Abstract 746: Modeling micro- and nanoplastics-induced colon aging in organoids to unravel pathways leading to early-onset colorectal cancer.

Abstract Background: Early-onset colorectal cancer (EOCRC) is rapidly increasing, with projections that by 2030, one in ten colon cancers will occur in individuals under 50. Unlike hereditary syndromes, most EOCRC cases are sporadic, implicating environmental and aging-related mechanisms. Accelerated biological aging, characterized by telomere attrition, oxidative stress, and senescence-associated inflammation, is a defining feature of EOCRC. Micro- and nanoplastics (MNPs) can accumulate in the gut, induce oxidative stress, and damage DNA. These processes mirror hallmarks of aging, suggesting that chronic MNP exposure may accelerate colonic epithelial aging and promote EOCRC initiation. Methods: To test this hypothesis, we used patient-derived human colon organoids from normal and polyp tissues. Apical-out organoids, which expose the luminal surface to the environment, were treated with defined polyethylene-derived microplastics (1.7-2.2 μm) and nanoplastics (0.04-0.06 μm) at 0, 1 and10 μg/mL for up to 72 hours. We assessed viability, oxidative stress, senescence markers, and inflammatory cytokines. Telomere length will be quantified by qPCR, and cytokine profiling was performed using Olink proteomics. Results: Live/Dead assays revealed minimal cytotoxicity at 1 μg/mL, while nanoplastics induced greater cell death and oxidative stress at 10 μg/mL. Preliminary data suggest that nanoplastic exposure leads to telomere shortening. Moreover, gene expression analyses showed that nanoplastics triggered stronger mitochondrial and redox stress responses than microplastics, consistent with higher reactivity of smaller particles. Additional experimental groups will be included to validate and expand upon these preliminary findings. Conclusions: Although preliminary, these data point to potential links between MNP exposure and early aging-associated stress pathways in the colon epithelium. Continued refinement of this organoid model, together with expanded sample sizes and multiomic analyses, will be essential for determining whether these early signals represent meaningful contributors to EOCRC risk. Funding: Individualizing colorectal cancer patient care using the host and tumor telomere phenotype (RO1 CA204013), Curtiss Fund (92541775), C-SiG Core(s): Epigenomics & Spatial Biology Core, and Clinical Core of the Mayo Clinic Center for Cell Signaling in Gastroenterology (P30DK084567) Citation Format: Zahra Heydari, Gobinda Sarkar, Lisa A. Boardman. Modeling micro- and nanoplastics-induced colon aging in organoids to unravel pathways leading to early-onset colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 746.