Phosphorylated 4E-binding protein 1 (p-4E-BP1): a novel prognostic marker in human astrocytomas

Korkolopoulou P, Levidou G, El-Habr E A, Piperi C, Adamopoulos C, Samaras V, Boviatsis E, Thymara I, Trigka E-A, Sakellariou S, Kavantzas N, Patsouris E & Saetta A A ?(2012) Histopathology similar to 61, 293305 Phosphorylated 4E-binding protein 1 (p-4E-BP1): a novel prognostic marker in human astrocytomas Aims: To investigate the significance of the mammalian target of rapamycin (mTOR) pathway in astrocytic tumours, published information in this context being limited, especially regarding phosphorylated 4E-binding protein (p-4E-BP) 1. Methods and results: Paraffin-embedded tissue from 111 patients with astroglial tumours (grades IIIV) was investigated for the association of phosphorylated mTOR (p-mTOR) signalling components with phosphorylated extracellular signal-related kinase 1/2 (p-ERK1/2) and phosphorylated AKT (p-AKT) expression, clinicopathological features, angiogenesis, isocitrate dehydrogenase 1 (IDH1)-R132H, and survival. Expression was also quantified by western blot analysis in 12 cases and in three primary glioma cell cultures following rapamycin treatment. p-mTOR expression correlated with p-4E-BP1 expression and marginally with p-p70S6K expression. p-4E-BP1 expression increased with tumour grade. Rapamycin induced a decline in phosphorylation levels of all three proteins. Nuclear p-AKT and cytoplasmic p-ERK1/2 immunoexpression correlated with p-4E-BP1 expression, whereas cytoplasmic p-AKT expression correlated with p-p70S6K expression. All three proteins were associated with increased angiogenesis but not with IDH1-R132H expression status. p-mTOR adversely affected overall and disease-free survival in univariate analysis. In multivariate survival analysis, the presence of p-4E-BP1 predicted shortened overall survival in the entire cohort and glioblastomas. Conclusions: mTOR signalling components are differentially involved in the acquisition of a more aggressive and angiogenic phenotype in astrocytic tumours. Moreover, p-4E-BP1 emerges as a novel prognostic marker, which might aid in the selection of patients who are more likely to benefit from therapy with mTOR inhibitors.