Tumor-Resident Bacteria: Mechanisms of Carcinogenesis, Metastasis and Clinical Implications

Abstract The human microbiome constitutes an intricate ecosystem comprising bacteria, viruses, fungi, and archaea, which are localized across different anatomical sites, including the skin, oral cavity, respiratory system, and gastrointestinal tract. The microbiota (the microbial community within the body) plays a crucial role in cancer by affecting its initiation, progression, and treatment response. Genomic instability, chronic inflammation, and metabolite production are some features that are responsible for initiation. It is a major regulator of the immune system. Though some beneficial microbes promote anti-tumor immunity it can create an immunosuppressive tumor microenvironment, enabling cancer to evade immune destruction, affecting cancer therapy efficacy. The rapid advancement of high-throughput sequencing has yielded increasing evidence for the existence of a microbial community within tumor tissue. It is crucial to explore the mechanisms of intratumor microbe migration, their potential carcinogenic roles, the defining features of different types of tumor-associated microbes, the methodologies used in tumor microbiota research, and the clinical value of targeting these microbes in cancer therapy. The diverse environments provided by various tissues and organs critically influence host–microbe interactions.