Of note, spindle cells isolated from ulcerated KS-like skin lesions of BKV/Tat-transgenic mice co-express antigens specific for endothelial, smooth muscle, and antigen-presenting cells, and express a complex mixture of angiogenic factors, including fibroblast growth factor-2 and vascular endothelial growth factor [36], as observed in human KS lesions and primary KS cells isolated from human lesions [1,24,37]. This evidence concerns the gene FGF2 and Kaposi's sarcoma.