ERalpha Protein Expression Research Articles

Abstract 2562: eIF4E modulators to address breast cancer resistance

Abstract ER+/HER2- advanced or metastatic breast cancers represents a large patient population served by CDK4/6 inhibitors combined with hormonal therapy as standard of care. As acquired resistance emerges, molecular profiling indicates about > 100 different mutations render resistance, creating challenges for treating physicians, patients, and the healthcare system broadly. The aim of our work is to maintain consolidation of this large patient population by developing targeted therapies to a key fundamental mechanism at the convergence of many oncogenic signaling pathways through which resistance arises. The regulation of CAP dependent protein translation is a central element in oncogenesis. One of a family of CAP binding proteins, eIF4E serves to anchor the m7GTP CAP of RNA into several protein complexes and regulates multiple aspects of mRNA processing such as nuclear export and ribosomal translation. Our efforts focused on simultaneously developing potent small molecule modulators of eIF4E and patient hypotheses through which to direct their initial clinical use. By aligning medicinal chemistry tools with patient directed pharmacology, we optimized our inhibitors to identify orally bioavailable, nM modulators of eIF4E. Biochemical assays demonstrated direct binding and allosteric modulation of eIF4E activity by PICRN941, along with Proximity Ligation Assays (PLA) demonstrating reduced eIF4E and 4G association in cells. Western analysis demonstrated that PICRN941 induced simultaneous and significant modulation of a number of key oncogenes that have been postulated to drive intrinsic or acquired resistance in response to standard of care including anti-estrogen treatment, CDK4/6 inhibitors or PI3K inhibitors combined with hormonal therapy, including MYC, CDK2, CDK4, CCND1 and eIF4E itself. Treatment of ER+ breast cancer cell lines including ZR-75-1, T47D, and ZR-75-30 with PICRN941 induced a dose dependent reduction in the levels of hyper-phosphorylated 4E-BP1 commensurate to increases in unphosphorylated 4E-BP1, and dose-dependent reduction in protein expression of Cyclin D1, CDK4, ER alpha, phosphorylated Rb and eIF4E. Reduced protein expression correlated with subsequent cell cycle arrest and apoptosis. We further studied our inhibitors in primary patient derived organoids in collaboration with the Hubrecht Institute, where we observed potent and complete responses in breast cancer organoids that represent patient populations where unmet needs remain high including PTEN and RB null organoid models. Markers of target engagement correlated well with organoid model sensitivity, including Cyclin D1 responses. Our findings suggest that our allosteric eIF4E modulators may provide a unique and efficient therapeutic approach to address multiple resistance mechanisms across cancer patient populations, toward fulfilling the promise of this elusive target. Citation Format: Lisa Sturla, Bassil Dekky, Xuemei Zhang, Katherine S. Bowdish, Chris VanDeusen. eIF4E modulators to address breast cancer resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2562.

Mechanism of 17β-estradiol stimulated integration of human mesenchymal stem cells in heart tissue

Scarcity of gender specific donor hearts highlights the importance of mesenchymal stem cells (MSCs) as a therapeutic tool for heart repair. However, inefficient incorporation, retention, and activity of MSCs in cardiac tissue remain an obstacle. Since surges in follicular estradiol (E2; μmolar-range) trigger tissue remodeling (e.g. ovulation) and E2 exerts beneficial actions on the cardiovascular system, we hypothesized that E2 may promote/improve MSC-mediated cardiac repair processes. Using Wharton's jelly (WJ)-derived MSCs we assessed the effects of E2 on MSC proliferation, directed migration, and engraftment in murine heart slices (using xCELLigence real-time cell-impedance system, DNA quantification, and microscopy) and on MSC-induced angiogenesis in vivo (matrigel plug assay). Protein expression was assessed by Western blotting, ELISA/Luminex, and proteomic analysis; whereas mRNA expression was assessed by qRT-PCR. MSCs expressed estrogen receptors (ERs) -alpha and -beta. E2 promoted MSC proliferation and up-regulated mRNA and protein expression of ER-alpha, ER-beta, extracellular matrix metalloproteinase inducer (EMMPRIN), and matrix metalloproteinase (MMP) -9, yet down-regulated MMP-2 expression. Moreover, E2 up-regulated expression of vascular endothelial growth factor (VEGF)-A, VEGFR-2, vascular cell adhesion protein-1 (VCAM-1), and angiogenin (ANG) and stimulated nitric oxide (NO) production via ER. Proteomic analysis of MSCs showed that E2 up-regulated 47 proteins, down-regulated 7 proteins, and increased the expression of key biochemical components/pathways involved in tissue repair. In MSCs co-cultured with murine heart-slices, E2 significantly induced MSC migration in an ER-alpha-dependent fashion and significantly increased the secretion of MMP-2, MMP-9, ANG, and VEGF. In an in vivo matrigel assay, E2-treated MSCs increased angiogenesis and hemoglobin content. In conclusion, E2-treatment increases the incorporation of MSCs in heart slices and promotes MSC-induced angiogenesis. These beneficial effects are mediated via increases in molecules/pathways involved in tissue remodeling and angiogenesis. We speculate that E2 may enhance MSC ability to repair/regenerate cardiac tissue.

SMURF1 facilitates estrogen receptor \u0251 signaling in breast cancer cells

BackgroundEstrogen receptor alpha (ER alpha) is expressed in the majority of breast cancers and promotes estrogen-dependent cancer progression. ER alpha positive breast cancer can be well controlled by ER alpha modulators, such as tamoxifen. However, tamoxifen resistance is commonly observed by altered ER alpha signaling. Thus, further understanding of the molecular mechanisms, which regulates ER alpha signaling, is important to improve breast cancer therapy.MethodsSMURF1 and ER alpha protein expression levels were measured by western blot, while the ER alpha target genes were measured by real-time PCR. WST-1 assay was used to measure cell viability; the xeno-graft tumor model were used for in vivo study. RNA sequencing was analyzed by Ingenuity Pathway Analysis. Identification of ER alpha signaling was accomplished with luciferase assays, real-time RT-PCR and Western blotting. Protein stability assay and ubiquitin assay was used to detect ER alpha protein degradation. Immuno-precipitation based assays were used to detect the interaction domain between ER alpha and SMURF1. The ubiquitin-based Immuno-precipitation based assays were used to detect the specific ubiquitination manner happened on ER alpha.ResultsHere, we identify the E3 ligase SMURF1 facilitates ER alpha signaling. We show that depletion SMURF1 decreases ER alpha positive cell proliferation in vitro and in vivo. SMURF1 depletion based RNA-sequence data shows SMURF1 is necessary for ER alpha target gene expression in the transcriptomic scale. Immunoprecipitation indicates that SMURF1 associates with the N-terminal of ER alpha in the cytoplasm via its HECT domain. SMURF1 increases ER alpha stability, possibly by inhibiting K48-specific poly-ubiquitination process on ER alpha protein. Interestingly, SMURF1 expression could be induced via estradiol treatment.ConclusionsOur study reveals a novel positive feedback between SMURF1 and ER alpha signaling in supporting breast cancer growth. Targeting SMURF1 could be one promising strategy for ER alpha positive breast cancer treatment.

Synthesis and mechanistic aspects of 2-anilinonicotinyl-pyrazolo[1,5-a]pyrimidine conjugates that regulate cell proliferation in MCF-7 cells via estrogen signaling

A series of anilinonicotinyl linked pyrazolo[1,5-a]pyrimidine conjugates (6a–x) were synthesized and evaluated for their antiproliferative activity. Some of these conjugates exhibited promising cytotoxic effects in the MCF-7 cell line and among these 6a and 6c exhibited significant effects, apart from G2/M cell cycle arrest. Interestingly they showed profound effects on cyclin D1, Bcl-2 and survivin proteins that regulate breast cancer cell proliferation. Moreover, ER alpha protein expression was studied to understand regulatory role of these conjugates on estrogen activity in estrogen positive breast cancer cells like MCF-7 and compounds 6a and 6c reduced their activity.

Triptolide inhibits cell proliferation by downregulating phosphorylation of estrogen reporters in 4T1 tumor-bearing mice

In order to investigate the anti-proliferative effects of triptolide (TP) on 4T1 mice breast cancer cell line in vitro and in mouse model, as well as the possible mechanisms, we detected the effect of TP on cell proliferation by MTT assay or Crystal Violet Staining in our research. Flowcytometry combined with FITC-Annexin V/PI staining were used for detecting TP induced 4T1 cell apoptosis. The protein expression of ERalpha, p-ERalpha, ERbeta, p-ERbeta, ERK, p-ERK, p38, p-p38, SAPK/JNK, and p-SAPK/JNK was tested by western blotting. We also compare TP with chemotherapy drug doxorubicin in 4T1 tumor bearing BLAB/c mice model, the Xenogen bioluminescence imaging, H&E, and IHC result indicated that TP exhibits an anticancer proliferation activity. As a result, TP in 100, 10, 1, 0.1 micromol x L(-1), all inhibited the proliferation of 4T1 cells by MTT assay and Crystal Violet Staining. TP which concentrations is 10, 1, 0.1 micromol x L(-1) could induce the apoptosis of 4T1 cells and reduce the cell proliferation. TP in 200 microg x kg(-1) could inhibit the tumor growth in vivo. The anticancer proliferation of TP was involved in its effect on reducing expression of ERalpha, p-ERalpha, ERbeta, and p-ERbeta, but nothing to do with the activation of MAPK signaling pathway.

Alteration in expression of estrogen receptor isoforms alpha and beta, and aromatase in the testis and its relation with changes in nitric oxide during aging in mice

The aim of present study was to investigate the changes in the testicular expression of aromatase, ER alpha, ER beta and iNOS protein and correlate these with serum testosterone and nitric oxide levels, to elucidate the role of estrogen and nitric oxide in the testis during aging. This study showed localization of aromatase and ER alpha mainly in the Leydig cell and showed close correlation of testicular aromatase level with circulating testosterone level suggesting that estrogen may be modulating testicular steroidogenesis. Localization ER alpha mainly in the mitotically active germ cell suggest possible role of estrogen in germ cell proliferation. This study showed basal level of nitric oxide during reproductively active period, whereas increased serum nitric oxide coincides with decreased testicular activity in old age. This study showed inverse correlation between aromatase and NO level. Treatment with either SNP or L-NAME on testicular steroidogenic factor (3-beta HSD/ StAR) or germ cell survival factor (Bcl2) showed that increased NO causes decreased steroidogenesis and increased germ cell apoptosis. In conclusion this study suggest that estrogen modulate steroidogenesis and germ cell survival in reproductively active period whereas in old age decreased estrogen concentration causes increased nitric oxide which in turn decreases testicular steroidogenesis and germ cell apoptosis.

ShRNA-mediated gene silencing of MTA1 influenced on protein expression of ER alpha, MMP-9, CyclinD1 and invasiveness, proliferation in breast cancer cell lines MDA-MB-231 and MCF-7 in vitro

BackgroundMTA1(metastasis associated-1) is a tumor metastasis associated candidate gene and overexpression in many human tumors, including breast cancer. In this study, we investigated depressive effect on MTA1 by MTA1-specific short hairpin RNA(shRNA) expression plasmids in human breast cancer cell lines MDA-MB-231 and MCF-7, and effect on protein levels of ER alpha, MMP-9, cyclinD1, and tumor cell invasion, proliferation.MethodsShRNA expression vectors targeting MTA1 was constructed and transfected into human breast cancer cell lines MDA-MB-231 and MCF-7. The transfection efficiency was evaluated by fluorescence microscopy, mRNA levels of MTA1 were detected by reverse transcription-polymerase chain reaction (RT-PCR), protein levels of ER alpha, MMP-9 and cyclinD1 were detected by Western blotting, respectively. Tumor cells invasive ability were evaluated by Boyden chamber assay, the cells proliferation were evaluated using cell growth curve and MTT analysis, the cell cycle analysis was performed using flow cytometry.ResultsDown-regulation of MTA1 by RNAi approach led to re-expression of ER alpha in ER-negative breast cancer cell lines MDA-MB-231, and reduced protein levels of MMP-9 and CyclinD1, as well as decreased tumor cell invasion and proliferation, more cells were blocked in G0/G1 stage(P < 0.05). However, after inhibiting mRNA levels of MTA1, protein expression of ER alpha, MMP-9, cyclinD1 and the changes of cancer cells invasiveness, proliferation, cells cycle were no statistical difference in ER-positive human breast cancer cell lines MCF-7 (P > 0.05).ConclusionsShRNA targeted against MTA1 could specifically mediate the MTA1 gene silencing and consequentially recover the protein expression of ER alpha, resulting in increase sensitivity of antiestrogens, as well as suppress the protein levels of MMP-9 and cyclinD1 in ER-negative human breast cancer cell lines MDA-MB-231. Silencing effect of MTA1 could efficiently inhibit the invasion and proliferation in MDA-MB-231 cells. The shRNA interference targeted against MTA1 may have potential therapeutic utility in human breast cancer.

Effect of ferulic acid on proliferation and mechanism in human breast cancer cells

To investigate phytoestrogenic effects of ferulic acid in ER-positive T47D and ER-negative MDA-MB231 cells in culture. T47D and MDA-MB231 human breast cancer cells were treated with ferulic acid and examined cell proliferation by means of MTT assay. Cell cycle distribution, ERalpha and ERbeta expression were treated by flow cytometer. The pS2 mRNA expressions were detected by real-time fluorescence quantitative PCR. The proliferations were enhanced significantly by treatment with ferulic acid on T47D cells and the proliferation effects were inhibited by adding Faslodex (1 x 10(-8) mol x L(-1)). However, there was no significant difference on the proliferation in MDA-MB-231 cells compared with solvent control group by both treatment with ferulic acid and co-treatment with Faslodex (1 x 10(-8) mol x L(-1)). Ferulic acid stimulated the amount of T47D cells in phase S and proliferation index increased significantly. The effects were inhibited by treatment with Faslodex (1 x 10(-8) mol x L(-1)), and the amount of cells in phase S and proliferation index decreased, the amount of cells in G0/G1 phase increased, cell cycle of T47D was arrested in G0/G1 phase. Ferulic acid up-regulated pS2 mRNA expressions and increased the level of ERalpha protein expression in T47D cells. Ferulic acid did not show remarkable effect to the level of ERbeta protein expression in T47D cells. Ferulic acid possessed phytoestrogenic effect by up-regulating pS2 gene expression and the receptor subtype of ERalpha.

Changes in Oestrogen Receptor α Expression in the Nucleus of the Solitary Tract of the Rat Over the Oestrous Cycle and Following Ovariectomy

Oestrogen is capable of modulating autonomic outflow and baroreflex function via actions on groups of neurones in the brainstem. We investigated the presence of oestrogen receptor (ER) alpha in a part of the nucleus of the solitary tract (NTS) associated with central cardiovascular control, aiming to determine whether ERalpha mRNA and protein expression is correlated with levels of circulating oestrogen during the oestrous cycle. Polymerase chain reaction (PCR) detected ERalpha mRNA in the NTS at each stage of the oestrous cycle, from ovariectomised, sham-operated and male rats. Real-time PCR showed variations in ERalpha mRNA expression during the oestrous cycle, with the highest levels seen in oestrus, and lowest levels in metoestrus (P < 0.05 versus oestrus) and proestrus (P < 0.05 versus oestrus). Expression in males was lower than in dioestrus and oestrus females (P < 0.05). After ovariectomy, ERalpha mRNA levels were decreased compared to sham-operated animals (P < 0.01). Confocal fluorescence immunohistochemistry with stereological analysis showed that numbers of ERalpha immunoreactive cell nuclei per mm(3) of tissue in the caudal NTS were significantly greater in proestrus than in other groups of rats (P < 0.05). There were also differences among the groups in the extent of colocalisation of ERalpha in neurones immunoreactive for tyrosine hydroxylase and nitric oxide synthase. These results imply a complex pattern of region-specific oestrogen signalling in the NTS and suggest that ERalpha expression in this important autonomic nucleus may be related to circulating oestrogen levels. This may have consequences for the regulation of autonomic tone and baroreflex sensitivity when oestrogen levels decline, for example following menopause.

Estrogen Regulates Estrogen Receptors and Antioxidant Gene Expression in Mouse Skeletal Muscle

BackgroundEstrogens are associated with the loss of skeletal muscle strength in women with age. Ovarian hormone removal by ovariectomy in mice leads to a loss of muscle strength, which is reversed with 17β-estradiol replacement. Aging is also associated with an increase in antioxidant stress, and estrogens can improve antioxidant status via their interaction with estrogen receptors (ER) to regulate antioxidant gene expression. The purpose of this study was to determine if ER and antioxidant gene expression in skeletal muscle are responsive to changes in circulating estradiol, and if ERs regulate antioxidant gene expression in this tissue.Methodology/Principal FindingsAdult C57BL/6 mice underwent ovariectomies or sham surgeries to remove circulating estrogens. These mice were implanted with placebo or 17β-estradiol pellets acutely or chronically. A separate experiment examined mice that received weekly injections of Faslodex to chronically block ERs. Skeletal muscles were analyzed for expression of ER genes and proteins and antioxidant genes. ERα was the most abundant, followed by Gper and ERβ in both soleus and EDL muscles. The loss of estrogens through ovariectomy induced ERα gene and protein expression in the soleus, EDL, and TA muscles at both the acute and chronic time points. Gpx3 mRNA was also induced both acutely and chronically in all 3 muscles in mice receiving 17β-estradiol. When ERs were blocked using Faslodex, Gpx3 mRNA was downregulated in the soleus muscle, but not the EDL and TA muscles.Conclusions/SignificanceThese data suggest that Gpx3 and ERα gene expression are sensitive to circulating estrogens in skeletal muscle. ERs may regulate Gpx3 gene expression in the soleus muscle, but skeletal muscle regulation of Gpx3 via ERs is dependent upon muscle type. Further work is needed to determine the indirect effects of estrogen and ERα on Gpx3 expression in skeletal muscle, and their importance in the aging process.

An estrogen receptor α suppressor, microRNA‐22, is downregulated in estrogen receptor α‐positive human breast cancer cell lines and clinical samples

Previous studies have suggested that microRNAs (miRNAs) may play important roles in tumorigenesis, but little is known about the functions of most miRNAs in cancer development. In the present study, we set up a cell-based screen using a luciferase reporter plasmid carrying the whole approximately 4.7 kb 3'-UTR of estrogen receptor alpha (ERalpha) mRNA cotransfected with a synthetic miRNA expression library to identify potential ERalpha-targeting miRNAs. Among all the miRNAs, miR-22 was found to repress robustly the luciferase signal in both HEK-293T and ERalpha-positive MCF-7 cells. Mutation of the target site was found to abrogate this repression effect of miR-22, whereas antagonism of endogenous miR-22 in MDA-MB-231 cells resulted in elevated reporter signals. We assessed the miR-22 expression patterns in five breast cancer cell lines and 23 clinical biopsies and revealed that there is a significant inverse association between the miR-22 levels and ERalpha protein expression. To evaluate the potential of miR-22 as a potential therapeutic intervention, we found that reduction of endogenous ERalpha protein levels and suppression of cancer cell growth could be achieved in MCF-7 cells by miR-22 overexpression in a way that can be recapitulated by the introduction of specific small interfering RNA against ERalpha. The phenomena can be rescued by the reintroduction of ERalpha. Taken together, our data indicate that miR-22 was frequently downregulated in ERalpha-positive human breast cancer cell lines and clinical samples. Direct involvement in the regulation of ERalpha may be one of the mechanisms through which miR-22 could play a pivotal role in the pathogenesis of breast cancer.

Methylation status of oestrogen receptor α-A: a predictor of prognosis in leukaemias

Many studies have shown that epigenetic regulation of ERs (oestrogen receptors) plays a key role in the pathogenesis of leukaemia. In the present study, it was found that the methylated status of ERalpha-A might serve as an epigenetic biomarker of leukaemias. In this study, the protein expression and cell apoptosis, cycle, proliferation and viability with and without 5-aza-dC (5-aza-2'-deoxycytidine) were evaluated with Western blotting, 3H-TdR (3H-thymidine) incorporation, propidium iodide staining and Trypan Blue staining respectively. The protein expression of ERalpha was significantly enhanced in all leukaemic cell lines using treatment with the DNA demethylation reagent 5-aza-dC. However, no obvious change in the protein expression of ERbeta takes place with 5-aza-dC. And with 5-aza-dC, cell apoptosis, cell cycle, cell proliferation and viability were all inhibited significantly. We also tracked 40 cases of leukaemias with ERalpha-A methylation (95%; 38 of 40) to observe the prognosis 1 year after chemotherapy treatment. The patients with ERalpha-A methylation have no obvious symptomatic relief; however, two patients without ERalpha-A methylation have obtained effective relief. This result suggested that ERalpha plays a significant role in leukaemogenesis, and the methylated status of ERalpha-A not only might serve as an epigenetic biomarker of leukaemias for diagnosis, but also has the potential to serve as a predictor of prognosis in leukaemias.

Prostaglandin E2 Induces CYP1B1 Expression via Ligand-Independent Activation of the ERα Pathway in Human Breast Cancer Cells

Breast cancer is a major cause of death worldwide. Human cytochrome P450 (CYP) 1B1 is a key enzyme in the metabolism of 17beta-estradiol, and CYP1B1-metabolized 4-hydroxyestradiol is a marker for breast cancer. Furthermore, overexpression of cyclooxygenase-2 (COX-2), which produces prostaglandin E(2) (PGE(2)), has been detected in invasive breast carcinomas. However, the interaction between PGE(2) and CYP1B1 expression in human breast cancer is unclear. Here, we investigated the effect of PGE(2) on CYP1B1 expression and its mechanism in breast cancer cells. PGE(2) significantly increased CYP1B1 protein and messenger RNA expression and dose dependently enhanced CYP1B1 promoter activity in human breast cancer MCF-7 cells. Transient transfection with human CYP1B1 (hCYP1B1) deletion promoter constructs and cotreatment with inhibitors revealed that the estrogen response element contributed to the effects of PGE(2). CYP1B1 expression was not affected by PGE(2) in estrogen receptor (ER) alpha-negative MDA-MB-231 breast cancer cells or in ERalpha/beta-negative MCF-10A normal breast cells, and protein expression of ERalpha and ERbeta was not affected by PGE(2) treatment in MCF-7 cells. However, PGE(2) rapidly induced phosphorylation of ERalpha at serine residues 118, 167, and 305, suggesting that PGE(2) activates ERalpha in a ligand-independent manner. PGE(2) also increased phosphorylation of extracellular signal-regulated kinase (ERK), Akt, and protein kinase A (PKA). Finally, a COX-2 inhibitor inhibited PGE(2)-induced CYP1B1 expression, and COX-2 overexpression increased CYP1B1 expression. Our results indicate that PGE(2)-induced CYP1B1 expression is mediated by ligand-independent activation of the ERalpha pathway as a result of the activation of ERK, Akt, and PKA in breast cancer cells.

Estrogenic Effects of the Herbal Formula, Menoprogen, in Ovariectomized Rats

Despite the health risks for postmenopausal women, the indications and ideal candidates for hormone replacement therapy remain unclear. The present study used ovariectomized rats to examine the safety and effects of the Chinese herbal formula Menoprogen (MPG), which is prescribed for menopausal syndrome. Daily oral MPG (1000 mg/kg body weight) for 2 weeks significantly recovered uterine and adrenal gland atrophy and restored serum estradiol, estrone and progesterone levels that were decreased in rats by bilateral ovariectomy. However, yeast two-hybrid and nuclear receptor cofactor assays showed that MPG did not bind estrogen receptors alpha (ERalpha) and beta, and immunohistochemical staining revealed that unlike 17beta-estradiol, MPG did not stimulate the protein expression of ERalpha, progesterone receptor, c-jun and c-fos in the uterus. No side effects of MPG were confirmed in vivo. These findings suggest that MPG would be useful for treating women with premenopausal and postmenopausal syndromes.

The effects of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin on foetal male rat steroidogenesis

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is the most toxic and widely investigated dioxin congener. In utero and lactational exposure to TCDD results in developmental and reproductive defects that are the most sensitive endpoints for TCDD toxicity. TCDD has a potential to interfere with steroid metabolism, but the mechanisms by which this occurs are not well understood. In this study, we investigated the effects of TCDD on prenatal rat steroidogenesis. Pregnant Sprague-Dawley female rats were treated once with TCDD (0, 0.3 or 1 microg/kg) by gavage on embryonic day (ED) 11 and the expression levels of androgen (AR) and estrogen receptors (ER), steroidogenic enzymes (P450scc and 3beta-HSD) and four regulatory factors (StAR, SF-1, GATA-4 and Insl-3) involved in foetal Leydig cell and adrenal function were analysed on ED 19.5. Hormonal status of male foetuses was determined by measuring testicular testosterone (T) levels, plasma luteinizing hormone (LH) and corticosterone concentrations. In utero exposure to TCDD reduced intratesticular T of foetal males (significant at 0.3 microg/kg TCDD) and tended to reduce the protein expression of ERalpha and AR of foetal male rat testis. Foetal male rat plasma LH levels were significantly reduced at the dose of 1 microg/kg TCDD, while corticosterone levels tended to be increased possibly because of the TCDD-induced stress. Only minor alterations in steroidogenesis were observed in rat adrenal. mRNA expression of developmental regulatory factors was not influenced by foetal TCDD exposure, except for significantly reduced adrenal SF-1. The results demonstrate that maternal exposure to TCDD suppressed testicular steroidogenesis of 19.5-day-old foetal male Sprague-Dawley rat. The highest dose of TCDD (1 microg/kg) had also an effect on pituitary LH secretion. Our data implicate that TCDD has direct testicular and pituitary effects on foetal male rat but with different dose-responses. These changes can lead to impaired steroidogenesis and it may result in the maldevelopment of the testis and weaken masculinization.

Progesterone receptors A and B and estrogen receptor alpha expression in normal breast tissue and fibroadenomas

Fibroadenomas are the most common benign breast tumors, occurring mainly in young women. Their responses to the hormonal environment are similar to those of normal breast tissue, which suggests that steroid receptors may play a role in tumor development. We evaluated the gene and protein expression of progesterone receptors A and B (PRA and PRB) and the protein expression of estrogen receptor alpha (ER-alpha) in fibroadenoma samples, comparing with adjacent normal breast tissue, from 11 premenopausal women. Progesterone and estradiol levels were determined. No alterations in the PRs gene and protein expression and the ER-alpha protein expression were observed between the follicular and luteal phases, in normal breast versus fibroadenomas. Protein levels of PRA and PRB were higher in fibroadenomas compared to normal breast tissue (P = 0.038 and P = 0.031), while the PRs mRNA levels were similar in both tissues (P = 0.721 and P = 0.139). There were no differences in ER-alpha protein expression between normal breast tissue and fibroadenomas (P = 0.508). The PRA:PRB ratio was similar in the tissues, and also showed a strong correlation in both (r = 0.964, P = 0.0001). Our data suggest a role of PRs in the growth and development of fibroadenomas, although without alterations of the PRA:PRB ratio in these tumors. The absence of alterations in ER-alpha protein levels could be a characteristic behavior of fibroadenomas, unlike breast cancer.

Mouse mammary tumour virus-like virus (MMTV-LV) is present within the liver in a wide range of hepatic disorders and unrelated to nuclear p53 expression or hepatocarcinogenesis

The human equivalent of mouse mammary tumour virus (MMTV-LV) may have a role in the pathogenesis of primary biliary cirrhosis (PBC) and breast carcinogenesis. We investigated MMTV-LV prevalence in patients with liver disease of diverse aetiology and associations with hepatic expression of hormonal receptors, p53 protein and complicating hepatocarcinogenesis. Nested PCR for MMTV-LV envelope was performed using tissue from 210 patients with liver disease and 20 patients with histologically normal liver. Hepatic expression of estrogen receptor-alpha (ER-alpha), progesterone receptor (PgR) and p53 protein was determined by immunohistochemistry. MMTV-LV expression was also determined in hepatocellular carcinoma (HCC) tissue from 21 patients, in 11 of whom paired non-tumourous liver tissue was available for comparison. MMTV-LV envelope sequences were present in 25% (53/210) of liver disease biopsies but not in histologically normal liver (0/20) (P=0.02). There was no association between MMTV-LV presence and hepatic expression of ER-alpha or p53 protein. No liver sections were PgR positive. MMTV-LV prevalence was not significantly different in HCC tissue, paired non-tumourous chronic liver disease tissue from the same patients and liver disease tissue from patients without complicating HCC. Hepatic expression of MMTV-LV is evident in a wide range of non-cirrhotic and cirrhotic liver diseases, irrespective of ER-alpha, PgR or p53 status, and unrelated to complicating HCC.

Alteration of the MT1 melatonin receptor gene and its expression in primary human breast tumors and breast cancer cell lines

The MT1 melatonin receptor is bound and activated by the pineal hormone melatonin. This G protein-coupled melatonin receptor is expressed in human breast tumor cell lines, and when activated, mediates the growth-suppressive and steroid hormone/nuclear receptor modulatory actions of melatonin on breast tumor cells. In the current studies, we have examined the expression of the MT1 receptor in breast cancer cell lines and primary human breast tumors and correlated MT1 receptor expression with the deletion, rearrangement and amplification of the MT1 gene and established markers of breast cancer such as tumor size, stage, estrogen receptor alpha (ERalpha) and progesterone receptor (PR) expression. Theses studies suggest amplification of the MT1 gene in some breast tumors and an inverse correlation with ERalpha, PR and MT1 protein expression. Furthermore, these approaches employing immunohistochemical and immunofluorescent/confocal microscopic studies demonstrate that the MT1 receptor is localized to the caveoli and that MT1 expression in MCF-7 breast cancer cells can be repressed by estradiol and melatonin.

MicroRNA-221/222 Negatively Regulates Estrogen Receptorα and Is Associated with Tamoxifen Resistance in Breast Cancer

A search for regulators of estrogen receptor alpha (ERalpha) expression has yielded a set of microRNAs (miRNAs) for which expression is specifically elevated in ERalpha-negative breast cancer. Here we show distinct expression of a panel of miRNAs between ERalpha-positive and ERalpha-negative breast cancer cell lines and primary tumors. Of the elevated miRNAs in ERalpha-negative cells, miR-221 and miR-222 directly interact with the 3'-untranslated region of ERalpha. Ectopic expression of miR-221 and miR-222 in MCF-7 and T47D cells resulted in a decrease in expression of ERalpha protein but not mRNA, whereas knockdown of miR-221 and miR-222 partially restored ERalpha in ERalpha protein-negative/mRNA-positive cells. Notably, miR-221- and/or miR-222-transfected MCF-7 and T47D cells became resistant to tamoxifen compared with vector-treated cells. Furthermore, knockdown of miR-221 and/or miR-222 sensitized MDA-MB-468 cells to tamoxifen-induced cell growth arrest and apoptosis. These findings indicate that miR-221 and miR-222 play a significant role in the regulation of ERalpha expression at the protein level and could be potential targets for restoring ERalpha expression and responding to antiestrogen therapy in a subset of breast cancers.

Role of Estrogen Receptor‐α and −β in Regulating Leptin Expression in 3T3‐L1 Adipocytes

We investigated the effects of the estrogen receptor-alpha (ERalpha) and -beta (ERbeta) in the regulation of leptin, resistin, and adiponectin expression in 3T3-L1 adipocytes. Mature adipocytes were exposed to estradiol (E2), ERalpha agonist (PPT (4,4',4''-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol)), ERbeta agonist (DPN (2,3-bis(4-Hydroxyphenyl)-propionitrile)), E2 with ERalpha antagonist (MPP (1,3-Bis(4-hydroxyphenyl)-4-methyl-5-[4-(2-piperidinylethoxy)phenol]-1H-pyrazole dihydrochloride)), and E2 with ERbeta antagonist (R,R-THC ((R,R)-5,11-diethyl-5,6,11,12-tetrahydro-2,8-chrysenediol)) at different concentrations. To clarify the expression and regulation of adipokines by ER subtypes, total RNA was extracted from cells and measured using quantitative PCR. Western blot analysis was performed to evaluate the protein expression of adipokines, ERalpha, and ERbeta. The leptin expression was significantly increased in the cells treated with high concentrations (10(-5) and 10(-6) mol/l) of the PPT (P < 0.01, P < 0.05). By contrast, the leptin expression decreased in a dose-dependent manner in the MPP-treated groups (P < 0.05). High concentrations (10(-5) mol/l) of R,R-THC with E2 (10(-7) mol/l) caused a significant increase of the leptin expression (P < 0.01). The leptin mRNA levels were positively correlated with the ERalpha mRNA levels (r = 0.584, P < 0.01) and negatively correlated with the ERbeta mRNA levels (r = -0.236, P = 0.03) in the adipocytes. The ratio of the ERalpha to ERbeta mRNA levels in the adipocytes was significantly associated with leptin mRNA levels (r = 0.454, P < 0.01). ERalpha induced leptin expression and ERbeta inhibited its expression in 3T3-L1 adipocytes. The ratio of the ERalpha-to-ERbeta expression in 3T3-L1 adipocytes may be an important potential regulatory factor in leptin expression.