The role of exosomes in the tumour microenvironment on macrophage polarisation

Macrophages are highly heterogeneous immune cells that play an important role in the tumour microenvironment (TME). After being stimulated differently in the TME, macrophages can be polarised into the M1 phenotype to exhibit an anti-tumour effect or the M2 phenotype to exhibit a tumour-promoting effect. There are a large number of exosomes in the TME that can transmit information between cells and regulate the polarisation of macrophages, thereby affecting tumour invasion, metastasis, and treatment. This review introduces some of the pathways involved in M1/M2 macrophage polarisation and the effects of substances carried by exosomes from different sources in the TME on macrophage polarisation, especially microRNAs (miRNAs).