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

Background: Acquired immunodeficiency syndrome (AIDS) is associated with the occurrence of tumors such as Kaposi's sarcoma (KS) and B-cell lymphoma. However, no evidence exists yet that human immunodeficiency virus type 1, the causative agent of AIDS, is directly responsible for cell transformation. It is also not clear whether KS lesions, which are of complex cellularity, contain tumor cells derived from a true monoclonal malignancy (originating from a single malignant cell) or whether the lesions are just polyclonally hyperplastic in nature (containing increased numbers of normal cells). In fact, the presence of malignant KS cells has never been unequivocally shown in AIDS-associated KS, and previously isolated KS cell cultures were not immortal or malignant. Purpose: Our purpose was to (a) utilize technology that could facilitate isolation and enrichment of tumor cells from AIDS-associated KS lesions, (b) establish and characterize an immortalized KS cell line, and (c) test the malignant potential of such a cell line in animal models. Methods: Mononuclear cells were isolated from 2.5 L of pleural effusion from an AIDS-associated KS patient. T-lymphocytes, B-lymphocytes, monocytes/macrophages, and fibroblasts were removed by a cytotoxicity method, using monoclonal antibodies specific for cell surface markers 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 detected by G-banded marker studies, and phenotypic markers were determined by indirect immunofluorescence and immunocytochemical methods. Beige nude XID and severe combined immunodeficient mice mere used to evaluate the tumorigenic, angiogenic, and metastatic potentials of cells. Results: An immortalized cell line, named KS Y-1, was isolated. Its phenotype is similar to that of endothelial cells with positive CS34 and CD31 markers. Tetraploid chromosomal abnormalities were found in primary fresh KS tissue and in vitro passages of KS Y-1 cells. These cells promoted tumorigenesis, angiogenesis, and metastasis in immunodeficient mice. Tumors produced at the site of injection, as well as metastases in the lung, spleen, pancreas, gastrointestinal tract, and skin showed a human tetraploid karyotype. KS Y-1 cells show high plating efficiency. 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 mouse model can be used to study the effects of therapeutic compounds in advanced KS.