Pesticide exposure and increased breast cancer risk in women population studies

Pesticide exposure is emerging as a risk factor for various human diseases. Breast cancer (BC) is a multifactorial disease with known genetic and non-genetic risk factors. Most BC cases are attibutable to non-genetic risk factors, with a history of adverse environmental exposures playing a significant role. Pesticide exposure can occur at higher levels in female populations participating in rural activities such as spraying of pesticides in the field, unprotected handling of pesticides at home, and washing of contaminated clothes. Exposure can also be significant in the drinking water of certain populations. Here, we reviewed the literature on women's exposure to pesticides and the risk of BC. We summarize the main links between pesticide exposure and BC and discuss the role of dose and exposure context, as well as potential mechanisms of toxicity. Overall, reports reviewed here have documented stronger associations between higher levels of exposure and BC risk, including documenting direct and acute pesticide exposure in certain female populations. However, discrepancies among studies regarding dose and mode of exposure may result in misunderstandings about the risks posed by pesticide exposure. Plausible mechanisms linking pesticides to breast cancer risk include their impacts as endocrine disruptors, as well as their roles as genotoxic agents, and modulators of the epigenome. Besides establishing links between pesticide exposure and breast cancer, the literature also highlights the critical need to understand the routes and doses of women's exposure to pesticides and the specific associations and mechanisms that are determinants of disease etiology and prognosis.

OMICs Signatures Linking Persistent Organic Pollutants to Cardiovascular Disease in the Swedish Mammography Cohort

Cardiovascular disease (CVD) development may be linked to persistent organic pollutants (POPs), including organochlorine compounds (OCs) and perfluoroalkyl and polyfluoroalkyl substances (PFAS). To explore underlying mechanisms, we investigated metabolites, proteins, and genes linking POPs with CVD risk. We used data from a nested case-control study on myocardial infarction (MI) and stroke from the Swedish Mammography Cohort - Clinical (n = 657 subjects). OCs, PFAS, and multiomics (9511 liquid chromatography-mass spectrometry (LC-MS) metabolite features; 248 proteins; 8110 gene variants) were measured in baseline plasma. POP-related omics features were selected using random forest followed by Spearman correlation adjusted for confounders. From these, CVD-related omics features were selected using conditional logistic regression. Finally, 29 (for OCs) and 12 (for PFAS) unique features associated with POPs and CVD. One omics subpattern, driven by lipids and inflammatory proteins, associated with MI (OR = 2.03; 95% CI = 1.47; 2.79), OCs, age, and BMI, and correlated negatively with PFAS. Another subpattern, driven by carnitines, associated with stroke (OR = 1.55; 95% CI = 1.16; 2.09), OCs, and age, but not with PFAS. This may imply that OCs and PFAS associate with different omics patterns with opposite effects on CVD risk, but more research is needed to disentangle potential modifications by other factors.

Genetic Variations in Cytochrome P450 1A1 and 1B1 Genes in a Cohort of Patients from Iraq Diagnosed with Breast Cancer

Breast cancer is the most prevalent malignant neoplasm in females. Genetic variations in the xenobiotic metabolising cytochrome enzymes; Family 1 Subfamily A Member 1 (CYP1A1) and Family 1 Subfamily B Member 1 (CYP1B1) might play a role in the individual susceptibility to breast cancer and its prognosis. The goal of this study is to estimate the incidence of single nucleotide polymorphisms (SNPs) in CYP1A1 (rs1048943, Ile462VaI, and rs4646903/MSP1) and in CYP1B1 (rs1056836, Leu432Val) genes in patients with breast cancer. This case-control study included 180 female patients with breast cancer and 180 healthy control subjects from Kirkuk/Iraq. Genomic DNA was extracted from venous blood samples and tested for SNPs by the direct DNA sequencing technique. A statistical analysis was done to identify if there is any association between SNPs and the increasing odd of breast cancer and its stage, grade and molecular subtype at diagnosis. The common (reference) genotype of CYP1A1 gene rs1048943 is AA. The AG and GG variant genotypes were significantly more common in the breast cancer patients and conferred an increased odd of breast cancer and its later stages (stages III and IV) and poor differentiation (P < .01) but not with the molecular subtypes. The common genotype of CYP1A1 rs4646903 is TT. The variant genotypes TC and CC are not associated either with increased risk of breast cancer (P > .05) or with its stage, grade or molecular subtypes (P > .05). The GG genotype of CYP1B1 rs1056836 was the common genotype. The CG and CC variant genotypes were not associated with the increased risks of breast cancer (P > .05) or its stage, grade or molecular subtypes (P > .05). In conclusion, variants genotypes of CYP1A1 rs1048943 might play a role in breast cancer pathogenesis and prognosis and can have a place in cancer screening and tailored medicine in the future in the Iraqi population. Future larger scale studies including other genes might help to better understand the role of the SNP in breast risk and its prognosis.

Variation in biomarker levels of metals, persistent organic pollutants, and omega-3 fatty acids in association with genetic polymorphisms among Inuit in Nunavik, Canada

BACKGROUND

Biomarker measures of contaminant exposure and nutrient status can help increase understanding of the risks and benefits associated with the consumption of traditional foods by Inuit. While gene-environment and gene-nutrient interactions may help explain variations in biomarker measures, the role of genetic polymorphisms is largely understudied especially for vulnerable sub-populations.

OBJECTIVE

The aim of this study was to characterize the relationship between single nucleotide polymorphisms (SNPs) in key genes and blood concentrations of environmental chemicals and nutrients among Inuit.

METHODS

Blood samples from 665 individuals who participated in the Qanuippitaa Survey (Nunavik, Canada) in 2004 were analyzed for toxicants and nutrients. DNA was extracted and 140 SNPs in classes relevant to the toxicokinetics and/or toxicodynamics of the target contaminants and nutrients, and/or are involved in cardiovascular health and lipid metabolism were genotyped using the Sequenom iPLEX Gold platform.

RESULTS

Geometric means (μg/L) of mercury (Hg), cadmium (Cd), lead (Pb), DDE, PCB-153, and selenium (Se) were 11.1, 2.8, 39.9, 2.9, 1.1 and 301.2, respectively. Red blood cell membrane levels of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) were 5.1%/total fatty acid (TFA) and 1.3%/TFA respectively. Out of 106 SNPs which met our inclusion criteria, biomarker levels for Hg, Cd, Pb, DDE, PCB-153, DHA, and EPA differed (p < 0.05) by genotype for 20, 13, 12, 19, 21, 9 and 8 SNPs, respectively. Following Bonferroni correction (p < 0.0005), only 9 SNPs remained significant (rs2274976 in MTHFR, rs174602 in FADS2, rs7115739 and rs74771917 in FADS3, rs713041 in GPX4, rs2306283 and rs4149056 in SLCO1B1, rs1885301 in ABCC2/MRP2, and rs4244285 in CYP2C19; 5 associated with Hg, 2 with Pb, 2 with DDE, 4 with PCB-153, 1 with DHA).

CONCLUSIONS

The findings suggest that polymorphisms in environmentally-responsive genes can influence biomarker levels of key toxicants and nutrients. While there are no immediate clinical or public health implications of these findings, we believe that such gene-environment and gene-nutrient studies provide a foundation that will inform and provide direction to future studies.

PFAS and cancer, a scoping review of the epidemiologic evidence

BACKGROUND

The number of studies addressing per- and polyfluoroalkyl substances (PFAS) and cancer is increasing. Many communities have had water contaminated by PFAS, and cancer is one of the important community concerns related to PFAS exposure.

OBJECTIVES

We critically reviewed the evidence relating to PFAS and cancer from an epidemiologic standpoint to highlight directions for future research that would be the most likely to meaningfully increase knowledge.

METHODS

We conducted a search in PubMed for studies of cancer and PFAS (through 9/20/2020). We identified epidemiologic studies that provided a quantitative estimate for some measure of the association between PFAS and cancer. Here, we review that literature, including several aspects of epidemiologic study design that impact the usefulness of study results.

RESULTS

We identified 16 cohort (or case-cohort) studies, 10 case-control studies (4 nested within cohorts and 6 non-nested), 1 cross sectional study and 1 ecologic study. The cancer sites with the most evidence of an association with PFAS are testicular and kidney cancer. There are also some suggestions in a few studies of an association with prostate cancer, but the data are inconsistent.

DISCUSSION

Each study's design has strengths and limitations. Weaknesses in study design and methods can, in some cases, lead to questionable associations, but in other cases can make it more difficult to detect true associations, if they are present. Overall, the evidence for an association between cancer and PFAS remains sparse. A variety of studies with different strengths and weaknesses can be helpful to clarify associations between PFAS and cancer. Long term follow-up of large-sized cohorts with large exposure contrasts are most likely to be informative.

Environmental exposures and breast cancer risk in the context of underlying susceptibility: A systematic review of the epidemiological literature

BACKGROUND

The evidence evaluating environmental chemical exposures (ECE) and breast cancer (BC) risk is heterogeneous which may stem in part as few studies measure ECE during key BC windows of susceptibility (WOS). Another possibility may be that most BC studies are skewed towards individuals at average risk, which may limit the ability to detect signals from ECE.

OBJECTIVES

We reviewed the literature on ECE and BC focusing on three types of studies or subgroup analyses based on higher absolute BC risk: BC family history (Type 1); early onset BC (Type 2); and/or genetic susceptibility (Type 3).

METHODS

We systematically searched the PubMed database to identify epidemiologic studies examining ECE and BC risk published through June 1, 2019.

RESULTS

We identified 100 publications in 56 unique epidemiologic studies. Of these 56 studies, only 2 (3.6%) were enriched with BC family history and only 11% of studies (6/56) were specifically enriched with early onset cases. 80% of the publications from these 8 enriched studies (Type 1: 8/10 publications; Type 2: 8/10 publications) supported a statistically significant association between ECE and BC risk including studies of PAH, indoor cooking, NO₂, DDT; PCBs, PFOSA; metals; personal care products; and occupational exposure to industrial dyes. 74% of Type 3 publications (20/27) supported statistically significant associations for PAHs, traffic-related air pollution, PCBs, phthalates, and PFOSAs in subgroups of women with greater genetic susceptibility due to variants in carcinogen metabolism, DNA repair, oxidative stress, cellular apoptosis and tumor suppressor genes.

DISCUSSION

Studies enriched for women at higher BC risk through family history, younger age of onset and/or genetic susceptibility consistently support an association between an ECE and BC risk. In addition to measuring exposures during WOS, designing studies that are enriched with women at higher absolute risk are necessary to robustly measure the role of ECE on BC risk.

Serum Levels of Commonly Detected Persistent Organic Pollutants and Per- and Polyfluoroalkyl Substances (PFASs) and Mammographic Density in Postmenopausal Women

There are little epidemiological data on the impact of persistent organic pollutants (POPs) and endocrine disruptors on mammographic density (MD), a strong predictor of breast cancer. We assessed MD in 116 non-Hispanic white post-menopausal women for whom serum concentrations of 23 commonly detected chemicals including 3 polybrominated diphenyl ethers (PBDEs), 8 per- and polyfluoroalkyl substances (PFASs), and 12 polychlorinated biphenyls (PCBs) had been measured. Linear regression analyses adjusting for potential confounders were used to examine the associations between the levels of the chemical compounds, modeled as continuous and dichotomized (above/below median) variables, and square-root-transformed MD. None of the associations were statistically significant after correcting for multiple testing. Prior to correction for multiple testing, all chemicals with un-corrected p-values < 0.05 had regression coefficients less than zero, suggesting inverse associations between increased levels and MD, if any. The smallest p-value was observed for PCB-153 (regression coefficient for above-median vs. below-median levels: −0.87, un-corrected p = 0.008). Neither parity nor body mass index modified the associations. Our results do not support an association between higher MD and serum levels of PBDEs, PCBs, or PFASs commonly detected in postmenopausal women.

Associations between endocrine disrupting chemicals and equine metabolic syndrome phenotypes

Equine Metabolic Syndrome (EMS) is characterized by abnormalities in insulin regulation, increased adiposity and laminitis, and has several similarities to human metabolic syndrome. A large amount of environmental variability in the EMS phenotype is not explained by commonly measured factors (diet, exercise, and season), suggesting that other environmental factors play a role in EMS development. Endocrine disrupting chemicals (EDCs) are associated with metabolic syndrome and other endocrine abnormalities in humans. This led us to hypothesize that EDCs are detectable in horse plasma and play a role in the pathophysiology of EMS. EDCs acting through the aryl hydrocarbon and estrogen receptors, were measured in plasma of 301 horses from 32 farms. The median (range) TEQ (2,3,7,8-TCDD equivalent) and EEQ (17β-estradiol equivalent) were 19.29 pg/g (0.59-536.36) and 10.50 pg/ml (4.35-15000.00), respectively. TEQ was negatively associated with plasma fat extracted and batch analyzed. EEQ was positively associated with pregnancy and batch analyzed, and negatively associated with being male and superfund score ≤100 miles of the farm. Of particular interest, serum glucose and insulin, glucose and insulin post oral sugar challenge, and leptin concentrations were associated with EEQ, and serum triglyceride concentration was associated with TEQ. Overall, we demonstrated that EDCs are present in the plasma of horses and may explain some of the environmental variability in measured EMS phenotypes. This is the first example of EDCs being associated with clinical disease phenotype components in domestic animals.