PECAM1 and hepatocellular carcinoma: PDGFRβ is the representative biomarker of tumor vessel–associated pericytes (33), and we also verified the good colocalization of PDGFRβ and blood vessel biomarker CD31 in the HCC tissues of monkey (Supplementary Material Fig. S3), indicating that PDGFRβ is a potential target for molecular imaging of vascularized tumors.