ISOLATION AND CHARACTERIZATION OF AN IMMORTAL NEOPLASTIC CELL-LINE (KS Y-1) FROM AIDS-ASSOCIATED KAPOSIS-SARCOMA

Background: Acquired immunodeficiency syndrome (AIDS) is associated wi th the occurrence of tumors such as Kaposi's sarcoma (KS) and B-cell l ymphoma. However, no evidence exists yet that human immunodeficiency v irus type 1, the causative agent of AIDS, is directly responsible for cell transformation. It is also not clear whether KS lesions, which ar e of complex cellularity, contain tumor cells derived from a true mono clonal malignancy (originating from a single malignant cell) or whethe r the lesions are just polyclonally hyperplastic in nature (containing increased numbers of normal cells). In fact, the presence of malignan t KS cells has never been unequivocally shown in AIDS-associated KS, a nd previously isolated KS cell cultures were not immortal or malignant . Purpose: Our purpose was to (a) utilize technology that could facili tate isolation and enrichment of tumor cells from AIDS-associated KS l esions, (b) establish and characterize an immortalized KS cell line, a nd (c) test the malignant potential of such a cell line in animal mode ls. Methods: Mononuclear cells were isolated from 2.5 L of pleural eff usion from an AIDS-associated KS patient. T-lymphocytes, B-lymphocytes , monocytes/macrophages, and fibroblasts were removed by a cytotoxicit y method, using monoclonal antibodies specific for cell surface marker s and baby rabbit complement. KS cells were cultured in the absence of exogenous growth factors in an effort to select for transformed cells capable of self-sustained growth. The karyotype abnormalities were de tected by G-banded marker studies, and phenotypic markers were determi ned by indirect immunofluorescence and immunocytochemical methods. Bei ge nude XID and severe combined immunodeficient mice mere used to eval uate the tumorigenic, angiogenic, and metastatic potentials of cells. Results: An immortalized cell line, named KS Y-1, was isolated. Its ph enotype is similar to that of endothelial cells with positive CS34 and CD31 markers. Tetraploid chromosomal abnormalities were found in prim ary fresh KS tissue and in vitro passages of KS Y-1 cells. These cells promoted tumorigenesis, angiogenesis, and metastasis in immunodeficie nt mice. Tumors produced at the site of injection, as well as metastas es in the lung, spleen, pancreas, gastrointestinal tract, and skin sho wed a human tetraploid karyotype. KS Y-1 cells show high plating effic iency. Conclusion: The KS Y-1 cell line could be the first evidence of AIDS-associated KS cells that may develop clones with an indisputable malignant cell phenotype. Implications: KS Y-1 cells in the in vivo m ouse model can be used to study the effects of therapeutic compounds i n advanced KS.