In situ production of sex steroids in human breast carcinoma

Pregnane X receptor (PXR) deficiency promotes hepatocarcinogenesis via induction of Akr1c18 expression and prostaglandin F2α (PGF2α) levels

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide. Pregnane X receptor (PXR), a xenobiotic-sensing nuclear receptor, plays a critical role in the metabolism of endogenous and exogenous substances in the liver. Here, we investigate whether PXR plays a role in pathogenesis of HCC. We show that liver tumors were developed in diethylnitrosamine (DEN)-treated in PXR knockout (KO) mice. Hepatic levels of prostaglandin F2α (PGF2α) and aldo-keto reductase family 1 member C18 (Akr1c18), a prostaglandin synthase of catalyzing reduction of PGH2 to PGF2α, were significantly elevated in DEN-treated PXR KO mice. Hepatic mRNA levels of alpha fetoprotein (AFP), cyclin D1 (Ccnd1), fibroblast growth factor 21 (FGF21), and inflammatory cytokine interleukin 6 (IL-6) were significantly increased in DEN-treated PXR KO mice. Other members of Akr1c family, liver metabolizing enzymes including Cyp1a2, Cyp2b10 and Cyp3a11, and bile acid synthesis enzyme Cyp7a1 mRNA levels were significantly decreased in DEN-treated PXR KO mice. Our findings revealed that PXR deficiency promoted DEN-induced HCC in mice via induction of Akr1c18 expression and PGF2α levels and the increased PGF2α levels synthetized by Akr1c18 enhanced hepatocytes proliferation and induced inflammatory cytokine production, which accelerated liver tumor development after DEN treatment, suggesting that PXR deficiency may create a microenvironment that is more prone to DEN-induced liver tumors and targeting PXR and Akr1c18 to reduce PGF2α biosynthesis may be a potential and novel therapeutic strategy for HCC.

Breast Cancer: Targeting of Steroid Hormones in Cancerogenesis and Diagnostics

Breast cancer is the most common malignancy in women with high mortality. Sensitive and specific methods for the detection, characterization and quantification of endogenous steroids in body fluids or tissues are needed for the diagnosis, treatment and prognosis of breast cancer and many other diseases. At present, non-invasive diagnostic methods are gaining more and more prominence, which enable a relatively fast and painless way of detecting many diseases. Metabolomics is a promising analytical method, the principle of which is the study and analysis of metabolites in biological material. It represents a comprehensive non-invasive diagnosis, which has a high potential for use in the diagnosis and prognosis of cancers, including breast cancer. This short review focuses on the targeted metabolomics of steroid hormones, which play an important role in the development and classification of breast cancer. The most commonly used diagnostic tool is the chromatographic method with mass spectrometry detection, which can simultaneously determine several steroid hormones and metabolites in one sample. This analytical procedure has a high potential in effective diagnosis of steroidogenesis disorders. Due to the association between steroidogenesis and breast cancer progression, steroid profiling is an important tool, as well as in monitoring disease progression, improving prognosis, and minimizing recurrence.

Changes in steroid hormone profile and tumour progression after genistein treatment of canine inflammatory mammary cancer xenotransplanted mice

Isoflavones, such as genistein, have been proposed to have beneficial effects on health, including preventive or therapeutic actions in carcinogenesis. Their structural similarity to oestrogens allows them to bind at the cellular level with oestrogen receptors. Therefore, this study attempted to determine the antitumoural effects of genistein administered in a canine inflammatory mammary cancer xenograft model, in terms of tumour proliferation, appearance of metastases and steroid hormone regulation. Using histology and immunohistochemical analyses as well as the EIA technique for hormonal determinations, the antitumoural effects of genistein on an inflammatory mammary cancer xenograft model were assessed for 3 weeks. Mice treated with genistein showed higher Ki-67 levels than the control group. There were significantly more distant metastases in the genistein-treated xenografts versus the control group. Intratumoural and serum progesterone, androstenedione and oestrogen levels in treated mice were elevated, whereas intratumoural testosterone levels were decreased compared to the control group. These results revealed that genistein ingestion promotes tumour proliferation and elevates metastatic rates by increasing intratumoural and circulating oestrogen levels in a mammary cancer xenograft model.

AKR1C3 (type 5 17β-hydroxysteroid dehydrogenase/prostaglandin F synthase): Roles in malignancy and endocrine disorders

Aldo-Keto-Reductase 1C3 (type 5 17β-hydroxysteroid dehydrogenase (HSD)/prostaglandin (PG) F_2α synthase) is the only 17β-HSD that is not a short-chain dehydrogenase/reductase. By acting as a 17-ketosteroid reductase, AKR1C3 produces potent androgens in peripheral tissues which activate the androgen receptor (AR) or act as substrates for aromatase. AKR1C3 is implicated in the production of androgens in castration-resistant prostate cancer (CRPC) and polycystic ovarian syndrome; and is implicated in the production of aromatase substrates in breast cancer. By acting as an 11-ketoprostaglandin reductase, AKR1C3 generates 11β-PGF_2α to activate the FP receptor and deprives peroxisome proliferator activator receptorγ of its putative PGJ₂ ligands. These growth stimulatory signals implicate AKR1C3 in non-hormonal dependent malignancies e.g. acute myeloid leukemia (AML). AKR1C3 moonlights by acting as a co-activator of the AR and stabilizes ubiquitin ligases. AKR1C3 inhibitors have been used clinically for CRPC and AML and can be used to probe its pluripotency.

Structural and Functional Biology of Aldo-Keto Reductase Steroid-Transforming Enzymes

Aldo-keto reductases (AKRs) are monomeric NAD(P)(H)-dependent oxidoreductases that play pivotal roles in the biosynthesis and metabolism of steroids in humans. AKR1C enzymes acting as 3-ketosteroid, 17-ketosteroid, and 20-ketosteroid reductases are involved in the prereceptor regulation of ligands for the androgen, estrogen, and progesterone receptors and are considered drug targets to treat steroid hormone-dependent malignancies and endocrine disorders. In contrast, AKR1D1 is the only known steroid 5β-reductase and is essential for bile-acid biosynthesis, the generation of ligands for the farnesoid X receptor, and the 5β-dihydrosteroids that have their own biological activity. In this review we discuss the crystal structures of these AKRs, their kinetic and catalytic mechanisms, AKR genomics (gene expression, splice variants, polymorphic variants, and inherited genetic deficiencies), distribution in steroid target tissues, roles in steroid hormone action and disease, and inhibitor design.

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.

Progestins used in endocrine therapy and the implications for the biosynthesis and metabolism of endogenous steroid hormones

Steroidogenesis refers to the de novo synthesis of steroid hormones from cholesterol by a number of sequential enzyme catalysed reactions in the adrenal and the gonads. In addition, circulating steroid hormone precursors are further metabolised in selected peripheral tissues. It has been suggested that the biosynthesis of endogenous steroid hormones can be modulated by progestins, used widely by women in female reproductive medicine. However, as a number of structurally diverse progestins with different pharmacological properties are available, it is possible that these synthetic compounds may vary in their effects on steroidogenesis. This review summarises the evidence indicating that progestins influence the biosynthesis of steroid hormones in the adrenal and gonads, as well as the metabolism of these endogenous hormones in the breast, highlighting the limitations to the current knowledge and directions for future research.

Associations of obesity and physical activity with serum and intratumoral sex steroid hormone levels among postmenopausal women with breast cancer: analysis of paired serum and tumor tissue samples

PURPOSE

It has been hypothesized that intratumoral estrogens may play important roles in the growth of breast cancer. However, few studies have investigated such intratumoral hormones, or their association with risk factors of breast cancer.

METHODS

In this cross-sectional study, hormone levels in paired serum and tumor tissue samples from 146 postmenopausal women with breast cancer were measured by liquid chromatography-tandem mass spectrometry and compared between estrogen/progesterone (ER/PgR) subtypes. The associations of risk factors including body mass index (BMI) and other lifestyle factors with these hormone levels were investigated using analysis of covariance.

RESULTS

The level of estradiol (E2) in tumor tissue was extremely high in women with ER+ (geometric mean 95.6 pg/g) relative to women with ER-/PgR- (8.9 pg/g), whereas serum E2 level did not differ much between the two groups (3.1 and 2.8 pg/ml, respectively). Serum levels of precursors for E2, including testosterone (T) and androstenedione (Adione), and tissue Adione level, were high among women with ER+. After adjustment for confounding variables, BMI was found to be positively associated with tissue levels of E2, estrone (E1), T, and Adione among women with ER+ (P _trend < 0.0001 for E2; 0.0016 for E1; 0.0002 for T; and 0.03 for Adione).

CONCLUSION

The data suggest that tissue E2 is related to the growth of receptor-positive breast cancer and that risk factors such as BMI affect tissue levels of E2 and its precursors. Understanding of hormonal environments within tumor tissue may be important for elucidating hormonal etiology of breast cancer and improving the prognosis of 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.

Steroid Tumor Environment in Male and Female Mice Model of Canine and Human Inflammatory Breast Cancer

Canine inflammatory mammary cancer (IMC) shares clinical and histopathological characteristics with human inflammatory breast cancer (IBC) and has been proposed as a good model for studying the human disease. The aim of this study was to evaluate the capacity of female and male mice to reproduce IMC and IBC tumors and identify the hormonal tumor environment. To perform the study sixty 6–8-week-old male and female mice were inoculated subcutaneously with a suspension of 10⁶IPC-366 and SUM149 cells. Tumors and serum were collected and used for hormonal analysis. Results revealed that IPC-366 reproduced tumors in 90% of males inoculated after 2 weeks compared with 100% of females that reproduced tumor at the same time. SUM149 reproduced tumors in 40% of males instead of 80% of females that reproduced tumors after 4 weeks. Both cell lines produce distant metastasis in lungs being higher than the metastatic rates in females. EIA analysis revealed that male tumors had higher T and SO4E1 concentrations compared to female tumors. Serum steroid levels were lower than those found in tumors. In conclusion, IBC and IMC male mouse model is useful as a tool for IBC research and those circulating estrogens and intratumoral hormonal levels are crucial in the development and progression of tumors.

Intratumoral estrogen production and actions in luminal A type invasive lobular and ductal carcinomas

The great majority of invasive lobular carcinoma (ILC) is estrogen-dependent luminal A type carcinoma but the details of estrogen actions and its intratumoral metabolism have not been well studied compared to invasive ductal carcinoma (IDC). We first immunolocalized estrogen-related enzymes including estrogen sulfotransferase (EST), estrogen sulfatase (STS), 17β-hydroxysteroid dehydrogenase (HSD) 1/2, and aromatase. We then evaluated the tissue concentrations of estrogens in ILC and IDC and subsequently estrogen-responsive gene profiles in these tumors in order to explore the possible differences and/or similarity of intratumoral estrogen environment of these two breast cancer subtypes. The status of STS and 17βHSD1 was significantly lower in ILCs than IDCs (p = 0.022 and p < 0.0001), but that of EST and 17βHSD2 vice versa (p < 0.0001 and p = 0.0106). In ILCs, tissue concentrations of estrone and estradiol were lower than those in IDCs (p = 0.0709 and 0.069). In addition, the great majority of estrogen response genes tended to be lower in ILCs. Among those genes above, FOXP1 was significantly higher in ILCs than in IDCs (p = 0.002). FOXP1 expression was reported to be significantly higher in relapse-free IDC patients treated with tamoxifen. Therefore, tamoxifen may be considered an option of endocrine therapy for luminal A type ILC patients. This is the first study to demonstrate the detailed and comprehensive status of intratumoral production and metabolism of estrogens and the status of estrogen response genes in luminal A-like ILC with comparison to those in luminal A-like IDCs.

Transcript level of AKR1C3 is down-regulated in gastric cancer

Steroid hormones have been shown to play a role in gastric carcinogenesis. Large amounts of steroid hormones are locally produced in the peripheral tissues of both genders. Type 5 of 17β-hydroxysteroid dehydrogenase, encoded by the AKR1C3 gene, plays a pivotal role in both androgen and estrogen metabolism, and its expression was found to be deregulated in different cancers. In this study we measured AKR1C3 transcript and protein levels in nontumoral and primary tumoral gastric tissues, and evaluated their association with some clinicopathological features of gastric cancer (GC). We found decreased levels of AKR1C3 transcript (p < 0.0001) and protein (p = 0.0021) in GC tissues compared with the adjacent, apparently histopathologically normal, mucosa. Lower levels of AKR1C3 transcript were observed in diffuse and intestinal types of GC, whereas AKR1C3 protein levels were decreased in tumors with multisite localization, in diffuse histological type, T3, T4, and G3 grades. We also determined the effect of the histone deacetylase inhibitor sodium butyrate (NaBu) on AKR1C3 expression in EPG 85-257 and HGC-27 GC cell lines. We found that NaBu elevates the levels of both AKR1C3 transcript and protein in the cell lines we investigated. Together, our results suggest that decreased expression of AKR1C3 may be involved in development of GC and can be restored by NaBu.

Intratumoral estrogen sulfotransferase induction contributes to the anti-breast cancer effects of the dithiocarbamate derivative TM208

AIM

Sulfotransferase-catalyzed sulfation is the most important pathway for inactivating estrogens. Thus, activation of estrogen sulfotransferase (EST) may be an alternative approach for the treatment of estrogen-dependent breast cancer. In this study we investigated the involvement of EST in anti-breast cancer effects of the dithiocarbamate derivative TM208 in vitro and in vivo.

METHODS

The viability of human breast cancer MCF-7 cells was determined using a SBB assay. Nude mice bearing MCF-7 cells were orally administered TM208 (50 and 150 mg·kg(-1)·d(-1)) for 18 days. The xenograft tumors and uteri were collected. The mRNA expression of EST was examined with real-time PCR. EST protein was detected with Western blot, ELISA or immunohistochemical staining assays. A radioactive assay was used to measure the EST activity. Uterotropic bioassay was used to examine the uterine estrogen responses.

RESULTS

Treatment with TM208 (10, 15 and 20 μmol/L) concentration-dependently increased EST expression in MCF-7 cells in vitro. Co-treatment with triclosan, an inhibitor of sulfonation, abolished TM208-induced cytotoxicity in MCF-7 cells. TM208 exhibited an apparent anti-estrogenic property: it exerted more potent cytotoxicity in E2-treated MCF-7 cells. In the nude mice bearing MCF-7 cells, TM208 administration time-dependently increased the expression and activity of EST, and blocked the gradual increase of E2 concentration in the xenograft tumors. Furthermore, TM208 administration blocked the estrogens-stimulated uterine enlargement. Tamoxifen, a positive control drug, produced similar effects on the expression and activity of EST in vitro and in vivo.

CONCLUSION

The induction of EST and reduction of estrogen concentration contribute to the anti-breast cancer action of TM208 and tamoxifen. TM208 may be developed as anticancer drug for the treatment of estrogen receptor-positive breast cancer.

In vitro interactions between mammary fibroblasts (Hs 578Bst) and cancer epithelial cells (MCF-7) modulate aromatase, steroid sulfatase and 17β-hydroxysteroid dehydrogenases

Our objectives were to investigate the interactions between mammary cancer epithelial cells (MCF-7) and stromal cells (Hs-578Bst) at the level of the expression and inhibition of steroidogenesis enzymes by using monolayer and three dimensional co-culture models. Expressions of steroidogenesis enzymes and E2/DHT conversions in co-cultured MCF-7 and Hs-578Bst cells as well as the effects of aromatase inhibitor combined to steroid sulfatase (STS) and 17β-hydroxysteroid dehydrogenases (17βHSDs) inhibitors were evaluated. 17β-HSD type 7 was mostly modulated in MCF-7 cells whereas aromatase was mostly regulated in Hs578Bst cells thereby increasing E2 conversion and MCF-7 cell growth. A combination of inhibitors toward aromatase, STS and 17β-HSD7, was found to be the most significant treatment in decreasing E2 and elevating DHT thus inhibiting MCF-7 cell proliferation and spheroid-like cancer cell aggregation in collagen gel. The interactions between those cells modulated E2 formation in paracrine/intracrine manners by synergistically regulating aromatase, 17β-HSD7 and STS. Among tumor-associated cells, stromal fibroblasts may participate in intratumoral E2 deposition; therefore promoting breast cancer cell growth.

Promiscuity and diversity in 3-ketosteroid reductases

Many steroid hormones contain a Δ(4)-3-ketosteroid functionality that undergoes sequential reduction by 5α- or 5β- steroid reductases to produce 5α- or 5β-dihydrosteroids; and a subsequent 3-keto-reduction to produce a series of isomeric tetrahydrosteroids. Apart from steroid 5α-reductase all the remaining enzymes involved in the two step reduction process in humans belong to the aldo-keto reductase (AKR) superfamily. The enzymes involved in 3-ketosteroid reduction are AKR1C1-AKR1C4. These enzymes are promiscuous and also catalyze 20-keto- and 17-keto-steroid reduction. Interest in these reactions exist since they regulate steroid hormone metabolism in the liver, and in steroid target tissues, they may regulate steroid hormone receptor occupancy. In addition many of the dihydrosteroids are not biologically inert. The same enzymes are also involved in the metabolism of synthetic steroids e.g., hormone replacement therapeutics, contraceptive agents and inhaled glucocorticoids, and may regulate drug efficacy at their cognate receptors. This article reviews these reactions and the structural basis for substrate diversity in AKR1C1-AKR1C4, ketosteroid reductases. This article is part of a Special Issue entitled 'Steroid/Sterol signaling'.

Aldo-keto reductase 1C3 (AKR1C3) is associated with the doxorubicin resistance in human breast cancer via PTEN loss

Aldo-keto reductase 1C3 (AKR1C3), one member of the aldo-keto reductase superfamily, is involved in a variety of cancers. Recently, AKR1C3 has been demonstrated to be related with the doxorubicin (DOX) resistance in human breast cancer. Here, we attempted to explore the resistance mechanism mediated by AKR1C3. First, one DOX resistant breast cancer cell line MCF-7/DOX was successfully established and an increased level of AKR1C3 was observed in the MCF-7/DOX cells compared to the parental MCF-7 cells. To investigate the contribution of AKR1C3 in the DOX resistance, we further established an AKR1C3 overexpression cell line, referred to MCF-7/AKR1C3. In the MCF-7/AKR1C3 cells, the DOX induced cytotoxicity, detected by CCK-8 cell viability assay and DAPI staining, was greatly reduced (3.2-fold increase in the IC50 value). Interestingly, a loss of tumor suppressor PTEN (phosphatase and tensin homolog deleted on chromosome 10) was observed when AKR1C3 was overexpressed. Secondary to the PTEN loss, the activated Akt also markedly increased. In addition, the AKR1C3 mediated DOX resistance can be conquered by the Akt inhibitor (LY294002). Furthermore, we found that the expression levels of AKR1C3 and PTEN had a negative relationship in the human breast tumor tissues (the standard correlation coefficient=-0.71; P=0.048). In conclusion, our data suggested that the AKR1C3 mediated DOX resistance might be resulted from the activation of anti-apoptosis PTEN/Akt pathway via PTEN loss. AKR1C3 may present a potential therapeutic target in addressing DOX resistance in breast cancer.

Clinical implications of aldo-keto reductase family 1 member C3 and its relationship with lipocalin 2 in cancer of the uterine cervix

OBJECTIVE

Over-expression of the aldo-keto reductase family 1 member C3 (AKR1C3) has been demonstrated in many human cancers. Lipocalin 2 (LCN2) is reported to inhibit cervical cancer metastasis but little is known regarding its relationship with AKR1C3 in the development and progression of uterine cervical cancer. This study aimed to investigate the involvement of AKR1C3 and its relationship with LCN2 in cervical cancer.

METHODS

The roles of AKR1C3 and LCN2 were investigated using the lentivirus shRNA system in SiHa and Caski cervical cancer cells. LCN2 and matrix metalloproteinase-2 (MMP-2) promoters were constructed to demonstrate transcriptional regulation by shAKR1C3 and shLCN2, respectively. The influences of metastatic phenotypes were analyzed by wound healing, Boyden chamber, and immunofluorescence assays. The activity of MMP-2 was determined by zymography assay. The impacts of AKR1C3 and LCN2 on patient prognosis were evaluated using tissue microarrays by Cox regression and Kaplan-Meier models.

RESULTS

Silencing of the AKR1C3 gene increased the expression of LCN2 and decreased the migratory and invasive abilities and changed the cytoskeleton of cervical cancer cells. When AKR1C3 was over-expressed, it decreased LCN2 promoter activity and LCN2 expression and increased cell migration. The mRNA level and enzyme activity of MMP-2 increased in silenced LCN2 cells. Positive AKR1C3 and negative LCN2 were correlated with higher recurrence and poorer survival of cervical cancer patients.

CONCLUSIONS

Silencing of AKR1C3 increases LCN2 expression and inhibits metastasis in cervical cancer. Both AKR1C3 and LCN2 serve as molecular targets for cancer therapy to improve the clinical outcome of cervical cancer patients.

Androgen resistance in female mice increases susceptibility to DMBA-induced mammary tumors

Hormones, notably estrogens, are pivotal in the origins of breast cancer but androgenic effects, while supported by persistence of AR expression in breast cancers, remain controversial. This study determined the role of the androgen actions via androgen receptor (AR) in experimental mammary cancer. Androgen-resistant female and male mice (ARKO) were generated using Cre/loxP technique and featured a global AR inactivation. The effect of AR inactivation and influence of genetic background on 7,12-dimethylbenz[a]anthracene (DMBA)-induced tumorigenesis was confirmed using two separate ARKO models with different genetic backgrounds. The onset of palpable mammary tumors was significantly faster in ARKO females (median time 22 vs 34 weeks, respectively; (p = 0.0024; multivariate Cox regression) compared to WT and independent of the mouse genetic background. The cumulative incidence at 9 months was 81 ± 10% [mean ± SE] for ARKO compared to 50 ± 13% in WT females. The increased DMBA susceptibility of ARKO females was associated with a higher epithelial proliferation index but not with major structural or receptor (estrogen or progesterone) expression differences between the virgin WT or ARKO female mammary glands. AR inactivation allowed substantial ductal extension in ARKO males while WT males displayed only rudimentary epithelial branches or complete regression of epithelial structures. Yet, DMBA did not induce epithelial mammary tumors in WT or ARKO males, demonstrating that AR inactivation alone is insufficient to promote mammary tumors. These results demonstrate that AR inactivation accelerates mammary carcinogenesis in female mice exposed to the chemical carcinogen DMBA regardless of mouse genetic background but require prior exposure to endogenous ovarian hormones.

The role of estrogen-metabolizing enzymes and estrogen receptors in human epidermis

Local estrogen metabolism and its sensitivities in the skin have been also suggested to contribute to skin homeostasis in addition to age- and/or gender-dependent circulating estrogen, even though their local mechanisms have been largely unknown. To characterize their potential correlations, age- and gender-dependencies were evaluated focusing on 5 pivotal estrogen-metabolizing enzymes including aromatase, estrogen sulfotransferase, steroid sulfatase, and 17β-hydroxysteroid dehydrogenases and estrogen receptors (ERα and ERβ) using immunohistochemistry of 100 human skin specimens. When their epidermal expression levels were compared among 7 age groups, ranging from the teens to the seventies, the highest expression in the teens group and the lowest expression in the seventies group were found in the expression of aromatase and ERβ, respectively, while no significant differences between the male and the female groups were found in the immunoreactivities of our interested proteins. Our results suggest that age-related differences in aromatase and ERβ expressions impact epidermal homeostasis.

Molecular therapy of breast cancer: progress and future directions

Breast cancer is a major cause of death in Western women, with a 10% lifetime risk of the disease. Most breast cancers are estrogen-dependent. Molecular therapies for breast cancer have developed rapidly in the past few decades and future treatment strategies are being investigated. The selective estrogen receptor (ER) modulator tamoxifen, which until now has served as a standard therapy, functions not only as an estrogen antagonist but also as an estrogen agonist in terms of bone maintenance. Aromatase inhibitors have performed well in international trials and have become a new standard therapy for estrogen-dependent breast cancer. The systematic study of estrogen activation pathways suggests that the enzymes steroid sulfatase and 17beta-hydroxysteroid dehydrogenase type 1, which both have pivotal roles in estrogen biosynthesis, are promising targets; the results of a phase I trial of steroid sulfatase inhibitors are encouraging. The activity of the human epidermal growth factor receptor (HER) pathway correlates negatively with that of the ER. HER2 is overexpressed in 22% of all breast cancers. In the decade since HER2 began being targeted, the monoclonal antibody trastuzumab has been used as well as pertuzumab and HER2 vaccines. Among the estrogen-independent breast cancers, the basal-like subtype has low survival, and therapeutic improvement is a priority. Crosstalk between ER and HER2 signaling pathways means that combinatory therapies may hold the key to enhancement of treatment responses. Other molecular therapies involving functional genomics and RNA interference studies also hold promise.

Testosterone membrane-initiated action in breast cancer cells: Interaction with the androgen signaling pathway and EPOR

Membrane-initiated androgen actions have now been acknowledged, even though a specific binding site has not been biochemically characterized yet. Recent data indicate that testosterone-BSA, a non-permeable testosterone analog, can exert specific actions in breast cancer cell lines, including proper transcriptional effects, independent of the intracellular androgen sites. In the present work we explore the effects of testosterone-BSA in two specifically modified pathways, revealed by early trascriptome analysis, namely the non-genotropic androgen signaling and the HIF1alpha pathway. We provide evidence that p38 MAPK and PI3K/Akt/NFkappaB and/or Rho/Actin pathways are directly involved in testosterone-induced apoptosis, while the JNK/c-JUN pathway is involved in membrane site-initiated transcription. Furthermore we show that membrane-acting androgens modify the transcription of the erythropoietin receptor (EPOR), leading to erythropoietin-initiated actions. Interestingly, association of recombinant human erythropoietin (rHuEPO) together with testosterone-BSA protects cells from apoptosis, through discrete signaling events. The effect of testosterone-BSA is exerted through the classical erythropoietin promoter, while rHuEPO decreases the transcription of EPOR acting on a newly identified regulatory/promoter region, upstream of its known promoter. These results suggest a new interaction of membrane-acting androgen with EPOR and should be taken into account in the pharmaceutical manipulations of breast cancer patients.

Aromatase and in situ estrogen production in DCIS (ductal carcinoma in situ) of human breast

Ductal carcinoma in situ or DCIS belongs to intraductal proliferative lesions, which are a group of cytologically and architecturally diverse ductal proliferations, typically originating from the terminal duct-lobular units. In these intraductal proliferative diseases, estrogens are considered to be involved in the progression of the disease especially from ductal non-neoplastic hyperplasia to DCIS and possibly development of invasive carcinoma from DCIS. Estrogen receptor (ER) alpha is abundantly expressed in atypical ductal hyperplasia and low grade DCIS. Suppression of estrogenic actions using tamoxifen resulted in inhibition of recurrence of DCIS and/or of progression into invasive carcinoma. Intratumoral estrogen concentration in DCIS determined by liquid chromatography/electrospray tandem mass spectrometry is significantly higher than that in non-neoplastic breast tissues with statistically not lower than that in invasive carcinoma. Aromatase mRNA expression in both stromal and parenchymal cells of DCIS determined by quantitative RT-PCR following laser capture microdissection was also much higher than that in non-neoplastic breast, although lower than that in invasive carcinoma. Immunohistochemistry of aromatase also revealed the similar patterns of immunolocalization as in invasive carcinoma. Aromatase is overexpressed in noninvasive breast malignancies including DCIS and results in elevated concentrations of intratumoral estradiol. These findings could provide the scientific rationale as to employing aromatase inhibitors in the management of ER positive DCIS patients.

Aldo-keto reductase 1C3 expression in MCF-7 cells reveals roles in steroid hormone and prostaglandin metabolism that may explain its over-expression in breast cancer

Aldo-keto reductase (AKR) 1C3 (type 5 17beta-hydroxysteroid dehydrogenase and prostaglandin F synthase), may stimulate proliferation via steroid hormone and prostaglandin (PG) metabolism in the breast. Purified recombinant AKR1C3 reduces PGD(2) to 9alpha,11beta-PGF(2), Delta(4)-androstenedione to testosterone, progesterone to 20alpha-hydroxyprogesterone, and to a lesser extent, estrone to 17beta-estradiol. We established MCF-7 cells that stably express AKR1C3 (MCF-7-AKR1C3 cells) to model its over-expression in breast cancer. AKR1C3 expression increased steroid conversion by MCF-7 cells, leading to a pro-estrogenic state. Unexpectedly, estrone was reduced fastest by MCF-7-AKR1C3 cells when compared to other substrates at 0.1muM. MCF-7-AKR1C3 cells proliferated three times faster than parental cells in response to estrone and 17beta-estradiol. AKR1C3 therefore represents a potential target for attenuating estrogen receptor alpha induced proliferation. MCF-7-AKR1C3 cells also reduced PGD(2), limiting its dehydration to form PGJ(2) products. The AKR1C3 product was confirmed as 9alpha,11beta-PGF(2) and quantified with a stereospecific stable isotope dilution liquid chromatography-mass spectrometry method. This method will allow the examination of the role of AKR1C3 in endogenous prostaglandin formation in response to inflammatory stimuli. Expression of AKR1C3 reduced the anti-proliferative effects of PGD(2) on MCF-7 cells, suggesting that AKR1C3 limits peroxisome proliferator activated receptor gamma (PPARgamma) signaling by reducing formation of 15-deoxy-Delta(12,14)-PGJ(2) (15dPGJ(2)).

Intracrinology of breast microenvironment: hormonal status in nipple aspirate fluid and its relationship to breast cancer

Breast cancer, a complex and multifactorial disease, is the most commonly diagnosed malignancy affecting women. Methods currently available for breast cancer detection have well-described limitations; in this respect, the intraductal approaches directly assess the microenvironment of the breast. Nipple aspirate fluid (NAF) can be noninvasively obtained from the breast in most women and represents a promising biological tool to assess metabolic, hormonal and molecular changes occurring in the cells lining the ducts, from which breast cancer arises. The aim of this review is to highlight the application of NAF studies in the field of biomarker discovery, which provide results useful for early detection and prevention of breast cancer risk; in fact, the analysis of NAF (mirroring the ductal-lobular microenvironment) is a reliable method for assessment of metabolic/hormonal pathways within the mammary gland, identifying biomolecular mechanisms of breast cancer initiation and progression. The intracrinology of breast microenvironment (i.e., hormonal status in NAF) may provide independent diagnostic/prognostic factors, highlighting the importance of early altered hormonal metabolism (e.g., aromatase, estrogen sulfotransferase and steroid sulfatase pathway) in relation to breast cancer initiation. The possible application of targeted therapies through the inhibition of intratumoral enzymes involved in steroid metabolism is also discussed. The intraductal approach to hormone analyses may provide a further panel of biomarkers providing clinical benefits and strengthening the armory against breast cancer.

Integrated view on 17beta-hydroxysteroid dehydrogenases

17beta-Hydroxysteroid dehydrogenases (17beta-HSDs) are important enzymes in steroid metabolism. Long known members of the protein family seemed to be well characterised concerning their role in the regulation of the biological potency of steroid hormones, but today more and more evidence points to pivotal contributions of these enzymes in a variety of other metabolic pathways. Therefore, studies on 17beta-HSDs develop towards metabolomic survey. Latest research results give new insights into the complex metabolic interconnectivity of the 17beta-HSDs. In this paper metabolic activities of 17beta-HSDs will be compared, their interplay with endogenous substrates summarised, and interlacing pathways depicted. Strategies on deciphering the physiological role of 17beta-HSDs and the genetic predisposition for associated diseases will be presented.

Expression of estrogenicity genes in a lineage cell culture model of human breast cancer progression

TaqMan Gene Expression assays were used to profile the mRNA expression of estrogen receptor (ERalpha and ERbeta) and estrogen metabolism enzymes including cytosolic sulfotransferases (SULT1E1, SULT1A1, SULT2A1, and SULT2B1), steroid sulfatase (STS), aromatase (CYP19), 17beta-hydroxysteroid dehydrogenases (17betaHSD1 and 2), CYP1B1, and catechol-O-methyltransferase (COMT) in an MCF10A-derived lineage cell culture model for basal-like human breast cancer progression and in ERalpha-positive luminal MCF7 breast cancer cells. Low levels of ERalpha and ERbeta mRNA were present in MCF10A-derived cell lines. SULT1E1 mRNA was more abundant in confluent relative to subconfluent MCF10A cells, a non-tumorigenic proliferative breast disease cell line. SULT1E1 was also expressed in preneoplastic MCF10AT1 and MCF10AT1K.cl2 cells, but was markedly repressed in neoplastic MCF10A-derived cell lines as well as in MCF7 cells. Steroid-metabolizing enzymes SULT1A1 and SULT2B1 were only expressed in MCF7 cells. STS and COMT were widely detected across cell lines. Pro-estrogenic 17betaHSD1 mRNA was most abundant in neoplastic MCF10CA1a and MCF10DCIS.com cells, while 17betaHSD2 mRNA was more prominent in parental MCF10A cells. CYP1B1 mRNA was most abundant in MCF7 cells. Treatment with the histone deacetylase inhibitor trichostatin A (TSA) induced SULT1E1 and CYP19 mRNA but suppressed CYP1B1, STS, COMT, 17betaHSD1, and 17betaHSD2 mRNA in MCF10A lineage cell lines. In MCF7 cells, TSA treatment suppressed ERalpha, CYP1B1, STS, COMT, SULT1A1, and SULT2B1 but induced ERbeta, CYP19 and SULT2A1 mRNA expression. The results indicate that relative to the MCF7 breast cancer cell line, key determinants of breast estrogen metabolism are differentially regulated in the MCF10A-derived lineage model for breast cancer progression.

Physical activity and postmenopausal breast cancer: proposed biologic mechanisms and areas for future research

Convincing evidence now supports a probable preventive role for physical activity in postmenopausal breast cancer. The mechanisms by which long-term physical activity affect risk, however, remain unclear. The aims of this review were to propose a biological model whereby long-term physical activity lowers postmenopausal breast cancer risk and to highlight gaps in the epidemiologic literature. To address the second aim, we summarized epidemiologic literature on 10 proposed biomarkers, namely, body mass index (BMI), estrogens, androgens, sex hormone binding globulin, leptin, adiponectin, markers of insulin resistance, tumor necrosis factor-alpha, interleukin-6, and C-reactive protein, in relation to postmenopausal breast cancer risk and physical activity, respectively. Associations were deemed "convincing," "probable," "possible," or "hypothesized" using set criteria. Our proposed biological model illustrated the co-occurrence of overweight/obesity, insulin resistance, and chronic inflammation influencing cancer risk through interrelated mechanisms. The most convincing epidemiologic evidence supported associations between postmenopausal breast cancer risk and BMI, estrogens, and androgens, respectively. In relation to physical activity, associations were most convincing for BMI, estrone, insulin resistance, and C-reactive protein. Only BMI and estrone were convincingly (or probably) associated with both postmenopausal breast cancer risk and physical activity. There is a need for prospective cohort studies relating the proposed biomarkers to cancer risk and for long-term exercise randomized controlled trials comparing biomarker changes over time, specifically in postmenopausal women. Future etiologic studies should consider interactions among biomarkers, whereas exercise trials should explore exercise effects independently of weight loss, different exercise prescriptions, and effects on central adiposity.

Steroid sulfatase and estrogen sulfotransferase in colon carcinoma: regulators of intratumoral estrogen concentrations and potent prognostic factors

Previous epidemiologic and in vitro studies have indicated a potential involvement of estrogens in the pathogenesis of human colon carcinoma, but the precise roles of estrogens have remained largely unknown. Therefore, in this study, we first measured intratumoral concentrations of estrogens in 53 colon carcinomas using liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS). Tissue concentrations of total estrogen [estrone (E(1)) + estradiol] and E(1) were significantly (2.0- and 2.4-fold, respectively) higher in colon carcinoma tissues than in nonneoplastic colonic mucosa (n = 31), and higher intratumoral concentrations of total estrogen and E(1) were significantly associated with adverse clinical outcome. Intratumoral concentration of total estrogen was significantly associated with the combined status of steroid sulfatase (STS) and estrogen sulfotransferase (EST), but not with that of aromatase. Thus, we subsequently examined the STS/EST status in 328 colon carcinomas using immunohistochemistry. Immunoreactivities for STS and EST were detected in 61% and 44% of the cases, respectively. The -/+ group of the STS/EST status was inversely associated with Dukes' stage, depth of invasion, lymph node metastasis, and distant metastasis and positively correlated with Ki-67 labeling index of the carcinomas. In addition, this -/+ group had significantly longer survival, and a multivariate analysis revealed the STS/EST status as an independent prognostic factor. Results from our present study showed that the STS/EST status of carcinoma tissue determined intratumoral estrogen levels and could be a significant prognostic factor in colon carcinoma, suggesting that estrogens are locally produced mainly through the sulfatase pathway and play important roles in the progression of the disease.

The Role of Androgens in Normal and Malignant Breast Tissue

Androgens, like estrogens, can be synthesized in the breast. As both active androgens and their corresponding receptors are present in breast tissue, we conclude that they play a role in breast physiology. This is supported by the fact that insufficient androgen production or sensitivity results in the development of gynecomastia. Complete androgen insensitivity due to receptor defects leads to normal female breast development in these XY women. While breast development is completely inhibited by male testosterone levels, partial but not total degradation of a developed breast by androgen treatment appears to be possible. Breast cancer in early stages seems to fulfill the prerequisites of androgen responsiveness. Androgen treatment of advanced breast cancer has shown similar effectiveness as anti-estrogen or estrogen-ablative therapy, but also considerable side effects. It has been speculated that the use of selective androgen modulators (SARMs), either alone or preferably in addition to anti-estrogens or aromatase inhibitors, may be a promising alternative to current therapy modalities in hormone-dependent breast cancer. In addition, future studies on the use of SARMs in prophylactic settings seem to be justified.

Aromatase in human breast carcinoma as a key regulator of intratumoral sex steroid concentrations

It is well-known that estrogens are closely involved in the growth of human breast carcinomas, and that the great majority of breast carcinoma express estrogen receptors. Recent studies have demonstrated that estrogens are locally produced and act on the breast carcinoma tissue. Among these pathways, aromatase is a key enzyme for intratumoral production of estrogens in breast carcinomas, and aromatase inhibitors are currently used in the breast carcinoma in postmenopausal women as an estrogen deprivation therapy. This review summarizes the results of recent studies on the expression and regulation of aromatase in breast carcinoma tissues, and discusses the potential biological and/or clinical significance of aromatase. Aromatase is abundantly expressed in various cell types, such as carcinoma cells, intratumoral stromal cells, and adipocytes adjacent to the carcinoma, in breast carcinoma tissues. Further, a key regulator for aromatase expression differed according to cell type. In addition, aromatase suppressed in situ production of bioactive androgen, 5alpha-dihydrotestosterone (DHT), in breast carcinoma. Aromatase inhibitors may thus have additional antiproliferative effects through increasing local DHT concentration with estrogen deprivation.