Abstract 3438: Associations between estimated endotoxin exposure and circulating immunological markers among male farmers

Abstract Occupational exposure to endotoxin has been associated with reduced lung cancer risk. Farmers who perform certain tasks (e.g., raising hogs) can be highly exposed to endotoxin. The mechanisms through which endotoxin could confer a lower risk of lung cancer, while likely to be immune mediated, are not clear. To address this gap, we evaluated associations between estimated endotoxin exposure and circulating immunologic markers among male farmers in the Biomarkers of Exposure and Effect in Agriculture (BEEA) study. Our investigation included 122 non-smoking farmers from Iowa, oversampling those raising hogs (n=61). We evaluated 58 serologic markers, including some linked to lung cancer, that were measured using multiplex bead-based assays. Based on an algorithm linking personal air measurements in BEEA and published data to reported farming tasks, we estimated cumulative endotoxin exposure in the last 30 days and 12 months before sample collection. We used multivariable linear regression to estimate geometric mean ratios of immune markers across exposure quartiles, overall and by season of sample collection. Higher endotoxin exposure in the last 30 days was associated with increased levels of FGF-2, MIP-3A/CCL20, and sIL-4R (Ptrend ≤ 0.02), and with decreased levels of MDC/CCL22 (Ptrend = 0.02). In analyses stratified by season, the positive associations with FGF-2 and MIP-3A/CCL20 were most apparent in the winter (Ptrend = 0.002 and 0.03, respectively); we also observed an inverse association with sCD27 levels in the summer (Ptrend = 0.03). Similar patterns were observed for endotoxin exposure in the last 12 months. This study is the first to use novel algorithm-based endotoxin exposure estimates to evaluate associations with intermediate lung cancer-related markers. Several markers were associated with endotoxin levels in an exposure-response manner. Our findings suggest possible biological mechanisms through which endotoxin may reduce risk of lung cancer. Table 1. Associations between estimated endotoxin exposure in the last 30 days and selected serum im Citation Format: Somayina C. Ezennia, Laura E. Beane-Freeman, Vicky C. Chang, Shuai Xie, Gabriella Andreotti, Melissa C. Friesen, Jonathan N. Hofmann. Associations between estimated endotoxin exposure and circulating immunological markers among male farmers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3438.