Glutamine synthetase expression as a valuable marker of epilepsy and longer survival in newly diagnosed glioblastoma multiforme

Abstract

BackgroundGlutamine synthetase (GS) is an astrocytic enzyme catalyzing the conversion of glutamate and ammonia to glutamine. Its up-regulation has been related to higher tumor proliferation and poor prognosis in extra-cerebral tumors. We have previously reported a GS deficiency in patients with glioblastoma multiforme (GBM) who also developed epilepsy, which is a favorable prognostic factor in glioma. Here, we investigated the prognostic value of GS expression in patients with GBM with or without epilepsy and its correlation with survival.MethodsWe conducted a clinical and histopathological study on 83 (52 males) consecutive patients with newly diagnosed GBM. Immunohistochemical expression of GS was scored semi-quantitatively on the basis of cell number, staining intensity, and distribution of immunoreactive cells. Several clinical and neuropathological variables were analyzed in relation to survival and GS expression.ResultsMedian age at diagnosis was 62 years. At the last evaluation, with a median follow-up of 11.5 months (range, 1.5-58 months), 5 patients (6%) were still alive and 78 (94%) were dead. GS expression patterns in neoplastic cells were inversely correlated to the presence of epilepsy (P