PECAM1 and neoplasm: Mice treated with mono- or dual therapy, however, did exhibit a significantly lower quantity of CD31+ blood vessels compared with the ctrl group (anti–PD-1 P < 0.0001, anti-MIF P < 0.001, anti–PD-1/anti-MIF P < 0.0001), which is in agreement with MIF’s previously reported action in promoting tumor angiogenesis (18).