PECAM1 and cancer: The phenotypic change of pulmonary endothelium compatible with endothelial–mesenchymal transition, evidenced by downregulation of endothelium-specific proteins such as VE-CAD, CD31, vWF, or VEGFR2, seemed to be evident 3 weeks after cancer cell inoculation (Fig. 4i), concomitant with the early phase of metastasis (Fig. 1g).