PECAM1 and neoplasm: Moreover, using the Human Protein Atlas (HPA) website, we examined the protein expression level of the hub genes and observed that protein expression of SPP1, COL1A1, and COL3A1 was noticeably upregulated in tumor samples, whereas the protein expression of VWF, PECAM1, EDN1, CDH5, and TEK was noticeably downregulated (Figure 8).