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.
Paraffin-embedded tissue from 111 patients with astroglial tumours (grades II-IV) 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.
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.
"The crucial role of 4E-BP1 as a key effector of the AKT and ERK signaling pathways in tumors has been elegantly studied by She et al . Moreover, high expression levels of 4E-BP1 have been found to have prognostic value in several tumor types [33-37]. Therefore, further exploration of targeting 4E-BP1 should be explored in the future for multiple tumor types, including, and especially, pancreatic cancer. "
[Show abstract][Hide abstract] ABSTRACT: Patients with pancreatic cancer have dismal prognoses, and novel therapies are urgently needed. Mutations of the KRAS oncogene occur frequently in pancreatic cancer and represent an attractive target. Direct targeting of the predominant KRAS pathways have been challenging and research into therapeutic strategies have been now refocused on pathways downstream of KRAS, phosphoinositide 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK [MEK]). We hypothesized that concurrent inhibition of the PI3K and MEK pathways would result in synergistic antitumor activity, as it would circumvent the compensatory feedback loop between the two pathways. We investigated the combined effect of the PI3K inhibitor, GDC0941, and the MEK inhibitor, AZD6244, on cell viability, apoptosis and cell signaling in a panel of pancreatic cancer cell lines. An in vivo analysis was conducted on pancreatic cancer xenografts. While BxPC-3 (KRAS wild type) and MIA PaCa-2 (KRAS mutated) cell lines were sensitive to GDC0941 and AZD6244 as single agents, synergistic inhibition of tumor cell growth and induction of apoptosis were observed in both cell lines when the two drugs were combined. Interestingly, phosphorylation of the cap-dependent translational components, 4E-binding protein (p-4E-BP1) and S6 was found to be closely associated with sensitivity to GDC0941 and AZD6244. In BxPC-3 cell xenografts, survival differences were observed between the control and the AZD6244, GDC0941, and combination groups. Our study provides the rationale for concurrent targeting of the PI3K and MEK pathways, regardless of KRAS status, and suggests that phosphorylation of 4E-BP1and S6 can serve as a predictive biomarker for response to treatment.
PLoS ONE 10/2013; 8(10):e77243. DOI:10.1371/journal.pone.0077243 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Phosphorylation of eukaryotic translation initiation factor 4E (eIF4E) binding protein (4E-BP1) results in release of eIF4E, which sequentially relieves translational repression and enhances oncogenic protein synthesis. We assessed the expression of phosphorylated 4E-BP1 (p-4E-BP1) in non-small cell lung cancer (NSCLC) and its correlation with clinicopathological parameters and patient survival. In addition, we investigated whether phosphorylation site made a difference in outcome. Tissue microarray blocks were generated from 73 NSCLC samples and immunohistochemically stained for p-4E-BP1 Thr37/46 and p-4E-BP1 Thr70. Both p-4E-BP1 Thr37/46 and p-4E-BP1 Thr70 were more highly expressed in squamous cell carcinoma than in adenocarcinoma (P = 0.006 and P = 0.003, respectively). Expression of p-4E-BP1 Thr70 was higher in tumours with a diameter larger than 3 cm (P = 0.024) and nodal metastasis (P = 0.053). High p-4E-BP1 Thr70 expression significantly correlated with worse overall survival (P = 0.001) and was an independent prognostic factor (hazard ratio 2.64, P = 0.004). p-4E-BP1 Thr37/46 had no prognostic significance. Phosphorylation site affected the prognostic significance of p-4E-BP1. p-4E-BP1 Thr70 is a candidate biomarker to predict poor prognosis in patients with NSCLC.
International journal of clinical and experimental pathology 06/2015; 8(4):3955-3962. · 1.89 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Astrocytomas, the most common type of gliomas, and especially grade IV glioblastomas are "endowed" with strong proliferation and invasion potentials, high recurrence rate, and poor patients' prognosis. Aberrant signaling of AKT-mTOR (mammalian target of rapamycin) has been implicated in carcinogenesis. This paper is focused on the impact of deregulated AKT-mTOR signaling components in the clinical outcome and prognosis of human astrocytomas. Current therapeutic targeting of astrocytomas with AKT-mTOR inhibitors in preclinical and clinical stage is also discussed, including future perspectives regarding the management of these devastating tumors.
Neurology Research International 02/2012; 2012:454957. DOI:10.1155/2012/454957
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