The expression of the Fibroblast Growth Factor (FGF) genes and their receptors in Kaposi's sarcoma (KS) have been evaluated in our laboratory. FGF3 (Int-2) was found to be expressed in 55% of the fresh KS specimens examined. The FGF3 oncoprotein was detected by immunohistologic techniques in the spindle-shaped tumor cells surrounding the irregular vascular slits, histologically characteristic of KS. Nucleic acid alterations of FGF3 in KS were identified by sequencing of RT-PCR products, SSCP and sequencing methods. Transformed NIH3T3 cells transfected with FGF3 induced KS-like tumors when infected into nude mice. These observations led to our hypothesis that an aberrant expression of FGF3 is involved in the pathogenesis of KS. We propose to elucidate the role FGF3 plays in the development of this neoplasm, the most prevalent tumor seen in patients with AIDS. The mechanisms of FGF3 activation and its role in KS will bed examined:1)FGF3 sequence alterations will be confirmed by the construction of genomic libraries from KS tumors and sequencing of clones of the FGF3 locus. Genomic libraries prepared from uninvolved skin from the same donors and from healthy patients will serve as controls. 2) Confirmed mutations detected in the FGF3 gene from KS will be introduced into the "wild type" FGF3 cDNA by site-directed mutagenesis. The transformation efficiency of mutated FGF3 cDNA will be examined in vitro by transfection into NiH3T3 cells, dermal human microvascular endothelial cells and smooth muscle cells. 3)The ability of FGF3 transformed NIH3T3 cell to induce KS-like tumor formation after transplantation into nude mice will be evaluated. 4)Attempts will be made to create a transgenic mouse model using a KS-derived FGF3 mutant. 5)The molecular events that result in the aberrant expression of FGF3 in KS will be studied,i.e.the possible presence inserted DNA viral sequences in KS will be examined by Southern blot analyses of genomic clones of FGF3 locus from KS tumors. The 5'regulatory sequences of FGF3 genomic clones from KS and normal tissues will be compared. 6) The specific FGF3 receptor(s) in KS will be characterized by Northern blot analysis and cross-linking experiments. The affinity of FGF3 for its receptor(s) will be determined. inhibition of the autocrine activation of the FGF3 receptor(s) in KS will be examined using antibodies against FGF3. 7) inhibition of FGF3 expression in KS will be studied using antibodies to FGF3 and antisense oligonucleotides by determining their effect on KS cell growth in vitro and in vivo. The proposed studies are designed to elucidate the relationship between activation of mutated FGF3 expression and the oncogenesis of KS. Potentially, the results of these investigations could lead to innovative therapeutic approaches for the treatment of KS by inhibition of FGF3 in KS.