Stolzenberg-Solomon, Rachel Z.

Abstract Background: Genome-wide association studies (GWAS) have linked single nucleotide polymorphisms (SNPs) to pancreatic ductal adenocarcinoma (PDAC) risk at over 20 genomic loci. The Pancreatic Cancer Cohort Consortium and Pancreatic Cancer Case-Control Consortium are currently expanding on previous GWAS studies for PDAC from ∼9,000 cases and ∼12,000 controls to ∼36,000 cases and ∼800,000 controls in individuals of European and Asian ancestry. This ongoing GWAS phase is estimated to detect up to 50 new risk signals. Post-GWAS studies aim to fine-map and functionally assess risk variants in disease-relevant cell types and contexts to identify target genes and underlying mechanisms of risk. Massively parallel reporter assays (MPRAs) are a powerful method of assessing allele-specific gene regulatory effects. Integrating sequences into the genome using lentiviruses (Lenti-MPRA) enables the capture of variant function in the context of the native cellular chromatin. An added benefit is that Lenti-MPRAs can be used for difficult to transfect cells such as primary cells, that often reflect the disease relevant cell types. Methods: We have used a lentiviral MPRA to test 228 fine-mapped SNPs at the chr5p15.33 multi-cancer risk locus in PDAC cell lines (MIA PaCa-2, PANC-1) and the normal-derived ductal pancreas (HPDE) cell line. Additionally, we have optimized the transduction of large MPRA libraries into primary pancreas cells. Tunicamycin was used to induce ER stress in cell lines and primary cells, assessing downstream gene expression using RT-qPCR. Results: Our pilot MPRA demonstrated high reproducibility in PDAC cell lines (r2=0.93-0.97, MIA PaCa-2, PANC-1 cells) and normal-derived pancreatic ductal cells (r2=0.68-0.86, HPDE cells). We identified 33 SNPs out of 228 with significant allele-specific transcriptional activity in PDAC cell lines and 5 in HPDE cells (FDR ≤0.05). An additional 6-15% of variants exhibited significant allele-specific transcriptional activity when in the frames of the SNP-centered tested oligos were shifted left or right. We demonstrate the inducibility of ER-stress with tunicamycin treatment over 24 hours in cells lines and primary pancreatic cells. Additionally, we observed increased expression of CLPTM1IL at the chr5p15.33 locus after tunicamycin treatment over 24 hours in cell lines and primary pancreatic cells, suggesting ER-stress and inflammation may influence gene expression at this locus. Conclusions: Lentiviral MPRA assays in commonly used PDAC cell lines have demonstrated good reproducibility. The optimization studies and preliminary work in primary pancreatic cells provide a solid foundation for the next steps of assessing all GWAS loci in ER stress, an important disease relevant condition. Citation Format: Minal B Patel, Aidan O'Brien, Jun Zhong, Irene Collins, Jason W Hoskins, Stephen J Chanock, Samuel O Antwi, Rachel Z Stolzenberg-Solomon, Alison P Klein, Brian M Wolpin, Sara Lindström, H. Efsun Arda, Kevin M Brown, Katelyn E Connelly, Laufey T Amundadottir, Meagan Jezek. The functional characterization of pancreatic ductal adenocarcinoma GWAS risk variants in primary pancreatic cells – A pilot study [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr A018.

Abstract Background: Whether circulating polyunsaturated fatty acid (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 SD 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; and dihomo-gamma-linolenic acid OR = 0.95, 95% CI = 0.87–1.02]. The OR estimates remained virtually unchanged after adjustment for covariates, using 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: These results suggest that modifying n-6 PUFA levels through food sources or supplementation may not influence risk of pancreatic cancer.