Expression Of SRC-1 Research Articles

Immunohistochemical detection of steroid receptor cofactors in ovarian endometriosis: involvement of down-regulated SRC-1 expression in the limited growth activity of the endometriotic epithelium

To study the steroid hormone-induced growth mechanisms of endometriosis, the immunohistochemical expression of steroid hormone receptor cofactors was investigated in 37 cases of endometriotic epithelia and was compared with that of eutopic endometria of identical patients. The expression of steroid receptor coactivators (p300/CBP and SRC-1) and corepressors (NCoR and SMRT) was examined in relation to the estrogen receptor (ER), the progesterone receptor (PR), and Ki-67. Results of immunostaining were indicated as a "positivity index" (PI, full score; 100). The expression of ER and PR in endometriotic epithelia largely resembled that in eutopic endometria, however, the expression of Ki-67 in the proliferative phase (PI 13.8 +/- 2.4, mean +/- SD) was significantly lower than that in eutopic endometria (32.6 +/- 10.6). The expression of SRC-1 in eutopic endometria was increased in the proliferative phase (56.5 +/- 16.8) and decreased in the secretory phase (14.8 +/- 6.9). In endometriosis, however, the PI for SRC-1 did not show apparent cyclic changes during the menstrual cycle. Moreover, the expression of SRC-1 in endometriotic epithelia in the proliferative phase was significantly lower than that in eutopic endometria. These findings suggested the reduced proliferative activity in endometriotic epithelia to be related to the reduced expression of SRC-1.

The role of oestrogen receptor α in human thyroid cancer: contributions from coregulatory proteins and the tyrosine kinase receptor HER2

Epidemiological, clinical, and molecular studies suggest a role for oestrogen in thyroid cancer. How oestrogen mediates its effects and the consequence of it on clinical outcome has not been fully elucidated. The participation of coregulatory proteins in modulating oestrogen receptor (ER) function and input of crosstalk with the tyrosine kinase receptor HER2 was investigated. Oestrogen induced cell proliferation in the follicular thyroid cancer (FTC)-133 cells, but not in the anaplastic 8305C cell line. Knockdown of the coactivator steroid receptor coactivator (SRC)-1 inhibited FTC-133 basal, but not oestrogen induced, cell proliferation. Oestrogen also increased protein expression of SRC-1 and the ER target gene cyclin D1 in the FTC-133 cell line. ERalpha, ERbeta, the coregulatory proteins SRC-1 and nuclear corepressor (NCoR), and the tyrosine kinase receptor HER2 were localised by immunohistochemistry and immnofluorescence in paraffin-embedded tissue from thyroid tumour patients (n=111). ERalpha was colocalised with both SRC-1 and NCoR to the nuclei of the tumour epithelial cells. Expression of ERalpha and NCoR was found predominantly in non-anaplastic tumours and was significantly associated with well-differentiated tumours and reduced incidence of disease recurrence. In non-anaplastic tumours, HER2 was significantly associated with SRC-1, and these proteins were associated with poorly differentiated tumours, capsular invasion and disease recurrence. Totally, 87% of anaplastic tumours were positive for SRC-1. Kaplan-Meier estimates of disease-free survival indicated that in thyroid cancer, SRC-1 strongly correlates with reduced disease-free survival (P<0.001), whereas NCoR predicted increased survival (P<0.001). These data suggest opposing roles for the coregulators SRC-1 and NCoR in thyroid tumour progression.

Expression Levels of Co-Regulators in Early Breast Cancer.

Abstract Introduction: The p160 (SRC) family of estrogen receptor (ER) co-activators have important implications in tamoxifen resistance. The SRC family play a central role in ER mediated transcription. There are three family members; SRC-1, SRC-2 and AIB1. AIB1 is amplified in 5-10% of human breast cancers. SRC-1 expression is associated with HER2 expression, increased risk of recurrence and insensitivity to endocrine treatment. Co-factors interact with the ER and basal transcriptional machine to activate or repress ER-mediated transcription. To investigate the role of ER and its co-factors in breast cancer we have carried out quantitative RT-PCR (qRT-PCR) to measure the relative expression of ERa and its co-factors.Methods: In this study we examined patients which were untreated or treated with chemotherapy or hormonal therapy following breast conservation surgery. RNA was extracted from 340 early breast cancer specimens from the Edinburgh Breast Conserving Surgery cohort (BCS). The BCS is a fully documented consectutive cohort of breast cancers treated by conservation surgery, axillary node sampling or clearance, and whole breast radiotherapy between 1981-1998. Clinico-pathological features and complete follow up (duration &amp;gt;10 years) is available for this cohort. qRT-PCR was carried out using primers for ER, SRC-1, SRC-2, AIB1, NCoR1 and SMRT.Results: This study demonstrated SRC-1 expression to be negatively correlated with both SRC-2 and AIB1 expression. SRC-1 expression was also negatively correlated with the co-repressors NCoR1 and SMRT expression. There was a strong correlation between the co-repressors, NCoR1 and SMRT and the co-activators SRC-2 and AIB1. Relapse-free survival (RFS) was estimated using Kaplan-Meier curves. Patients who had high expression of all three co-activators had reduced relapse-free survival (HR: 2.15 95%C.I. 1.175-3.921, p=0.01). No significant association was noted with overall survival. Exploratory subgroup analysis was under powered and showed no significant association with outcome.Conclusion: In conclusion, our study of expression levels of ER and its cofactors by quantitative RT-PCR in breast cancer samples revealed a correlation between the co-factors and co-repressors. These findings would suggest that ER and cofactors may play a synergistic role in the development and progression of breast cancer. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2127.

Serum S100B as a Prognostic Indicator in Patients with Breast Cancer.

Abstract BackgroundThe nuclear receptor co-activator SRC-1 has recently been implicated as an important mediator of breast cancer metastasis in vitro. These findings are in keeping with previous reports from our group reporting significantly reduced disease free survival in patients who express SRC-1 when compared to those who do not. We identified the developmental protein HOXc11 as interacting with SRC-1 in tamoxifen resistant breast cancer cells. Dysregulation of homeobox genes has been reported in a wide variety of both solid organ and haematological malignancies. The putative target gene of HOXc11, S100B is a secreted protein, known to be of prognostic significance in malignant melanoma. The aim of this work was to examine the relationship between HOXc11, SRC-1 and S100B and their relevance to disease progression in breast cancer.Materials and MethodsAll chromatin immunoprecipitation (ChIP) and proliferation assays were performed in tamoxifen resistant breast cancer cells derived from MCF7s. Immunohistochemistry was performed for S100B, HOXc11 and SRC-1 on a tissue microarray of 560 patients with invasive breast cancer with a median follow up of 6.5 years. S100B was assessed using an ELISA based technique (Diasorin, USA) on serum samples of a prospective cohort of patients with breast cancer prior to any treatment.ResultsChIP assays confirmed recruitment of both HOXc11 and SRC-1 to the promoter region of S100B after treatment with tamoxifen at both 45 minutes and 2 hours when compared to control. Treatment of tamoxifen resistant cells with HOXc11 siRNA resensitised the cells to the anti-proliferative effects of tamoxifen. Immunohistochemistry revealed S100B to be a strong predictor of reduced disease free survival in patients receiving adjuvant endocrine treatment (Hazard ratio 5.82; p&amp;lt;0.0001). Tumour expression of S100B was associated with expression of both HOXc11 and SRC-1 providing translational evidence for a relationship between these proteins. Elevated serum levels (&amp;gt;0.15ug/l) of S100B were found in 10.5% of patients with breast cancer prior to treatment. Elevated S100B correlated with HER2 positivity (Fisher's exact: p=0.005) but not with any of the other standard clinico-pathological factors examined. From a cohort of 80 patients with known medium to long term follow up, elevated serum S100B showed a strong positive correlation with disease recurrence (p=0.017, odds ratio 9.38).DiscussionOur investigations into the prognostic significance of S100B in breast cancer have shown considerable promise. Given it's accessibility as a serum protein, quantifiable by ELISA, it offers potential as a marker for disease recurrence in patients with breast cancer. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4052.

SRC-1 Promotes Breast Cancer Metastasis by Activating MAPK Pathway.

Abstract Background: Steroid receptor coactivator (SRC-1) was defined as a nuclear receptor coactivator. It interacts with nuclear receptor and other transcriptional factors and promotes target genes expression. In breast cancer, SRC-1 expression correlates positively with HER2 expression, disease recurrence and resistance to endocrine therapy. Our previous work demonstrated that knockout of SRC-1 in mice suppressed breast cancer metastasis without affecting primary tumor initiation and growth in the MMTV-PyMT transgenic mice. However, the molecular mechanism responsible for SRC-1 in breast cancer metastasis is still unclear.Material and Methods: To further study the function of SRC-1 in breast cancer metastasis, we generated transgenic mice with overexpression of human SRC-1 in the mouse mammary epithelial cells. The mammary glands of these mice exhibited normal development. After crossing these mice with MMTV-TVA (avian subgroup A receptor gene, TVA) transgenic mice, we obtained MMTV-TVA/MMTV-hSRC-1 (tester) and MMTV-TVA/WT (control) biogenic mice. RCAS (avian leukosis virus) viruses, which contain MMTV-PyMT expression cassette and can bind to TVA, were injected into mammary gland to induce mammary tumor. Tumor initiation, growth and metastasis were carefully examined with these mice. To investigate mechanism, multiple PyMT tumor cell lines were generated form individual primary tumor with or without SRC-1 and cell migration and invasion were compared with those cells and human breast cancer cells.Results and discuss: No difference in tumor initiation and growth was observed in those mice, but metastasis incidence of breast cancer to lung increased significantly in PyMT/TVA/hSRC-1 mice compared with PyMT/TVA/WT control mice. Tumor metastasis in lung also presented higher index in PyMT/TVA/hSRC-1 mice. In vitro study with PyMT/SRC-1 WT and KO cell lines showed SRC-1 deficiency disturbed cells migration and invasion. WT tumor cells adhered faster to extracellular matrix fibronecetin (FN) and presented high levels of phosphorylated forms of FAK, c-Src, Erk, Jnk and activated Rac1. Western blotting and real-time RT-PCR revealed lower integrin alpha5 and Gem, one of GTP binding protein, levels in SRC-1 deficient tumor cells. In human breast cancer MDA-MB-231 cells, SRC-1 knockdown led to decreased cell migration and invasion. Therefore, SRC-1 may regulate integrin expression and MAPK pathway to promote cancer cell migration and metastasis. Our study provides a possibility to inhibit breast cancer metastasis by targeting SRC-1 function. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6150.

Progesterone and estradiol effects on SRC-1 and SRC-3 expression in human astrocytoma cell lines

Progesterone (P(4)) and estradiol (E(2)) regulate many cell functions through their interaction with specific intracellular receptors, which require the participation of coactivators such as SRC-1 and SRC-3 for enhancing their transcriptional activity. Coactivator expression is altered in many cancers and in some of them their expression is regulated by P(4) and E(2). In this study, we determined progesterone and estrogen receptor isoform expression in two human astrocytoma cell lines with different evolution grade (U373, grade III; and D54, grade IV) by Western Blot. We studied the role of P(4) and E(2) on SRC-1 and SRC-3 expression in U373 and D54 cell lines by RT-PCR and Western blot. In U373 cells, P(4) did not modify SRC-1 expression, but in D54 cells it increased SRC-1 mRNA expression after 12 h of treatment without significant changes after 24 h. P(4) also increased SRC-1 protein content after 24 h, but reduced it after 48 h. E(2) did not change SRC-1 expression in any cell line. SRC-3 expression was not regulated by either E(2) or P(4). Our data suggest that SRC-1 and SRC-3 expression is differentially regulated by sex steroid hormones in astrocytomas and that P(4) regulates SRC-1 expression depending on the evolution grade of human astrocytoma cells.

Importance of steroid receptor coactivators in the modulation of steroid action on brain and behavior

Steroid receptors such as estrogen and androgen receptors are nuclear receptors involved in the transcriptional regulation of a large number of target genes. Steroid-dependent protein expression in the brain controls a large array of biological processes including spatial cognition, copulatory behavior and neuroprotection. The discovery of a competition, or squelching, between two different nuclear receptors introduced the notion that common cofactors may be involved in the modulation of transcriptional activity of nuclear receptors. These cofactors or coregulatory proteins are functionally divided into coactivators and corepressors and are involved in chromatin remodeling and stabilization of the general transcription machinery. Although a large amount of information has been collected about the in vitro function of these coregulatory proteins, relatively little is known regarding their physiological role in vivo, particularly in the brain. Our laboratory and others have demonstrated the importance of SRC-1 in the differentiation and activation of steroid-dependent sexual behaviors and the related neural genes. For example, we report that the inhibition of SRC-1 expression blocks the activating effects of exogenous testosterone on male sexual behaviors and increases the volume of the median preoptic area. Other coactivators are likely to be involved in the modulation in vivo of steroid receptor activity and it seems that the presence of a precise subset of coactivators could help define the phenotype of the cell by modulating a specific downstream pathway after steroid receptor activation. The very large number of coactivators and their association into preformed complexes potentially allows the determination of hundreds of different phenotypes. The study of the expression of the coactivator and their function in vivo is required to fully understand steroid action and specificity in the brain.

Expression of estrogen receptor co-regulators SRC-1, RIP140 and NCoR and their interaction with estrogen receptor in rat uterus, under the influence of ormeloxifene

Ormeloxifene binds competitively to ERs and antagonizes estrogen-induced gene expression in the uterus. However its detailed molecular mechanisms are not well understood. Present study was aimed to examine the changes in expression pattern of co-regulatory proteins SRC-1 (co-activator), RIP140 and NCoR (co-repressors) and their interaction with ERα in rat uterus under the influence of ormeloxifene (Orm) and tamoxifen (Tam). Adult ovariectomized rats were treated with estradiol (E 2) (5 μg/100 g), or Orm or Tam (200 μg/100 g, s.c.) alone or along with E 2, for 3 days. RT-PCR analysis of uterine RNA and immunoblotting of uterine extracts revealed that expression of SRC-1, RIP140 and NCoR was insensitive to E 2 or Orm or Tam treatment. Direct protein–protein interaction experiments using co-immunoprecipitation revealed that E 2-induced the interaction of ERα with co-activator SRC-1. In rats given Orm alone or along with E 2, there was a significant reduction in E 2-induced effect on ERα–SRC-1 interaction. In case of ERβ and SRC-1, Orm reduced interaction only in the absence of E 2. Interaction of RIP140 or NCoR with ERα was found to be more in rats treated with Orm along with E 2 as compared to that in E 2-treated rats whereas no such recruitment was found in Tam treated rats. Interaction of RIP140 with ERβ was insensitive to Orm or Tam treatment whereas the interaction of NCoR with ERα and ERβ was increased in Orm treated rats. Ormeloxifene also showed inhibitory effects on uterine ER–ERE binding and estrogen-induced expression of progesterone receptor. Taken together, these findings demonstrate that ormeloxifene antagonizes ERα-mediated transcription by inhibiting the recruitment of SRC-1 and inducing the recruitment of RIP140 and NCoR.

The developmental protein HOXc11 as a mediator of endocrine resistance in breast cancer.

Abstract Abstract #3034 The nuclear receptor coactivator, SRC-1, has been implicated as an important mediator of resistance to endocrine therapy in breast cancer through work from our group and others. Using mass spectrometry we identified the homeobox protein HOXc11 as an interacting partner for the nuclear receptor coactivator SRC-1 in endocrine resistant breast cancer cells. Homeobox genes control cell differentiation. The processes of neoplasia and normal development are closely linked, therefore it is little surprise that increasing evidence implicates these genes in neoplasia development.&amp;#x2028; We propose that the interaction between SRC-1 and HOXc11 plays an important role in the development of endocrine resistance. Our aim was to identify potential HOXc11/SRC-1 target genes and assess the clinical significance of these genes.&amp;#x2028; Co-immunprecipitation assays confirmed the SRC-1 and HOXc11 interaction after treatment with tamoxifen for 2 hours in the endocrine resistant LY2 breast cancer cell line, an interaction that was not present in endocrine sensitive MCF-7 cells under the same treatment conditions. A target gene for HOXc11, S100β, has previously been identified in neuronal cells. Based on this we sought the presence of either protein at the promoter region for S100β. Chromatin immunoprecipitation (ChIP) assays in LY2 cells confirmed recruitment of both HOXc11 and SRC-1 to the promoter region of S100β after treatment with tamoxifen at both 45 minutes and 2 hours when compared to control.&amp;#x2028; To assess the clinical significance of S100β, we used immunohistochemistry on a paraffin embedded tissue microarray to examine itÂs expression in a large cohort of breast cancer patients (n=560). S100β was a strong predictor of reduced disease free survival in patients receiving adjuvant endocrine treatment (Hazard ratio 5.82; p&amp;lt;0.0001). This also showed that expression of S100β was associated with expression of HOXc11 and SRC-1. Given that S100β is a secreted protein, we hypothesized that elevated levels could be detected in patients with breast cancer at time of diagnosis. Using an ELISA to measure S100β levels, we found elevated levels in one quarter of breast cancer patients, pre treatment, when compared to age matched controls.&amp;#x2028; Investigation into non steroidal SRC-1 binding partners in endocrine resistant breast cancer identified the homeobox protein HOXc11. A target gene for the interaction between SRC-1 and HOXc11, S100β, is a secreted protein and raises the exciting possibility that it may offer potential as a biomarker for endocrine resistance in breast cancer. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3034.

The Role of SRC-1 in Murine Prostate Carcinogenesis Is Nonessential due to a Possible Compensation of SRC-3/AIB1 Overexpression

The androgen and androgen receptor (AR)-regulated gene expression plays important roles in normal prostate and prostate cancer development, and AR transcriptional control of genes is mediated by transcriptional coactivators, including the three members of the steroid receptor coactivator (SRC) family, SRC-1 (NCOA1), SRC-2 (TIF2/GRIP1/NCOA2) and SRC-3 (AIB1, ACTR/RAC3/NCOA3). SRC-1 and SRC-3 are overexpressed in multiple human endocrine cancers and knockdown of either one of them in prostate cancer cell lines impedes cellular proliferation. Knockout of SRC-3 in mice suppresses the progression of spontaneous prostate carcinogenesis. In this study, we investigated SRC-1 contribution to prostate cancer in vivo by deleting the SRC-1 gene in TRAMP mice, which contain the probasin promoter-driven SV40 T/t antigen transgene. In assessing tumor mass of mice at various ages, we found that initiation and progression of prostate cancer induced by SV40 T/t antigens were unaltered in SRC-1(-/-) mice versus WT mice. Primary tumor histology and metastasis to distant lymph nodes were also similar in these mice at all time points assessed. These results demonstrate that the role of SRC-1 in mouse prostate carcinogenesis is nonessential and different from the essential contribution of SRC-3 that is required for prostate cancer progression and metastasis in mice. Interestingly, we observed that during prostate tumorigenesis SRC-1 expression was relatively constant, while SRC-3 expression was significantly elevated. Therefore, the loss of SRC-1 function may be compensated by SRC-3 overexpression during prostate tumorigenesis in SRC-1(-/-) mice.

Unique Roles of p160 Coactivators for Regulation of Breast Cancer Cell Proliferation and Estrogen Receptor-α Transcriptional Activity

Each of the three members of the p160 steroid receptor coactivator (SRC) family of coactivators (SRC-1, SRC-2 and SRC-3) stimulates estrogen receptor (ER)-alpha function in trans-activation assays. Consequently, we sought to elucidate their contributions to the ER-regulated processes of cell proliferation, apoptosis, and the expression of ERalpha target genes in MCF-7 breast cancer cells. The small interfering RNA depletion of SRC-2 or SRC-3 but not SRC-1 inhibited growth of MCF-7 cells, and this was reflected in decreased cell cycle progression and increased apoptosis in SRC-2- or SRC-3-depleted cells as well as a reduction in ERalpha transcriptional activity measured on a synthetic reporter gene. However, only SRC-3 depletion blocked estradiol stimulated cell proliferation. Depletion of SRC-1 did not affect these events, and together this reveals functional differences between each of the three SRC family coactivators. Regulation of the endogenous ERalpha target gene, c-myc was not affected by depletion of any of the p160 coactivators although depletion of each of them decreased pS2 mRNA expression in estradiol-treated MCF-7 cells. Moreover, progesterone receptor and cyclin D1 gene expression were decreased in SRC-3 small interfering RNA-treated cells. Expression of mRNA and protein levels for the antiapoptotic gene, Bcl-2 was dependent on SRC-3 expression, whereas Bcl-2 protein but not mRNA expression also was sensitive to SRC-1 depletion. Together these data indicate that the closely related p160 coactivators are not functionally redundant in breast cancer cells because they play gene-specific roles in regulating mRNA and protein expression, and they therefore are likely to make unique contributions to breast tumorigenesis.

The genetic ablation of SRC-3 protects against obesity and improves insulin sensitivity by reducing the acetylation of PGC-1α

Transcriptional control of metabolic circuits requires coordination between specific transcription factors and coregulators and is often deregulated in metabolic diseases. We characterized here the mechanisms through which the coactivator SRC-3 controls energy homeostasis. SRC-3 knock-out mice present a more favorable metabolic profile relative to their wild-type littermates. This metabolic improvement in SRC-3(-/-) mice is caused by an increase in mitochondrial function and in energy expenditure as a consequence of activation of PGC-1alpha. By controlling the expression of the only characterized PGC-1alpha acetyltransferase GCN5, SRC-3 induces PGC-1alpha acetylation and consequently inhibits its activity. Interestingly, SRC-3 expression is induced by caloric excess, resulting in the inhibition of PGC-1alpha activity and energy expenditure, whereas caloric restriction reduces SRC-3 levels leading to enhanced PGC-1alpha activity and energy expenditure. Collectively, these data suggest that SRC-3 is a critical link in a cofactor network that uses PGC-1alpha as an effector to control mitochondrial function and energy homeostasis.

Ets-2 and p160 proteins collaborate to regulate c-Myc in endocrine resistant breast cancer

Associations between p160 coactivator proteins and endocrine resistance have been described. Though thought to primarily interact with steroid receptors, the p160 proteins can also interact with non-nuclear receptor transcription factors including the MAP kinase effector proteins Ets. Here, we observed that in breast cancer cells resistant and insensitive to endocrine treatment, the growth factor EGF induced Ets-2 but not Ets-1 transcriptional regulation of the oncogene myc. Ets-2 regulation of myc was found to be reliant on the p160 proteins SRC-1 and SRC-3. In support of these molecular observations, strong associations were observed between the transcription factor, Ets-2 and its coactivator SRC-1 (P<0.01) and the target gene myc (P<0.0001) in a cohort of breast cancer patients with locally advanced disease. Expression of Ets-2, SRC-1 and c-Myc individually all associated with reduced disease-free survival (P<0.001, P<0.001 and P=0.002 respectively). There was no association between SRC-3 and disease-free survival (P=0.707). SRC-1 can utilize MAP kinase effector transcription factor Ets-2 to regulate the production of the oncogene myc. These signalling mechanisms may be important in the development of steroid resistant/independent breast cancer.

ATF2 impairs glucocorticoid receptor–mediated transactivation in human CD8+ T cells

AbstractChronic inflammatory diseases often have residual CD8+ T-cell infiltration despite treatment with systemic corticosteroids, which suggests divergent steroid responses between CD4+ and CD8+ cells. To examine steroid sensitivity, dexamethasone (DEX)–induced histone H4 lysine 5 (K5) acetylation and glucocorticoid receptor α (GCRα) translocation were evaluated. DEX treatment for 6 hours significantly induced histone H4 K5 acetylation in normal CD4+ cells (P = .001) but not in CD8+ cells. DEX responses were functionally impaired in CD8+ compared with CD4+ cells when using mitogen-activated protein kinase phosphatase (1 hour; P = .02) and interleukin 10 mRNA (24 hours; P = .004) induction as a readout of steroid-induced transactivation. Normal DEX-induced GCRα nuclear translocation and no significant difference in GCRα and GCRβ mRNA expression were observed in both T-cell types. In addition, no significant difference in SRC-1, p300, or TIP60 expression was found. However, activating transcription factor-2 (ATF2) expression was significantly lower in CD8+ compared with CD4+ cells (P = .009). Importantly, inhibition of ATF2 expression by small interfering RNA in CD4+ cells resulted in inhibition of DEX-induced transactivation in CD4+ cells. The data indicate refractory steroid-induced transactivation but similar steroid-induced transrepression of CD8+ cells compared with CD4+ cells caused by decreased levels of the histone acetyltransferase ATF2.

Clinical implications of steroid receptor coactivator (SRC)-3 in uterine endometrial cancers

Estrogen is recognized as a significant modifier in the development, growth and invasion of uterine endometrial cancer. Steroid receptor coactivator-3 (SRC-3; AIB1, ACTR, RAC3, TRAM-1, and pCIP) is a member of the p160 family of coactivator for nuclear hormone receptors including estrogen receptor (ER). It is reported that SRC-3 is overexpressed in various cancers. However, SRC-3 expression manner in uterine endometrial cancer is not fully understood. In this study, we showed SRC-3 mRNA expression correlates with clinical stage, depth of myometrial invasion and dedifferentiation. The prognosis of the 25 patients with higher expression of SRC-3 mRNA in uterine endometrial cancers was extremely poor (36%), whereas the 24-month survival rate of the 15 patients with lower expression of SRC-3 mRNA was 96%. These data indicate that SRC-3 might be an important indicator of uterine endometrial cancer advancement and survival.

Perinatal bisphenol A affects the behavior and SRC-1 expression of male pups but does not influence on the thyroid hormone receptors and its responsive gene

Bisphenol A (BPA) has been shown to interfere with thyroid hormone receptors (THRs) and to influence the expression of THR-responsive elements in vivo and in vitro, while some studies reported hyperactivity induced by BPA treatment. In the present study, our purpose was to investigate the effect of BPA exposure on behavioral alteration and its mechanism of action, especially focusing on the thyroid hormone pathway. Significant sexual difference on behaviors was observed in perinatal BPA exposure, as manifested by hyperactivity and impaired spatial learning/memory in male pups after matured. Dams treated with 0.1 mg/l BPA showed transient hypothyroidism, while male pups were found to exhibit a transient hyperthyroidism followed by hypothyroidism. Furthermore, significant up-regulated expression levels of mRNA and protein of SRC-1 in the hippocampus were observed in male pups by 0.1 mg/l BPA treatment. However the expression of THRα/β and RC3/neurogranin were not affected by BPA treatment. These results indicate that perinatal BPA exposure at a very low level may influence thyroid function and then consequently affects brain development, but at the same time, suggest that thyroid hormone receptor may not be a direct target of BPA action, but instead, another factor may be involved in this action.

The core component of the mammalian SWI/SNF complex SMARCD3/BAF60c is a coactivator for the nuclear retinoic acid receptor

Retinoic acid receptors (RARs) activate transcription by recruiting coactivator complexes such as histone acetyltransferases (HAT) and the mediator complex, to increase chromatin accessibility by general transcription factors and to promote transcription initiation. Indirect evidences have suggested a role for the ATP-dependent chromatin remodeling complex SWI/SNF in RAR-mediated transcription. Here we demonstrate that two highly related subunits of the core SWI/SNF complex, BAF60c1 and BAF60c2, interact physically with retinoid receptors and are coactivators for RARs. This coactivating property is dependent on SRC1 expression, showing that HATs and SWI/SNF cooperate in this retinoid-controlled transcriptional process.

Tamoxifen-induced ER-α–SRC-3 interaction in HER2 positive human breast cancer; a possible mechanism for ER isoform specific recurrence

Differential signalling between the two oestrogen receptor (ER) isoforms in the presence of tamoxifen has been described. We hypothesise that differential recruitment of the steroid receptor co-activator, SRC-3 to ER-alpha and ER-beta may in part explain associations between ER isoforms and response to endocrine treatment. SRC-3 was localised within epithelial cells of breast tumour tissue and was co-localised with ER-alpha and ER-beta, (n=112). Expression of SRC-3 was found to be positively associated with ER-alpha (P=0.0021) and inversely with ER-beta (P<0.0001). Uniquely, this study utilises primary cell cultures derived from patient tumours, thus providing samples not readily available in most molecular model systems. These samples have enabled us to investigate the influence of growth factor pathways on steroid receptor-co-activator interactions. In HER2 (human epidermal growth factor receptor 2) positive primary tumour cell cultures 17beta-estradiol induced a decrease in SRC-3, whereas upregulated SRC-3 expression. Furthermore, treatment with tamoxifen-induced SRC-3 recruitment to the ER-oestrogen response element and enhanced interaction between SRC-3 and ER-alpha, but not ER-beta. Knockdown of SRC-3 results in a concomitant loss of expression of the oestrogen target gene pS2. Furthermore, silencing of SRC-3 resensitizes endocrine resistant, HER2 positive cells to the anti-proliferative effects of tamoxifen. The ability of ER-alpha, but not ER-beta to recruit SRC-3 in the presence of tamoxifen may in part explain the differential ER isoform associations with recurrence in human breast cancer.

Sound conditioning protects hearing by activating the hypothalamic–pituitary–adrenal axis

Sound conditioning primes the auditory system to low levels of acoustic stimuli and reduces damage caused by a subsequent acoustic trauma. This priming activates the HPA axis resulting in the elevation of plasma corticosterone with a consequent upregulation of glucocorticoid receptors (GR) in the cochlea and the paraventricular nucleus (PVN) of the hypothalamus in the mouse. This protective effect is blocked by adrenalectomy or pharmacological treatment with RU486 + metyrapone. Sound conditioning prevents GR down-regulation induced by acoustic trauma and subsequently enhances GR activity in spiral ganglion neurons. Increased SRC-1 expression, triggered by sound conditioning, positively correlates with the upregulation of GR in the cochlea. These findings will help to define the cellular mechanisms responsible for protecting the auditory system from hearing loss by sound conditioning.

Targeting steroid receptor coactivator-1 expression with locked nucleic acids antisense reveals different thresholds for the hormonal regulation of male sexual behavior in relation to aromatase activity and protein expression

Steroid receptors such as the androgen and estrogen receptors require the presence of several proteins, known as coactivators, to enhance the transcription of target genes. The first goal of the present study was to define the role of SRC-1 on the steroid-dependent expression of the aromatase protein and its activity in male Japanese quail. The second goal was to analyze the rapid plasticity of the POM following antisense treatment interruption. We confirm here that the inhibition of SRC-1 expression by daily intracerebroventricular injections of locked nucleic acid antisense oligonucleotides in the third ventricle at the level of the preoptic area-hypothalamus (HPOA) significantly reduces testosterone-dependent male sexual behavior. In the first experiment, aromatase protein expression in HPOA was inhibited in SRC-1-depleted males but the enzymatic activity remained at the level measured in controls. We observed in the second experiment a recovery of the behavioral response to testosterone treatment after interruption of the antisense injection. However, several morphological characteristics of the POM were not different between the control group, the antisense-treated birds and antisense-treated birds in which treatment had been discontinued 3 days earlier. Antisense was also less effective in knocking-down SRC-1 in the present experiments as compared to our previous study. An analysis of this variation in the degree of knock-down of SRC-1 expression suggests dissociation among different aspects of steroid action on brain and behavior presumably resulting from the differential sensitivity of behavioral and neurochemical responses to the activation by testosterone and/or its estrogenic metabolites.