Breast cancer and hormonal therapy

Role of the Sodium-Dependent Organic Anion Transporter (SOAT/SLC10A6) in Physiology and Pathophysiology

The sodium-dependent organic anion transporter (SOAT, gene symbol SLC10A6) specifically transports 3'- and 17'-monosulfated steroid hormones, such as estrone sulfate and dehydroepiandrosterone sulfate, into specific target cells. These biologically inactive sulfo-conjugated steroids occur in high concentrations in the blood circulation and serve as precursors for the intracrine formation of active estrogens and androgens that contribute to the overall regulation of steroids in many peripheral tissues. Although SOAT expression has been detected in several hormone-responsive peripheral tissues, its quantitative contribution to steroid sulfate uptake in different organs is still not completely clear. Given this fact, the present review provides a comprehensive overview of the current knowledge about the SOAT by summarizing all experimental findings obtained since its first cloning in 2004 and by processing SOAT/SLC10A6-related data from genome-wide protein and mRNA expression databases. In conclusion, despite a significantly increased understanding of the function and physiological significance of the SOAT over the past 20 years, further studies are needed to finally establish it as a potential drug target for endocrine-based therapy of steroid-responsive diseases such as hormone-dependent breast cancer.

Estrone-3-Sulfate Stimulates the Proliferation of T47D Breast Cancer Cells Stably Transfected With the Sodium-Dependent Organic Anion Transporter SOAT (SLC10A6)

Estrogens play a pivotal role in the development and proliferation of hormone-dependent breast cancer. Apart from free estrogens, which can directly activate the estrogen receptor (ER) of tumor cells, sulfo-conjugated steroids, which maintain high plasma concentrations even after menopause, first have to be imported into tumor cells by carrier-mediated uptake and then can be cleaved by the steroid sulfatase to finally activate ERs and cell proliferation. In the present study, expression of the sodium-dependent organic anion transporter SOAT was analyzed in breast cancer and its role for hormone-dependent proliferation of T47D breast cancer cells was elucidated. The SOAT protein was localized to the ductal epithelium of the mammary gland by immunohistochemistry. SOAT showed high expression in different pathologies of the breast with a clear ductal localization, including ductal hyperplasia, intraductal papilloma, and intraductal carcinoma. In a larger breast cancer cDNA array, SOAT mRNA expression was high in almost all adenocarcinoma specimen, but expression did not correlate with either the ER, progesterone receptor, or human epidermal growth factor receptor 2 status. Furthermore, SOAT expression did not correlate with tumor stage or grade, indicating widespread SOAT expression in breast cancer. To analyze the role of SOAT for breast cancer cell proliferation, T47D cells were stably transfected with SOAT and incubated under increasing concentrations of estrone-3-sulfate (E₁S) and estradiol at physiologically relevant concentrations. Cell proliferation was significantly increased by 10^-9 M estradiol as well as by E₁S with EC₅₀ of 2.2 nM. In contrast, T47D control cells showed 10-fold lower sensitivity to E₁S stimulation with EC₅₀ of 21.7 nM. The E₁S-stimulated proliferation of SOAT-T47D cells was blocked by the SOAT inhibitor 4-sulfooxymethylpyrene. In conclusion: The present study clearly demonstrates expression of SOAT in breast cancer tissue with ductal localization. SOAT inhibition can block the E₁S-stimulated proliferation of T47D breast cancer cells, demonstrating that SOAT is an interesting novel drug target from the group of E₁S uptake carriers for anti-proliferative breast cancer therapy.

Effect of calycosin on left ventricular ejection fraction and angiogenesis in rat models with myocardial infarction

OBJECTIVE

To evaluated the effect of calycosin on left ventricular ejection fraction and angiogenesis.

METHODS

Adult male Sprague-Dawley rats were randomly assigned into calycosin-treated groups (0.5, 1, 2, and 4 mg/kg qd), a dimethyl sulfoxide (DMSO), or a sham-operated control group. The myocardial ischaemia (MI) model was intraperitoneally administered calycosin for 28 days. The survival rates and left ventricular ejection fractions (LVEF) were compared between groups. The expression levels of vascular endothelial growth factor (VEGF) and cluster of differentiation 31 (CD31) in ischaemic myocardium were also measured and compared.

RESULTS

The construction of MI model resulted in a LVEF reduction of 50% compared with the sham-control. After 28 days, the LVEF value was 10% higher when calycosin (4 mg/kg) was administered compared with the DMSO group. The expression of VEGF and CD31 showed a dose-dependent manner when calycosin was administrated. The calycosin-treated (4 mg/kg) group displayed a two-fold increase in VEGF expression at both the mRNA and protein levels compared with the DMSO group. In addition, CD31 expression in the microvascular increased 1.5-fold in the 4 mg/kg calycosin-treated group.

CONCLUSION

Calycosin improved left ventricular ejection fraction in the MI rat models, induced VEGF expression in the ischaemic myocardium, increased CD31 expression and promoted angiogenesis.

Percutaneous estradiol/oral micronized progesterone has less-adverse effects and different gene regulations than oral conjugated equine estrogens/medroxyprogesterone acetate in the breasts of healthy women in vivo

Gene expression analysis of healthy postmenopausal women in a prospective clinical study indicated that genes encoding for epithelial proliferation markers Ki-67 and progesterone receptor B mRNA are differentially expressed in women using hormone therapy (HT) with natural versus synthetic estrogens. Two 28-day cycles of daily estradiol (E2) gel 1.5 mg and oral micronized progesterone (P) 200 mg/day for the last 14 days of each cycle did not significantly increase breast epithelial proliferation (Ki-67 MIB-1 positive cells) at the cell level nor at the mRNA level (MKI-67 gene). A borderline significant beneficial reduction in anti-apoptotic protein bcl-2, favouring apoptosis, was also seen followed by a slight numeric decrease of its mRNA. By contrast, two 28-day cycles of daily oral conjugated equine estrogens (CEE) 0.625 mg and oral medroxyprogesterone acetate (MPA) 5 mg for the last 14 days of each cycle significantly increased proliferation at both the cell level and at the mRNA level, and significantly enhanced mammographic breast density, an important risk factor for breast cancer. In addition, CEE/MPA affected around 2,500 genes compared with just 600 affected by E2/P. These results suggest that HT with natural estrogens affects a much smaller number of genes and has less-adverse effects on the normal breast in vivo than conventional, synthetic therapy.

Hormone replacement therapy after breast cancer: 10 year follow up of the Stockholm randomised trial

BACKGROUND

The management of hormonal deficiency symptoms in breast cancer survivors is an unsolved problem. While hormone replacement therapy (HRT) may increase the risk of breast cancer in healthy women, its effects on recurrence is unclear. Observational studies have suggested decreased recurrence rates from HRT. The few clinical trials in this field have all been closed preterm.

METHODS

The Stockholm trial was started in 1997 and designed to minimise the dose of progestogen in the HRT arm. Disease-free women with a history of breast cancer were randomised to HRT (n=188) or no HRT (n=190). The trial was stopped in 2003 when another Swedish study (HABITS, the Hormonal Replacement After Breast Cancer - Is it Safe?) reported increased recurrence. However the Stockholm material showed no excess risk after 4 years of follow-up. A long term follow-up has now been performed.

FINDINGS

After 10.8 years of follow-up, there was no difference in new breast cancer events: 60 in the HRT group versus 48 among controls (hazard ratio (HR)=1.3; 95% confidence interval (CI)=0.9-1.9). Among women on HRT, 11 had local recurrence and 12 distant metastases versus 15 and 12 for the controls. There were 14 contra-lateral breast cancers in the HRT group and four in the control group (HR=3.6; 95% CI=1.2-10.9; p=0.013). No differences in mortality or new primary malignancies were found.

INTERPRETATION

The number of new events did not differ significantly between groups, in contrast to previous reports. The increased recurrence in HABITS has been attributed to higher progestogen exposure. As both trials were prematurely closed, data do not allow firm conclusions. Both studies found no increased mortality from breast cancer or other causes from HRT. Current guidelines typically consider HRT contraindicated in breast cancer survivors. Findings suggest that, in some women symptom relief may outweigh the potential risks of HRT.

Calycosin promotes angiogenesis involving estrogen receptor and mitogen-activated protein kinase (MAPK) signaling pathway in zebrafish and HUVEC

Background

Angiogenesis plays an important role in a wide range of physiological processes, and many diseases are associated with the dysregulation of angiogenesis. Radix Astragali is a Chinese medicinal herb commonly used for treating cardiovascular disorders and has been shown to possess angiogenic effect in previous studies but its active constituent and underlying mechanism remain unclear. The present study investigates the angiogenic effects of calycosin, a major isoflavonoid isolated from Radix Astragali, in vitro and in vivo.

Methodology

Tg(fli1:EGFP) and Tg(fli1:nEGFP) transgenic zebrafish embryos were treated with different concentrations of calycosin (10, 30, 100 µM) from 72 hpf to 96 hpf prior morphological observation and angiogenesis phenotypes assessment. Zebrafish embryos were exposed to calycosin (10, 100 µM) from 72 hpf to 78 hpf before gene-expression analysis. The effects of VEGFR tyrosine kinase inhibitor on calycosin-induced angiogenesis were studied using 72 hpf Tg(fli1:EGFP) and Tg(fli1:nEGFP) zebrafish embryos. The pro-angiogenic effects of calycosin were compared with raloxifene and tamoxifen in 72 hpf Tg(fli1:EGFP) zebrafish embryos. The binding affinities of calycosin to estrogen receptors (ERs) were evaluated by cell-free and cell-based estrogen receptor binding assays. Human umbilical vein endothelial cell cultures (HUVEC) were pretreated with different concentrations of calycosin (3, 10, 30, 100 µM) for 48 h then tested for cell viability and tube formation. The role of MAPK signaling in calycosin-induced angiogenesis was evaluated using western blotting.

Conclusion

Calycosin was shown to induce angiogenesis in human umbilical vein endothelial cell cultures (HUVEC) in vitro and zebrafish embryos in vivo via the up-regulation of vascular endothelial growth factor (VEGF), VEGFR1 and VEGFR2 mRNA expression. It was demonstrated that calycosin acted similar to other selective estrogen receptor modulators (SERMs), such as raloxifene and tamoxifen, by displaying selective potency and affinity to estrogen receptors ERα and ERβ. Our results further indicated that calycosin promotes angiogenesis via activation of MAPK with the involvement of ERK1/2 and ER. Together, this study revealed, for the first time, that calycosin acts as a selective estrogen receptor modulator (SERM) to promote angiogenesis, at least in part through VEGF-VEGFR2 and MAPK signaling pathways.

Sex steroid hormones, hormonal contraception, and the immunobiology of human immunodeficiency virus-1 infection

Worldwide, an increasing number of women use oral or injectable hormonal contraceptives. However, inadequate information is available to aid women and health care professionals in weighing the potential risks of hormonal contraceptive use in individuals living with HIV-1 or at high risk of infection. Numerous epidemiological studies and challenge studies in a rhesus macaque model suggest that progesterone-based contraceptives increase the risk of HIV-1 infection in humans and simian immunodeficiency virus (SIV) infection in macaques, accelerate disease progression, and increase viral shedding in the genital tract. However, because several other studies in humans have not observed any effect of exogenously administered progesterone on HIV-1 acquisition and disease progression, the issue continues to be a topic of intense research and ongoing discussion. In contrast to progesterone, systemic or intravaginal treatment with estrogen efficiently protects female rhesus macaques against the transmission of SIV, likely by enhancing the natural protective properties of the lower genital tract mucosal tissue. Although the molecular and cellular mechanisms underlying the effect of sex steroid hormones on HIV-1 and SIV acquisition and disease progression are not well understood, progesterone and estrogen are known to regulate a number of immune mechanisms that may exert an effect on retroviral infection. This review summarizes current knowledge of the effects of various types of sex steroid hormones on immune processes involved in the biology of HIV-1 infection.

Metastatic phenotype is regulated by estrogen in thyroid cells

BACKGROUND

Over 200 million people worldwide are affected by thyroid proliferative diseases, including cancer, adenoma, and goiter, annually. The incidences of thyroid malignancies are three to four times higher in women, suggesting the possible involvement of estrogen. Based on this observed sex bias, we hypothesize that estrogen modulates the growth and metastatic propensity of thyroid cancer cells.

METHODS

In this study, two thyroid cell lines (Nthy-ori 3-1 and BCPAP) were evaluated for the presence of estrogen receptor (ER) by Western blot analysis and estrogen responsiveness by using a cell proliferation assay. In addition, the effect of estradiol (E(2)) on modulation of metastatic phenotype was determined by using in vitro adhesion, migration, and invasion assays.

RESULTS

Thyroid cells expressed a functionally active ER-alpha and ER-beta as evidenced by 50-150% enhancement of proliferation in the presence of E(2). E(2) also enhanced adhesion, migration, and invasion of thyroid cells in an in vitro experimental model system that, based on our results, is modulated by beta-catenin.

CONCLUSION

Our data provide evidence that the higher incidence of thyroid cancer in women is potentially attributed to the presence of a functional ER that participates in cellular processes contributing to enhanced mitogenic, migratory, and invasive properties of thyroid cells. These findings will enable and foster the possible development of antiestrogenic therapy targeting invasion and migration, thus affecting metastatic propensity.

The effect of Telmisartan on collagen biosynthesis depends on the status of estrogen activation in breast cancer cells

PPAR-gamma and estrogen receptor belong to a family of nuclear hormone receptors that were shown to affect transcriptional activity of each other. The angiotensin II type 1 receptor antagonist Telmisartan is a well known PPAR-gamma ligand. The effect of Telmisartan-induced PPAR-gamma activation on collagen biosynthesis was studied in the estrogen-dependent (MCF-7 cells expressing alpha and beta receptors) and estrogen-independent (MDA-MB 231, expressing only beta receptor) cell lines. We have found that the presence of estrogen in growth medium (2nM) augmented collagen biosynthesis in both cell lines. An addition to the growth medium of PPAR-gamma agonist, Telmisartan, but not rosiglitazone or clofibrat, other PPAR-gamma agonists, induced inhibition of collagen biosynthesis in MCF-7 cells, cultured in the presence of estrogen, while it had no effect on collagen biosynthesis in MDA-MB-231 cells. On the other hand, Telmisartan induced stimulation of collagen biosynthesis in MCF-7 cells cultured in the absence of estrogen (or in conditions of estrogen receptor removal by ICI 182-780-dependent degradation) and had no effect on similarly cultured MDA-MB-231 cells. The effect of Telmisartan on collagen biosynthesis was found specific for PPAR-gamma and not for angiotensin II type 1 since Losartan (specific antagonist of angiotensin II type 1 receptor) in the presence of estradiol did not induce inhibition of this protein in MCF-7 cells. The mechanism of the inhibition was found at the level of NF-kB (known inhibitor of collagen gene expression) and MAPK signaling. PPAR-gamma ligands stimulated expression of NF-kB, while they inhibited expression of p-38 but not ERK1/ERK2. The data suggest that the effect of Telmisartan on collagen biosynthesis in breast cancer cells depends on the status of estrogen receptor activation and the inhibitory effect of Telmisartan on the process requires functional alpha estrogen receptor.

Insulin receptor substrate 2 plays important roles in 17beta-estradiol-induced bone formation

BACKGROUND

Discovering the mechanisms of the estrogen effects on the osteoblasts is very important for the development of new agents which have the clear-cut beneficial effects of estrogen while free of adverse effect.

AIM

The aim of this study was to investigate the differential gene expression of 17beta-estradiol (E2)-treated osteoblast-like cells, and the effect of E2 on the insulin receptor substrate 2 (IRS- 2) expression in human cultured osteoblast-like cells and the osteoblasts of ovariectomized (OVX) rats.

MATERIAL AND METHODS

The differential gene expression of E2-treated osteoblast- like cells was analyzed by cytokine expression array and validated by RT-PCR and Western blot analysis. The protein expression and phosphorylation of one of the differentially expressed gene, IRS-2, treated at different times with E2 were analyzed. The Sprague-Dawley rats were ovariectomized and then treated with E2, the IRS-2 expression was analyzed by immunohistochemistry analysis.

RESULTS

E2 upregulated the mRNA expression of IRS-2, bone morphogenetic protein 9, and connective tissue growth factor expression, down-regulated the mRNA expression of matrix metalloproteinase 15 and some tumor suppressor genes. Peak expression of IRS-2 was observed at 12-24 h of treatment by 10-8M E2. E2 can also increase the phosphorylation of IRS-2. The IRS-2 expression was down-regulated in the osteoblasts and bone marrow cells of the OVX rats, which had lower bone mineral density (BMD) than the normal rats. However, both BMD and IRS-2 expression can be rescued by 10-8M E2 in the OVX rats.

CONCLUSION

IRS-2 in osteoblast is up-regulated by E2 and plays important roles in the estrogen- induced bone formation.

GPR30 predicts poor survival for ovarian cancer

OBJECTIVES

GPR30 is a 7-transmembrane G protein-coupled estrogen receptor that functions alongside traditional estrogen receptors to regulate cellular responses to estrogen. Recent studies suggest that GPR30 expression is linked to lower survival rates in endometrial and breast cancer. This study was conducted to evaluate GPR30 expression in ovarian tumors.

METHODS

GPR30 expression was analyzed using immunohistochemistry and archival specimens from 45 patients with ovarian tumors of low malignant potential (LMP) and 89 patients with epithelial ovarian cancer (EOC). Expression, defined as above or below the median (intensity times the percentage of positive epithelial cells) was correlated with predictors of adverse outcome and survival.

RESULTS

GPR30 expression above the median was observed more frequently in EOC than in LMP tumors (48.3% vs. 20%, p=0.002), and in EOC was associated with lower 5-year survival rates (44.2% vs. 82.6%, Log-rank p<0.001). Tumor grade and FIGO stage, the other significant predictors of survival, were used to stratify cases into "high risk" and "low risk" groups. The 5-year survival rate for "low risk" EOC (all grade 1 and Stage I/II, grade 2) was 100%. In "high risk" EOC (all grade 3 and Stage III/IV, grade 2), the difference in 5-year survival by GPR 30 expression was significant (33.3% vs. 72.4%, p=0.001).

CONCLUSIONS

The novel estrogen-responsive receptor GPR30 is preferentially expressed in "high risk" EOC and is associated with lower survival rates. Further investigation of GPR30 as a potential target for therapeutic intervention in high risk EOC is warranted.