Development of improved SRC-3 inhibitors as breast cancer therapeutic agents

Steroid receptor coactivators (SRCs) possess specific and distinct oncogenic roles in the initiation of cancer and in cancer progression to a more aggressive disease. These coactivators interact with nuclear receptors and other transcription factors to boost transcription of multiple genes which potentiate cancer cell proliferation, migration, invasion, tumor angiogenesis and epithelial mesenchymal transition (EMT). Targeting SRCs using small molecule inhibitors (SMIs) is a promising approach to control cancer progression and metastasis. By high throughput screening analysis, we recently identified SI-2 as a potent SRC SMI. To develop therapeutic agents, SI-10 and SI-12, the SI-2 analogs, are synthesized that incorporate the addition of fluorine atoms to the SI-2 chemical structure. As a result, these analogs exhibit a significantly prolonged plasma half-life, minimal toxicity and improved hERG activity. Biological functional analysis showed that SI-10 and SI-12 treatment (5-50 nM) can significantly inhibit viability, migration and invasion of breast cancer cells in vitro and repress the growth of breast cancer PDX organoids. Treatment of mice with 10 mg/kg/day of either SI-10 or SI-12 was sufficient to repress growth of xenograft tumors derived from MDA-MB-231 and LM2 cells. Furthermore, in spontaneous and experimental metastasis mouse models developed from MDA-MB-231 and LM2 cells respectively, SI-10 and SI-12 effectively inhibited progression of breast cancer lung metastasis. These results demonstrate that SI-10/SI-12 are promising therapeutic agents and are specifically effective in blocking tumor metastasis, a key point in tumor progression to a more lethal state that results in patient mortality in the majority of cases.

A Steroid Receptor Coactivator Stimulator MCB-613 Attenuates Adverse Remodeling After Myocardial Infarction

Previous work from ours and other laboratories have shown that steroid receptor coactivators (SRCs) are involved in heart development and in mitigating cardiac dysfunction in cardiac injury models. Members of the p160 SRC family, SRC-1 (NCOA1), SRC-2 (NCOA2/TIF2/GRIP1) and SRC-3 (NCOA3/AIB1/ACTR/pCIP), interact with nuclear receptors and other transcription factors to drive target gene expression by assembling transcriptional coactivator complexes to increase transcription. This indicates a potential for SRC targeting drugs pertinent to cell migration, proliferation and survival-promoting paracrine interactions in cardiac tissue injury responses. We have identified a small molecule activator of SRCs (MCB-613) that selectively and reversibly binds to SRCs as shown by surface plasmon resonance and is a potent SRC stimulator that acts to greatly enhance SRC transcriptional activity with no apparent toxicity in mice. We postulated that MCB-613 could enable wound repair and preservation of cardiac function after an acute MI by reducing the extent of injury-related fibrosis and the subsequent chronic loss of cardiac function associated with non-contracting scar tissue. We thus tested the effect of MCB-613 on the cardiac injury response by administering MCB-613 two hours after ischemic injury in a mouse model of MI. Along with measurements of functional cardiac output and damage, we sought to identify the cell-type specific responses responsible for MCB-613’s cardio-protective effects by utilizing single cell transcriptomics of cardiac interstitial cells to characterize the effects of SRC stimulation on cardiac function post-MI. We show that MCB-613, a potent small molecule stimulator of steroid receptor coactivators (SRCs) attenuates pathological remodeling post-MI. MCB-613 decreases infarct size, apoptosis, hypertrophy, and fibrosis while maintaining significant cardiac function. MCB-613, when given within hours post-MI, induces lasting protection from adverse remodeling concomitant with: (i) inhibition of macrophage inflammatory signaling and IL-1 signaling which attenuates the acute inflammatory response, (ii) attenuation of fibroblast differentiation, and (iii) promotion of Tsc22d3 expressing macrophages - all of which may limit inflammatory damage. Our results indicate MCB-613 controls the cellular interstitial cardiac repair response to ischemia. Distinct molecular and cellular mechanisms related to stimulation of SRC-3 have been identified that pave the way for the further exploration of SRCs as drug targets that can be engaged to improve the management of myocardial injury response outcomes. SRC stimulation with MCB-613 (and derivatives) is a potential novel therapeutic approach for inhibiting cardiac dysfunction after MI.

An Analysis of the Implication of Estrogens and Steroid Receptor Coactivators in the Genetic Basis of Gender Incongruence

In mammals, sex differences in the adult brain are established very early in development, when the brain is still very immature. In the case of having inherited the SRY gene, during embryogenesis, testosterone secreted by the testes enters the brain and is converted to estradiol by the aromatase. Then the estradiol acts by binding to intracellular estrogen receptors (ERs) located predominantly in neurons, masculinizing specific brain regions. But ERs are also transcription factors that, when they are exposed to their ligand, dimerize and form complexes with coactivator proteins and corepressors, modifying the transcription of multiple target genes in a cascade effect and ultimately neuronal function. Given the intimate relationship between steroids and brain dimorphism, and steroid coactivators and gene transcription, in the present work, we further explore the implication of ERs α and β, and steroid coactivators NCoA-1, NCoA-2, NCoA-3, NCoA-4, NCoA-5 and p300-CREBBP, in the genesis of brain dimorphism. Based on our data, we believe that the coactivators NCOA-1, NCOA-2 and p300-CREBBP could be considered as candidate genes for GI.

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 3 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.

A steroid receptor coactivator stimulator (MCB-613) attenuates adverse remodeling after myocardial infarction

Progressive remodeling of the heart, resulting in cardiomyocyte (CM) loss and increased inflammation, fibrosis, and a progressive decrease in cardiac function, are hallmarks of myocardial infarction (MI)-induced heart failure. We show that MCB-613, a potent small molecule stimulator of steroid receptor coactivators (SRCs) attenuates pathological remodeling post-MI. MCB-613 decreases infarct size, apoptosis, hypertrophy, and fibrosis while maintaining significant cardiac function. MCB-613, when given within hours post MI, induces lasting protection from adverse remodeling concomitant with: 1) inhibition of macrophage inflammatory signaling and interleukin 1 (IL-1) signaling, which attenuates the acute inflammatory response, 2) attenuation of fibroblast differentiation, and 3) promotion of Tsc22d3-expressing macrophages—all of which may limit inflammatory damage. SRC stimulation with MCB-613 (and derivatives) is a potential therapeutic approach for inhibiting cardiac dysfunction after MI.

Activation of COUP-TFI by a Novel Diindolylmethane Derivative

Chicken ovalbumin upstream promoter-transcription factor I (COUP-TFI) is an orphan receptor and member of the nuclear receptor superfamily. Among a series of methylene substituted diindolylmethanes (C-DIMs) containing substituted phenyl and heteroaromatic groups, we identified 1,1-bis(3′-indolyl)-1-(4-pyridyl)-methane (DIM-C-Pyr-4) as an activator of COUP-TFI. Structure activity studies with structurally diverse heteroaromatic C-DIMs showed that the pyridyl substituted compound was active and the 4-pyridyl substituent was more potent than the 2- or 3-pyridyl analogs in transactivation assays in breast cancer cells. The DIM-C-Pyr-4 activated chimeric GAL4-COUP-TFI constructs containing full length, C- or N-terminal deletions, and transactivation was inhibited by phosphatidylinositol-3-kinase and protein kinase A inhibitors. However, DIM-C-Pyr-4 also induced transactivation and interactions of COUP-TFI and steroid receptor coactivators-1 and -2 in mammalian two-hybrid assays, and ligand-induced interactions of the C-terminal region of COUP-TFI were not affected by kinase inhibitors. We also showed that DIM-C-Pyr-4 activated COUP-TFI-dependent early growth response 1 (Egr-1) expression and this response primarily involved COUP-TFI interactions with Sp3 and to a lesser extent Sp1 bound to the proximal region of the Egr-1 promoter. Modeling studies showed interactions of DIM-C-Pyr-4 within the ligand binding domain of COUP-TFI. This report is the first to identify a COUP-TFI agonist and demonstrate activation of COUP-TFI-dependent Egr-1 expression.