Genetically predicted plasma phospholipid arachidonic acid concentrations and 10 site-specific cancers in UK biobank and genetic consortia participants : A mendelian randomization study

BACKGROUND & AIMS: Arachidonic acid (AA) is metabolized by cyclooxygenases and lipoxygenases to pro-inflammatory eicosanoids, which according to experimental research modulate tumor cell proliferation, differentiation, and apoptosis. We employed the Mendelian randomization design to test the hypothesis that higher plasma phospholipid AA concentrations are associated with increased risk of 10 site-specific cancers. METHODS: Two genetic variants associated with plasma phospholipid concentrations of AA (rs174547 in FADS1 [P = 3.0 × 10-971] and rs16966952 in PDXDC1 [P = 2.4 × 10-10]) in the Cohorts for Heart and Aging Research in Genomic Epidemiology Consortium were used as genetic instruments. The associations of those variants with cancer were taken from the UK Biobank (n = 367,643), FinnGen consortium (n = 135,638), International Lung Cancer Consortium (n = 27,209), Prostate Cancer Association Group to Investigate Cancer Associated Alterations in the Genome consortium (n = 140,254), Breast Cancer Association Consortium (n = 228,951), Ovarian Cancer Association Consortium (n = 66,450), and BioBank Japan (n = 212,453). RESULTS: Higher genetically predicted plasma phospholipid AA concentrations were associated with increased risk of colorectal and lung cancer. Results were consistent across data sources and variants. The combined odds ratios per standard deviation increase of AA concentrations were 1.08 (95% CI 1.05-1.11; P = 6.3 × 10-8) for colorectal cancer and 1.07 (95%CI 1.05-1.10; P = 3.5 × 10-7) for lung cancer. Genetically predicted AA concentrations had a suggestive positive association with esophageal cancer (odds ratio 1.09; 95% CI 1.02-1.17; P = 0.016) but were not associated with cancers of the stomach, pancreas, bladder, prostate, breast, uterus, or ovary. CONCLUSION: These results indicate that AA may be implicated in the development of colorectal and lung cancer and possibly esophageal cancer. Treatments with plasma AA-lowering properties should be evaluated for clinical benefit