345P - A new L-asparaginase as a promising biodrug to acute lymphoblastic leukemia treatment

Date 18 December 2016
Event ESMO Asia 2016 Congress
Session Poster lunch
Topics Anti-Cancer Agents & Biologic Therapy
Leukaemia
Presenter Leonardo Schultz
Citation Annals of Oncology (2016) 27 (suppl_9): ix104-ix111. 10.1093/annonc/mdw586
Authors L. Schultz1, G. Monteiro2, A. Pessoa-Jr2, M.A. de Oliveira1
  • 1Biology, Sao Paulo State University, 11380-972 - Sao Vicente/BR
  • 2Biochemical And Pharmaceutical Technology, University of São Paulo, 05508-000 - São Paulo/BR

Abstract

Background

Bacterial L-asparaginases (L-ASNase) are tetrameric enzymes of high molecular weight (∼140kDa) used as therapeutic proteins for treatment of acute lymphoblastic leukemia (ALL), since this kind of tumor cell is dependent on the availability of extracellular L-asparagine (Asn). Bacterial L-ASNase hydrolyzes efficiently Asn into aspartate (Asp) and ammonia, decreasing the source of Asn to tumor cells. International pharmaceutical industries produce L-ASNase from Escherichia coli and Erwinia chrysanthemi, but several side effects are associated with L-ASNase administration, including immunological reactions, neurotoxicity, among others. Furthermore, its use in patients often results in a rapid decay of circulating L-ASNase levels, leading to high frequency of the administration. Therefore, it is essential to search new sources of this enzyme in order to increase its availability as a drug, to reduce side effects. In this context, the biodiversity is an important source to find new biopharmaceuticals.

Methods

In this work we have characterized by molecular biology and biochemical approaches, a new enzyme named ASNaseS with high homology with the bacterial counterparts (∼50% similarity), which may be a potential alternative in the treatment of the ALL. The structure of the enzyme was characterized by circular dichroism spectroscopy (CD) and by size exclusion chromatography (SEC), the biochemical assays were performed by L-glutamic dehydrogenase-coupled spectrophotometric assay as also by colorimetric assay using Nessler’s reagent.

Results

The CD data revealed an α/β structure containing ∼16% of α-helix and ∼35% of β-sheets and elevated thermoresistence (> 50ºC). SEC analysis showed that enzyme possess low molecular weight (∼44 kDa) in solution, a very contrasting result with bacterial counterparts. Evaluation of L-ASNase activity showed that the L-ASNaseM has kcat = 0.414 s−1, Km = 4.18 mM and kcat/Km = 99 M−1s−1, the activity specific is 5.6 U/mg.

Conclusions

The results suggest that L-ASNaseM may be a promising alternative biopharmaceutical to ALL treatment. Additionally, site-directed mutagenesis approaches aiming to improve the enzyme properties are in progress.

Clinical trial indentification

Legal entity responsible for the study

UNESP and USP.

Funding

FAPESP (São Paulo Research Foundation, Proc. n.2013/08617-7).

Disclosure

All authors have declared no conflicts of interest.