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Signaling pathways regulating TC21-induced tumorigenesis

Mete Erdogan1, Ambra Pozzi, Neil Bhowmick

  • 1Department of Cancer Biology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA.

The Journal of Biological Chemistry
|July 28, 2007
PubMed

Insights

TC21 (R-Ras2) overexpression drives cancer progression by activating key signaling pathways like PI3K and mTOR. These transformed cells become resistant to TGF-beta

Area of Science:

  • Oncology
  • Cell Biology
  • Molecular Biology

Background:

  • TC21 (R-Ras2) is a Ras-related GTPase involved in human cancer pathogenesis.
  • Transforming growth factor beta (TGF-beta) has complex roles in tumorigenesis, inhibiting normal cells but promoting proliferation in Ras-transformed cells.
  • The precise mechanisms of TC21-induced tumor formation and TGF-beta's regulation of TC21-transformed cells remain unclear.

Purpose of the Study:

  • To investigate the role of TC21 in cancer progression.
  • To elucidate the signaling pathways mediating TC21-induced transformation.
  • To determine how TGF-beta affects TC21-transformed cells.

Main Methods:

  • Overexpression of an activated G23V mutant of TC21 in EpH4 murine mammary epithelial cells.
  • In vitro and in vivo oncogenicity assays.
  • Analysis of signaling pathway activation (p38 MAPK, mTOR, PI3K, Akt/PKB) and TGF-beta response.

Main Results:

  • Mutant TC21-expressing cells exhibited significantly higher oncogenicity than those expressing activated H-Ras.
  • TC21-induced transformation and proliferation were dependent on p38 MAPK, mTOR, and phosphoinositide 3-kinase activation, but not Akt/PKB.
  • TC21-transformed cells became insensitive to TGF-beta's growth inhibitory effects, with increased soft agar growth upon TGF-beta stimulation.
  • Smad-dependent and independent pathways remained functional despite loss of TGF-beta growth inhibition response.

Conclusions:

  • Overexpression of active TC21 promotes tumorigenicity via the PI3K, p38 MAPK, and mTOR pathways.
  • TC21 transformation confers resistance to the normal growth-inhibitory functions of TGF-beta.
  • Understanding these pathways is crucial for targeting TC21 in cancer therapy.

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