THE HIV-1 TAT PROTEIN INDUCES THE EXPRESSION AND EXTRACELLULAR APPEARANCE OF ACIDIC FIBROBLAST GROWTH-FACTOR

Mounting experimental evidence suggests that the TAT protein, released from human immunodeficiency virus-1 (HIV-1)-infected inflammatory cel ls, may genetically reprogram targeted cells within a localized enviro nment to develop highly vascularized tumors of mesenchymal origin. The fibroblast growth factor (FGF) family of polypeptides has gained gene ral acceptance as initiators of angiogenesis and functions as potent m ito gens for mesoderm-derived cells. To evaluate a potential biologica l relationship between TAT and acidic FGF (FGF-1), primary murine embr yonic fibroblasts either were transfected with the viral transactivato r or were transduced (retrovirally mediated) with a secreted, chimeric form of the human polypeptide growth factor, human stomach tumor/Kapo si's sarcoma (hst/KS)FGF-1. Reverse transcriptase-polymerase chain rea ction, Western blotting, in situ immunohistochemical, heparin affinity , DNA synthesis, and transient transfection techniques were used to co nfirm expression, localization, and functionality of the transgenes, B oth transfected and transduced cells constitutively expressing either TAT or (hst/KS)FGF-1 adopted a transformed phenotype, maintained aggre ssive growth behavior, and demonstrated both induction of EGF-specific phosphotyrosyl proteins and nuclear association of FGF-1 and FGF-1 re ceptor. Increased levels of endogenous, murine FGF 1 mRNA (reverse tra nscriptase-polymerase chain reaction) and protein (immunoblot analysis ) were apparent in both (hst/KS)FGF-1- and TAT-transformed cells, Medi um conditioned by (hst/KS)FGF-1-transduced cells contained steady-stat e levels of biologically active FGF-1 which exhibited a representative molecular weight. Limited sodium dodecyl sulfate-polyacrylamide gel e lectrophoretic analysis of the conditioned medium from TAT-transformed cells demonstrated the appearance of FGF-1 as latent, high molecular weight complexes requiring reducing agents to activate full biological activity. Collectively, these results suggest that TAT induces the ex pression and secretion of FGF-1, which may be potentially relevant to the pathophysiological development of AIDS-Kaposi's sarcoma.