Altered ornithine decarboxylase and S-adenosylmethionine decarboxylase expression and regulation in mouse fibroblasts transformed with oncogenes or constitutively active Mitogen-Activated Protein (MAP) kinase kinase.

In the present study, the expression and the regulation of ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (SAMDC) was examined in a series of oncogene transformed cell lines. The expression of both ODC and SAMDC was found to correlate with the nature of the oncogene expressed and with the resulting cellular phenotype expressed. This study demonstrates, for the first time, that the expression of both ODC and SAMDC increases as a function of cellular transformation and, in particular, as a function of malignant progression. Ras transformed cells were shown to express a unique regulatory mechanism whereby a co-ordinate up-regulation of the expression of both ODC and SAMDC occurs (via post-transcriptional stabilization of their mRNA transcripts) in the presence of protein synthesis inhibition. Altered expression (and regulation) of both ODC and SAMDC is suggested to constitute an important part of an altered growth regulatory program inherent to oncogene transformed cells, in particular, to transformed cells capable of malignant progression.