The bidirectional regulatory effects of bacteria on blood vessels in the tumor microenvironment.

The diagnosis and treatment of tumors represent significant global challenges. Understanding the tumor microenvironment (TME) is crucial for a more comprehensive understanding of the mechanisms of tumorigenesis. The TME is a dynamic and complicated multicellular system consisting of tumor cells, various types of non-tumor cells, molecular signals, and extracellular matrix. Tumor blood vessels, formed through diverse mechanisms including vasculogenesis, sprouting angiogenesis, intussusceptive growth, vessel coalescence, co-option, vasculogenic mimicry, and lymphangiogenesis, serve as pivotal regulators in the TME by controlling tissue perfusion, orchestrating immune cell trafficking, facilitating metastasis, and modulating responses to therapeutic interventions. As our understanding of tumor vessels formation deepens alongside advancements in microbial research, an increasing number of studies have reported that bacteria can affect tumorigenesis and development by acting on tumor vessels; bacteria could even become a potential anti-tumor therapy. Although the important role of bacteria in tumor tissue has been well reviewed, no studies have summarized the effects of bacteria on tumor vessels. In this review, we aim to provide a comprehensive review of the important literature describing the role of bacteria in the tumor vasculature system and summarize its mechanism.