PECAM1 and neoplasm: Immunohistochemistry (IHC) stain of CD31, an endothelial cell marker, also showed that CD31 expression was dramatically increased in Lon-overexpressing B16/F10 tumor and decreased under the treatment with Fc-VFD and/or anti-PD-L1 (Fig. 2H), suggesting that Fc-VFD treatment is able to promote vascular normalization.