A number of genes related to cancer stem cells were validated by qRT-PCR, including Cxcl12/Sdf-1, Pdgfra, Lgr5, Lrg1, Pecam1/CD31, H19 and Src2, which were all significantly upregulated in Nanog-papillomas and Nanog-SCCs relative to control papillomas (Fig. 4B). This evidence concerns the gene PDGFRA and papilloma.