Intratumoural Microbiota: Roles in Cancer Development, Prognosis, and Therapy

Breakthroughs in sequencing technologies have overturned the notion that tum ors are sterile. Recent studies reveal that bacteria, fungi, and viruses—collectively termed the intratumoral microbiota—are present across diverse cancer types. These microorganisms may colonize tumors through mucosal barrier disruption, local tis sue spread, or circulation in the blood. Once established, they act as key modulators of the tumor microenvironment. Mechanistic evidence shows that intratumoral microbiota can induce genomic in stability, alter epigenetic states, promote chronic inflammation, evade immune sur veillance, and reshape tumor metabolism. The composition and diversity of these microbial communities differ by tumor type and stage. Distinct microbial signatures are associated with patient prognosis and therapeutic response. The intratumoral microbiota are increasingly recognized not only as biomarkers for early detection and prognosis but also as potential therapeutic targets, especially in immunothera py. However, significant challenges remain in understanding their origins, biological functions, and the safe manipulation of these microbes. Overall, advances in this field hold promise to transform cancer diagnosis, prognosis, and treatment through microbiota-targeted strategies. This review highlights the characteristics and origins of intratumoral microbiota, their prognostic significance, and their emerging role in cancer therapy.