Exposure to 4,4'-DDE in visceral adipose tissue and weight loss in adolescents from the Teen-LABS cohort

OBJECTIVE

Dichlorodiphenyldichloroethylene (DDE), an obesogen accumulating in adipose tissue, is released into circulation with weight loss, although its impact is underexplored among adolescents. We tested the association using an integrative translational approach of epidemiological analysis among adolescents with obesity and in vitro measures exploring the impact of DDE on adipogenesis via preadipocytes.

METHODS

We included 63 participants from the Teen-Longitudinal Assessment of Bariatric Surgery (Teen-LABS) cohort. We assessed 4,4'-DDE in visceral adipose tissue at surgery and BMI and waist circumference at surgery and 0.5, 1, 3, and 5 years after. We conducted longitudinal analysis to estimate the interaction on weight loss between DDE and time since surgery. In vitro analysis quantified adipogenic differentiation in commercial human preadipocytes exposed to 4,4'-DDE via fluorescent staining and imaging.

RESULTS

A dose-response relationship was observed, with the low-exposure group having a greater reduction in BMI during the first year compared to higher-exposure groups and showing smaller regains compared to higher-exposure groups after the first year. In vitro analysis of preadipocytes treated with 4,4'-DDE during adipogenic differentiation for 12 days showed a concentration-dependent increase in lipid accumulation.

CONCLUSIONS

DDE could contribute to weight trajectory among adolescents undergoing bariatric surgery, potentially mediated via promoted adipogenesis in preadipocytes.

Perinatal triphenyl phosphate exposure induces metabolic dysfunctions through the EGFR/ERK/AKT signaling pathway: Mechanistic in vitro and in vivo studies

Triphenyl phosphate (TPhP), a widely used organophosphate-flame retardant, is ubiquitously found in household environments and may adversely affect human health. Evidence indicates that TPhP exposure causes metabolic dysfunctions in vivo; however, the underlying mechanism of such adverse effects has not been comprehensively investigated. Herein, we utilized two in vitro models including mouse and human preadipocytes to delineate adipogenic mechanisms of TPhP. The results revealed that both mouse and human preadipocytes exposed to TPhP concentration-dependently accumulated more fat through a significant upregulation of epidermal growth factor receptor (EGFR). We demonstrated that TPhP significantly promoted adipogenesis through the activation of EGFR/ERK/AKT signaling pathway as evident by a drastic reduction in adipogenesis of preadipocytes cotreated with inhibitors of EGFR and its major effectors. Furthermore, we confirmed the mechanism of TPhP-induced metabolic dysfunctions in vivo. We observed that male mice perinatally exposed to TPhP had a significant increase in adiposity, hepatic triglycerides, insulin resistance, plasma insulin levels, hypotension, and phosphorylated EGFR in gonadal fat. Interestingly, an administration of a potent and selective EGFR inhibitor significantly ameliorated the adverse metabolic effects caused by TPhP. Our findings uncovered a potential mechanism of TPhP-induced metabolic dysfunctions and provided implications on toxic metabolic effects posed by environmental chemicals.

Chronic Exposure to Low Levels of Parabens Increases Mammary Cancer Growth and Metastasis in Mice

Methylparaben (MP) and propylparaben (PP) are commonly used as food, cosmetic, and drug preservatives. These parabens are detected in the majority of US women and children, bind and activate estrogen receptors (ER), and stimulate mammary tumor cell growth and invasion in vitro. Hemizygous B6.FVB-Tg (MMTV-PyVT)634Mul/LellJ female mice (n = 20/treatment) were exposed to MP or PP at levels within the US Food and Drug Administration's "human acceptable daily intake." These paraben-exposed mice had increased mammary tumor volume compared with control mice (P < 0.001) and a 28% and 91% increase in the number of pulmonary metastases per week compared with the control mice, respectively (P < 0.0001). MP and PP caused differential expression of 288 and 412 mammary tumor genes, respectively (false discovery rate < 0.05), a subset of which has been associated with human breast cancer metastasis. Molecular docking and luciferase reporter studies affirmed that MP and PP bound and activated human ER, and RNA-sequencing revealed increased ER expression in mammary tumors among paraben-exposed mice. However, ER signaling was not enriched in mammary tumors. Instead, both parabens strongly impaired tumor RNA metabolism (eg, ribosome, spliceosome), as evident from enriched KEGG pathway analysis of differential mammary tumor gene expression common to both paraben treatments (MP, P < 0.001; PP, P < 0.01). Indeed, mammary tumors from PP-exposed mice had an increased retention of introns (P < 0.05). Our data suggest that parabens cause substantial mammary cancer metastasis in mice as a function of their increasing alkyl chain length and highlight the emerging role of aberrant spliceosome activity in breast cancer metastasis.

In Vitro characterization of the endocrine disrupting effects of per- and poly-fluoroalkyl substances (PFASs) on the human androgen receptor

Per- and poly-fluoroalkyl substances (PFASs) are used extensively in a broad range of industrial applications and consumer products. While a few legacy PFASs have been voluntarily phased out, over 5000 PFASs have been produced as replacements for their predecessors. The potential endocrine disrupting hazards of most emerging PFASs have not been comprehensively investigated. In silico molecular docking to the human androgen receptor (hAR) combined with machine learning techniques were previously applied to 5206 PFASs and predicted 23 PFASs bind the hAR. Herein, the in silico results were validated in vitro for the five candidate AR ligands that were commercially available. Three manufactured PFASs namely (9-(nonafluorobutyl)- 2,3,6,7-tetrahydro-1 H,5 H,11 H-pyrano[2,3-f]pyrido[3,2,1-ij]quinolin-11-one (NON), 2-(heptafluoropropyl)- 3-phenylquinoxaline (HEP), and 2,2,3,3,4,4,5,5,5-nonafluoro-N-(4-nitrophenyl)pentanamide (NNN) elicited significant antiandrogenic effects at relatively low concentrations. We further investigated the mechanism of AR inhibition and found that all three PFASs inhibited AR transactivation induced by testosterone through a competitive binding mechanism. We then examined the antiandrogenic effects of these PFASs on AR expression and its responsive genes. Consistently, these PFASs significantly decreased the expression of PSA and FKBP5 and increased the expression of AR, similar to the effects elicited by a known competitive AR inhibitor, hydroxyflutamide. This suggests they are competitive antagonists of AR activity and western blot analysis revealed these PFASs decreased intracellular AR protein in androgen sensitive human prostate cancer cells. Hence, the findings presented here corroborate our published in silico approach and indicate these emerging PFASs may adversely affect the human endocrine system.

Cell-Based Bioassay to Screen Environmental Chemicals and Human Serum for Total Glucocorticogenic Activity

Glucocorticoids are steroid hormones that have systemic effects that are mediated by the glucocorticoid receptor. Environmental chemicals that disrupt glucocorticoid receptor signaling and/or glucocorticoid homeostasis could adversely affect the health of human and nonhuman vertebrates. A major challenge in identifying environmental chemicals that alter glucocorticoid receptor signaling and/or glucocorticoid homeostasis is a lack of adequate screening methods. We developed a cell-based bioassay to measure total glucocorticogenic activity (TGA) of environmental chemicals and human serum. Human MDA-MB-231 breast cancer cells were stably transfected with a luciferase reporter gene driven by 3 tandem glucocorticoid-response elements. Dose-response curves for 6 glucocorticoids and 4 non-glucocorticoid steroid hormones were generated to evaluate the specificity of the bioassay. Cells were also optimized to measure TGA of 176 structurally diverse environmental chemicals and human serum samples in a high-throughput format. Reporter activity was glucocorticoid-specific and induced 400-fold by 1 μM dexamethasone. Furthermore, 3 of the screened chemicals (3,4,4'-trichlorocarbanilide, isopropyl-N-phenylcarbamate, and benzothiazole derivative 2-[4-chlorophenyl]-benzothiazole) potentiated cortisol-induced glucocorticoid receptor activity. Serum TGA estimates from the bioassay were highly correlated with a cortisol enzyme-linked immunosorbent assay. The present study establishes an in vitro method to rapidly screen environmental chemicals and human serum for altered glucocorticogenic activity. Future studies can utilize this tool to quantify the joint effect of endogenous glucocorticoids and environmental chemicals. Environ Toxicol Chem 2021;40:177-186. © 2020 SETAC.

Structure-based virtual screening of perfluoroalkyl and polyfluoroalkyl substances (PFASs) as endocrine disruptors of androgen receptor activity using molecular docking and machine learning

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) pose a substantial threat as endocrine disruptors, and thus early identification of those that may interact with steroid hormone receptors, such as the androgen receptor (AR), is critical. In this study we screened 5,206 PFASs from the CompTox database against the different binding sites on the AR using both molecular docking and machine learning techniques. We developed support vector machine models trained on Tox21 data to classify the active and inactive PFASs for AR using different chemical fingerprints as features. The maximum accuracy was 95.01% and Matthew's correlation coefficient (MCC) was 0.76 respectively, based on MACCS fingerprints (MACCSFP). The combination of docking-based screening and machine learning models identified 29 PFASs that have strong potential for activity against the AR and should be considered priority chemicals for biological toxicity testing.

Structure-based discovery of the endocrine disrupting effects of hydraulic fracturing chemicals as novel androgen receptor antagonists

Hydraulic fracturing (HF) technology is increasingly utilized for oil and gas extraction operations. The widespread use of HF has led to concerns of negative impacts on both the environment and human health. Indeed, the potential endocrine disrupting impacts of HF chemicals is one such knowledge gap. Herein, we used structure-based molecular docking to assess the binding affinities of 60 HF chemicals to the human androgen receptor (AR). Five HF chemicals had relatively high predicted AR binding affinity, suggesting the potential for endocrine disruption. We next assessed androgenic and antiandrogenic activities of these chemicals in vitro. Of the five candidate AR ligands, only Genapol®X-100 significantly modified AR transactivation. To better understand the structural effect of Genapol®X-100 on the potency of AR inhibition, we compared the antiandrogenic activity of Genapol®X-100 with that of its structurally similar chemical, Genapol®X-080. Interestingly, both Genapol®X-100 and Genapol®X-080 elicited an antagonistic effect at AR with 20% relative inhibitory concentrations of 0.43 and 0.89 μM, respectively. Furthermore, we investigated the mechanism of AR inhibition of these two chemicals in vitro, and found that both Genapol®X-100 and Genapol®X-080 inhibited AR through a noncompetitive mechanism. The effect of these two chemicals on the expression of AR responsive genes, e.g. PSA, KLK2, and AR, was also investigated. Genapol®X-100 and Genapol®X-080 altered the expression of these genes. Our findings heighten awareness of endocrine disruption by HF chemicals and provide evidence that noncompetitive antiandrogenic Genapol®X-100 could cause adverse endocrine health effects.

Plasma glucocorticogenic activity, race/ethnicity and alcohol intake among San Francisco Bay Area women

Racial and ethnic minorities are at higher risk for a variety of diseases. While sociodemographic and lifestyle factors contribute to racial/ethnic health disparities, the biological processes underlying these associations remain poorly understood. Stress and its biological consequences through the glucocorticoid receptor (GR) have been hypothesized to mediate adverse disease outcomes. In fasting morning samples of 503 control women from the San Francisco Bay Area Breast Cancer Study, we used a sensitive Chemical-Activated LUciferase gene eXpression (CALUX) assay to examine the association of sociodemographic and lifestyle factors with plasma glucocorticogenic (G) activity in three racial/ethnic groups. The G activity is a sensitive measure that reflects biological activity of total plasma glucocorticoids including cortisol and glucocorticoid-like compounds. Associations between G activity and sociodemographic and lifestyle factors were examined using multivariable linear regression models. Latina and non-Latina Black (NLB) women had 9% (P = 0.053) and 14% (P = 0.008) lower morning G activity than non-Latina White (NLW) women, respectively. Additionally, we replicated a previously reported association between G activity and alcohol intake (women who drank >10gms had 19% higher G activity than non-drinkers, P = 0.004) in Latina and NLB women. Further research should assess the association between G activity and health outcomes in a prospective cohort so as to characterize the relationship between total plasma G activity in pre-disease state and disease outcomes across different racial/ethnic populations.

SAT-722 Structure-Based Discovery of Hydraulic Fracturing Chemicals as Novel Androgen Receptor Antagonists

Hydraulic fracturing (HF) technology is increasingly utilized for oil and gas extraction operations. The widespread use of HF has led to concerns of potential negative impacts on both the environment and human health. Indeed, the potential endocrine disrupting impacts of HF chemicals is one such knowledge gap. Herein, we used structure-based molecular docking to assess the binding affinities of 60 HF chemicals used in California to the human androgen receptor (AR). Five HF chemicals had relatively high AR binding affinity, suggesting the potential to disrupt AR effects. We next assessed androgenic and antiandrogenic activities of these chemicals in vitro. Of the five candidate AR ligands, only Genapol^® X–100 was found to significantly reduce the AR transactivation by 22%. To better understand the structural effect of Genapol^® X–100 on the potency of receptor inhibition, we compared the antiandrogenic activity of Genapol^® X–100 with that of its structurally similar chemical, Genapol^® X–080. Interestingly, both Genapol^® X–100 and Genapol^® X–080 elicited a significant antagonistic effect with 20% relative inhibitory concentrations (RIC₂₀) of 0.43 and 0.89 μM, respectively. This indicated that Genapol^® X–100 was more potent in inhibiting AR than Genapol^® X–080, consistent with longer Genapol^® X–100 chain length causing greater potency of AR activity inhibition. Furthermore, we investigated the mechanism of AR inhibition of these two chemicals in vitro. The result revealed that both Genapol^® X–100 and Genapol^® X–080 inhibited AR through noncompetitive binding mechanism. The effects of these two chemicals on the expression of AR responsive genes such as PSA, KLK2, and AR were also investigated. Genapol^® X–100 and Genapol^® X–080 notably altered the expression of these genes at relatively low concentrations of 0.5 µM to 1 µM. Using these integrated in vitro and in silico approaches, we identified HF chemicals as novel noncompetitive AR antagonists. Our findings heighten awareness of endocrine disruption by HF chemicals and provide evidence that noncompetitive antiandrogenic Genapol^® X–100 could possibly cause adverse endocrine health effects in humans.

Structural Dynamics of Agonist and Antagonist Binding to the Androgen Receptor

Androgen receptor (AR) is a steroid hormone nuclear receptor which upon binding its endogenous androgenic ligands (agonists), testosterone and dihydrotestosterone (DHT), alters gene transcription, producing a diverse range of biological effects. Antiandrogens, such as the pharmaceuticals bicalutamide and hydroxyflutamide, act as agonists in the absence of androgens and as antagonists in their presence or in high concentration. The atomic level mechanism of action by agonists and antagonists of AR is less well characterized. Therefore, in this study, multiple 1 μs molecular dynamics (MD), docking simulations, and perturbation-response analyses were performed to more fully explore the nature of interaction between agonist or antagonist and AR and the conformational changes induced in the AR upon interaction with different ligands. We characterized the mechanism of the ligand entry/exit and found that helix-12 and nearby structural motifs respond dynamically in that process. Modeling showed that the agonist and antagonist/agonist form a hydrogen bond with Thr877/Asn705 and that this interaction is absent for antagonists. Agonist binding to AR increases the mobility of residues at allosteric sites and coactivator binding sites, while antagonist binding decreases mobility at these important sites. A new site was also identified as a potential surface for allosteric binding. These results shed light on the effect of agonists and antagonists on the structure and dynamics of AR.

Estrogenic activity, race/ethnicity, and Indigenous American ancestry among San Francisco Bay Area women

Estrogens play a significant role in breast cancer development and are not only produced endogenously, but are also mimicked by estrogen-like compounds from environmental exposures. We evaluated associations between estrogenic (E) activity, demographic factors and breast cancer risk factors in Non-Latina Black (NLB), Non-Latina White (NLW), and Latina women. We examined the association between E activity and Indigenous American (IA) ancestry in Latina women. Total E activity was measured with a bioassay in plasma samples of 503 women who served as controls in the San Francisco Bay Area Breast Cancer Study. In the univariate model that included all women with race/ethnicity as the independent predictor, Latinas had 13% lower E activity (p = 0.239) and NLBs had 35% higher activity (p = 0.04) compared to NLWs. In the multivariable model that adjusted for demographic factors, Latinas continued to show lower E activity levels (26%, p = 0.026), but the difference between NLBs and NLWs was no longer statistically significant (p = 0.431). An inverse association was observed between E activity and IA ancestry among Latina women (50% lower in 0% vs. 100% European ancestry, p = 0.027) consistent with our previously reported association between IA ancestry and breast cancer risk. These findings suggest that endogenous estrogens and exogenous estrogen-like compounds that act on the estrogen receptor and modulate E activity may partially explain racial/ethnic differences in breast cancer risk.

Abstract A53: Plasma glucocorticogenic activity differs by race/ethnicity and alcohol intake among San Francisco Bay Area women

Breast cancer mortality is higher among non-Hispanic Black (NHB) and Hispanic women than non-Hispanic White (NHW) women in the United States. While various sociodemographic and lifestyle factors contribute to racial/ethnic disparities in breast cancer, the biologic processes underlying these associations remain poorly understood. Cortisol, the predominant endogenous glucocorticoid present in humans, is secreted in a diurnal pattern with the highest concentration occurring shortly after waking followed by a steady decline throughout the day. A flattened diurnal cortisol pattern (e.g., due to lower morning and/or elevated evening cortisol levels) is often observed among chronically stressed individuals and has been linked to poorer survival among breast cancer patients. We examined the association between race/ethnicity and other breast cancer risk factors with glucocorticogenic (G) activity, a measure that reflects plasma cortisol levels, in 503 controls from the San Francisco Bay Area Breast Cancer Study (SFBCS, 329 Hispanic, 100 NHB and 74 NHW women) using a low-cost Chemical-Activated LUciferase gene eXpression (CALUX) assay. Associations between G activity and sociodemographic and lifestyle factors were examined using multivariable linear regression models. Hispanic and NHB women had 14% (P = 0.016) and 16% (P = 0.007) lower morning G activity than NHW women, respectively. Additionally, we replicated our previously reported association between G activity and alcohol intake (women who drank &gt;10 gm had 22% higher G activity than non-drinkers, P = 0.003). This association was only present in Hispanics and NHB. No statistically significant associations were observed between G activity and Indigenous American ancestry, body mass index, or neighborhood socioeconomic status. Our results indicate that NHB and Hispanic women may have a blunted cortisol awakening response potentially due to chronic stress. The increase in morning G activity observed with higher alcohol intake in Hispanics and NHB might reflect the use of alcohol as a stress-coping mechanism. Further research should assess the association between G activity and breast cancer survival in biospecimens from a prospective cohort so as to characterize the relationship between prediagnosis chronic stress and breast cancer outcome across different racial/ethnic groups.

Citation Format: Rosemarie M. de la Rosa, Sylvia S. Sanchez, Phum Tachachartvanich, Heather Ruiz, Scarlett Lin Gomez, Esther M. John, Martyn T. Smith, Laura Fejerman. Plasma glucocorticogenic activity differs by race/ethnicity and alcohol intake among San Francisco Bay Area women [abstract]. In: Proceedings of the Tenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2017 Sep 25-28; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2018;27(7 Suppl):Abstract nr A53.

Abstract PR05: Estrogenic activity is associated with race/ethnicity and Indigenous American ancestry among San Francisco Bay Area women

The incidence of breast cancer in the U.S. varies by race/ethnicity. Furthermore, in Hispanic women, breast cancer risk is higher among women with low Indigenous American ancestry compared to those with high Indigenous American ancestry and in U.S.-born compared to foreign-born women. In a previous pilot study among foreign-born and U.S.-born Mexican women, we found that plasma estrogenic (E) activity was associated with genetic ancestry and years of U.S. residence, suggesting the possibility of a hormone-related pathway for the observed differences in breast cancer risk. In the present study, we examined the association between E activity and genetic ancestry in a larger sample of Hispanic women. We also evaluated the association between E activity, demographic factors, and breast cancer risk in non-Hispanic Black (NHB) and non-Hispanic White (NHW) women. We utilized a receptor-mediated Chemical-Activated Luciferase gene eXpression (CALUX) assay for the assessment of total activity profiles against estrogen receptors (ER) in human plasma, which captures levels of both endogenous and exogenous estrogenic compounds. Results were expressed in relative light units (RLUs), with higher RLU values reflecting greater E activity in plasma. ER activation was measured in plasma samples of 329 Hispanic, 100 NHBs, and 74 NHW women who participated as controls in the San Francisco Bay Area Breast Cancer Study (SFBCS). The participants ranged in age from 35 to 79 years, though the study was composed predominantly of postmenopausal women. Multivariable regression models included race/ethnicity, age at blood draw, height, body mass index (BMI), neighborhood socioeconomic status (SES), and alcohol intake. In the univariate model that included all women (n=503) and race/ethnicity as the independent predictor, Hispanics had 24% lower E activity (p=0.061) and NHBs had 36% higher activity (p=0.047) compared to NHWs. In the multivariable model, Hispanics still showed lower E activity levels (34%, p=0.009), but the difference with NHBs and NHWs was no longer statistically significant (p=0.493). After adjustment for levels of two endogenous estrogens, estradiol and estrone, in a subset of samples (n=260), Hispanics continued to show 20% lower E activity compared to NHWs. In addition, when BMI is categorized into tertiles consisting of normal (&lt;25 kg/m2), overweight (25-30 kg/m2), and obese (BMI &gt;30 kg/m2) women, we found that obese women had 73% higher E activity compared to those with normal BMI (p&lt;0.001) and overweight women had 46% higher activity (p=0.006). Among the Hispanic women, we confirmed the previously observed negative association between E activity and Indigenous American ancestry, which is consistent with the observation that Hispanic women with high Indigenous American ancestry have lower risk of developing breast cancer. Overall, our study suggests that observed associations between race/ethnicity, genetic ancestry and BMI with breast cancer risk could be partly due to the mediating effect of endogenous estrogens as well as to the effect of exogenous estrogen-like compounds.

Citation Format: Sylvia S. Sanchez, Phum Tachachartvanich, Heather Ruiz, Frank Z. Stanczyk, Scarlett Lin Gomez, Esther M. John, Martyn T. Smith, Laura Fejerman. Estrogenic activity is associated with race/ethnicity and Indigenous American ancestry among San Francisco Bay Area women [abstract]. In: Proceedings of the Tenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2017 Sep 25-28; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2018;27(7 Suppl):Abstract nr PR05.

Assessment of the Endocrine-Disrupting Effects of Trichloroethylene and Its Metabolites Using in Vitro and in Silico Approaches

Trichloroethylene (TCE) is a ubiquitous environmental contaminant, which may have effects on both ecosystem and human health. TCE has been reported to cause several toxic effects, but little effort has been made to assess the ecological risks of TCE or its major metabolites: trichloroethanol (TCOH), trichloroacetic acid, and oxalic acid (OA). In this study, the endocrine-disrupting potential of TCE and its metabolites were investigated using in vitro and in silico approaches. We examined alterations in the steroidogenesis pathway using the NCI-H295R cell line and utilized receptor-mediated luciferase reporter cell lines to identify effects on estrogen and androgen receptors. Molecular docking was also used to explore chemical interactions with these receptors. All test chemicals except OA significantly increased 17β-estradiol production which can be attributed to an up-regulation of 17β-hydroxysteroid dehydrogenase. Moreover, TCOH exhibited significant antiestrogenic activity with a RIC20 (20% relative inhibitory concentration) of 3.7 × 10-7 M. Molecular docking simulation supported this finding with lower docking scores for TCOH, indicating that hydrogen bonds may stabilize the interaction between TCOH and the estrogen receptor binding pocket. These findings suggest that TCE contamination poses an endocrine-disrupting threat, which has implications for both ecological and human health.

Direct detection of nitrotyrosine-containing proteins using an aniline-based oxidative coupling strategy

A convenient two-step method is described for the detection of nitrotyrosine-containing proteins. First, nitrotyrosines are reduced to aminophenols using sodium dithionite. Following this, an oxidative coupling reaction is used to attach anilines bearing fluorescence reporters or affinity probes. Features of this approach include fast reaction times, pmol-level sensitivity, and excellent chemoselectivity.

Association of lifestyle and demographic factors with estrogenic and glucocorticogenic activity in Mexican American women

Breast cancer risk is higher in US-born than in foreign-born Hispanics/Latinas and also increases with greater length of US residency. It is only partially known what factors contribute to these patterns of risk. To gain new insights, we tested the association between lifestyle and demographic variables and breast cancer status, with measures of estrogenic (E) and glucocorticogenic (G) activity in Mexican American women. We used Chemical-Activated LUciferase gene eXpression assays to measure E and G activity in total plasma from 90 Mexican American women, without a history of breast cancer at the time of recruitment, from the San Francisco Bay Area Breast Cancer Study. We tested associations of nativity, lifestyle and sociodemographic factors with E and G activity using linear regression models. We did not find a statistically significant difference in E or G activity by nativity. However, in multivariable models, E activity was associated with Indigenous American ancestry (19% decrease in E activity per 10% increase in ancestry, P = 0.014) and with length of US residency (28% increase in E activity for every 10 years, P = 0.035). G activity was associated with breast cancer status (women who have developed breast cancer since recruitment into the study had 21% lower G activity than those who have not, P = 0.054) and alcohol intake (drinkers had 25% higher G activity than non-drinkers, P = 0.015). These associations suggest that previously reported breast cancer risk factors such as genetic ancestry and alcohol intake might in part be associated with breast cancer risk through mechanisms linked to the endocrine system.

Chlorpyrifos promotes colorectal adenocarcinoma H508 cell growth through the activation of EGFR/ERK1/2 signaling pathway but not cholinergic pathway

Aside from the effects on neuronal cholinergic system, epidemiological studies suggest an association between chlorpyrifos (CPF) exposure and cancer risk. This in vitro study examined the effects of CPF and its toxic metabolite, chlorpyrifos oxon (CPF-O), on the growth of human colorectal adenocarcinoma H508, colorectal adenocarcinoma HT-29, normal colon epithelial CCD841, liver hepatocellular carcinoma HepG2, and normal liver hepatocyte THLE-3 cells. The results showed that CPF (5-100 μM) concentration-dependently increased viability of H508 and CCD841 cells in serum-free conditions. This increasing trend was not found in HT-29, HepG2 and THLE-3 cells. In contrast, CPF-O (50-100 μM) reduced the viability of all cell lines. Cell cycle analysis showed the induction of cells in the S phase, and EdU incorporation assay revealed the induction of DNA synthesis in CPF-treated H508 cells indicating that CPF promotes cell cycle progression. Despite the observation of acetylcholinesterase activity inhibition and reactive oxygen species (ROS) generation, atropine (a non-selective muscarinic acetylcholine receptor antagonist) and N-acetylcysteine (a potent antioxidant) failed to inhibit the growth-promoting effect of CPF. CPF increased the phosphorylation of epidermal growth factor receptor (EGFR) and its downstream effector, extracellular signal regulated kinase (ERK1/2), in H508 cells. AG-1478 (a specific EGFR tyrosine kinase inhibitor) and U0126 (a specific MEK inhibitor) completely mitigated the growth promoting effect of CPF. Altogether, these results suggest that EGFR/ERK1/2 signaling pathway but not cholinergic pathway involves in CPF-induced colorectal adenocarcinoma H508 cell growth.

Abstract B40: Estrogen receptor activity levels among Mexican American women

Background: Breast cancer incidence varies greatly worldwide. In particular, the incidence of breast cancer in Mexico is lower than that in the U.S. Individuals of Hispanic or Latino origin in the U.S. represent 16% of the total population and 38% of the population of California. The migratory experience is accompanied by changes in lifestyle and environmental exposures, which in turn modify the individual's internal chemical environment. We expect that understanding the reasons behind breast cancer development in this seemingly protected population will be informative about relevant exposures that affect the probability of developing this disease more generally. Enzyme activation by exposure to hormone receptor disrupting compounds can lead to increased hormone catabolism, and compromise hormone signaling. Breast cancer is directly affected by the presence of endogenously produced hormones and likely also by hormone-like compounds of exogenous origin. We, therefore, used an untargeted cell-based assay to measure estrogen receptor activity among 90 Mexican American women from the San Francisco Bay Area Breast Cancer Study (SFBCS), 15 of whom developed breast cancer after blood sample collection.

Methods: The estrogen receptor-mediated chemical-activated luciferase gene expression (ER-CALUX) assay was used to assess the presence of estrogenic substances in archived plasma for 90 U.S. Latina women. The plate design included multiple reference samples placed across and within plates. We first fitted a linear mixed effects model to the data including the technical sources of variation (plate as a random effect and row, column, row + column and row x column as fixed effects) and an indicator variable, to capture the distinct nature of the reference sample. Given that for each sample we had 4 measures of activity, we then fitted a linear mixed effect model using the residuals for the first regression, taking the individual level of variation into account, and including the following explanatory variables: case/control status, proportion of Indigenous American ancestry, menopausal status, use of hormone replacement therapy, use of oral contraceptives, socioeconomic status, education, body mass index and daily alcohol intake.

Results: We did not observe a statistically significant difference between cases and controls in the estrogen receptor activity levels (p=0.12). We found a statistically significant difference in estrogen receptor activity levels by menopausal status in the expected direction, with mean equivalent estradiol level being 498±48 pM in pre-menopausal and 125±60 pM in post-menopausal women (p=0.001). Daily alcohol consumption also showed a statistically significant association with estrogen receptor activity levels (0.001), which disappeared when 1 woman with extremely high levels of daily alcohol consumption (75 Grams/daily) was excluded from the analysis (p=0.567).

Conclusion: Despite the noisy nature of the untargeted measure of estrogen receptor activity, we were able to develop an experimental design that could capture technical variability and that allowed us to observed the expected association between levels of estrogen receptor activity and menopausal status in archived samples of U.S. Latina women. The present study included 15 women who developed breast cancer after specimen collection and 75 controls, and therefore was underpowered to detect modest differences between the two groups in estrogen receptor activity levels. Further studies are planned to examine this endpoint in a much larger sample set.

Citation Format: Laura Fejerman, Reuben Thomas, Sylvia Sanchez, Phum Tachachartvanich, Esther M. John, Martyn Smith. Estrogen receptor activity levels among Mexican American women. [abstract]. In: Proceedings of the Seventh AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 9-12, 2014; San Antonio, TX. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2015;24(10 Suppl):Abstract nr B40.