Suppression of tumorigenesis and induction of p15(ink4b) by Smad4/DPC4 in human pancreatic cancer cells. Clin Cancer Res 2002 Nov;8(11):3628-38
Date
11/14/2002Pubmed ID
12429655Scopus ID
2-s2.0-0036848885 (requires institutional sign-in at Scopus site) 59 CitationsAbstract
PURPOSE: The tumor suppressor gene Smad4/DPC4, a key transcription factorin transforming growth factor beta (TGF-beta) signaling cascades,is inactivated in 50% of pancreatic adenocarcinomas. We seek to determine the role of Smad4/DPC4 in the suppression of tumor cell growth and in the regulation of TGF-beta-mediated expression of cell-cycle regulatory genes p15(ink4b) and p21(waf1).
EXPERIMENTAL DESIGN: Smad4/DPC4 is overexpressed by adenoviral infection in CFPac-1 pancreatic cancer cells, in which the Smad4/DPC4 is homozygously deleted, and in Capan-1 pancreatic cancer cells, in which Smad4/DPC4 is not expressed. Expression of the TGF-beta downstream target gene p21(waf1), regulation of the p15(ink4b) promoter, anchorage-independent growth, and tumorigenesis were examined.
RESULTS: We demonstrate that expression of Smad4/DPC4 in Capan-1 cells reduced anchorage-independent growth by more than 50%, and inhibited xenograft tumor growth. However, overexpression of Smad4/DPC4 did not inhibit CFPac-1 cell growth. Interestingly, Smad4/DPC4 induced expression of p15(ink4b), p21(waf1), and TGF-beta-responsive reporter gene in Capan-1 but not in CFPac-1 cells. Furthermore, we found a previously unidentified Smad4 binding element (SBE) located in the region between -356 and -329 bp of the p15(ink4b) promoter. The p15(ink4b) promoter reporter gene assays revealed that Smad4-dependent transcriptional activation is mediated by this SBE, which indicates that p15(ink4b) is one of the downstream target genes regulated by Smad/DPC4.
CONCLUSION: These results explain the role of Smad4/DPC4 in TGF-beta-mediated inhibition of cell proliferation in vitro and in vivo. Moreover, these results suggest that Smad4/DPC4-mediated tumor suppression and induction of TGF-beta-regulated cell-cycle-inhibitory genes may depend on additional factors that are absent in CFPac-1 cells.
Author List
Peng B, Fleming JB, Breslin T, Grau AM, Fojioka S, Abbruzzese JL, Evans DB, Ayers D, Wathen K, Wu T, Robertson KD, Chiao PJAuthor
Douglas B. Evans MD Chair, Professor in the Surgery department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
AdenoviridaeAnimals
Blotting, Northern
Blotting, Western
Cell Cycle Proteins
Cell Division
Cell Nucleus
Cyclin-Dependent Kinase Inhibitor p15
Cyclin-Dependent Kinase Inhibitor p16
Cyclin-Dependent Kinase Inhibitor p21
Cyclins
DNA-Binding Proteins
Gene Deletion
Genes, Reporter
Homozygote
Humans
Immunoblotting
Luciferases
Mice
Mice, Nude
Neoplasm Transplantation
Pancreatic Neoplasms
Promoter Regions, Genetic
Signal Transduction
Smad4 Protein
Time Factors
Trans-Activators
Transcriptional Activation
Transfection
Transforming Growth Factor beta
Tumor Cells, Cultured
Tumor Suppressor Proteins