AUTOCRINE TRANSFORMATION BY FIBROBLAST GROWTH-FACTOR-9 (FGF-9) AND ITS POSSIBLE PARTICIPATION IN HUMAN ONCOGENESIS

Transfection of human fibroblast growth factor 9 (FGF-9) cDNA into mou se BALB/c 3T3 clone A31 cells led to morphological transformation of t he cells and foci formation 4 weeks later. Isolated transformants had a higher saturation density than parental A31 cells, could grow in sof t agar, and secreted FGF-9 into the culture supernatant. The introduct ion of FGF-9 N33 cDNA, which encodes a truncated protein that has 33 N -terminal amino acids deleted and has the same mitogenic potency as FG F-9, failed to lead to foci formation. Although FGF-9 is a secretory p rotein, it does not have a typical secretory signal sequence, and the secreted protein retains the full sequence coded in the cDNA except fo r the initiating methionine. The produced FGF-9 N33 was not secreted a nd remained within the cell. It is possible that FGF-9 has an uncleava ble signal sequence within the first 33 N-terminal amino acids. All of the phenotypes acquired by transformation could be arrested by treatm ent with a neutralizing anti-human FGF-9 monoclonal antibody (MAb) 150 -59. Additionally, transformants formed tumors in nude mice, Injection of MAb 150-59 suppressed tumor formation in nude mice and caused exis ting tumors to regress. Our results suggest that the cellular transfor mation mediated by FGF-9 is produced by autocrine stimulation. We have detected FGF-9 production in the human tumor cell lines glioma NMC-G1 , from which FGF-9 was originally purified, and stomach carcinoma AZ-5 21. The growth of NMC-G1 was not affected by MAb 150-59, but that of A Z-521 was arrested by MAb 150-59 in the presence of heparin. Moreover, the growth of the AZ-521 cell tumor in nude mice could be partially a rrested by antibody treatment. The possibility of a participation of F GF-9 in the formation of human tumors is suggested. (C) 1997 Wiley-Lis s, Inc.