Cancer, characterized by its high incidence and low cure rate, is the leading cause of mortality in both China and developed countries (Xia et al., 2022). The occurrence and progression of tumors are intricately linked to immune function. On one hand, the body's immune system can identify and eliminate cancer cells through various mechanisms of immune response. On the other hand, during the process of immune selection, cancer cells can employ immune remodeling to counteract and evade the destructive effects inflicted by the immune system upon them - a phenomenon known as an immune escape. Over recent decades, extensive research into the dynamic and complex interactions between cancer and the immune system has led to breakthroughs in tumor immunotherapy approaches such as immune checkpoint inhibitors, CAR-T cell therapy, and vaccine therapy. These therapies aim to enhance anti-tumor immunity while antagonizing cancer cell evasion strategies with promising results in curing or converting cancers into chronic diseases. However, given that only a subset of patients respond positively to these treatments, there is an urgent need to identify novel cellular and molecular targets for future generations of immunotherapy.

The tumor immune microenvironment, shaped by the intricate interactions among macrophages, neutrophils, mast cells, dendritic cells, T cells, B cells, NK cells, and other immune factors and cells, resembles a battleground where tumor immunity is both promoted and suppressed. A comprehensive understanding of the positive immune response cells, immunosuppressive molecules, and factors influencing the tumor immune microenvironment can offer novel insights for tumor immunotherapy. Among numerous factors impacting the effects of the tumor immune microenvironment, platelets - an integral part of innate immunity - not only exhibit functional similarities to innate immune cells but also possess the capacity to engage with antigen-presenting cells and lymphocytes through various receptor molecules expressed on their surfaces as well as derived bioactive substances. The significance of platelets in directly or indirectly regulating the tumor immune microenvironment should not be overlooked.

Although platelets are small, they possess remarkable deformability and potent secretion characteristics, playing a pivotal role in blood circulation. Over the past few years, as our understanding of the interaction between platelets and blood vessel walls has improved, we have gradually unraveled their connection with inflammation, immune response, and tumor cells (Koupenova et al., 2018). The paradoxically complex process of platelet-mediated antitumor or tumor-promoting effects stems partly from their influence on the tumor immune microenvironment. Given the continuous updates in relevant research studies, it is imperative to review existing literature and explore the relationship between platelets, their bioactive factors, and the tumor immune microenvironment during tumorigenesis and progression. This review aims to elucidate the delicate balance within this relationship concerning both the anti-tumor and pro-tumor functions of platelets while proposing novel insights into utilizing a targeted approach toward platelet-based strategies for tumor immunotherapy.