The glutaminase activity of L-asparaginase is not required for anticancer activity against ASNS-negative cells.

Abstract

L-Asparaginase (L-ASP) is a key component of therapy for acute lymphoblastic leukemia. Its mechanism of action, however, is still poorly understood, in part because of its dual asparaginase and glutaminase activities. Here, we show that L-ASP's glutaminase activity is not always required for the enzyme's anticancer effect. We first used molecular dynamics simulations of the clinically standard Escherichia coli L-ASP to predict what mutated forms could be engineered to retain activity against asparagine but not glutamine. Dynamic mapping of enzyme substrate contacts identified Q59 as a promising mutagenesis target for that purpose. Saturation mutagenesis followed by enzymatic screening identified Q59L as a variant that retains asparaginase activity but shows undetectable glutaminase activity. Unlike wild-type L-ASP, Q59L is inactive against cancer cells that express measurable asparagine synthetase (ASNS). Q59L is potently active, however, against ASNS-negative cells. Those observations indicate that the glutaminase activity of L-ASP is necessary for anticancer activity against ASNS-positive cell types but not ASNS-negative cell types. Because the clinical toxicity of L-ASP is thought to stem from its glutaminase activity, these findings suggest the hypothesis that glutaminase-negative variants of L-ASP would provide larger therapeutic indices than wild-type L-ASP for ASNS-negative cancers.

• Authors: Wai Kin Chan, Philip L Lorenzi, Andriy Anishkin, Preeti Purwaha, David M Rogers, Sergei Sukharev, Susan B Rempe, John N Weinstein
• Journal: Blood (Blood) Vol. 123 Issue 23 Pg. 3596-606 (Jun 05 2014) ISSN: 1528-0020 [Electronic] United States
• PMID: 24659632 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)
• Copyright: © 2014 by The American Society of Hematology.

Chemical References

• Antineoplastic Agents
• Recombinant Proteins
• Asparaginase
• Glutaminase
• Aspartate-Ammonia Ligase

Topics

• Antineoplastic Agents (chemistry, therapeutic use)
• Asparaginase (chemistry, genetics, therapeutic use)
• Aspartate-Ammonia Ligase (genetics)
• Drug Resistance, Neoplasm (genetics)
• Escherichia coli (enzymology)
• Glutaminase (chemistry, genetics)
• Humans
• K562 Cells
• Models, Molecular
• Molecular Dynamics Simulation
• Mutagenesis, Site-Directed
• Precursor Cell Lymphoblastic Leukemia-Lymphoma (drug therapy)
• Recombinant Proteins (chemistry, genetics, therapeutic use)
• Tumor Cells, Cultured