Cells derived from skin biopsies from two Kaposi's sarcoma patients, an elderly female with a sporadic non-AIDS form, and an AIDS-affected homosexual male, were established in culture. The classic patient had a few small lesions, while the epidemic case presented-large, disseminated, cutaneous and oral mucosa lesions. The cells obtained from both patients, termed IST-KS2 and AIDS-IST-KS3 respectively, had the characteristic spindle shape reported for Kaposi's sarcoma-derived cells. By immunocytochemistry they were both found to express the smooth muscle specific isoform of alpha actin. The KS cells expressed the fibroblastic antigen TE-7, which is not expressed in endothelial cells. Furthermore both KS cultures were negative for the endothelium associated markers Factor VIII, EN4 and PAL-E. They were also negative for the leukocyte antigen CD45, but were positive for vimentin. Immunocytochemistry studies were therefore suggestive of a primitive mesenchymal cell. When the KS-derived cells were grown on a gel of reconstituted basement membrane, both cultures formed large branching colonies characteristic of malignant cells of mesenchymal origin. No differences were observed between HIV-related and the sporadic KS-derived cultures studied. Fibroblasts and smooth muscle cells did not form branching colonies, while endothelial cells on matrigel differentiated forming tube-like structures. Supernatants from both sporadic and AIDS-related KS cell cultures had similar effects on endothelial cell growth in vitro and were also found to stimulate chemotaxis and chemoinvasion of normal vascular endothelial cells in the Boyden chamber assay, showing angiogenic potential in vitro. Our results demonstrate that long term cultures of spindle shaped cells derived from either HIV-associated and classic KS show the same histocytochemical phenotype, have invasiveness in matrigel similar to that of malignant sarcomas, and share in vitro angiogenic properties. Therefore, factors from the host are likely to be responsible for the divergent clinical picture of the classic and epidemic Kaposi's patients studied here.

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