Microplastics' Impact on the Development of AOM/DSS-Induced Colitis-Associated Colorectal Cancer in Mice

Recently, evidence indicating that microplastics (MPs) have a hazardous effect on human health is accumulating. The potential of MPs having a role in carcinogenesis was suggested. Therefore, the aim of this study was to evaluate MPs' effect on colitis-associated colorectal cancer (CAC) development. The AOM/DSS-induced CAC model was reproduced in two groups of adult male C56BL/6 mice. One of these groups received MPs (5 μm polystyrene microbeads) with drinking water at a dose of 1.48 mg/kg/day throughout the experiment (12 weeks), and the other received water untreated with MPs. In the colons of mice that consumed MPs, there was a higher number of tumor nodules at the macroscopic level, a greater tumor prevalence on histological sections, more pronounced inflammatory infiltration, a higher goblet cell volume fraction, the content of highly sulfated mucins was found in them, and there were more tumors with increased enteroendocrine cell content. We did not find any MP effects on the claudins, mucins, proapoptotic factor Bax, or on the proliferation marker Mki67 gene expression in the medial colon, nor on the serum level of TNFα, IL-1β, IL-6, and IL-10 cytokines. Thus, MPs promote the CAC development in mice by exacerbating intestinal local inflammation and damaging the epithelial barrier, and MPs may represent a potential environmental cofactor contributing to CAC risk.