Abstracts

Rationale: Glutamate is an excitatory neurotransmitter that plays a key role in cellular mechanism involved in aggressive tumor cell behavior, such as migration, proliferation and resistance to apoptosis [De Groot J., Sontheimer H. Glutamate and the biology of gliomas. Glia, 2011 Aug;59(8):1181-9]. Glioblastoma, the most common and malignant brain tumors in adults, is characterized by high proliferation/migration rate and drug resistance [Hambarddzumyan D, Bergers G. Glioblastoma: Defining Tumor Niches. Trends Cancer. 2015 Dec; 1(4): 252–265]Indeed, expression of glutamate receptors has been previously reported in human glioma cell lines [De Groot J., Sontheimer H. Glutamate and the biology of gliomas. Glia, 2011 Aug;59(8):1181-9]. The aim of this study was to evaluate the in vitro effect of perampanel, an AMPA glutamate receptor antagonist, on four human glioma cell lines (U87 and U138) in terms of proliferation, induction of apoptosis and glutamate receptor expression. Methods: Cells were exposed to different concentrations of temozolomide and perampanel, alone or in combination for different time-points. After 72h, cells were counted with a cell counter. The type of drug interaction was evaluated using the Chou-Talalay method that allows assigning a combination index (CI) value to the drug combination. Apoptosis was evaluated by Annexin V-binding assays and flow cytometry in cells treated for 24h-48 h with perampanel. Results: Exposure to perampanel for 24h was able to inhibit in vitro proliferation of both U87 and U138 cells lines with IC50=177.5 µM and IC50=196.7 µM respectively. This anti-proliferative effect was rather independent from exposure time since longer exposure (72h) did not change significantly growth inhibition (U87 IC50=215.9 µM; U138 IC50=156.9 µM for 72h treatment). Moreover, in our experimental conditions, perampanel induced high levels of apoptosis, assessed by annexin V binding assay, when U138 were treated with 300 µM (IC80) and 150 µM (IC50) concentration. Finally, the in vitro effects of the combination of perampanel with temozolomide was also evaluated and a strong synergistic effect was detected in U87 but not in U138 cell lines. miRNA profiling was evaluated and a number of perampanel-modulated miRNA possibly explaining the observed cytotoxic effect was identified. Conclusions: These preliminary data further confirm the involvement of glutamate pathway in glioma cell proliferation. Funding: EISAI provided financial support to this work