Effect of growth factors on the expression of proto-oncogenes c-fos and c-myc in FRTL-5 cell line.

This study was performed to prove the hypothesis that oncogene expressions would have the same patterns with those of cellular growth to growth factors in FRTL-5 cells. Ribonucleic acids of FRTL-5 were extracted at 15', 30', 60' and 120' after administration of growth factors to quiescent FRTL-5, and blotted to the nitrocellulose membrane. They were hybridized with radiolabelled c-fos, c-myc and beta-actin probes. Hybridized dot blots were autoradiographed and the amount of radioactivity was measured by densitometry. Densitometric readings were used as the indices of oncogene expressions. Expressions of c-fos and c-myc were more prominent in combined administrations of TSH (10 mU/ml) and IGF-I (100 ng/ml) or IgG of Graves' disease (Graves' IgG; 1 mg/ml) and IGF-I than in combined administration of TSH and Graves' IgG. IgG of primary myxedema suppressed oncogene expressions by TSH or Graves' IgG, but not by IGF-I. From the above results, it was suggested that expressions of c-fos and c-myc to growth factors would have similar patterns with those of cell growth to growth factors in FRTL-5, and the actions of TSH and Graves' IgG would be manifested through same signal transduction system, but IGF-I would be manifested by its own.