Staphylococcus aureus activates the Aryl Hydrocarbon Receptor in Human Keratinocytes

Staphylococcus (S.) aureus is an important pathogen causing various infections including - as most frequently isolated bacterium - cutaneous infections. Keratinocytes as the first barrier cells of the skin respond to S. aureus by the release of defense molecules such as cytokines and antimicrobial peptides. Although several pattern recognition receptors expressed in keratinocytes such as Toll-like and NOD-like receptors have been reported to detect the presence of S. aureus, the mechanisms underlying the interplay between S. aureus and keratinocytes are still emerging. Here we report that S. aureus induced gene expression of CYP1A1 and CYP1B1, responsive genes of the aryl hydrocarbon receptor (AhR). AhR activation by S. aureus was further confirmed by AhR gene reporter assays. AhR activation was mediated by factor(s) < 2 kDa secreted by S. aureus. Whole transcriptome analyses and real-time PCR analyses identified IL-24, IL-6 and IL-1beta as cytokines induced in an AhR-dependent manner in S. aureus-treated keratinocytes. AhR inhibition in a 3D organotypic skin equivalent confirmed the crucial role of the AhR in mediating the induction of IL-24, IL-6 and IL-1beta upon stimulation with living S. aureus. Taken together, we further highlight the important role of the AhR in cutaneous innate defense and identified the AhR as a novel receptor mediating the sensing of the important skin pathogen S. aureus in keratinocytes.

Recurrent activating mutations in AHR act as drivers of urinary tract cancer

Bladder cancer is a common cancer with a high recurrence rate and with limited progress in treatment and survival of patients with advanced stages of the disease. The tumorigenesis of bladder cancer is still poorly understood, but identification of genetic contributors to its development may provide leads for targeted therapeutic approaches. By an in-depth analysis of whole-genome sequencing data of metastasized urinary tract cancer samples, we identified a novel recurrent in-frame deletion of exons 8 and 9 in the aryl hydrocarbon receptor (AHR) gene, encoding a ligand-activated transcription factor with context-specific physiological functions. The deletion (AHRΔe8-9) is highly specific to urinary tract cancer and occurs in 10.7% of metastatic lesions. Additionally, a recurrent AHR hotspot point mutation and AHR gene amplifications were identified indicating that alterations in the AHR gene are a key cancer driver event for urinary tract cancer adding up to a prevalence of ~19% (40 out of 206). The hotspot point mutation results in an amino acid change (AHRQ383H) in the ligand-binding domain of the protein and causes altered ligand affinities such as AHRQ383H activation upon incubation with the AhR antagonist CH-2233191. The in-frame deletion of exons 8 and 9 disrupt the ligand-binding domain and result in a constitutive nuclear localization of the protein and ligand-independent transcriptional activation. The constitutive activation of the AhR pathway by the hAHRΔe8-9 mutant in mouse bladder organoids induces dedifferentiation and enables anchorage independent growth. In conclusion, our results indicate that AhR is a key proto-oncogene and cancer driver gene in urinary tract cancer and emphasize the potential of the AhR pathway as a target for therapeutic interventions.

Aryl Hydrocarbon Receptor (AHR) Gene Expression in AML Is Associated with FLT3-ITD+ AML and HLA-E Induced Immune Resistance Reversed By Ik-364

Background: The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor critical for cellular metabolism, stem cell differentiation and immune control. HLA-E is a non-classical HLA molecule that is critical for NK cell activation. HLA-E is expressed on some AML blasts but genomic characterization is limited. IK-364, a tool compound generated by Ikena Oncology, is an AHR inhibitor in preclinical investigation. We set out to identify the genomic signatures associated with activation of the AHR pathway in AML samples utilizing the Beat AML dataset. Methods: Whole bone marrow or peripheral blood samples were procured from AML patients under IRB-approved protocol (eIRB# 4422). Utilizing the Beat AML database, all samples were examined based on RNA AHR expression levels (RPKM) and correlated with genomic expression. High vs. low AHR expression was based on 90 th and 10 th percentiles. Pathway enrichment from upregulated genes was identified and compared between high vs. low AHR expression. Single cell RNA sequencing by 10x genomics Chromium system by the Massively Parallel Sequencing Shared Resource at OHSU was performed with previously frozen FLT3 positive AML samples (4 high AHR and 4 low AHR). Immunophenotyping was conducted by flow cytometry. The AHR antagonist IK-364 was utilized to study the in vitro effects of AHR modulation. Cytotoxicity was measured by flow cytometric detection of caspase-3/7 and SytoxAAD activation. Results: The highest and lowest 10% expression levels of AHR in all samples in Beat AML were evaluated for mutation profiles. Ranking the top 18 mutations based on frequency we found an enrichment of FLT3 mutations in the high AHR expression group compared to the lower expression group (Figure 1A). ELN risk did not correlate with AHR expression however FAB classification M0/M1 and M4/M5 monocytic subtypes had higher AHR expression than M3 FAB subtype (Figure 2A). AHR gene expression was highly correlated with FLT3-ITD mutations (p=0.0007) (Figure 2B) and HLA-E expression (p=&lt;0.0001) (Figure 3A). High AHR and high HLA-E joint expression in AML was associated with pathway upregulation in translocation of ZAP70 to immunological synapse, upregulation of HLA class II antigen presentation, phosphorylation of CD3 and TCR zeta chain and PD-1 signaling (p-value-1.11E-16), which are critical for innate and adaptive immune responses. AHR low and HLA-E low AML samples showed pathway enrichment for down-regulated genes including Hedgehog on state and neurexins and neuroligins (p value-0.001 and 7.61E-04 respectively). Genes upregulated in AHR high samples included CD14, CD86, HLA-DR, LILRB4, MAFB which are associated with monocytic phenotype. AHR high FLT3+ AML samples had higher protein expression of HLA-E on CD45+ blasts (p=0.03) compared to AHR low FLT3+ AML samples. Pretreatment of FLT3+ AML primary patient samples with IK-364 for 48 hours downregulates HLA-E on blasts (p=0.007) and, in a FLT3 positive AML cell line, Molm14, enhanced susceptibility to NK-cell-mediated killing (Figure 3B, 3C). Discussion: Overall, we found that high AHR gene expression in AML correlates with FLT3-ITD expression and HLA-E as well as monocytic subtype. Pathway enrichment highlight the important role of AHR in immune regulation. Furthermore, AHR antagonism by IK-364, downregulates HLA-E on AML blasts and augments NK cell mediated killing of a mutant FLT3-ITD positive AML cell line. Our results highlight a continued interest in targeting the AHR pathway to augment immune-based therapies in AML.uture studies are underway to determine the mechanism behind this critical immune regulation. Figure 1 Figure 1. Disclosures Saultz: IKENA: Research Funding. Lind: IKENA: Research Funding. Tyner: Seattle Genetics: Research Funding; Constellation: Research Funding; Agios: Research Funding; Incyte: Research Funding; Petra: Research Funding; Gilead: Research Funding; Takeda: Research Funding; Janssen: Research Funding; Genentech: Research Funding; Array: Research Funding; Schrodinger: Research Funding; Astrazeneca: Research Funding. Kosaka: IKENA: Research Funding. McGovern: IKENA: Current Employment. Wang: IKENA: Current Employment. Sanchez-Martin: IKENA: Current Employment.

93 Computational biology and tissue-based approaches to inform indication selection for a novel AHR inhibitor

BackgroundAryl Hydrocarbon Receptor (AHR) is a ligand-activated transcription factor that regulates the activities of multiple innate and adaptive immune cell types. Multiple ligands such as kynurenine bind to AHR driving its nuclear translocation and transcriptional activation, leading to an immunosuppressive tumor microenvironment.1 2 AHR activation is implicated in tumor development in multiple cancer types. In addition, high levels of serum kynurenine are associated with resistance to checkpoint inhibitors.3 To overcome AHR-mediated immunosuppression in cancers, we developed a selective oral AHR inhibitor IK-175 and took a combined computational and tissue-based approach to select cancer indications for its clinical development.MethodsThe aim of this work is to identify tumor indications dependent on AHR signaling and design patient selection strategies based on a proprietary transcriptional signature, mRNA and protein detection assays to evaluate AHR pathway activation in tumors.ResultsGenomic profiling of solid and hematological cancers from TCGA and Project GENIE databases identified bladder and esophageal tumors among others, as frequently harboring AHR gene amplifications.A proprietary gene signature of AHR activation was developed integrating literature, pathway analysis, RNAseq and nanostring data from PBMC, T-cells and cell lines upon AHR inhibition. Transcriptional analysis of the TCGA data using this signature demonstrated bladder cancer has the highest expressions of AHR and AHR signature genes, suggesting increased pathway activity in bladder cancer relative to other cancer types. Increased AHR signature gene expression was associated with worse overall survival in the TCGA bladder cancer cohort. Furthermore, RNAscope analysis of a tissue microarray containing 10 different tumor types revealed bladder cancer had one of the highest AHR transcript expression in the tumor compartment.Finally, nuclear localization of AHR protein was assessed as an indicator of pathway activation through the development of a novel IHC method. Extensive TMA screening of AHR protein in 15 different indications demonstrated bladder cancer as the tumor type with the highest prevalence of AHR nuclear expression.ConclusionsIn summary, we demonstrated high prevalence of nuclear AHR protein expression, AHR gene amplification and target gene expression in bladder cancer, suggesting aberrant AHR activation may play an important role in the progression of this tumor type. This study provides rationale for therapeutic targeting of AHR in bladder cancer patients. Ikena is currently evaluating the anti-tumor activity of IK-175 as a single agent and in combination with nivolumab in bladder cancer in a Phase 1a/1b clinical study (NCT04200963).ReferencesQuintana FJ, Sherr DH. Aryl hydrocarbon receptor control of adaptive immunity. Pharmacol Rev 2013 Aug 1;65(4):1148–61.Murray IA, Patterson AD, Perdew GH. Aryl hydrocarbon receptor ligands in cancer: friend and foe. Nat Rev Cancer 2014 Dec;14(12):801–14.Li, Haoxin et al. ‘Metabolomic adaptations and correlates of survival to immune checkpoint blockade.’ Nature Communications 2019 Sep 25;10:1–4346.

AHR-dependent genes and response to MTX therapy in rheumatoid arthritis patients

Methotrexate (MTX) is the first-line therapy for rheumatoid arthritis. Nevertheless, MTX resistance is quite a common issue in clinical practice. There are some premises that aryl hydrocarbon receptor (AhR) gene battery may take part in MTX metabolism. In the present retrospective study, we analyzed genes expression of AHR genes battery associated with MTX metabolism in whole blood of RA patients with good and poor response to MTX treatment. Additionally, sequencing, genotyping and bioinformatics analysis of AHR repressor gene (AHRR) c.565C > G (rs2292596) and c.1933G > C (rs34453673) have been performed. Theoretically, both changes may have an impact on H3K36me3 and H3K27me3. Evolutionary analysis revealed that rs2292596 may be possibly damaging. Allele G in rs2292596 and DAS28 seems to be associated with a higher risk of poor response to MTX treatment in RA. RA patients with poor response to MTX treatment revealed upregulated AhR and SLC19A1 mRNA level. Treatment with IL-6 inhibitor may be helpful to overcome the low-dose MTX resistance. Analysis of gene expression revealed possible another cause of poor response to MTX treatment which is different from that observed in the case of acute lymphoblastic leukemia.

Dimethyl sulfoxide stimulates the AhR-Jdp2 axis to control ROS accumulation in mouse embryonic fibroblasts

The aryl hydrocarbon receptor (AhR) is a ligand-binding protein that responds to environmental aromatic hydrocarbons and stimulates the transcription of downstream phase I enzyme–related genes by binding the cis element of dioxin-responsive elements (DREs)/xenobiotic-responsive elements. Dimethyl sulfoxide (DMSO) is a well-known organic solvent that is often used to dissolve phase I reagents in toxicology and oxidative stress research experiments. In the current study, we discovered that 0.1% DMSO significantly induced the activation of the AhR promoter via DREs and produced reactive oxygen species, which induced apoptosis in mouse embryonic fibroblasts (MEFs). Moreover, Jun dimerization protein 2 (Jdp2) was found to be required for activation of the AhR promoter in response to DMSO. Coimmunoprecipitation and chromatin immunoprecipitation studies demonstrated that the phase I–dependent transcription factors, AhR and the AhR nuclear translocator, and phase II–dependent transcription factors such as nuclear factor (erythroid-derived 2)–like 2 (Nrf2) integrated into DRE sites together with Jdp2 to form an activation complex to increase AhR promoter activity in response to DMSO in MEFs. Our findings provide evidence for the functional role of Jdp2 in controlling the AhR gene via Nrf2 and provide insights into how Jdp2 contributes to the regulation of ROS production and the cell spreading and apoptosis produced by the ligand DMSO in MEFs. Graphical abstract

Lack of association between multiple polymorphisms in aryl hydrocarbon receptor (AhR) gene and cancer susceptibility

Background The aryl hydrocarbon receptor (AhR) is commonly known as an environmental sensor. Polymorphisms in AhR gene have been implicated in susceptibility to cancer. However, the results were controversial. This study was conducted to quantitatively summarize the association between AhR polymorphisms and cancer risk by meta-analysis. Methods Relevant reports were searched in four databases (Embase, PubMed, Wanfang, and China National Knowledge Infrastructure). We used pooled odds ratio (OR) and 95% confidence interval (95% CI) to evaluate the strength of the association in both standard and cumulative meta-analysis. Subgroup and sensitivity analysis was also performed, and between-study heterogeneity and publication bias were checked. Results A total of seventeen studies referring to three AhR polymorphisms (rs2066853, rs7796976, and rs2074113) were identified, and 9557 cases and 10038 controls were included. There was no statistically significant association of AhR rs2066853 polymorphism with cancer risk in the overall population, and the negative results were repeated in subgroup analysis by the ethnicity and cancer type. Concerning AhR rs7796976 or rs2074113 polymorphism, no significant correlation was detected. Moreover, these non-significant findings were stable in sensitivity analysis, and the cumulative meta-analysis indicated a trend of no significant link between this three AhR polymorphisms and cancer risk as more data accumulated over time. Conclusion This meta-analysis provides evidence that the rs2066853, rs7796976, or rs2074113 polymorphism in AhR gene is not a susceptible predictor of cancer. Further clinical and functional investigation between AhR polymorphisms and cancer susceptibility are needed.

R-sulforaphane modulates the expression profile of AhR, ERα, Nrf2, NQO1, and GSTP in human breast cell lines

Our previous study showed remarkable differences in the effect of R-sulforaphane (R-SFN) on the expression of CYPs 19, 1A1, 1A2, and 1B1 in ER(+) MCF7, ER( −) MDA-MB-231, and non-tumorigenic immortalized MCF10A (8). This study aimed to evaluate the effect of R-SFN on phase II enzymes induction and expression of AhR, Nrf2, and ERα in the same breast cell lines. The results showed increased expression of GSTP as a result of treatment with R-SFN in breast cancer cells. An increased NQO1 transcript and protein levels were found in all breast cells, with the most significant increase in MCF7 cells. Similarly, the enhancement of Nrf2 expression was noticed in all tested cells. AhR gene transcript and protein were decreased in MCF7 cells. In MDA-MB-231, increased AhR mRNA was not confirmed at the protein level. No differences were found in the expression of ERα. Overall, the results of the present study extended our earlier suggestions on the possible interference of R-SFN with estrogens homeostasis in breast cancer cells differing in ERα status, as well as in non-tumorigenic immortalized breast epithelial cells. While some of R-SFN effects might be beneficial and useful in breast cancer prevention, the others, particularly GSTP induction, may lead to adverse effects.

AhR and IDO1 in pathogenesis of Covid-19 and the “Systemic AhR Activation Syndrome:” a translational review and therapeutic perspectives

Covid-19 is the acute illness caused by SARS-CoV-2 with initial clinical symptoms such as cough, fever, malaise, headache, and anosmia. After entry into cells, corona viruses (CoV) activate aryl hydrocarbon receptors (AhRs) by an indoleamine 2,3-dioxygenase (IDO1)-independent mechanism, bypassing the IDO1-kynurenine-AhR pathway. The IDO1-kynurenine-AhR signaling pathway is used by multiple viral, microbial and parasitic pathogens to activate AhRs and to establish infections. AhRs enhance their own activity through an IDO1-AhR-IDO1 positive feedback loop prolonging activation induced by pathogens. Direct activation of AhRs by CoV induces immediate and simultaneous up-regulation of diverse AhR-dependent downstream effectors, and this, in turn, results in a “Systemic AhR Activation Syndrome” (SAAS) consisting of inflammation, thromboembolism, and fibrosis, culminating in multiple organ injuries, and death. Activation of AhRs by CoV may lead to diverse sets of phenotypic disease pictures depending on time after infection, overall state of health, hormonal balance, age, gender, comorbidities, but also diet and environmental factors modulating AhRs. We hypothesize that elimination of factors known to up-regulate AhRs, or implementation of measures known to down-regulate AhRs, should decrease severity of infection. Although therapies selectively down-regulating both AhR and IDO1 are currently lacking, medications in clinical use such as dexamethasone may down-regulate both AhR and IDO1 genes, as calcitriol/vitamin D3 may down-regulate the AhR gene, and tocopherol/vitamin E may down-regulate the IDO1 gene. Supplementation of calcitriol should therefore be subjected to epidemiological studies and tested in prospective trials for prevention of CoV infections, as should tocopherol, whereas dexamethasone could be tried in interventional trials. Because lack of physical exercise activates AhRs via the IDO1-kynurenine-AhR signaling pathway increasing risk of infection, physical exercise should be encouraged during quarantines and stay-at-home orders during pandemic outbreaks. Understanding which factors affect gene expression of both AhR and IDO1 may help in designing therapies to prevent and treat humans suffering from Covid-19.