Nevertheless, these genes are known to act as tumor suppressor (e.g. ADAMTS18 and Periostin) [48,49], apoptosis-inducer (e.g. insulin like growth factor binding protein 5) [50], and regulator of vascular integrity (regulator of G-protein signaling 5) [51], suggesting that their down-regulation by K13 may have a causal role in the pathogenesis of KS lesions. This evidence concerns the gene POSTN and Kaposi's sarcoma.