TGFB1 and neoplasm: proved that exosomes derived from tumour cells can promote breast cancer progression through releasing abundant immunosuppressive cytokines (TGF‐β) to suppress immune reactions.41 Tumour microenvironment derived exosomes, which are secreted by tumour stromal cells (principally tumour associated fibroblasts), promote tumour growth by providing cancer cells with the substance needed for metabolism under a nutrient‐deficient environment.42 As for CCA, exosomes play an important role in regulating tumour growth.