Steroid receptor coactivator-1 coactivates activating protein-1-mediated transactivations through interaction with the c-Jun and c-Fos subunits

Significant Association of Estrogen Receptor-β Isoforms and Coactivators in Breast Cancer Subtypes

Nuclear receptor coregulators are the principal regulators of Estrogen Receptor (ER)-mediated transcription. ERβ, an ER subtype first identified in 1996, is associated with poor outcomes in breast cancer (BCa) subtypes, and the coexpression of the ERβ1 isoform and AIB-1 and TIF-2 coactivators in BCa-associated myofibroblasts is associated with high-grade BCa. We aimed to identify the specific coactivators that are involved in the progression of ERβ-expressing BCa. ERβ isoforms, coactivators, and prognostic markers were tested using standard immunohistochemistry. AIB-1, TIF-2, NF-kB, p-c-Jun, and/or cyclin D1 were differentially correlated with ERβ isoform expression in the BCa subtypes and subgroups. The coexpression of the ERβ5 and/or ERβ1 isoforms and the coactivators were found to be correlated with a high expression of P53, Ki-67, and Her2/neu and large-sized and/or high-grade tumors in BCa. Our study supports the notion that ERβ isoforms and coactivators seemingly coregulate the proliferation and progression of BCa and may provide insight into the potential therapeutic uses of the coactivators in BCa.

NCOA3 is a critical oncogene in thyroid cancer via the modulation of major signaling pathways

PURPOSE

The Nuclear Receptor Coactivator (NCOA3, also known as SRC-3, AIB1, p/CIP, RAC3, ACTR, and TRAM1), acts as an oncogene in multiple tumors, but its biological function in thyroid cancer remains unclear. This study was designed to explore the role of NCOA3 in thyroid cancer.

METHODS

The study assessed NCOA3 expression in thyroid cancer and their matched non-cancerous thyroid tissues at mRNA and protein levels. Then we evaluated the effect of NCOA3 on malignant activities of thyroid cancer cells. To better understand the oncogenic role of NCOA3 in thyroid tumorigenesis, we tested the effect of NCOA3 on major proteins related to thyroid cancer.

RESULTS

Our data demonstrated that protein expression of NCOA3 was significantly upregulated in thyroid cancer tissues. NCOA3 knockdown inhibited cell proliferation and invasion, and induced cell cycle arrest and apoptosis in thyroid cancer. Conversely, ectopic expression of NCOA3 promoted cell proliferation and invasiveness in thyroid cancer. Mechanistically, NCOA3 could improve the survival and invasiveness of thyroid cancer cells through the modulation of the ErbB, AKT, ERK, and β-catenin pathways.

CONCLUSION

Collectively, these findings suggest that NCOA3 is critical in the initiation and development of thyroid cancer, and might be a possible marker for prognosis and therapy.

PXR Functionally Interacts with NF-κB and AP-1 to Downregulate the Inflammation-Induced Expression of Chemokine CXCL2 in Mice

Pregnane X receptor (PXR) is a liver-enriched xenobiotic-responsive transcription factor. Although recent studies suggest that PXR shows anti-inflammatory effects by suppressing nuclear factor kappa B (NF-κB), the detailed mechanism remains unclear. In this study, we aimed to elucidate this mechanism. Mice were treated intraperitoneally with the PXR agonist pregnenolone 16α-carbonitrile (PCN) and/or carbon tetrachloride (CCl₄). Liver injury was evaluated, and hepatic mRNA levels were determined via quantitative reverse transcription polymerase chain reaction. Reporter assays with wild-type and mutated mouse Cxcl2 promoter-containing reporter plasmids were conducted in 293T cells. Results showed that the hepatic expression of inflammation-related genes was upregulated in CCl₄-treated mice, and PCN treatment repressed the induced expression of chemokine-encoding Ccl2 and Cxcl2 among the genes investigated. Consistently, PCN treatment suppressed the increased plasma transaminase activity and neutrophil infiltration in the liver. In reporter assays, tumor necrosis factor-α-induced Cxcl2 expression was suppressed by PXR. Although an NF-κB inhibitor or the mutation of an NF-κB-binding motif partly reduced PXR-dependent suppression, the mutation of both NF-κB and activator protein 1 (AP-1) sites abolished it. Consistently, AP-1-dependent gene transcription was suppressed by PXR with a construct containing AP-1 binding motifs. In conclusion, the present results suggest that PXR exerts anti-inflammatory effects by suppressing both NF-κB- and AP-1-dependent chemokine expression in mouse liver.

SRC1 Deficiency in Hypothalamic Arcuate Nucleus Increases Appetite and Body Weight

Appetite is tightly controlled by neural and hormonal signals in animals. In general, steroid receptor co-activator 1 (SRC1) enhances steroid hormone signalling in energy balance and serves as a common co-activator of several steroid receptors, such as estrogen and glucocorticoid receptors. However, the key roles of SRC1 in energy balance remain largely unknown. We first confirmed that SRC1 is abundantly expressed in the hypothalamic arcuate nucleus (ARC), which is a critical centre for regulating feeding and energy balance; it is further co-localised with agouti-related protein and proopiomelanocortin neurons in the arcuate nucleus. Interestingly, local SRC1 expression changes with the transition between sufficiency and deficiency of food supply. To identify its direct role in appetite regulation, we repressed SRC1 expression in the hypothalamic ARC using lentivirus shRNA and found that SRC1 deficiency significantly promoted food intake and body weight gain, particularly in mice fed with a high-fat diet. We also found the activation of the AMP-activated protein kinase (AMPK) signalling pathway due to SRC1 deficiency. Thus, our results suggest that SRC1 in the ARC regulates appetite and body weight and that AMPK signalling is involved in this process. We believe that our study results have important implications for recognising the overlapping and integrating effects of several steroid hormones/receptors on accurate appetite regulation in future studies.

Network analysis of SRC-1 reveals a novel transcription factor hub which regulates endocrine resistant breast cancer

Steroid receptor coactivator 1 (SRC-1) interacts with nuclear receptors and other transcription factors (TFs) to initiate transcriptional networks and regulate downstream genes which enable the cancer cell to evade therapy and metastasise. Here we took a top-down discovery approach to map out the SRC-1 transcriptional network in endocrine resistant breast cancer. First, rapid immunoprecipitation mass spectrometry of endogenous proteins (RIME) was employed to uncover new SRC-1 TF partners. Next, RNA sequencing (RNAseq) was undertaken to investigate SRC-1 TF target genes. Molecular and patient-derived xenograft studies confirmed STAT1 as a new SRC-1 TF partner, important in the regulation of a cadre of four SRC-1 transcription targets, NFIA, SMAD2, E2F7 and ASCL1. Extended network analysis identified a downstream 79 gene network, the clinical relevance of which was investigated in RNAseq studies from matched primary and local-recurrence tumours from endocrine resistant patients. We propose that SRC-1 can partner with STAT1 independently of the estrogen receptor to initiate a transcriptional cascade and control regulation of key endocrine resistant genes.

Role of Stro1+/CD44+ stem cells in myometrial physiology and uterine remodeling during pregnancy

Regulation of myometrial functions during pregnancy has been considered the result of the integration of endocrine and mechanical signals. Nevertheless, uterine regeneration is poorly understood, and the cellular source within the gravid uterus is largely unexplored.In this study, we isolated and quantified the myometrial stem cells (MSC) population from pregnant female Eker rat uteri, by using Stro1/CD44 surface markers. We demonstrated that prior parity significantly increased the percentage of Stro1+/CD44+ MSC because of injured tissue response. Interestingly, we established that Stro1+/CD44+ MSC respond efficiently to physiological cues when they were treated in vitro under different dose-dependent pregnant rat serum.Previous studies reveal strong regulatory links between O2 availability and stem cell function. Based on these premises, cell proliferation assays showed that isolated Stro1+/CD44+ MSC possess a higher proliferative rate under hypoxic versus normoxic conditions. We also detected a total of 37 upregulated and 44 downregulated hypoxia-related genes, which were differentially expressed in Stro1+/CD44+ MSC, providing an alternative approach to infer into complex molecular mechanisms such as energy metabolism, inflammatory response, uterine expansion, and/or remodeling.Since these cells preferentially grow under low oxygen conditions, we propose that the increase of the rat uterus during pregnancy involves myometrial oxygen consumption, thereby enhancing MSC proliferation. Moreover, pregnancy-induced mechanical stretching results in hypoxic conditions, ultimately creating an environment that promotes stem cell proliferation and further uterine enlargement, which is essential for a successful pregnancy. In summary, all of these data support that rat Stro1+/CD44+ MSC contribute to uterine enlargement during pregnancy.

The role of mitogen-activated protein kinases and sterol receptor coactivator-1 in TGF-β-regulated expression of genes implicated in macrophage cholesterol uptake

The anti-atherogenic cytokine TGF-β inhibits macrophage foam cell formation by suppressing the expression of key genes implicated in the uptake of modified lipoproteins. We have previously shown a critical role for p38 MAPK and JNK in the TGF-β-mediated regulation of apolipoprotein E expression in human monocytes. However, the roles of these two MAPK pathways in the control of expression of key genes involved in the uptake of modified lipoproteins in human macrophages is poorly understood and formed the focus of this study. TGF-β activated both p38 MAPK and JNK, and knockdown of p38 MAPK or c-Jun, a key downstream target of JNK action, demonstrated their requirement in the TGF-β-inhibited expression of several key genes implicated in macrophage lipoprotein uptake. The potential role of c-Jun and specific co-activators in the action of TGF-β was investigated further by studies on the lipoprotein lipase gene. c-Jun did not directly interact with the minimal promoter region containing the TGF-β response elements and a combination of transient transfection and knock down assays revealed an important role for SRC-1. These studies provide novel insights into the mechanisms underlying the TGF-β-mediated inhibition of macrophage gene expression associated with the control of cholesterol homeostasis.

NCOA1 promotes angiogenesis in breast tumors by simultaneously enhancing both HIF1α- and AP-1-mediated VEGFa transcription

Nuclear receptor coactivator 1 (NCOA1) is overexpressed in a subset of breast cancer and its increased expression positively correlates with disease recurrence and metastasis. Although NCOA1 is known to promote breast cancer metastasis through working with multiple transcription factors to upregulate the expression of Twist1, ITGA5, CSF-1, SDF1 and CXCR4, the role of NCOA1 in breast tumor angiogenesis has not been investigated. In this study, we found that the microvascular density (MVD) was significantly decreased and increased in Ncoa1-knockout and NCOA1-overexpressing mammary tumors, respectively, in several breast cancer mouse models. Knockout or knockdown of NCOA1 in breast cancer cell lines also markedly compromised their capability to induce angiogenesis in Matrigel plugs embedded subcutaneously in mice, while this compromised capability could be rescued by VEGFa treatment. At the molecular level, NCOA1 upregulates VEGFa expression in both mouse mammary tumors and cultured breast cancer cells, and it does so by associating with both c-Fos, which is recruited to the AP-1 site at bp −938 of the VEGFa promoter, and HIF1α, which is recruited to the HIF1α-binding element at bp −979 of the VEGFa promoter, to enhance VEGFa transcription. In 140 human breast tumors, high NCOA1 protein correlates with high MVD and patients with both high NCOA1 and high MVD showed significantly shorter survival time. In summary, this study revealed a novel mechanism that NCOA1 potentiates breast cancer angiogenesis through upregulating HIF1α and AP-1-mediated VEGFa expression, which reinforces the rational of targeting NCOA1 in controlling breast cancer progression and metastasis.

Circadian Clock Regulates Bone Resorption in Mice

The circadian clock controls many behavioral and physiological processes beyond daily rhythms. Circadian dysfunction increases the risk of cancer, obesity, and cardiovascular and metabolic diseases. Although clinical studies have shown that bone resorption is controlled by circadian rhythm, as indicated by diurnal variations in bone resorption, the molecular mechanism of circadian clock-dependent bone resorption remains unknown. To clarify the role of circadian rhythm in bone resorption, aryl hydrocarbon receptor nuclear translocator-like (Bmal1), a prototype circadian gene, was knocked out specifically in osteoclasts. Osteoclast-specific Bmal1-knockout mice showed a high bone mass phenotype due to reduced osteoclast differentiation. A cell-based assay revealed that BMAL1 upregulated nuclear factor of activated T cells, cytoplasmic, calcineurin-dependent 1 (Nfatc1) transcription through its binding to an E-box element located on the Nfatc1 promoter in cooperation with circadian locomotor output cycles kaput (CLOCK), a heterodimer partner of BMAL1. Moreover, steroid receptor coactivator (SRC) family members were shown to interact with and upregulate BMAL1:CLOCK transcriptional activity. Collectively, these data suggest that bone resorption is controlled by osteoclastic BMAL1 through interactions with the SRC family and binding to the Nfatc1 promoter. © 2016 American Society for Bone and Mineral Research.

Tead and AP1 Coordinate Transcription and Motility

The Tead family transcription factors are the major intracellular mediators of the Hippo-Yap pathway. Despite the importance of Hippo signaling in tumorigenesis, Tead-dependent downstream oncogenic programs and target genes in cancer cells remain poorly understood. Here, we characterize Tead4-mediated transcriptional networks in a diverse range of cancer cells, including neuroblastoma, colorectal, lung, and endometrial carcinomas. By intersecting genome-wide chromatin occupancy analyses of Tead4, JunD, and Fra1/2, we find that Tead4 cooperates with AP1 transcription factors to coordinate target gene transcription. We find that Tead-AP1 interaction is JNK independent but engages the SRC1-3 co-activators to promote downstream transcription. Furthermore, we show that Tead-AP1 cooperation regulates the activity of the Dock-Rac/CDC42 module and drives the expression of a unique core set of target genes, thereby directing cell migration and invasion. Together, our data unveil a critical regulatory mechanism underlying Tead- and AP1-controlled transcriptional and functional outputs in cancer cells.

Moving Beyond the Androgen Receptor (AR): Targeting AR-Interacting Proteins to Treat Prostate Cancer

Medical or surgical castration serves as the backbone of systemic therapy for advanced and metastatic prostate cancer, taking advantage of the importance of androgen signaling in this disease. Unfortunately, resistance to castration emerges almost universally. Despite the development and approval of new and more potent androgen synthesis inhibitors and androgen receptor (AR) antagonists, prostate cancers continue to develop resistance to these therapeutics, while often maintaining their dependence on the AR signaling axis. This highlights the need for innovative therapeutic approaches that aim to continue disrupting AR downstream signaling but are orthogonal to directly targeting the AR itself. In this review, we discuss the preclinical research that has been done, as well as clinical trials for prostate cancer, on inhibiting several important families of AR-interacting proteins, including chaperones (such as heat shock protein 90 (HSP90) and FKBP52), pioneer factors (including forkhead box protein A1 (FOXA1) and GATA-2), and AR transcriptional coregulators such as the p160 steroid receptor coactivators (SRCs) SRC-1, SRC-2, SRC-3, as well as lysine deacetylases (KDACs) and lysine acetyltransferases (KATs). Researching the effect of-and developing new therapeutic agents that target-the AR signaling axis is critical to advancing our understanding of prostate cancer biology, to continue to improve treatments for prostate cancer and for overcoming castration resistance.

Estrogen receptor α enhances the transcriptional activity of ETS-1 and promotes the proliferation, migration and invasion of neuroblastoma cell in a ligand dependent manner

BACKGROUND

It is well known that estrogen receptor α (ERα) participates in the pathogenic progress of breast cancer, hepatocellular carcinoma and head and neck squamous cell carcinoma. In neuroblastoma cells and related cancer clinical specimens, moreover, the ectopic expression of ERα has been identified. However, the detailed function of ERα in the proliferation of neuroblastoma cell is yet unclear.

METHODS

The transcriptional activity of ETS-1 (E26 transformation specific sequence 1) was measured by luciferase analysis. Western blot assays and Real-time RT-PCR were used to examine the expression of ERα, ETS-1 and its targeted genes. The protein-protein interaction between ERα and ETS-1 was determined by co-IP and GST-Pull down assays. The accumulation of ETS-1 in nuclear was detected by western blot assays, and the recruitment of ETS-1 to its targeted gene's promoter was tested by ChIP assays. Moreover, SH-SY5Y cells' proliferation, anchor-independent growth, migration and invasion were quantified using the MTT, soft agar or Trans-well assay, respectively.

RESULTS

The transcriptional activity of ETS-1 was significantly increased following estrogen treatment, and this effect was related to ligand-mediated activation of ERα. The interaction between the ERα and ETS-1 was identified, and enhancement of ERα activation would up-regulate the ETS-1 transcription factor activity via modulating its cytoplasm/nucleus translocation and the recruitment of ETS-1 to its target gene's promoter. Furthermore, treatment of estrogen increased proliferation, migration and invasion of neuroblastoma cells, whereas the antagonist of ERα reduced those effects.

CONCLUSIONS

In this study, we provided evidences that activation of ERα promoted neuroblastoma cells proliferation and up-regulated the transcriptional activity of ETS-1. By investigating the role of ERα in the ETS-1 activity regulation, we demonstrated that ERα may be a novel ETS-1 co-activator and thus a potential therapeutic target in human neuroblastoma treatment.

LXXLL peptide converts transportan 10 to a potent inducer of apoptosis in breast cancer cells

Degenerate expression of transcription coregulator proteins is observed in most human cancers. Therefore, in targeted anti-cancer therapy development, intervention at the level of cancer-specific transcription is of high interest. The steroid receptor coactivator-1 (SRC-1) is highly expressed in breast, endometrial, and prostate cancer. It is present in various transcription complexes, including those containing nuclear hormone receptors. We examined the effects of a peptide that contains the LXXLL-motif of the human SRC-1 nuclear receptor box 1 linked to the cell-penetrating transportan 10 (TP10), hereafter referred to as TP10-SRC1_LXXLL, on proliferation and estrogen-mediated transcription of breast cancer cells in vitro. Our data show that TP10-SRC1_LXXLL induced dose-dependent cell death of breast cancer cells, and that this effect was not affected by estrogen receptor (ER) status. Surprisingly TP10-SRC1_LXXLL severely reduced the viability and proliferation of hormone-unresponsive breast cancer MDA-MB-231 cells. In addition, the regulation of the endogenous ERα direct target gene pS2 was not affected by TP10-SRC1_LXXLL in estrogen-stimulated MCF-7 cells. Dermal fibroblasts were similarly affected by treatment with higher concentrations of TP10-SRC1_LXXLL and this effect was significantly delayed. These results suggest that the TP10-SRC1_LXXLL peptide may be an effective drug candidate in the treatment of cancers with minimal therapeutic options, for example ER-negative tumors.

Estrogen receptor β (ERβ1) transactivation is differentially modulated by the transcriptional coregulator Tip60 in a cis-acting element-dependent manner

Estrogen receptor (ER) β1 and ERα have overlapping and distinct functions despite their common use of estradiol as the physiological ligand. These attributes are explained in part by their differential utilization of coregulators and ligands. Although Tip60 has been shown to interact with both receptors, its regulatory role in ERβ1 transactivation has not been defined. In this study, we found that Tip60 enhances transactivation of ERβ1 at the AP-1 site but suppresses its transcriptional activity at the estrogen-response element (ERE) site in an estradiol-independent manner. However, different estrogenic compounds can modify the Tip60 action. The corepressor activity of Tip60 at the ERE site is abolished by diarylpropionitrile, genistein, equol, and bisphenol A, whereas its coactivation at the AP-1 site is augmented by fulvestrant (ICI 182,780). GRIP1 is an important tethering mediator for ERs at the AP-1 site. We found that coexpression of GRIP1 synergizes the action of Tip60. Although Tip60 is a known acetyltransferase, it is unable to acetylate ERβ1, and its coregulatory functions are independent of its acetylation activity. In addition, we showed the co-occupancy of ERβ1 and Tip60 at ERE and AP-1 sites of ERβ1 target genes. Tip60 differentially regulates the endogenous expression of the target genes by modulating the binding of ERβ1 to the cis-regulatory regions. Thus, we have identified Tip60 as the first dual-function coregulator of ERβ1.

Infantile hemangioma-mechanism(s) of drug action on a vascular tumor

Infantile hemangioma (IH), a benign vascular tumor, is the most common tumor of infancy, with an incidence of 5%-10% at the end of the first year. The tumor displays a distinctive life cycle consisting of a proliferating phase, occurring in the first months of life, followed by an involuting phase. Thus, IH represents a unique model of postnatal vasculogenesis, angiogenesis, and vessel regression. Traditionally, corticosteroids were the drug of choice when treatment of IH was indicated. In recent years, beta-blockers, most specifically propranolol, have serendipitously been shown to be an effective pharmacological treatment. This article will focus on the mechanism of action of these two drugs, the old and the new treatments, in slowing the growth and accelerating involution of IH.

SRC-3 coactivator regulates cell resistance to cytotoxic stress via TRAF4-mediated p53 destabilization

Steroid receptor coactivator 3 (SRC-3) is an oncogenic nuclear receptor coactivator that plays a significant role in drug resistance. Using a lentiviral cDNA library rescue screening approach, we identified a SRC-3 downstream gene-TRAF4 (tumor necrosis factor [TNF] receptor associated-factor 4)-that functions in cell resistance to cytotoxic stress. TRAF4 expression is positively correlated with SRC-3 expression in human breast cancers. Similar to that observed for SRC-3 overexpression, breast cancer cells overexpressing TRAF4 are more resistant to stress-induced death. Here, we further dissected the underlying molecular mechanism for SRC-3 and TRAF4-mediated resistance to cytotoxic agents. We observed that SRC-3 expression is inversely correlated with the expression of p53-regulated proapoptotic genes in breast cancers and further found that SRC-3 and TRAF4 overexpression diminished cytotoxic stress-induced up-regulation of the tumor suppressor p53 protein. To determine the mechanism, we showed that the TRAF domain of TRAF4 bound to the N-terminal TRAF-like region of the deubiquitinase HAUSP (herpesvirus-associated ubiquitin-specific protease; also named USP7) and blocked the access of p53 to the same region of HAUSP. This TRAF4-mediated inhibition of HAUSP then led to the loss of p53 deubiquitination and its stabilization in response to cellular stress. Consistent with this cellular function, we also found that TRAF4 overexpression in breast cancer patients was associated significantly with poor prognosis. Because of SRC-3's ability to abrogate p53 function, our results suggest that SRC-3 overexpression may be especially important in tumors in which p53 is not mutated.

AIB1 predicts bladder cancer outcome and promotes bladder cancer cell proliferation through AKT and E2F1

Background:

We previously demonstrated that AIB1 overexpression is an independent molecular marker for shortened survival of bladder cancer (BC) patients. In this study, we characterised the role and molecular mechanisms of AIB1 in BC tumorigenicity.

Methods:

AIB1 expression was measured by immunohistochemistry in non-muscle-invasive BC tissue and adjacent normal bladder tissue. In addition, the tumorigenicity of AIB1 was assessed with in vitro and in vivo functional assays.

Results:

Overexpression of AIB1 was observed in tissues from 46 out of 146 patients with non-muscle-invasive BC and was an independent predictor for poor progression-free survival. Lentivirus-mediated AIB1 knockdown inhibited cell proliferation both in vitro and in vivo, whereas AIB1 overexpression promoted cell proliferation in vitro. The growth-inhibitory effect induced by AIB1 knockdown was mediated by G1 arrest, which was caused by reduced expression of key cell-cycle regulatory proteins through the AKT pathway and E2F1.

Conclusion:

Our results suggest that AIB1 promotes BC cell proliferation through the AKT pathway and E2F1. Furthermore, AIB1 overexpression predicts tumour progression in patients with non-muscle-invasive BC.

Chromosome 2p gain in monoclonal B-cell lymphocytosis and in early stage chronic lymphocytic leukemia

Recent studies have described chromosome 2p gain as a recurrent lesion in chronic lymphocytic leukemia (CLL). We investigated the 2p gain and its relationship with common prognostic biomarkers in a prospective series of 69 clinical monoclonal B-cell lymphocytosis (cMBL) and 218 early stage (Binet A) CLL patients. The 2p gain was detected by FISH in 17 patients (6%, 16 CLL, and 1 cMBL) and further characterized by single nucleotide polymorphism-array. Overall, unfavorable cytogenetic deletions, i.e., del(11)(q23) and del(17)(p13) (P = 0.002), were significantly more frequent in 2p gain cases, as well as unmutated status of IGHV (P < 1 × 10(-4) ) and CD38 (P < 1 × 10(-4) ) and ZAP-70 positive expression (P = 0.003). Furthermore, 2p gain patients had significantly higher utilization of stereotyped B-cell receptors compared with 2p negative patients (P = 0.009), and the incidence of stereotyped subset #1 in 2p gain patients was significantly higher than that found in the remaining CLLs (P = 0.031). Transcriptional profiling analysis identified several genes significantly upregulated in 2p gain CLLs, most of which mapped to 2p. Among these, NCOA1 and ROCK2 are known for their involvement in tumor progression in several human cancers, whereas among those located in different chromosomes, CAV1 at 7q31.1 has been recently identified to play a critical role in CLL progression. Thus, 2p gain can be present since the early stages of the disease, particularly in those cases characterized by other poor prognosis markers. The finding of genes upregulated in the cells with 2p gain provides new insights to define the pathogenic role of this lesion.

9-Cis-retinoic acid induces growth inhibition in retinoid-sensitive breast cancer and sea urchin embryonic cells via retinoid X receptor α and replication factor C3

There is widespread interest in defining factors and mechanisms that suppress the proliferation of cancer cells. Retinoic acid (RA) is a potent suppressor of mammary cancer and developmental embryonic cell proliferation. However, the molecular mechanisms by which 9-cis-RA signaling induces growth inhibition in RA-sensitive breast cancer and embryonic cells are not apparent. Here, we provide evidence that the inhibitory effect of 9-cis-RA on cell proliferation depends on 9-cis-RA-dependent interaction of retinoid X receptor α (RXRα) with replication factor C3 (RFC3), which is a subunit of the RFC heteropentamer that opens and closes the circular proliferating cell nuclear antigen (PCNA) clamp on DNA. An RFC3 ortholog in a sea urchin cDNA library was isolated by using the ligand-binding domain of RXRα as bait in a yeast two-hybrid screening. The interaction of RFC3 with RXRα depends on 9-cis-RA and bexarotene, but not on all-trans-RA or an RA receptor (RAR)-selective ligand. Truncation and mutagenesis experiments demonstrated that the C-terminal LXXLL motifs in both human and sea urchin RFC3 are critical for the interaction with RXRα. The transient interaction between 9-cis-RA-activated RXRα and RFC3 resulted in reconfiguration of the PCNA-RFC complex. Furthermore, we found that knockdown of RXRα or overexpression of RFC3 impairs the ability of 9-cis-RA to inhibit proliferation of MCF-7 breast cancer cells and sea urchin embryogenesis. Our results indicate that 9-cis-RA-activated RXRα suppresses the growth of RA-sensitive breast cancer and embryonic cells through RFC3.

The function of steroid receptor coactivator-1 in normal tissues and cancer

In 1995, the steroid receptor coactivator-1 (SRC-1) was identified as the first authentic steroid receptor coactivator. Since then, the SRC proteins have remained at the epicenter of coregulator biology, molecular endocrinology and endocrine-related cancer. Cumulative works on SRC-1 have shown that it is primarily a nuclear receptor coregulator and functions to construct highly specific enzymatic protein complexes which can execute efficient and successful transcriptional activation of designated target genes. The versatile nature of SRC-1 enables it to respond to steroid dependent and steroid independent stimulation, allowing it to bind across many families of transcription factors to orchestrate and regulate complex physiological reactions. This review highlights the multiple functions of SRC-1 in the development and maintenance of normal tissue functions as well as its major role in mediating hormone receptor responsiveness. Insights from genetically manipulated mouse models and clinical data suggest SRC-1 is significantly overexpressed in many cancers, in particular, cancers of the reproductive tissues. SRC-1 has been associated with cellular proliferation and tumor growth but its major tumorigenic contributions are promotion and execution of breast cancer metastasis and mediation of resistance to endocrine therapies. The ability of SRC-1 to coordinate multiple signaling pathways makes it an important player in tumor cells' escape of targeted therapy.

The nuclear cofactor RAC3/AIB1/SRC-3 enhances Nrf2 signaling by interacting with transactivation domains

Nuclear factor erythroid 2-related factor 2 (Nrf2, NM 006164, 605 AA) is essential for the antioxidant responsive element (ARE)-mediated expression of a group of detoxifying antioxidant genes that detoxify carcinogens and protect against oxidative stress. Several proteins have been identified as Nrf2-interacting molecules. In this study, we found that the overexpression of receptor-associated coactivator 3 (RAC3)/AIB-1/steroid receptor coactivator-3, a nuclear coregulator and oncogene frequently amplified in human breast cancers, induced heme oxygenase-1 (HO-1) through Nrf2 transactivation in HeLa cells. Next, we determined the interaction between RAC3 and Nrf2 proteins using a co-immunoprecipitation assay and fluorescence resonance energy transfer analysis. The results showed that RAC3 bound directly to the Nrf2 protein in the nucleus. Subsequently, we identified the interacting domains of Nrf2 and RAC3 using a glutathione S-transferase pull-down assay. The results showed that both the N-terminal RAC3-pasB and C-terminal RAC3-R3B3 domains were tightly bound to the Neh4 and Neh5 transactivation domains. Furthermore, chromatin immunoprecipitation showed that RAC3 bound tightly to the ARE enhancer region of the HO-1 promoter via Nrf2 binding. These data suggest that Nrf2 activation is modulated and directly controlled through interactions with the RAC3 protein in HeLa cells.

Tumor-suppressor role for the SPOP ubiquitin ligase in signal-dependent proteolysis of the oncogenic co-activator SRC-3/AIB1

Steroid receptor co-activator-3 (SRC-3/AIB1) is an oncogene that is amplified and overexpressed in many human cancers. However, the molecular mechanisms that regulate 'activated SRC-3 oncoprotein' turnover during tumorigenesis remain to be elucidated. Here, we report that speckle-type POZ protein (SPOP), a cullin 3 (CUL3)-based ubiquitin ligase, is responsible for SRC-3 ubiquitination and proteolysis. SPOP interacts directly with an SRC-3 phospho-degron in a phosphorylation-dependent manner. Casein kinase Iɛ phosphorylates the S102 in this degron and promotes SPOP-dependent turnover of SRC-3. Short hairpin RNA knockdown and overexpression experiments substantiated that the SPOP/CUL3/Rbx1 ubiquitin ligase complex promotes SRC-3 turnover. A systematic analysis of the SPOP genomic locus revealed that a high percentage of genomic loss or loss of heterozygosity occurs at this locus in breast cancers. Furthermore, we demonstrate that restoration of SPOP expression inhibited SRC-3-mediated oncogenic signaling and tumorigenesis, thus positioning SPOP as a tumor suppressor.

The p160 ER co-regulators predict outcome in ER negative breast cancer

The SRC family of ER co-regulators are frequently overexpressed in breast cancer. Overexpression of AIB1 appears to be linked to hormone resistance in HER2 positive breast cancer. However, the role of these co-regulators in ER negative disease is poorly understood. SRC1, SRC2 and AIB1 expression was determined by immunohistochemical analysis of tissue microarrays constructed from tumours within the Edinburgh Breast Conservation Series (BCS). The BCS represents a fully documented consecutive cohort of 1,812 patients treated by breast conservation surgery in a single institution. Our results demonstrate tumours that overexpress both HER2 and AIB1 were associated with markedly reduced relapse free, distant relapse free and overall survival compared to HER2 and AIB1 only overexpressing tumours irrespective of ER status. In ER negative disease both SRC1 and AIB1 were linked to early relapse and death. The SRC family of ER co-regulators is involved in early relapse and resistance in both ER negative and ER positive breast cancer challenging the conventional concept that this effect is mediated solely via the ER.

Steroid receptor coactivator-1 upregulates integrin α₅ expression to promote breast cancer cell adhesion and migration

Metastatic breast cancer remains a lethal disease with poorly understood molecular mechanisms. Steroid receptor coactivator-1 (SRC-1 or NCOA1) is overexpressed in a subset of breast cancers with poor prognosis. It potentiates gene expression by serving as a coactivator for nuclear receptors and other transcription factors. We previously reported that SRC-1 promotes breast cancer metastasis without affecting primary mammary tumor formation. Herein, we found that SRC-1 deficiency in mouse and human breast cancer cells substantially reduced cell adhesion and migration capabilities on fibronectin and significantly extended the time of focal adhesion disassembly and reassembly. In agreement with this phenotype, SRC-1 expression positively correlated with integrin α(5) (ITGA5) expression in estrogen receptor-negative breast tumors whereas SRC-1 deficiency decreased ITGA5 expression. Furthermore, ITGA5 reduction in SRC-1-deficient/insufficient breast cancer cells or knockdown of ITGA5 in SRC-1-expressing breast cancer cells was associated with a disturbed integrin-mediated signaling. Critical downstream changes included reduced phosphorylation and/or dampened activation of focal adhesion kinase, paxillin, Rac1, and Erk1/2 during cell adhesion. Finally, we found that SRC-1 enhanced ITGA5 promoter activity through an AP-1 (activator protein)-binding site proximal to the transcriptional initiation site; both SRC-1 and c-Jun were recruited to this promoter region in breast cancer cells. These results show that SRC-1 can promote breast cancer metastasis by directly enhancing ITGA5 expression and thus promoting ITGA5-mediated cell adhesion and migration. Therefore, targeting ITGA5 in SRC-1-positive breast cancers may result in inhibition of SRC-1-promoted breast cancer metastasis.

Altered AIB1 or AIB1Δ3 expression impacts ERα effects on mammary gland stromal and epithelial content

Amplified in breast cancer 1 (AIB1) (also known as steroid receptor coactivator-3) is a nuclear receptor coactivator enhancing estrogen receptor (ER)α and progesterone receptor (PR)-dependent transcription in breast cancer. The splice variant AIB1Δ3 demonstrates increased ability to promote ERα and PR-dependent transcription. Both are implicated in breast cancer risk and antihormone resistance. Conditional transgenic mice tested the in vivo impact of AIB1Δ3 overexpression compared with AIB1 on histological features of increased breast cancer risk and growth response to estrogen and progesterone in the mammary gland. Combining expression of either AIB1 or AIB1Δ3 with ERα overexpression, we investigated in vivo cooperativity. AIB1 and AIB1Δ3 overexpression equivalently increased the prevalence of hyperplastic alveolar nodules but not ductal hyperplasia or collagen content. When AIB1 or AIB1Δ3 overexpression was combined with ERα, both stromal collagen content and ductal hyperplasia prevalence were significantly increased and adenocarcinomas appeared. Overexpression of AIB1Δ3, especially combined with overexpressed ERα, led to an abnormal response to estrogen and progesterone with significant increases in stromal collagen content and development of a multilayered mammary epithelium. AIB1Δ3 overexpression was associated with a significant increase in PR expression and PR downstream signaling genes. AIB1 overexpression produced less marked growth abnormalities and no significant change in PR expression. In summary, AIB1Δ3 overexpression was more potent than AIB1 overexpression in increasing stromal collagen content, inducing abnormal mammary epithelial growth, altering PR expression levels, and mediating the response to estrogen and progesterone. Combining ERα overexpression with either AIB1 or AIB1Δ3 overexpression augmented abnormal growth responses in both epithelial and stromal compartments.

Transcription factor effector domains

The last decade has seen an incredible breakthrough in technologies that allow histones, transcription factors (TFs), and RNA polymerases to be precisely mapped throughout the genome. From this research, it is clear that there is a complex interaction between the chromatin landscape and the general transcriptional machinery and that the dynamic control of this interface is central to gene regulation. However, the chromatin remodeling enzymes and general TFs cannot, on their own, recognize and stably bind to promoter or enhancer regions. Rather, they are recruited to cis regulatory regions through interaction with site-specific DNA binding TFs and/or proteins that recognize epigenetic marks such as methylated cytosines or specifically modified amino acids in histones. These "recruitment" factors are modular in structure, reflecting their ability to interact with the genome via one region of the protein and to simultaneously bind to other regulatory proteins via "effector" domains. In this chapter, we provide examples of common effector domains that can function in transcriptional regulation via their ability to (a) interact with the basal transcriptional machinery and general co-activators, (b) interact with other TFs to allow cooperative binding, and (c) directly or indirectly recruit histone and chromatin modifying enzymes.

[Effects of gambogic acid on the regulation of steroid receptor coactivator-3 in A549 cells]

OBJECTIVE

To investigate the effects of gambogic acid (GA) on the proliferation inhibition and apoptosis induction in Human lung adenocarcinoma A549 cells in vitro, as well as the regulation of steroid receptor coactivator-3 (SRC-3) to explore the relationship between them.

METHODS

The effect of GA on the growth of A549 cells was studied by MTT assay. Apoptosis was detected by Hoechst 33258 staining. The localization of SRC-3 was determined by confocal laser scanning microscopy. Western blot and RT-PCR technique were applied to assess the expression of SRC-3.

RESULTS

GA presented a striking proliferation inhibition potency on A549 cells in vitro, as well as apoptosis induction activity in a time- and dose-dependent manner. The IC(50) value for 24 h was (3.17 +/- 0.13) micromol/L. Overexpression of SRC-3 was found in A549 cells, whereas the SRC-3 protein and mRNA expression levels were significantly downregulated in A549 cells induced by GA in a dose-dependent manner. The location of SRC-3 was situated mainly in the cell nuclei.

CONCLUSION

GA exhibits a potent proliferation inhibition and apoptosis induction in human lung adenocarcinoma A549 cells, which might correspond to the downregulation of the expression of SRC-3. Thus, it promises to be a new target drug for lung cancer treatment.

Targeting NF-κB in infantile hemangioma-derived stem cells reduces VEGF-A expression

BACKGROUND

infantile hemangioma (IH) is a most common tumor of infancy. Using infantile hemangioma-derived stem cells (HemSCs), we recently demonstrated that corticosteroids suppress the expression of VEGF-A, monocyte chemoattractant protein-1 (MCP-1), urokinase plasminogen activator receptor (uPAR), and interleukin-6 (IL-6); each of these are known targets of the transcription factor nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB). In the present study, we examined the expression of these NF-κB target genes in IH tissue specimens and the effect of NF-κB regulation on the expression of pro-angiogenic cytokines, and in particular VEGF-A, in HemSCs.

MATERIALS AND METHODS

RNA extracted from IH tissue and hemangioma-derived stem cells (HemSCs) was used to analyze NF-κB target gene expression by reverse transcription-quantitative PCR (RT-qPCR). The effects of NF-κB blockade were examined in HemSCs. Immunostaining, immunoblotting and ELISA were used to assess protein expression.

RESULTS

MCP-1, uPAR, and IL-6 were found to be differentially expressed in proliferating versus involuting IH. Corticosteroids suppressed NF-κB activity of HemSCs. Velcade (Bortezomib), a proteosome inhibitor that can indirectly inhibit NF-κB, impaired HemSCs viability and expression of pro-angiogenic factors. Furthermore, specific inhibition of NF-κB resulted in suppression of VEGF-A.

CONCLUSIONS

we demonstrate expression of NF-κB target genes in proliferating IH. In addition, we show that the expression of several pro-angiogenic factors in HemSCs, and in particular VEGF-A, is regulated by NF-B activity.

The cooperative function of nuclear receptor coactivator 1 (NCOA1) and NCOA3 in placental development and embryo survival

Nuclear receptor coactivator 1 [NCOA1/steroid receptor coactivator (SRC)-1] and NCOA3 (SRC-3/AIB1/ACTR) constitute two thirds of the SRC (steroid receptor coactivator) family. Although in vitro experiments have suggested overlapping functions between NCOA1 and NCOA3, their in vivo functional relationship is poorly understood. In this study, NCOA1 and NCOA3 double knockout mice were generated to determine the compensatory roles of NCOA1 and NCOA3 in development. NCOA1(-/-) mice survived normally, whereas most NCOA3(-/-) embryos were viable at embryonic d 13.5 (E13.5). In contrast, the majority of double-knockout (DKO) embryos died by E13.5. NCOA1 and NCOA3 are expressed in the labyrinth, and labyrinths of NCOA1(+/-);NCOA3(-/-) and DKO placentas were small compared with wild-type and single-knockout labyrinths. DKO labyrinths exhibited low densities of maternal blood sinuses and fetal capillaries and displayed fetomaternal blood transfusion. At the interface between maternal and fetal circulations, layer I sinusoidal trophoblast giant cells showed a reduced density of microvilli. Layer III syncytiotrophoblasts appeared to accumulate large lipid droplets and have reduced density and deepened invaginations of the intrasyncytial bays. The endothelial layer in DKO labyrinth showed abnormal morphologies and had large lipid droplets. Furthermore, disruption of NCOA1 and NCOA3 increased labyrinth trophoblast proliferation and their progenitor gene expression but decreased their differentiation gene expression. NCOA1 and NCOA3 deficiencies also affected the expression of several genes for placental morphogenesis including TGFβ-, peroxisome proliferator-activated receptor-β-, and peroxisome proliferator-activated receptor-γ-regulated genes and for glucose transportation including GLUT1 and Cx26. These findings demonstrate that NCOA1 and NCOA3 cooperatively regulate placental morphogenesis and embryo survival.

Minireview: Not picking pockets: nuclear receptor alternate-site modulators (NRAMs)

Because of their central importance in gene regulation and mediating the actions of many hormones, the nuclear receptors (NRs) have long been recognized as very important biological and pharmaceutical targets. Of all the surfaces available on a given NR, the singular site for regulation of receptor activity has almost invariably been the ligand-binding pocket of the receptor, the site where agonists, antagonists, and selective NR modulators interact. With our increasing understanding of the multiple molecular components involved in NR action, researchers have recently begun to look to additional interaction sites on NRs for regulating their activities by novel mechanisms. The alternate NR-associated interaction sites that have been targeted include the coactivator-binding groove and allosteric sites in the ligand-binding domain, the zinc fingers of the DNA-binding domain, and the NR response element in DNA. The studies thus far have been performed with the estrogen receptors, the androgen receptor (AR), the thyroid hormone receptors, and the pregnane X receptor. Phenotypic and conformation-based screens have also identified small molecule modulators that are believed to function through the NRs but have, as yet, unknown sites and mechanisms of action. The rewards from investigation of these NR alternate-site modulators should be the discovery of new therapeutic approaches and novel agents for regulating the activities of these important NR proteins.

Normal and cancer-related functions of the p160 steroid receptor co-activator (SRC) family

The three homologous members of the p160 SRC family (SRC1, SRC2 and SRC3) mediate the transcriptional functions of nuclear receptors and other transcription factors, and are the most studied of all the transcriptional co-activators. Recent work has indicated that the SRCgenes are subject to amplification and overexpression in various human cancers. Some of the molecular mechanisms responsible for SRC overexpression, along with the mechanisms by which SRCs promote breast and prostate cancer cell proliferation and survival, have been identified, as have the specific contributions of individual SRC family members to spontaneous breast and prostate carcinogenesis in genetically manipulated mouse models. These studies have identified new challenges for cancer research and therapy.

Determinants of the NF-kappaB response to acute psychosocial stress in humans

Previous research has shown that psychosocial stress is associated with an increased activity of the transcription factor nuclear factor-kappaB (NF-kappaB), a major inducer of inflammatory genes. While considerable individual variation has been noted, factors contributing to this variation have not been described so far. Therefore, 29 healthy participants (35.8+/-12 yrs) were exposed to the Trier Social Stress Test. Blood was collected before and repeatedly afterward for determination of NF-kappaB activity, leukocyte subset numbers, cortisol, norepinephrine, and in vitro-stimulated IL-6 production. Additionally, age, sex, and ratings of perceived chronic and acute stress were assessed. Regression analyses revealed that older participants showed a lower NF-kappaB stress response compared to younger adults (beta= -.42, p=.026). Higher NF-kappaB stress responses were associated with lower cortisol stress responses (beta= -.37, p=.05), higher pre-stress IL-6 production (beta=.38, p=.043), and high chronic in combination with low acute stress, or vice versa (beta= -.61, p=.06). Norepinephrine and sex were not associated with NF-kappaB stress responses (all p.13). In summary, the present study shows for the first time in human psychosocial stress the negative association of cortisol and NF-kappaB. This parallels results from in vitro studies. Our finding of lower NF-kappaB stress responses in older age and in people with high chronic and acute stress might be interpreted as an adaptive dampening of NF-kappaB activity. In the absence of longitudinal data, however, this interpretation remains speculative.

Involvement of GADD153 and cardiac ankyrin repeat protein in cardiac ischemia-reperfusion injury

Oxidative stress is critical for causing cardiac injuries during ischemia-reperfusion (IR), yet the molecular mechanism for this remains unclear. In the present study, we observe that hypoxia and reoxygenation, a component of ischemia, effectively induces apoptosis in the cardiac myocytes from neonatal rats and it concomitantly leads to induction of GADD153, an apoptosis-related gene. Furthermore, IR injury of rat heart showed a GADD153 overexpression in the ischemic area where the TUNEL reaction was positive. A downregulation of cardiac ankyrin repeat protein (CARP) was also observed in this ischemic area. Promoter deletion and reporter analysis revealed that hypoxia transcriptionally activates a GADD153 promoter through the AP-1 element in neonatal cardiomyocytes. Ectopic overexpression of GADD153 resulted in the downregulation of CARP expression. Accordingly, the induction of GADD153 mRNA were followed by the CARP down-regulation in an in vivo rat coronary ischemia/reperfusion injury model. These results suggest that GADD153 over-expression and the resulting downregulation of CARP may have causative roles in apoptotic cell death during cardiac IR injury.

Steroid receptor coactivator-1 is necessary for regulation of corticotropin-releasing hormone by chronic stress and glucocorticoids

Adaptation to stress in vertebrates occurs via activation of hormonal and neuronal signaling cascades in which corticotropin-releasing hormone (CRH) plays a central role. Expression of brain CRH is subject to strong, brain-region specific regulation by glucocorticoid hormones and neurogenic intracellular signals. We hypothesized that Steroid Receptor Coactivator 1 (SRC-1), a transcriptional coregulator of the glucocorticoid receptor, is involved in the sensitivity of CRH regulation by stress-related factors. In the brains of SRC-1 knockout mice we found basal CRH mRNA levels to be lower in the central nucleus of the amygdala. Hypothalamic CRH up-regulation after chronic (but not acute) stress, as well as region-dependent up- and down-regulation induced by synthetic glucocorticoids, were significantly attenuated compared with wild type. The impaired induction of the crh gene by neurogenic signals was corroborated in AtT-20 cells, where siRNA and overexpression experiments showed that SRC-1 is necessary for full induction of a CRH promoter reporter gene by forskolin, suggestive of involvement of transcription factor CREB. In conclusion, SRC-1 is involved in positive and negative regulation of the crh gene, and an important factor for the adaptive capacity of stress.

The steroid receptor coactivator-1 regulates twist expression and promotes breast cancer metastasis

In breast cancer, steroid receptor coactivator-1 (SRC-1) expression positively correlates with HER2 expression and poor prognosis. In mouse mammary tumor virus-polyoma middle T (PyMT) breast cancer mouse model, SRC-1 strongly promotes mammary tumor metastasis. However, the molecular targets and mechanisms that mediate the role of SRC-1 in metastasis are unknown. In this study, SRC-1 wild-type (WT) and knockout (KO) cell lines were developed from the mammary tumors of WT/PyMT and KO/PyMT mice. WT cells exhibited strong migration and invasion capabilities, reduced E-cadherin and beta-catenin epithelial markers, gained N-cadherin and vimentin mesenchymal markers, and formed undifferentiated invasive structures in three-dimensional culture. In contrast, KO cells showed slow migration and invasion, retained E-cadherin, had less N-cadherin and vimentin, and developed partially differentiated three-dimensional structures. Importantly, WT cells expressed Twist, a master regulator of metastasis, at significantly higher levels versus KO cells. SRC-1 knockdown in WT cells reduced Twist expression, whereas SRC-1 restoration in KO cells also rescued Twist expression. Furthermore, SRC-1 was found to coactivate Twist transcription through physical interaction with the transcription factor PEA3 at the proximal Twist promoter. Accordingly, Twist knockdown in WT cells increased E-cadherin and reduced cell invasion and metastasis, and Twist expression in KO cells decreased E-cadherin and increased cell invasion. SRC-1 knockdown in human breast cancer cells also decreased Twist, cell migration, and invasion. Therefore, SRC-1 promotes breast cancer invasiveness and metastasis by coactivating PEA3-mediated Twist expression. Intervention of SRC-1 function may provide new strategies to inhibit breast cancer metastasis.

Expression and significance of androgen receptor coactivators in urothelial carcinoma of the bladder

Urothelial carcinoma (UC) of the bladder is approximately three times more common in men than women. While the etiology for this gender difference in incidence remains unknown, a role for androgen receptor (AR) signaling has been suggested. The mechanisms by which AR activity is regulated in UC cells, however, are largely elusive. Here, we explore the significance of coregulators that are critical for the formation of a functional AR transcriptional complex, in UC cells. Using two AR-positive UC cell lines, TCC-SUP and UMUC3, we demonstrate the expression of the coactivators NCOA1, NCOA2, NCOA3, CREBBP, and EP300 in UC cells. small interfering RNA-mediated knockdown of the AR or any of these coactivators markedly impacted cell viability and abrogated androgen-dependent cell proliferation. Noteworthy, contrary to AR-positive prostate cancer cells, expression of these AR-associated coactivators was not androgen regulated in UC cells. To assess the clinical relevance of coactivator expression, we performed immunohistochemistry on paraffin-embedded sections from 55 patients with UC of the bladder. We found that while 24 out of 55 (44%) of tumors expressed the AR, each of the coactivators was expressed by 85-100% of the bladder cancers. Moreover, we noted a significant downregulation of NCOA1 expression in tumors versus adjacent, non-tumor bladder urothelium, with a mean of 68% (range 0-100) of tumor cells demonstrating NCOA1 staining versus a mean of 81% (range 0-90) of non-tumor cells (P=0.03). Taken together, our data suggest an important role for AR-associated coactivators in UC and point toward differences in the regulation of AR activity between bladder and prostate cancer cells.

Transcriptional activation of human matrix metalloproteinase-9 gene expression by multiple co-activators

Matrix metalloproteinase-9 (MMP-9), a proteolytic enzyme for matrix proteins, chemokines and cytokines, is a major target in cancer and autoimmune diseases, since it is aberrantly upregulated. To control MMP-9 expression in pathological conditions, it is necessary to understand the regulatory mechanisms of MMP-9 expression. MMP-9 gene expression is regulated primarily at the transcriptional level. In this study, we investigated the role of multiple co-activators in regulating MMP-9 transcription. We demonstrate that multiple transcriptional co-activators are involved in MMP-9 promoter activation, including CBP/p300, PCAF, CARM1 and GRIP1. Furthermore, enhancement of MMP-9 promoter activity requires the histone acetyltransferase activity of PCAF but not that of CBP/p300, and the methyltransferase activity of CARM1. More importantly, these co-activators are able to activate MMP-9 promoter activity independently, and function in a synergistic manner. Significant synergy was observed among CARM1, p300 and GRIP1, which is dependent on the interaction of p300 and CARM1 with the AD1 and AD2 domains of GRIP1, respectively. This suggests the formation of a ternary co-activator complex on the MMP-9 promoter. Chromatin immunoprecipitation assays demonstrate that these co-activators associate with the endogenous MMP-9 promoter, and that siRNA knockdown of expression of these co-activators reduces endogenous MMP-9 expression. Taken together, these studies demonstrate a new level of transcriptional regulation of MMP-9 expression by the cooperative action of co-activators.

Steroid receptor coactivator-3/AIB1 promotes cell migration and invasiveness through focal adhesion turnover and matrix metalloproteinase expression

Steroid receptor coactivator-3 (SRC-3)/AIB1 is a member of the p160 nuclear receptor coactivator family involved in development and cell cycle progression. We previously showed that SRC-3/AIB1 is required for prostate cancer cell proliferation and survival. Here, we reported that the elevated SRC-3/AIB1 expression is significantly correlated with human prostate cancer seminal vesicle invasion and lymph node metastasis. Furthermore, SRC-3/AIB1 is associated with increased prostate cancer cell migration and invasion. SRC-3/AIB1 is required for focal adhesion turnover and focal adhesion kinase activation. In addition, SRC-3/AIB1 directly regulates transcription of matrix metalloproteinase (MMP)-2 and MMP-13 through its coactivation of AP-1 and PEA3. Taken together, these data suggest that SRC-3/AIB1 plays an essential role in prostate cancer cell invasion and metastasis.

Restriction to Fos family members of Trip6-dependent coactivation and glucocorticoid receptor-dependent trans-repression of activator protein-1

The term activator protein (AP)-1 describes homodimeric and heterodimeric transcription factors composed of members of the Jun, Fos, and cAMP response element-binding protein (CREB)/activating transcription factor (ATF) families of proteins. Distinct AP-1 dimers, for instance the prototypical c-Jun:c-Fos and c-Jun:ATF2 dimers, are differentially regulated by signaling pathways and bind related yet distinct response elements in the regulatory regions of AP-1 target genes. Little is known about the dimer-specific regulation of AP-1 activity at the promoter of its target genes. We have previously shown that nTrip6, the nuclear isoform of the LIM domain protein Trip6, acts as an AP-1 coactivator. Moreover, nTrip6 is an essential component of glucocorticoid receptor (GR)-mediated trans-repression of AP-1, in that it mediates the tethering of GR to the promoter-bound AP-1. We have now discovered a striking specificity of nTrip6 actions determined by the binding preference of its LIM domains. We show that nTrip6 interacts only with Fos family members. Consequently, nTrip6 is a selective coactivator for AP-1 dimers containing Fos. nTrip6 also assembles activated GR to c-Jun:c-Fos-driven promoters. Neither nTrip6 nor GR are recruited to a promoter occupied by c-Jun:ATF2. Thus, only Fos-containing dimers are trans-repressed by GR. Thus, the dimer composition of AP-1 determines the mechanism of both the positive and negative regulation of AP-1 transcriptional activity. Interestingly, on a second level of action, GR represses the increase in transcriptional activity of c-Jun:ATF2 induced by c-Jun N-terminal kinase (JNK)-dependent phosphorylation. This repression depends on GR-mediated induction of MAPK phosphatase 1 (MKP-1) expression, which results in c-Jun N-terminal kinase inactivation.

Gene regulation system of vasopressin and corticotropin-releasing hormone

The neurohypophyseal hormones, arginine vasopressin and corticotropin-releasing hormone (CRH), play a crucial role in the physiological and behavioral response to various kinds of stresses. Both neuropeptides activate the hypophysial-pituitary-adrenal (HPA) axis, which is a central mediator of the stress response in the body. Conversely, they receive the negative regulation by glucocorticoid, which is an end product of the HPA axis. Vasopressin and CRH are closely linked to immune response; they also interact with pro-inflammatory cytokines. Moreover, as for vasopressin, it has another important role, which is the regulation of water balance through its potent antidiuretic effect. Hence, it is conceivable that vasopressin and CRH mediate the homeostatic responses for survival and protect organisms from the external world.

A tight and elaborate regulation system of the vasopressin and CRH gene is required for the rapid and flexible response to the alteration of the surrounding environments. Several important regulatory elements have been identified in the proximal promoter region in the vasopressin and CRH gene. Many transcription factors and intracellular signaling cascades are involved in the complicated gene regulation system. This review focuses on the current status of the basic research of vasopressin and CRH. In addition to the numerous known facts about their divergent physiological roles, the recent topics of promoter analyses will be discussed.

Proto-oncogene ACTR/AIB1 promotes cancer cell invasion by up-regulating specific matrix metalloproteinase expression

Overexpression of ACTR/AIB1 is frequently found in different cancers with distant metastasis. To address its possible involvement in tumor metastasis, we performed invasion assays to examine the effect of ACTR alteration on the invasiveness of breast cancer cells (MDA-MB-231 or T-47D) and found that high levels of ACTR are required for their strong invasiveness. Molecular analysis indicates that ACTR functions as a coactivator of AP-1 to up-regulate the expression of matrix metalloproteinases such as MMP-7 and MMP-10 and reduce cell adhesion to specific extracellular matrix proteins. These novel findings provide a mechanistic link between ACTR and MMPs, and suggest that ACTR may also play an important role in cancer progression by facilitating tumor invasion.

Determining the transrepression activity of xenoestrogen on nuclear factor-kappa B in Cos-1 cells by estrogen receptor-alpha

Functional assays have been used to define the estrogenicity of xenoestrogens in cotransfection studies employing estrogen receptors in various cell lines. It is known that estrogen is able to affect transcription from other nuclear transcription factors, especially the nuclear factor-kappa B (NF-kappa B). The ability of selected xenoestrogens (methoxychlor [MXC], dieldrin, and o',p'-DDT) to transrepress the NF-kappa B-mediated transcription in Cos-1 cells was evaluated by cotransfection of human estrogen receptor-alpha (hERalpha). These xenoestrogens have been described as comparably potent xenoestrogens, whereas their relative binding activity (RBA) has been relegated to a lower order as compare to estrogen. The two NF-kappa B response element-containing SV40 promoter and -242/+54 cytomegalovirus (CMV)-expressing firefly luciferase (2 x NRE-PV-Luc and 2 x NRE-CMV-Luc, respectively) were transfected into Cos-1 cells with pRL-tk, expressing the renilla luciferase as internal control. The estrogen receptor was expressed from cytomegalovirus major immediate early promoter (CMV-MIEP) (CMV5-hERalpha). Treatment with 1 nM estrogen (E(2)) (26.2%), 5 nM E(2) (41.4%; p < .05), and xenoestrogens (methoxychlor [1 nM: 29.6%, p < .05; 10 nM: 22.6%), dieldrin [1 nM: 10.3%; 10 nM: 36.06%, p < .05], and o',p'-DDT [1 nM: 17.0%; 10 nM: 7.15%]) repressed transcription from 2 x NREX-PV-Luc. The antiestrogen, ICI 182,780, failed to antagonize the effects of xenoestrogens. The effects of xenoestrogens in transrepression of NF-kappa B by ERalpha were similar when 2 x NRE-CMV-Luc was employed as reporter. Statistically significant (p < .01) repression by 1 nM E(2) (69.2%), 5 nM E(2) (69.1%), 1 nM o',p'-DDT (51.4%), 1 nM dieldrin (47.3%), and 1 nM MXC (73.3%) were observed. The effect of these xenoestrogens without ERalpha cotransfection on 2 x NRE-PV-Luc- and 2 x NRE-CMV-Luc-mediated NF-kappa B transcription was not affected by the treatment alone. It is concluded that xenoestrogens, like estrogens, are capable of producing transrepression of NF-kappa B by hERalpha.

Crosstalk between the glucocorticoid receptor and other transcription factors: molecular aspects

Glucocorticoids (GCs) regulate cell fate by altering gene expression via the glucocorticoid receptor (GR). Ligand-bound GR can activate the transcription of genes carrying the specific GR binding sequence, the glucocorticoid response element (GRE). In addition, GR can modulate, positively or negatively, directly or indirectly, the activity of other transcription factors (TFs), a process referred to as "crosstalk". In the indirect crosstalk, GR interferes with transduction pathways upstream of other TFs. In the direct crosstalk, GR and other TFs modulate each other's activity when bound to the promoters of their target genes. The multiplicity of molecular actions exerted by TFs, particularly the GR, is not only fascinating in terms of molecular structure, it also implies that the TFs participate in a wide range of regulatory processes, broader than anticipated. This review focuses on the molecular mechanisms involved in the crosstalk, on both current ideas and unresolved questions, and discusses the possible significance of the crosstalk for the physiologic and therapeutic actions of GCs.

Inhibition of adhesive interaction between multiple myeloma and bone marrow stromal cells by PPARgamma cross talk with NF-kappaB and C/EBP

Binding of multiple myeloma (MM) cells to bone marrow stromal cells (BMSCs) triggers expression of adhesive molecules and secretion of interleukin-6 (IL-6), promoting MM cell growth, survival, drug resistance, and migration, which highlights the possibility of developing and validating novel anti-MM therapeutic strategies targeting MM cells-host BMSC interactions and their sequelae. Recently, we have found that expression of the peroxisome proliferator-activated receptor gamma (PPARgamma) and its ligands can potently inhibit IL-6-regulated MM cell growth. Here we demonstrate that PPARgamma agonists 15-d-PGJ2 and troglitazone significantly suppress cell-cell adhesive events, including expression of adhesion molecules and IL-6 secretion from BMSCs triggered by adhesion of MM cells, as well as overcome drug resistance by a PPARgamma-dependent mechanism. The synthetic and natural PPARgamma agonists have diverging and overlapping mechanisms blocking transactivation of transcription factors NF-kappaB and 5'-CCAAT/enhancer-binding protein beta (C/EBPbeta). Both 15-d-PGJ2 and troglitazone blocked C/EBPbeta transcriptional activity by forming PPARgamma complexes with C/EBPbeta. 15-d-PGJ2 and troglitazone also blocked NF-kappaB activation by recruiting the coactivator PGC-1 from p65/p50 complexes. In addition, 15-d-PGJ2 had a non-PPARgamma-dependent effect by inactivation of phosphorylation of IKK and IkappaB. These studies provide the framework for PPARgamma-based pharmacological strategies targeting adhesive interactions of MM cells with the bone marrow microenvironment.

Steroid receptor coactivator 3 is a coactivator for myocardin, the regulator of smooth muscle transcription and differentiation

Abnormal proliferation of vascular smooth muscle cells (VSMCs) constitutes a key event in atherosclerosis, neointimal hyperplasia, and the response to vascular injury. Estrogen receptor alpha (ERalpha) mediates the protective effects of estrogen in injured blood vessels and regulates ligand-dependent gene expression in vascular cells. However, the molecular mechanisms mediating ERalpha-dependent VSMC gene expression and VSMC proliferation after vascular injury are not well defined. Here, we report that the ER coactivator steroid receptor coactivator 3 (SRC3) is also a coactivator for the major VSMC transcription factor myocardin, which is required for VSMC differentiation to the nonproliferative, contractile state. The N terminus of SRC3, which contains a basic helix-loop-helix/Per-ARNT-Sim protein-protein interaction domain, binds the C-terminal activation domain of myocardin and enhances myocardin-mediated transcriptional activation of VSMC-specific, CArG-containing promoters, including the VSMC-specific genes SM22 and myosin heavy chain. Suppression of endogenous SRC3 expression by specific small interfering RNA attenuates myocardin transcriptional activation in cultured cells. The SRC3-myocardin interaction identifies a site of convergence for nuclear hormone receptor-mediated and VSMC-specific gene regulation and suggests a possible mechanism for the vascular protective effects of estrogen on vascular injury.