[Research Progresses on the Effects of CCL4 on Immune Escape 
in Tumor Microenvironment]

Immunotherapy has become the cornerstone of current malignant tumor treatment. However, the response of different patients to immunotherapy is highly heterogeneous, and not all patients can benefit from it. There is an urgent need to find biomarkers that can effectively predict the efficacy of immunotherapy. C-C chemokine ligand 4 (CCL4) is a cytokine, belonging to the inflammatory CCL subfamily. It is mainly secreted by immune cells and tumor cells and shows low or no expression in normal tissues but abnormally high expression in various malignant tumor tissues. After binding to CCL4 and its receptor C-C chemokine receptor type 5 (CCR5), it can recruit and mediate immune cell migration, destroy the stability of the tumor microenvironment (TME), participate in carcinogenesis and promote the development of tumors. In the tumor immune microenvironment, CCL4 can mediate and recruit the directed migration of key immune cells such as monocytes, macrophages, natural killer (NK) cells, and T cells, which makes it a potentially important element affecting the efficacy of immunotherapy and has specific value. This paper reviews the research progresses of CCL4's effects on immune escape in TME, in order to provide clues and references for basic research and clinical diagnosis and treatment.
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