Faculty Bibliography

OBJECTIVE:To investigate the specific and combined effects of personal concentrations of some per- and polyfluoroalkyl substances (PFAS), other persistent organic pollutants (POPs), and chemical elements -measured in individuals' blood several years before the pandemic- on the development of SARS-CoV-2 infection and COVID-19 disease in the general population. METHODS:We conducted a prospective cohort study in 240 individuals from the general population of Barcelona. PFAS, other POPs, and chemical elements were measured in plasma, serum, and whole blood samples, respectively, collected in 2016-2017. PFAS were analyzed by liquid chromatography-triple quadrupole mass spectrometry. SARS-CoV-2 infection was detected by rRT-PCR in nasopharyngeal swabs and/or antibody serology in blood samples collected in 2020-2021. RESULTS:No individual PFAS nor their mixtures were significantly associated with SARS-CoV-2 seropositivity or COVID-19 disease. Previously identified mixtures of POPs and elements (Porta et al., 2023) remained significantly associated with seropositivity and COVID-19 when adjusted for PFAS (all OR > 4 or p < 0.05). Nine chemicals comprised mixtures associated with COVID-19: thallium, ruthenium, lead, benzo[b]fluoranthene, DDD, other DDT-related compounds, manganese, tantalum, and aluminium. And nine chemicals comprised the mixtures more consistently associated with SARS-CoV-2 seropositivity: thallium, ruthenium, lead, benzo[b]fluoranthene, DDD, gold, and (protectively) selenium, indium, and iron. CONCLUSIONS:The PFAS studied were not associated with SARS-CoV-2 seropositivity or COVID-19. The results confirm the associations between personal blood concentrations of some POPs and chemical elements and the risk of COVID-19 and SARS-CoV-2 infection in what remains the only prospective and population-based cohort study on the topic. Mixtures of POPs and chemical elements may contribute to explain the heterogeneity in the risks of SARS-CoV-2 infection and COVID-19 in the general population.

BACKGROUND:There are conflicting data on whether nonalcoholic fatty liver disease (NAFLD) is associated with susceptibility to pancreatic cancer (PC). Using Mendelian randomization (MR), we investigated the relationship between genetic predisposition to NAFLD and risk for PC. METHODS:Data from genome-wide association studies within the Pancreatic Cancer Cohort Consortium (PanScan; cases n=5090, controls n=8733) and the Pancreatic Cancer Case Control Consortium (PanC4; cases n=4,163, controls n=3,792) were analyzed. We used data on 68 genetic variants with four different MR methods (inverse variance weighting [IVW], MR-Egger, simple median, and penalized weighted median) separately to predict genetic heritability of NAFLD. We then assessed the relationship between each of the four MR methods and PC risk, using logistic regression to calculate odds ratios (ORs) and 95% confidence intervals (CIs), adjusting for PC risk factors, including obesity and diabetes. RESULTS:No association was found between genetically predicted NAFLD and PC risk in the PanScan or PanC4 samples (e.g., PanScan, IVW OR=1.04, 95% CI: 0.88-1.22, MR-Egger OR=0.89, 95% CI: 0.65-1.21; PanC4, IVW OR=1.07, 95% CI: 0.90-1.27, MR-Egger OR=0.93, 95% CI: 0.67-1.28). None of the four MR methods indicated an association between genetically predicted NAFLD and PC risk in either sample. CONCLUSIONS:Genetic predisposition to NAFLD is not associated with PC risk. IMPACT/CONCLUSIONS:Given the close relationship between NAFLD and metabolic conditions, it is plausible that any association between NAFLD and PC might reflect host metabolic perturbations (e.g., obesity, diabetes, or metabolic syndrome) and does not necessarily reflect a causal relationship between NAFLD and PC.

Citizens deserve regulatory changes and policies more sensitive to the current needs of humans, the climate, and nature. In this work we draw on prior experiences of preventable human suffering and economic losses caused by delayed regulation of legacy and emerging pollutants. Heightened awareness of environmental health problems is necessary among health professionals, the media, and citizens' organizations. Improved translation from research to the clinical world and to policy is critical to reduce the population burden of diseases caused by exposure to endocrine disruptors and other environmental chemicals. Numerous lessons can be learned from science-to-policy processes built for "old pollutants" (as persistent organic pollutants, heavy metals, tributyltin), as well as from current trends regarding the regulation of non-persistent chemicals, such as the prototypical endocrine disruptor bisphenol A. We end discussing relevant pieces of the puzzle to tackle the environmental and regulatory challenges faced by our societies.

Knowledge on the role in cancer etiology of environmental exposures as pesticides is a pre-requisite for primary prevention. We review 62 epidemiological studies on exposure to pesticides and cancer risk in humans published from 2017 to 2021, with emphasis on new findings, methodological approaches, and gaps in the existing literature. While much of the recent evidence suggests causal relationships between pesticide exposure and cancer, the strongest evidence exists for acute myeloid leukemia (AML) and colorectal cancer (CRC), diseases in which the observed associations were consistent across several studies, including high quality prospective studies and those using biomarkers for exposure assessment, with some observing dose-response relationships. Though high-quality studies have been published since the IARC monograph on organophosphate insecticides in 2017, there are still gaps in the literature on carcinogenic evidence in humans for a large number of pesticides. To further knowledge, we suggest leveraging new techniques and methods to increase sensitivity and precision of exposure assessment, incorporate multi-omics data, and investigate more thoroughly exposure to chemical mixtures. There is also a strong need for better and larger population-based cohort studies that include younger and non-occupationally exposed individuals, particularly during developmental periods of susceptibility. Though the existing evidence has limitations, as always in science, there is sufficient evidence to implement policies and regulatory action that limit pesticide exposure in humans and, hence, further prevent a significant burden of cancers.

BACKGROUND:Findings and limitations of previous studies on persistent organic pollutants (POPs) and pancreatic cancer risk support conducting further research in prospective cohorts. METHODS:We conducted a prospective case-control study nested within the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. Participants were 513 pancreatic cancer cases and 1020 matched controls. Concentrations of 22 POPs were measured in plasma collected at baseline. RESULTS:Some associations were observed at higher concentrations of p, p'-DDT, trans-nonachlor, β-hexachlorocyclohexane and the sum of six organochlorine pesticides and of 16 POPs. The odds ratio (OR) for the upper quartile of trans-nonachlor was 1.55 (95% confidence interval 1.06-2.26; P for trend = 0.025). Associations were stronger in the groups predefined as most valid (participants having fasted >6 h, with microscopic diagnostic confirmation, normal weight, and never smokers), and as most relevant (follow-up ≥10 years). Among participants having fasted >6 h, the ORs were relevant for 10 of 11 exposures. Higher ORs were also observed among cases with microscopic confirmation than in cases with a clinical diagnosis, and among normal-weight participants than in the rest of participants. Among participants with a follow-up ≥10 years, estimates were higher than in participants with a shorter follow-up (for trans-nonachlor: OR = 2.14, 1.01 to 4.53, P for trend = 0.035). Overall, trans-nonachlor, three PCBs and the two sums of POPs were the exposures most clearly associated with pancreatic cancer risk. CONCLUSIONS:Individually or in combination, most of the 22 POPs analysed did not or only moderately increased the risk of pancreatic cancer.

Trace elements such as cadmium, arsenic, zinc or selenium increase or decrease risk of a wide range of human diseases. Their levels in toenails may provide a measure of mid-term intake of trace elements for studies in humans. However, in biologically and clinically aggressive diseases as pancreatic cancer, the progression of the disease could modify such concentrations and produce reverse causation bias. The aim was to analyze the influence of specific time intervals between several clinical events and the collection of toenails upon concentrations of trace elements in patients with pancreatic cancer. Subjects were 118 incident cases of pancreatic adenocarcinoma prospectively recruited in eastern Spain. Toenails were collected at cancer diagnosis, and soon thereafter interviews were conducted. Information on cancer signs and symptoms was obtained from medical records and patient interviews. Levels of 12 trace elements were determined in toenail samples by inductively coupled plasma mass spectrometry. General linear models adjusting for potential confounders were applied to analyze relations between log concentrations of trace elements and the time intervals, including the interval from first symptom of cancer to toenail collection (iST). Toenail concentrations of the 12 trace elements were weakly or not influenced by the progression of the disease or the diagnostic procedures. Concentrations of aluminum were slightly higher in subjects with a longer iST (age, sex and stage adjusted geometric means: 11.44 vs. 7.75 µg/g for iST > 120 days vs. ≤ 40 days). There was a weak inverse relation of iST with concentrations of zinc and selenium (maximum differences of about 20 and 0.08 µg/g, respectively). Conclusions: concentrations of the trace elements were weakly or not influenced by the development of the disease before toenail collection. Only concentrations of aluminum increased slightly with increasing iST, whereas levels of zinc and selenium decreased weakly. Even in an aggressive disease as pancreatic cancer, toenail concentrations of trace elements may provide a valid measure of mid-term intake of trace elements, unaffected by clinical events and disease progression.

BACKGROUND:Epidemiological studies have suggested positive associations for iron and red meat intake with risk of pancreatic ductal adenocarcinoma (PDAC). Inherited pathogenic variants in genes involved in the hepcidin-regulating iron metabolism pathway are known to cause iron overload and hemochromatosis. OBJECTIVES/OBJECTIVE:The objective of this study was to determine whether common genetic variation in the hepcidin-regulating iron metabolism pathway is associated with PDAC. METHODS:We conducted a pathway analysis of the hepcidin-regulating genes using single nucleotide polymorphism (SNP) summary statistics generated from 4 genome-wide association studies in 2 large consortium studies using the summary data-based adaptive rank truncated product method. Our population consisted of 9253 PDAC cases and 12,525 controls of European descent. Our analysis included 11 hepcidin-regulating genes [bone morphogenetic protein 2 (BMP2), bone morphogenetic protein 6 (BMP6), ferritin heavy chain 1 (FTH1), ferritin light chain (FTL), hepcidin (HAMP), homeostatic iron regulator (HFE), hemojuvelin (HJV), nuclear factor erythroid 2-related factor 2 (NRF2), ferroportin 1 (SLC40A1), transferrin receptor 1 (TFR1), and transferrin receptor 2 (TFR2)] and their surrounding genomic regions (±20 kb) for a total of 412 SNPs. RESULTS:The hepcidin-regulating gene pathway was significantly associated with PDAC (P = 0.002), with the HJV, TFR2, TFR1, BMP6, and HAMP genes contributing the most to the association. CONCLUSIONS:Our results support that genetic susceptibility related to the hepcidin-regulating gene pathway is associated with PDAC risk and suggest a potential role of iron metabolism in pancreatic carcinogenesis. Further studies are needed to evaluate effect modification by intake of iron-rich foods on this association.

Germline variation and smoking are independently associated with pancreatic ductal adenocarcinoma (PDAC). We conducted genome-wide smoking interaction analysis of PDAC using genotype data from four previous genome-wide association studies in individuals of European ancestry (7,937 cases and 11,774 controls). Examination of expression quantitative trait loci data from the Genotype-Tissue Expression Project followed by colocalization analysis was conducted to determine if there was support for common SNP(s) underlying the observed associations. Statistical tests were two sided and P-values < 5 x 10-8 were considered statistically significant. Genome-wide significant evidence of qualitative interaction was identified on chr2q21.3 in intron 5 of the transmembrane protein 163 (TMEM163) and upstream of the cyclin T2 (CCNT2). The most significant SNP using the Empirical Bayes method, in this region which included 45 significantly associated SNPs, was rs1818613 (per allele OR in never smokers 0.87, 95% CI 0.82-0.93; former smokers 1.00, 95 CI 0.91-1.07; current smokers 1.25, 95%CI 1.12-1.40, interaction P-value=3.08x10-9). Examination of the Genotype-Tissue Expression Project data demonstrated an expression quantitative trait locus in this region for TMEM163 and CCNT2 in several tissue types. Colocalization analysis supported a shared SNP, rs842357, in high LD with rs1818613 (r2=0. 94) driving both the observed interaction and the expression quantitative trait loci signals. Future studies are needed to confirm and understand the differential biologic mechanisms by smoking status that contribute to our PDAC findings.

BACKGROUND:Whether circulating polyunsaturated fatty acids (PUFA) levels are associated with pancreatic cancer risk is uncertain. Mendelian randomization (MR) represents a study design using genetic instruments to better characterize the relationship between exposure and outcome. METHODS:We utilized data from genome-wide association studies within the Pancreatic Cancer Cohort Consortium and Pancreatic Cancer Case-Control Consortium, involving approximately 9,269 cases and 12,530 controls of European descent, to evaluate associations between pancreatic cancer risk and genetically predicted plasma n-6 PUFA levels. Conventional MR analyses were performed using individual-level and summary-level data. RESULTS:Using genetic instruments, we did not find evidence of associations between genetically predicted plasma n-6 PUFA levels and pancreatic cancer risk (estimates per one standard deviation increase in each PUFA-specific weighted genetic score using summary statistics: Linoleic acid - odds ratio (OR) = 1.00, 95% confidence interval (CI) 0.98-1.02; arachidonic acid - OR = 1.00, 95% CI 0.99-1.01; dihomo-gamma-linolenic acid - OR = 0.95, 95% CI 0.87-1.02). The OR estimates remained virtually unchanged after adjustment for covariates, using of individual level data or summary statistics, or stratification by age and sex. CONCLUSIONS:Our results suggest that variations of genetically determined plasma n-6 PUFA levels are not associated with pancreatic cancer risk. IMPACT/CONCLUSIONS:These results suggest that modifying n-6 PUFA levels through food sources or supplementation may not influence risk of pancreatic cancer.