TAT and Kaposi's sarcoma: Tat has been suggested to play a role in HIV-related Kaposi sarcoma by promoting EC proliferation and tumor angiogenesis, where Tat binds specifically and activates the Flk-1/kinase insert domain receptor (Flk- 1/KDR), a VEGF-A tyrosine kinase receptor, and promotes angiogenesis (98).