Phosphorylated 4E-binding protein 1 (p-4E-BP1): a novel prognostic marker in human astrocytomas
ABSTRACT 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.
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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 · 3.53 Impact Factor
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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.02/2012; 2012:454957. DOI:10.1155/2012/454957
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ABSTRACT: Purpose: To evaluate the effects and mechanism of AMP-dependent kinase (AMPK) activator aminoimidazole carboxamide ribonucleotide (AICAR) on uveal melanoma cell lines. Methods: Four different cell lines were treated with AICAR (1-4 mM). Cell growth was assessed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) assay. Cell cycle was evaluated by flow cytometry. Expression of cell cycle control proteins, cell growth transcription factors and downstream effectors of AMPK were determined by RT-PCR and Western blots. Results: AICAR treatment led to activation of AMPK, inhibited cell growth, induced S-phase arrest and down-regulated cyclins A and D. AICAR treatment was associated with inhibition of 4E-BP1 phosphorylation, a marker of mammalian target of rapamycin (mTOR) pathway activity, without down-regulation of ribosomal protein S6 phosphorylation or changes in the macro-autophagy marker LC3B. The effects of AICAR were abolished by treatment with dipyridamole, an inhibitor of AICAR entrance into cells. Treatment with adenosine kinase inhibitor 5-iodotubericidin to inhibit the conversion of AICAR to ZMP (the direct activator of AMPK) reversed most of the growth inhibiting effects indicating that some of AICAR's anti-proliferative effect are mediated at least partially through AMPK activation. Conclusions: AICAR, after entering the cells, inhibits uveal melanoma cell growth at least partially, through activation of AMPK, inhibition of 4E-BP1 phosphorylation, and down-regulation of cyclins including cyclins A1 and D1.Investigative ophthalmology & visual science 04/2014; DOI:10.1167/iovs.13-12856 · 3.66 Impact Factor