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The interdependence between catalytic activity, conformational stability, and cytotoxicity of onconase

Cindy Schulenburg1, Barbara Ardelt, Wojciech Ardelt

  • 1Martin-Luther University Halle-Wittenberg, Halle, Germany. Cindy.Schulenburg@biochemtech.uni-halle.de

Cancer Biology & Therapy
|July 20, 2007
PubMed

Insights

Onconase (ONC), a frog-derived ribonuclease, demonstrates anticancer effects. Its cytotoxic and cytostatic properties on tumor cells are primarily driven by catalytic activity, not conformational stability.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Oncology

Background:

  • Onconase (ONC) is a cytotoxic ribonuclease from Rana pipiens with demonstrated anticancer activity.
  • ONC is currently in Phase IIIb clinical trials for unresectable malignant mesothelioma.

Purpose of the Study:

  • To investigate the relationship between structural variants of Onconase, their ribonucleolytic activity, conformational stability, and their anticancer properties.
  • To determine whether catalytic activity or conformational stability is the primary driver of ONC's cytostatic and cytotoxic effects.

Main Methods:

  • Generation of Onconase variants with mutations in specific structural regions.
  • Assessment of ribonucleolytic activity and conformational stability of ONC variants.
  • Evaluation of cytostatic and cytotoxic effects on various tumor cell lines, including clonogenicity, cell cycle progression, and apoptosis induction.

Main Results:

  • All Onconase variants induced reproductive cell death and reduced clonogenicity in tumor cells.
  • Surviving cells exhibited reduced proliferation rates, smaller colony sizes, and prolonged G(0/1) phase.
  • Cytotoxic and cytostatic effects were mainly determined by the catalytic activity of the variants, rather than their conformational stability.

Conclusions:

  • The catalytic activity of Onconase is the key determinant of its anticancer efficacy.
  • Structural modifications influencing ribonucleolytic activity are more critical for Onconase's therapeutic potential than those affecting conformational stability.

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