Onconase (ONC), which is an amphibian homologue of bovine pancreatic ribonuclease (RNase A), is now undergoing a human clinical trial for the treatment of cancer. ONC is delivered to patients intravenously and is able to kill cancer cells selectively. Hence, ONC has the potential to be the harbinger of a new class of cancer chemotherapeutics based on ribonucleases. Ribonuclease- based chemotherapeutic agents are unrelated to extant chemotherapeutics and thus represent a new stratagem for the clinical treatment of cancer. In contrast to ONC, neither RNase A nor its human homologue-RNase 1-is cytotoxic, despite having 10,000-fold greater catalytic activity than ONC. Moreover, only ONC is immunogenic, and its dosing is limited by renal toxicity. These differential attributes, as well as a desire to understand the biochemical mechanism by which ribonucleases exert specific antitumoral activity, motivate this research proposal.
Specific Aims. The five Specific Aims of this research proposal use ideas and methods from organic chemistry, biochemistry, molecular biology, and cell biology to reveal the mechanism by which ribonucleases exert their specific antitumoral activity, and to enhance that activity. During the next grant period, this intent will be achieved in five Specific Aims.
Aim 1 is to assess the role of cell- surface charge in ribonuclease cytotoxicity.
Aim 2 is to determine the kinetic mechanism of cytosolic entry by ribonucleases.
Aim 3 is to create targeted ribonucleases with highly selective toxicity for cancer cells.
Aim 4 is to reveal the roles of ribonuclease and its cognate inhibitor protein in vivo. Finally, Aim 5 is to use contrast agents and magnetic resonance imagining to report on ribonucleases in vivo. Significance. The results of the research proposed herein will provide a detailed biochemical understanding of the antitumoral activity of ribonucleases, and could ultimately lead to new cancer chemotherapeutics based on variants of an endogenous human enzyme, RNase 1.

Public Health Relevance

This research project is focused on the development of a new class of chemotherapeutic agents for the treatment of cancer. The agents are based on ribonuclease, which is a human enzyme that catalyzes the cleavage of RNA. The goal of the project is to obtain fundamental insights into the relationship between the amino-acid sequence of ribonuclease, its three-dimensional structure, and its biological function, and to use those insights to create novel ribonucleases of potential therapeutic utility.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Special Emphasis Panel (ZRG1-BCMB-B (02))
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Forry, Suzanne L
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University of Wisconsin Madison
Schools of Earth Sciences/Natur
United States
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Hoang, Trish T; Tanrikulu, I Caglar; Vatland, Quinn A et al. (2018) A Human Ribonuclease Variant and ERK-Pathway Inhibitors Exhibit Highly Synergistic Toxicity for Cancer Cells. Mol Cancer Ther 17:2622-2632
Thomas, Sydney P; Hoang, Trish T; Ressler, Valerie T et al. (2018) Human angiogenin is a potent cytotoxin in the absence of ribonuclease inhibitor. RNA 24:1018-1027
Chyan, Wen; Raines, Ronald T (2018) Enzyme-Activated Fluorogenic Probes for Live-Cell and in Vivo Imaging. ACS Chem Biol 13:1810-1823
Lomax, Jo E; Eller, Chelcie H; Raines, Ronald T (2017) Comparative functional analysis of ribonuclease 1 homologs: molecular insights into evolving vertebrate physiology. Biochem J 474:2219-2233
Chyan, Wen; Kilgore, Henry R; Gold, Brian et al. (2017) Electronic and Steric Optimization of Fluorogenic Probes for Biomolecular Imaging. J Org Chem 82:4297-4304
Hoang, Trish T; Raines, Ronald T (2017) Molecular basis for the autonomous promotion of cell proliferation by angiogenin. Nucleic Acids Res 45:818-831
Hoang, Trish T; Smith, Thomas P; Raines, Ronald T (2017) A Boronic Acid Conjugate of Angiogenin that Shows ROS-Responsive Neuroprotective Activity. Angew Chem Int Ed Engl 56:2619-2622
Andersen, Kristen A; Smith, Thomas P; Lomax, Jo E et al. (2016) Boronic Acid for the Traceless Delivery of Proteins into Cells. ACS Chem Biol 11:319-23
Arnold, Ulrich; Raines, Ronald T (2016) Replacing a single atom accelerates the folding of a protein and increases its thermostability. Org Biomol Chem 14:6780-5
Thomas, Sydney P; Kim, Eunji; Kim, Jin-Soo et al. (2016) Knockout of the Ribonuclease Inhibitor Gene Leaves Human Cells Vulnerable to Secretory Ribonucleases. Biochemistry 55:6359-6362

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