Smad4/DPC4 silencing and hyperactive Ras jointly disrupt transforming growth factor-β antiproliferative responses in colon cancer cells Journal Article


Authors: Calonge, M. J.; Massagué, J.
Article Title: Smad4/DPC4 silencing and hyperactive Ras jointly disrupt transforming growth factor-β antiproliferative responses in colon cancer cells
Abstract: Smad4/DPC4 is a tumor suppressor gene frequently mutated or deleted in pancreatic and metastatic colon cancers. Smad4 acts as a cofactor that binds transforming growth factor-β (TGF-β) receptor-activated Smad2 and Smad3 generating transcriptional complexes. Using SW480.7 colon carcinoma cells, defective in Smad4 function, we have investigated whether this loss plays a role in the resistance of colon cancer cells to the antiproliferative effects of TGF-β. SW480.7 cells contain only one Smad4 allele, which we found encodes a wild type protein that is not expressed. We generated SW480.7 cells conditionally expressing Smad4 via an ecdysone-inducible system. Smad4 expression in these cells failed to rescue TGF-β antiproliferative and gene responses (c-myc down-regulation and induction of p21/Cip1 and plasminogen activator inhibitor-1). SW480.7 cells contain an activated Ki-ras oncogene. Hyperactivation of Ras can inhibit Smad nuclear accumulation by their phosphorylation at mitogen-activated protein kinase sites. Co-transfection into SW480.7 cells of Smad4 together with a Ras phosphorylation-resistant Smad3 (but not with wild type Smad2, Smad3, adenomatous polyposis coli (APC), or TGF-β type II receptor) restored the TGF-β antiproliferative response. These results suggest that loss of Smad4 function by both deletion and silencing and inhibition of Smad2/3 function by a hyperactive Ras pathway jointly prevent TGF-β antiproliferative responses in SW480.7 colon cancer cells.
Keywords: mitogen activated protein kinase; controlled study; protein phosphorylation; gene mutation; human cell; gene deletion; dna-binding proteins; cell proliferation; animals; cell division; gene expression; smad3 protein; transforming growth factor beta; cell line; protein binding; colonic neoplasms; alleles; gene function; tumor cells, cultured; gene activation; gene disruption; colon cancer; cancer cell; gene loss; base sequence; ras protein; trans-activators; gene silencing; ras proteins; dna primers; smad4 protein; allelism; humans; human; priority journal; article
Journal Title: Journal of Biological Chemistry
Volume: 274
Issue: 47
ISSN: 0021-9258
Publisher: American Society for Biochemistry and Molecular Biology  
Date Published: 1999-11-19
Start Page: 33637
End Page: 33643
Language: English
DOI: 10.1074/jbc.274.47.33637
PUBMED: 10559252
PROVIDER: scopus
DOI/URL:
Notes: Article -- Export Date: 16 August 2016 -- Source: Scopus
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  1. Joan Massague
    389 Massague