Glucocorticoid Receptor Target Genes Research Articles

Abstract 6275: Exposure to neighborhood violence rewires glucocorticoid receptor binding and drives proliferation and invasiveness in lung tumor samples

Abstract Background: Despite smoking less, Black men experience higher incidence of lung cancer compared to white men. This health disparity is even more prevalent in Black men from Chicago, suggesting local neighborhood factors impacting tumorigenesis. Preliminary data indicate that, compared to white men, Black men are more likely to reside in neighborhoods with high levels of violence and have elevated levels of hair cortisol. Objective: To understand the link between lung tumorigenesis and exposure to neighborhood violence, our objective is to investigate the chromatin recruitment of the receptor for cortisol, called the glucocorticoid receptor (GR), and to correlate this recruitment with target gene expression levels. Methods: Utilizing CUT & RUN, we identified the gene binding sites of GR using 15 lung tumor and corresponding healthy tissue samples from lung cancer patients living in Chicago. GR recruitment to chromatin was correlated with the neighborhood homicide rate obtained using patients’ zip codes. Spatial transcriptome profiles for these 15 lung tumor samples were obtained from the Space Ranger pipeline and gene expression hot spots of GR target genes were visualized using Loupe Browser (10x Genomics). Results: GR recruitment to regulatory regions of chromatin increases with greater zip code level violence rates. In patients from high violence neighborhoods, tumor samples had higher magnitude of binding compared to normal neighboring tissue. In tumor samples from patients living in high violence compared to low violence neighborhoods, GR binding is seen in genes that are associated with increased tumor aggressiveness. Hot-spot analysis of these genes found strong co-expression of genes associated with proliferation and invasion in samples from high violence but not low violence neighborhoods. Conclusion: Exposure to neighborhood violence may impact tumor biology via increased GR recruitment to genes associated with proliferation and invasion. Citation Format: Hannah Heath, Jin Young Yoo, Vani Sharma, Hannah McGee, Aiman Soliman, Abeer Mohamed, Alicia K. Matthews, Robert Winn, Zeynep Madak-Erdogan, Sage Kim. Exposure to neighborhood violence rewires glucocorticoid receptor binding and drives proliferation and invasiveness in lung tumor samples [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6275.

The glucocorticoid receptor as a master regulator of the Müller cell response to diabetic conditions in mice

Diabetic retinopathy (DR) is considered a primarily microvascular complication of diabetes. Müller glia cells are at the centre of the retinal neurovascular unit and play a critical role in DR. We therefore investigated Müller cell-specific signalling pathways that are altered in DR to identify novel targets for gene therapy. Using a multi-omics approach on purified Müller cells from diabetic db/db mice, we found the mRNA and protein expression of the glucocorticoid receptor (GR) to be significantly decreased, while its target gene cluster was down-regulated. Further, oPOSSUM TF analysis and ATAC- sequencing identified the GR as a master regulator of Müller cell response to diabetic conditions. Cortisol not only increased GR phosphorylation. It also induced changes in the expression of known GR target genes in retinal explants. Finally, retinal functionality was improved by AAV-mediated overexpression of GR in Müller cells. Our study demonstrates an important role of the glial GR in DR and implies that therapeutic approaches targeting this signalling pathway should be aimed at increasing GR expression rather than the addition of more ligand.Graphical

FGF21 Induces Skeletal Muscle Atrophy and Increases Amino Acids in Female Mice: A Potential Role for Glucocorticoids.

Fibroblast growth factor-21 (FGF21) is an intercellular signaling molecule secreted by metabolic organs, including skeletal muscle, in response to intracellular stress. FGF21 crosses the blood-brain barrier and acts via the nervous system to coordinate aspects of the adaptive starvation response, including increased lipolysis, gluconeogenesis, fatty acid oxidation, and activation of the hypothalamic-pituitary-adrenocortical (HPA) axis. Given its beneficial effects for hepatic lipid metabolism, pharmaceutical FGF21 analogues are used in clinical trials treatment of fatty liver disease. We predicted pharmacologic treatment with FGF21 increases HPA axis activity and skeletal muscle glucocorticoid signaling and induces skeletal muscle atrophy in mice. Here we found a short course of systemic FGF21 treatment decreased muscle protein synthesis and reduced tibialis anterior weight; this was driven primarily by its effect in female mice. Similarly, intracerebroventricular FGF21 reduced tibialis anterior muscle fiber cross-sectional area; this was more apparent among female mice than male littermates. In agreement with the reduced muscle mass, the topmost enriched metabolic pathways in plasma collected from FGF21-treated females were related to amino acid metabolism, and the relative abundance of plasma proteinogenic amino acids was increased up to 3-fold. FGF21 treatment increased hypothalamic Crh mRNA, plasma corticosterone, and adrenal weight, and increased expression of glucocorticoid receptor target genes known to reduce muscle protein synthesis and/or promote degradation. Given the proposed use of FGF21 analogues for the treatment of metabolic disease, the study is both physiologically relevant and may have important clinical implications.

The Transcription Factors NFATc1 and NFATc2 Control Glucocorticoid Resistance in Pediatric T-Cell Acute Lymphoblastic Leukemia

Background: The overall survival of pediatric T-cell Acute Lymphoblastic Leukemia (T-ALL) is significantly improved (˜75-80%) with the current therapeutic approaches. Nevertheless, for those patients that do not respond to conventional treatment and experience relapse, the prognosis is extremely poor. In this context, it is well defined that resistance to glucocorticoids (GCs), pillar drugs in the treatment protocol, can predispose pediatric T-ALL patients to a poor outcome. A pivotal role of LCK kinase has been elucidated in supporting GC resistance in T-ALL cells in our previous study and recently confirmed by other colleagues. However, to date, the biological processes modulated by LCK in this context are not yet defined. Aim: the identification of new mechanisms underlying GC resistance can lead to alternative therapeutic approaches to prevent or overcome GC resistance and ameliorate the outcome of this subgroup of patients. Methods and Results: we uncovered the involvement of NFATc1 and NFATc2 transcription factors, that act downstream LCK kinase, in guiding GC resistance in T-ALL cells. Of note, a high NFATc1 and NFATc2 transcriptional activity characterizes pediatric GC resistant T-ALL patients at diagnosis, that in turns show a low Glucocorticoid Receptor (GR) activity. In agreement, NFATc1 or NFATc2 specific gene silencing in 3 T-ALL GC resistant cell line models and primary cells increases dexamethasone response, by restoring GR canonical transcriptional activity through the increaseexpression of BIM GR targetgene (p value <0.05). Conversely, NFATc1 or NFATc2 overexpression in a murine T-ALL GC sensitive cell line confers resistance to dexamethasone treatment. Interestingly, by Gene Expression Profile (GEP) and Nuclear Magnetic Resonance (NMR) analysis, we observed that NFATc1 gene silencing in GC resistant cells significantly downregulates intracellular cholesterol abundance. Additionally, by Chromatin Immunoprecipitation (ChIP) we revealed that NFATc1 can directly control the transcription of HMGCS1, EBP and DHCR7, key enzymes of cholesterol biosynthesis process (n≥3, p value <0.05 for all the three genes). In agreement, exogenous cholesterol addition to NFATc1 knock-down cell lines rebuild dexamethasone resistance. Conversely, by GEP and flow cytometry analysis we observed that NFATc2 gene silencing in T-ALL GC resistant cells leads to a downregulation of the Wnt/β-catenin signaling pathway and to an increased T-cell differentiation. Furthermore, by ChIP analysis we revealed that in T-ALL GC resistant cells NFATc2 can directly affect the transcription of LRP6, a key Wnt/β-catenin signaling component (n=3, p value <0.05). In agreement, the Wnt/β-catenin signaling activation, by Wnt3a stimulation, restores dexamethasone resistance in NFATc2 knock-down T-ALL cells. Finally, we observed that the inhibition of cholesterol biosynthesis by simvastatin or of Wnt/β-catenin by PRI-724 increases GC sensitivity in T-ALL GC resistant cells by the High-Throughput drug synergism Screening (HTS) and the Highest Single Agent (HSA) approach. Conclusions: Overall, we revealed for the first time the involvement of NFATc1 and NFATc2 transcription factors in supporting GC resistance in T-ALL cells by the modulation of cholesterol biosynthesis and Wnt/β-catenin signaling, both processes well-described in sustaining chemotherapy resistance, paving the rationale to alternative therapeutic options for T-ALL GC resistant pediatric patients.

E47 as a novel glucocorticoid-dependent gene mediating lipid metabolism in patients with endogenous glucocorticoid excess.

E47 has been identified as a modulating transcription factor of glucocorticoid receptor target genes, its loss protecting mice from metabolic adverse effects of glucocorticoids. We aimed to analyze the role of E47 in patients with endogenous glucocorticoid excess [Cushing's syndrome (CS)] and its association with disorders of lipid and glucose metabolism. This is a prospective cohort study including 120 female patients with CS (ACTH-dependent = 79; ACTH-independent = 41) and 26 healthy female controls. Morning whole blood samples after an overnight fast were used to determine E47 mRNA expression levels in patients with overt CS before and 6-12 months after curative surgery. Expression levels were correlated with the clinical phenotype of the patients. Control subjects underwent ACTH stimulation tests and dexamethasone suppression tests to analyze short-term regulation of E47. E47 gene expression showed significant differences in patient cohorts with overt CS vs. patients in remission (p = 0.0474) and in direct intraindividual comparisons pre- vs. post-surgery (p = 0.0353). ACTH stimulation of controls resulted in a significant decrease of E47 mRNA expression 30min after i.v. injection compared to baseline measurements. Administration of 1 mg of dexamethasone overnight in controls did not change E47 mRNA expression. E47 gene expression showed a positive correlation with total serum cholesterol (p = 0.0036), low-density lipoprotein cholesterol (p = 0.0157), and waist-arm ratio (p = 0.0138) in patients with CS in remission. E47 is a GC-dependent gene that is upregulated in GC excess potentially aiming at reducing metabolic glucocorticoid side effects such asdyslipidemia.

Exposure to low-intensity noise exacerbates nonalcoholic fatty liver disease by activating hypothalamus pituitary adrenal axis

Noise exposure induces metabolic disorders, in a latent, chronic and complex way. However, there is no direct evidence elucidating the relationship between low-intensity noise exposure and nonalcoholic fatty liver disease (NAFLD). Male mice (n = 5) on high-fat diet (HFD) were exposed to an average of 75 dB SPL noise for 3 months to reveal the effect of noise exposure on NAFLD, where the potential mechanisms were explored. In vivo (n = 5) and in vitro models challenged with dexamethasone (DEX) were used to verify the role of hypothalamus pituitary adrenal (HPA) axis activation in hepatic lipid metabolism. Typical chronic-restraint stress (CRS, n = 8) was used to explore the role of depression in modifying activity of HPA axis. Finally, animal experiment (n = 8) was repeated to validate the roles of depression and HPA axis activation in NAFLD development. Chronic low-intensity noise exposure exacerbated NAFLD in mice on HFD characterized by hepatocyte steatosis, modified lipid metabolism and inflammation level. Plasma ACTH in H + N group was 1.5-fold higher than that in HFD group. Transcription of glucocorticoid receptor target genes was increased by chronic low-intensity noise exposure in HFD-treated mice. Excessive glucocorticoids mimicking HPA axis activation induced NAFLD in vivo and in vitro. Plasma ACTH increase and lipid storage also occurred in depressive mice stressed by CRS. More interestingly, the same noise exposure simultaneously induced depression in mice, disrupted the HPA axis homeostasis and exacerbated NAFLD in a repeated experiment. Thus, three-month exposure to 75 dB SPL noise was sufficient to exacerbate NAFLD progress in mice, where activation of HPA axis played a critical role. Depression played an intermediate role and contributed to HPA axis activation up-stream of the exacerbation.

REDD1 (regulated in development and DNA damage1) modulates the glucocorticoid receptor function in keratinocytes.

Glucocorticoids (GCs) are widely used for the treatment of inflammatory skin diseases despite significant adverse effects including skin atrophy. Effects of GCs are mediated by the glucocorticoid receptor (GR), a well-known transcription factor. Previously, we discovered that one of the GR target genes, REDD1, is causatively involved in skin atrophy. Here, we investigated its role in GR function using HaCaT REDD1 knockout (KO) keratinocytes. We found large differences in transcriptome of REDD1 KO and control Cas9 cells in response to glucocorticoid fluocinolone acetonide (FA): both the scope and amplitude of response were significantly decreased in REDD1 KO. The status of REDD1 did not affect GR stability/degradation during self-desensitization, and major steps in GR activation-its nuclear import and phosphorylation at activating Ser211. However, the amount of GR phosphorylated at Ser226 that may play negative role in GR signalling, was increased in the nuclei of REDD1 KO cells. GR nuclear import and transcriptional activity also depend on the composition of GR chaperone complex: exchange of chaperone FKBP51 (FK506-binding protein 5) for FKBP52 (FK506-binding protein 4) being a necessary step in GR activation. We found the increased expression and abnormal nuclear translocation of FKBP51 in both untreated and FA-treated REDD1 KO cells. Overall, our results suggest the existence of a feed-forward loop in GR signalling mediated by its target gene REDD1, which has translational potential for the development of safer GR-targeted therapies.

Identification of Glucocorticoid Receptor Target Genes That Potentially Inhibit Collagen Synthesis in Human Dermal Fibroblasts.

Over several decades, excess glucocorticoids (GCs) of endogenous or exogenous origin have been recognized to significantly inhibit collagen synthesis and accelerate skin aging. However, little is known regarding their molecular mechanisms. We hypothesized that the action of GCs on collagen production is at least partially through the glucocorticoid receptor (GR) and its target genes, and therefore aimed to identify GR target genes that potentially inhibit collagen synthesis in Hs68 human dermal fibroblasts. We first confirmed that dexamethasone, a synthetic GC, induced canonical GR signaling in dermal fibroblasts. We then collected 108 candidates for GR target genes reported in previous studies on GR target genes and verified that 17 genes were transcriptionally upregulated in dexamethasone-treated dermal fibroblasts. Subsequently, by individual knockdown of the 17 genes, we identified that six genes, AT-rich interaction domain 5B, FK506 binding protein 5, lysyl oxidase, methylenetetrahydrofolate dehydrogenase (NADP + dependent) 2, zinc finger protein 36, and zinc fingers and homeoboxes 3, are potentially involved in GC-mediated inhibition of collagen synthesis. The present study sheds light on the molecular mechanisms of GC-mediated skin aging and provides a basis for further research on the biological characteristics of individual GR target genes.

Phase I trial of enzalutamide (Enz) plus the glucocorticoid receptor antagonist relacorilant (Rela) for patients with metastatic castration resistant prostate cancer.

5062 Background: Resistance to androgen receptor (AR) targeted therapies is common in mCRPC. Glucocorticoid receptor (GR) expression increases with AR inhibition in patients (pts) and blockade of GR signaling inhibits CRPC growth in preclinical models when combined with AR blockade. We thus conducted a phase I study of the combination of rela and enz in patients with mCRPC. Methods: The study used a 6+3 design to assess safety and pharmacokinetics (PK) of the 2-drug combination. The starting dose of rela 100mg/day was chosen based on current clinical studies indicating this dose was both safe for daily dosing and pharmacologically active and the starting dose for Enz was 120mg based on anticipated drug-drug interactions. Escalating doses of rela were combined with Enz 120 using pre-specified dose escalation rules. An additional 12 patients were to be assessed at the MTD to refine safety and PK profiles. Primary endpoint was safety of the combination and to establish safe and pharmacologically active doses of both agents. Key secondary endpoints were tumor response per RECIST 1.1 criteria and progression-free survival (PFS; defined as either PSA progression, radiographic progression or death). PSA was measured after 12 weeks or at the last time at which PSA data was available, including times <12 weeks. Results: 35 pts were enrolled. Pts had a median age of 74 (range 62-85) and baseline PSA of 89.5 (range 7.3-2391). 100% had prior potent AR signaling inhibitor (abi or enz) with 89% receiving prior enz, 94% prior abi, 83% prior both. 69% of pts received prior docetaxel. Median PSA change was 0.1%. Enz 120mg + Rela 100mg and Enz 120+Rela 150 were found to be safe and tolerable and achieved desirable Enz PK. DLTs were noted in 3 pts at the 200mg Rela dose, which was deemed to have exceeded the MTD, which was thus defined as 150mg Rela+120mg Enz. Most common ≥ grade 3 treatment related adverse events (TRAEs) were fatigue (11% of pts), anemia (9%), abdominal pain (6%) and pericardial effusion (6%). Median PFS was 2.5 months for 21 of 35 evaluable pts. Best response per RECIST 1.1 were Not Evaluable (40%), SD (34%) & PD (26%). No CR or PR were noted. Most common reasons for discontinuation from trial included progressive disease/hospice (82%), AEs (12%), physician discretion (3%) & death (3%). 2 pts remain on trial as of data cutoff (12/31/22). Conclusions: The combination of enzalutamide and relacorilant was safe & largely well tolerated. The majority of pts were discontinued from trial due to progressive disease or hospice. Further analyses of secondary & correlative endpoints such as translational/endocrine biomarkers, GR target gene expression and circulating tumor cells are ongoing. Clinical trial information: NCT03674814 .

EJE Prize 2023: genes on steroids-genomic control of hepatic metabolism by the glucocorticoid receptor.

Glucocorticoids are essential hormones produced by the adrenal cortex with prominent circadian rhythmicity and in times of stress. Glucocorticoids maintain liver homeostasis through coordinated activities that control the major pathways of energy metabolism. Glucocorticoids activate the glucocorticoid receptor (GR), a nuclear hormone receptor that regulates the transcription of hundreds of genes in response to ligand. This review aims to provide a comprehensive overview of glucocorticoid receptor signaling impact on glucose, amino acid, and lipid metabolism in the liver. We integrate fundamental and current findings elucidating key GR-regulated pathways from a physiologic, biochemical, and molecular point-of-view. Here, we focus on the transcriptional regulation of well-characterized hepatic GR target genes, and on those GR co-factors that coordinate nutritional and hormonal signals.

Abstract 3434: Selective glucocorticoid receptor modulation reveals a new role for CLEC10A in patients with solid tumors

Abstract Selective glucocorticoid receptor (GR) modulators (SGRMs) represent a clinically validated mechanism of enhancing chemosensitivity and ameliorating the sequelae of hypercortisolism. While GRs reportedly control the expression of up to 20% of the human genome, specific targets of systemic GR antagonism in humans have yet to be identified. To address this question, we established a robust NanoString assay to measure candidate GR target genes in human blood and assessed them before and after therapy with the oral SGRM relacorilant, which selectively antagonizes the GR. In a randomized, controlled phase 2 study in patients with recurrent, platinum-resistant ovarian cancer (NCT03776812), gene changes were assessed in 139 patients after treatment with relacorilant + nab-paclitaxel (NP) or NP alone. Using cross-validated random forest methods, a gene panel that accurately identified patients who had received relacorilant was established (ROC AUC 0.945 +/- 0.038). In 13 patients who crossed over from NP alone to relacorilant + NP, the genes in the panel were modified only after crossover (paired t-test P=0.0003), validating the gene panel’s ability to detect GR activity. The 4 most induced (LILRB4, FPR3, CLEC10A, CCR2) and 4 most suppressed (CDKN1C, TNFRSF17, BRIP1, PDK1) genes by relacorilant + NP vs. NP alone were selected and shown to be reliable indicators of GR activity across clinical studies in patients with pancreatic, prostate, and other solid tumors (NCT04329949, NCT03674814, NCT02762981), independent of concomitant medications or other confounders. CLEC10A (C-type lectin domain containing 10A) was identified as a particularly sensitive marker of GR activity as its expression was strongly suppressed by the GR agonist prednisone in healthy volunteers (paired t-test P<0.00010, NCT03335956) and strongly induced by relacorilant in patients with solid tumors (paired t-test P<0.00010). CLEC10A induction in blood by relacorilant was associated with longer overall survival in patients with ovarian cancer treated with relacorilant + NP (HR=0.39, Cox PH P=0.0135). High baseline tumor CLEC10A expression was also associated with longer overall survival in a large tumor ‘omics’ database (N=1656 ovarian tumors; HR 0.8, log-rank P=0.0008). CLEC10A and the genes correlated with its expression were found to be primarily expressed by a specific subset of dendritic cells, supporting previous reports that GR agonism can suppress dendritic cells. This analysis of CLEC10A and other identified GR target genes confirmed that systemic GR activity in patients with a range of solid tumors can be modulated pharmacologically, indicates that GR modulation may be associated with survival in patients with ovarian cancer, and provides new insights into the systemic functions of the GR in humans. Citation Format: Nicoletta Colombo, Toon Van Gorp, Ursula A. Matulonis, Ana Oaknin, Rachel N. Grisham, Diane Provencher, Gini F. Fleming, Alexander B. Olawaiye, Erkut H. Borazanci, Russell Z. Szmulewitz, Subhagya A. Wadekar, Grace Mann, Hazel J. Hunt, Andrew E. Greenstein, Domenica Lorusso. Selective glucocorticoid receptor modulation reveals a new role for CLEC10A in patients with solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3434.

Phase 1 efficacy and pharmacodynamic results of exicorilant + enzalutamide in patients with metastatic castration-resistant prostate cancer.

145 Background: Metastatic castration-resistant prostate cancer (mCRPC) remains an incurable disease with significant morbidity. Androgen receptor (AR) signaling is a key driver of tumor growth in mCRPC, and AR-targeted therapies are the mainstay for patients (pts) with locally advanced or metastatic disease. Enzalutamide (ENZA) is commonly used, but resistance typically develops within 1–2 years. The glucocorticoid receptor (GR) can substitute for the AR, providing a tumor escape pathway (Arora et al. Cell 2013). In the 22Rv1 CRPC xenograft model, the selective GR modulator exicorilant (EXI) combined with ENZA reduced tumor growth, supporting the hypothesis that dual antagonism of GR + AR may block this escape pathway. Safety and pharmacokinetics from the first study of EXI + ENZA in pts with mCRPC (NCT03437941) were previously presented (Linch et al. ESMO 2022). Here, we report efficacy and pharmacodynamic (PD) results from the same study. Methods: Segment 1 (Seg 1) of this phase 1 study evaluated open-label, fasting, BID dosing of EXI (140 or 180 mg) + ENZA 160 mg QD. Segment 2 (Seg 2) tested QD dosing of EXI with food in a double-blind design: All pts received EXI 240 mg + ENZA and were randomized 3:1 to EXI titration (to 280 mg followed by 320 mg) or to remain on EXI 240 mg + placebo. Efficacy assessments included radiographic response and changes in prostate-specific antigen (PSA) levels. PSA was collected prior to study entry and PSA doubling times were calculated before and during treatment. PD analyses included baseline (BL) tumor GR expression and modulation of GR target genes in whole blood. As not all pts enrolled in Seg 1 were ENZA naïve, efficacy data are reported for Seg 2 only. Data cutoff date: July 7, 2022. Results: 39 pts were enrolled (Seg 1: 14, irrespective of prior ENZA exposure; Seg 2: 25, on a stable ENZA dose with rising PSA, defined as a 25% increase over nadir and absolute value >1 ng/mL). In Seg 2, there were no radiographic responses, 18 pts had a best overall response of stable disease per PCWG3, and 1 pt achieved a PSA response (≥50% PSA reduction from BL). BL tumor GR expression was detectable in all assessed tumors. PD analyses demonstrated EXI modulation of GR target genes, such as CDKN1C. Comparable PD effects were observed across EXI doses (240–320 mg QD). While BL 24-h urinary free cortisol (UFC) for most pts was within the normal range, improvements in PSA doubling times after treatment with EXI + ENZA were predominantly observed in pts with higher BL UFC ( P<0.05). Conclusions: This study did not include an ENZA-alone arm and was thus not designed to assess the contribution of EXI to the efficacy of the EXI + ENZA combination. In heavily pretreated pts with prior ENZA exposure, 1 PSA response and no radiographic responses were observed. PD analysis confirmed systemic GR modulation. Instances of PSA doubling time improvements were observed in pts with relatively higher UFC. Clinical trial information: NCT03437941 .

Oncogenic deubiquitination controls tyrosine kinase signaling and therapy response in acute lymphoblastic leukemia.

Dysregulation of kinase signaling pathways favors tumor cell survival and therapy resistance in cancer. Here, we reveal a posttranslational regulation of kinase signaling and nuclear receptor activity via deubiquitination in T cell acute lymphoblastic leukemia (T-ALL). We observed that the ubiquitin-specific protease 11 (USP11) is highly expressed and associates with poor prognosis in T-ALL. USP11 ablation inhibits leukemia progression in vivo, sparing normal hematopoiesis. USP11 forms a complex with USP7 to deubiquitinate the oncogenic lymphocyte cell-specific protein-tyrosine kinase (LCK) and enhance its activity. Impairment of LCK activity leads to increased glucocorticoid receptor (GR) expression and glucocorticoids sensitivity. Genetic knockout of USP7 improved the antileukemic efficacy of glucocorticoids in vivo. The transcriptional activation of GR target genes is orchestrated by the deubiquitinase activity and mediated via an increase in enhancer-promoter interaction intensity. Our data unveil how dysregulated deubiquitination controls leukemia survival and drug resistance, suggesting previously unidentified therapeutic combinations toward targeting leukemia.

Targeting PLZF Enhances Glucocorticoid Sensitivity in Acute Myeloid Leukemia

Glucocorticoids (GCs) are Glucocorticoid Receptor (GR) agonists that are extensively used in clinic, from management of autoimmune and inflammatory disorders to being the corner stone in treatment of adult and childhood lymphoid cancers. Unlike lymphoblastic leukemias, acute myeloid leukemia (AML) cells are generally resistant to glucocorticoids and the mechanisms underlying this resistance are yet to be elucidated. Recent efforts by our group and others suggest that certain genetic alterations, such as RUNX1 loss of function mutations, or therapy-induced stress by chemo-agents such as cytarabine or small molecules like FLT3-inhibitors could sensitize AML cells to GCs, most probably via up-regulation of glucocorticoid receptor (GR) expression. To better characterize GC-response in AML, we compared gene expression landscape of GC-resistant versus GC-sensitive AML cell lines exposed to dexamethasone (Dex) for different time points. Interestingly, we found that the number of down-regulated genes upon GC treatment is similar in both cell lines. However, GC-sensitive cell line showed 3 to 6 times more up-regulated genes following GC treatment compared to the resistant cell line. A significant portion of up-regulated genes in the sensitive cells were targets of GR transcription factor. Gene set enrichment analysis revealed up-regulation of genes associated with macrophage differentiation, inflammation, and apoptosis pathways only in the sensitive cells. To identify modulators of the GC response in AML, we conducted a genome-wide CRISPR/Cas9-based genetic screen on resistant cell lines in the presence or absence of Dex. We identified the promyelocytic leukemia zinc factor (PLZF) as a critical transcription factor that determines GC-response in AML cells. In line with this, we showed that PLZF knockdown conferred sensitivity to GC-resistant AML cells, whereas PLZF over-expression conferred resistance to the sensitive cells. Transcriptome analysis showed an overlap of up-regulated pathways between PLZF-depleted cells and GC-sensitive cells in presence of Dex including inflammation and apoptosis pathways, suggesting that PLZF depletion primes AML cells to GC-response. Furthermore, Dex treatment induced expression of a subset of GR target genes in PLZF depleted cells. Importantly, this effect was not associated with significant changes in GR global protein levels or sub-cellular distribution. PLZF has been recently shown to be a neosubstrate for Cereblon-mediated protein degradation. To define potential therapeutic strategies that target PLZF in AML, we selected two cereblon modulating molecules including Lenalidomide, which is commonly used in the clinic for treatment of hematological malignancies, and CC-3060 compound that is more potent in PLZF degradation. Combination of Dex with PLZF-degrading compounds increased cell death in a significant portion of 95 primary AML samples tested, and as expected, a broader synergistic effect was obtained with CC-3060 compound. Combination of Dex and Lenalidomide appeared more effective in samples harboring NPM1 mutation, independently of recurrent additional mutations of FLT3 or DNMT3A. Importantly, these combinations had no cytotoxicity effect on normal CD34+ cordblood cells in vitro. Current efforts are ongoing to assess efficacy of this newly identified combinatorial therapy in vivo. All together our study shows that GR trans-activating capacity is diminished in resistant AML cells leading to a failure in activating pro-differentiation and anti-leukemic genes upon Dex treatment. PLZF interferes with GC-induced cell death in AML cells at least in part via suppressing 100 of genes involved in GC-response. PLZF suppression induces inflammatory response and sensitizes AML cells to anti-inflammatory effects of glucocorticoids. Based on our results, potent PLZF degrading compounds hold promises to potentiate GC-response in AML.

Peripheral glucocorticoid receptor antagonism by relacorilant with modest HPA axis disinhibition.

Glucocorticoid stress hormones are produced in response to hypothalamic-pituitary-adrenal (HPA) axis activation. Glucocorticoids are essential for physiology and exert numerous actions via binding to the glucocorticoid receptor (GR). Relacorilant is a highly selective GR antagonist currently undergoing a phase 3 clinical evaluation for the treatment of endogenous Cushing's syndrome. It was found that increases in serum adrenocorticotropic hormone (ACTH) and cortisol concentrations after relacorilant treatment were substantially less than the increases typically observed with mifepristone, but it is unclear what underlies these differences. In this study, we set out to further preclinically characterize relacorilant in comparison to the classical but non-selective GR antagonist mifepristone. In human HEK-293 cells, relacorilant potently antagonized dexamethasone- and cortisol-induced GR signaling, and in human peripheral blood mononuclear cells, relacorilant largely prevented the anti-inflammatory effects of dexamethasone. In mice, relacorilant treatment prevented hyperinsulinemia and immunosuppression caused by increased corticosterone exposure. Relacorilant treatment reduced the expression of classical GR target genes in peripheral tissues but not in the brain. In mice, relacorilant induced a modest disinhibition of the HPA axis as compared to mifepristone. In line with this, in mouse pituitary cells, relacorilant was generally less potent than mifepristone in regulating Pomc mRNA and ACTH release. This contrast between relacorilant and mifepristone is possibly due to the distinct transcriptional coregulator recruitment by the GR. In conclusion, relacorilant is thus an efficacious peripheral GR antagonist in mice with only modest disinhibition of the HPA axis, and the distinct properties of relacorilant endorse the potential of selective GR antagonist treatment for endogenous Cushing's syndrome.

Novel assays monitoring direct glucocorticoid receptor protein activity exhibit high predictive power for ligand activity on endogenous gene targets.

Exogenous glucocorticoids are widely used in the clinic for the treatment of inflammatory disorders and auto-immune diseases. Unfortunately, their use is hampered by many side effects and therapy resistance. Efforts to find more selective glucocorticoid receptor (GR) agonists and modulators (called SEGRAMs) that are able to separate anti-inflammatory effects via gene repression from metabolic effects via gene activation, have been unsuccessful so far. In this study, we characterized a set of functionally diverse GR ligands in A549 cells, first using a panel of luciferase-based reporter gene assays evaluating GR-driven gene activation and gene repression. We expanded this minimal assay set with novel luciferase-based read-outs monitoring GR protein levels, GR dimerization and GR Serine 211 (Ser211) phosphorylation status and compared their outcomes with compound effects on the mRNA levels of known GR target genes in A549 cells and primary hepatocytes. We found that luciferase reporters evaluating GR-driven gene activation and gene repression were not always reliable predictors for effects on endogenous target genes. Remarkably, our novel assay monitoring GR Ser211 phosphorylation levels proved to be the most reliable predictor for compound effects on almost all tested endogenous GR targets, both driven by gene activation and repression. The integration of this novel assay in existing screening platforms running both in academia and industry may therefore boost chances to find novel GR ligands with an actual improved therapeutic benefit.

592 REDD1/DDIT4 regulates the glucocorticoid receptor function in human keratinocytes

Glucocorticoids (Gcs) are widely used for inflammatory skin diseases. However, Gcs are also notorious for adverse effects such as skin atrophy. The glucocorticoid receptor (GR) is a transcription factor mediating Gcs action. Previously, we found that GR target gene REDD1 is causatively involved in atrophic effects of Gcs, and that REDD1 inhibitors could protect skin from steroid hypoplasia. In this work, we searched for the mechanisms underlying REDD1 effects on GR function using HaCaT REDD1 KO keratinocytes generated by CRISPR/Cas9 approach. Transcriptome analysis revealed that induction of GR target genes (FKBP51, SGK1, GILZ, BIRC3, and KLF9) by glucocorticoid fluocinolone acetonide (FA) in REDD1 KO was markedly lower than in Cas9-control cells. Interestingly, induction of mitochondrial GR targets, MT-ND2 and MT-CYTB, by FA was also decreased in REDD1 KO cells compared to control. This suggested the existence of novel feed forward loop in GR activation via REDD1. Next, we assessed whether a) REDD1 KO affected GR expression at RNA/protein levels, and b) modified the major steps in GR activation: GR phosphorylation at activation site Ser211 and GR nuclear import. Surprisingly, the difference between REDD1 KO and control cells in terms of GR expression and activation was rather marginal. We also did not find direct protein-protein interaction between GR and REDD1 using co-immunoprecipitation (co-IP). It is known that GR function is strongly regulated by chaperones including immunophilins FKBP51 and FKBP52. Specifically, FKBP51 inhibits GR activity via altered nuclear translocation and inhibition of interaction between GR and its ligands, and potentially may affect GR-DNA binding. We found that FKBP51 protein levels were increased in REDD1 KO keratinocytes, while FKBP52 levels did not change significantly. The ongoing experiments are focused on the evaluation of FKBP51 interaction with GR in the absence of REDD1 and the effect of FKBP51 knockdown on response of REDD1 KO cells to FA.

Application of a pharmacological transcriptome filter identifies a shortlist of mouse glucocorticoid receptor target genes associated with memory consolidation

Glucocorticoids regulate memory consolidation, facilitating long-term storage of relevant information to adequately respond to future stressors in similar conditions. This effect of glucocorticoids is well-established and is observed in multiple types of behaviour that depend on various brain regions. By and large, higher glucocorticoid levels strengthen event-related memory, while inhibition of glucocorticoid signalling impairs consolidation. The mechanism underlying this glucocorticoid effect remains unclear, but it likely involves the transcriptional effects of the glucocorticoid receptor (GR). We here used a powerful paradigm to investigate the transcriptional effects of GR in the dorsal hippocampus of mice after training in an auditory fear conditioning task, aiming to identify a shortlist of GR target genes associated to memory consolidation. Therefore, we utilized in an explorative study the properties of selective GR modulators (CORT108297 and CORT118335), alongside the endogenous agonist corticosterone and the classical GR antagonist RU486, to pinpoint GR-dependent transcriptional changes. First, we confirmed that glucocorticoids can modulate memory strength via GR activation. Subsequently, by assessing the specific effects of the available GR-ligands on memory strength, we established a pharmacological filter which we imposed on the hippocampal transcriptome data. This identified a manageable shortlist of eight genes by which glucocorticoids may modulate memory consolidation, warranting in-depth follow-up. Overall, we showcase the strength of the concept of pharmacological transcriptome filtering, which can be readily applied to other research topics with an established role of glucocorticoids.

Abstract 5728: A druggable FOXA1-glucocorticoid receptor transcriptional axis drives tumor growth in NSCLC

Abstract FOXA1 is a pioneer factor that is essential to steroid receptor function in hormone-dependent adenocarcinomas, including breast and prostate cancer. FOXA1 expression is also observed in other tumors of epithelial lineage such as non-small cell lung cancer (NSCLC), but whether and how it is required for tumor growth in these contexts is not known. Analyzing data from genome-scaled pooled loss-of-function screens, we identified and validated a subset of NSCLC cell lines with reduced cellular fitness following FOXA1 knockout. We performed a rapid immunoprecipitation and mass spectrometry of endogenous proteins (RIME) screen to nominate candidate factors that may cooperate with FOXA1 to mediate oncogenic transcription programs. This screen revealed a chromatin-localized interaction between FOXA1 and the glucocorticoid receptor (GR). Depletion of GR expression using shRNA or CRISPR/Cas9 suppressed the proliferation of FOXA1-dependent, but not FOXA1-independent NSCLC models, suggesting GR specifically contributes to tumor growth in the FOXA1-dependent context. To assess the potential therapeutic utility of targeting the FOXA1-GR signaling axis, we employed two structurally distinct ligand antagonists of GR from ORIC Pharmaceuticals: ORIC-101, a steroidal antagonist, and OP-4954, a non-steroidal antagonist. Both antagonists inhibited dexamethasone stimulated GR-transactivation of a glucocorticoid response element (GRE)-luciferase reporter with equal potency. However, proliferation and colony formation of the FOXA1/GR-dependent NSCLC cells were only inhibited upon treatment with ORIC-101, and not OP-4954. Gene expression analysis uncovered a discrete set of GR target genes, including SFTPB, TRAF4 and SGK1, whose expression was reduced by ORIC-101 but unaffected or even induced by OP-4954. The specific inhibition of GR target gene expression and attendant induction of apoptosis by ORIC-101 suggest a hierarchy of GR targets relevant to the FOXA1/GR-growth program in NSCLC. Finally, we evaluated the in vivo therapeutic potential of ORIC-101 using NSCLC xenografts and found that single-agent ORIC-101 exhibited potent antitumor effects in these models. Taken together, these data establish a model of FOXA1-GR-dependent tumor growth amongst a subset of NSCLCs and demonstrate that effective blockade of this complex is a rational therapeutic avenue to be explored in the clinic. Citation Format: Madeline Dorso. A druggable FOXA1-glucocorticoid receptor transcriptional axis drives tumor growth in NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5728.

Abstract 2348: Contribution of the GR/LEDGFp75 axis to prostate cancer chemoresistance

Abstract Prostate cancer (PCa) is the second leading cause of cancer deaths in the U.S., disproportionally affecting African American (AA) men. Glucocorticoids (GCs) are administered to PCa patients and have been implicated in therapy resistance. This may be critical to AA men with PCa since they have elevated endogenous GCs levels compared to Caucasian American (CA) men. GCs bind to the glucocorticoid receptor (GR) to exert their actions. The mechanisms of GR-mediated chemoresistance, and its possible contribution to PCa mortality disparities are unknown. We demonstrated that GCs upregulate the chemoresistance-associated protein and transcription co-activator LEDGF/p75 in PCa cells and identified consensus GR binding sites in the promoter region of this protein. Given that both GR and LEDGF/p75 are components of the RNA polymerase II transcription complex, we hypothesized that GR transcriptionally upregulates LEDGF/p75 and then interacts with it to enhance taxane resistance in PCa cells. Pharmacological and genetic inhibition of GR in a panel of docetaxel (DTX)-sensitive and -resistant PCa cells decreased the expression of LEDGF/p75, confirming its status as a candidate GR target gene. However, silencing of LEDGF/p75 had no effects on GR expression. Immunoprecipitation studies revealed that GR and LEDGF/p75 interact in DTX-resistant PCa cells. This interaction was confirmed by confocal microscopy. Immunohistochemical analysis of GR and LEDGF/p75 expression in normal and tumor prostate tissues was performed, and the results are currently being analyzed. Our studies use a mechanistic approach to evaluate the potential contribution of the GR-LEDGF/p75 axis to PCa chemoresistance. Evaluating the co-expression of these proteins in racially diverse PCa tissues may also reveal race-related differential expression, providing insights into the potential contribution of this axis to PCa chemoresistance and mortality disparities. Citation Format: Evelyn S. Sanchez Hernandez, Greisha L. Ortiz Hernandez, Pedro T. Ochoa, Christian R. Gomez, Carlos A. Casiano. Contribution of the GR/LEDGFp75 axis to prostate cancer chemoresistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2348.