Malignant gliomas are the most common and devastating primary
tumors in the brain and, despite treatment, patients with these
tumors have a poor prognosis. The participation of ecto-5'-NT/CD73 per se as a proliferative factor, being involved in the control of cell growth, differentiation, invasion, migration and
metastasis processes has been previously proposed. In the present study, we evaluated the activity and functions of ecto-5'-NT/CD73 during the proliferation process of rat C6 and human U138MG
glioma cell lines. Increasing confluences and culture times led to an increase in ecto-5'-NT/CD73 activity in both C6 and U138MG
glioma cells. RT-PCR analysis and flow cytometry analysis showed a significant increase in ecto-5'-NT/CD73
mRNA and
protein levels, respectively, comparing confluent with sub-confluent cultures in human U138MG
glioma cells.
Ecto-5'-nucleotidase/CD73 may regulate the extracellular
adenosine 5'-monophosphate (
AMP) and
adenosine levels. Treatment with 1 microM
APCP, a competitive ecto-5'-NT/CD73 inhibitor, caused a significant reduction of 30% in
glioma cell proliferation. In addition, 100 microM
adenosine increases cell proliferation by 36%, and the treatment with
adenosine plus
NBTI and
dipyridamole, produced an additional and significant increase of on cell proliferation. The inhibitory effect on cell proliferation caused by
APCP was reverted by co-treatment with
NBTI and
dipyridamole.
AMP (1 mM and 3 mM) decreased U138MG
glioma cell proliferation by 29% and 42%, respectively. Taken together, these results suggest the participation of ecto-5'-NT/CD73 in cell proliferation and that this process is dependent upon the
enzyme's production of
adenosine, a proliferative factor, and removal of
AMP, a toxic molecule for
gliomas.