Sequential activation of NFAT and c-Myc transcription factors mediates the TGF-beta switch from a suppressor to a promoter of cancer cell proliferation

J Biol Chem. 2010 Aug 27;285(35):27241-27250. doi: 10.1074/jbc.M110.100438. Epub 2010 Jun 1.

Abstract

Transforming growth factor beta (TGF-beta) has a dual role in carcinogenesis, acting as a growth inhibitor in early tumor stages and a promoter of cell proliferation in advanced diseases. Although this cellular phenomenon is well established, the underlying molecular mechanisms remain elusive. Here, we report that sequential induction of NFAT and c-Myc transcription factors is sufficient and required for the TGF-beta switch from a cell cycle inhibitor to a growth promoter pathway in cancer cells. Mechanistically, TGF-beta induces in a calcineurin-dependent manner the expression and activation of NFAT factors, which then translocate into the nucleus to promote c-Myc expression. In response to TGF-beta, activated NFAT factors bind to and displace Smad3 repressor complexes from the previously identified TGF-beta inhibitory element (TIE) to transactivate the c-Myc promoter. c-Myc in turn stimulates cell cycle progression and growth through up-regulation of D-type cyclins. Most importantly, NFAT knockdown not only prevents c-Myc activation and cell proliferation, but also partially restores TGF-beta-induced cell cycle arrest and growth suppression. Taken together, this study provides the first evidence for a Smad-independent master regulatory pathway in TGF-beta-promoted cell growth that is defined by sequential transcriptional activation of NFAT and c-Myc factors.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcineurin / genetics
  • Calcineurin / metabolism
  • Cell Cycle*
  • Cell Line, Tumor
  • Humans
  • Mice
  • NFATC Transcription Factors / genetics
  • NFATC Transcription Factors / metabolism*
  • Neoplasms / genetics
  • Neoplasms / metabolism*
  • Proto-Oncogene Proteins c-myc / genetics
  • Proto-Oncogene Proteins c-myc / metabolism*
  • Smad Proteins / genetics
  • Smad Proteins / metabolism
  • Transcription, Genetic*
  • Transcriptional Activation / drug effects
  • Transcriptional Activation / genetics
  • Transforming Growth Factor beta / metabolism*
  • Transforming Growth Factor beta / pharmacology

Substances

  • MYC protein, human
  • NFATC Transcription Factors
  • Proto-Oncogene Proteins c-myc
  • Smad Proteins
  • Transforming Growth Factor beta
  • Calcineurin