The main battlefield of mRNA vaccine - Tumor immune microenvironment

With the increasing threat of tumors to humans, mRNA vaccine-based immunotherapy has received extensive attention; however, the killing effect is sometimes unsatisfactory. The occurrence of tumors is closely related to the abnormality of the tumor immune microenvironment, including the increase in the number of immuno-suppressive cells, the anomaly of some cells with tumor-killing function, and the increase in the glycolysis pathway, all of which will affect the anti-tumor effect of mRNA vaccines. Furthermore, delivery in the body and successful escape from lysosome are also essential steps that involve the result of killing. Starting from inhibiting tumor growth and metastasis by mRNA vaccines, this paper summarizes the tumor microenvironment con-structed by immunosuppressive cells and cytokines, which inhibit immune cells from exerting anti-tumor effects, emphasizing the increase of glycolytic pathway after tumor formation, which makes tumors have a high prob-ability of metastasis. In the present study, mRNA vaccines adjust the number of immune cells by combining adjuvants or immune checkpoint inhibitors (ICIs), thereby improving the tumor immune microenvironment (TIME) and tilting the balance in favor of immune-potent cells can achieve better anti-tumor effects. All efforts to understand the relationship between TIME and mRNA vaccine will provide a basis for tumor treatment in the future.