PDGFRB and Kaposi's sarcoma: Furthermore, the appreciation of the importance of receptor tyrosine kinases, such as PDGFR and c-kit in the life cycle of KSHV has led to clinical trials exploring the efficacy of imatinib, an inhibitor of Abl as well as of these two tyrosine kinases, against KS; these trials have reported a partial regression of KS tumours in about a third of treated patients [323,324].