Neoplastic AIDS-associated Kaposi's sarcoma cell line KSY-1 cannot transdifferentiate into capillaries

Objective: Kaposi's sarcoma (KS) is an acquired immunodeficiency syndrome ( AIDS)-defining neoplasm histologically characterized by proliferation of sp indle cells, inflammatory cells, and abundant neovascularization. When the malignant cell Line KSY-1 derived from an AIDS-KS tumor is transplanted sub cutaneously into nude mice, prominent neovascular features develop. Using t his mouse model of neoplastic KS, we set out to determine, using c-ets I ma rkers specific for mouse or human tissues, whether vascular growth and infl ammatory infiltrate induced by the transplanted KSY-1 cells is of host cell or transplant origin. Study Design/Methods: KS tumors were induced by subcutaneous inoculation of 5 x 10(6) KSY-1 cells/200 mu L in immunodeficient mice, and species-specif ic mouse and human riboprobes of the c-ets I protooncogene were used for in situ hybridization to define cell of origin. Results: Five different tumors were examined. Tissue sections from all case s were hybridized with radiolabeled riboprobes for the presence of both mou se and human c-ets 1 mRNA. Tumor cells were labeled with the human c-ets I probe, whereas neovascular and inflammatory tissues were of mouse origin. Conclusions: The finding that vascular but not tumor cells are of host orig in supports the model of tumor-induced vascularization via a mechanism of t umor cell-derived cytokine-medicated pathogenesis.