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MG-2477, a new tubulin inhibitor, induces autophagy through inhibition of the Akt/mTOR pathway and delayed apoptosis in A549 cells.

ABSTRACT: We previously demonstrated that MG-2477 (3-cyclopropylmethyl-7-phenyl-3H-pyrrolo[3,2-f]quinolin-9(6H)-one) inhibits the growth of several cancer cell lines in vitro. Here we show that MG-2477 inhibited tubulin polymerization and caused cells to arrest in metaphase. The detailed mechanism of action of MG-2477 was investigated in a non-small cell lung carcinoma cell line (A549). Treatment of A549 cells with MG-2477 caused the cells to arrest in the G2/M phase of the cell cycle, with a concomitant accumulation of cyclin B. Moreover, the compound induced autophagy, which was followed at later times by apoptotic cell death. Autophagy was detected as early as 12h by the conversion of microtubule associated protein 1 light chain 3 (LC3-I) to LC3-II, following cleavage and lipid addition to LC3-I. After 48h of MG-2477 exposure, phosphatidylserine externalization on the cell membrane, caspase-3 activation, and PARP cleavage occurred, revealing that apoptotic cell death had begun. Pharmacological inhibition of autophagy with 3-methyladenine or bafilomycin A1 increased apoptotic cell death, suggesting that the autophagy caused by MG-2477 played a protective role and delayed apoptotic cell death. Additional studies revealed that MG-2477 inhibited survival signaling by blocking activation of Akt and its downstream targets, including mTOR, and FHKR. Treatment with MG-2477 also reduced phosphorylation of mTOR downstream targets p70 ribosomal S6 kinase and 4E-BP1. Overexpression of Akt by transfection with a Myr-Akt vector decreased MG-2477 induced autophagy, indicating that Akt is involved. Taken together, these results indicated that the autophagy induced by MG-2477 delayed apoptosis by exerting an adaptive response following microtubule damage.

SUBMITTER: Viola G

PROVIDER: S-EPMC3234688 | biostudies-literature | 2012 Jan

REPOSITORIES: biostudies-literature

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MG-2477, a new tubulin inhibitor, induces autophagy through inhibition of the Akt/mTOR pathway and delayed apoptosis in A549 cells.

Viola Giampietro G Bortolozzi Roberta R Hamel Ernest E Moro Stefano S Brun Paola P Castagliuolo Ignazio I Ferlin Maria Grazia MG Basso Giuseppe G

Biochemical pharmacology 20110922 1

We previously demonstrated that MG-2477 (3-cyclopropylmethyl-7-phenyl-3H-pyrrolo[3,2-f]quinolin-9(6H)-one) inhibits the growth of several cancer cell lines in vitro. Here we show that MG-2477 inhibited tubulin polymerization and caused cells to arrest in metaphase. The detailed mechanism of action of MG-2477 was investigated in a non-small cell lung carcinoma cell line (A549). Treatment of A549 cells with MG-2477 caused the cells to arrest in the G2/M phase of the cell cycle, with a concomitant ...[more]

PMID: 21964343

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Project description:Novel quinazolinone compounds have been studied in the field of drug discovery for a long time. Among their broad range of pharmacological effects, certain compounds effectively inhibit cancer cell proliferation. MJ?33 is a quinazolinone derivative with proposed anticancer activities that was synthesized in our laboratory. The present study aimed to evaluate the anticancer activity of MJ?33 in fluorouracil (5FU)?resistant colorectal cancer cells (HT?29/5FUR) and to investigate the underlying molecular mechanisms. The cell viability assay results indicated that HT?29/5FUR cell viability was inhibited by MJ?33 treatment in a concentration?dependent manner compared with the control group. The cellular morphological alterations observed following MJ?33 treatment indicated the occurrence of apoptosis and autophagy, as well as inhibition of cell proliferation in a time?dependent manner compared with the control group. The acridine orange, LysoTracker Red and LC3?green fluorescent protein staining results indicated that MJ?33 treatment significantly induced autophagy compared with the control group. The DAPI/TUNEL dual staining results demonstrated increased nuclear fragmentation and condensation following MJ?33 treatment compared with the control group. The Annexin V apoptosis assay and image cytometry analysis results demonstrated a significant increase in apoptotic cells following MJ?33 treatment compared with the control group. The western blotting results demonstrated markedly decreased Bcl?2, phosphorylated (p)?BAD, pro?caspase?9 and pro?caspase?3 expression levels, and notably increased cytochrome c and apoptotic peptidase activating factor 1 expression levels following MJ?33 treatment compared with the control group. Moreover, the expression levels of autophagy?related proteins, including autophagy related (ATG)?5, ATG?7, ATG?12, ATG?16, p62 and LC3?II, were increased following MJ?33 treatment compared with the control group. Furthermore, MJ?33?treated HT?29/5FUR cells displayed decreased expression levels of p?AKT and p?mTOR compared with control cells. The results suggested that MJ?33?induced apoptosis was mediated by AKT signaling, and subsequently modulated via the mitochondria?dependent signaling pathway. Therefore, the results suggested that suppression of AKT/mTOR activity triggered autophagy in the HT?29/5FUR cell line. In summary, the results indicated that MJ?33 inhibited HT?29/5FUR cell viability, and induced apoptosis and autophagy via the AKT/mTOR signaling pathway. The present study may provide novel insight into the anticancer effects and mechanisms underlying MJ?33 in 5FU?resistant colorectal cancer cells.

Dataset Information

MG-2477, a new tubulin inhibitor, induces autophagy through inhibition of the Akt/mTOR pathway and delayed apoptosis in A549 cells.

Publications

MG-2477, a new tubulin inhibitor, induces autophagy through inhibition of the Akt/mTOR pathway and delayed apoptosis in A549 cells.

Similar Datasets

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