Gut microbiome-driven colorectal cancer via immune, metabolic, neural, and endocrine axes reprogramming.

Colorectal cancer (CRC) is a leading cause of cancer mortality worldwide and is increasingly recognized as the outcome of complex host-microbe interactions. Beyond established genetic and environmental drivers, the gut microbiome has emerged as a causal and mechanistic contributor to CRC initiation, progression, and therapy response. This review synthesizes current molecular, ecological, and translational evidence to explain how gut microbial communities reprogram immune, metabolic, neural, and endocrine networks within the tumor microenvironment. CRC-associated dysbiosis is characterized by enrichment of pathobionts such as Fusobacterium nucleatum, pks⁺ Escherichia coli, and enterotoxigenic Bacteroides fragilis, and by loss of protective, short-chain-fatty-acid-producing commensals. These microbes promote carcinogenesis through genotoxin-induced DNA damage, epithelial barrier disruption, metabolic rewiring, and chronic inflammation that collectively sustain immune suppression and tumor growth. Defined mutational signatures from bacterial metabolites, including colibactin, cytolethal distending toxin, and indolimines, now directly link microbial exposures to human cancer genomes. By integrating these findings, this review conceptualizes CRC as a biofilm-structured, microbiome-driven ecosystem disease, where polymicrobial consortia coordinate barrier breakdown, immune evasion, and metabolic cooperation. Finally, we highlight emerging microbiota-targeted strategies, including dietary modulation, pre- and probiotics, postbiotics, bacteriophage therapy, engineered live biotherapeutics, and fecal microbiota transplantation, that translate these insights into precision prevention and therapy. Through this integrative framework, the review aims to reposition the microbiome from a correlative feature to a tractable determinant of CRC pathogenesis and treatment response.