Rapamycin induces p53-independent apoptosis through the mitochondrial             pathway in non-small cell lung cancer cells.
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.
Division of Medical Oncology and Molecular Respirology, Department                     of Multidisciplinary Internal Medicine, Tottori University, 36-1 Nishi-cho,                     Yonago-shi, Tottori-ken 683-8504, Japan.
Naomi
N
Miyake
Hiroki
H
Chikumi
Miyako
M
Takata
Masaki
M
Nakamoto
Tadashi
T
Igishi
Eiji
E
Shimizu
D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D002289:Carcinoma, Non-Small-Cell Lung; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D045304:Cytochromes c / Q000378:metabolism; D006801:Humans; D008175:Lung Neoplasms; D008928:Mitochondria / Q000378:metabolism*; D009154:Mutation; D020123:Sirolimus / Q000494:pharmacology*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
D000903:Antibiotics, Antineoplastic; D051017:Apoptosis Regulatory Proteins; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D045304:Cytochromes c; C505407:CASP3 protein, human; D053148:Caspase 3; D020123:Sirolimus