Transformation by oncogenic Ras expands the early genomic response to transforming growth factor beta in intestinal epithelial cells.
A substantial body of evidence implicates TGFbeta as a tumor promoter in epithelial cells that have become resistant to its tumor suppressor activity. To better understand early, genome-wide TGFbeta responses in cells resistant to growth inhibition by TGFbeta, we used microarray analysis in a well-defined cell culture system of sensitive and resistant intestinal epithelial cells. TGFbeta-regulated gene expression in TGFbeta-growth-sensitive, nontransformed rat intestinal epithelial cells (RIE-1) was compared to expression in TGFbeta-growth-resistant RIE cells stably transformed by oncogenic Ras(12V). Treatment of RIE-1 cells with 2 ng/ml TGFbeta1 for 1 hour increased the expression of eight gene sequences by 2.6-fold or more, whereas eight were down regulated 2.6-fold. In RIE-Ras(12V) cells, 42 gene sequences were upregulated and only 3 were down-regulated. Comparison of RIE and RIE-Ras(12V) identified 37 gene sequences as unique, Ras-dependent genomic targets of TGFbeta1. TGFbeta-regulation of connective tissue growth factor and vascular endothelial growth factor, two genes up-regulated in RIE-Ras cells and previously implicated in tumor promotion, was independently confirmed and further characterized by Northern analysis. Our data indicate that overexpression of oncogenic Ras in intestinal epithelial cells confers a significantly expanded repertoire of robust, early transcriptional responses to TGFbeta via signaling pathways yet to be fully elucidated but including the canonical Raf-1/MAPK/Erk pathway. Loss of sensitivity to growth inhibition by TGFbeta does not abrogate TGFbeta signaling and actually expands the early transcriptional response to TGFbeta1. Expression of some of these genes may confer to Ras-transformed cells characteristics favorable for tumor promotion.
Allen
Carl E
CE
Center for Cell and Developmental Biology, The Research Institute at Nationwide Children's Hospital and the Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH 43205, USA.
Du
Jianguo
J
Jiang
Bo
B
Huang
Qin
Q
Yakovich
Adam J
AJ
Barnard
John A
JA
D000818:Animals; D002471:Cell Transformation, Neoplastic / Q000187:drug effects / Q000235:genetics*; D002478:Cells, Cultured; D055513:Connective Tissue Growth Factor / Q000235:genetics; D018450:Disease Progression; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D011905:Genes, ras / Q000502:physiology*; D016678:Genome / Q000187:drug effects* / Q000502:physiology; D007413:Intestinal Mucosa / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D020411:Oligonucleotide Array Sequence Analysis; D051381:Rats; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics
C526316:CCN2 protein, rat; D016212:Transforming Growth Factor beta; D042461:Vascular Endothelial Growth Factor A; C467498:vascular endothelial growth factor A, rat; D055513:Connective Tissue Growth Factor