INVOLVEMENT OF BASIC FIBROBLAST GROWTH-FACTOR IN SURAMIN-INDUCED INHIBITION OF V79 AP4 FIBROBLAST CELL-PROLIFERATION/

The V79/AP4 Chinese hamster fibroblasts were densely stained with the anti-basic fibroblast growth factor (bFGF) antibody demonstrating an e ndogenous production of the peptide. The in vitro proliferation of the se cells was stimulated by exogenous bFGF and the maximum growth (259% increase in H-3-thymidine incorporation into DNA) was reached with bF GF 10 ng ml-1. Inhibition of bFGF-mediated mitogenic pathway was obtai ned with a 15-mer antisense oligodeoxynucleotide targeted against bFGF mRNA and with suramin, a drug which blocks the biological activity of heparin-binding growth factors. bFGF antisense oligomer reduced the s ynthesis of DNA by 79.5 and 89.5% at 20 and 60 muM, respectively; this effect was reversed by the addition of exogenous bFGF to the culture medium. A short-term exposure to suramin 300 mug ml-1 produced a modes t reduction in H-3-thymidine incorporation but suppressed the mitogeni c effect of bFGF on V79/AP4 cells. In cells treated with suramin 300 m ug ml-1 the drug concentration increased linearly over 3 days, reachin g 13.15 mug mg-1 of protein; cell proliferation was inhibited in a dos e-related manner as evaluated by the colony formation assay (IC50: 344 .22 mug ml-1) and by the number of mitoses observed in culture. Furthe rmore, the drug induced ultrastructural alterations, consisting of per inuclear cisternae swelling, chromatin condensation, nucleolar segrega tion and cytoplasmic vacuolations. These findings demonstrated that th e endogenous production of bFGF plays an important role in V79/AP4 fib roblasts proliferation, and the inhibition of bFGF-mediated mitogenic signalling with bFGF antisense oligomer or suramin is an effective mea n of reducing cell growth.