Bifunctional effects of heparin-binding protein HBp17 on DNA synthesis in cells.

A 17 kD heparin-binding protein (HBp17) has a biphasic dose-dependent effect on DNA synthesis in 3T3 cells. Maximal stimulation of DNA synthesis occurs at 8 ng/ml HBp17, but a half-maximal inhibition occurs at approximately 500 ng/ml. This inhibition can easily be reversed by addition of 400 pg/ml aFGF or 100 pg/ml bFGF, whereas EGF had no effect. This biphasic action of HBp17 was also seen in human umbilical vein endothelial cells (HUVEC), whereas it was not found in the malignant cell line, A431-AJC. The functional relationship between HBp17 and FGF is discussed.