P2X7 receptors are a potential novel target for anti-glioma therapies

Mastura Monif,David A Williams,Terence J O’Brien,Kate J Drummond,Christopher A Reid,Simon V Liubinas

doi:10.1186/s12950-014-0025-4

Abstract

Human gliomas pose significant morbidity and mortality to those afflicted by them, and currently there are no curative treatment modalities available for these highly invasive tumours. With the approval from the human ethics committee, patients diagnosed with brain tumour (glioma) were recruited for this study. At the time of surgical resection, freshly resected tumour as well as ‘peri-tumour’ tissue were taken directly from theatre to the laboratory and were successfully cultured. Confocal fluorescence microscopy techniques and immunohistochemistry were used for characterization of human glioma cultures. Dye uptake experiments and confocal microscopy were utilized for P2X7 receptor (P2X7R) pore activity. We reveal human glioma cultures to contain microglia in close association with glioma (tumour) cells. Both glioma cells and microglia were found to express the purinergic, ATP sensing, P2X7R. P2X7R protein expression was increased in microglia derived from tumour when compared to ‘peri-tumour’ tissue. The pore capacity of P2X7R in tumour-associated microglia was functional, as evidenced by dye uptake experiments. Importantly, inhibition of P2X7R with the synthetic antagonist, brilliant blue G (BBG) resulted in a significant decrease in the number of glioma cells in culture. P2X7R was found to be over-expressed in grade IV human gliomas and its pore capacity was functional. Antagonism of P2X7R with BBG resulted in a decrease in tumour cell number. This identifies P2X7R as a promising therapeutic target to combat human glioma proliferation.

Highlights

Human gliomas pose significant morbidity and mortality to those afflicted by them, and currently there are no curative treatment modalities available for these highly invasive tumours
We reveal increased P2X7 receptor (P2X7R) protein expression in microglia cultured from human brain tumour versus ‘peri-tumour’
Microglia infiltrated the clusters of tumour cells, with microglia and tumour cells being in very close proximity to one another (Figure 2)

Summary

Introduction

Human gliomas pose significant morbidity and mortality to those afflicted by them, and currently there are no curative treatment modalities available for these highly invasive tumours. Gliomas are the most common type of intrinsic brain tumour and a major cause of morbidity and mortality for those afflicted by these highly invasive tumours. In addition to tumour cells, gliomas contain microglia, which are known to contribute to the tumour mass [2]. Under normal conditions microglia assume a quiescent/ resting (ramified) phenotype, but in the setting of brain injury or neoplasia microglia become activated [2]. Activated microglia are capable of releasing various immunomodulatory molecules that could alter the course of tumourogenesis [3]. The mechanisms controlling the transition from ramified to activated microglia are not fully understood. We have recently shown that the purinergic receptor, P2X7R, is involved in this transition [4]

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Discussion

Conclusion