The intratumoral microbiome as an emerging hub in cancer pathogenesis and precision oncology

Over the past decade, the number of microbial communities identified within tumors has increased by 400%. Notably, the intratumoral microbiome, which includes bacteria, fungi, viruses, and other microorganisms within tumor tissues, was first discovered more than a century ago. Based on the updated framework of cancer characteristics, we propose that the immune microenvironment is a fundamental and variable microbial feature in cancer. Numerous studies have demonstrated that the intratumoral microbiome constitutes a critical component of the tumor microenvironment. However, due to its low biomass, characterizing its functional mechanisms remains a significant challenge. To summarize current research on the intratumoral microbiome in oncology, we first examine its establishment, homeostasis, and heterogeneity across different cancer types, followed by a comprehensive exploration of its multifaceted roles in tumor initiation and progression. Furthermore, we discuss the critical implications of the intratumoral microbiome in cancer biomarkers, antitumor therapies, and novel microbe-based anticancer strategies. In summary, this review highlights the intratumoral microbiome as an emerging therapeutic target, offering new perspectives for deciphering the complex mechanisms of cancer.