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Inhibition of clonogenic tumor growth: a novel function of Smac contributing to its antitumor activity

Meike Vogler1, Stavros Giagkousiklidis, Felicitas Genze

  • 1University Children's Hospital, Prittwitzstr. 43, 89075 Ulm, Germany.

Oncogene
|August 11, 2005
PubMed

Insights

Second mitochondria derived activator of caspase (Smac) inhibits tumor growth by blocking migration and proliferation. Smac’s effects on cell viability are cell density-dependent and may offer new cancer therapy strategies.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Cancer Research

Background:

  • Second mitochondria derived activator of caspase (Smac) is known to sensitize cells for apoptosis.
  • The impact of Smac on cell viability without apoptotic stimuli was previously unclear.

Purpose of the Study:

  • To investigate the effect of Smac on cell viability, clonogenic growth, migration, and proliferation in neuroblastoma cells.
  • To determine if Smac's inhibition of clonogenic survival is linked to its apoptosis-promoting activity.

Main Methods:

  • Overexpression of full-length or processed Smac in SH-EP neuroblastoma cells.
  • Assessment of cell density-dependent effects on clonogenic survival, migration, proliferation, and apoptosis.
  • Analysis of protein and mRNA expression of apoptosis regulators (XIAP, survivin, FLIP) and cell cycle proteins (p21).

Main Results:

  • Smac inhibited clonogenic tumor growth, random migration, and proliferation in a cell density-dependent manner.
  • Smac enhanced apoptosis and inhibited protein expression of XIAP, survivin, FLIP, and p21, but not their mRNA levels.
  • Inhibition of clonogenic capacity by Smac was independent of its apoptosis-promoting activity and was reversible by increasing cell density.

Conclusions:

  • Smac restrains clonogenic tumor growth by inhibiting migration and proliferation, independent of its role in apoptosis.
  • Smac's effects are cell density-dependent, suggesting potential therapeutic applications in controlling tumor growth and metastasis.
  • Smac agonists could be valuable in cancer therapy, particularly for minimal residual disease management.

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