PECAM1 and neoplasm: In addition, tumor cell contribution to neovascularization was also confirmed by combined in situ- and immunofluorescence labelling in the mouse model displaying double-positivity of endothelial-like cells for the vessel marker CD31 and the human Y-chromosome (Figure 2G) as well as for CD31 and the human-DNA specific ALU-repeat sequences (Figure 3A–D).