Transcription repression in oncogenic transformation: common targets of epigenetic repression in cells transformed by Fos, Ras or Dnmt1.

Fos and Ras function in both dependent and independent signal transduction pathways, and sustained activity of either oncogene is sufficient to induce cell transformation and tumorigenesis. Increased DNA (cytosine-5) methyltransferse (Dnmt1) activity is involved in the mechanism of transformation by both oncogenes, suggesting that inappropriate epigenetic transcription regulation may be a common route of oncogenesis, and that cell transformation may model aspects of the epigenetic deregulation that often occurs in tumors. Here, we have taken a microarray-based gene expression approach to identify differentially expressed genes in cells transformed by c-fos, v-fos, ras or Dnmt1. The cohort of genes differentially expressed in all four transformation systems includes an over-representation of repressed genes, many of which have been functionally implicated in the suppression of transformation or tumorigenesis. Furthermore, we identified four potential tumor suppressor genes subject to epigenetic transcriptional repression in transformed cells. The results emphasize the role of transcription repression in oncogenesis, and they provide insights into the potential common epigenetic mechanisms impacting cell transformation.