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Adverse Outcome Pathway Network-Based Assessment of the Interactive Effects of an Androgen Receptor Agonist and an Aromatase Inhibitor on Fish Endocrine Function.

ABSTRACT: Predictive approaches to assessing the toxicity of contaminant mixtures have been largely limited to chemicals that exert effects through the same biological molecular initiating event. However, by understanding specific pathways through which chemicals exert effects, it may be possible to identify shared "downstream" nodes as the basis for forecasting interactive effects of chemicals with different molecular initiating events. Adverse outcome pathway (AOP) networks conceptually support this type of analysis. We assessed the utility of a simple AOP network for predicting the effects of mixtures of an aromatase inhibitor (fadrozole) and an androgen receptor agonist (17β-trenbolone) on aspects of reproductive endocrine function in female fathead minnows. The fish were exposed to multiple concentrations of fadrozole and 17β-trenbolone individually or in combination for 48 or 96 h. Effects on 2 shared nodes in the AOP network, plasma 17β-estradiol (E2) concentration and vitellogenin (VTG) production (measured as hepatic vtg transcripts) responded as anticipated to fadrozole alone but were minimally impacted by 17β-trenbolone alone. Overall, there were indications that 17β-trenbolone enhanced decreases in E2 and vtg in fadrozole-exposed fish, as anticipated, but the results often were not statistically significant. Failure to consistently observe hypothesized interactions between fadrozole and 17β-trenbolone could be due to several factors, including lack of impact of 17β-trenbolone, inherent biological variability in the endpoints assessed, and/or an incomplete understanding of interactions (including feedback) between different pathways within the hypothalamic-pituitary-gonadal axis. Environ Toxicol Chem 2020;39:913-922. © 2020 SETAC.

SUBMITTER: Ankley GT

PROVIDER: S-EPMC7357796 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:LESSONS LEARNED:Studies targeting the androgen receptor (AR) signaling pathway in aromatase inhibitor (AI)-resistant breast cancer are limited. Bicalutamide, one of the commonly used AR inhibitors in prostate cancer, in combination with AI, did not show synergistic activity in patients with estrogen receptor-positive and AI-resistant disease in this phase II, single-arm study. The clinical benefit rate and objective response rate at 6 months were 16.7% and 0%, respectively, and the study was terminated after the first stage. BACKGROUND:Endocrine resistance is a major problem in clinical practice. Studies have shown that androgen receptor (AR) signaling activation may be one of the mechanisms, and targeting AR showed some promising results in AR-positive triple-negative breast cancer. The aim of this study was to assess the efficacy and safety of bicalutamide plus another aromatase inhibitor in patients with nonsteroidal aromatase inhibitor (AI) or steroidal AI resistance and estrogen receptor (ER)-positive and AR-positive advanced breast cancer. METHODS:A Simon's two-stage, phase II, single-arm study was conducted. We assumed the clinical benefit rate (CBR) of 40% would be significant in clinical practice. In this case, if ?4 patients of the 19 patients in the first stage benefited from treatment, the CBR would achieve the assumed endpoint. If fewer than four patients benefited from treatment in the first stage, the trial would be terminated. All patients received bicalutamide 50 mg per day orally plus another aromatase inhibitor. The primary outcome was CBR; secondary outcomes included objective response rate (ORR), progression-free survival (PFS), and tolerability. RESULTS:A total of 19 patients enrolled in the first stage, and 18 patients met all criteria for analysis. The trial terminated according to protocol after the first stage. After a median follow-up of 14 months, the CBR at 6 months was 16.7% (3/18); no patients with partial or complete response were observed. The median PFS was 2.7 months. Bicalutamide in combination with AI was well tolerated. CONCLUSION:Bicalutamide in combination with another AI did not show synergistic activity in patients with ER-positive breast cancer and AI resistance. Results suggest that no more large-sample clinical trials should be conducted in this population for overcoming endocrine resistance.

Project description:One objective in developing adverse outcome pathways (AOPs) is to connect biological changes that are relevant to risk assessors (i.e., fecundity) to molecular and cellular-level alterations that might be detectable at earlier stages of a chemical exposure. Here, we examined biochemical responses of fathead minnows (Pimephales promelas) to inform an AOP relevant to spironolactone's activation of the androgen receptor, as well as explore other biological impacts possibly unrelated to this receptor. Liquid chromatography with high resolution mass spectrometry (LC-MS) was used to measure changes in endogenous polar metabolites in livers of male and female fish that were exposed to five water concentrations of spironolactone (0, 0.05, 0.5, 5, or 50μgL-1) for 21days. Metabolite profiles were affected at the two highest concentrations (5 and 50μgL-1), but not in the lower-level exposures, which agreed with earlier reported results of reduced female fecundity and plasma vitellogenin (VTG) levels. We then applied partial least squares regression to assess whether metabolite alterations covaried with changes in fecundity, VTG gene expression and protein concentrations, and plasma 17β-estradiol and testosterone concentrations. Metabolite profiles significantly covaried with all measured endpoints in females, but only with plasma testosterone in males. Fecundity reductions occurred in parallel with changes in metabolites important in osmoregulation (e.g., betaine), membrane transport (e.g., l-carnitine), and biosynthesis of carnitine (e.g., methionine) and VTG (e.g., glutamate). Based on a network analysis program (i.e., mummichog), spironolactone also affected amino acid, tryptophan, and fatty acid metabolism. Thus, by identifying possible key events related to changes in biochemical pathways, this approach built upon an established AOP describing spironolactone's androgenic properties and highlighted broader implications potentially unrelated to androgen receptor activation, which could form a basis for the development of an AOP network.

Project description:Abstract Background: Partial Androgen Insensitivity Syndrome (PAIS) (OMIM # 312300) is one of the causes of Disorders/Differences of Sex Development with 46,XY karyotype and normal or increased testosterone secretion that results in atypical genitalia. In general, it is caused by inactivating mutations on AR gene (Xq12 - OMIM * 313700), therefore it presents an X-linked recessive inheritance. Individuals raised as males have incomplete puberty with micropenis, sparse hairs, gynecomastia and increased LH, testosterone and estradiol serum levels. Therefore, the use of aromatase inhibitor in these cases becomes a logical indication aiming to increase testosterone levels in the tentative of supplanting its peripheral resistance and decreasing estrogen levels. Objective: To present clinical and laboratory data during the first year of use of aromatase inhibitor in puberty of three boys with confirmed molecular diagnosis of PAIS. Results: All subjects used letrozole (2.5 mg daily during 12 months). None reported significant side effects. Cases 1 and 2 are brothers (p.Ala596Tre). Case 1: Onset of treatment at age 12; height changed from 158 cm (z = +1.15) to 166 cm (z = +1.21), Tanner from G2P2T2 to G3P3T1, penis from 4.0 to 6.5 cm, LH from 7.5 to 18.3 IU/L (NR: 1.5 to 9.3 IU/L), testosterone from 361 to 1,347 ng/dL (NR: 165 to 763 ng/dL), estradiol from 35 to <5.0 pg/mL (NR: < 40 pg/mL) and bone age remained at 13 years. Case 2: Onset of treatment at age 11; height changed from 156 cm (z = +1.71) to 163 cm (z = +1.80), Tanner from G2P2T2 to G3P3T1, penis from 3.5 to 5.5 cm, LH from 4.8 to 12.4 IU/L (NR: 1.5 to 9.3 IU/L), testosterone from 259 to 1,069 ng/dL (NR: 165 to 763 ng/dL), estradiol from 28 to <5.0 pg/mL (NR: < 40 pg/mL) and bone age remained at 12.5 years. Case 3 (p.Ser597Arg): Onset of treatment at age 12; height changed from 153 cm (z = +0.49) to 161 cm (z = +0.55), Tanner from G2P2T1 to G3P3T1, penis from 4.0 to 7.0 cm, LH from 8.5 to 17.2 IU/L (NR: 1.5 to 9.3 IU/L), testosterone from 280 to 889 ng/dL (NR: 165 to 763 ng/dL), estradiol from 32 to <5.0 pg/mL (NR: < 40 pg/mL) and bone age remained at 13.5 years. Discussion: There are no reports in the literature of the use of aromatase inhibitor in PAIS. The results of this pilot study (gynecomastia regression, significant testosterone level increases with decrease in estradiol levels, increment in height without bone age advancing, progression of puberty and penile growth) are sustaining for the indication of this treatment in boys with PAIS during puberty.

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Adverse Outcome Pathway Network-Based Assessment of the Interactive Effects of an Androgen Receptor Agonist and an Aromatase Inhibitor on Fish Endocrine Function.

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