Sang Jun Han

Although they are not abundant, regulatory T cells (Tregs) are a critical component of the immune system that prevent autoimmune disease.1 his central role of Tregs in suppressing pathological immu...

The concept of nuclear receptor (NR) coregulation was proposed nearly 2 decades before it was experimentally validated. According to this model, NRs—executors of a vast array of transcriptional programs—do not act independently but are governed by a network of regulatory proteins that either activate or repress their biological function. Nuclear receptors identify the genes to be regulated. However, coregulators ultimately serve as the true controllers of transcriptional outcomes. They recruit cofactors and coordinate the activity of transcriptional complexes, thereby shaping NR-mediated gene expression beyond NRs’ intrinsic functionality. The steroid receptor coactivator (SRC) family is the most extensively studied and functionally dominant group of NR coregulators, modulating nearly all gene activities. The pleiotropic biological roles of SRCs—spanning key physiological and pathological processes—make them compelling therapeutic targets. Here, we outline the evolution of the coregulation concept, which reached a critical milestone with the discovery of the SRC family. We highlight the central roles of SRCs in both physiology and oncology and trace the development of therapeutic strategies aimed at targeting these proteins.

Regulatory T cells (Tregs) play a crucial role in the immune system, and their dysfunction can lead to the development of autoimmune conditions. In cancer, tumors frequently hijack the immunosuppressive function of Tregs to evade immune responses. Due to their central role in key pathological processes, Tregs have gained increasing attention as promising targets for various clinical applications. However, their relative scarcity (∼5% to 10% of CD4+ T cells) and instability presents a technical challenge for research and therapeutic development. In congenic animal models used to investigate autologous cell transfer–based therapies, this challenge is even greater, as Treg donor animals may only be able to provide cells to a small number of recipient mice. Here, we present an optimized protocol for ex vivo editing and expansion of mouse Tregs. Because a recent study demonstrated the anticancer potential of SRC-3 KO mouse Tregs, we use them here as a case study.

Steroid receptor coactivators (SRCs) are master regulators of nuclear receptor signaling and play essential roles in female reproductive physiology. By integrating steroid hormone signaling with growth factors and metabolic pathways, SRC-1, SRC-2, and SRC-3 coordinate key processes such as decidualization, placental development, and ovarian function. Dysregulation of SRCs is strongly linked to the progression of benign gynecologic disorders, including polycystic ovary syndrome (PCOS), endometriosis, and uterine fibroids, largely through enhancing hormonal hypersensitivity and disrupting nuclear receptor–mediated cellular pathways. Emerging evidence further implicates specific SRC isoforms in disease pathogenesis, underscoring their potential as biomarkers and therapeutic targets. To inhibit SRC activity, natural compounds (e.g., gossypol, bufalin, verrucarin A) and synthetic small molecules (e.g., SI-2, SI-12, MCB-613) have been developed, demonstrating preclinical efficacy across several human diseases. However, their application in benign reproductive disorders remains largely unexplored. This review summarizes current knowledge of SRC biology in benign gynecologic disorders, outlines their mechanistic roles in disease progression, and highlights opportunities for clinical translation. Targeting SRCs may ultimately represent a novel, nonhormonal, fertility-preserving therapeutic strategy in women’s health.

Endometriosis is a pathological condition characterized by the ectopic growth of endometrial cells, leading to chronic pelvic pain and infertility. Epidemiological studies have associated exposure to dioxin-like polychlorinated biphenyls, particularly PCB126, with an increased risk of endometriosis. However, the underlying mechanisms of this association remain poorly understood. We utilized a surgically induced endometriosis mouse model and human endometrial cell lines to assess the impact of PCB126 on endometriosis progression. Mice were exposed to environmentally relevant doses of PCB126. Endometriotic lesion growth, estrogen receptor signaling, receptor tyrosine kinase activity, and gene expression changes induced by PCB126-mediated elevation of DNA methyltransferase 3A (DNMT3A) were evaluated using histology, bioluminescent imaging, immunoblotting, and RNA sequencing. Functional validation was conducted using a pharmacologic AXL inhibitor and tissue-specific Dnmt3a knockout mice. PCB126 significantly promoted the growth of ectopic lesions and humanized models of endometriosis. Mechanistically, PCB126 enhanced estrogen receptor β (ESR2) activity by upregulating AXL and its ligand, growth arrest–specific 6, and elevating DNMT3A expression. The inhibition of AXL signaling suppressed the growth of endometriotic lesions. ESR2 directly regulated Dnmt3a expression, and loss of Dnmt3a reduced lesion growth and inflammatory cytokine production, thereby reversing immune dysregulation. These findings establish a mechanistic link between PCB126 exposure and epigenetic and immune reprogramming in endometriotic lesions. Our findings establish a mechanistic connection between environmental PCB126 exposure and endometriosis progression via the AXL/ESR2/DNMT3A axis. This study provides new insight into how endocrine-disrupting chemicals promote hormone-sensitive diseases through epigenetic and immunological pathways, offering potential targets for therapeutic intervention.

Previous studies show that orphan nuclear receptor 4A1 (NR4A1) regulated endometriotic cell growth, survival, estrogen receptor β (ERβ), mTOR signaling and fibrosis. NR4A2 is also expressed in epithelial and stromal derived endometriotic cells and in this study the effects of 1,1-bis(3’-indolyl)-(3,5-disubstitutedphenyl)methane (DIM-3,5) dual NR4A1/NR4A2 ligands and knockdown of NR4A1 and NR4A2 were investigated. The dual NR4A1/2 DIM-3,5 analogs inhibited previously identified pro-endometriotic pathways and gene products, and they also inhibited TWIST1, and multiple markers associated with epithelial-to-mesenchymal transition (EMT). The results show that both NR4A1 and NR4A2 regulate the same pathways including endometriotic cell growth, survival and migration and also some of the same genes in endometriotic epithelial and stromal cells. For example, DIM-3,5 compounds downregulate ERβ in stromal but not epithelial endometriotic cells and this response is NR4A1- and not NR4A2-dependent. Among the EMT-related markers, Claudin-1 is induced by DIM-3,5 ligands, and after knockdown of NR4A1 or NR4A2 in both epithelial and stromal cells. Most of the EMT markers are downregulated by DIM-3,5 ligands and are coregulated by NR4A1 and NR4A2. In vivo studies showed that DIM-3,5-Cl₂ significantly reduced the growth of endometriotic lesions in a mouse model without inducing cytotoxicity during treatment. Thus, DIM-3,5 derivatives simultaneously suppress NR4A1- and NR4A2-dependent endometriosis progression effectively and represent a promising non-hormonal therapeutic strategy to replace current hormone-based treatments, that can be associated with adverse effects.

Endometriosis is a pathological condition in which endometrial cells proliferate outside the uterine cavity, resulting in pelvic pain and infertility. Exposure to endocrine-disrupting chemicals (EDCs) has been implicated in the progression of endometriosis, though the precise mechanisms remain largely undefined. Among EDCs, elevated levels of polychlorinated biphenyl (PCB)-126 have been strongly associated with endometriosis, particularly in patients with deep infiltrating disease. In a mouse model of endometriosis, PCB-126 exposure significantly promoted the growth of ectopic lesions by activating the Steroid Receptor Coactivator-1 (SRC-1) isoform/Matrix Metalloproteinase-9 (MMP9)/Estrogen Receptor-β (ERβ) axis, a key driver of disease progression. PCB-126 also enhanced ERβ activity via upregulation of the AXL Receptor Tyrosine Kinase (AXL)/Growth Arrest-Specific 6 (GAS6) signaling pathway in endometriotic lesions. Notably, BMS-777607, an AXL inhibitor, effectively suppressed lesion growth in this model. Moreover, the PCB-126/ERβ axis directly increased expression of DNA Methyltransferase 3A (DNMT3A), contributing to inflammation and immune dysregulation in endometriotic tissue. Collectively, these findings suggest that PCB-126 promotes endometriosis progression through coordinated activation of the AXL/ERβ/DNMT3A axis, driving estrogen-mediated epigenetic and immunoinflammatory responses.

In patients with endometriosis, refluxed endometrial fragments evade host immunosurveillance, developing into endometriotic lesions. However, the mechanisms underlying this evasion have not been fully elucidated. N-Myc and STAT Interactor (NMI) have been identified as key players in host immunosurveillance, including interferon (IFN)-induced cell death signaling pathways. NMI levels are markedly reduced in the stromal cells of human endometriotic lesions due to modulation by the Estrogen Receptor beta/Histone Deacetylase 8 axis. Knocking down NMI in immortalized human endometrial stromal cells (IHESCs) led to elevated RNA levels of genes involved in cell-to-cell adhesion and extracellular matrix signaling following IFNA treatment. Furthermore, NMI knockdown inhibited IFN-regulated canonical signaling pathways, such as apoptosis mediated by Interferon Stimulated Gene Factor 3 and necroptosis upon IFNA treatment. In contrast, NMI knockdown with IFNA treatment activated non-canonical IFN-regulated signaling pathways that promote proliferation, including β-Catenin and AKT signaling. Moreover, NMI knockdown in IHESCs stimulated ectopic lesions’ growth in mouse endometriosis models. Therefore, NMI is a novel endometriosis suppressor, enhancing apoptosis and inhibiting proliferation and cell adhesion of endometrial cells upon IFN exposure.

In patients with endometriosis, refluxed endometrial fragments evade host immunosurveillance, developing into endometriotic lesions. However, the mechanisms underlying this evasion have not been fully elucidated. N-Myc and STAT Interactor (NMI) have been identified as key players in host immunosurveillance, including interferon (IFN)-induced cell death signaling pathways. NMI levels are markedly reduced in the stromal cells of human endometriotic lesions due to modulation by the Estrogen Receptor beta/Histone Deacetylase 8 axis. Knocking down NMI in immortalized human endometrial stromal cells (IHESCs) led to elevated RNA levels of genes involved in cell-to-cell adhesion and extracellular matrix signaling following IFNA treatment. Furthermore, NMI knockdown inhibited IFN-regulated canonical signaling pathways, such as apoptosis mediated by Interferon Stimulated Gene Factor 3, and necroptosis upon IFNA treatment. In contrast, NMI knockdown with IFNA treatment activated non-canonical IFN-regulated signaling pathways that promote proliferation, including β-Catenin and AKT signaling. Moreover, NMI knockdown in IHESCs stimulated ectopic lesions’ growth in mouse endometriosis models. Therefore, NMI is a novel endometriosis suppressor, enhancing apoptosis and inhibiting proliferation and cell adhesion of endometrial cells upon IFN exposure.

Nuclear receptor 4A1 (NR4A1) plays an important role in endometriosis progression; levels of NR4A1 in endometriotic lesions are higher than in normal endometrium, and substituted bis-indole analogs (NR4A1) antagonists suppress endometriosis progression in mice with endometriosis. In addition, the flavonoids kaempferol and quercetin are natural products that directly bind NR4A1 and significantly repress the intrinsic NR4A1-dependent transcriptional activity in human endometriotic epithelial and stromal cells and Ishikawa endometrial cancer cells. NR4A1 knockdown and inhibition of NR4A1 by kaempferol and quercetin suppressed proliferation of human endometriotic epithelial cells and Ishikawa cells by inhibiting epidermal growth factor receptor/c-Myc/survivin-mediated growth-promoting and survival pathways, The mammalian target of rapamycin (mTOR) signaling and αSMA/CTGF/COL1A1/FN-mediated fibrosis signaling but increasing Thioredoxin domain Containing 5/SESN2-mediated oxidative/estrogen receptors stress signaling. In human endometriotic stromal cells, NR4A1 knockdown and inhibition of NR4A1 by kaempferol and quercetin primarily inhibited mTOR signaling by suppressing proliferation of human endometrial stromal cells. In addition, kaempferol and quercetin treatment also effectively suppressed the growth of endometriotic lesions in mice with endometriosis compared with the vehicle without any body weight changes. Therefore, kaempferol and quercetin are NR4A1 antagonists with potential as nutritional therapy for endometriosis.