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Background/aim Glioblastoma multiforme is the most malignant type of glioma. Alpha-bisabolol is an essential oil reported as a potent cell death agent. In the present work, we evaluated the effect of alpha-bisabolol on ecto-5'-nucleotidase/CD73, the most well-characterized enzymatic source of adenosine, present in lipid rafts. Materials and methods Glioma cells were treated with alpha-bisabolol and, in some experiments, pre-treated with an A3 antagonist. MTT assay (viability), malachite green method (ecto-5'-nucleotidase/CD73 activity) and quantitative polymerase chain reaction (qPCR) (A3 mRNA) were carried out. Results Alpha-bisabolol led to a decrease in C6 and U138-MG glioma cells viability, accompanied by an increase in ecto-5'-NT/CD73 activity. Pre-treatment with an A3 antagonist reverted the effect of α-bisabolol with an increase of mRNA expression of this receptor. Conclusion Our data indicated the participation of ecto-5'-nucleotidase/CD73 and A3 receptor in the anti-proliferative effect of α-bisabolol on glioma cells.

Glioblastoma multiforme (GBM) is a deadly cancer characterized by a pro-tumoral immune response. T-regulatory (Treg) lymphocytes suppress effector immune cells through cytokine secretion and the adenosinergic system. Ecto-5'-nucleotidase/CD73 plays a crucial role in Treg-mediated immunosuppression in the GBM microenvironment (GME). Methotrexate (MTX) is an immunosuppressive drug that can increase the extracellular concentration of adenosine. In this manuscript, C6 GBM cells were treated with 1.0 μM MTX, and ecto-5'-nucleotidase/CD73 expression and extracellular AMP metabolism were analyzed in vitro. For in vivo studies, rats with implanted GBM were treated for 10 days with MTX-loaded lipid-core nanocapsules (MTX-LNCs, 1 mg/kg/day). The activity of ectonucleotidase and the expression of NTPDase1/CD39 and ecto-5'-nucleotidase/CD73 were measured. The frequencies of T lymphocytes (CD3(+)CD4(+), CD3(+)CD8(+), and CD4(+)CD25(high)CD39(+)) were quantified. In vitro, treatment with MTX increased CD73 expression and activity in C6 cells, which is in agreement with higher levels of extracellular adenosine. In vivo, MTX-LNC treatment increased CD39 expression on CD3(+)CD8(+) lymphocytes. In addition, MTX-LNC treatment up-regulated CD73 expression in tissue isolated from GBM, a finding that is in agreement with the higher activity of this enzyme. More specifically, the treatment increased CD73 expression on CD3(+)CD4(+) and CD3(+)CD8(+) lymphocytes. Treatment with MTX-LNCs decreased the frequencies of T-cytotoxic, T-helper, and Treg lymphocytes in the GME. Although more studies are necessary to better understand the complex cross-talk mediated by supra-physiological concentrations of adenosine in the GME, these studies demonstrate that MTX treatment increases CD73 enzyme expression and AMP hydrolysis, leading to an increase in adenosine production and immunosuppressive capability.