Transformation of mouse mammary epithelial cells with the Ha‐ras but not with the neu oncogene results in a gene dosage‐dependent increase in transforming growth factor‐α production

Abstract

An enhanced expression of transforming growth factor‐α (TGFα) was demonstrated in two clones of NOG‐8 mouse mammary epithelial cells, NOG‐8 SR1 and NOG‐8 SR2, that have been transformed by a v‐Ha‐ras oncogene. The amount of TGFα production in NOG‐8 SR1 and NOG‐8 SR2 cells was dependent on the level of p21 ^ras expression in these clones, which directly correlated with their cloning efficiency in soft agar. There was also a decrease in the number of epidermal growth factor (EGF) receptors on the NOG‐8 SR1 and NOG‐8 SR2 cells that is proportional to the amount of TGFα secreted. These effects were specific for ras because neu‐transformed NOG‐8 cells grew in soft agar at a comparable level to NOG‐8 SR2 cells yet did not show any increase in TGFα production or change in EGF receptor expression.