Etienne Audet-walsh - Academia.edu (original) (raw)

Papers by Etienne Audet-walsh

Results and limitations Seven SNPs located in or nearby genes implicated in steroid hormone metab... more Results and limitations Seven SNPs located in or nearby genes implicated in steroid hormone metabolism were significantly associated with prostate volume: HSD17B2 (rs1119933), ESR2 (rs8006145), SULT2B1 (rs279451), NQO1 (rs2917670), ESR1 (rs1569788), GSTP1 (rs1138272), and CYP19A1 (rs17523880). Significant association was maintained after multivariate analysis for four SNPs, indicating their independent association with prostate volume. The power of the association of each SNP with prostate volume was comparable to the effect of age. The strongest associations were found with variants in ESR1, ESR2, HSD17B2, and CYP19A1 genes, indicating a potential role of the estrogen signaling pathway in genesis of BPH. Conclusions Our results are in favor of an implication of estrogen biotransformation and signaling pathways in the pathophysiology of BPH.

How androgen signaling contributes to the oncometabolic state of prostate cancer remains unclear.... more How androgen signaling contributes to the oncometabolic state of prostate cancer remains unclear. Here, we show how the estrogen-related receptor g (ERRg) negatively controls mitochondrial respiration in prostate cancer cells. Sustained treatment of prostate cancer cells with androgens increased the activity of several metabolic pathways, including aerobic glycolysis, mitochondrial respiration, and lipid synthesis. An analysis of the intersection of gene expression, binding events, and motif analyses after androgen exposure identified a metabolic gene expression signature associated with the action of ERRg. This metabolic state paralleled the loss of ERRg expression. It occurred in both androgen-dependent and castration-resistant prostate cancer and was associated with cell proliferation. Clinically, we observed an inverse relationship between ERRg expression and disease severity. These results illuminate a mechanism in which androgendependent repression of ERRg reprograms prostate cancer cell metabolism to favor mitochondrial activity and cell proliferation. Furthermore, they rationalize strategies to reactivate ERRg signaling as a generalized therapeutic approach to manage prostate cancer. Cancer Res; 77(2); 378-89. Ó2016 AACR.

Androgen receptor (AR) signaling reprograms cellular metabolism to support prostate cancer (PCa) ... more Androgen receptor (AR) signaling reprograms cellular metabolism to support prostate cancer (PCa) growth and survival. Another key regulator of cellular metabolism is mTOR, a kinase found in diverse protein complexes and cellular localizations, including the nucleus. However, whether nuclear mTOR plays a role in PCa progression and participates in direct transcriptional cross-talk with the AR is unknown. Here, via the intersection of gene expression, genomic, and metabolic studies, we reveal the existence of a nuclear mTOR-AR transcriptional axis integral to the metabolic rewiring of PCa cells. Androgens reprogram mTOR-chromatin associations in an AR-dependent manner in which activation of mTOR-dependent metabolic gene networks is essential for androgeninduced aerobic glycolysis and mitochondrial respiration. In models of castration-resistant PCa cells, mTOR was capable of transcriptionally regulating metabolic gene programs in the absence of androgens, highlighting a potential novel castration resistance mechanism to sustain cell metabolism even without a functional AR. Remarkably, we demonstrate that increased mTOR nuclear localization is indicative of poor prognosis in patients, with the highest levels detected in castration-resistant PCa tumors and metastases. Identification of a functional mTOR targeted multigene signature robustly discriminates between normal prostate tissues, primary tumors, and hormone refractory metastatic samples but is also predictive of cancer recurrence. This study thus underscores a paradigm shift from AR to nuclear mTOR as being the master transcriptional regulator of metabolism in PCa.

The identification of the estrogen-related receptors (ERRs) as the first orphan nuclear receptors... more The identification of the estrogen-related receptors (ERRs) as the first orphan nuclear receptors ignited a new era in molecular endocrinology, which led to the discovery of new ligand-dependent response systems. Although ERR subfamily members have yet to be associated with a natural ligand, the characterization of these orphan receptors has demonstrated that they occupy a strategic node in the transcriptional control of cellular energy metabolism. In particular, ERRs are required for the response to various environmental challenges that require high energy levels by the organism. As central regulators of energy homeostasis, ERRs may also be implicated in the etiology of metabolic disorders, such as type 2 diabetes and metabolic syndrome. Here, we review the recent evidence that further highlights the role of ERRs in metabolic control, particularly in liver and skeletal muscle, and their likely involvement in metabolic diseases. Consequently, we also explore the promises and pitfalls of ERRs as potential therapeutic targets.

The prognostic significance of common deletions in uridine diphospho-glucuronosyltransferase 2B (... more The prognostic significance of common deletions in uridine diphospho-glucuronosyltransferase 2B (UGT2B) genes encoding sex steroid metabolic enzymes has been recently recognized in localized prostate cancer (PCa) after radical prostatectomy (RP). However, the role of germline variations at the UGT1 locus, encoding half of all human UGTs and primarily involved in estrogen metabolism, remains unexplored. We investigated whether variants of UGT1 are potential prognostic markers. We studied 526 Caucasian men who underwent RP for clinically localized PCa. Genotypes of patients for 34 haplotype-tagged single-nucleotide polymorphisms (htSNPs) and 11 additional SNPs across the UGT1 locus previously reported to mark common variants including functional polymorphisms were determined. The risk of biochemical recurrence (BCR) was estimated using adjusted Cox proportional hazards regression and Kaplan-Meier analysis. We further investigated whether variants are associated with plasma hormone levels by mass spectrometry. In multivariable models, seven htSNPs were found to be significantly associated with BCR. A greater risk was revealed for four UGT1 intronic variants with hazard ratios (HRs) of 1.59-1.88 (P!0.002) for htSNPs in UGT1A10, UGT1A9, and UGT1A6. Conversely, decreased BCR was associated with three htSNPs in introns of UGT1A10 and UGT1A9 (HRZ0.56-058; P%0.01). An unfavorable UGT1 haplotype comprising all risk alleles, with a frequency of 14%, had a HR of 1.68 (95% CIZ1.13-2.50; PZ0.011). Significant alteration in circulating androsterone levels was associated with this haplotype, consistent with changes in hormonal exposure. This study provides the first evidence, to our knowledge, that germline polymorphisms of UGT1 are potential predictors of recurrence of PCa after prostatectomy.

Graphical Abstract Highlights d The PGC-1a/ERRa axis is a key effector of AMPK metabolic reprogra... more Graphical Abstract Highlights d The PGC-1a/ERRa axis is a key effector of AMPK metabolic reprogramming in cancer d The PGC-1a/ERRa axis represses folate cycle metabolism d The PGC-1a/ERRa axis decreases purine biosynthesis d The PGC-1a/ERRa axis sensitizes cells and tumors to antifolate therapy SUMMARY

The tumor suppressor folliculin (FLCN) forms a repressor complex with AMP-activated protein kinas... more The tumor suppressor folliculin (FLCN) forms a repressor complex with AMP-activated protein kinase (AMPK). Given that AMPK is a master regulator of cellular energy homeostasis, we generated an adipose-specific Flcn (Adipoq-FLCN) knockout mouse model to investigate the role of FLCN in energy metabolism. We show that loss of FLCN results in a complete metabolic reprogramming of adipose tissues, resulting in enhanced oxidative metabolism. Adipoq-FLCN knockout mice exhibit increased energy expenditure and are protected from high-fat diet (HFD)induced obesity. Importantly, FLCN ablation leads to chronic hyperactivation of AMPK, which in turns induces and activates two key transcriptional regulators of cellular metabolism, proliferator-activated receptor γ (PPARγ) coactivator-1α (PGC-1α) and estrogen-related receptor α (ERRα). Together, the AMPK/PGC-1α/ERRα molecular axis positively modulates the expression of metabolic genes to promote mitochondrial biogenesis and activity. In addition, mitochondrial uncoupling proteins as well as other markers of brown fat are up-regulated in both white and brown FLCN-null adipose tissues, underlying the increased resistance of Adipoq-FLCN knockout mice to cold exposure. These findings identify a key role of FLCN as a negative regulator of mitochondrial function and identify a novel molecular pathway involved in the browning of white adipocytes and the activity of brown fat.

5a-Reductase types 1 and 2, encoded by SRD5A1 and SRD5A2, are the two enzymes that can catalyze t... more 5a-Reductase types 1 and 2, encoded by SRD5A1 and SRD5A2, are the two enzymes that can catalyze the conversion of testosterone to dihydrotestosterone, the most potent androgen receptor (AR) agonist in prostate cells. 5a-Reductase type 2 is the predominant isoform expressed in the normal prostate. However, its expression decreases during prostate cancer (PCa) progression, whereas SRD5A1 increases, and the mechanism underlying this transcriptional regulatory switch is still unknown. Interrogation of SRD5A messenger RNA expression in three publicly available data sets confirmed that SRD5A1 is increased in primary and metastatic PCa compared with nontumoral prostate tissues, whereas SRD5A2 is decreased. Activation of AR, a major oncogenic driver of PCa, induced the expression of SRD5A1 from twofold to fourfold in three androgen-responsive PCa cell lines. In contrast, AR repressed SRD5A2 expression in this context. Chromatin-immunoprecipitation studies established that AR is recruited to both SRD5A1 and SRD5A2 genes following androgen stimulation but initiates transcriptional activation only at SRD5A1 as monitored by recruitment of RNA polymerase II and the presence of the H3K27Ac histone mark. Furthermore, we showed that the antiandrogens bicalutamide and enzalutamide block the AR-mediated regulation of both SRD5A1 and SRD5A2, highlighting an additional mechanism explaining their beneficial effects in patients. In summary, we identified an AR-dependent transcriptional regulation that explains the differential expression of 5a-reductase types 1 and 2 during PCa progression. Our work thus defines a mechanism by which androgens control their own synthesis via differential regulatory control of the expression of SRD5A1 and SRD5A2. (Endocrinology 158: 1015(Endocrinology 158: -1021(Endocrinology 158: , 2017

Purpose: Prostate cancer is a heterogeneous genetic disease, and molecular methods for predicting... more Purpose: Prostate cancer is a heterogeneous genetic disease, and molecular methods for predicting prognosis in patients with aggressive form of the disease are urgently needed to better personalize treatment approaches. The objective was to identify host genetic variations in candidate steroidogenic genes affecting hormone levels and prostate cancer progression.

Background: Endometrial cancer (EC) predominantly occurs after menopause and is strongly related ... more Background: Endometrial cancer (EC) predominantly occurs after menopause and is strongly related to steroid hormones, particularly estrogens. However, the relationship between these hormones and clinical characteristics remains unaddressed.

Background: Endometrial cancer is the most common gynecological malignancy. Estrogen exposure is ... more Background: Endometrial cancer is the most common gynecological malignancy. Estrogen exposure is strongly associated with endometrial cancer. Whereas this cancer occurs predominantly in postmenopausal women lacking estrogen production by ovaries, the conversion of adrenal androgen-estrogen precursors to estradiol (E 2 ), estrone (E 1 ), and its sulfate (E 1 -S) has been well documented in peripheral tissues.

Mémoire présenté à la Faculté des études supérieures de l'Université Laval dans le cadre du progr... more Mémoire présenté à la Faculté des études supérieures de l'Université Laval dans le cadre du programme de maîtrise en Biologie pour l'obtention du grade de maître ès sciences (M.Sc.) DÉPARTEMENT DE BIOLOGIE FACULTÉ DES SCIENCES ET DE GÉNIE UNIVERSITÉ LA V AL QUÉBEC 2008 © Étienne Audet-Walsh, 2008 . Résumé ' Les gènes de la sous-famille CYP 2B sont fortement activés par des traitements au phénobarbital ou des inducteurs de type phénobarbital, et cette réponse nécessite la présence du constitutive androstane receptor (CAR). La dexaméthasone, un glucocorticoïde synthétique, a la capacité d' induire CYP2Bl et CYP2B2 chez le rat et CYP2B lOchez la souris. Les travaux présentés dans ce mémoire démontrent le rôle majeur du récepteur des glucocorticoïdes (GR) dans la réponse à la dexaméthasone, ce qui constitue une nouvelle voie de régulation des gènes CYP2B. De plus, cinq régions critiques impliquées dans la réponse ont été caractérisées et elles formeraient les éléments clé d ' une unité de réponse aux glucocorticoïdes de CYP2B2. Pour la première fois, CAR peut jouer le rôle de facteur accessoire, en stimulant la réponse à la dexaméthasone passant par GR. En conclusion, ' les résultats présentés ici décrivent une nouvelle voie de régulation des gènes CYP2B de rongeurs.

Background: The relationship between polymorphisms in the hydroxysteroid (17-beta) dehydrogenase ... more Background: The relationship between polymorphisms in the hydroxysteroid (17-beta) dehydrogenase (HSD17B) family of genes, which are involved in steroid hormone biotransformation, and the risk of prostate cancer (PCa) progression remains unexplored. Objective: Determine whether inherited variations in HSD17B genes are associated with PCa progression. Design, setting, and participants: We studied two independent Caucasian cohorts composed of 526 men with organ-confined PCa and 213 men with advanced disease who had a median follow-up of 7.4 yr and 7.8 yr after surgery, respectively. Measurements: Patients with localised PCa were genotyped for 88 haplotype-tagging single nucleotide polymorphisms in HSD17B type 1 (HSD17B1), type 2 (HSD17B2), type 3 (HSD17B3), type 4 (HSD17B4), type 5 (HSD17B5), and type 12 (HSD17B12), and their prognostic significance on disease progression was assessed using Kaplan-Meier survival curves and Cox regression models. Positive findings were then investigated in advanced disease. Results and limitations: After adjusting for known risk factors, 12 SNPs distributed across HSD17B2, HSD17B3, and HSD17B12 were significantly associated with risk of biochemical recurrence (BCR) in localised PCa (for variants in HSD17B2: hazard ratio [HR]: 1.92-2.93; p = 0.025-0.004). In addition, four variants of HSD17B2 (rs1364287, rs2955162, rs1119933, rs9934209) were significantly associated with progression-free survival (HR: 2.96-4.69; p = 0.004-0.00005) and overall survival in advanced disease (HR: 3.98-8.14; p = 0.003-0.00002). Four variants of HSD17B3 and HSD17B12 were associated with a reduced risk of BCR (HR: 0.51-0.65; p = 0.020-0.036) but not with progression in advanced disease. These results were generated mainly in Caucasians and should be studied in other ethnic groups. Conclusions: This study suggests a prominent role for common genetic variants in the HSD17B2 pathway in PCa progression.

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Estrogens, namely, 17 -estradiol (E 2 ), are conjugated to glucuronides (G), and this metabolic c... more Estrogens, namely, 17 -estradiol (E 2 ), are conjugated to glucuronides (G), and this metabolic conversion is part of their tissular-concentration control-mechanism. This inactivation process has been observed, in addition to the liver, in several estrogen-dependent tissues and the resulting polar metabolites are detected in circulation. We developed and validated a highly sensitive and specific mass spectrometry-based method to directly measure estrogen-G serum levels. The method uses deuterated standards but does not involve enzymatic hydrolysis, a major improvement over previous techniques. Estrone (E 1 ), E 1 -sulfate, E 2 , the 3-G of E 1 , E 2 , 2-methoxy-E 1 (2-MeOE 1 ) and 2-methoxy-E 2 (2-MeOE 2 ), and the 17-G of E 2 were measured in serum of 19 premenopausal and 10 postmenopausal healthy women. Two extractions, solid-phase and liquid-liquid, were performed to isolate the estrogens. Estrogens were then quantified by mass spectrometry in the negative MRM ion mode using an API3200 spectrometer with a turbo ionspray source. The method selectively measured estrogen glucuronides with sensitivity g5 pg/mL, accuracy 90-111%, and reproducibility (CV ) 1.4-13.3%). The method is applicable between 5 and 1000 pg/mL. For the ovarian follicular phase, the major metabolite found was E 1 -3G, with E 2 -3G and 2-MeOE 1 -3G found in lesser amounts (54, 10.4, and 7.8 pg/mL, respectively) These concentrations are 2.6-to 3-fold greater than found for luteal-phase estrogens. The concentrations of E 2 -17G and 2-MeOE 2 -3G were usually less than the limit of quantification. In serum of postmenopausal women, E 1 -3G was the most abundant estrogen found (30.9 pg/mL). Our method profiles estrogens and estrogen-glucuronides and may represent a new tool to identify biomarkers in hormone-dependent diseases.

The prognostic relevance of inherited variations in hormone-related genes in the context of prost... more The prognostic relevance of inherited variations in hormone-related genes in the context of prostate cancer (PCa) progression has not been well studied. Of these, UDP-glucuronosyltransferase (UGT) gene products lead to inactivation of steroids.

Hepatic cytochrome P450 (P450) enzymes metabolize exogenous and endogenous compounds, and many ar... more Hepatic cytochrome P450 (P450) enzymes metabolize exogenous and endogenous compounds, and many are inducible by xenobiotics. Their synthesis is tightly regulated, particularly through nuclear receptors. Expression of murine CYP2B genes is strongly activated by treatment with phenobarbital or phenobarbital-like inducers, and a detectable response requires the presence of the constitutive androstane receptor (CAR). However, other compounds can also induce murine CYP2B proteins. For example, dexamethasone is known to induce rat CYP2B1 and CYP2B2 and mouse CYP2B10. Using human HepG2 and rat H4IIEC3 hepatoma cell lines, we found that dexamethasone induction of CYP2B2 and Cyp2b10 luciferase reporters required the glucocorticoid receptor. Given the well known observation that CYP2B genes are not phenobarbital-responsive in cultured cell lines, the dexamethasone responsiveness of CYP2B reporter con-structs in cell lines demonstrates in itself that the mechanism of dexamethasone induction is distinct from that of phenobarbital. We also analyzed the relative importance of the phenobarbital response unit (PBRU) and of a known glucocorticoid response element in this response. Both sites contributed to the response, but other sites were required for maximal induction. CAR was also found to act as an accessory factor to stimulate the response to dexamethasone by the glucocorticoid receptor. Furthermore, in H4IIEC3 cells, CAR activated the PBRU in the natural sequence context of the CYP2B2 and Cyp2b10 5 flanks. In summary, there are at least two independent mechanisms of CYP2B induction: one involving phenobarbital and phenobarbital-like inducers and another involving glucocorticoids that induce via the glucocorticoid receptor with CAR acting as an accessory factor.