Molecular structure and biological function of the cancer-amplified nuclear receptor coactivator SRC-3/AIB1

Critical Roles of SRC-3 in the Development and Progression of Breast Cancer, Rendering It a Prospective Clinical Target

Breast cancer (BCa) is the most frequently diagnosed malignant tumor in women and is also one of the leading causes of cancer-related death. Most breast tumors are hormone-dependent and estrogen signaling plays a critical role in promoting the survival and malignant behaviors of these cells. Estrogen signaling involves ligand-activated cytoplasmic estrogen receptors that translocate to the nucleus with various co-regulators, such as steroid receptor co-activator (SRC) family members, and bind to the promoters of target genes and regulate their expression. SRC-3 is a member of this family that interacts with, and enhances, the transcriptional activity of the ligand activated estrogen receptor. Although SRC-3 has important roles in normal homeostasis and developmental processes, it has been shown to be amplified and overexpressed in breast cancer and to promote malignancy. The malignancy-promoting potential of SRC-3 is diverse and involves both promoting malignant behavior of tumor cells and creating a tumor microenvironment that has an immunosuppressive phenotype. SRC-3 also inhibits the recruitment of tumor-infiltrating lymphocytes with effector function and promotes stemness. Furthermore, SRC-3 is also involved in the development of resistance to hormone therapy and immunotherapy during breast cancer treatment. The versatility of SRC-3 in promoting breast cancer malignancy in this way makes it a good target, and methodical targeting of SRC-3 probably will be important for the success of breast cancer treatment.

AIB1 is a novel target of the high-risk HPV E6 protein and a biomarker of cervical cancer progression

The high-risk human papillomaviruses (HPV-16, -18) are critical etiologic agents in human malignancy, most importantly in cervical cancer. These oncogenic viruses encode the E6 and E7 proteins that are uniformly retained and expressed in cervical cancers and required for maintenance of the tumorigenic phenotype. The E6 and E7 proteins were first identified as targeting the p53 and pRB tumor suppressor pathways, respectively, in host cells, thereby leading to disruption of cell cycle controls. In addition to p53 degradation, a number of other functions and critical targets for E6 have been described, including telomerase, Myc, PDZ-containing proteins, Akt, Wnt, mTORC1, as well as others. In this study, we identified Amplified in Breast Cancer 1 (AIB1) as a new E6 target. We first found that E6 and hTERT altered similar profiling of gene expression in human foreskin keratinocytes (HFK), independent of telomerase activity. Importantly, AIB1 was a common transcriptional target of both E6 and hTERT. We then verified that high-risk E6 but not low-risk E6 expression led to increases in AIB1 transcript levels by real-time RT-PCR, suggesting that AIB1 upregulation may play an important role in cancer development. Western blots demonstrated that AIB1 expression increased in HPV-16 E6 and E7 expressing (E6E7) immortalized foreskin and cervical keratinocytes, and in three of four common cervical cancer cell lines as well. Then, we evaluated the expression of AIB1 in human cervical lesions and invasive carcinoma using immunohistochemical staining. Strikingly, AIB1 showed positivity in the nucleus of cells in the immediate suprabasal epithelium, while nuclei of the basal epithelium were negative, as evident in the Cervical Intraepithelial Neoplasia 1 (CIN1) samples. As the pathological grading of cervical lesions increased from CIN1, CIN2, CIN3 carcinoma in situ and invasive carcinoma, AIB1 staining increased progressively, suggesting that AIB1 may serve as a novel histological biomarker for cervical cancer development. For cases of invasive cervical carcinoma, AIB1 staining was specific to cancerous lesions. Increased expression of AIB1 was also observed in transgenic mouse cervical neoplasia and cancer models induced by E6E7 and estrogen. Knockdown of AIB1 expression in E6E7 immortalized human cervical cells significantly abolished cell proliferation. Taken together, these data support AIB1 as a novel target of HPV E6 and a biomarker of cervical cancer progression.

Stereospecific lasofoxifene derivatives reveal the interplay between estrogen receptor alpha stability and antagonistic activity in ESR1 mutant breast cancer cells

Chemical manipulation of estrogen receptor alpha ligand binding domain structural mobility tunes receptor lifetime and influences breast cancer therapeutic activities. Selective estrogen receptor modulators (SERMs) extend estrogen receptor alpha (ERα) cellular lifetime/accumulation. They are antagonists in the breast but agonists in the uterine epithelium and/or in bone. Selective estrogen receptor degraders/downregulators (SERDs) reduce ERα cellular lifetime/accumulation and are pure antagonists. Activating somatic ESR1 mutations Y537S and D538G enable resistance to first-line endocrine therapies. SERDs have shown significant activities in ESR1 mutant setting while few SERMs have been studied. To understand whether chemical manipulation of ERα cellular lifetime and accumulation influences antagonistic activity, we studied a series of methylpyrollidine lasofoxifene (Laso) derivatives that maintained the drug’s antagonistic activities while uniquely tuning ERα cellular accumulation. These molecules were examined alongside a panel of antiestrogens in live cell assays of ERα cellular accumulation, lifetime, SUMOylation, and transcriptional antagonism. High-resolution x-ray crystal structures of WT and Y537S ERα ligand binding domain in complex with the methylated Laso derivatives or representative SERMs and SERDs show that molecules that favor a highly buried helix 12 antagonist conformation achieve the greatest transcriptional suppression activities in breast cancer cells harboring WT/Y537S ESR1. Together these results show that chemical reduction of ERα cellular lifetime is not necessarily the most crucial parameter for transcriptional antagonism in ESR1 mutated breast cancer cells. Importantly, our studies show how small chemical differences within a scaffold series can provide compounds with similar antagonistic activities, but with greatly different effects of the cellular lifetime of the ERα, which is crucial for achieving desired SERM or SERD profiles.

Effect of Src tyrosine kinase on a rat model of asthma

Src tyrosine kinase is a protein encoded by the Src gene. The present study aimed to determine the role of Src protein kinase in asthma using small interfering RNA (siRNA) technology. Several Src siRNAs were designed and the most effective siRNA pair was selected. A rat model of asthma was established using ovalbumin, and the rats were treated with Src siRNA, empty vector or phosphate-buffered saline (PBS). A non-asthmatic control group was also established. The rats were clinically observed and Src mRNA and protein levels were measured by reverse transcription-quantitative PCR and western blot analysis, respectively. Pathological observation of the lung tissue, counting of white blood cells (WBCs) and eosinophils (EOSs) and analysis of the concentrations of IL-5, IL-33 and IFN-γ in the bronchoalveolar lavage fluid were performed. The expression levels of Src mRNA in the control, PBS, empty vector and siRNA groups were 110±30.7x10³, 253±55.4x10³, 254±41.3x10³ and 180±50.9x10³, respectively. Histochemical analysis of the lung tissue of rats in the siRNA group exhibited a relatively complete lung structure and little damage to the alveolar cavity. Src protein expression and IL-5, IL-33 levels, WBC and EOS levels were positively correlated with Src mRNA expression, while the IFN-γ concentration was negatively correlated with Src mRNA expression. These results indicate that Src knockdown inhibits the release of tracheal inflammatory factors and significantly alleviates asthma in rats. In conclusion, the present study utilized a gene transfer technique to interfere with the expression of Src in rats, which decreased the levels of IL-5, IL-33, WBCs and EOSs and increased the level of IFN-γ; these changes effectively ameliorated the condition of the trachea in asthmatic rats.

SRC-3, a Steroid Receptor Coactivator: Implication in Cancer

Steroid receptor coactivator-3 (SRC-3), also known as amplified in breast cancer 1 (AIB1), is a member of the SRC family. SRC-3 regulates not only the transcriptional activity of nuclear receptors but also many other transcription factors. Besides the essential role of SRC-3 in physiological functions, it also acts as an oncogene to promote multiple aspects of cancer. This review updates the important progress of SRC-3 in carcinogenesis and summarizes its mode of action, which provides clues for cancer therapy.

A comprehensive review on anticancer mechanism of bazedoxifene

Cancer is counted as a second leading cause of death among nontransmissible diseases. Identification of novel anticancer drugs is therefore necessary for the effective treatment of cancer. Conventional drug discovery is time consuming and expensive process. Unlike conventional drug discovery, drug repositioning offers a novel strategy for urgent drug discovery since it is a cost-effective and faster process. Bazedoxifene (BZA) is a synthetic selective estrogen receptor modulator, approved by the United States Food and Drug Administration for the treatment of osteoporosis in postmenopausal women. BZA is now being studied for its anticancer activity in various cancers including breast cancer, liver cancer, pancreatic cancer, colon cancer, head and neck cancer, medulloblastoma, brain cancer, and gastrointestinal cancer. Studies have reported that BZA is effective in reducing cancer progression through multiple mechanisms. BZA could effectively inhibit STAT3, PI3K/AKT, and MAPK signaling pathways and induce apoptosis. In addition to its anticancer activity as monotherapy, BZA has been shown to enhance the chemotherapeutic efficacy of clinical drugs such as paclitaxel, cisplatin, palbociclib, and oxaliplatin in multiple neoplasms. This review mainly focused on the anticancer activity, cellular targets, and anticancer mechanism of BZA, which may help the further design and conduct of research and repositioning it for oncological clinic trials.

Targeting the NCOA3-SP1-TERT axis for tumor growth in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) has a high mortality rate and lacks an effective therapeutic target. Elevated expression of human telomerase reverse transcriptase (TERT) is an important hallmark in cancers, but the mechanism by which TERT is activated differentially in cancers is poorly understood. Here, we have identified nuclear receptor coactivator-3 (NCOA3) as a new modulator of TERT expression and tumor growth in HCC. NACO3 specifically binds to the TERT promoter at the -234 to -144 region and transcriptionally activates TERT expression. NCOA3 promotes HCC cell growth and tumor progression in vitro and in vivo through upregulating the TERT signaling. Knockdown of NACO3 suppresses HCC cell viability and colony formation, whereas TERT overexpression rescues this suppression. NCOA3 interacts with and recruits SP1 binding on the TERT promoter. Knockdown of NCOA3 also inhibits the expression of the Wnt signaling-related genes but has no effect on the Notch signaling-targeting genes. Moreover, NCOA3 is positively correlated with TERT expression in HCC tumor tissues, and high expression of both NCOA3 and TERT predicts a poor prognosis in HCC patients. Our findings indicate that targeting the NCOA3-SP1-TERT signaling axis may benefit HCC patients.

Nuclear Receptors Are Differentially Expressed and Activated in KAIMRC1 Compared to MCF7 and MDA-MB231 Breast Cancer Cells

We recently established a KAIMRC1 cell line that has unique features compared to the known breast cancer cell lines, MCF7 and MDA-MB231. To characterize it further, we investigated the expression profile of nuclear receptors and their respective co-factors in these cell lines. We confirm that in contrast to the triple negative cell line MDA-MB231, the MCF7 and KAIMRC1 are estrogen receptor alpha (ERa) and progesterone receptor alpha (PRa) positive, with significant lower expression of these receptors in KAIMRC1. KAIMRC1 cell is a vitamin D receptor (VDR) negative and V-ErbA-Related Protein 2 (EAR2) positive in contrast to MCF7 and MDA-MB231. Remarkably, the histone deacetylases (HDACs) are highly expressed in KAIRMC1 with HDAC6 and HDAC 7 are exclusively expressed in KAIMRC1 while thyroid hormone receptor-associated protein 80 (TRAP80), telomeric DNA binding protein 1 (TBP1) and TGF-beta receptor interacting protein (TRIP1) are absent in KAIMRC1 but present in MCF7 and MDA-MB231. In a luciferase reporter assay, the ERa coexpression is needed for estrogen receptor element (ERE)-luciferase activation by estradiol in KAIMRC1 but not in MCF7. The co-expression of exogenous Liver X receptor alpha (LXRa)/retinoid X receptor alpha (RXRa) are necessary for LXR responsive element (LXRE) activation by the GW3696 in the three cell lines. However, the activity of peroxisome proliferator-activated receptor response element (PPARE)-tk-luciferase reporter increased when peroxisome proliferator-activated receptors alpha (PPARa)/RXRa were coexpressed but the addition of PPARa agonist (GW7647) did not stimulate further the reporter. The signal of the PPARE reporter increased in a dose-dependent manner with rosiglitazone (PPARg agonist) in KAIMRC1, MCF7, and MDA-MB231 when the proliferator-activated receptors gamma (PPARg)/RXRa receptors were cotransfected. Retinoic acid-induced activation of retinoic acid receptor response element (RARE)-tk-luciferase is dependent on exogenous expression of retinoic acid receptor alpha (RARa)/RXRa heterodimer in MDA-MB 231 but not in MCF7 and KAIMRC1 cell lines. In the three cell lines, Bexarotene-induced retinoid X receptor response element (RXRE)-luciferase reporter activation was induced only if the RXRa/LXRa heterodimer were co-expressed. The vitamin D receptor response element (VDRE)-luciferase reporter activity showed another distinct feature of KAIMRC1, where only co-expression of exogenous vitamin D receptor (VDR)/RXRa heterodimer was sufficient to reach the maximum rate of activation of VDRE reporter. In the proliferation assay, nuclear receptors ligands showed a distinct effect on KAIMRC1 compared to MCF7 and MDA-MB231. Growth inhibition effects of used ligands suggest that KAIMRC1 correlate more closely to MDA-MB231 than MCF7. Vitamin D3, rosiglitazone, novel RXR compound (RXRc) and PPARa compound (GW6471) have the most profound effects. In conclusion, we showed that nuclear receptors are differentially expressed, activated and also their ligand produced distinct effects in KAIMRC1 compared to MCF7 and MDA-MB231. This finding gives us confidence that KAIMRC1 has a unique biological phenotype.

A novel SRC-2-dependent regulation of epithelial-mesenchymal transition in breast cancer cells

Steroid receptor coactivator 2 (SRC-2) is a nuclear receptor coactivator, important for the regulation of estrogen receptor alpha (ERα)-mediated transcriptional activity in breast cancer cells. However, the transcriptional role of SRC-2 in breast cancer is still ambiguous. Here we aimed to unravel a more precise transcriptional role of SRC-2 and uncover unique target genes in MCF-7 breast cancer cells, as opposed to the known oncogene SRC-3. Gene expression analyses of cells depleted of either SRC-2 or SRC-3 showed that they transcriptionally regulate mostly separate gene sets. However, individual unique gene sets were implicated in some of the same major gene ontology biological processes, such as cellular structure and development. This finding was supported by three-dimensional cell cultures, demonstrating that depletion of SRC-2 and SRC-3 changed the morphology of the cells into epithelial-like hollow acinar structures, indicating that both SRC proteins are involved in maintaining the hybrid E/M phenotype. In clinical ER-positive, HER2-negative breast cancer samples the expression of SRC-2 was negatively correlated with the expression of MCF-7-related luminal, cell cycle and cellular morphogenesis genes. Finally, elucidating SRC-2 unique transcriptional effects, we identified Lyn kinase (an EMT biomarker) to be upregulated exclusively after SRC-2 depletion. In conclusion, we show that both SRC-2 and SRC-3 are essential for the EMT in breast cancer cells, controlling different transcriptional niches.

Prognostic value of AIB1 and EIF5A2 in intravesical recurrence after surgery for upper tract urothelial carcinoma

Objectives

The aim of this study was to investigate the prognostic effect of amplified in AIB1 and EIF5A2 expression on postoperative intravesical recurrence for upper urinary tract urothelial carcinoma (UTUC) and improve postoperative risk stratification and prediction of intravesical chemotherapy benefit.

Materials and methods

We evaluated immunohistochemical expression of AIB1 and EIF5A2 in 109 UTUC patients to determine the predictive significance in intravesical recurrence. A prognostic model was developed based on univariate and multivariate analyses.

Results

Intravesical recurrence occurred in 18 out of the 109 (16.5%) patients during the follow-up period. Significant associations of high expression of AIB1 and EIF5A2 with shortened bladder recurrence interval (median: 24 months vs 46 months, P=0.021; 28 months vs 39 months, P=0.002) were demonstrated. In different subsets of UTUC patients, high expression of AIB1 was a prognostic indicator in high grade (P=0.006) and pT2–4 (P=0.007), and high expression of EIF5A2 for high grade (P=0.014), pT2–4 (P=0.002) and pN0 (P=0.009). Moreover, in multivariate analysis, AIB1 and EIF5A2 expression (P=0.034 and 0.022, respectively) together with pN stage (P=0.009) provided significant independent predictors for intravesical recurrence after surgery for UTUC. Surgical approach with radical nephroureterectomy (RNU) was an informative factor toward good oncologic outcomes for intravesical recurrence (P=0.056). Based on a prognostic model with these factors, patients with UTUC were classified into the low-risk group and the high-risk group. In a subset analysis, the patients in the high-risk group were found to have a favorable response to intravesical chemotherapy (P=0.047). A nomogram based on the multivariate analysis was developed to predict intravesical recurrence accurately and guide postoperative intravesical instillations. The concordance index (c-index) of this model was 0.806.

Conclusion

High expression of AIB1 and EIF5A2 were independent predictors for intravesical recurrence after RNU and might be able to predict which patients benefit from postoperative intravesical chemotherapy.

The SERM/SERD bazedoxifene disrupts ESR1 helix 12 to overcome acquired hormone resistance in breast cancer cells

Acquired resistance to endocrine therapy remains a significant clinical burden for breast cancer patients. Somatic mutations in the ESR1 (estrogen receptor alpha (ERα)) gene ligand-binding domain (LBD) represent a recognized mechanism of acquired resistance. Antiestrogens with improved efficacy versus tamoxifen might overcome the resistant phenotype in ER +breast cancers. Bazedoxifene (BZA) is a potent antiestrogen that is clinically approved for use in hormone replacement therapies. We found that BZA possesses improved inhibitory potency against the Y537S and D538G ERα mutants compared to tamoxifen and has additional inhibitory activity in combination with the CDK4/6 inhibitor palbociclib. In addition, comprehensive biophysical and structural biology studies show BZA’s selective estrogen receptor degrading (SERD) properties that override the stabilizing effects of the Y537S and D538G ERα mutations.

Toward the precision breast cancer survival prediction utilizing combined whole genome-wide expression and somatic mutation analysis

BACKGROUND

Breast cancer is the most common type of invasive cancer in woman. It accounts for approximately 18% of all cancer deaths worldwide. It is well known that somatic mutation plays an essential role in cancer development. Hence, we propose that a prognostic prediction model that integrates somatic mutations with gene expression can improve survival prediction for cancer patients and also be able to reveal the genetic mutations associated with survival.

METHOD

Differential expression analysis was used to identify breast cancer related genes. Genetic algorithm (GA) and univariate Cox regression analysis were applied to filter out survival related genes. DAVID was used for enrichment analysis on somatic mutated gene set. The performance of survival predictors were assessed by Cox regression model and concordance index(C-index).

RESULTS

We investigated the genome-wide gene expression profile and somatic mutations of 1091 breast invasive carcinoma cases from The Cancer Genome Atlas (TCGA). We identified 118 genes with high hazard ratios as breast cancer survival risk gene candidates (log rank p <  0.0001 and c-index = 0.636). Multiple breast cancer survival related genes were found in this gene set, including FOXR2, FOXD1, MTNR1B and SDC1. Further genetic algorithm (GA) revealed an optimal gene set consisted of 88 genes with higher c-index (log rank p <  0.0001 and c-index = 0.656). We validated this gene set on an independent breast cancer data set and achieved a similar performance (log rank p <  0.0001 and c-index = 0.614). Moreover, we revealed 25 functional annotations, 15 gene ontology terms and 14 pathways that were significantly enriched in the genes that showed distinct mutation patterns in the different survival risk groups. These functional gene sets were used as new features for the survival prediction model. In particular, our results suggested that the Fanconi anemia pathway had an important role in breast cancer prognosis.

CONCLUSIONS

Our study indicated that the expression levels of the gene signatures remain the effective indicators for breast cancer survival prediction. Combining the gene expression information with other types of features derived from somatic mutations can further improve the performance of survival prediction. The pathways that were associated with survival risk suggested by our study can be further investigated for improving cancer patient survival.

Toward the precision breast cancer survival prediction utilizing combined whole genome-wide expression and somatic mutation analysis

Background

Breast cancer is the most common type of invasive cancer in woman. It accounts for approximately 18% of all cancer deaths worldwide. It is well known that somatic mutation plays an essential role in cancer development. Hence, we propose that a prognostic prediction model that integrates somatic mutations with gene expression can improve survival prediction for cancer patients and also be able to reveal the genetic mutations associated with survival.

Method

Differential expression analysis was used to identify breast cancer related genes. Genetic algorithm (GA) and univariate Cox regression analysis were applied to filter out survival related genes. DAVID was used for enrichment analysis on somatic mutated gene set. The performance of survival predictors were assessed by Cox regression model and concordance index(C-index).

Results

We investigated the genome-wide gene expression profile and somatic mutations of 1091 breast invasive carcinoma cases from The Cancer Genome Atlas (TCGA). We identified 118 genes with high hazard ratios as breast cancer survival risk gene candidates (log rank p <  0.0001 and c-index = 0.636). Multiple breast cancer survival related genes were found in this gene set, including FOXR2, FOXD1, MTNR1B and SDC1. Further genetic algorithm (GA) revealed an optimal gene set consisted of 88 genes with higher c-index (log rank p <  0.0001 and c-index = 0.656). We validated this gene set on an independent breast cancer data set and achieved a similar performance (log rank p <  0.0001 and c-index = 0.614). Moreover, we revealed 25 functional annotations, 15 gene ontology terms and 14 pathways that were significantly enriched in the genes that showed distinct mutation patterns in the different survival risk groups. These functional gene sets were used as new features for the survival prediction model. In particular, our results suggested that the Fanconi anemia pathway had an important role in breast cancer prognosis.

Conclusions

Our study indicated that the expression levels of the gene signatures remain the effective indicators for breast cancer survival prediction. Combining the gene expression information with other types of features derived from somatic mutations can further improve the performance of survival prediction. The pathways that were associated with survival risk suggested by our study can be further investigated for improving cancer patient survival.

Electronic supplementary material

The online version of this article (10.1186/s12920-018-0419-x) contains supplementary material, which is available to authorized users.

The inflammatory cytokine TNF contributes with RAC3-induced malignant transformation

RAC3 is a coactivator of steroid receptors and NF-κB. It is usually overexpressed in several tumors, contributes to maintain cancer stem cells and also to induce them when is overexpressed in non-tumoral cells. In this work, we investigated whether the inflammatory cytokine TNF may contribute to the transforming effects of RAC3 overexpression in the non-tumoral HEK293 cell line.

The study model included the HEK293 tumoral transformed cell line constitutively overexpressing RAC3 by stable transfection and control non-tumoral cells transfected with an empty vector. The HeLa and T47D tumoral cells that naturally overexpress RAC3 were used as positive control.

We found that TNF potentiated RAC3-induced mesenchymal transition, involving an increased E-Cadherin downregulation, Vimentin and SNAIL upregulation and enhanced migratory behavior. Moreover, concerning the molecular mechanisms by which TNF potentiates the RAC3 transforming action, they involve the IKK activation, which in addition induced the β-Catenin transactivation.

Our results demonstrate that although RAC3 overexpression could be a signal strong enough to induce cancer stem cells, the inflammatory microenvironment may be playing a key role contributing to the migratory and invasive phenotype required for metastasis and cancer persistence.

Role of RAC3 coactivator in the adipocyte differentiation

RAC3 is a member of the p160 family of steroid receptor coactivators and it is highly expressed in several human cancers, contributing to enhanced cell proliferation and cellular transformation. In this work, we have studied the role of RAC3 in adipogenesis in L-929 cells. Adipogenesis is a highly regulated process, involving cell cycle arrest and changes in the gene expression pattern required for morphological remodelling. We found that RAC3 expression levels are downregulated during adipocyte differentiation induced by specific stimulus. In addition, cells constitutively expressing low levels of RAC3 (shRNA), showed enhanced adipocyte differentiation which was evidenced by the early detection of the adipocyte markers Perilipin, PPARγ and Oil Red O staining. Moreover, RAC3 downregulation favoured cell arrest and autophagy. Early and late autophagy inhibitors blocked adipocyte differentiation in control cells, but partially inhibited shRAC3 differentiation, demonstrating that although autophagy is required for adipogenesis, additional signals could be trigged by RAC3 downregulation. We conclude that RAC3 is a key regulator of adipogenesis, since its downregulation generates the cellular arrest and autophagic responses that are required steps for this process.

Plac1 Is a Key Regulator of the Inflammatory Response and Immune Tolerance In Mammary Tumorigenesis

Plac1 is an X-linked trophoblast gene expressed at high levels in the placenta, but not in adult somatic tissues other than the testis. Plac1 however is re-expressed in several solid tumors and in most human cancer cell lines. To explore the role of Plac1 in cancer progression, Plac1 was reduced by RNA interference in EO771 mammary carcinoma cells. EO771 "knockdown" (KD) resulted in 50% reduction in proliferation in vitro and impaired tumor growth in syngeneic mice; however, tumor growth in SCID mice was equivalent to tumor cells expressing a non-silencing control RNA, suggesting that Plac1 regulated adaptive immunity. Gene expression profiling of Plac1 KD cells indicated reduction in several inflammatory and immune factors, including Cxcl1, Ccl5, Ly6a/Sca-1, Ly6c and Lif. Treatment of mice engrafted with wild-type EO771 cells with a Cxcr2 antagonist impaired tumor growth, reduced myeloid-derived suppressor cells and regulatory T cells, while increasing macrophages, dendritic cells, NK cells and the penetration of CD8+ T cells into the tumor bed. Cxcl1 KD phenocopied the effects of Plac1 KD on tumor growth, and overexpression of Cxcl1 partially rescued Plac1 KD cells. These results reveal that Plac1 modulates a tolerogenic tumor microenvironment in part by modulating the chemokine axis.

Identification of miRNAs as biomarkers for acquired endocrine resistance in breast cancer

Therapies targeting estrogen receptor α (ERα) including tamoxifen, a selective estrogen receptor modulator (SERM) and aromatase inhibitors (AI), e.g., letrozole, have proven successful in reducing the death rate for breast cancer patients whose initial tumors express ERα. However, about 40% of patients develop acquired resistance to these endocrine treatments. There is a critical need to develop sensitive circulating biomarkers that accurately identify signaling pathways altered in breast cancer patients resistant to endocrine therapies. Serum miRNAs have the potential to serve as biomarkers of the progression of endocrine-resistant breast cancer due to their cancer-specific expression and stability. Exosomal transfer of miRNAs has been implicated in metastasis and endocrine-resistance. This review focuses on miRNAs in breast tumors and in serum, including exosomes, from breast cancer patients that are associated with resistance to tamoxifen since it is best-studied.

Honokiol inhibits bladder cancer cell invasion through repressing SRC-3 expression and epithelial-mesenchymal transition

Urinary bladder cancer (UBC) is one of the most common urological cancer types. Muscle invasive bladder cancer possesses high propensity for metastasis with poor prognosis. Honokiol is a lignan isolated from Magnolia officinalis with high bioavailability and potent anticancer effects. The results of the present study demonstrated that honokiol significantly inhibited UBC cell migration and invasion in a dose-dependent manner compared with the vehicle-treated control group. In addition, honokiol treatment suppressed epithelial-mesenchymal transition by induction of E-cadherin and repression of N-cadherin. Honokiol was capable of significantly downregulating the expression of cell invasion-associated genes, steroid receptor coactivator-3 (SRC-3), matrix metalloproteinase (MMP)-2 and Twist1. Notably, the inhibition of UBC cell invasion by honokiol was reversed by reintroduction of oncoprotein SRC-3 expression, with the restoration of MMP-2 and Twist1, and reduction of E-cadherin expression. Furthermore, the results of the luciferase assay confirmed that SRC-3 could regulate Twist1 promoter activity. Taken together, the results of the present study suggest that honokiol is a promising agent against UBC cell invasion via downregulation of SRC-3 and its target genes.

Activating ESR1 Mutations Differentially Affect the Efficacy of ER Antagonists

Recent studies have identified somatic ESR1 mutations in patients with metastatic breast cancer and found some of them to promote estrogen-independent activation of the receptor. The degree to which all recurrent mutants can drive estrogen-independent activities and reduced sensitivity to ER antagonists like fulvestrant is not established. In this report, we characterize the spectrum of ESR1 mutations from more than 900 patients. ESR1 mutations were detected in 10%, with D538G being the most frequent (36%), followed by Y537S (14%). Several novel, activating mutations were also detected (e.g., L469V, V422del, and Y537D). Although many mutations lead to constitutive activity and reduced sensitivity to ER antagonists, only select mutants such as Y537S caused a magnitude of change associated with fulvestrant resistance in vivo Correspondingly, tumors driven by Y537S, but not D5358G, E380Q, or S463P, were less effectively inhibited by fulvestrant than more potent and bioavailable antagonists, including AZD9496. These data point to a need for antagonists with optimal pharmacokinetic properties to realize clinical efficacy against certain ESR1 mutants.Significance: A diversity of activating ESR1 mutations exist, only some of which confer resistance to existing ER antagonists that might be overcome by next-generation inhibitors such as AZD9496. Cancer Discov; 7(3); 277-87. ©2016 AACR.This article is highlighted in the In This Issue feature, p. 235.

Estrogen receptor alpha somatic mutations Y537S and D538G confer breast cancer endocrine resistance by stabilizing the activating function-2 binding conformation

Somatic mutations in the estrogen receptor alpha (ERα) gene (ESR1), especially Y537S and D538G, have been linked to acquired resistance to endocrine therapies. Cell-based studies demonstrated that these mutants confer ERα constitutive activity and antiestrogen resistance and suggest that ligand-binding domain dysfunction leads to endocrine therapy resistance. Here, we integrate biophysical and structural biology data to reveal how these mutations lead to a constitutively active and antiestrogen-resistant ERα. We show that these mutant ERs recruit coactivator in the absence of hormone while their affinities for estrogen agonist (estradiol) and antagonist (4-hydroxytamoxifen) are reduced. Further, they confer antiestrogen resistance by altering the conformational dynamics of the loop connecting Helix 11 and Helix 12 in the ligand-binding domain of ERα, which leads to a stabilized agonist state and an altered antagonist state that resists inhibition.

Around one in every eight women will be diagnosed with breast cancer in their lifetime. Hormone-based therapies – also referred to antiestrogen drugs – target a protein called estrogen receptor alpha and are effective treatments for the majority of these cancers. Unfortunately, about half of patients will develop recurrent breast cancers even though the cancer continues to produce the target of the drugs.

The estrogen receptor alpha drives breast cancer in a number of ways, many of which require the receptor to be activated by binding to the hormone estrogen. When estrogen binds it causes the receptor to change shape to expose a surface where other proteins called coactivators can bind. Once a coactivator is bound, the estrogen receptor is active and signals the cancer cell to grow, divide, invade local tissues, and spread to new sites in the body.

Antiestrogen drugs competitively block the binding of estrogen to the receptor and cause the receptor to take on a different shape that inhibits the binding of the coactivator. However, recent studies identified mutations at specific sites in the gene that encodes estrogen receptor alpha in a large subset of patients with breast cancers that have spread. These mutations make the receptor resistant to antiestrogen drugs, and two mutations (called Y537S and D538G) account for approximately 70% of cases. However, it was not clear how these mutations altered the activity of estrogen receptor alpha at the molecular level.

Fanning, Mayne, Dharmarajan et al. now show these two most common mutations allow estrogen receptor alpha to bind to the coactivator in the absence of hormone. This unfortunately also reduces the effectiveness of one of the mostly widely administered antiestrogen therapies – a drug called tamoxifen. However, Fanning, Mayne, Dharmarajan et al. also show that the newer and more potent antiestrogens that are currently under examination in clinical trials should be highly effective at treating the cancers with the mutated versions of estrogen receptor alpha.

Applying the knowledge gained from these new findings toward the development of new antiestrogens could help reverse the impact of these common mutations. If successful, these new drugs will provide life-saving treatments for many breast cancer patients.

Selection and Application of DNA Aptamer Against Oncogene Amplified in Breast Cancer 1

Amplified in breast cancer 1 (AIB1), also known as steroid receptor coactivator 3 (SRC-3), is a transcriptional coactivator that interacts with nuclear receptors and other transcription factors to enhance their effects on target gene transcription. AIB1, which acts as a major oncogene, is highly expressed in many human cancers, and has been demonstrated to be a key regulator for tumor initiation, progression, metastasis, invasion, and survival. Recruitment of the transcriptional factor CBP/p300 by CBP/p300-interaction domain (CID) of AIB1 is essential for its transcriptional activation function. In this research, we isolated a DNA aptamer AY-3 that binds to AIB1-CID from a random oligonucleotide library using in vitro screening technology-Systematic Evolution of Ligands by EXponential enrichment (SELEX). The binding affinity of the aptamer to AIB1-CID fusion protein is in the nanomolar range. More importantly, the aptamer was found to disrupt in the interaction between p300 and AIB1. This aptamer has great potential to serve as a therapeutic agent for cancer by inhibiting the coactivation of AIB1.

Association of NCOA3 polymorphisms with Dyslipidemia in the Chinese Han population

Background

Nuclear receptor coactivator-3 (NCOA3) is involved in various physiological processes. Emerging evidence from previous studies using animal models suggests that the NCOA3 gene (NCOA3) plays a critical role in lipid metabolism as well as adipogenesis and obesity. The present study aims to investigate the association between NCOA3 SNPs and dyslipidemia in the Chinese Han population.

Methods

Five hundred and twenty-nine (529) Chinese Han subjects were recruited. Four tag SNPs (rs2425955G > T, rs6066394T > C, rs10485463C > G, and rs6094753G > A) in NCOA3, selected from the HapMap website, were genotyped using MALDI-TOF mass spectrometry. Data analysis was performed using SPSS 16.0, SNPStats and haploview 4.2.

Results

Four SNPs (rs2425955, rs6066394, rs10485463, and rs6094753) were associated with triglyceride levels. Except for SNP rs10485463, genotype distributions and allele frequencies of the other three NCOA3 SNPs (rs2425955, rs6066394, and rs6094753) were significantly different between hypertriglyceridemia subjects and normal group. Significant differences were also observed in allele frequencies and genotype distributions of SNP rs10485463 between low-HDL cholesterolemia subjects and normal group. Carriers of rs2425955 T allele had a lower risk of hypertriglyceridemia compared to GG genotype. Similar results were observed from rs6094753. Subjects with rs6066394 CT genotype had a lower risk of hypertriglyceridemia than those with the TT genotype; however, CC and TT genotypes showed no significant difference in the risk of hypertriglyceridemia. Similar results were found in the association between rs6066394 and hypercholesterolemia. The variant alleles of rs2425955, rs6066394 and rs6094753 were associated with a lower risk of hypertriglyceridemia compared with the wild-type alleles. The G allele of rs10485463 was associated with an increased risk of low-HDL cholesterolemia. In the log-additive model the association between rs2425955 and hypertriglyceridemia remained significant after Bonferroni correction, and genotypes with variant alleles were associated with a lower risk of hypertriglyceridemia.

Conclusions

In summary, this study demonstrated that variation in NCOA3 might influence the risk of dyslipidemia and serum lipid levels in Chinese Han population.

Roles for miRNAs in endocrine resistance in breast cancer

Therapies targeting estrogen receptor alpha (ERα), including selective ER modulators such as tamoxifen, selective ER downregulators such as fulvestrant (ICI 182 780), and aromatase inhibitors such as letrozole, are successfully used in treating breast cancer patients whose initial tumor expresses ERα. Unfortunately, the effectiveness of endocrine therapies is limited by acquired resistance. The role of microRNAs (miRNAs) in the progression of endocrine-resistant breast cancer is of keen interest in developing biomarkers and therapies to counter metastatic disease. This review focuses on miRNAs implicated as disruptors of antiestrogen therapies, their bona fide gene targets and associated pathways promoting endocrine resistance.

ERK3 promotes endothelial cell functions by upregulating SRC-3/SP1-mediated VEGFR2 expression

Despite a regain of interest recently in ERK3 kinase signaling, the molecular regulations of both ERK3 gene expression and protein kinase activity are still largely unknown. While it is shown that disruption of ERK3 gene causes neonatal lethality, cell type-specific functions of ERK3 signaling remain to be explored. In this study, we report that ERK3 gene expression is upregulated by cytokines through c-Jun in endothelial cells; c-Jun binds to the ERK3 gene and regulates its transcription. We further reveal a new role for ERK3 in regulating endothelial cell migration, proliferation and tube formation by upregulating SRC-3/SP-1-mediated VEGFR2 expression. The underlying molecular mechanism involves ERK3-stimulated formation of a transcriptional complex involving coactivator SRC-3, transcription factor SP-1 and the secondary coactivator CBP. Taken together, our study identified a molecular regulatory mechanism of ERK3 gene expression and revealed a previously unknown role of ERK3 in regulating endothelial cell functions.

The levels of RAC3 expression are up regulated by TNF in the inflammatory response

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The inflammatory response increases the expression of RAC3 in vitro and in vivo.

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TNF induces the increase of RAC3 at transcriptional level through NF-κB activation.

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Glucocorticoids also induce the increase of RAC3 expression levels.

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RAC3 appears to be essential for NF-κB- and GR-mediated transcription.

RAC3 is a coactivator of glucocorticoid receptor and nuclear factor-κB (NF-κB) that is usually over-expressed in tumors and which also has important functions in the immune system. We investigated the role of the inflammatory response in the control of RAC3 expression levels in vivo and in vitro. We found that inflammation regulates RAC3 levels. In mice, sub-lethal doses of lipopolysaccharide induce the increase of RAC3 in spleen and the administration of the synthetic anti-inflammatory glucocorticoid dexamethasone has a similar effect. However, the simultaneous treatment with both stimuli is mutually antagonistic. In vitro stimulation of the HEK293 cell line with tumor necrosis factor (TNF), one of the cytokines induced by lipopolysaccharide, also increases the levels of RAC3 mRNA and protein, which correlates with an enhanced transcription dependent on the RAC3 gene promoter. We found that binding of the transcription factor NF-κB to the RAC3 gene promoter could be responsible for these effects. Our results suggest that increase of RAC3 during the inflammatory response could be a molecular mechanism involved in the control of sensitivity to both pro- and anti-inflammatory stimuli in order to maintain the normal healthy course of the immune response.

Cryo-EM techniques to resolve the structure of HSV-1 capsid-associated components

Electron cryo-microscopy has become a routine technique to determine the structure of biochemically purified herpes simplex virus capsid particles. This chapter describes the procedures of specimen preparation by cryopreservation; low dose and low temperature imaging in an electron cryo-microscope; and data processing for reconstruction. This methodology has yielded subnanometer resolution structures of the icosahedral capsid shell where α-helices and β-sheets of individual subunits can be recognized. A relaxation of the symmetry in the reconstruction steps allows us to resolve the DNA packaging protein located at one of the 12 vertices in the capsid.

Up-regulation of nuclear receptor coactivator amplified in breast cancer-1 in papillary thyroid carcinoma correlates with lymph node metastasis

INTRODUCTION

Nuclear receptor coactivator amplified in breast cancer-1 (AIB1), a new oncogenic coactivator, is commonly overexpressed and amplified in variety of human cancers. However, the expression of AIB1 in papillary thyroid carcinoma (PTC), the major histologic type of thyroid cancer, and its clinical significance are still unclear.

MATERIALS AND METHODS

AIB1 expression in PTC was examined by immunohistochemistry using tissue microarrays comprised of 90 primary PTC, 46 matched lymph node, and 20 normal thyroid tissue specimens in this study.

RESULTS

In the normal thyroid specimens, AIB1 expression was either absent or at low levels. In contrast, AIB1 overexpression was detected in 50 of 83 (60.2 %) primary PTC specimens. Up-regulated AIB1 was evident in 39 of 46 (73.5 %) matched lymph nodes. Overexpression of AIB1 was observed more frequently in PTCs with lymph node metastasis [N1a/N1b, 39/46 (73.5 %)] versus PTCs without lymph node metastasis [N0, 14/34 (41.2 %)]. Furthermore, high-level AIB1 expression was only observed in the lymph node-positive specimens. Moreover, we found no correlation between AIB1 expression and ER expression in PTC tissues.

CONCLUSIONS

Our findings suggest that overexpression of AIB1 may be a biomarker for tumorigenesis and progression of PTC and may play an important role in its acquisition of a metastatic phenotype.

β-Estradiol-dependent activation of the JAK/STAT pathway requires p/CIP and CARM1

The steroid receptor coactivator p/CIP, also known as SRC-3, is an oncogene commonly amplified in breast and ovarian cancers. p/CIP is known to associate with coactivator arginine methyltransferase 1 (CARM1) on select estrogen responsive genes. We have shown, using a ChIP-on-chip approach, that in response to stimulation with 17β-estradiol (E2), the p/CIP/CARM1 complex is recruited to 204 proximal promoters in MCF-7 cells. Many of the complex target genes have been previously implicated in signaling pathways related to oncogenesis. Jak2, a member of the Jak/Stat signaling cascade, is one of the direct E2-dependent targets of the p/CIP/CARM1 complex. Following E2-treatment, histone modifications at the Jak2 promoter are reflective of a transcriptionally permissive gene, and modest changes in RNA and protein expression lead us to suggest that an additional factor(s) may be required for a more notable transcriptional and functional response. Bioinformatic examination of the 204 proximal promoter sequences of p/CIP/CARM1 targets supports the idea that transcription factor crosstalk is likely the favored mechanism of E2-dependent p/CIP/CARM1 complex recruitment. This data may have implications towards understanding the oncogenic role of p/CIP in breast cancer and ultimately allow for the identification of new prognostic indicators and/or viable therapeutic targets.

Prognostic relevance of AIB1 (NCoA3) amplification and overexpression in breast cancer

AIB1 (amplified in breast cancer 1) is an estrogen receptorα (ERα) co-activator, known to be amplified and overexpressed in a fraction of breast cancers. It has been linked to prognosis and tamoxifen resistance. However, results have been ambiguous. The different functions of AIB1 in ERα-positive and -negative disease are poorly understood. Therefore, we analyzed the clinical significance of AIB1 in breast cancer with respect to ERα-status and characterized the subgroups. 2,197 breast carcinomas sampled on a pre-existing tissue microarray (TMA) were analyzed for AIB1 expression and amplification by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH).

RESULTS

AIB1 expression was detected in 60 % of the tumors. It was associated with tumor size (p = 0.003), high histological grade (p < 0.0001), poor disease-specific, and overall survival (p = 0.0018 and p = 0.003). There was a strong inverse relationship between AIB1 and ERα expression (p < 0.0001). AIB1 overexpression was associated with increased Ki67 labeling index (p < 0.0001), even if analyzed for different ER expression levels. AIB1 amplification was found in 11 % of the carcinomas. It was associated with high histological grade (p = 0.0012), lymph node involvement (p = 0.0163), and poor disease-specific survival (p = 0.0032) but not with overall survival (p = 0.1672) or ER status (p = 0.4456). If ER-positive tumors were stratified according to their AIB1 amplification status, there was a significant worse disease-specific survival in cases showing AIB1 amplification (p = 0.0017). AIB1 expression is associated with unfavorable prognosis and tumor phenotype. It seems to unfold its oncogenic potential at least in part independent from its role as an ERα co-activator. AIB1 has an impact on cell cycle regulation in ERα-positive as well as ERα-negative tumors. Furthermore, AIB1 amplification characterizes a subgroup of ERα-positive breast cancer with worse outcome. Therefore, AIB1 might be helpful to identify those ERα-positive breast cancers patients who are candidates for adjuvant chemotherapy.

The role of AIB1 in breast cancer

Amplified in breast cancer 1 (AIB1) is a member of the p160 steroid receptor coactivator family that mediates the transcriptional activities of nuclear receptors including estrogen receptor (ER) and progesterone receptor (PR), as well as certain other transcription factors, including E2F1 and p53. AIB1 is widely implicated in nuclear receptor-mediated diseases, particularly malignant diseases, including breast, prostate, gastric and pancreatic cancers. AIB1 was initially implicated in hormone-dependent breast cancer, where increasing levels of AIB1 mRNA and protein were detected in some of these specimens and the overexpression of AIB1 in mice led to an increased incidence of tumors. More recent studies revealed that AIB1 also affects the growth of hormone-independent breast cancer via signaling pathways such as those of E2F1, IGF-I, EGF and PI3K/Akt/mTOR. The pleiotropic effect of AIB1 and the roles it plays in both normal development and cancer have presented a great challenge to formulating an effective therapeutic strategy for breast cancer. In this review, we highlight the significant progress made with the recent findings and present an overview of the current understanding of the influence of AIB1 on breast cancer via hormone-dependent and -independent signaling pathways.

The interaction between hepatitis B virus X protein and AIB1 oncogene is required for the activation of NFκB signal transduction

We identified the interaction between HBV X (HBx) protein and the oncogene AIB1 (amplified in breast cancer 1). A serine/proline motif (SSPSPS) in HBx was found to be required for the interaction. Two LXD motifs [LLXX(X)L, X means any amino acids], LLRNSL and LLDQLHTLL in AIB1 were also found to be involved in the HBx-AIB1 interaction. The HBx-AIB1 interaction was important for the activation of NFκB signal transduction, the HBx mutant that did not interact with AIB1showed dramatically lower NFκB activation activity than the WT HBx. These findings contribute to the new understanding on signal transduction activation mechanisms of HBx.

The RIP140 gene is a transcriptional target of E2F1

RIP140 is a transcriptional coregulator involved in energy homeostasis and ovulation which is controlled at the transcriptional level by several nuclear receptors. We demonstrate here that RIP140 is a novel target gene of the E2F1 transcription factor. Bioinformatics analysis, gel shift assay, and chromatin immunoprecipitation demonstrate that the RIP140 promoter contains bona fide E2F response elements. In transiently transfected MCF-7 breast cancer cells, the RIP140 promoter is transactivated by overexpression of E2F1/DP1. Interestingly, RIP140 mRNA is finely regulated during cell cycle progression (5-fold increase at the G1/S and G2/M transitions). The positive regulation by E2F1 requires sequences located in the proximal region of the promoter (-73/+167), involves Sp1 transcription factors, and undergoes a negative feedback control by RIP140. Finally, we show that E2F1 participates in the induction of RIP140 expression during adipocyte differentiation. Altogether, this work identifies the RIP140 gene as a new transcriptional target of E2F1 which may explain some of the effect of E2F1 in both cancer and metabolic diseases.

Steroid receptor coactivator-3 differentially regulates the inflammatory response in peritoneal macrophages

Steroid receptor coactivator-3 (SRC-3) is a transcriptional coactivator that plays an important role in the regulation of cytokine mRNA translation. In the present study, SCR-3 gene knockout mice were used to study the effects of SCR-3 on the regulation of the inflammatory response in peritoneal macrophages induced by lipopolysaccharides (LPS). Peritoneal macrophages (PMs) of SRC-3^−/− mice showed a decrease in the release of TNF-α, IL-1β and IL-6, and an increase in the release of IL-10. Furthermore, results of RT-PCR also showed that levels of TNF-α, IL-1β and IL-6 mRNA expression were significantly lower, while the level of IL-10 mRNA expression was higher in the SRC-3^−/− mice, compared to those of wild-type mice, following treatment with LPS (p<0.01). In addition, western blotting revealed that: i) the extent of reduction of the glucocorticoid receptor in PMs from SRC-3^−/− mice was significantly lower than that in wild-type mice (p<0.01); ii) the extent of increase of AP-1 in PMS from SRC-3^−/− mice was significantly lower than that in wild-type mice (p<0.01); iii) the extent of increase of NF-κB p65 in PMs from SRC-3^−/− mice was significantly higher than that in wild-type mice (p<0.01). Collectively, our studies revealed that SRC-3 may play a key role in the maintenance of innate immunity. Furthermore, absence of the SRC-3 protein may result in the partial loss of inflammation and phagocytosis barrier function, including suppression of LPS-induced transcriptional activity, release of TNF-α, IL-1β and IL-6, and obstruction of the function of phagocytes and elimination of bacteria, as well as their production.

Recovering protein-protein and domain-domain interactions from aggregation of IP-MS proteomics of coregulator complexes

Coregulator proteins (CoRegs) are part of multi-protein complexes that transiently assemble with transcription factors and chromatin modifiers to regulate gene expression. In this study we analyzed data from 3,290 immuno-precipitations (IP) followed by mass spectrometry (MS) applied to human cell lines aimed at identifying CoRegs complexes. Using the semi-quantitative spectral counts, we scored binary protein-protein and domain-domain associations with several equations. Unlike previous applications, our methods scored prey-prey protein-protein interactions regardless of the baits used. We also predicted domain-domain interactions underlying predicted protein-protein interactions. The quality of predicted protein-protein and domain-domain interactions was evaluated using known binary interactions from the literature, whereas one protein-protein interaction, between STRN and CTTNBP2NL, was validated experimentally; and one domain-domain interaction, between the HEAT domain of PPP2R1A and the Pkinase domain of STK25, was validated using molecular docking simulations. The scoring schemes presented here recovered known, and predicted many new, complexes, protein-protein, and domain-domain interactions. The networks that resulted from the predictions are provided as a web-based interactive application at http://maayanlab.net/HT-IP-MS-2-PPI-DDI/.

Effects of SCR-3 on the immunosuppression accompanied with the systemic inflammatory response syndrome

Steroid receptor coactivator-3 (SRC-3) is a multifunctional protein that plays an important role in mammary gland growth, development, and tumorigenesis. In this study, SCR-3 gene knockout mice were used to study the effects of SCR-3 on the immunosuppression accompanied with systemic inflammatory response syndrome (SIRS). Bacterial clearance assay was performed by blood culture and frozen sections, and the results showed that the absence of SCR-3 protein serious damaged the innate immune system and the body's ability to inactivate or phagocytosis of bacteria was significantly decreased, and the absence of SCR-3 protein also weakened phagocytes' ability to degrade bacteria and their metabolites. Furthermore, animal model of inflammatory reaction was established and the immune function was determined, and the results revealed that SRC-3 protein may play an important role in maintenance of T-cells' immune function, and severe T-cell immune function disorder would be resulted once SRC-3 protein is missing. In addition, the results of our study showed the steady-state of lymphocyte subsets was destroyed after SIRS, leading the suppression of cellular immune function, and the absence of SCR-3 protein may aggravate the suppression of T-lymphocyte function. Therefore, the present study demonstrated that the absence of SCR-3 protein would aggravate immunosuppression. In addition, SRC-3 protein is a significant regulator of infection and inflammation, and SRC-3 protein play an essential role in the development of immunosuppression accompanied with SIRS.

Peptidyl-prolyl cis–trans isomerase Pin1 in ageing, cancer and Alzheimer disease

Phosphorylation of proteins on serine or threonine residues preceding proline is a key signalling mechanism in diverse physiological and pathological processes. Pin1 (peptidyl-prolyl cis–trans isomerase) is the only enzyme known that can isomerise specific Ser/Thr-Pro peptide bonds after phosphorylation and regulate their conformational changes with high efficiency. These Pin1-catalysed conformational changes can have profound effects on phosphorylation signalling by regulating a spectrum of target activities. Interestingly, Pin1 deregulation is implicated in a number of diseases, notably ageing and age-related diseases, including cancer and Alzheimer disease. Pin1 is overexpressed in most human cancers; it activates numerous oncogenes or growth enhancers and also inactivates a large number of tumour suppressors or growth inhibitors. By contrast, ablation of Pin1 prevents cancer, but eventually leads to premature ageing and neurodegeneration. Consistent with its neuroprotective role, Pin1 has been shown to be inactivated in neurons of patients with Alzheimer disease. Therefore, Pin1-mediated phosphorylation-dependent prolyl isomerisation represents a unique signalling mechanism that has a pivotal role in the development of human diseases, and might offer an attractive new diagnostic and therapeutic target.

SRC-3 has a role in cancer other than as a nuclear receptor coactivator

Steroid receptor coactivator-3 (SRC-3), also known as AIB1, is a member of the p160 steroid receptor coactivator family. Since SRC-3 was found to be amplified in breast cancer in 1997, the role of SRC-3 in cancer has been broadly investigated. SRC-3 initially was identified as a transcriptional coactivator for nuclear receptors such as the estrogen receptor (ER), involved in the proliferation of hormone-dependent cancers. However, increasing clinical evidence shows that dysregulation of SRC-3 expression in several human hormone-independent cancers is correlated with pathological factors and clinical prognosis. Recently, both in vivo and in vitro studies demonstrate that SRC-3 may influence a number of cancer cellular processes in several ways independent of nuclear receptor signaling. In addition, an SRC-3 transgenic mice model shows that SRC-3 induces tumors in several mouse tissues. These results indicate that the role of SRC-3 in cancer is not just as a nuclear receptor coactivator. The focus of this review is to examine possible SRC-3 roles in cancer, other than as a nuclear receptor coactivator.

Genomic instability and oncogene amplifications in colorectal adenomas predict recurrence and synchronous carcinoma

Individual colorectal adenomas have different propensities to progress to invasive disease. In this study, we explored whether these differences could be explained by gene copy number alterations. We evaluated 18 adenomas of patients without synchronous or subsequent carcinoma (6.5 years follow-up), 23 adenomas of carcinoma patients, and 6 related carcinomas. All samples were measured for their DNA ploidy status. Centromere probes for chromosomes 17 and 18, as well as gene-specific probes for SMAD7, EGFR, NCOA3, TP53, MYC, and RAB20 were assessed by multicolor fluorescence in situ hybridization. An increased genomic instability index of CEP17, SMAD7, and EGFR, as well as TP53 deletions and MYC amplifications defined adenomas of patients with synchronous carcinoma (P<0.05). Diploid NCOA3 signal counts were associated with longer adenoma recurrence-free surveillance (P=0.042). In addition, NCOA3, MYC, EGFR, and RAB20 amplifications, as well as TP53 deletions correlated with increased DNA stem line values and/or aneuploidy in adenomas (P<0.05). Furthermore, aberrations of NCOA3, MYC, and RAB20 were associated with histopathologically defined high-risk adenomas (P<0.05). RAB20 amplifications were also correlated with high-grade dysplastic adenomas (P=0.002). We conclude that genomic instability in colorectal adenomas is reflected by EGFR, MYC, NCOA3, and RAB20 amplifications that do correlate with histomorphological features and are indicative for adenoma recurrence and the presence of synchronous carcinomas.

Mouse models of follicular and papillary thyroid cancer progression

A significant number of well-differentiated thyroid cancers progress or recur, becoming resistant to current therapeutic options. Mouse models recapitulating the genetic and histological features of advanced thyroid cancer have been an invaluable tool to dissect the mechanisms involved in the progression from indolent, well differentiated tumors to aggressive, poorly differentiated carcinomas, and to identify novel therapeutic targets. In this review, we focus on the lessons learned from models of epithelial cell-derived thyroid cancer showing progression from hyperplastic lesions to locally invasive and metastatic carcinomas.

Temperature-dependent structural changes in intrinsically disordered proteins: formation of alpha-helices or loss of polyproline II?

Structural characterization of intrinsically disordered proteins (IDPs) is mandatory for deciphering their potential unique physical and biological properties. A large number of circular dichroism (CD) studies have demonstrated that a structural change takes place in IDPs with increasing temperature, which most likely reflects formation of transient alpha-helices or loss of polyproline II (PPII) content. Using three IDPs, ACTR, NHE1, and Spd1, we show that the temperature-induced structural change is common among IDPs and is accompanied by a contraction of the conformational ensemble. This phenomenon was explored at residue resolution by multidimensional NMR spectroscopy. Intrinsic chemical shift referencing allowed us to identify regions of transiently formed helices and their temperature-dependent changes in helicity. All helical regions were found to lose rather than gain helical structures with increasing temperature, and accordingly these were not responsible for the change in the CD spectra. In contrast, the nonhelical regions exhibited a general temperature-dependent structural change that was independent of long-range interactions. The temperature-dependent CD spectroscopic signature of IDPs that has been amply documented can be rationalized to represent redistribution of the statistical coil involving a general loss of PPII conformations.

Multiple Routes to Oestrogen Antagonism

Several lines of evidence attest to the existence of alternative ligand binding sites on the oestrogen receptor (ER), including non-competitive inhibition by trilostane or tamoxifen. It is possible that the inhibitory action of conventional oestrogen agonists at high concentrations may indicate that they too interact at alternative ER sites, albeit at low affinity. To test this possibility an oestrogen reporter assay was used to compare the activity of different oestrogens and antagonists in breast cancer and prostate cell lines. All four cell lines tested contained different amounts of oestrogen receptor α (ERα), ERβ, progesterone receptor and coregulator mRNA. Though differences were observed in response to stimulation and inhibition, these correlated only with the presence or absence of ERα, and not with the other components. Thus stimulation of the reporter by oestradiol and oestrone was biphasic in the breast cancer cells, while prostate cells were unable to respond. Only T47D cells were stimulated by oestriol or diethylstilboestrol, however reporter activity of all the cell lines was repressed by 10μM diethylstilboestrol. Reporter activity of MCF-7 cells was inhibited by tamoxifen, raloxifene and ICI 182,780, but stimulated by trilostane, yet all these antioestrogens inhibited agonist-stimulated activity. Trilostane also inhibited the agonism seen in cells co-treated with E2 and tamoxifen. It is clear that several of the compounds tested may have either agonist or antagonist effects under different conditions and at different concentrations, acting through ERα alone. Though biphasic dose response curves, or hormesis, have been attributed to various mechanisms, we here provide evidence that alternative ligand binding sites may contribute to this phenomenon.

SRC-3 deficient mice developed fat redistribution under high-fat diet

An emerging concept suggests that an aberrant distributed body fat is closely linked to the occurrence of metabolic abnormalities. Mice deficient in steroid receptor coactivator-3 (SRC-3) are shown to be protected against high-fat diet (HFD) induced obesity but little is known about whether visceral (VAT) and subcutaneous adipose tissue (SCAT) distribute differently in SRC-3(-/-) mice versus SRC-3(+/+) mice. Here we reported that under HFD, fat redistributed between VAT and subcutaneous area of SRC-3(-/-) mice. When VAT/SCAT weight ratio (VAT/SCAT ratio) was calculated, SRC-3(-/-) mice had significantly elevated VAT/SCAT ratio in HFD versus normal diet (ND), while VAT/SCAT ratio was similar in SRC-3(+/+) mice under ND and HFD. Serological changes in SRC-3(-/-) mice paralleled the altered fat distribution. In SRC-3(-/-) mice, assays on gene expression revealed an increase in adipogenesis in VAT versus SCAT and an elevation in thermogenesis and lipolysis in SCAT versus VAT, which could explain the preferential fat accumulation in SRC-3(-/-) VAT. Our results presented in vivo evidence that SRC-3 deficiency could lead to fat redistribution under HFD in mice and provided new clues to researches on the pathogenesis of fat redistribution.

Estrogen-dependent and estrogen-independent mechanisms contribute to AIB1-mediated tumor formation

We have previously reported the oncogenic properties of the gene amplified in breast cancer 1 (AIB1), a member of the p160 family of hormone receptor coactivators. In a transgenic mouse model, AIB1 overexpression resulted in a high incidence of tumors in various tissues, including mammary gland, uterus, lung, and pituitary. To determine whether the AIB1 oncogenicity in this model depended on its function as an estrogen receptor (ER) coactivator, we abolished ER signaling through two independent approaches, by performing ovariectomy on AIB1 transgenic (AIB1-tg) mice to prevent gonadal estrogen production and by crossing AIB1-tg mice with ERalpha-null mutant mice. Ovariectomized (ovx) mice, but not AIB1 x ERalpha-/- mice, still developed mammary gland hyperplasia and ductal carcinoma in situ. Both approaches, however, completely prevented the development of invasive mammary tumors, indicating that invasive mammary tumor formation is strictly estrogen dependent. Once developed, AIB1-induced mammary tumors can subsequently lose their dependence on estrogen: Injection of ERalpha(+) tumor cell lines derived from such tumors into ovx or untreated wild-type mice resulted in a similar rate of tumor growth in both groups. Surprisingly, however, ovx mice had an approximately 4-fold higher rate of metastasis formation, suggesting that estrogen provided some protection from metastasis formation. Lastly, our experiments identified oncogenic functions of AIB1 that are independent of its ER coactivation, as both approaches, ovariectomy and ER-/- crosses, still resulted in a high incidence of tumors in the lung and pituitary. We therefore conclude that AIB1 can exert its oncogenicity through tissue-specific estrogen-dependent and estrogen-independent functions.

Natural mixtures of persistent organic pollutants (POP) increase weight gain, advance puberty, and induce changes in gene expression associated with steroid hormones and obesity in female zebrafish

In the present study, developmental and reproductive effects of lifelong exposure to environmental relevant concentrations of two natural mixtures of persistent organic pollutants (POP) were investigated using classical and molecular methods in a controlled zebrafish model. The mixtures used were extracted from burbot (Lota lota) liver originating from freshwater systems in Norway: one mixture with high levels and one mixture with background levels of polybrominated diphenyl ethers (PBDE), polychlorinated biphenyls (PCB), and dichlorodiphenyltrichloroethane metabolites (DDT). The concentration of POP measured in the zebrafish ranged from levels detected in wild fish from Lake Mjøsa to concentrations reported in human and wildlife populations, indicating that the experimental fish were exposed to concentrations comparable with wild fish. Phenotypic effects observed in both exposure groups included earlier onset of puberty, increased male/female sex ratio, and differences in body weight at 5 mo of age. Interestingly, genome-wide transcription profiling showed changes in regulation of genes involved in endocrine signaling and growth. The transcriptomics changes include key regulator genes for steroid hormone functions (ncoa3), and growth (c/ebp, ncoa3). The effects observed in the experimental zebrafish model raise the question whether chemical pollution represents a risk to reproductive health of wild fish inhabitating the freshwater system.

Estrogen-induced interaction between KLF5 and estrogen receptor (ER) suppresses the function of ER in ER-positive breast cancer cells

Kruppel-like factor 5 (KLF5) is implicated in human breast cancer by frequent genomic deletion and expressional deregulation, but the molecular mechanisms by which KLF5 affects breast tumorigenesis are still unknown. This study was conducted to examine whether and how KLF5 affects the function of estrogen receptor (ER) in breast cancer cells. Using different cell lines, we found that restored expression of KLF5 inhibited estrogen-promoted cell proliferation in ER-positive MCF-7 and T-47D cell lines but had no effect on ER-negative SK-BR-3 cells. Transcriptional activity of ER was also suppressed by KLF5, as detected by using estrogen-stimulated ER responsive element-mediated reporter assay and expression analysis of ER target genes including c-MYC and Cathepsin D (CSTD). Chromatin immunoprecipitation assays showed that KLF5 inhibited ERalpha binding to the promoter of c-myc and CSTD. Furthermore, estrogen induced an interaction between KLF5 and ERalpha. These results suggest that KLF5 inhibits the function of ERalpha in gene regulation and cell proliferation through protein interaction that interrupts the binding of ERalpha to target gene promoters to prevent target gene induction.

Estrogen-related receptor alpha expression and function is associated with the transcriptional coregulator AIB1 in breast carcinoma

The significance of the estrogen-related receptor alpha (ERRalpha) as prognostic marker for poor clinical outcome in breast carcinoma has recently been reported. Transcriptional activity of nuclear receptors such as ERRalpha depends on coregulatory proteins. Thus, we compared the expression of different receptors, coregulators, and target genes on RNA and protein level in identical primary breast tumor samples (n = 48). We found a positive correlation between the transcripts of ERRalpha and AIB1 (amplified in breast cancer-1), a coactivator overexpressed in breast cancers and associated with resistance to antihormone treatment. These data were confirmed on protein level, studying an independent patient collection (n = 257). Expression of the estrogen-regulated gene pS2 was associated with ERRalpha only in tumors, where estrogen receptor (ERalpha) expression was low or absent. In ERalpha high expressing tumors, no correlation of ERRalpha and pS2 was observed. AIB1 interacts directly with ERRalpha as shown by fluorescence-resonance energy transfer, mammalian two-hybrid, and coimmunoprecipitation assays with endogenous proteins. It enhances ERRalpha transcriptional activity in ERalpha-negative breast cancer cell lines as shown in functional reporter gene assays. Blocking ERRalpha with an inverse agonist abolished interaction and coactivation by AIB1. Recruitment of both proteins to ERRalpha target gene promoters further supports the significance of their interaction. Our findings identify AIB1 as functionally relevant cofactor for ERRalpha in breast carcinoma. ERRalpha/AIB1 complexes may control estradiol-regulated genes in a hormone-independent manner. Accordingly, ERRalpha might be a rewarding target for treatment of endocrine-resistant tumors.