Microplastics–Gut Microbiome Crosstalk in Carcinogenesis: Mechanisms, Molecular Targets and Emerging Therapeutic Directions

Microplastics (MPs; <5 mm) are ubiquitous environmental contaminants mainly taken up by the human body through ingestion and inhalation. The gastrointestinal tract is a major target for biological effects because ingested particles can directly interact with the intestinal epithelium and gut microbiota. Experimental studies have demonstrated that MP exposure can change microbial community structure and function, damage the integrity of the intestinal barrier, induce oxidative stress and inflammation, and disrupt microbial and host metabolism. Therefore, this narrative review aims to evaluate the emerging association between MP exposure, gut microbiome dysbiosis, and carcinogenesis with special emphasis on molecular mechanisms, microbiome-mediated effects, organ-specific cancer associations, and the strength of available evidence. The most compelling MP-specific evidence for cancer is from recent colorectal models, with reports of increased colitis-associated tumorigenesis, altered response to treatment, and microplastics detected in human colorectal cancer specimens. In vivo animal studies have shown that microbiome-targeted strategies, particularly probiotics, can ameliorate MP-related intestinal or hepatic toxicity, with prebiotics, synbiotics, postbiotics, fecal microbiota transplantation, dietary interventions, and nanomedicine being largely investigational. Overall, this review distinguishes established findings from emerging associations and highlights research priorities for exposure assessment, biomarker development, mechanistic validation, and future health strategies.