NRP1 and neoplasm: Although an incorporation of abnormal TECs that do not express normal EC markers in leaky ATVs is conceivable, the enhanced NRP1 expression in HT1080 cells under hypoxia, the apparent integration of HT1080 and of A431 tumor cells in the endothelial layer, and the concomitant subcellular localization of NRP1 and MET at the apical face of tumor cells are unique properties of VM.