Steroid receptor coactivators in Treg and Th17 cell biology and function.

Steroid receptor coactivators (SRCs) are master regulators of transcription that play key roles in human physiology and pathology. SRCs are particularly important for the regulation of the immune system with major roles in lymphocyte fate determination and function, macrophage activity, regulation of nuclear factor κB (NF-κB) transcriptional activity and other immune system biology. The three members of the p160 SRC family comprise a network of immune-regulatory proteins that can function independently or act in synergy with each other, and compensate for - or moderate - the activity of other SRCs. Recent evidence indicates that the SRCs are key participants in governing numerous aspects of CD4+ T cell biology. Here we review findings that establish the SRCs as essential regulators of regulatory T cells (Tregs) and T helper 17 (Th17) cells, with a focus on their crucial roles in Treg immunity in cancer and Treg-Th17 cell phenotypic plasticity.

Arginase 1 and L-arginine coordinate fetal lung development and the initiation of labor in mice.

Fetal development and parturition are precisely regulated processes that involve continuous crosstalk between the mother and the fetus. Our previous discovery that wild-type mice carrying steroid receptor coactivator (Src)-1 and Src-2 double-deficient fetuses exhibit impaired lung development and delayed labor, which indicates that the signals for parturition emanate from the fetus. In this study, we perform RNA sequencing and targeted metabolomics analyses of the lungs from fetal Src-1/-2 double-knockout mice and find that expression of arginase 1 (Arg1) is significantly decreased, accompanied by increased levels of the Arg1 substrate L-arginine. Knockdown of Arg1 in the lungs of fetal mice induces apoptosis of epithelial cells and dramatically delays initiation of labor. Moreover, treatment of human myometrial smooth muscle cells with L-arginine significantly inhibits spontaneous contractions by attenuating activation of NF-κB and downregulating expression of contraction-associated protein genes. Transcription factors GR and C/EBPß increase transcription of Arg1 in an Src-1/Src-2-dependent manner. These findings provide new evidence that fetus-derived factors may play dual roles in coordinating fetal lung development and the initiation of labor.

Steroid receptor coactivators - their role in immunity.

Steroid Receptor Coactivators (SRCs) are essential regulators of transcription with a wide range of impact on human physiology and pathology. In immunology, SRCs play multiple roles; they are involved in the regulation of nuclear factor-κB (NF-κB), macrophage (MΦ) activity, lymphoid cells proliferation, development and function, to name just a few. The three SRC family members, SRC-1, SRC-2 and SRC-3, can exert their immunological function either in an independent manner or act in synergy with each other. In certain biological contexts, one SRC family member can compensate for lack of activity of another member, while in other cases one SRC can exert a biological function that competes against the function of another family counterpart. In this review we illustrate the diverse biological functionality of the SRCs with regard to their role in immunity. In the light of recent development of SRC small molecule inhibitors and stimulators, we discuss their potential relevance as modulators of the immunological activity of the SRCs for therapeutic purposes.

Targeting transcriptional regulators for treatment of anaplastic thyroid cancer.

Dysregulation of genes perpetuates cancer progression. During carcinogenesis, cancer cells acquire dependency of aberrant transcriptional programs (known as "transcription addiction") to meet the high demands for uncontrolled proliferation. The needs for particular transcription programs for cancer growth could be cancer-type-selective. The dependencies of certain transcription regulators could be exploited for therapeutic benefits. Anaplastic thyroid cancer (ATC) is an extremely aggressive human cancer for which new treatment modalities are urgently needed. Its resistance to conventional treatments and the lack of therapeutic options for improving survival might have been attributed to extensive genetic heterogeneity due to subsequent evolving genetic alterations and clonal selections during carcinogenesis. Despite this genetic complexity, mounting evidence has revealed a characteristic transcriptional addiction of ATC cells resulting in evolving diverse oncogenic signaling for cancer cell survival. The transcriptional addiction has presented a huge challenge for effective targeting as shown by the failure of previous targeted therapies. However, an emerging notion is that many different oncogenic signaling pathways activated by multiple upstream driver mutations might ultimately converge on the transcriptional responses, which would provide an opportunity to target transcriptional regulators for treatment of ATC. Here, we review the current understanding of how genetic alterations in cancer distorted the transcription program, leading to acquisition of transcriptional addiction. We also highlight recent findings from studies aiming to exploit the opportunity for targeting transcription regulators as potential therapeutics for ATC.

An acetylation-enhanced interaction between transcription factor Sox2 and the steroid receptor coactivators facilitates Sox2 transcriptional activity and function.

SRY-box 2 (Sox2) is a transcription factor with critical roles in maintaining embryonic stem (ES) cell and adult stem cell functions and in tumorigenesis. However, how Sox2 exerts its transcriptional function remains unclear. Here, we used an in vitro protein-protein interaction assay to discover transcriptional regulators for ES cell core transcription factors (Oct4, Sox2, Klf4, and c-Myc) and identified members of the steroid receptor coactivators (SRCs) as Sox2-specific interacting proteins. The SRC family coactivators have broad roles in transcriptional regulation, but it is unknown whether they also serve as Sox2 coactivators. We demonstrated that these proteins facilitate Sox2 transcriptional activity and act synergistically with p300. Furthermore, we uncovered an acetylation-enhanced interaction between Sox2 and SRC-2/3, but not SRC-1, demonstrating it is Sox2 acetylation that promotes the interaction. We identified putative Sox2 acetylation sites required for acetylation-enhanced interaction between Sox2 and SRC-3 and demonstrated that acetylation on these sites contributes to Sox2 transcriptional activity and recruitment of SRC-3. We showed that activation domains 1 and 2 of SRC-3 both display a preferential binding to acetylated Sox2. Finally, functional analyses in mouse ES cells demonstrated that knockdown of SRC-2/3 but not SRC-1 in mouse ES cells significantly downregulates the transcriptional activities of various Sox2 target genes and impairs ES cell stemness. Taken together, we identify specific SRC family proteins as novel Sox2 coactivators and uncover the role of Sox2 acetylation in promoting coactivator recruitment and Sox2 transcriptional function.

Emerging roles of steroid receptor coactivators in stromal cell responses.

Tissue parenchyma is the functional unit of an organ and all of the remaining cells within that organ collectively make up the tissue stroma. The stroma includes fibroblasts, endothelial cells, immune cells, and nerves. Interactions between stromal and epithelial cells are essential for tissue development and healing after injury. These interactions are governed by growth factors, inflammatory cytokines and hormone signaling cascades. The steroid receptor coactivator (SRC) family of proteins includes three transcriptional coactivators that facilitate the assembly of multi-protein complexes to induce gene expression in response to activation of many cellular transcription factor signaling cascades. They are ubiquitously expressed and are especially critical for the developmental function of steroid hormone responsive tissues. The SRCs are overexpressed in multiple cancers including breast, ovarian, prostate and endometrial cancers. In this review, we focus on the role of the SRCs in regulating the functions of stromal cell components responsible for angiogenesis, inflammation and cell differentiation.

Decreased 11ß-hydroxysteroid dehydrogenase 1 in lungs of steroid receptor coactivator (Src)-1/-2 double-deficient fetal mice is caused by impaired glucocorticoid and cytokine signaling.

Our previous research revealed that steroid receptor coactivators (Src)-1 and -2 serve a critical cooperative role in production of parturition signals, surfactant protein A and platelet-activating factor, by the developing mouse fetal lung (MFL). To identify the global landscape of genes in MFL affected by Src-1/-2 double-deficiency, we conducted RNA-seq analysis of lungs from 18.5 days post-coitum (dpc) Src-1-/- /-2-/- (dKO) vs. WT fetuses. One of the genes most highly downregulated (~4.8 fold) in Src-1/-2 dKO fetal lungs encodes 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1), which catalyzes conversion of inactive 11-dehydrocorticosterone to the glucocorticoid receptor (GR) ligand, corticosterone. Glucocorticoids were reported to upregulate 11ß-HSD1 expression in various cell types via induction of C/EBP transcription factors. We observed that C/ebpα and C/ebpß mRNA and protein were markedly reduced in Src-1/-2 double-deficient (Src-1/-2d/d ) fetal lungs, compared to WT. Moreover, glucocorticoid induction of 11ß-hsd1, C/ebpα and C/ebpß in cultured MFL epithelial cells was prevented by the SRC family inhibitor, SI-2. Cytokines also contribute to the induction of 11ß-HSD1. Expression of IL-1ß and TNFα, which dramatically increased toward term in lungs of WT fetuses, was markedly reduced in Src-1/-2d/d fetal lungs. Our collective findings suggest that impaired lung development and surfactant synthesis in Src-1/-2d/d fetuses are likely caused, in part, by decreased GR and cytokine induction of C/EBP and NF-κB transcription factors. This results in reduced 11ß-HSD1 expression and glucocorticoid signaling within the fetal lung, causing a break in the glucocorticoid-induced positive feedforward loop.

Overexpression of steroid receptor coactivators alleviates hyperglycemia-induced endothelial cell injury in rats through activating the PI3K/Akt pathway.

Hyperglycemia is a major factor in vascular endothelial injury that finally leads to a cardiovascular event. Steroid receptor coactivators (SRCs) are a group of non-DNA binding proteins that induce structural changes in steroid receptors (nuclear receptors) critical for transcriptional activation. SRCs, namely, SRC-1, SRC-2, and SRC-3, are implicated in the regulation of vascular homeostasis. In this study we investigate the role of SRCs in hyperglycemia-induced endothelial injury. Aortic endothelial cells were prepared from normal and diabetic rats, respectively. Diabetic rats were prepared by injection of streptozotocin (50 mg/kg, i.p.). The expression levels of SRC-1 and SRC-3 were significantly decreased in endothelial cells from the diabetic rats. Similar phenomenon was also observed in aortic endothelial cells from the normal rats treated with a high glucose (25 mM) for 4 h or 8 h. The expression levels of SRC-2 were little affected by hyperglycemia. Overexpression of SRC-1 and SRC-3 in high glucose-treated endothelial cells significantly increased the cell viability, suspended cell senescence, and inhibited cell apoptosis compared with the control cells. We further showed that overexpression of SRC-1 and SRC-3 markedly suppressed endothelial injury through restoring nitric oxide production, upregulating the expression of antioxidant enzymes (SOD, GPX, and CAT), and activating the PI3K/Akt pathway. The beneficial effects of SRC-1 and SRC-3 overexpression were blocked by treatment with the PI3K inhibitor LY294002 (10 mM) or with the Akt inhibitor MK-2206 (100 nM). In conclusion, hyperglycemia decreased SRC-1 and SRC-3 expression levels in rat aortic endothelial cells. SRC-1 and SRC-3 overexpression might protect against endothelial injury via inhibition of oxidative stress and activation of PI3K/Akt pathway.

Hyperactivation of nuclear receptor coactivators induces PERK-dependent cell death.

Nuclear receptor coactivators (NCOAs) function as coactivators for nuclear receptors as well as several other transcription factors and potentiate their transcriptional activity. NCOAs play an important role in biology of hormone-dependent and -independent cancers. MCB-613 is a recently described, small molecule stimulator of NCOAs and anti-neoplastic compound that leads to the death of tumour cells due to increased cellular stress. In the present study we investigated the molecular mechanism of MCB-613-induced cell death. We report that absence of NCOA3 leads to compromised activation of PERK signalling pathway during unfolded protein response (UPR). We found that chemical and genetic inhibition of NCOA3 attenuated the expression of PERK at mRNA and protein level. We show that loss of NCOA3 renders cells hypersensitive to UPR induced cell death. Our results show that MCB-613 induced cell death is attenuated in NCOA3 knockout HeLa cells and MCB-613 leads to enhanced PERK signalling in wild-type HeLa cells. The knockdown of PERK provides resistance to MCB-613 mediated cell death while knockdown of XBP1 and ATF6 have no such effect. Our results suggest that hyperstimulation of NCOA3 by MCB-613 induces cell death by evoking constitutive PERK signalling. Taken together our results point to NCOA3 as an important determinant in regulating cell fate during ER stress, with too little and too much NCOA3 both producing deleterious effects.

Reprint of "Steroid receptor coactivators as therapeutic targets in the female reproductive system".

The steroid receptor coactivators (SRCs/p160/NCOA) are a family of three transcriptional coregulators initially discovered to transactivate the transcriptional potency of steroid hormone receptors. Even though SRCs were also found to modulate the activity of multiple other transcription factors, their function is still strongly associated with regulation of steroid hormone action and many studies have found that they are critical for the regulation of reproductive biology. In the case of the female reproductive tract, SRCs have been found to play crucial roles in its physiology, ranging from ovulation, implantation, to parturition. Not surprisingly, SRCs' action has been linked to numerous abnormalities and debilitating disorders of female reproductive tissues, including infertility, cancer, and endometriosis. Many of these pathologies are still in critical need of therapeutic intervention and "proof-of-principle" studies have found that SRCs are excellent targets in pathological states. Therefore, small molecule modulators of SRCs' activity could be applied in the future in the treatment of many diseases of the female reproductive system.

Steroid receptor coactivators as therapeutic targets in the female reproductive system.

The steroid receptor coactivators (SRCs/p160/NCOA) are a family of three transcriptional coregulators initially discovered to transactivate the transcriptional potency of steroid hormone receptors. Even though SRCs were also found to modulate the activity of multiple other transcription factors, their function is still strongly associated with regulation of steroid hormone action and many studies have found that they are critical for the regulation of reproductive biology. In the case of the female reproductive tract, SRCs have been found to play crucial roles in its physiology, ranging from ovulation, implantation, to parturition. Not surprisingly, SRCs' action has been linked to numerous abnormalities and debilitating disorders of female reproductive tissues, including infertility, cancer, and endometriosis. Many of these pathologies are still in critical need of therapeutic intervention and "proof-of-principle" studies have found that SRCs are excellent targets in pathological states. Therefore, small molecule modulators of SRCs' activity could be applied in the future in the treatment of many diseases of the female reproductive system.

The p160/steroid receptor coactivator family: potent arbiters of uterine physiology and dysfunction.

The p160/steroid receptor coactivator (SRC) family comprises three pleiotropic coregulators (SRC-1, SRC-2, and SRC-3; otherwise known as NCOA1, NCOA2, and NCOA3, respectively), which modulate a wide spectrum of physiological responses and clinicopathologies. Such pleiotropy is achieved through their inherent structural complexity, which allows this coregulator class to control both nuclear receptor and non-nuclear receptor signaling. As observed in other physiologic systems, members of the SRC family have recently been shown to play pivotal roles in uterine biology and pathobiology. In the murine uterus, SRC-1 is required to launch a full steroid hormone response, without which endometrial decidualization is markedly attenuated. From "dovetailing" clinical and mouse studies, an isoform of SRC-1 was recently identified which promotes endometriosis by reprogramming endometrial cells to evade apoptosis and to colonize as endometriotic lesions within the peritoneal cavity. The endometrium fails to decidualize without SRC-2, which accounts for the infertility phenotype exhibited by mice devoid of this coregulator. In related studies on human endometrial stromal cells, SRC-2 was shown to act as a molecular "pacemaker" of the glycolytic flux. This finding is significant because acceleration of the glycolytic flux provides the necessary bioenergy and biomolecules for endometrial stromal cells to switch from quiescence to a proliferative phenotype, a critical underpinning in the decidual progression program. Although studies on uterine SRC-3 function are in their early stages, clinical studies provide tantalizing support for the proposal that SRC-3 is causally linked to endometrial hyperplasia as well as with endometrial pathologies in patients diagnosed with polycystic ovary syndrome. This proposal is now driving the development and application of innovative technologies, particularly in the mouse, to further understand the functional role of this elusive uterine coregulator in normal and abnormal physiologic contexts. Because dysregulation of this coregulator triad potentially presents a triple threat for increased risk of subfecundity, infertility, or endometrial disease, a clearer understanding of the individual and combinatorial roles of these coregulators in uterine function is urgently required. This minireview summarizes our current understanding of uterine SRC function, with a particular emphasis on the next critical questions that need to be addressed to ensure significant expansion of our knowledge of this underexplored field of uterine biology.

Overexpression of steroid receptor coactivator-3 in bone cancers: an in vivo immunohistochemical study with tissue microarray.

Bone tissue is steroid-responsive and profoundly regulated by steroids and/or their receptors. Bone cancers (either primary or metastatic) belong to the most dangerous tumors. Previous studies have demonstrated overexpression of steroid receptor coactivator-3 (SRC-3) in many cancers, such as breast cancer, prostate cancer, thyroid cancer, functioning in the regulation of cancer cell proliferation, invasion, and metastasis. However, so far, the expression and function of SRC-3 in bone cancers have not yet been clarified. In this study, nickel-intensified immunohistochemistry was conducted using a commercial tissue microarray (with 94 cases of bone cancer tissue and 10 normal bone tissues), and the 4-scoring system was employed to evaluate the expression levels of SRC-3 immunoreactivity. The results showed that in normal bone tissue, levels of SRC-3 are almost negative (score=0), the total positivity (score=1-3) of SRC-3 immunoreactivities in bone cancers was 74.47%. There were no significant differences in gender, status (malignant or benign) or (mean) age (p>0.05). The percentage of positivity was 77.78% in osteogenic tumors, 58.82% in cartilage tumors, 70% in giant cell tumors, 100% in hematopoietic tumors, 77.78% in miscellaneous lesions, and 75% in miscellaneous tumors. Age related differences of SRC-3 immunoreactivities were detected in cartilage tumors and giant cell tumors (p<0.05). The above results clearly demonstrated a high frequency of overexpression of SRC-3 immunoreactivities in different bone cancers, indicating its potential roles in the prognosis and treatment of these cancers.

Indirect activation of the SV23 and SV24 splice variants of human constitutive androstane receptor: analysis with 3-hydroxyflavone and its analogues.

BACKGROUND AND PURPOSE: Naturally occurring splice variants of human CAR (hCAR), including hCAR-SV23 (insertion of amino acids SPTV) and hCAR-SV24 (APYLT), have been shown to be expressed in liver. However, little is known regarding how hCAR-SV23 and hCAR-SV24 are activated. Therefore, we investigated the mode of activation of these hCAR splice variants. EXPERIMENTAL APPROACH: Cell-based reporter gene assays, including ligand-binding domain transactivation assays and coactivator recruitment assays, were conducted on cultured HepG2 cells transfected with various constructs and treated with 3-hydroxyflavone or a hydroxylated (galangin, datiscetin, kaempferol, morin, quercetin or myricetin) or methylated (isorhamnetin, tamarixetin, or syringetin) analogue. KEY RESULTS: Among the flavonols investigated, only 3-hydroxyflavone increased hCAR-SV23 and hCAR-SV24 activities. 3-Hydroxyflavone did not transactivate the ligand-binding domain of these isoforms or recruit steroid receptor coactivators (SRC-1, SRC-2, or SRC-3). By comparison, 3-hydroxyflavone, galangin, datiscetin, kaempferol, quercetin, isorhamnetin and tamarixetin activated hCAR-WT, whereas none of the flavonols activated hCAR-SV25 (both SPTV and APYLT insertions). The flavonols 3-Hydroxyflavone, galangin, quercetin and tamarixetin transactivated the ligand-binding domain of hCAR-WT, but only 3-hydroxyflavone recruited SRC-1, SRC-2 and SRC-3 to the receptor. CONCLUSION AND IMPLICATIONS: hCAR-SV23 and hCAR-SV24 can be activated by a mechanism that does not involve the ligand-binding domain of the receptor or recruitment of SRC-1, SRC-2, or SRC-3. 3-Hydroxyflavone and its structural analogues activated hCAR in an isoform-selective and chemical-specific manner. Overall, our study provides insight into a novel mode of ligand activation of hCAR-SV23 and hCAR-SV24.

Oral exposure to bisphenol a increases dimethylbenzanthracene-induced mammary cancer in rats.

BACKGROUND: Bisphenol A (BPA) is widely used in the manufacture of polycarbonate plastics, including infant formula bottles. OBJECTIVES: Based on the reported endocrine disruptor activity of this polyphenol, we hypothesized that exposure to BPA early in life would elicit developmental changes in the mammary tissue and cause a predisposition for mammary cancer. METHODS: We exposed neonatal/prepubertal rats to BPA via lactation from nursing dams treated orally with 0, 25, and 250 mug BPA/kg body weight/day. For tumorigenesis studies, female offspring were exposed to 30 mg dimethylbenzanthracene (DMBA)/kg body weight at 50 days of age. RESULTS: The combination of DMBA treatment with lactational exposure to BPA demonstrated a dose-dependent increase in mammary tumor multiplicity and reduced tumor latency compared with controls. In the absence of DMBA treatment, lactational BPA exposure resulted in increased cell proliferation and decreased apoptosis at 50 but not 21 days postpartum (shortly after last BPA treatment). Using Western blot analysis, we determined that steroid receptor coactivators (SRCs) 1-3, Akt, phosphorylated Akt, progesterone receptor A (PR-A), and erbB3 proteins were significantly up-regulated at 50 days of age. CONCLUSIONS: The data presented here provide the first evidence that maternal exposure to BPA during lactation increases mammary carcinogenesis in a DMBA-induced model of rodent mammary cancer. Changes in PR-A, SRC 1-3, erbB3, and Akt activity are consistent with increased cell proliferation and decreased apoptosis playing a role in mammary cancer susceptibility. These alterations provide an explanation of enhanced mammary carcinogenesis after lactational BPA exposure.