Thermococcus kodakarensis-derived L-asparaginase: a candidate for the treatment of glioblastoma

Abstract

L-Asparaginase is a chemotherapeutic agent against various types of cancer due to its asparagine depleting ability. Previously, we have characterized a highly active and thermostable L-Asparaginase (TK1656) from Thermococcus kodakarensis and reported its anti-cancerous effects against acute lymphoblastic leukemia. In the current study, we report anti-proliferative and cytotoxic effects of TK1656 on glioblastoma cell line SF767. Our results showed that TK1656 reduced the proliferation of glioblastoma cells after 72 h in a dose-dependent manner while leaving Vero cells unaffected. The IC50 of TK1656 against SF767 cells was calculated as 18 µg/mL by neutral red uptake assay. Phase-contrast microscopy showed pronounced morphological changes in TK1656 treated SF767 cells. Likewise, DAPI staining and DNA laddering showed that TK1656 has strong genotoxic effects on glioblastoma cells. The AO/EB dual staining pointed out the induction of apoptosis in TK1656 treated cells. Activation of Caspases 3, 6, and 8, after TK1656 treatment, further substantiated the notion of apoptosis mediated death in these cells. Furthermore, flow cytometry data showed that TK1656 treatment induced cell cycle arrest with an increased sub-G1 cell population and downregulation of CDK2 and CDK4. Altogether, our data revealed that TK1656 induces apoptosis and cell cycle arrest in glioblastoma cells. Our findings prompt further investigations to approve the use of TK1656 for the effective treatment of glioblastoma.