Application of an in Vitro Assay to Identify Chemicals That Increase Estradiol and Progesterone Synthesis and Are Potential Breast Cancer Risk Factors

High-Throughput Transcriptomics Screen of ToxCast Chemicals in U-2 OS Cells

New approach methodologies (NAMs) aim to accelerate the pace of chemical risk assessment while simultaneously reducing cost and dependency on animal studies. High Throughput Transcriptomics (HTTr) is an emerging NAM in the field of chemical hazard evaluation for establishing in vitro points-of-departure and providing mechanistic insight. In the current study, 1201 test chemicals were screened for bioactivity at eight concentrations using a 24-h exposure duration in the human- derived U-2 OS osteosarcoma cell line with HTTr. Assay reproducibility was assessed using three reference chemicals that were screened on every assay plate. The resulting transcriptomics data were analyzed by aggregating signal from genes into signature scores using gene set enrichment analysis, followed by concentration-response modeling of signatures scores. Signature scores were used to predict putative mechanisms of action, and to identify biological pathway altering concentrations (BPACs). BPACs were consistent across replicates for each reference chemical, with replicate BPAC standard deviations as low as 5.6 × 10-3 μM, demonstrating the internal reproducibility of HTTr-derived potency estimates. BPACs of test chemicals showed modest agreement (R2 = 0.55) with existing phenotype altering concentrations from high throughput phenotypic profiling using Cell Painting of the same chemicals in the same cell line. Altogether, this HTTr based chemical screen contributes to an accumulating pool of publicly available transcriptomic data relevant for chemical hazard evaluation and reinforces the utility of cell based molecular profiling methods in estimating chemical potency and predicting mechanism of action across a diverse set of chemicals.

Chronic aquatic toxicity assessment of diverse chemicals on Daphnia magna using QSAR and chemical read-across

We have modeled here chronic Daphnia toxicity taking pNOEC (negative logarithm of no observed effect concentration in mM) and pEC50 (negative logarithm of half-maximal effective concentration in mM) as endpoints using QSAR and chemical read-across approaches. The QSAR models were developed by strictly obeying the OECD guidelines and were found to be reliable, predictive, accurate, and robust. From the selected features in the developed models, we have found that an increase in lipophilicity and saturation, the presence of electrophilic or electronegative or heavy atoms, the presence of sulphur, amine, and their related functionality, an increase in mean atomic polarizability, and higher number of (thio-) carbamates (aromatic) groups are responsible for chronic toxicity. Therefore, this information might be useful for the development of environmentally friendly and safer chemicals and data-gap filling as well as reducing the use of identified toxic chemicals which have chronic toxic effects on aquatic ecosystems. Approved classes of drugs from DrugBank databases and diverse groups of chemicals from the Chemical and Product Categories (CPDat) database were also assessed through the developed models.

Application of the Key Characteristics Framework to Identify Potential Breast Carcinogens Using Publicly Available in Vivo, in Vitro, and in Silico Data

BACKGROUND

Chemicals that induce mammary tumors in rodents or activate estrogen or progesterone signaling are likely to increase breast cancer (BC) risk. Identifying chemicals with these activities can prompt steps to protect human health.

OBJECTIVES

We compiled data on rodent tumors, endocrine activity, and genotoxicity to assess the key characteristics (KCs) of rodent mammary carcinogens (MCs), and to identify other chemicals that exhibit these effects and may therefore increase BC risk.

METHODS

Using authoritative databases, including International Agency for Research on Cancer (IARC) Monographs and the US Environmental Protection's (EPA) ToxCast, we selected chemicals that induce mammary tumors in rodents, stimulate estradiol or progesterone synthesis, or activate the estrogen receptor (ER) in vitro. We classified these chemicals by their genotoxicity and strength of endocrine activity and calculated the overrepresentation (enrichment) of these KCs among MCs. Finally, we evaluated whether these KCs predict whether a chemical is likely to induce mammary tumors.

RESULTS

We identified 279 MCs and an additional 642 chemicals that stimulate estrogen or progesterone signaling. MCs were significantly enriched for steroidogenicity, ER agonism, and genotoxicity, supporting the use of these KCs to predict whether a chemical is likely to induce rodent mammary tumors and, by inference, increase BC risk. More MCs were steroidogens than ER agonists, and many increased both estradiol and progesterone. Enrichment among MCs was greater for strong endocrine activity vs. weak or inactive, with a significant trend.

DISCUSSION

We identified hundreds of compounds that have biological activities that could increase BC risk and demonstrated that these activities are enriched among MCs. We argue that many of these should not be considered low hazard without investigating their ability to affect the breast, and chemicals with the strongest evidence can be targeted for exposure reduction. We describe ways to strengthen hazard identification, including improved assessments for mammary effects, developing assays for more KCs, and more comprehensive chemical testing. https://doi.org/10.1289/EHP13233.

Risk of breast cancer in daughters of agricultural workers in Denmark

OBJECTIVES

Agricultural workers face unique occupational hazards such as pesticide exposure, which has been associated with breast cancer. However, research considering the association between parental agricultural work and breast cancer in female offspring is lacking. Therefore, the aim of the present nested case-control study was to explore this association.

METHODS

The Danish Cancer Registry was utilized to identify women diagnosed with primary breast cancer. A total of 5587 cases were included in the study, and for each case, 20 cancer-free female controls were selected, matched on year of birth. It was a requisition that both cases and controls were born in Denmark and that either maternal or paternal employment history was available.

RESULTS

Adverse associations were consistently noted for different time windows of maternal employment in "Horticulture" and breast cancer. Inverse associations were observed for paternal employment in most of the examined agricultural industries, although a small increased risk was indicated for perinatal employment in "Horticulture". Furthermore, maternal preconceptional employment in "Horticulture" was observed to increase the risk of ER positive tumors (odds ratio [OR] = 1.79, 95% confidence interval [CI]: 1.13-2.85, whereas parental perinatal employment was linked to an elevated risk of ER negative tumors (maternal employment: OR = 2.48, 95% CI: 1.18-5.21; paternal employment: OR = 1.62, 95% CI: 0.70-3.77).

CONCLUSIONS

The present study indicates that maternal horticultural employment in different potential susceptible time windows may elevate the risk of breast cancer subtypes in daughters. These findings need to be reproduced in future prospective cohort studies, including information on e.g., pesticide exposure withing agricultural job categories and lifestyle factors.

Exposure to Organochlorine Pesticides and Female Breast Cancer Risk According to Molecular Receptors Expression: a Systematic Review and Meta-analysis of Epidemiological Evidence

PURPOSE OF REVIEW

Organochlorine pesticides (OCP) have been proposed as potential mammary carcinogens since they interact with steroid signaling pathways. However, the epidemiological results are not conclusive. Most studies have evaluated breast cancer (BC) as a single entity without considering the different molecular expressions, including estrogen receptor (ER), progesterone receptor (PR), and HER2, that could differ in their association with these contaminants. Hence, we assessed the association between biological concentration of OCP and BC, according to its molecular receptor expression, based on a systematic review and meta-analysis.

RECENT FINDINGS

Of the 141 articles eligible for full-text review, nine met the inclusion criteria. The way in which molecular expression was reported was heterogeneous; therefore, the inclusion of studies in the meta-analysis was limited to eight articles. A negative association was identified for β-hexachlorocyclohexane and trans-nonachlor with ER + tumors and between hexachlorobenzene and ER - tumors. No associations were observed for p,p'-dichlorodiphenyldichloroethylene, cis-nonachlor, and dieldrin, and it was not possible to evaluate the associations between OCP with HER2 expression or triple-negative tumors due to lack of data. The results suggest that some OCP might be associated with BC depending on the expression of ER. However, the evidence is not conclusive due to the scarce data. We identified several methodological aspects to fill the gaps in knowledge and increase the comparability among studies.

The Effect of Individual or Study-Wide Report-Back on Knowledge, Concern, and Exposure-Reducing Behaviors Related to Endocrine-Disrupting Chemicals

BACKGROUND

To make informed decisions about endocrine-disrupting chemicals (EDCs), people need functional understanding of exposures and health and an ability to act on their knowledge. The return of biomonitoring results is an opportunity to educate people about EDCs and motivate exposure reduction.

OBJECTIVES

This study investigates environmental health knowledge about EDCs, concerns about health effects, and exposure-reducing behaviors before and after the return of individual-level exposure results or only study-wide results.

METHODS

Women in the Child Health and Development Studies who were biomonitored for 42 EDCs were randomly assigned to receive a report with personal chemical results or only study-wide findings. We interviewed participants before and after report-back about their knowledge and concerns about EDCs and how frequently they performed exposure-related behaviors. We investigated baseline differences by education and race and examined changes after report-back by race and report type.

RESULTS

Participants (n = 135 ) demonstrated general understanding of exposure pathways and health impacts of EDCs. For 9 out of 20 knowledge questions, more than 90% of participants (n ≥ 124 ) gave correct responses at baseline, including for questions about chemicals' persistence in the body and effects of early-life exposure. Most participants held two misconceptions-about chemical safety testing in the United States and what doctors can infer from EDC results-although errors decreased after report-back. Initially, concern was higher for legacy pollutants, but report-back increased concern for consumer product chemicals. After report-back, participants took some actions to reduce exposures, particularly to per- and polyfluoroalkyl substances, and total behavior was associated with knowledge and concern but not race, education, or report type.

DISCUSSION

This study demonstrated that participants had foundational knowledge about EDCs and that report-back further built their environmental health literacy. We conclude that future communications should target misconceptions about chemicals regulation in the United States, because information about regulations is crucial for people to evaluate risks posed by consumer product chemicals and decide whether to engage with public policy. https://doi.org/10.1289/EHP12565.

Identifying Toxic Consumer Products: A Novel Data Set Reveals Air Emissions of Potent Carcinogens, Reproductive Toxicants, and Developmental Toxicants

Consumer products are important sources of exposure to harmful chemicals. Product composition is often a mystery to users, however, due to gaps in the laws governing ingredient disclosure. A unique data set that the California Air Resources Board (CARB) uses to determine how volatile organic chemicals (VOCs) from consumer products affect smog formation holds a partial solution. By analyzing CARB data on VOCs in consumer products, we identified and quantified emissions of volatile chemicals regulated under the California Safe Drinking Water and Toxic Enforcement Act ("Prop 65"). We here highlight individual chemicals as well as consumer product categories that people are likely to be exposed to as individual consumers, in the workplace, and at the population level. Of the 33 Prop 65-listed chemicals that appear in the CARB emissions inventory, we classified 18 as "top tier priorities for elimination". Among these, methylene chloride and N-methyl-2-pyrrolidone were most prevalent in products across all three population groups. Of 172 consumer product categories, 105 contained Prop 65-listed chemicals. Although these chemicals are known carcinogens and reproductive/developmental toxicants, they remain in widespread use. Manufacturers and regulators should prioritize product categories containing Prop 65-listed chemicals for reformulation or redesign to reduce human exposures and associated health risks.

Monitoring residues of pesticides in food in Brazil: A multiscale analysis of the main contaminants, dietary cancer risk estimative and mechanisms associated

Introduction

Pesticides pose a risk for cancer development and progression. People are continuously exposed to such substances by several routes, including daily intake of contaminated food and water, especially in countries that are highly pesticide consumers and have very permissive legislation about pesticide contamination as Brazil. This work investigated the relationship among pesticides, food contamination, and dietary cancer risk.

Methods

Analyzed two social reports from the Brazilian Government: the Program for Analysis of Residues of Pesticides in Food (PARA) and The National Program for Control of Waste and Contaminants (PNCRC).

Results and discussion

First, we characterized the main pesticide residues detected over the maximum limits allowed by legislation or those prohibited for use in food samples analyzed across the country. Based on this list, we estimated the dietary cancer risks for some of the selected pesticides. Finally, we searched for data about dietary cancer risks and carcinogenic mechanisms of each pesticide. We also provided a critical analysis concerning the pesticide scenario in Brazil, aiming to discuss the food contamination levels observed from a geographical, political, and public health perspective. Exposures to pesticides in Brazil violate a range of human rights when food and water for human consumption are contaminated.

Chemical Effects on Breast Development, Function, and Cancer Risk: Existing Knowledge and New Opportunities

Population studies show worrisome trends towards earlier breast development, difficulty in breastfeeding, and increasing rates of breast cancer in young women. Multiple epidemiological studies have linked these outcomes with chemical exposures, and experimental studies have shown that many of these chemicals generate similar effects in rodents, often by disrupting hormonal regulation. These endocrine-disrupting chemicals (EDCs) can alter the progression of mammary gland (MG) development, impair the ability to nourish offspring via lactation, increase mammary tissue density, and increase the propensity to develop cancer. However, current toxicological approaches to measuring the effects of chemical exposures on the MG are often inadequate to detect these effects, impairing our ability to identify exposures harmful to the breast and limiting opportunities for prevention. This paper describes key adverse outcomes for the MG, including impaired lactation, altered pubertal development, altered morphology (such as increased mammographic density), and cancer. It also summarizes evidence from humans and rodent models for exposures associated with these effects. We also review current toxicological practices for evaluating MG effects, highlight limitations of current methods, summarize debates related to how effects are interpreted in risk assessment, and make recommendations to strengthen assessment approaches. Increasing the rigor of MG assessment would improve our ability to identify chemicals of concern, regulate those chemicals based on their effects, and prevent exposures and associated adverse health effects.

Cheminformatics analysis of chemicals that increase estrogen and progesterone synthesis for a breast cancer hazard assessment

Factors that increase estrogen or progesterone (P4) action are well-established as increasing breast cancer risk, and many first-line treatments to prevent breast cancer recurrence work by blocking estrogen synthesis or action. In previous work, using data from an in vitro steroidogenesis assay developed for the U.S. Environmental Protection Agency (EPA) ToxCast program, we identified 182 chemicals that increased estradiol (E2up) and 185 that increased progesterone (P4up) in human H295R adrenocortical carcinoma cells, an OECD validated assay for steroidogenesis. Chemicals known to induce mammary effects in vivo were very likely to increase E2 or P4 synthesis, further supporting the importance of these pathways for breast cancer. To identify additional chemical exposures that may increase breast cancer risk through E2 or P4 steroidogenesis, we developed a cheminformatics approach to identify structural features associated with these activities and to predict other E2 or P4 steroidogens from their chemical structures. First, we used molecular descriptors and physicochemical properties to cluster the 2,012 chemicals screened in the steroidogenesis assay using a self-organizing map (SOM). Structural features such as triazine, phenol, or more broadly benzene ramified with halide, amine or alcohol, are enriched for E2 or P4up chemicals. Among E2up chemicals, phenol and benzenone are found as significant substructures, along with nitrogen-containing biphenyls. For P4up chemicals, phenol and complex aromatic systems ramified with oxygen-based groups such as flavone or phenolphthalein are significant substructures. Chemicals that are active for both E2up and P4up are enriched with substructures such as dihydroxy phosphanedithione or are small chemicals that contain one benzene ramified with chlorine, alcohol, methyl or primary amine. These results are confirmed with a chemotype ToxPrint analysis. Then, we used machine learning and artificial intelligence algorithms to develop and validate predictive classification QSAR models for E2up and P4up chemicals. These models gave reasonable external prediction performances (balanced accuracy ~ 0.8 and Matthews Coefficient Correlation ~ 0.5) on an external validation. The QSAR models were enriched by adding a confidence score that considers the chemical applicability domain and a ToxPrint assessment of the chemical. This profiling and these models may be useful to direct future testing and risk assessments for chemicals related to breast cancer and other hormonally-mediated outcomes.

Application of ToxCast/Tox21 data for toxicity mechanism-based evaluation and prioritization of environmental chemicals: Perspective and limitations

In response to the need to minimize the use of experimental animals, new approach methodologies (NAMs) using advanced technology have emerged in the 21st century. ToxCast/Tox21 aims to evaluate the adverse effects of chemicals quickly and efficiently using a high-throughput screening and to transform the paradigm of toxicity assessment into mechanism-based toxicity prediction. The ToxCast/Tox21 database, which contains extensive data from over 1400 assays with numerous biological targets and activity data for over 9000 chemicals, can be used for various purposes in the field of chemical prioritization and toxicity prediction. In this study, an overview of the database was explored to aid mechanism-based chemical prioritization and toxicity prediction. Implications for the utilization of the ToxCast/Tox21 database in chemical prioritization and toxicity prediction were derived. The research trends in ToxCast/Tox21 assay data were reviewed in the context of toxicity mechanism identification, chemical priority, environmental monitoring, assay development, and toxicity prediction. Finally, the potential applications and limitations of using ToxCast/Tox21 assay data in chemical risk assessment were discussed. The analysis of the toxicity mechanism-based assays of ToxCast/Tox21 will help in chemical prioritization and regulatory applications without the use of laboratory animals.

Development, Validation, and Application of a Human Reproductive Toxicity Prediction Model Based on Adverse Outcome Pathway

A growing number of environmental contaminants have been proved to have reproductive toxicity to males and females. However, the unclear toxicological mechanism of reproductive toxicants limits the development of virtual screening methods. By consolidating androgen (AR)-/estrogen receptors (ERs)-mediated adverse outcome pathways (AOPs) with more than 8000 chemical substances, we uncovered relationships between chemical features, a series of pathway-related effects, and reproductive apical outcomes─changes in sex organ weights. An AOP-based computational model named RepTox was developed and evaluated to predict and characterize chemicals' reproductive toxicity for males and females. Results showed that RepTox has three outstanding advantages. (I) Compared with the traditional models (37 and 81% accuracy, respectively), AOP significantly improved the predictive robustness of RepTox (96.3% accuracy). (II) Compared with the application domain (AD) of models based on small in vivo datasets, AOP expanded the ADs of RepTox by 1.65-fold for male and 3.77-fold for female, respectively. (III) RepTox implied that hydrophobicity, cyclopentanol substructure, and several topological indices (e.g., hydrogen-bond acceptors) were important, unbiased features associated with reproductive toxicants. Finally, RepTox was applied to the inventory of existing chemical substances of China and identified 2100 and 7281 potential toxicants to the male and female reproductive systems, respectively.