Oncogenic Ras and transforming growth factor-beta synergistically regulate AU-rich element-containing mRNAs during epithelial to mesenchymal transition.
Colon cancer progression is characterized by activating mutations in Ras and by the emergence of the tumor-promoting effects of transforming growth factor-beta (TGF-beta) signaling. Ras-inducible rat intestinal epithelial cells (RIE:iRas) undergo a well-described epithelial to mesenchymal transition and invasive phenotype in response to H-RasV12 expression and TGF-beta treatment, modeling tumor progression. We characterized global gene expression profiles accompanying Ras-induced and TGF-beta-induced epithelial to mesenchymal transition in RIE:iRas cells by microarray analysis and found that the regulation of gene expression by the combined activation of Ras and TGF-beta signaling was associated with enrichment of a class of mRNAs containing 3' AU-rich element (ARE) motifs known to regulate mRNA stability. Regulation of ARE-containing mRNA transcripts was validated at the mRNA level, including genes important for tumor progression. Ras and TGF-beta synergistically increased the expression and mRNA stability of vascular endothelial growth factor (VEGF), a key regulator of tumor angiogenesis, in both RIE:iRas cells and an independent cell culture model (young adult mouse colonocyte). Expression profiling of human colorectal cancers (CRC) further revealed that many of these genes, including VEGF and PAI-1, were differentially expressed in stage IV human colon adenocarcinomas compared with adenomas. Furthermore, genes differentially expressed in CRC are also significantly enriched with ARE-containing transcripts. These studies show that oncogenic Ras and TGF-beta synergistically regulate genes containing AREs in cultured rodent intestinal epithelial cells and suggest that posttranscriptional regulation of gene expression is an important mechanism involved in cellular transformation and CRC tumor progression.
Kanies
Cindy L
CL
Department of Surgery, Vanderbilt University Medical Center, D-4316 Medical Center North, Nashville, TN 37232-2730, USA.
Smith
J Joshua
JJ
Kis
Christian
C
Schmidt
Carl
C
Levy
Shawn
S
Khabar
Khalid S A
KS
Morrow
Jason
J
Deane
Natasha
N
Dixon
Dan A
DA
Beauchamp
R Daniel
RD
D000818:Animals; D002465:Cell Movement; D049109:Cell Proliferation; D015179:Colorectal Neoplasms / Q000473:pathology; D051546:Cyclooxygenase 2 / Q000378:metabolism; D018450:Disease Progression; D004848:Epithelium / Q000473:pathology*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006801:Humans; D008648:Mesoderm / Q000473:pathology*; D051379:Mice; D020411:Oligonucleotide Array Sequence Analysis; D015689:Oncogene Protein p21(ras) / Q000378:metabolism*; D011485:Protein Binding; D020871:RNA Stability; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D038621:Regulatory Sequences, Ribonucleic Acid / Q000235:genetics*; D015203:Reproducibility of Results; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism
D012333:RNA, Messenger; D038621:Regulatory Sequences, Ribonucleic Acid; D016212:Transforming Growth Factor beta; D042461:Vascular Endothelial Growth Factor A; D051546:Cyclooxygenase 2; D015689:Oncogene Protein p21(ras)