Rapamycin induces p53-independent apoptosis through the mitochondrial pathway in non-small cell lung cancer cells
ABSTRACT The mammalian target of rapamycin (mTOR) is a key kinase acting downstream of growth factor receptor PI3K and AKT signaling, leading to processes resulting in increased cell size and proliferation through translation control. Rapamycin, a specific inhibitor of mTOR, results predominately in G1 cell cycle arrest through translation control and occasionally, cell type-dependent apoptosis by an unknown mechanism. In this study, we investigated the effect and mechanism of action of rapamycin on non-small cell lung cancer (NSCLC) cell lines with p53 mutations. Cell proliferation was evaluated by modified MTT assay. The apoptotic effect of rapamycin was measured by caspase-3 activation and flow cytometric analysis of Annexin V binding. The expression of Bcl-2 and the release of cytochrome c from mitochondria were evaluated by western blotting. We found that rapamycin induced apoptosis in NSCLC cell lines with p53 mutations. Western blot analysis demonstrated that rapamycin downregulates the expression levels of Bcl-2, which leads to increased cytochrome c release from mitochondria and subsequent activation of caspase cascades. These findings suggest that rapamycin induces p53-independent apoptosis through downregulation of Bcl-2 and the mitochondrial pathway in NSCLC cell lines as a novel antitumor mechanism.
SourceAvailable from: Roberta R Alfieri[Show abstract] [Hide abstract]
ABSTRACT: While PI3K/AKT/mTOR pathway is altered in a variety of cancers including non small cell lung cancer, abnormalities in this pathway are more common in squamous cell lung carcinoma than in adenocarcinoma of the lung. Moreover, aberrant activation of PI3K/AKT/mTOR pathway is one of the mechanisms of acquired resistance to EGFR-TK inhibitors in patients with adenocarcinoma carrying EGFR activating mutations. Several inhibitors of the PI3K pathway are undergoing evaluation in preclinical and clinical studies. These include pan and selective inhibitors of PI3K, AKT inhibitors, rapamycin and rapalogs for mTOR inhibition, dual mTORC1-mTORC2 inhibitors and dual PI3K-mTOR inhibitors. This review focuses on recent preclinical and clinical data on the efficacy of PI3K pathway inhibitors in NSCLC either as monotherapy approach or in combination with chemotherapy or with drugs that target other signaling transduction pathways.Biochemical Pharmacology 05/2014; 90(3). DOI:10.1016/j.bcp.2014.05.011 · 4.65 Impact Factor
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ABSTRACT: Background:Glyoxalase I (GI) is a cellular defence enzyme involved in the detoxification of methylglyoxal (MG), a cytotoxic byproduct of glycolysis, and MG-derived advanced glycation end products (AGEs). Argpyrimidine (AP), one of the major AGEs coming from MG modifications of proteins arginines, is a pro-apoptotic agent. Radiotherapy is an important modality widely used in cancer treatment. Exposure of cells to ionising radiation (IR) results in a number of complex biological responses, including apoptosis. The present study was aimed at investigating whether, and through which mechanism, GI was involved in IR-induced apoptosis.Methods:Apoptosis, by TUNEL assay, transcript and protein levels or enzymatic activity, by RT-PCR, western blot and spectrophotometric methods, respectively, were evaluated in irradiated MCF-7 breast cancer cells, also in experiments with appropriate inhibitors or using small interfering RNA.Results:Ionising radiation induced a dramatic reactive oxygen species (ROS)-mediated inhibition of GI, leading to AP-modified Hsp27 protein accumulation that, in a mechanism involving p53 and NF-κB, triggered an apoptotic mitochondrial pathway. Inhibition of GI occurred at both functional and transcriptional levels, the latter occurring via ERK1/2 MAPK and ERα modulation.Conclusions:Glyoxalase I is involved in the IR-induced MCF-7 cell mitochondrial apoptotic pathway via a novel mechanism involving Hsp27, p53 and NF-κB.British Journal of Cancer advance online publication, 10 June 2014; doi:10.1038/bjc.2014.280 www.bjcancer.com.British Journal of Cancer 06/2014; DOI:10.1038/bjc.2014.280 · 4.82 Impact Factor
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ABSTRACT: Catalpol is an iridoid glucoside extracted from the traditional Chinese medicinal plant called Rehmannia glutinosa, and it is reported to possess a variety of pharmacological activities. The goal of this research was to explore the effect of catalpol on the human bladder cancer cells T24. The cells were treated for different durations with various concentrations of catalpol. Then the viability, mobility, and invasiveness of the cells were determined by MTT assay and flow cytometry, respectively. Catalpol was found to significantly suppress the proliferation, migration, and invasiveness of T24 bladder cancer cells in a dose- and time-dependent manner. The results also revealed that catalpol promoted apoptosis and caused the cell-cycle arrest at G2/M phase. Furthermore, the catalpol-mediated apoptosis was found to involve the modulation of PI3K/Akt pathway and inhibit the expression of anti-apoptotic B cell lymphoma-2 (Bcl-2) family proteins. Also, the expressions of Bcl-2 proapoptotic effectors, Bcl-2-associated X protein, and Bcl-2 associated death promoter were up-regulated in the cells treated with catalpol. The enzymes involved in the ultimate process of apoptosis, active caspase-3 and poly ADP ribose polymerase were elevated, and the latter was observed to be cleaved, indicating that catalpol-accelerated cell apoptosis involved a caspase-dependent pathway. These results suggest that catalpol might serve to be a promising therapeutic agent for the treatment of human bladder cancer.Cell Biochemistry and Biophysics 11/2014; DOI:10.1007/s12013-014-0355-0 · 2.38 Impact Factor