PDGFB and Kaposi's sarcoma: The existence of a KSHV-induced, ligand-mediated mechanism for PDGFRA activation is supported by immunohistochemistry staining of mECK36 and AIDS-KS lesions showing that the areas staining for both KSHV-LANA and phospho-PDGFRA correspond with the detection of PDGFRA ligands PDGFA and PDGFB.