The tumour microenvironment stimulates IFN-γ production by activated NK cells and further upregulates PD-L1 expression on the surface of tumour and NK cells [59, 62].Meanwhile, many exosomes are released from tumour cells, and stimulation with IFN-γ increases the amount of PD-L1 transported on their surface [43]. The gene discussed is CD274; the disease is neoplasm.