Lee et al. further found that, in keloid, not only the expression of PTN decreased but also the expression of its functional receptor RPTPB/F and upstream regulators was decreased, including PDGF-B, PDGFR-A, and PDGFR-B, which may be a potential novel treatment for keloid in humans (32, 84). Here, PTPRZ1 is linked to keloid.