The mitogenic signaling pathway for fibroblast growth factor-2 involves the tyrosine phosphorylation of cyclin D2 in MCF-7 human breast cancer cells

Fibroblast growth factor-2 (FGF-2) is mitogenic for the human breast cancer cell line MCF-7; here we investigate some of the signaling pathways subser ving this activity. FGF-2 stimulation of MCF-7 cells resulted in a global i ncrease of intracellular tyrosine phosphorylation of proteins, particularly FGF receptor substrate-2, the protooncogene product Src and the mitogen-ac tivated protein kinase (MAP kinase) cascade, A major increase in the tyrosi ne phosphorylation of a 30-kDa protein species was also found. This protein was identified as cyclin D2 by mass spectrometry after trypsin digestion. Immunoprecipitation of cyclin D2 and immunoblotting with anti-phosphotyrosi ne antibodies confirmed that the tyrosine phosphorylation of cyclin D2 was indeed induced by FGF-2 stimulation. In addition, pharmacological inhibitio n of Src (with herbimycin A and PP2), and of the MAP kinase cascade (with P D98059), confirmed that Src activity is required for the FGF-2-induced phos phorylation of cyclin D2 whereas MAP kinase activity is not, Thus, tyrosine phosphorylation of cyclin D2 may be a hey regulatory target for FGF-2 sign aling. (C) 2000 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.