Nuclear receptors are key effectors of metabolic programs; however, the contribution of co-regulatory complexes in maintaining metabolic homeostasis is not fully understood. Here, we show that modulation of the constitutive androstane receptor (CAR) by the co-repressor silencing mediator of retinoic acid and thyroid hormone receptors (SMRT) is required for bile acid (BA) homeostasis. Transcriptional changes in the livers of mice harboring a targeted disruption in one of the nuclear receptor-interacting domains (RIDs), SMRTmRID1 mice, revealed increased expression of CAR target genes involved in BA export. Consistent with this, SMRTmRID1 mice challenged with a high-fat diet showed increased BAs in serum and urine with commensurate decreases in the liver and intestines. Notably, the reduction in intestinal BAs led to decreased activity of the BA receptor farnesoid X receptor (FXR). This reduction in FXR activity compromised the integrity of the intestinal barrier, increased bacterial burden, and augmented intestinal inflammation. Moreover, SMRTmRID1 mice were susceptible to intestinal damage, with higher mortality rates in acute colitis and colitis-associated cancer models. Treatment with a synthetic FXR agonist (XL335) rescued SMRTmRID1 mice during acute colitis. Collectively, these studies highlight the importance of SMRT in maintaining BA homeostasis through direct and indirect regulation of hepatic CAR and intestinal FXR activity, respectively, and point to potential therapeutic routes for combating intestinal pathologies associated with a high-fat diet. Nuclear receptors (NRs) have a crucial role in gene transcription regulation, impacting metabolic homeostasis. This study explores the disruption of the silencing mediator for retinoid and thyroid hormone receptors (SMRT) network in high-fat diet (HFD)-fed SMRTmRID1 mice, revealing its impact on bile acid (BA) homeostasis and intestinal health. Researchers used SMRTmRID1 knock-in mice, which have mutations in the RID1 domain, to study the effects of impaired SMRT–NR interactions. They found that disrupted SMRT function derepresses hepatic constitutive androstane receptor activity, leading to altered BA metabolism and reduced intestinal BA levels. This reduction impairs farnesoid X receptor-mediated mucosal defense, increasing intestinal permeability and inflammation. The study highlights the importance of the SMRT–NR network in maintaining BA homeostasis and suggests that farnesoid X receptor activation could mitigate intestinal dysfunction. Future research could explore tissue-specific SMRT models to further understand these interactions. This summary was initially drafted using artificial intelligence, then revised and fact-checked by the author.

Abstract The ability of tumor cells to tolerate DNA damage through a robust DNA damage response (DDR) limits the efficacy of many anticancer therapies, including genotoxic agents; however, the epigenetic mechanisms that sustain DDR gene expression remain poorly understood. Here, we identify Class I histone deacetylases (HDACs) as critical regulators of the DDR in pancreatic ductal adenocarcinoma (PDAC). HDAC1/2 maintain a proper genome-wide distribution of H3K27 acetylation, ensuring efficient recruitment of BRD4 and RNA polymerase II to DDR gene promoters. Pharmacological HDAC inhibition with entinostat preferentially enriches H3K27 acetylation at intergenic regions, diverting transcriptional machinery away from promoters and suppressing DDR gene expression. Consequently, HDAC inhibition increases DNA damage and sensitizes PDAC to diverse DNA-damaging (e.g., platinum agents, topoisomerase inhibitors) and DDR-targeting therapies (e.g., PARP inhibitors). To overcome the systemic toxicity that has limited the clinical translation of HDAC inhibitors, we developed a bottlebrush prodrug (BPD) nanoparticle platform for tumor-selective entinostat delivery. Entinostat-BPD enables tumor-specific HDAC inhibition, reduces system toxicity, and achieves tumor suppression comparable to free entinostat with only one-seventh of the cumulative drug exposure, demonstrating enhanced translational potential of this platform. Together, these findings uncover an HDAC-directed epigenetic mechanism that drives resistance to DNA damage-inducing agents and further establish combinatorial and precision-targeting strategies to improve PDAC outcomes. Given the central role of the DDR across cancer types and the widespread use of DNA-damaging therapies, this work may have broad therapeutic relevance beyond pancreatic cancer. Citation Format: Gaoyang Liang, Hung V. Nguyen, Jonathan Zhu, Hervé Tiriac, Hadiqa Zafar, Daniel Y. Cao, Gabriela Estepa, Dylan C. Nelson, Yang Dai, Tae Gyu Oh, Christopher Liddle, Ruth T. Yu, Andrew M. Lowy, Weiwei Fan, Morgan L. Truitt, Annette R. Atkins, Jeremiah A. Johnson, Michael Downes, Ronald M. Evans. HDAC inhibition sensitizes pancreatic cancer to DNA-damaging therapies via genome-wide redistribution of transcriptional machinery [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(8_Suppl):Abstract nr LB097.

Vitamin D receptor (VDR) agonists promote quiescence of cancer-associated fibroblasts and improve efficacy of chemotherapy in preclinical models of pancreatic cancer. We conducted a run-in phase trial with primary endpoint of safety when the VDR agonist paricalcitol is given with first-line gemcitabine and albumin-bound paclitaxel (GA) in patients with metastatic pancreatic cancer. Secondary endpoints included pharmacodynamic analyses. Thirty-six patients were randomized to GA plus placebo, GA plus intravenous paricalcitol or GA plus oral paricalcitol with pretreatment and on-treatment tumor biopsies. Paricalcitol was safely administered with GA, although five patients (42%) receiving oral paricalcitol had grade 2-4 hypercalcemia and required dose reduction. Nuclear VDR protein expression was heterogeneous across patients, and VDR was expressed in tumor, immune and stromal cells. Compared to pretreatment specimens, on-treatment biopsies had decreased proportion of αSMA+ fibroblasts, altered fibroblast VDR activation signature and greater density and spatial colocalization of CD8+ T cells with tumor cells in the GA-plus-paricalcitol arms. VDR expression was predictive of tumor response in the GA-plus-paricalcitol arms. Paricalcitol can be safely administered with chemotherapy to patients with metastatic pancreatic cancer, and on-treatment biopsies indicated favorable modulation of the tumor microenvironment by paricalcitol as predicted by preclinical models. ClinicalTrials.gov identifier: NCT03520790 .

While glucose uptake is a surrogate marker of brown fat activation, its role in thermogenesis remains uncertain. To ascertain when and how glucose can fuel thermogenesis, we generated brown adipocyte-specific RalGAPB knockout (KO) mice, which have constitutively active RalA and dramatically elevated glucose uptake due to the translocation of the glucose transporter Glut4 to the plasma membrane (PM). Lean mice with RalGAPB KO showed increased lipid accumulation in brown adipocytes through elevated de novo lipogenesis (DNL) and reduced oxidative metabolism; these mice exhibited markedly reduced energy expenditure and cold tolerance. DNL inhibitors rescued the defective oxidation and energy expenditure in the KO mice. Surprisingly, brown adipocyte DNL was not increased in obese RalGAPKO mice, but energy expenditure was. Moreover, obese KO mice lost more fat than controls during fasting, due to a combination of increased energy expenditure and reduced insulin levels that favored systemic lipid oxidation. RalA was activated in brown fat by β adrenergic stimulation due to increased insulin secretion, an effect that was required for cold tolerance. This process was repressed in obesity. Together, these findings reveal that increasing glucose uptake drives energy expenditure when DNL is restricted, underscoring the context-dependent role of glucose metabolism in brown fat thermogenesis.

The DNA damage response (DDR) is critical for pancreatic ductal adenocarcinoma (PDAC) development and therapeutic responses, including to genotoxic agents. While epigenetic modulators have been shown to contribute to the DDR, how chromatin regulation dictates responses to DNA damage in PDAC remains incompletely understood. Here, we identify Class I histone deacetylases (HDACs) as critical regulators of the DDR. HDAC1/2 direct the genomic distribution of H3K27ac, ensuring sufficient BRD4 and RNA polymerase II (Pol II) occupancy at DDR gene promoters. HDAC inhibition by entinostat shifts the balance of H3K27 acetylation preferentially toward intergenic regions, diverting BRD4 and Pol II from promoters, thereby suppressing DDR gene expression. In line with this, HDAC inhibition heightens DNA damage and sensitizes PDAC to diverse DNA-damaging and DDR-targeting agents. Since the clinical development of HDAC inhibitors has been limited by systemic toxicity, we developed bottlebrush prodrug (BPD) nanoparticles for tumor-selective entinostat delivery. Entinostat-BPD achieved tumor-specific HDAC inhibition while displaying potent efficacy and reduced systemic toxicity. These findings reveal an HDAC-dependent DDR vulnerability and offer combinational and precision targeting strategies to facilitate clinical translation and improve PDAC patient outcomes.

BACKGROUNDCheckpoint inhibitor-associated autoimmune diabetes mellitus (CIADM) is a rare but life-altering complication of immune checkpoint inhibitor (ICI) therapy. Biomarkers that predict type 1 diabetes (T1D) are unreliable for CIADM.AIMIn the present study, we sought to identify biomarkers for the prediction of CIADM.METHODSFrom our prospective biobank, we identified 14 patients with CIADM who had metastatic melanoma treated with anti-programed antibody death 1 (anti-PD-1) with or without anti-cytotoxic T lymphocyte-associated antibody protein 4 (anti-CTLA4). Controls were selected from the same biobank, matched 2:1. Pretreatment, on-ICI, and post-CIADM serum and PBMCs were analyzed. Serum was analyzed for T1D autoantibodies, C-peptide, glucose, and cytokines. PBMCs were profiled using flow cytometry. Pancreatic volume was measured using CT volumetry.RESULTSBefore treatment, patients with CIADM had smaller pancreatic volume (27% reduction, P = 0.044) and higher anti-glutamic acid decarboxylase autoantibody (anti-GAD) titers (median 2.9 vs. 0, P = 0.01). They had significantly higher baseline proportions of Th17 cells (P = 0.03), higher CD4+ central memory cells (P = 0.04), and lower naive CD4+ T cells (P = 0.01). With ICI treatment, greater declines in pancreatic volume were seen in patients with CIADM (P < 0.0001). Activated CD4+ T cell subsets increased significantly in CIADM and controls with immune-related adverse effects (IRAEs) but not in controls without IRAEs. Using only pretreatment results, we found that pancreatic volume, anti-GAD antibody titers, and the baseline immune flow profile were highly predictive of CIADM development, with an AUC of greater than 0.96.CONCLUSIONSPeople who develop CIADM are immunologically predisposed and have antecedent pancreatic and immunological changes that accurately predict disease with excellent sensitivity. These biomarkers could be used to guide ICI use, particularly when planning treatment for low-risk tumors.FUNDINGNational Health and Medical Research Council (NHMRC) Investigator grants 2033228, 2009476, and 2007839.

Mitochondrial energy metabolism is vital for muscle function and is tightly controlled at the transcriptional level, both in the basal state and during adaptive muscle remodeling. The importance of the transcription factors estrogen-related receptors (ERRs) in controlling innate mitochondrial energetics has been recently demonstrated. However, whether different ERR isoforms display distinct functions in glycolytic versus oxidative myofibers is largely unknown. Moreover, their roles in regulating exercise-induced adaptive mitochondrial biogenesis remain unclear. Using muscle-specific single and combinatorial knockout mouse models, we have identified both cooperative and distinct roles of the ERR isoforms ERRα and ERRγ in regulating mitochondrial energy metabolism in different muscles. We demonstrate the essential roles of both these ERRs in mediating adaptive mitochondrial biogenesis in response to exercise training. We further show that PGC1α-induced mitochondrial biogenesis is completely abolished in primary myotubes with ERRα deletion but not ERRγ, highlighting distinct roles of these two isoforms in adaptive mitochondrial remodeling. Mechanistically, we find that both ERRs directly bind to the majority of mitochondrial energetic genes and control their expression, largely through collaborative binding to the same genomic loci. Collectively, our findings reveal critical and direct regulatory roles of ERRα and ERRγ in governing both innate and adaptive mitochondrial energetics in skeletal muscle.

Nutritional status is a determining factor for growth during development and homeostatic maintenance in adulthood. In the context of muscle, growth hormone (GH) coordinates growth with nutritional status; however, the detailed mechanisms remain to be fully elucidated. Here, we show that the transcriptional repressor B cell lymphoma 6 (BCL6) maintains muscle mass by sustaining GH action. Muscle-specific genetic deletion of BCL6 at either perinatal or adult stages profoundly reduces muscle mass and compromises muscle strength. Conversely, muscle-directed viral overexpression of BCL6 significantly reverses the loss of muscle mass and strength. Mechanistically, we show that BCL6 transcriptionally represses the suppressor of cytokine signaling 2 to sustain the anabolic actions of GH in muscle. Additionally, we find that GH itself transcriptionally inhibits BCL6 through the Janus kinase and signal transducer and activator of transcription 5 (JAK/STAT5) pathway. Supporting the physiologic relevance of this feedback regulation, we show the coordinated suppression of muscle Bcl6 expression with the induction of GH in the fasted state. These findings reveal the complexity of the feedback controls modulating GH signaling and identify BCL6 as a key homeostatic regulator coordinating muscle mass with nutrient availability. Moreover, these studies open avenues for targeted therapeutic strategies to combat muscle-wasting conditions.

Bile acids (BAs) affect the intestinal environment by ensuring barrier integrity, maintaining microbiota balance, regulating epithelium turnover, and modulating the immune system. As a master regulator of BA homeostasis, farnesoid X receptor (FXR) is severely compromised in patients with inflammatory bowel disease (IBD) and colitis-associated colorectal cancer (CAC). At the front line, gut macrophages react to the microbiota and metabolites that breach the epithelium. We aim to study the role of the BA/FXR axis in macrophages. This study demonstrates that inflammation-induced epithelial abnormalities compromised FXR signaling and altered BAs' profile in a mouse CAC model. Further, gut macrophage-intrinsic FXR sensed aberrant BAs, leading to pro-inflammatory cytokines' secretion, which promoted intestinal stem cell proliferation. Mechanistically, activation of FXR ameliorated intestinal inflammation and inhibited colitis-associated tumor growth, by regulating gut macrophages' recruitment, polarization, and crosstalk with Th17 cells. However, deletion of FXR in bone marrow or gut macrophages escalated the intestinal inflammation. In summary, our study reveals a distinctive regulatory role of FXR in gut macrophages, suggesting its potential as a therapeutic target for addressing IBD and CAC.

Vitamin D signals through the vitamin D receptor (VDR) to induce its end-organ effects. Hepatic stellate cells control development of liver fibrosis in response to stressors and vitamin D signaling decreases fibrogenesis. VDR expression in hepatocytes is low in healthy liver, and the role of VDR in hepatocyte proliferation is unclear. Hepatocyte-VDR null mice (hVDR) were used to assess the role of VDR and vitamin D signaling in hepatic regeneration. hVDR mice have impaired liver regeneration and impaired hepatocyte proliferation associated with significant differential changes in bile salts. Notably, mice lacking hepatocyte VDR had significant increases in expression of conjugated bile acids after partial hepatectomy, consistent with failure to normalize hepatic function by the 14-day time point tested. Real-time PCR of hVDR and control livers showed significant changes in expression of cell-cycle genes including cyclins D1 and E1 and cyclin-dependent kinase 2. Gene expression profiling of hepatocytes treated with vitamin D or control showed regulation of groups of genes involved in liver proliferation, hepatitis, liver hyperplasia/hyperproliferation, and liver necrosis/cell death. Together, these studies demonstrate an important functional role for VDR in hepatocytes during liver regeneration. Combined with the known profibrotic effects of impaired VDR signaling in stellate cells, the studies provide a mechanism whereby vitamin D deficiency would both reduce hepatocyte proliferation and permit fibrosis, leading to significant liver compromise.

Mitochondrial dysfunction is a characteristic trait of human and rodent obesity, insulin resistance and fatty liver disease. Here we show that high-fat diet (HFD) feeding causes mitochondrial fragmentation in inguinal white adipocytes from male mice, leading to reduced oxidative capacity by a process dependent on the small GTPase RalA. RalA expression and activity are increased in white adipocytes after HFD. Targeted deletion of RalA in white adipocytes prevents fragmentation of mitochondria and diminishes HFD-induced weight gain by increasing fatty acid oxidation. Mechanistically, RalA increases fission in adipocytes by reversing the inhibitory Ser637 phosphorylation of the fission protein Drp1, leading to more mitochondrial fragmentation. Adipose tissue expression of the human homolog of Drp1, DNM1L , is positively correlated with obesity and insulin resistance. Thus, chronic activation of RalA plays a key role in repressing energy expenditure in obese adipose tissue by shifting the balance of mitochondrial dynamics toward excessive fission, contributing to weight gain and metabolic dysfunction.

Abstract Disclosure: L. Wu: None. J. Wentworth: None. C. Liddle: None. M. Carlino: Consulting Fee; Self; Amgen Inc, Bristol-Myers Squibb, Novartis Pharmaceuticals, Pierre Fabre, Regeneron Pharmaceuticals, Roche Pharmaceuticals, Merck, Sanofi. D. Brown: None. R.J. Clifton-Bligh: None. G. Long: Consulting Fee; Self; Amgen Inc, AstraZeneca, Boehringer Ingelheim, Bristol-Myers Squibb, Merck, Novartis Pharmaceuticals, Pierre Fabre, Regeneron Pharmaceuticals, Sandoz. S. Sasson: None. V. Tsang: None. A. Menzies: Consulting Fee; Self; Bristol-Myers Squibb, Novartis Pharmaceuticals, Roche Pharmaceuticals, Pierre Fabre. J.E. Gunton: None. Introduction: Checkpoint inhibitor associated autoimmune diabetes (CIADM) is a rare but highly morbid complication of immune checkpoint inhibitor (ICI) therapy. As indications for ICIs expand, the ability to predict CIADM has huge potential value and has yet to extensively explored. Aims: To identify potential biomarkers for prediction of CIADM in patients commencing ICI therapy. Methods: 14 patients with metastatic melanoma treated with ICI who subsequently developed CIADM were identified. 28 matched controls were identified (matched for ICI type, gender, cancer response and other immune related adverse events). Pre-treatment, on ICI and post CIADM serum and PBMCs were analysed. Serum was analysed for type 1 diabetes autoantibodies, C-peptide, glucose and an immune cytokine panel of TNFα, IL-2, IL-4, IL-6, IL-10, CXCL10, IL-1β, CCL2, IL-17A, CXCL8, TGF-B1, and IL-12p70. PBMCs were sorted using a BD Influx III cell sorter into 1000 CD8 cell subsets per sample. RNA was extracted and sequenced using a NovaSeq X with approximately 10 million 150bp paired end reads. RNA-Seq analysis was performed using edgeR. Results: Pre-ICI-treatment anti-GAD had a positive predictive value for CIADM prediction of 63.6% and a negative predictive value of 82.1%. Anti-IA2, anti-IAA and anti-ZnT8 were not predictive. C-peptide fell rapidly from 1.8nmol/L on treatment to 0.18nmol/L post diagnosis for CIADM and remains normal in controls. There were no significant differences in circulating cytokines between CIADM patients and controls. Pathway enrichment analysis performed on differentially expressed genes in people who developed CIADM identified significant regulation in pathways for B cell receptor and interferon signalling, RAS signalling and IGF1R signalling. These changes were not observed in controls. Conclusion: Anti-GAD has some predictive value for CIADM, but is incompletely sensitive. Further research is needed to prospectively test the predictive value of GAD Ab in combination with other potential markers such as pancreatic volumetry as we have previously published. Presentation: 6/2/2024

Transforming growth factor–β (TGFβ) drives fibrosis and disease progression in a number of chronic disorders, but targeting this ubiquitously expressed cytokine may not yield a viable and safe antifibrotic therapy. Here, we sought to identify alternative ways to inhibit TGFβ signaling using human hepatic stellate cells and macrophages from humans and mice in vitro, as well as mouse models of liver, kidney, and lung fibrosis. We identified Mer tyrosine kinase (MERTK) as a TGFβ-inducible effector of fibrosis that was up-regulated during fibrosis in multiple organs in three mouse models. We confirmed these findings in liver biopsy samples from patients with metabolic dysfunction-associated fatty liver disease (MAFLD). MERTK also induced TGFβ expression and drove TGFβ signaling resulting in a positive feedback loop that promoted fibrosis in cultured cells. MERTK regulated both canonical and noncanonical TGFβ signaling in both mouse and human cells in vitro. MERTK increased transcription of genes regulating fibrosis by modulating chromatin accessibility and RNA polymerase II activity. In each of the three mouse models, disrupting the fibrosis-promoting signaling loop by reducing MERTK expression reduced organ fibrosis. Pharmacological inhibition of MERTK reduced fibrosis in these mouse models either when initiated immediately after injury or when initiated after fibrosis was established. Together, these data suggest that MERTK plays a role in modulating organ fibrosis and may be a potential target for treating fibrotic diseases.

Despite numerous female contraceptive options, nearly half of all pregnancies are unintended. Family planning choices for men are currently limited to unreliable condoms and invasive vasectomies with questionable reversibility. Here, we report the development of an oral contraceptive approach based on transcriptional disruption of cyclical gene expression patterns during spermatogenesis. Spermatogenesis involves a continuous series of self-renewal and differentiation programs of spermatogonial stem cells (SSCs) that is regulated by retinoic acid (RA)-dependent activation of receptors (RARs), which control target gene expression through association with corepressor proteins. We have found that the interaction between RAR and the corepressor silencing mediator of retinoid and thyroid hormone receptors (SMRT) is essential for spermatogenesis. In a genetically engineered mouse model that negates SMRT-RAR binding (SMRTmRID mice), the synchronized, cyclic expression of RAR-dependent genes along the seminiferous tubules is disrupted. Notably, the presence of an RA-resistant SSC population that survives RAR de-repression suggests that the infertility attributed to the loss of SMRT-mediated repression is reversible. Supporting this notion, we show that inhibiting the action of the SMRT complex with chronic, low-dose oral administration of a histone deacetylase inhibitor reversibly blocks spermatogenesis and fertility without affecting libido. This demonstration validates pharmacologic targeting of the SMRT repressor complex for non-hormonal male contraception.

CYP2D6 genotype and phenotype for each subject

Oncogenic lesions in pancreatic ductal adenocarcinoma (PDAC) hijack the epigenetic machinery in stromal components to establish a desmoplastic and therapeutic resistant tumor microenvironment (TME). Here we identify Class I histone deacetylases (HDACs) as key epigenetic factors facilitating the induction of pro-desmoplastic and pro-tumorigenic transcriptional programs in pancreatic stromal fibroblasts. Mechanistically, HDAC-mediated changes in chromatin architecture enable the activation of pro-desmoplastic programs directed by serum response factor (SRF) and forkhead box M1 (FOXM1). HDACs also coordinate fibroblast pro-inflammatory programs inducing leukemia inhibitory factor (LIF) expression, supporting paracrine pro-tumorigenic crosstalk. HDAC depletion in cancer-associated fibroblasts (CAFs) and treatment with the HDAC inhibitor entinostat (Ent) in PDAC mouse models reduce stromal activation and curb tumor progression. Notably, HDAC inhibition (HDACi) enriches a lipogenic fibroblast subpopulation, a potential precursor for myofibroblasts in the PDAC stroma. Overall, our study reveals the stromal targeting potential of HDACi, highlighting the utility of this epigenetic modulating approach in PDAC therapeutics.

Endoxifen level for patients on moderate or strong CYP2D6 inhibitors

Supplemental Table 1. QPCR PRIMERS