In hypoxic ovarian cancer (109) and pancreatic cancer (110), exosomes mediate the polarization of M2-type macrophages into immunosuppressive M2-like macrophages expressing PD-L1 and IL-10, inhibiting the proliferation of CD4+ and CD8+ T cells in vitro; in vivo, this process promotes tumor growth through PD-L1 (111). Here, CD274 is linked to ovarian carcinoma.