CD274 and oral cavity squamous cell carcinoma: HypoExo miR-21 from oral squamous cell carcinoma (OSCC) increases the PD-L1 expression of MDSCs, thus decreasing the antitumor ability of γδ T cells [204]; lung cancer-derived EVs from intermittent hypoxia increase the PD-L1 expression of macrophages, thus aggravating the immunosuppressive status in macrophages [205].