Use of representational difference analysis to study the effect of TGFB onthe expression profile of a pancreatic cancer cell line

It has been shown that TGFBs, their receptors, or downstream targets show g enetic alterations in pancreatic cancer. This study was designed to identif y transcriptional alterations induced by prolonged treatment of pancreatic cancer cell lines with TGFB. The TGFB-responsive PANC-I cell line was treat ed with 10-ng/ml TGFB1 for 24 hr. cDNA representational difference analysis was used to generate subtracted hybridization probes enriched for TGFB reg ulated genes. These probes were hybridized on gridded arrays of cDNA clones containing genes differentially expressed in pancreatic cancer. Twenty-sev en distinct cDNA clones were shown to be TGFB target genes. Eleven genes we re upregulated by TGFB and were associated with extracellular matrix compos ition and formation, including genes usually transcribed by cells of mesenc hymal origin only. Transcript levels of 16 genes were downregulated by TGFB and could mainly be classified into markers of epithelial differentiation and genes involved in the transcriptional and translational machinery. In c onclusion, a 24-hr treatment of PANC-I cells with TGFB induced a loss of ep ithelial and a gain of mesenchymal markers. As in other tumors, this epithe lial-mesenchymal transdifferentiation may be of general importance during p ancreatic carcinogenesis, and may participate, e.g., in the development of the desmoplastic reaction or the acquisition of an invasive phenotype of pa ncreatic tumor cells. This study demonstrates the usefulness of cDNA RDA an d gridded clone libraries to study the effect of signaling cascades on the expression profile of tumor cells. Similar approaches may be helpful in the context of the genome project for the characterization of novel genes. (C) 1999 Wiley-Liss, Inc.