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 decarb oxylase (ODC) and S-adenosylmethionine decarboxylase (SAMDC) was examined i n a series of oncogene transformed cell lines. The expression of both ODC a nd SAMDC was found to correlate with the nature of the oncogene expressed a nd with the resulting cellular phenotype expressed. This study demonstrates , for the first time, that the expression of both ODC and SAMDC increases a s a function of cellular transformation and, in particular, as a function o f malignant progression. Ras transformed cells were shown to express a uniq ue regulatory mechanism whereby a co-ordinate up-regulation of the expressi on of both ODC and SAMDC occurs (via post-transcriptional stabilization of their mRNA transcripts) in the presence of protein synthesis inhibition. Al tered expression (and regulation) of both ODC and SAMDC is suggested to con stitute an important part of an altered growth regulatory program inherent to oncogene transformed cells, in particular, to transformed cells capable of malignant progression.