Intratumoral microbiota in colorectal cancer: focus on specific distribution and potential mechanisms

Colorectal cancer (CRC) is one of the most prevalent and lethal malignant tumors globally, posing significant health risks and societal burdens. Recently, advancements in next-generation sequencing technology have identified CRC intratumoral microbiota, thereby opening up novel avenues for further research. This review synthesizes the current advancements in CRC intratumoral microbiota and their impact on CRC progression and discusses the disparities in the relative abundance and community composition of CRC intratumoral microbiota across various colorectal tumors based on their anatomical location and molecular subtypes, as well as the tumor stages, and spatial tumor distribution. Intratumoral microbiota predominantly influence CRC development by modulating colonic epithelial cells, tumor cells, and the tumor microenvironment. Mechanistically, they can cause DNA damage, apoptosis and epithelial-mesenchymal transition. The effects of different intratumoral microbiota on CRC have been shown to be two-fold. In the future, to address the limitations of existing studies, it is important to develop comprehensive experimental protocols and suitable in vitro models for elucidating more mechanisms of intratumoral microbiota on CRC, which will facilitate the clinical application of microbe-related therapeutic strategies in CRC and potentially other tumors.