¹UC Davis Cancer Center and Division of Hematology and Oncology, UC Davis School of Medicine, Sacramento, CA, USA

Correspondence: R Wisdom, UC Davis Cancer Center and Division of Hematology and Oncology, UC Davis School of Medicine, Research Bldg III, Room 1100, 4645 2nd Ave., Sacramento, CA 95817, USA. E-mail: ronald.wisdom@ucdmc.ucdavis.edu

Received 21 March 2005; Revised 29 April 2005; Accepted 18 May 2005; Published online 11 July 2005.

Abstract

Ras, Raf, and Fos function as components in a signal transduction pathway that is constitutively active in many cancers. Many of the changes that underlie cell transformation arise through changes in gene expression. We have used gene expression profiling of 3T3 cells transformed by Ras, Raf, and Fos to define the common and distinct targets of transcriptional control by each of these oncogenes. In this analysis, the most strongly conserved feature of cell transformation at the transcriptional level is the transcriptional repression of genes that encode components of the extracellular matrix (ECM). TGF- treatment of fibroblasts is known to increase production of ECM, suggesting that TGF- might selectively reverse some of the gene expression changes that occur during cell transformation. Using gene expression profiling of the TGF- response, we show that the ability of TGF- to reverse the changes in gene expression brought about by cellular transformation is essentially confined to genes that encode components of the ECM and the cytoskeleton. This selective reversal of transformation-induced changes in gene expression is associated with partial reversal of many parameters of cell transformation. The results demonstrate a correlation between gene repression by the Ras/Raf/ERK signaling pathway, gene activation by the TGF- signaling pathway, and the transformed phenotype in fibroblasts.