Aryl Hydrocarbon Receptor Research Articles

Combination screen in multi-cell type tumor spheroids reveals interaction between aryl hydrocarbon receptor antagonists and E1 ubiquitin-activating enzyme inhibitor

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that regulates genes of drug transporters and metabolic enzymes to detoxify small molecule xenobiotics. It has a complex role in cancer biology, influencing both the progression and suppression of tumors by modulating malignant properties of tumor cells and anti-tumor immunity, depending on the specific tumor type and developmental stage. This has led to the discovery and development of selective AhR modulators, including BAY 2416964 which is currently in clinical trials. To identify small molecule anticancer agents that might be combined with AhR antagonists for cancer therapy, a high-throughput combination screen was performed using multi-cell type tumor spheroids grown from malignant cells, endothelial cells, and mesenchymal stem cells. The AhR selective antagonists BAY 2416964, GNF351, and CH-223191 were tested individually and in combination with twenty-five small molecule anticancer agents. As single agents, BAY 2416964 and CH-223191 showed minimal activity, whereas GNF351 reduced the viability of some spheroid models at concentrations greater than 1 µM. The activity of most combinations aligned well with the single agent activity of the combined agent, without apparent contributions from the AhR antagonist. All three AhR antagonists sensitized tumor spheroids to TAK-243, an E1 ubiquitin-activating enzyme inhibitor. These combinations were active in spheroids containing bladder, breast, ovary, kidney, pancreas, colon, and lung tumor cell lines. The AhR antagonists also potentiated pevonedistat, a selective inhibitor of the NEDD8-activating enzyme E1 regulatory subunit, in several tumor spheroid models. In contrast, the AhR antagonists did not enhance the cytotoxicity of the proteasome inhibitor bortezomib.

Discovery of a novel AhR–CYP1A1 axis activator for mitigating inflammatory diseases using an in situ functional imaging assay

The aryl hydrocarbon receptor (AhR) plays a crucial role in regulating many physiological processes. Activating the AhR–CYP1A1 axis has emerged as a novel therapeutic strategy against various inflammatory diseases. Here, a practical in situ cell-based fluorometric assay was constructed to screen AhR-CYP1A1 axis modulators, via functional sensing of CYP1A1 activities in live cells. Firstly, a cell-permeable, isoform-specific enzyme-activable fluorogenic substrate for CYP1A1 was rationally constructed for in-situ visualizing the dynamic changes of CYP1A1 function in living systems, which was subsequently used for discovering the efficacious modulators of the AhR–CYP1A1 axis. Following screening of a compound library, LAC-7 was identified as an efficacious activator of the AhR–CYP1A1 axis, which dose-dependently up-regulated the expression levels of both CYP1A1 and AhR in multiple cell lines. LAC-7 also suppressed macrophage M1 polarization and reduced the levels of inflammatory factors in LPS-induced bone marrow-derived macrophages. Animal tests showed that LAC-7 could significantly mitigate DSS-induced ulcerative colitis and LPS-induced acute lung injury in mice, and markedly reduced the levels of multiple inflammatory factors. Collectively, an optimized fluorometric cell-based assay was devised for in situ functional imaging of CYP1A1 activities in living systems, which strongly facilitated the discovery of efficacious modulators of the AhR–CYP1A1 axis as novel anti-inflammatory agents.

Coexposure to microplastic and Bisphenol A exhacerbates damage to human kidney proximal tubular cells

Microplastics (MPs) accumulate in tissues, including kidney tissue, while Bisphenol A (BPA) is a plasticizer of particular concern. At present, the combined effects of MPs and BPA are unexplored in human renal cells. Therefore, we exposed a proximal tubular cell line (PTECs) to polyethylene (PE)-MPs and BPA, both separately and in combination. When co-exposed, cells showed a significantly reduced cell viability (MTT test) and a pronounced pro-oxidant (MDA levels, NRF2 and NOX4 expression by Western blot) and pro-inflammatory response (IL1β, CCL/CCR2 and CCL/CCR5 mRNAs by RT-PCR), compared to those treated with a single compound. In addition, heat shock protein (HSP90), a chaperone involved in multiple cellular functions, was reduced (by Western Blot and immunocytochemistry), while aryl hydrocarbon receptor (AHR) expression, a transcription factor which binds environmental ligands, was increased (RT-PCR and immunofluorescence). Our research can contribute to the study of the nephrotoxic effects of pollutants and MPs and shed new light on the combined effects of BPA and PE-MPs.

Nicotine promotes pathogenic bacterial growth and biofilm formation in peri-implant.

Introduction. Peri-implantitis is a plaque-associated disease that leads to implant loss and arises from bacterial biofilms on the surface of the implant. Smoking is a risk factor for peri-implantitis and impedes treatment effectiveness. Additionally, aryl hydrocarbon receptor (AHR), IL-6, and IL-22 levels are related to peri-implantitis.Aim. We aimed to investigate the effects of nicotine on inflammatory response, bacterial growth and biofilm formation.Hypothesis/Gap Statement. We hypothesized that nicotine promoted pathogenic bacterial growth and biofilm formation, thereby aggravating inflammation.Methodology. The expression of AHR, IL-6 and IL-22 was measured in peri-implant sulci fluid using quantitative PCR and Western blot analyses. The cementum was incubated with bacterial suspension including Porphyromonas gingivalis, Streptococcus sanguinis and Fusobacterium nucleatum and treated with 100, 200, 250 and 300 µg ml-1 nicotine, and then, the absorbance and number of colony-forming units were detected. Biofilm formation was evaluated using the tissue culture plate method and safranin O staining. Carbohydrates and proteins were measured by the phenol-sulfuric acid method and the bicinchoninic acid method, respectively.Results. The results indicated that smoking increased the levels of AHR, IL-6 and IL-22. Functionally, nicotine promoted the growth of P. gingivalis, S. sanguinis and F. nucleatum. Additionally, it promoted the biofilm formation of these bacteria and increased the contents of carbohydrates and proteins.Conclusion. Nicotine promoted bacterial growth and biofilm build-up, suggesting that smoking may aggravate the progression of peri-implantitis.

Putting advanced materials to the test: Ti3C2 MXenes alleviate the hazardous effects of the environmental pollutant benzo[a]pyrene

Advanced materials are materials that have been engineered to exhibit novel or enhanced properties that confer superior performance when compared to conventional materials. Here, we evaluated the impact of Ti3C2 MXenes, a two-dimensional (2D) material, on the adverse effects caused by polycyclic aromatic hydrocarbons. To this end, we studied benzo[a]pyrene denoted here as B[a]P as a model compound. B[a]P was found to adsorb to MXenes as evidenced by UV–Vis spectroscopy. MXenes in the presence or absence of natural organic matter (NOM) were well tolerated by zebrafish embryos. The uptake (ingestion) of MXenes by zebrafish was determined by quantifying the Ti content using inductively coupled plasma mass spectrometry (ICP-MS) while Raman confocal mapping was applied for the label-free identification of MXenes in situ in exposed zebrafish. The body burden of B[a]P was determined by gas chromatography-mass spectrometry (GC-MS). The potential impact of MXenes on B[a]P triggered aryl hydrocarbon receptor (AhR) induction was assessed by evaluating the induction of downstream genes including cyp1a, and results were validated by using the transgenic zebrafish reporter tg(cyp1a-eGFP). The potential impact of MXenes on the genotoxicity caused by B[a]P was also assessed. MXenes were shown to ameliorate AhR induction and DNA damage caused by B[a]P. This was corroborated by using the human colon-derived cell line HT-29. Taken together, MXenes were found to be non-hazardous and alleviated the adverse effects caused by B[a]P in vitro and in vivo.

Activation of Aryl Hydrocarbon Receptor by an Indolic Uremic Toxin Increases the Risk of Deep Venous Thrombosis

Activation of Aryl Hydrocarbon Receptor by an Indolic Uremic Toxin Increases the Risk of Deep Venous Thrombosis

Ineffectiveness of 6,2',4'-trimethoxyflavone in mitigating cerebral ischemia/reperfusion injury after post-reperfusion administration in rats.

Pharmacological inhibition of aryl hydrocarbon receptor (AhR) activation after ischemia alleviates cerebral ischemia/reperfusion (IR) injury. To investigate whether AhR antagonist administration after reperfusion was also effective in attenuating cerebral IR injury. A total of 24 Sprague-Dawley rats were divided into the sham-operated group (no IR), control group (IR), and 6,2',4'-trimethoxyflavone (TMF) group (IR + TMF administration), with 10 rats assigned to each group. Cerebral IR injury was induced by 60 min of middle cerebral artery occlusion followed by reperfusion. TMF (5 mg/kg) was used as the AhR antagonist and was administered intraperitoneally immediately after reperfusion. Cerebral IR injury was observed using magnetic resonance imaging (MRI) and neurobehavioral assessments at baseline, immediately after ischemia, and at 3 days after ischemia. On MRI, the TMF group showed no significant differences in relative apparent diffusion coefficient (ADC), T2, and fractional anisotropy (FA) values; midline shift value; and infarct volume. In terms of neurobehavioral function, factors such as grip strength, contralateral forelimb use, time to touch, and time to remove adhesive tape from the forepaw, were also not significantly different between the control and TMF groups. This study demonstrated that AhR treatment after reperfusion had no noticeable effect on reducing cerebral IR injury in rats.

Benzo[a]pyrene: A carcinogen, its sources, adverse effects, and preventive measures

A polycyclic aromatic hydrocarbon called benzo[a]pyrene (B[a]P) is produced during incomplete burning of fuels. The most common way humans consume B[a]P is through food products, particularly grilled or smoked foods. B[a]P is also frequently detected in the sediments, soil, surface water, and air. Once bioactivated, it produces a highly reactive epoxide monomer that can create adducts by chemically reacting with biological molecules, such as DNA. B[a]P is implicated in various cancers due to its interaction with the aromatic hydrocarbon receptor (AhR). Apart from its detrimental impacts on development and reproduction, this substance also suppresses the immune system. Microbes, however, are critical to cleaning up the B[a]P-contaminated environment. This review focuses on forming B[a]P in different compartments of the environment and human surroundings, and the mechanisms responsible for its harmful effects and carcinogenic risk. This review also discusses the strategies for the deterioration of B[a]P.

Diagnosis and management of pituitary adenomas in children and adolescents.

Pituitary adenomas (PAs)-also now called pituitary neuroendocrine tumours or Pit-NETS-are rare in children and adolescents and exceptional below the age of 10. Most evidence-based high-quality data are derived from larger studies in adult patients. We will review recent knowledge on the epidemiology, clinical features, diagnosis, and treatment modalities of the different types of pituitary adenomas diagnosed in children and adolescents, emphasizing the many reasons why these cases should be discussed within pituitary-specific multidisciplinary teams with experts from both paediatric and adult practice. Paediatric PA presents multiple peculiarities that may challenge their adequate management. They are overall proportionally larger and more aggressive than in adults, with potential mass effects including hypopituitarism. Hormonal hypersecretion is frequent, resulting in clinical syndromes affecting normal growth and pubertal development. Prolactinomas represent the most frequent subtype of PA found during childhood, followed by adrenocorticotropin (ACTH) and growth hormone (GH)-secreting adenomas, while clinically non-functioning adenomas are exceptionally diagnosed before the age of 16. The occurrence of a pituitary tumour in a young individual should also prompt genetic testing in each case, searching for either germline mutations in one of the known genes that may drive inherited/familial PA (such as the multiple endocrine neoplasia type 1 or MEN1 gene, or the aryl hydrocarbon receptor interacting protein or AIP gene), or for a mosaic activating mutation of GNAS as found in the McCune-Albright syndrome.

Molecular Interactions Governing the Rat Aryl Hydrocarbon Receptor Activities of Polycyclic Aromatic Compounds and Predictive Model Development.

Polycyclic aromatic compounds (PACs) exhibit rat aryl hydrocarbon receptor (rAhR) activities, leading to diverse biological or toxic effects. In this study, the key amino residues and molecular interactions that govern the rAhR activity of PACs were investigated using in silico strategies. The homology model of rAhR was first docked with 90 PACs to yield complexes, and the results of the molecular dynamics simulations of 16 typical complexes showed that the binding energies of the complexes range from -7.37 to -26.39 kcal/mol. The major contribution to the molecular interaction comes from van der Waals forces, and Pro295 and Arg316 become the key residues involved in most complexes. Two QSAR models were further developed to predict the rAhR activity of PACs (in terms of log IEQ for PACs without halogen substitutions and log%-TCDD-max for halogenated PACs). Both models have good predictive ability, robustness, and extrapolation ability. Molecular polarizability, electronegativity, size, and nucleophilicity are identified as the important factors affecting the rAhR activity of PACs. The developed models could be employed to predict the rAhR activity of other reactive PACs. This work provides insight into the mechanisms and interactions of the rAhR activity of PACs and assists in the assessment of their fate and risk in organisms.

Introduction of MYBL2 as a common regulator between AHR and RELA: Its relationship with lnc-UCC and lnc-HOTTIP in glioblastoma multiforme

This study aimed to validate the experimental gene expression level of a common gene in the Aryl Hydrocarbon Receptor (AHR) and RELA in glioblastoma multiforme (GBM) using bioinformatics.RNAseq data was analyzed to identify differentially expressed genes (DEGs), and LncRNAs related to the regulation of the founded gene were identified by the RNA Interactome Database. Ten healthy controls and 28 GBM patients' tissue samples were gathered, and the change in gene expression levels was measured by real-time PCR.The results showed that MYBL2 is a common regulator between the AHR and RELA, and the expression of MYBL2, lnc-UCC, and lnc-HOTTIP genes was significantly increased in the GBM group.Lnc-UCC expression showed significant positive correlations with MYBL2 and lnc-HOTTIP expression levels. Further investigation into these genes and their regulatory mechanisms is need.

Bmal1 upregulates ATG5 expression to promote autophagy in skin cutaneous melanoma

BackgroundSkin cutaneous melanoma (SKCM) is a highly aggressive and malignant tumor that arises from the malignant transformation of melanocytes. In light of the limitations of existing treatment modalities, there is a pressing need to identify new drug targets for SKCM. Aryl-hydrocarbon receptor nuclear translocator-like (ARNTL), also known as Bmal1, is a gene that has been linked to the onset and progression of cancer. However, its role in SKCM remains understudied. MethodsThe expression of Bmal1 mRNA and protein was detected using TCGA, GTEx, CCLE, and ULCAN databases. Moreover, survival analysis was performed to investigate the association between Bmal1 and immune invasion and gene expression in immune infiltrating cells via CIBERSORT, R programming, TIMER, Sangerbox, Kaplan-Meier. The study also explored the role of proteins associated with Bmal1 by using R programming and databases (STRING and GSEA). Both in vitro and in vivo studies were conducted to examine the potential role of Bmal1 in SKCM. ResultsCompared to normal tissues, the expression level of Bmal1 was significantly reduced in SKCM. Which has been associated with its poor prognosis. Similarly, its expression in SKCM was substantially correlated with immune infiltration, while biogenic analysis indicated that it could potentially influence the tumor immune microenvironment (TME) by influencing tumor-associated neutrophils (TANs). Moreover, Bmal1 overexpression suppressed the proliferation and invasion of melanoma cells and enhanced apoptosis, migration, and cell colony formation. ConclusionThis study concluded that Bmal1 is a novel biomarker that functions as both a diagnostic and prognostic indicator for the progression of SKCM.

UA influences the progression of breast cancer via the AhR/p27Kip1/cyclin E pathway.

Uric acid (UA) is the end product of purine metabolism. In recent years, UA has been found to be associated with the prognosis of clinical cancer patients. However, the intricate mechanisms by which UA affects the development and prognosis of tumor patients has not been well elucidated. In this study, we explored the role of UA in breast cancer, scrutinizing its impact on breast cancer cell function by treating two types of breast cancer cell lines with UA. The role of UA in the cell cycle and proliferation of tumors and the underlying mechanisms were further investigated. We found that the antioxidant effect of UA facilitated the scavenging of reactive oxygen species (ROS) in breast cancer, thereby reducing aryl hydrocarbon receptor (AhR) expression and affecting the breast cancer cell cycle, driving the proliferation of breast cancer cells through the AhR/p27Kip1/cyclin E1 pathway. Moreover, in breast cancer patients, the expression of AhR and its downstream genes may be closely associated with cancer progression in patients. Therefore, an increase in UA could promote the proliferation of breast cancer cells through the AhR/p27Kip1/cyclin E1 pathway axis.

Molecular Insights into the Interaction of Tryptophan Metabolites with the Human Aryl Hydrocarbon Receptor in Silico: Tryptophan as Antagonist and no Direct Involvement of Kynurenine.

A direct link between the tryptophan (Trp) metabolite kynurenine (Kyn) and the aryl hydrocarbon receptor (AhR) is not supported by metabolic considerations and by studies demonstrating the failure of Kyn concentrations of up to 100 μM to activate the receptor in cell culture systems using the proxy system of cytochrome P-450-dependent metabolism. The Kyn metabolite kynurenic acid (KA) activates the AhR and may mediate the Kyn link. Recent studies demonstrated down regulation and antagonism of activation of the AhR by Trp. We have addressed the link between Kyn and the AhR by looking at their direct molecular interaction in silico. Molecular docking of Kyn, KA, Trp and a range of Trp metabolites to the crystal structure of the human AhR was performed under appropriate docking conditions. Trp and 30 of its metabolites docked to the AhR to various degrees, whereas Kyn and 3-hydroxykynurenine did not. The strongest docking was observed with the Trp metabolite and photooxidation product 6-Formylindolo[3,2-b]carbazole (FICZ), cinnabarinic acid, 5-hydroxytryptophan, N-acetyl serotonin and indol-3-yllactic acid. Strong docking was also observed with other 5-hydroxyindoles. We propose that the Kyn-AhR link is mediated by KA. The strong docking of Trp and its recently reported down regulation of the receptor suggest that Trp is an AhR antagonist and may thus play important roles in body homeostasis beyond known properties or simply being the precursor of biologically active metabolites. Differences in AhR activation reported in the literature are discussed.

Eucalyptus Wood Smoke Extract Elicits a Dose-Dependent Effect in Brain Endothelial Cells

The frequency, duration, and size of wildfires have been increasing, and the inhalation of wildfire smoke particles poses a significant risk to human health. Epidemiological studies have shown that wildfire smoke exposure is positively associated with cognitive and neurological dysfunctions. However, there is a significant gap in knowledge on how wildfire smoke exposure can affect the blood–brain barrier and cause molecular and cellular changes in the brain. Our study aims to determine the acute effect of smoldering eucalyptus wood smoke extract (WSE) on brain endothelial cells for potential neurotoxicity in vitro. Primary human brain microvascular endothelial cells (HBMEC) and immortalized human brain endothelial cell line (hCMEC/D3) were treated with different doses of WSE for 24 h. WSE treatment resulted in a dose-dependent increase in IL-8 in both HBMEC and hCMEC/D3. RNA-seq analyses showed a dose-dependent upregulation of genes involved in aryl hydrocarbon receptor (AhR) and nuclear factor erythroid 2-related factor 2 (NRF2) pathways and a decrease in tight junction markers in both HBMEC and hCMEC/D3. When comparing untreated controls, RNA-seq analyses showed that HBMEC have a higher expression of tight junction markers compared to hCMEC/D3. In summary, our study found that 24 h WSE treatment increases IL-8 production dose-dependently and decreases tight junction markers in both HBMEC and hCMEC/D3 that may be mediated through the AhR and NRF2 pathways, and HBMEC could be a better in vitro model for studying the effect of wood smoke extract or particles on brain endothelial cells.

PARP7 Inhibitors and AHR Agonists Act Synergistically Across a Wide-Range of Cancer Models.

Small molecule inhibitors of the mono (ADP) ribosyl transferase PARP7 are being evaluated as a monotherapy for tumors overexpressing PARP7 and in combination with immune checkpoint blockade. We previously showed that sensitivity to the PARP7 inhibitor (PARP7i) RBN-2397 could be enhanced by co-treatment with agonists of the Aryl Hydrocarbon Receptor (AHRa) in cell lines that show strong intrinsic sensitivity to RBN-2397. Here we demonstrate that a range of tumor cell lines that are relatively insensitive to PARP7i or AHRa as individual agents are unexpectedly profoundly sensitive to the combination. Our data show that this synergistic response is dependent on AHR/ARNT and is associated with increased levels of nuclear AHR and increased transcription of AHR target genes. In some hormone receptor-positive cell lines, we find that combination treatment is associated with proteasomal turnover of the steroid hormone receptors, androgen receptor and estrogen receptor. Both wildtype and hormone-resistant mutant forms of these receptors are degraded upon treatment with AHRa and PARP7i in breast and prostate cancer models. These results suggest that combining PARP7i with AHRa may extend the utility of these drugs to a wider range of tumors, including those that are refractory to hormone therapy.

The Kynurenine Pathway, Aryl Hydrocarbon Receptor, and Alzheimer's Disease.

Alzheimer's disease (AD) is the leading cause of dementia, mainly affecting elderly individuals. AD is characterized by β-amyloid plaques, abnormal tau tangles, neuronal loss, and metabolic disruptions. Recent studies have revealed the involvement of the kynurenine (KP) pathway and the aryl hydrocarbon receptor (AhR) in AD development. The KP pathway metabolizes tryptophan to produce neuroactive substances like kynurenine, kynurenic acid, and quinolinic acid. In AD, high levels of kynurenine and the neurotoxic quinolinic acid are associated with increased neuroinflammation and excitotoxicity; conversely, reduced levels of kynurenic acid, which acts as a glutamate receptor antagonist, compromise neuroprotection. Research has indicated elevated KP metabolites and enzymes in the hippocampus of AD patients and other tissues such as blood, cerebrospinal fluid, and urine. However, the finding that KP metabolites are AD biomarkers in blood, cerebrospinal fluid, and urine has been controversial. This controversy, stemming from the lack of consideration of the specific stage of AD, details of the patient's treatment, cognitive deficits, and psychiatric comorbidities, underscores the need for more comprehensive research. AhR, a ligand-activated transcription factor, regulates immune response, oxidative stress, and xenobiotic metabolism. Various ligands, including tryptophan metabolites, can activate it. Some studies suggest that AhR activation contributes to AD, while others propose that it provides neuroprotection. This discrepancy may be explained by the specific ligands that activate AhR, highlighting the complex relationship between the KP pathway, AhR activation, and AD, where the same pathway can produce both neuroprotective and harmful effects.

Involvement of Intestinal Epithelium Aryl Hydrocarbon Receptor Expression and 3, 3'-Diindolylmethane in Colonic Tertiary Lymphoid Tissue Formation.

Tertiary lymphoid tissues (TLTs) are adaptive immune structures that develop during chronic inflammation and may worsen or lessen disease outcomes in a context-specific manner. Immune cell activity governing TLT formation in the intestines is dependent on immune cell aryl hydrocarbon receptor (AhR) activation. Homeostatic immune cell activity in the intestines is further dependent on ligand activation of AhR in intestinal epithelial cells (IECs), yet whether AhR activation and signaling in IECs influences the formation of TLTs in the presence of dietary AhR ligands is not known. To this end, we used IEC-specific AhR deletion coupled with a mouse model of dextran sodium sulfate (DSS)-induced colitis to understand how dietary AhR ligand 3, 3'-diindolylmethane (DIM) influenced TLT formation. DIM consumption increased the size of TLTs and decreased T-cell aggregation to TLT sites in an IEC-specific manner. In DSS-exposed female mice, DIM consumption increased the expression of genes implicated in TLT formation (Interleukin-22, Il-22; CXC motif chemokine ligand 13, CXCL13) in an IEC AhR-specific manner. Conversely, in female mice without DSS exposure, DIM significantly reduced the expression of Il-22 or CXCL13 in iAhRKO mice, but this effect was not observed in WT animals. Our findings suggest that DIM affects the immunological landscape of TLT formation during DSS-induced colitis in a manner contingent on AhR expression in IECs and biological sex. Further investigations into specific immune cell activity, IEC-specific AhR signaling pathways, and dietary AhR ligand-mediated effects on TLT formation are warranted.

Abstract C167: Understanding the effect of single nucleotide polymorphism rs2292596 on the interaction of aryl hydrocarbon receptor repressor and aryl hydrocarbon receptor nuclear translocator

Abstract Lung cancer is the leading cause of cancer death in America. Additionally, the incident rates among Black/African American (B/AA) men and women are significantly higher than those of their white counterparts, despite B/AA’s lower exposure to cigarette smoke (Berg et al, 2010. Journal of Pharmacology and Experimental Therapeutics, Vol. 332, p202). One factor that may increase the risk of lung adenocarcinoma in B/AA individuals is a single nucleotide polymorphism (SNP) found in the aryl hydrocarbon receptor repressor (AHRR) gene. To date, this SNP has been poorly studied, particularly in B/AA individuals. As its name suggests, AHRR represses the detoxification of tobacco smoke induced by aryl hydrocarbon receptor (AHR). Upon exposure to tobacco smoke, AHR enters the nucleus where it dimerizes with aryl hydrocarbon receptor nuclear translocator (ARNT) and binds to xenobiotic response elements (XREs), thereby inducing the genes mediating the detoxification process. Simultaneously, AHRR is turned on as part of a negative feedback loop. AHRR down-regulates the detoxification process by binding to ARNT, forming a negative regulatory complex that binds to XREs. Within the region of AHRR that encodes for the ARNT interaction domain, a single nucleotide polymorphism (SNP) is found in exon 6. SNP rs2292596 encodes a proline or alanine, with 63% of the White subjects having proline while 89% of the B/AA subjects have proline (Single Nucleotide Polymorphism Database, NCBI). As proline is a turn-inducing amino acid, this change, residing in one of the AHRR loops that encircles ARNT, may affect the kinetics of AHRR/ARNT complex association and/or dissociation, thereby potentially affecting the regulatory balance of detoxification. We are currently synthesizing recombinant AHRR protein containing the two different amino acids, along with ARNT. To assess how these changes in the amino acid sequence affect the interaction of AHRR and ARNT, we will measure the association and dissociation rates using a SwitchSense DRX2 instrument. If the SNP affects the kinetics of AHRR/ARNT heterodimer formation, it may affect detoxification and thereby lung cancer risk. If so, in the future the accuracy of lung cancer detection may be improved by increased screening for individuals carrying the risk allele. Furthermore, if the presence of the risk allele implicates a higher risk for lung cancer, this may strengthen lung cancer prevention within the B/AA community. Funding: This research is supported by R21CA290319 from National Institute of Health (NIH)/National Cancer Institute (NCI), the Norris Comprehensive Cancer Center core grant, award number P30CA014089 from the NIH/NCI, and by the Undergraduate Research Associates Program supported by the USC Provost. Citation Format: Shiori Fukutome, Matthew A. Gladstone, Chunli Yan, Diego A. Velarde, Nicholas Mancuso, Ite Offringa. Understanding the effect of single nucleotide polymorphism rs2292596 on the interaction of aryl hydrocarbon receptor repressor and aryl hydrocarbon receptor nuclear translocator [abstract]. In: Proceedings of the 17th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2024 Sep 21-24; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2024;33(9 Suppl):Abstract nr C167.

Abstract C049: Aryl hydrocarbon receptor activity promotes cancer progression and drug resistance in castration-resistant prostate cancer cells

Abstract The aryl hydrocarbon receptor (AhR) is a nuclear transcription factor, xenobiotic sensor, and has a role in regulating diet-induced obesity. We report constitutive overexpression and activity of AhR promotes progression to androgen independence, proliferation, and mediates drug resistance in metastatic castration-resistant prostate cancer (CRPC) in vitro models. RNAseq analysis identified differentially expressed genes (DEGS) which may further implicate the role of AhR in prostate cancer progression. Recent evidence demonstrates significant changes in the expression profile of these genes in response to treatment with chemotherapeutics, specifically bromocriptine (Wu et al 2023). We also confirmed AhR inhibits drug-induced apoptosis in C4-2 cells. Further understanding of the molecular mechanisms governing AhR-mediated cancer progression and drug resistance should expand treatment options and improve patient outcomes. Citation Format: Kofi K. Khamit-Kush, Nathan J. Bowen, Jeffrey A. Handy, Joann B. Powell. Aryl hydrocarbon receptor activity promotes cancer progression and drug resistance in castration-resistant prostate cancer cells [abstract]. In: Proceedings of the 17th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2024 Sep 21-24; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2024;33(9 Suppl):Abstract nr C049.