Analysis of the Transforming Potential of Growth and Differentiation Factors in Syrian Hamster Embryo Cells: Reversible and Irreversible Transformation.

Abstract

The mitogenic growth and differentiation factor (GDFs) oncostatin M (OM), epidermal growth factor (EGF), fibroblast growth factor 4 (FGF-4), platelet-derived growth factor AA (PDGF AA), PDGF AB, and PDGF BB and the anti-mitogenic GDF, transforming growth factor beta one (TGF-beta1), were tested in the 7-day continuous exposure and 24-h transient exposure Syrian hamster embryo (SHE) cell transformation assay to determine their reversible and irreversible transforming potential. OM was negative while EGF, FGF-4, and PDGF AA were positive for statistically significant morphological transformation (MT) in the 7-day exposure SHE cell transformation assay. PDGF AB and PDGF BB (but not EGF, FGF-4, and PDGF AA) were positive for statistically significant MT in the 24-h transient exposure SHE cell transformation assays. TGF-beta1 was not only negative for the induction of MT in the 7-day and 24-h exposure SHE cell transformation assays, but suppressed the spontaneous background transformation response. Investigation of the transformation suppression potential of TGF-beta1 demonstrated that TGF-beta1 was able to irreversibly suppress the transformation potential of a variety of transforming agents including growth factors, Ames assay positive carcinogens, and Ames assay negative carcinogens. PDGF AA and PDGF BB were investigated to better understand the reversible and irreversible transformation response. Differences in the receptors activated, the proteins phosphorylated by the receptors, and immediate early gene expressed were observed in SHE cells treated with either PDGF AA or PDGF BB. Importantly, SHE cells treated with TGF-beta1 and PDGF BB, two GDFs, which modulate SHE cell transformation irreversibly, altered DNA methylation; PDGF AA did not demonstrate this effect. Together these data demonstrate that the SHE cell transformation assay can be utilized to evaluate the transformation potential and mechanism of activation of GDFs.