KDR and Merkel cell skin cancer: Due to the role of angiogenesis in tumorigenesis, TKIs targeting vascular endothelial growth factor receptor (VEGFR) and related kinases have been investigated as potential therapies for MCC. The tyrosine kinase c-kit is frequently expressed in MCC.However, MCC lacks highly recurrent tyrosine kinase amplification or mutation events that would otherwise provide a rationale for targeted tyrosine kinase inhibitor (TKI) therapy. molecular studies have not demonstrated a significant rate of activating mutations of the KIT gene, the tyrosine kinase c-kit is frequently expressed in MCC.