Development and Validation of a Computational Model for Androgen Receptor Activity

Abstract

Testing thousands of chemicals to identify potential androgen receptor (AR) agonists or antagonists would cost millions of dollars and take decades to complete using current validated methods. High-throughput in vitro screening (HTS) and computational toxicology approaches can more rapidly and inexpensively identify potential androgen-active chemicals. We integrated 11 HTS ToxCast/Tox21 in vitro assays into a computational network model to distinguish true AR pathway activity from technology-specific assay interference. The in vitro HTS assays probed perturbations of the AR pathway at multiple points (receptor binding, coregulator recruitment, gene transcription, and protein production) and multiple cell types. Confirmatory in vitro antagonist assay data and cytotoxicity information were used as additional flags for potential nonspecific activity. Validating such alternative testing strategies requires high-quality reference data. We compiled 158 putative androgen-active and -inactive chemicals from a combination of international test method validation efforts and semiautomated systematic literature reviews. Detailed in vitro assay information and results were compiled into a single database using a standardized ontology. Reference chemical concentrations that activated or inhibited AR pathway activity were identified to establish a range of potencies with reproducible reference chemical results. Comparison with existing Tier 1 AR binding data from the U.S. EPA Endocrine Disruptor Screening Program revealed that the model identified binders at relevant test concentrations (<100 μM) and was more sensitive to antagonist activity. The AR pathway model based on the ToxCast/Tox21 assays had balanced accuracies of 95.2% for agonist (n = 29) and 97.5% for antagonist (n = 28) reference chemicals. Out of 1855 chemicals screened in the AR pathway model, 220 chemicals demonstrated AR agonist or antagonist activity and an additional 174 chemicals were predicted to have potential weak AR pathway activity.

The STAT3 Inhibitor Galiellalactone Reduces IL6-Mediated AR Activity in Benign and Malignant Prostate Models

“…In the present study, we confirmed that IL6 increases the transactivation potential of the AR; however, this effect was observed only in the presence of moderate to high androgen concentrations. In particular, we did not observe any IL6-mediated AR activation at 1 to 10 pmol/L of R1881, which is biologically comparable with castrate testosterone levels found in patients, considering the 10-to 100-fold higher transactivation capacity of R1881 (40,41). This is in contrast to several previous publications that have found androgen-independent effects of IL6 on AR activity.…”

Predicting the activation of the androgen receptor by mixtures of ligands using Generalized Concentration Addition

“…MDA-kb2 cells express 240 fmol AR/mg-protein and are stably transfected with a luciferase construct driven by a steroid response element (Hall et al, 1990;Ham et al, 1988;Wilson, Bobseine and Gray, 2004). The assay is included in Tox21 and ToxCast (Kleinstreuer et al, 2017). No toxicity was evident at the concentrations tested (Supplemental Material, Figure S1).…”

Measured concentrations of consumer product chemicals in California house dust: Implications for sources, exposure, and toxicity potential

“…For endocrine‐disrupting potential, we evaluated four main processes, including androgen, estrogen, thyroid, and steroidogenic. For androgen, we utilized androgen receptor (AR) pathway activity integrated from 11 AR‐related in vitro HTS ToxCast assays and considered compounds with area under the curve (AUC) of ≥0.1 to be active in at least one AR pathway assay (active, inactive) . For estrogen, we utilized estrogen receptor (ER) interaction scores integrated from 13 ER‐related in vitro ToxCast assays and considered compounds with an AUC score of ≥0.1 to be active in at least one ER pathway assay (active, inactive) .…”

“…For androgen, we utilized androgen receptor (AR) pathway activity integrated from 11 AR-related in vitro HTS ToxCast assays and considered compounds with area under the curve (AUC) of ≥0.1 to be active in at least one AR pathway assay (active, inactive). 37 For estrogen, we utilized estrogen receptor (ER) interaction scores integrated from 13 ER-related in vitro ToxCast assays and considered compounds with an AUC score of ≥0.1 to be active in at least one ER pathway assay (active, inactive). 38 For thyroid, we utilized the results from the in vitro Amplex UltraRed-thyroperoxidase or thyroid peroxidase (AUR-TPO) assay 39 and a thyroid-specific in vitro HTS ToxCast assay.…”