Intratumoral microbiota: Distribution, mechanisms, and therapeutic implications

Recent studies have increasingly highlighted the presence of microbiota within tumors and their substantial impact on tumor initiation, progression, and treatment efficacy. Intratumoral microbiota modulate tumor progression via multiple mechanisms, such as regulation of cancer cell proliferation, manipulation of immune microenvironment, and induction of the DNA damage. Notably, the distinct bacterial profiles associated with each tumor type can, in turn, promote or suppress tumor growth. Given the various mechanisms through which intratumoral microbiota influence tumor progression, a deeper understanding of their composition and functional roles in tumor dynamics is critical for the development of targeted therapies. In this review, we summarize current understanding and future perspectives of the bacterial lineages associated with different tumor types, discuss the mechanisms through which the intratumoral microbiome modulates tumor progression, and highlight emerging therapeutic strategies targeting intratumoral bacteria, including sonodynamic therapy (SDT), chemotherapy, immunotherapy, and oncolytic bacterial approaches.