for breast cancer promotion are not yet clear. In this study, MCF-7 and T47D cells were treated with inhibitors of 17β-HSD1, 17β-HSD7, aromatase or steroid sulfatase (STS), then mRNA levels of 17β-HSD7, STS, 11β-HSD 2, estrogen receptors α (ERα) and androgen receptor (AR) were determined by Q-PCR. ER negative cell line MDA-MB-231 was used as a negative control. Our results demonstrate that 17β-HSD7, STS and 11β-HSD2 are all regulated by the same estrogen estradiol via ERα. When the gene of ERα (ESR1) was knocked down, there was no longer significant mutual regulation of these enzymes. Our results demonstrate that important steroidogenic enzymes transcriptionally regulated by ERα, can be mutually closely correlated. Inhibition of one of them can reduce the expression of another, thereby amplifying the role of the inhibition. Furthermore, inhibition of 17β-HSD7 increases the expression of AR gene which is considered as a marker for better prognosis in ER + breast cancer, while maintaining ERα level. Thus, our mechanistic finding provides a base for further improving the endocrine therapy of ER + breast cancer, e.g., for selecting the target steroid enzymes, and for the combined targeting of human 17β-HSD7 and ERα.

The role of 17βHSDs in breast tissue and breast cancers

The family of seventeen beta hydroxysteroid dehydrogenase enzymes has a long and diverse history in breast and breast cancer research. Given the known dependence of the breast on steroid signalling and intracrine steroid metabolism these enzymes are considered to be essential local fine tuners of overall steroid balance in the tissue. This review will cover the current state of knowledge regarding the expression, clinical effect and biological regulation of enzymes in both cancerous and normal states. In addition we will also cover the current state of knowledge regarding 17βHSD actions in the often neglected adipose and stromal components of tumours.

Role of hydroxysteroid (17beta) dehydrogenase type 1 in reproductive tissues and hormone-dependent diseases

Abnormal synthesis and metabolism of sex steroids is involved in the pathogenesis of various human diseases, such as endometriosis and cancers arising from the breast and uterus. Steroid biosynthesis is a multistep enzymatic process proceeding from cholesterol to highly active sex steroids via different intermediates. Human Hydroxysteroid (17beta) dehydrogenase 1 (HSD17B1) enzyme shows a high capacity to produce the highly active estrogen, estradiol, from a precursor hormone, estrone. However, the enzyme may also play a role in other steps of the steroid biosynthesis pathway. In this article, we have reviewed the literature on HSD17B1, and summarize the role of the enzyme in hormone-dependent diseases in women as evidenced by preclinical studies.

siRNA-based breast cancer therapy by suppressing 17β-hydroxysteroid dehydrogenase type 1 in an optimized xenograft cell and molecular biology model in vivo

Purpose

Hormone-dependent breast cancer is the most common form of breast cancer, and inhibiting 17β-HSD1 can play an attractive role in decreasing estrogen and cancer cell proliferation. However, the majority of existing inhibitors have been developed from estrogens and inevitably possess residual estrogenicity. siRNA knockdown provides a highly specific way to block a targeted enzyme, being especially useful to avoid estrogenicity. Application of 17β-HSD1-siRNA in vivo is limited by the establishment of an animal model, as well as the potential nuclease activity in vivo. We tried to reveal the in vivo potential of 17β-HSD1-siRNA-based breast cancer therapy.

Materials and methods

To establish a competent animal model, daily subcutaneous injection of an estrone micellar aqueous solution was adopted to provide the substrate for estradiol biosynthesis. The effects of three different doses of estrone (0.1, 0.5, and 2.5 µg/kg/day) on tumor growth in T47D-17β-HSD1-inoculated group were investigated and compared with the animals inoculated with wild type T47D cells. To solve in vivo delivery problem of siRNA, “17β-HSD1-siRNA/LPD”, a PEGylated and modified liposome–polycation–DNA nanoparticle containing 17β-HSD1-siRNA was prepared by the thin film hydration method and postinsertion technology. Finally, “17β-HSD1-siRNA/LPD” was tested in the optimized model. Tumor growth and 17β-HSD1 expression were assessed.

Results

Comparison with the untreated group revealed significant suppression of tumor growth in “17β-HSD1-siRNA/LPD”-treated group when HSD17B1 gene expression was knocked down.

Conclusion

These findings showed promising in vivo assessments of 17β-HSD1-siRNA candidates. This is the first report of an in vivo application of siRNA for steroid-converting enzymes in a nude mouse model.

The dual sex hormone specificity for human reductive 17β-hydroxysteroid dehydrogenase type 7: Synergistic function in estrogen and androgen control

Human 17β-hydroxysteroid dehydrogenase (17β-HSD) type 1 and 7 catalyze the final step of estrogen activation and the first step in androgen inactivation. It has been shown in breast cancer cells that DHT has a suppression effect on cell proliferation, counteracting the estrogen growth effect. However, the exact kinetic function of 17β-HSD7 in steroidogenesis was not determined. Here we report the steady-state kinetics and binding study for 17β-HSD7 with estrone or DHT as substrates and NADPH as cofactor. 17β-HSD7 has been overexpressed in E. coli and purified. For both substrates, kinetics of 17β-HSD7 demonstrates positive cooperativity. The K_0.5 value is 5.2 ± 0.4 μM and 14.4 ± 0.8 μM and the k_cat is 0.0063 ± 0.0003 s^-1 and 0.0153 ± 0.0007 s^-1 for the reduction of E1 and DHT, respectively. The binding study shows a similar affinity with a dissociation constant of 5.2 ± 0.5 μM and 11 ± 1 μM for E1 and DHT, respectively. Our kinetic and binding results reveal a positive cooperativity for 17β-HSD7 to both the E1 and DHT with a similar affinity, while 17β-HSD1 demonstrated a significantly higher affinity toward E1 than DHT, but with a strong E1 substrate inhibition. These results strongly support that the inhibition of 17β-HSD7 constitutes the basis of breast cancer cell proliferation decreasing that led to the shrinkage of xenograft ER + breast tumor mice model.

Steroid sulfatase inhibition success and limitation in breast cancer clinical assays: An underlying mechanism

Steroid sulfatase is detectable in most hormone-dependent breast cancers. STX64, an STS inhibitor, induced tumor reduction in animal assay. Despite success in phase І clinical trial, the results of phase II trial were not that significant. Breast Cancer epithelial cells (MCF-7 and T47D) were treated with two STS inhibitors (STX64 and EM1913). Cell proliferation, cell cycle, and the concentrations of estradiol and 5α-dihydrotestosterone were measured to determine the endocrinological mechanism of sulfatase inhibition. Comparisons were made with inhibitions of reductive 17β-hydroxysteroid dehydrogenases (17β-HSDs). Proliferation studies showed that DNA synthesis in cancer cells was modestly decreased (approximately 20%), accompanied by an up to 6.5% in cells in the G0/G1 phase and cyclin D1 expression reduction. The concentrations of estradiol and 5α-dihydrotestosterone were decreased by 26% and 3% respectively. However, supplementation of 5α-dihydrotestosterone produced a significant increase (approximately 35.6%) in the anti-proliferative effect of sulfatase inhibition. This study has clarified sex-hormone control by sulfatase in BC, suggesting that the different roles of estradiol and 5α-dihydrotestosterone can lead to a reduction in the effect of sulfatase inhibition when compared with 17β-HSD7 inhibition. This suggests that combined treatment of sulfatase inhibitors with 17β-HSD inhibitors such as the type7 inhibitor could hold promise for hormone-dependent breast cancer.

SULFATION PATHWAYS: Contribution of intracrine oestrogens to the aetiology of endometriosis

Endometriosis is an incurable hormone-dependent inflammatory disease that causes chronic pelvic pain and infertility characterized by implantation and growth of endometrial tissue outside the uterine cavity. Symptoms have a major impact on the quality of life of patients resulting in socioeconomic, physical and psychological burdens. Although the immune system and environmental factors may play a role in the aetiology of endometriosis, oestrogen dependency is still considered a hallmark of the disorder. The impact of oestrogens such as oestrone and particularly, oestradiol, on the endometrium or endometriotic lesions may be mediated by steroids originating from ovarian steroidogenesis or local intra-tissue production (intracrinology) dependent upon the expression and activity of enzymes that regulate oestrogen biosynthesis and metabolism. Two key pathways have been implicated: while there is contradictory data on the participation of the aromatase enzyme (encoded by CYP19A1), there is increasing evidence that the steroid sulphatase pathway plays a role in both the aetiology and pathology of endometriosis. In this review, we consider the evidence related to the pathways leading to oestrogen accumulation in endometriotic lesions and how this might inform the development of new therapeutic strategies to treat endometriosis without causing the undesirable side effects of current regimes that suppress ovarian hormone production.

Estrogen-related receptor γ regulates expression of 17β-hydroxysteroid dehydrogenase type 1 in fetal growth restriction

INTRODUCTION

Estrogen-related receptor γ (ERRγ) and 17β-hydroxysteroid dehydrogenase type 1 (HSD17B1) have important roles in cell invasion and in the proliferation of many types of cancer cells. However, it remains unknown whether ERRγ and HSD17B1 contribute to abnormal placental structure and dysfunction which characterize fetal growth restriction (FGR). Therefore, the aim of this study was to investigate the expression profiles of ERRγ and HSD17B1 in placenta tissues affected by FGR and to examine a possible molecular mechanism by which ERRγ is able to regulate HSD17B1 during development of FGR.

METHODS

Placenta tissues were collected from women affected by FGR (n = 28) and from women with appropriately gestational age (AGA) (n = 30). Relative mRNA and protein levels of ERRγ and HSD17B1 in both groups were assessed by quantitative real-time PCR, immunohistochemistry, and Western blot analyses. The effect of ERRγ on trophoblast function and its associated mechanistic details were studied in the trophoblast cell line, HTR-8/SVneo, which was transfected with small interfering RNA (siRNA) targeting ERRγ.

RESULTS

Both mRNA and protein levels of ERRγ and HSD17B1 were significantly lower in FGR placentae (P < 0.05). When ERRγ expression was knocked down in HTR-8/SVneo cells with siRNA, invasion and proliferation were inhibited. In addition, HSD17B1 expression was significantly decreased. In dual luciferase reporter assays, ERRγ stimulated transcription of HSD17B1 by targeting the ERRγ response element within its 5'-flanking promoter region.

DISCUSSION

Aberrant ERRγ expression may contribute to the pathogenesis of FGR by regulating the transcriptional activity of HSD17B1.

The interplay of endocrine therapy, steroid pathways and therapeutic resistance: Importance of androgen in breast carcinoma

A great majority of breast carcinomas expresses estrogen receptor (ER) and estrogens have crucial roles in the progress of breast carcinomas. Endocrine therapy targeting ER and/or intratumoral estrogen production significantly improved clinical outcomes of the patients with ER-positive breast carcinomas. However, resistance to endocrine therapy is often observed and significant number of patients will recur after the treatment. In addition, treatment for the patients with triple-negative breast carcinomas (negative for all ER, progesterone receptor (PR) and HER2) are limited to cytotoxic chemotherapy and novel therapeutic targets need to be identified. In breast carcinoma tissues, not only ER but androgen receptor (AR) is frequently expressed, suggesting pivotal roles of androgens in the progress of breast carcinomas. Growing interest on androgen action as possible therapeutic target has been taken, but androgen action seems quite complicated in breast carcinomas and inconsistent findings has been also proposed. In this review, we will summarize recent studies regarding intratumoral androgen production and its regulation as well as distinct subset of breast carcinomas characterized by activated AR signaling and recent clinical trial targeting AR in the patients with either ER-positive and ER-negative breast carcinomas.

Mechanisms of Action of Dehydroepiandrosterone

Dehydroepiandrosterone (3β-hydroxy-5-androsten-17-one, DHEA) and its sulfated metabolite DHEA-S are the most abundant steroids in circulation and decline with age. Rodent studies have shown that DHEA has a wide variety of effects on liver, kidney, adipose, reproductive tissues, and central nervous system/neuronal function. The mechanisms by which DHEA and DHEA-S impart their physiological effects may be direct actions on plasma membrane receptors, including a DHEA-specific, G-protein-coupled receptor in endothelial cells; various neuroreceptors, e.g., aminobutyric-acid-type A, N-methyl-d-aspartate (NMDA), and sigma-1 (S1R) receptors; by binding steroid receptors: androgen and estrogen receptors (ARs, ERα, or ERβ); or by their metabolism to more potent sex steroid hormones, e.g., testosterone, dihydrotestosterone, and estradiol, which bind with higher affinity to ARs and ERs. DHEA inhibits voltage-gated T-type calcium channels. DHEA activates peroxisome proliferator-activated receptor (PPARα) and CAR by a mechanism apparently involving PP2A, a protein phosphatase dephosphorylating PPARα and CAR to activate their transcriptional activity. We review our recent study showing DHEA activated GPER1 (G-protein-coupled estrogen receptor 1) in HepG2 cells to stimulate miR-21 transcription. This chapter reviews some of the physiological, biochemical, and molecular mechanisms of DHEA and DHEA-S activity.

Estrogen and androgen-converting enzymes 17β-hydroxysteroid dehydrogenase and their involvement in cancer: with a special focus on 17β-hydroxysteroid dehydrogenase type 1, 2, and breast cancer

Sex steroid hormones such as estrogens and androgens are involved in the development and differentiation of the breast tissue. The activity and concentration of sex steroids is determined by the availability from the circulation, and on local conversion. This conversion is primarily mediated by aromatase, steroid sulfatase, and 17β-hydroxysteroid dehydrogenases. In postmenopausal women, this is the primary source of estrogens in the breast. Up to 70-80% of all breast cancers express the estrogen receptor-α, responsible for promoting the growth of the tissue. Further, 60-80% express the androgen receptor, which has been shown to have tissue protective effects in estrogen receptor positive breast cancer, and a more ambiguous response in estrogen receptor negative breast cancers. In this review, we summarize the function and clinical relevance in cancer for 17β-hydroxysteroid dehydrogenases 1, which facilitates the reduction of estrone to estradiol, dehydroepiandrosterone to androstendiol and dihydrotestosterone to 3α- and 3β-diol as well as 17β-hydroxysteroid dehydrogenases 2 which mediates the oxidation of estradiol to estrone, testosterone to androstenedione and androstendiol to dehydroepiandrosterone. The expression of 17β-hydroxysteroid dehydrogenases 1 and 2 alone and in combination has been shown to predict patient outcome, and inhibition of 17β-hydroxysteroid dehydrogenases 1 has been proposed to be a prime candidate for inhibition in patients who develop aromatase inhibitor resistance or in combination with aromatase inhibitors as a first line treatment. Here we review the status of inhibitors against 17β-hydroxysteroid dehydrogenases 1. In addition, we review the involvement of 17β-hydroxysteroid dehydrogenases 4, 5, 7, and 14 in breast cancer.

Substrate inhibition of 17β-HSD1 in living cells and regulation of 17β-HSD7 by 17β-HSD1 knockdown

This study addresses first the role of human 17β-hydroxysteroid dehydrogenase type 1 (17β-HSD1) in breast cancer (BC) cells. The enzyme has a high estrone-activating activity that is subject to strong substrate inhibition as shown by enzyme kinetics at the molecular level. We used BC cells to verify this phenomenon in living cells: estrone concentration increase did reduce the reaction with 0.025 to 4μM substrate. Moreover, 5α-dihydrotestosterone (DHT) demonstrated some inhibition of estrogen activation at both the molecular and cellular levels. The presence of DHT did not change the tendency toward substrate inhibition for estrone conversion, but shifted the inhibition toward higher substrate concentrations. Moreover, a binding study demonstrated that both DHT and dehydroepiandrosterone (DHEA) can be bound to the enzyme, thereby supporting the multi-specificity of 17β-HSD1. We then followed the concentrations of estradiol and performed q-RT-PCR measurements of reductive 17β-HSDs after 17β-HSD1 inhibition. The estradiol decrease by the 17β-HSD1 inhibition was demonstrated lending support to this observation. Knockdown and inhibition of 17β-HSD1 produced reduction in estradiol levels and the down-regulation of another reductive enzyme 17β-HSD7, thus "amplifying" the reduction of estradiol by the 17β-HSD1 modulation itself. The critical positioning of 17β-HSD7 in sex-hormone-regulation as well as the mutual regulation of steroid enzymes via estradiol in BC, are clearly demonstrated. Our study demonstrates that fundamental enzymological mechanisms are relevant in living cells. Moreover, further enzyme study in cells is merited to advance biological and medical research. We also demonstrated the central role of 17β-HSD7 in sex-hormone conversion and regulation, supporting it as a novel target for estrogen-dependent (ER+) BC.

Inhibition of 17beta-hydroxysteroid dehydrogenase type 7 modulates breast cancer protein profile and enhances apoptosis by down-regulating GRP78

17beta-hydroxysteroid dehydrogenase type 7 (17β-HSD7) promotes breast cancer cell growth via dual-catalytic activity by modulating estradiol and DHT. Here, we clarified the expression pattern of 17β-HSD7 in postmenopausal luminal A type breast cancer with The Cancer Genome Atlas (TCGA) cohort. The impact of 17β-HSD7 inhibition on the proteome of MCF-7 cells was investigated and on cell apoptosis was revealed. MCF-7 cells were treated with an efficient inhibitor of 17β-HSD7 (INH7) or with vehicle, and a differential proteomics study was performed using two-dimensional (2D) gel electrophoresis followed by mass spectrometry and ingenuity pathway analysis (IPA). Cell apoptosis was analyzed by flow cytometry, followed by reverse transcription quantitative real-time PCR (RT-qPCR) and Western blot to investigate the expression of apoptosis-related genes. Our data showed 17β-HSD7 is amplified in primary and progressive breast cancer, inhibition of 17β-HSD7 in MCF-7 cells modulated 104 proteins primarily involved in cell death/survival, cell growth and DNA processing. The expression of 78kDa glucose-regulated protein (GRP78) and anti-apoptosis factor Bcl-2 were significantly suppressed via 17β-HSD7 inhibition with INH7, consequently induced MCF-7 cell apoptosis. However, INH7 treatment of T47D, another widely used epithelial ER+ breast cancer cell line, led to an up-regulation of GRP78 expression, resulting in a limited increase in apoptosis. These results suggest cell-specific effects of INH7 in the breast cancer, which is interesting for further study. An combinatory effect on apoptosis by INH7 and Letrozole (aromatase inhibitor) was further demonstrated in MCF-7. Down-regulation of GRP78 via 17β-HSD7 inhibition enhances cell apoptosis in response to Letrozole. This study highlights GRP78 as a key regulator related to 17β-HSD7 inhibition and effect. Taken together, results from the present study suggest a hypothesis that inhibition of 17β-HSD7 would be a complementary strategy to Letrozole by suppression of GRP78 in ER+ breast cancer. However, from a research perspective, further studies have to be carried out with more breast cancer cell lines as well as in vivo model to assess the efficacy of inhibitor combination.

Acetylation targets HSD17B4 for degradation via the CMA pathway in response to estrone

Dysregulation of hormone metabolism is implicated in human breast cancer. 17β-hydroxysteroid dehydrogenase type 4 (HSD17B4) catalyzes the conversion of estradiol (E2) to estrone (E1), and is associated with the pathogenesis and development of various cancers. Here we show that E1 upregulates HSD17B4 acetylation at lysine 669 (K669) and thereby promotes HSD17B4 degradation via chaperone-mediated autophagy (CMA), while a single mutation at K669 reverses the degradation and confers migratory and invasive properties to MCF7 cells upon E1 treatment. CREBBP and SIRT3 dynamically control K669 acetylation level of HSD17B4 in response to E1. More importantly, K669 acetylation is inversely correlated with HSD17B4 in human breast cancer tissues. Our study reveals a crosstalk between acetylation and CMA degradation in HSD17B4 regulation, and a critical role of the regulation in the malignant progression of breast cancer.

Mimicking postmenopausal steroid metabolism in breast cancer cell culture: Differences in response to DHEA or other steroids as hormone sources

Following menopause virtually 100% of estrogens are synthesized in peripheral target tissues from precursor steroids of adrenal origin. These steroids are the unique source of sex steroids in these women. This positions some steroid metabolizing enzymes as primary targets for novel therapies for estrogen receptor-positive (ER+) breast cancer. However, previous research on the steroid-converting enzymes has been performed using their direct substrate as a hormone source, depending on the facility where studied and the robust signal obtained. These experiments may not always provide an accurate reflection of physiological and post-menopausal conditions. We suggest providing dehydroepiandrosterone (DHEA) as an intracrinological hormone source, and comparing the role of steroid-converting enzymes using DHEA and their direct substrates when an extensive mechanistic understanding is required. Here, we present a comparative study of these enzymes with the provision of DHEA and the direct substrates, estrone (E1) or dihydrotestosterone (DHT), or additional steroids as hormone sources, in breast cancer cells. Enzyme knockdown by respective specific siRNAs and observations on the resulting differences in biological function were carried out. Cell biology studies showed no difference in biological function for 17β-HSD1 and 17β-HSD7 when cultured with different steroid hormones: cell proliferation and estradiol levels decreased, whereas DHT accumulated; cyclinD1, PCNA, and pS2 were down-regulated after knocking down these two enzymes, although the quantitative results varied. However, culture medium supplementation was found to have a marked impact on the study of 3α-HSD3. We demonstrated that provision of different steroids as a substrate or hormone sources may promote modified biological effects: provision of DHEA is the preferred choice to mimic postmenopausal steroid metabolism in cell culture.

Androgen and breast cancer: an update

PURPOSE OF REVIEW

The review is targeted at describing the advances in our understanding of androgen actions in the breast over the last 18 months. Androgens are current 'hot topics' in breast cancer because of their potential as therapeutics in situations where we currently do not have good clinical options. This is true for both estrogen receptor alpha (ERα) negative and ERα positive cancers.

RECENT FINDINGS

The review has focused on examining associations between androgen receptor and patient prognosis and outcomes in different breast cancer subtypes. A logical extension of this is covering the timely topic of the use of androgen-directed therapy in these patients. The principle settings in which this is being considered is in ERα positive cancer with therapeutic resistance to ER-directed therapies and in ERα negative breast cancer that lack current standard targeted therapies. Finally interactions between mutations, and the potential role of androgen in the normal hierarchy of mammary cell differentiation and the relationship of this to cancer, are considered.

SUMMARY

Androgens are firmly established as important factors across multiple breast cancer subtypes. The future challenge for basic researchers and important development for clinicians is going to be translating this understanding into effective therapeutics for the benefit of breast cancer patients.

Current knowledge of the multifunctional 17β-hydroxysteroid dehydrogenase type 1 (HSD17B1)

At the late 1940s, 17β-HSD1 was discovered as the first member of the 17β-HSD family with its gene cloned. The three-dimensional structure of human 17β-HSD1 is the first example of any human steroid converting enzyme. The human enzyme's structure and biological function have thus been studied extensively in the last two decades. In humans, the enzyme is expressed in placenta, ovary, endometrium and breast. The high activity of estrogen activation provides the basis of 17β-HSD1's implication in estrogen-dependent diseases, such as breast cancer, endometriosis and non-small cell lung carcinomas. Its dual function in estrogen activation and androgen inactivation has been revealed in molecular and breast cancer cell levels, significantly stimulating the proliferation of such cells. The enzyme's overexpression in breast cancer was demonstrated by clinical samples. Inhibition of human 17β-HSD1 led to xenograft tumor shrinkage. Unfortunately, through decades of studies, there is still no drug using the enzyme's inhibitors available. This is due to the difficulty to get rid of the estrogenic activity of its inhibitors, which are mostly estrogen analogues. New non-steroid inhibitors for the enzyme provide new hope for non-estrogenic inhibitors of the enzyme.