Pharmacological characterisation of nicotinic acetylcholine receptors expressed in glioma and glioblastoma cells

Gliomas and glioblastomas (GBMs) are a family of highly proliferative, migratory and invasive malignant brain tumours arising from different glial elements and more than 70% of the affected patients die within two years of diagnosis. Cigarette smoke is an environmental risk factor for the induction and development of human malignancies, and many glioma patients are cigarette smokers. The aim of this study was to characterise the nAChRs in gliomas and glioblastoma cells, analyse whether they regulate cell proliferation and intracellular signalling and investigate whether this signalling is modulated by nicotine. Quantitative real-time PCR confirmed the expression of a number of nAChR subunits in the U87MG glioma cell line and in primary glioblastoma cultures derived from patients at different tumoral stages. MTS assay and cell counting showed that nicotine, in a dose-dependent manner, significantly increased cell proliferation. These effects were blocked by co-treatment of the cells with specific nAChR antagonists. We also found that treatment of glioma cell line and glioblastoma cells with stylbene-derived antagonists reduced the viability of the cells in a dose-dependent manner, but had no effect on neuroblastoma and hepatocyte cells. Moreover, we found that nicotine exposure induced a time-dependent changes in the phosphorylation of Erk and Akt, and these changes are prevented by co-incubation of the cells with nicotinic antagonists. Collectively, our data suggest that nicotine activates signalling pathways involved in the proliferation and invasiveness of glioma and glioblastoma cells and, α-bungarotoxin-sensitive receptors mediate these effects, thus representing a possible target for new therapeutic strategies.