Andrea St. Laurent

Asparaginase (ASNase) is one of the first-lines of chemotherapy used in the treatment of acute lymphoblastic leukemia (ALL). It breaks down asparagine in the body forcing the cell to undergo apoptosis. Yet, some patients develop resistance to ASNase treatment. Asparagine is produced in the cell by the enzyme asparagine synthetase (ASNS). One explanation for resistance could be increased ASNS expression leading to the production of more asparagine than can be broken down. Here, we investigated whether ASNS levels were correlated to lower levels of ASNase induced apoptosis and whether using a competitive ASNS inhibitor, albizziine (Alb), to decrease ASNS activity would reverse ASNase resistance in leukemic cell lines. Two human leukemic cell lines with varying ASNS expression were utilized, Jurkat and HL-60. RT-qPCR analysis showed an 8.9-fold higher level of ASNS mRNA in HL-60 relative to Jurkat. In addition, HL-60 was resistant and Jurkat sensitive to ASNase-induced apoptosis. After 24 hours, 0.1 IU ASNase treatment resulted in a 43.27% increase in apoptosis in Jurkat cells, but no significant increase in HL-60 cells. The addition of the ASNS inhibitor, Alb, in combination with ASNase resulted in increased apoptosis in both cell lines. HL-60 apoptosis increased 6-fold when treated with a combination of 0.1 IU ASNase and 1mM Alb. Alb also increased Jurkat sensitivity to 0.1 IU ASNase from 43.27% apoptosis with ASNase alone to 67.15% in combination with ASNase. Alb alone did not induce any significant death. Furthermore, previous research has revealed that ASNS expression is low in normal brain tissues but elevated in high-grade neuroblastoma and cases with unfavorable prognosis. This research investigated ASNase as a potential chemotherapeutic treatment in neuroblastoma. SH-SY5Y, a human neuroblastoma cell line, was used to explore ASNase and Alb as an inducer of apoptosis. RT-qPCR analysis showed an 7.1-fold higher level of ASNS mRNA in SH-SY5Y relative to Jurkat. SH-SY5Y, when treated with 10 IU ASNase alone, was resistant to ASNase treatment. However, when 10 IU ASNase was used in combination with 10 mM Alb, it resulted in an 37.69% increase in apoptosis, a 5-fold increase. These results suggest that the ASNS inhibitor, Alb, can induce sensitivity to ASNase induced cell death in leukemic and neuroblastoma cell lines. It therefore warrants further investigation into its role in reversing chemotherapeutic resistance due to increased levels of ASNS.