KLK1 and systemic sclerosis: However, the angiogenesis inhibitor pent(r)axin-related gene (PTX3) is also up-regulated, while other genes critical for the angiogenic process, such as plexin B1 (PLXNB1, semaphorin receptor), tissue kallikreins KLK9, KLK11, and KLK12) [12], and DSG2 (a cadherin that mediates homophilic cell adhesion), undergo down-regulation in SSc-MVECs.