IMMUNOHISTOCHEMICAL DETECTION OF BCL-2 IN AIDS-ASSOCIATED AND CLASSICAL KAPOSIS-SARCOMA

Kaposi's Sarcoma (KS) is an angioproliferative disease that is charact erized by, proliferation of spindle-shaped cells predominantly of vasc ular endothelial cell origin, neoangiogenesis, inflammatory cell infil tration, and edema. Although the lesions of classical KS and AIDS-asso ciated KS (AIDS-KS) share common histological features, AIDS-KS occurs at a markedly higher frequency with a more aggressive clinical course Immunohistochemical analyses of 26 evolutionarily staged AIDS-KS lesi ons derived from HIV-infected patients demonstrate significant cytopla smic levels of Bcl-2, a protooncogene known to prolong cellular viabil ity and to antagonize apoptosis. Bcl-2 expression increases as the pat hological stage of KS advances. Immunohistochemical analyses of classi cal KS lesions demonstrate prevalent expression of Bcl-2 as well, indi cating that upregulation of Bcl-2 may be important in the pathogenesis of both classical and AIDS-associated KS. Coexpression of Bcl-2 and f actor VIII-related antigen in spindle-shaped cells present within RS l esions suggests that Bcl-2 is upregulated within the vascular endothel ial spindle-shaped cells of KS. The consequences of upregulated Bcl-2 expression within RS lesions may be prolonged spindle cell viability w hich, when coupled with dysregulated cellular proliferation due in par t to synergistic activities of inflammatory and angiogenic cytokines a nd NN-I Tat protein, may result in the maintenance, growth, and progre ssion of KS.