Expression of asparagine synthetase predicts in vitro response to l-asparaginase in canine lymphoid cell lines

Abstract

l-asparaginase (L-asp), a bacterial enzyme that depletes extracellular asparagine, is used to treat acute lymphoblastic leukemia in humans and a variety of aggressive lymphoid malignancies in dogs. Resistance to this drug is an important cause of treatment failure in both species. Using canine lymphoid cell lines, we found that L-asp sensitivity is strongly negatively correlated with the level of methylation of the asparagine synthetase (ASNS) promoter. Selection for in vitro resistance was accompanied by increased ASNS promoter methylation and decreased ASNS mRNA expression. In addition, treatment with the hypomethylating agent 5-azacytidine increased resistance to L-asp. ASNS methylation and expression is not predictive of overall survival or progression-free survival in canine lymphoma patients treated with L-asp. Our data suggest that ASNS is an important factor in mediating the in vitro response of canine lymphoid cells to L-asp; however, resistance mechanisms may be more complex in dogs treated clinically with L-asp, potentially due to concurrent treatments.

Keywords::

• Asparagine synthetase
• methylation
• l-asparaginase
• lymphoma
• comparative oncology

Acknowledgements

Special thanks are given to to Michael Kingberg and Annice Wei for their valuable insights. Additional thanks go to Raisa Jones and Brandon Mullins for experimental troubleshooting.

Potential conflict of interest:

Disclosure forms provided by the authors are available with the full text of this article at www.informahealthcare.com/lal.

This work was supported by a developmental grant from the North Carolina University Cancer Research Fund administered by the Lineberger Comprehensive Cancer Center to K.L.R. and S.E.S. K.L.R. is supported by a Mentored Research Scholar Grant in Applied and Clinical Research (MSRG-12–086-01-TBG) from the American Cancer Society and is a funded investigator in the UNC Institute for Pharmacogenomics and Individualized Therapy. S.E.S. was supported by grants from the Ohio Animal Health Foundation and Morris Animal Foundation (#D07CA-065) and is a member of the North Carolina State Center for Comparative Medicine and Translational Research. T.L.S. was supported by an NRSA in Genetics Training Grant (T32 GM09092-35).