OVEREXPRESSION OF THE FGF-2 24-KDA ISOFORM UP-REGULATES IL-6 TRANSCRIPTION IN NIH-3T3 CELLS

We have isolated NIH-3T3 cell lines overexpressing the nuclear 24-kDa isoform of fibroblast growth factor (FGF)-2 and characterized its regu latory effect on the expression of interleukin-6 (IL-6) in these cells . The clone pRF5 expressing the highest level was able to grow in 1% s erum medium to a high saturation density and acquired a radioresistanc e advantage. In pRF5 and another clone pRF1, IL-6 RNA levels mere mark edly increased. Studies with IL-6 promoter constructs revealed that IL -6 gene up-regulation occurred at the transcriptional level and did no t involve the AP-1 binding site. Exogenously added 18-kDa isoform of F GF-2 (100 ng/ml) produced down-regulation of IL-6 involving an AP-1 bi nding site, thus suggesting a receptor-independent pathway for the int racellular 24-kDa isoform. (C) 1998 Federation of European Biochemical Societies.