Fatty acid binding protein 4(FABP4) is an adipocyte-type fatty acid binding protein, which is mainly highly expressed in adipocytes and macrophages. FABP4 is a chaperone molecule in the transport process of intracellular free fatty acids. FABP4 can bind to free fatty acids and transport them into cells. At the same time, FABP4 is involved in the regulation of gene expression, cell proliferation, differentiation and signal transduction of tumor metastasis. It is involved in the interaction between fat and tumor tissue, including lipid transfer between adipocytes and tumor cells, and provides fatty acids required for tumor growth. It is regarded as a potential factor for association between obesity and tumor.