title: The interdependence between catalytic activity, conformational stability, and cytotoxicity of onconase.
abstract: Onconase (ONC) is a cytotoxic ribonuclease of the pancreatic ribonuclease A superfamily isolated from oocytes or early embryos of the Northern leopard frog (Rana pipiens). It shows anticancer activity and currently is in Phase IIIb clinical trial for unresectable malignant mesothelioma. We generated several variants of ONC possessing mutations in selected structural regions of the molecule that have altered ribonucleolytic activity and/or conformational stability. The relationship between the stability and ribonucleolytic activity of these variants and their cytostatic and cytotoxic properties was investigated on several tumor cell lines. Similar to ONC, all variants were inducing reproductive cell death detected by reduced clonogenicity. The surviving cells proliferated at reduced rates as reflected by diminished size of colonies and prolongation of G(0/1) phase of the cell cycle. Some cells were undergoing apoptosis. The cytotoxic and cytostatic effects of ONC and its variants were predominantly determined by their catalytic activity rather than by conformational stability.
authors.affiliation: Martin-Luther University Halle-Wittenberg, Halle, Germany. Cindy.Schulenburg@biochemtech.uni-halle.de
authors.forename: Cindy
authors.initials: C
authors.lastname: Schulenburg
authors.forename: Barbara
authors.initials: B
authors.lastname: Ardelt
authors.forename: Wojciech
authors.initials: W
authors.lastname: Ardelt
authors.forename: Ulrich
authors.initials: U
authors.lastname: Arnold
authors.forename: Kuslima
authors.initials: K
authors.lastname: Shogen
authors.forename: Renate
authors.initials: R
authors.lastname: Ulbrich-Hofmann
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Darzynkiewicz
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry* / Q000494:pharmacology*; D017209:Apoptosis; D002384:Catalysis; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004795:Enzyme Stability; D005434:Flow Cytometry; D006801:Humans; D020128:Inhibitory Concentration 50; D011487:Protein Conformation; D012260:Ribonucleases / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; D012260:Ribonucleases; C058703:ranpirnase