Suppression of tumorigenesis and induction of p15ink4b by Smad4/DPC4 in human pancreatic cancer cells

Bailu Peng, Jason B. Fleming, Tara Breslin, Ana M. Grau, Shuichi Fojioka, James L. Abbruzzese, Douglas B. Evans, Dan Ayers, Kyle Wathen, Tianai Wu, Kimberly D. Robertson, Paul J. Chiao

Research output: Contribution to journalArticlepeer-review

54 Scopus citations

Abstract

Purpose: The tumor suppressor gene Smad4/DPC4, a key transcription factor in transforming growth factor β (TGF-β) 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-β-mediated expression of cell-cycle regulatory genes p15ink4b and p21waf1. 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-β downstream target gene p21waf1, regulation of the p15ink4b 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 p15ink4b, p21waf1, and TGF-β-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 p15ink4b promoter. The p15ink4b promoter reporter gene assays revealed that Smad4-dependent transcriptional activation is mediated by this SBE, which indicates that p15ink4b is one of the downstream target genes regulated by Smad/DPC4. Conclusion: These results explain the role of Smad4/DPC4 in TGF-β-mediated inhibition of cell proliferation in vitro and in vivo. Moreover, these results suggest that Smad4/DPC4-mediated tumor suppression and induction of TGF-β-regulated cell-cycle-inhibitory genes may depend on additional factors that are absent in CFPac-1 cells.

Original languageEnglish (US)
Pages (from-to)3628-3638
Number of pages11
JournalClinical Cancer Research
Volume8
Issue number11
StatePublished - Nov 1 2002

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

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