Aryl hydrocarbon receptor signaling involved in the invasiveness of LNCaP cells

Risk of myeloproliferative neoplasms among U.S. Veterans from Korean, Vietnam, and Persian Gulf War eras

The Promise to Address Comprehensive Toxics (PACT) Act expanded U.S. Veterans' health care and benefits for conditions linked to service-connected exposures (e.g., Burn Pits, Agent Orange). However, myeloproliferative neoplasms (MPN) are not recognized as presumptive conditions for Veterans exposed to these toxic substances. This study evaluated the development of MPN among U.S. Veterans from the Korean, Vietnam, and Persian Gulf War eras. This retrospective cohort study included 65 425 Korean War era Veterans; 211 927 Vietnam War era Veterans; and 214 007 Persian Gulf War era Veterans from January 1, 2006, to January 26, 2023. Veterans with MPN, thrombosis, bleeding, and cardiovascular risk factors were identified through ICD-9 and -10 codes. Veterans from the Persian Gulf War era had the highest risk of developing MPN compared with Veterans from the Korean and Vietnam War eras, hazard ratio (HR) 4.92, 95% confidence interval (CI) 4.20-5.75 and HR 2.49, 95% CI 2.20-2.82, both p < .0001, respectively. Vietnam War era Veterans also had a higher risk of MPN development compared with Korean War era Veterans, HR 1.97, 95% CI 1.77-2.21, p < .0001. Persian Gulf War era Veterans were diagnosed with MPN at an earlier age, had higher risks of thrombosis and bleeding, and had lower survival rates compared with Korean War and Vietnam War era Veterans. This study reinforces evidence that environmental and occupational hazards increase the risk of clonal myeloid disorders and related complications, impacting overall survival with MPN. Limitations include the inability to confirm clonality and fully verify deployment and exposure status.

Aryl hydrocarbon receptor is a tumor promoter in MYCN-amplified neuroblastoma cells through suppression of differentiation

Neuroblastoma is the most common extracranial solid tumor in children. MYCN amplification is detected in almost half of high-risk cases and is associated with poorly differentiated tumors, poor patient prognosis and poor response to therapy, including retinoids. We identify the aryl hydrocarbon receptor (AhR) as a transcription factor promoting the growth and suppressing the differentiation of MYCN-amplified neuroblastoma. A neuroblastoma specific AhR transcriptional signature reveals an inverse correlation of AhR activity with patients' outcome, suggesting AhR activity is critical for disease progression. AhR modulates chromatin structures, reducing accessibility to regions responsive to retinoic acid. Genetic and pharmacological inhibition of AhR results in induction of differentiation. Importantly, AhR antagonism with clofazimine synergizes with retinoic acid in inducing differentiation both in vitro and in vivo. Thus, we propose AhR as a target for MYCN-amplified neuroblastoma and that its antagonism, combined with current standard-of-care, may result in a more durable response in patients.

When AHR signaling pathways meet viral infections

Aryl hydrocarbon receptor (AHR) is a ligand-dependent transcriptional factor widely expressed among immune, epithelial, endothelial and stromal cells in barrier tissues. It can be activated by small molecules provided by pollutants, microorganisms, food, and metabolism. It has been demonstrated that AHR plays an important role in modulating the response to many microbial pathogens, and the abnormal expression of AHR signaling pathways may disrupt endocrine, cause immunotoxicity, and even lead to the occurrence of cancer. Most humans are infected with at least one known human cancer virus. While the initial infection with these viruses does not cause major disease, the metabolic activity of infected cells changes, thus affecting the activation of oncogenic signaling pathways. In the past few years, lots of studies have shown that viral infections can affect disease progression by regulating the transmission of multiple signaling pathways. This review aims to discuss the potential effects of virus infections on AHR signaling pathways so that we may find a new strategy to minimize the adverse effects of the AHR pathway on diseases. Video Abstract.

The Kynurenine Pathway and Cancer: Why Keep It Simple When You Can Make It Complicated

Simple Summary

The kynurenine pathway has two main physiological roles: (i) it protects specific organs such as the eyes and placenta from strong immune reactions and (ii) it additionally generate in the liver and kidney a metabolite essential to all cells of human body. Abnormal activation of this pathway is recurrently observed in numerous cancer types. Its two functions are hijacked to promote tumor growth and cancer cell dissemination through multiple mechanisms. Clinical assays including administration of inhibitors of this pathway have not yet been successful. The complex regulation of this pathway is likely the reason behind this failure. In this review, we try to give an overview of the current knowledge about this pathway, to point out the next challenges, and to propose alternative therapeutic routes.

Abstract

The kynurenine pathway has been highlighted as a gatekeeper of immune-privileged sites through its ability to generate from tryptophan a set of immunosuppressive metabolic intermediates. It additionally constitutes an important source of cellular NAD⁺ for the organism. Hijacking of its immunosuppressive functions, as recurrently observed in multiple cancers, facilitates immune evasion and promotes tumor development. Based on these observations, researchers have focused on characterizing indoleamine 2,3-dioxygenase (IDO1), the main enzyme catalyzing the first and limiting step of the pathway, and on developing therapies targeting it. Unfortunately, clinical trials studying IDO1 inhibitors have thus far not met expectations, highlighting the need to unravel this complex signaling pathway further. Recent advances demonstrate that these metabolites additionally promote tumor growth, metastatic dissemination and chemoresistance by a combination of paracrine and autocrine effects. Production of NAD⁺ also contributes to cancer progression by providing cancer cells with enhanced plasticity, invasive properties and chemoresistance. A comprehensive survey of this complexity is challenging but necessary to achieve medical success.

LMP2A suppresses the role of AHR pathway through ERK signal pathway in EBV-associated gastric cancer

OBJECTIVE

To investigate the function of the aryl hydrocarbon receptor (AHR) pathway in Epstein-Barr Virus (EBV)-associated gastric cancer (EBVaGC) and to explore the relationship between EBV and AHR expression.

METHODS

The expression of AHR in EBVaGC and EBV negative GC (EBVnGC) tissues was detected by immunohistochemistry (IHC). Real-time qPCR (RT-qPCR) and Western blot analysis were used to examine the expression of AHR, cytochrome P450 1A1 (CYP1A1), and cytochrome P450 1B1 (CYP1B1) in gastric cancer cells. The cell proliferation and migration assay were tested by CCK8 and transwell analysis. EBV-encoded latent membrane protein 2A (LMP2A) was over-expressed in SGC7901 cells and silenced in AGS-EBV cells to further identify its role in EBV positive GC cells.

RESULTS

It was found that EBV infection inhibited the expression of AHR in gastric cancer tissues and cell lines. We also found that the activation of AHR pathway can promote cell proliferation and migration. However, the function was restricted in EBVaGC cell lines compared with EBVnGC. LMP2A can suppress AHR expression and pathway activation by activating phosphorylation of extracellular signal-regulated kinase (ERK) in EBV positive GC cell lines.

CONCLUSION

EBV-encoded LMP2A regulated the function of the AHR pathway by activating the ERK signal pathway in EBV positive GC cell lines.

How the AHR Became Important in Cancer: The Role of Chronically Active AHR in Cancer Aggression

For decades, the aryl hydrocarbon receptor (AHR) was studied for its role in environmental chemical toxicity i.e., as a quirk of nature and a mediator of unintended consequences of human pollution. During that period, it was not certain that the AHR had a “normal” physiological function. However, the ongoing accumulation of data from an ever-expanding variety of studies on cancer, cancer immunity, autoimmunity, organ development, and other areas bears witness to a staggering array of AHR-controlled normal and pathological activities. The objective of this review is to discuss how the AHR has gone from a likely contributor to genotoxic environmental carcinogen-induced cancer to a master regulator of malignant cell progression and cancer aggression. Particular focus is placed on the association between AHR activity and poor cancer outcomes, feedback loops that control chronic AHR activity in cancer, and the role of chronically active AHR in driving cancer cell invasion, migration, cancer stem cell characteristics, and survival.

Aryl Hydrocarbon Receptor: Its Regulation and Roles in Transformation and Tumorigenesis

AhR is an environmental response gene that mediates cellular responses to a variety of xenobiotic compounds that frequently function as AhR ligands. Many AhR ligands are classified as carcinogens or pro-carcinogens. Thus, AhR itself acts as a major mediator of the carcinogenic effect of many xenobiotics in vivo. In this concise review, mechanisms by which AhR trans-activates downstream target gene expression, modulates immune responses, and mediates malignant transformation and tumor development are discussed. Moreover, activation of AhR by post-translational modifications and crosstalk with other transcription factors or signaling pathways are also summarized.

Phthalate exposure and prostate cancer in a population-based nested case-control study

BACKGROUND

Phthalic acid esters are established as endocrine disruptors. The study aimed to evaluate the association between urinary phthalate metabolites and prostate cancer occurrence.

METHODS

The study was based on the Taiwan Community-Based Cancer Screening Program, which was set up in 1991-1992 and followed periodically. By 2010, 80 incident prostate cancer cases were identified in the 12,020 men. For each case, 2 controls were randomly selected, matched by age (±3 years), urine collection date (±3 months), and residential township. Frequently used phthalate metabolites from the urine samples were quantified by liquid chromatography/electrospray ionization tandem mass spectrometry. Logistic regression was conducted to assess the association between the exposure levels and prostate cancer occurrence.

RESULTS

Exposure to di (2-ethylhexyl), butyl-benzyl and di-isobutyl phthalates (DEHP, BBzP, DiBP) was positively associated with prostate cancer in men with waist circumference (WC) ≥90 cm but not in the leans. Odds ratio for the DEHP metabolite summary score (upper tertile compared to the rest) and prostate cancer were 7.76 (95% CI = 1.95-30.9) for WC ≥ 90 cm.

CONCLUSIONS

DEHP, BBzP, and DiBP exposure were associated with prostate cancer occurrence in abdominally obese men. The main limitation remains the lack of mechanistic experiments and comparable toxicological data.

[Aryl-hydrocarbon receptor as a potential target for anticancer therapy]

Aryl-hydrocarbon receptor (Aryl Hydrocarbon Receptor, AHR) is a ligand-dependent transcription factor, whose functions are related to xenobiotic detoxification, response to inflammation, and maintenance of tissue homeostasis. Recent investigations suggest that AHR also plays an important role in the processes of carcinogenesis. Increased expression of AHR is observed in several types of tumors and tumor cell lines. In addition, it turned out that the composition of pharmaceutical drugs used in oncotherapy includes some ligands AHR. These facts allow us to consider an aryl-hydrocarbon receptor as a potential target for anticancer therapy, especially for the treatment of severe cancers whose treatment options are very limited or do not exist at all. In this review the examples of AHR ligands' effect on tumor cell cultures and on model mice lines with AHR-dependent response are discussed.

Inhibition of the aryl hydrocarbon receptor/polyamine biosynthesis axis suppresses multiple myeloma

Polyamine inhibition for cancer therapy is, conceptually, an attractive approach but has yet to meet success in the clinical setting. The aryl hydrocarbon receptor (AHR) is the central transcriptional regulator of the xenobiotic response. Our study revealed that AHR also positively regulates intracellular polyamine production via direct transcriptional activation of 2 genes, ODC1 and AZIN1, which are involved in polyamine biosynthesis and control, respectively. In patients with multiple myeloma (MM), AHR levels were inversely correlated with survival, suggesting that AHR inhibition may be beneficial for the treatment of this disease. We identified clofazimine (CLF), an FDA-approved anti-leprosy drug, as a potent AHR antagonist and a suppressor of polyamine biosynthesis. Experiments in a transgenic model of MM (Vk*Myc mice) and in immunocompromised mice bearing MM cell xenografts revealed high efficacy of CLF comparable to that of bortezomib, a first-in-class proteasome inhibitor used for the treatment of MM. This study identifies a previously unrecognized regulatory axis between AHR and polyamine metabolism and reveals CLF as an inhibitor of AHR and a potentially clinically relevant anti-MM agent.