The expression of ecto-nucleotide pyrophosphatase/phosphodiesterase 1 (E-NPP1) is correlated with astrocytic tumor grade

Objective: Astrocytic brain tumors are subdivided in four grades. The most aggressive and invasive one is grade IV or glioblastoma multiforme (GBM). Ecto-nucleotide pyrophosphatase/phosphodiesterase-1 (E-NPP1), a membrane-bound enzyme, is involved in many cellular processes such as modulation of purinergic signalling, nucleotide recycling, regulation of extracellular pyrophosphate levels and stimulation of cell motility. In this study, the use of anti-NPP1 antibody in the determination of astrocytic tumor grade is evaluated. Materials and methods: Paraffin-embedded surgical specimens from 41 primary human astrocytic brain tumors (grade I=2; grade II=10; grade III=9: grade IV=20) and 5 control samples are immunostained against NPP1 and glial fibrillary acid protein an astrocytic marker. Results: In this communication, we report the expression of NPP1 in human astrocytic brain tumors. No expression could be detected in control tissue. We observed a remarkable up regulated expression of NPP1 in GBM. Taking the latter as 100%, grade I has a relative NPP1 staining of 7%, whereas grade II and III have a similar NPP1 expression level of 53% and 47% respectively. Conclusion: A correlation is found between the up-regulated expression of NPP1 and the grade of the astrocytic tumor. Further investigation of NPP1 expression, especially in GBM, is necessary to determine the role of NPP1 in astrocytic brain tumor progression. (C) 2010 Elsevier B.V. All rights reserved.