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A putative role for the aryl hydrocarbon receptor (AHR) gene in a patient with cyclical Cushing's disease.

ABSTRACT: BACKGROUND:Apart from PRKAR1A mutations in a subset of cyclical Cushing's syndrome due to primary pigmented nodular adrenocortical disease, the molecular basis of cyclical Cushing's syndrome has not been investigated. We speculated that cyclical Cushing's syndrome may be due to mutations in the clock genes that govern circadian rhythms, including the hypothalamic-pituitary-adrenal axis. CASE PRESENTATION:A 47-year-old man presented with mass effects from a sellar lesion. He was ultimately diagnosed with cyclical Cushing's disease due to a giant corticotrophinoma. We performed whole exome sequencing of germline and tumour DNA, SNP array of tumour DNA and tumour immunohistochemistry in order to detect variants in candidate circadian/pituitary-associated genes. We identified a rare germline missense variant in the aryl hydrocarbon receptor (AHR) gene, which has previously been indirectly linked to pituitary tumorigenesis and clock system disruption. The AHR variant was found in a highly conserved site involved in phosphorylation. It was predicted to be damaging by multiple in silico tools and AHR tumour immunohistochemistry demonstrated loss of the normal nuclear staining pattern, suggestive of an inactivating mutation. We also found a novel, damaging germline missense variant in the retinoid X receptor gamma (RXRG) gene, multiple somatic chromosomal gains (including AHR), and a somatic mutational signature consistent with oncogenesis that may have acted synergistically with the AHR variant. CONCLUSIONS:This is the first report of an AHR variant with predicted pathogenicity in the pituitary adenoma setting. Our preliminary data suggest that the highly conserved AHR gene may represent a link between pituitary tumorigenesis, the hypothalamic-pituitary-adrenal axis and the clock system. Further research may indicate a role for the gene in the development of cyclical Cushing's disease.

SUBMITTER: De Sousa SMC

PROVIDER: S-EPMC6988286 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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A putative role for the aryl hydrocarbon receptor (AHR) gene in a patient with cyclical Cushing's disease.

De Sousa Sunita M C SMC Manavis Jim J Feng Jinghua J Wang Paul P Schreiber Andreas W AW Scott Hamish S HS Torpy David J DJ

BMC endocrine disorders 20200129 1

<h4>Background</h4>Apart from PRKAR1A mutations in a subset of cyclical Cushing's syndrome due to primary pigmented nodular adrenocortical disease, the molecular basis of cyclical Cushing's syndrome has not been investigated. We speculated that cyclical Cushing's syndrome may be due to mutations in the clock genes that govern circadian rhythms, including the hypothalamic-pituitary-adrenal axis.<h4>Case presentation</h4>A 47-year-old man presented with mass effects from a sellar lesion. He was ul ...[more]

PMID: 31996203

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Project description:BackgroundCentrosome aberrations can cause genomic instability and correlate with malignant progression in common human malignancies such as breast and prostate cancer. Deregulation of cyclin/cyclin-dependent kinase 2 (CDK2) activity has previously been shown to be critically involved in centrosome overduplication. We therefore test here whether small molecule CDK inhibitors derived from the bis-indole indirubin can be used to suppress centrosome aberrations as a novel approach to chemoprevention of malignant progression.ResultsAs expected, we found that the CDK inhibitor indirubin-3'-oxime (IO) suppresses centrosome amplification in breast cancer cells. However, we made the unexpected discovery that indirubin-derived compounds that have been chemically modified to be inactive as kinase inhibitors such as 1-methyl-indirubin-3'-oxime (MeIO) still significantly reduced centrosome amplification. All indirubins used in the present study are potent agonists of the aryl hydrocarbon receptor (AhR), which is known for its important role in the cellular metabolism of xenobiotics. To corroborate our results, we first show that the coincidence of nuclear AhR overexpression, reflecting a constitutive activation, and numerical centrosome aberrations correlates significantly with malignancy in mammary tissue specimens. Remarkably, a considerable proportion (72.7%) of benign mammary tissue samples scored also positive for nuclear AhR overexpression. We furthermore provide evidence that continued expression of endogenous AhR is critical to promote centriole overduplication induced by cyclin E and that AhR and cyclin E may function in the same pathway. Overexpression of the AhR in the absence of exogenous ligands was found to rapidly disrupt centriole duplication control. Nonetheless, the AhR agonists IO and MeIO were still found to significantly reduce centriole overduplication stimulated by ectopic AhR expression.ConclusionsOur results indicate that continued expression of endogenous AhR promotes centrosome amplification in breast cancer cells in a pathway that involves cyclin E. AhR agonists such as indirubins inhibit centrosome amplification even when stimulated by ectopic expression of the AhR suggesting that these compounds are potentially useful for the chemoprevention of centrosome-mediated cell division errors and malignant progression in neoplasms in which the AhR is overexpressed. Future studies are warranted to determine whether individuals in which nuclear AhR overexpression is detected in benign mammary tissue are at a higher risk for developing pre-cancerous or cancerous breast lesions.

Project description:Greater than 90% of significant genome-wide association study (GWAS) single-nucleotide polymorphisms (SNPs) are in noncoding regions of the genome, but only 25.6% are known expression quantitative trait loci (eQTLs). Therefore, the function of many significant GWAS SNPs remains unclear. We have identified a novel type of eQTL for which SNPs distant from ligand-activated transcription factor (TF) binding sites can alter target gene expression in a SNP genotype-by-ligand-dependent fashion that we refer to as pharmacogenomic eQTLs (PGx-eQTLs)-loci that may have important pharmacotherapeutic implications. In the present study, we integrated chromatin immunoprecipitation-seq with RNA-seq and SNP genotype data for a panel of lymphoblastoid cell lines to identify 10 novel cis PGx-eQTLs dependent on the ligand-activated TF aryl hydrocarbon receptor (AHR)-a critical environmental sensor for xenobiotic (drug) and immune response. Those 10 cis PGx-eQTLs were eQTLs only after AHR ligand treatment, even though the SNPs did not create/destroy an AHR response element-the DNA sequence motif recognized and bound by AHR. Additional functional studies in multiple cell lines demonstrated that some cis PGx-eQTLs are functional in multiple cell types, whereas others displayed SNP-by-ligand-dependent effects in just one cell type. Furthermore, four of those cis PGx-eQTLs had previously been associated with clinical phenotypes, indicating that those loci might have the potential to inform clinical decisions. Therefore, SNPs across the genome that are distant from TF binding sites for ligand-activated TFs might function as PGx-eQTLs and, as a result, might have important clinical implications for interindividual variation in drug response. SIGNIFICANCE STATEMENT: More than 90% of single-nucleotide polymorphisms (SNPs) that are associated with clinical phenotypes are located in noncoding regions of the genome. However, the mechanisms of action of many of those SNPs have not been elucidated, and drugs may unmask functional expression quantitative trail loci (eQTLs). In the current study, we used drugs that bind to the ligand-activated transcription factor aryl hydrocarbon receptor (AHR) and identified SNPs that were associated with interindividual variation in gene expression following drug exposure-termed pharmacogenomic (PGx)-eQTLs. Possibly of greater significance, those PGx-eQTL SNPs were outside of AHR binding sites, indicating that they do not interrupt AHR DNA recognition. PGx-eQTLs such as those described in this work may have crucial implications for interindividual variation in drug.

Dataset Information

A putative role for the aryl hydrocarbon receptor (AHR) gene in a patient with cyclical Cushing's disease.

Publications

A putative role for the aryl hydrocarbon receptor (AHR) gene in a patient with cyclical Cushing's disease.

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