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 12 h 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 48 h 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.
A novel series of 3-alkyl-substituted 7-phenyl-3H-pyrrolo[3,2-f]quinolin-9-ones (7-PPyQs) was synthesized with the aim to optimize the cytotoxic activity of recently identified PPyQs, promising inhibitors of tubulin polymerization. All compounds inhibited the growth of 11 human tumor cell lines at submicromolar concentrations as well as two human resistant cancer sublines, A549-T12 and A549-T24. FACS analysis indicated that all compounds caused significant arrest of the A549 cell cycle in G2/M phase at 0.1 and 1 muM and a good correlation between the cytotoxicity IC50 and their ability to block the cell cycle was observed.
The newly synthesized 7-phenyl-3H-pyrrolo[3,2-f]quinolinones 16-26 and previously 27 and 28 were assayed for their in vitro antiproliferative activity on tumor cell lines, and the lead compound 16 in vivo on a singenic hepatocellular carcinoma in Balb/c mice. Results from FACS, immunofluorescence microscopy analysis, tubulin polymerization assay, and tritiated water release assay for the CYP19 activity confirmed the new compounds as potential anticancer agents acting by tubulin depolymerization, but devoid of aromatase activity unlike their geometric [2,3-h] isomers.
In our search for potential new anticancer drugs, we designed and synthesized a series of tricyclic compounds containing the antimitotic 2-phenylazaflavone chromophore fused to a pyrrole ring in a pyrroloquinoline structure. Compounds 8, 18, 19, 22, 23, 25 and 26, when tested against a panel of fourteen human tumor cell lines, showed poor in vitro cytotoxic activity, whereas 20, 21 and 24 showed significant activity (IC(50) 0.7 to 50 microM). Steroid hormone-sensitive ovary, liver, breast and adrenal gland adenocarcinoma cell lines displayed the highest sensitivity (IC(50) 0.7 to 8 microM). Compound 24 blocked cells in the G(2)/M phase of the cell cycle and induced a significant increase in apoptotis. Compounds 20, 21 and 24 proved to alter microtubule assembly and stability, displaying a cytoplasmic microtubule network similar to that caused by Vincristine. In vivo, administration of compound 24 to Balb/c mice inhibited the growth of a syngenic hepatocellular carcinoma.
In view of a possible application to aluminium(III) chelation therapy, 3-hydroxy-4-pyridinecarboxylic acid (3H4P) and 4-hydroxy-3-pyridinecarboxylic acid (4H3P) were synthesised, and their chemical interactions with the metal ion were investigated in aqueous 0.6 m (Na)Cl at 25°C by means of potentiometric titrations. Only mononuclear complexes of the type AlL l H h (l = 1, 2 and 3; h = 0, 1, ..., l) were formed. The qualitative and quantitative results obtained were confirmed by UV spectrophotometry and 1 H NMR spectroscopy. The efficiencies of the ligands to chelate aluminium(III) were evalu-
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