Vascular endothelial growth factor and Kaposi's sarcoma cells in human skin grafts

Human cancer cells often produce tumors in animal models that incompletely reproduce the histology of the parental tumor. Kaposi's sarcoma (KS) cells, in particular, have not produced durable angiogenic lesions in animal models that resemble those of KS in humans. We investigated the contribution of transformed KS cells, vascular endothelial growth factor (VEGF), and human skin tissue on tumor development in a human skin graft/mouse model. High levels of serum VEGF (322 pg/ml) were seen in HIV-1-infected persons with KS compared with HIV-1-infected persons without KS (115 pg/ml). Human KS lesions expressed VEGF in the spindle cells. Transformed KS cells expressed the mitogenically active 121-amino acid and 165-amino acid isoforms of VEGF. Tumors induced by KS cells implanted in the SCID mice grew preferentially in human skin grafts rather than in ungrafted murine skin. Tumors induced in the presence of human skin grafts developed numerous lumens expressing α_vβ₃ integrin. KS cells inoculated with neutralizing anti-VEGF antibody did not form tumors. This study supports an important role for VEGF in tumor development and shows how a human tissue can preferentially promote tumor growth.