Furthermore, immunodeficient mice carrying sh-CXCR4 PD/S-SCCs developed significantly less metastatic foci in the lungs than mice carrying sh-control tumors (Fig. 3d, e), in the absence of alterations in the tumor angiogenesis, as indicated by the unaltered frequency of CD31+ vessels (Fig. 3f, g) and the conserved expression of Vegfr2, a marker of endothelial cells (Supplementary Fig. 3J). This evidence concerns the gene PECAM1 and neoplasm.