Intratumoral microbiota in tumorigenesis: A double-edged sword

The rapid development of high-throughput sequencing technologies and bioinformatics has enabled the identification of diverse microbial communities within tumor tissues, giving rise to the concept of intratumoral microbiota. Comprising bacteria, viruses, fungi, and archaea, the intratumoral microbiota has been shown to play critical roles in tumor initiation, progression, and therapeutic responses. This review systematically summarizes the composition, ecological characteristics, and functional roles of intratumoral microbiota, with particular emphasis on its dual regulatory mechanisms in tumorigenesis, progression, metastasis, and recurrence. We further delineate four principal mechanistic pathways through which intratumoral microbiota influence tumor biology, including receptor-mediated signaling, metabolic reprogramming, effector molecule secretion, and intracellular invasion. Additionally, we evaluate the translational potential of these findings in clinical oncology, offering innovative perspectives for tumor diagnosis, therapeutic intervention, and preventive strategies.