title: Mechanisms of induction of cell cycle arrest and cell death by cryptolepine in human lung adenocarcinoma a549 cells.
abstract: We investigated p53-dependent and -independent molecular events associated with cell cycle alteration and cell death in human lung adenocarcinoma A549 cells using cryptolepine, a DNA-damaging agent. After a 24-h treatment, cryptolepine caused an accumulation of p53 at concentrations of 1.25-10 microM and induction of p21(Cip1/WAF1) but only at concentrations up to 5muM. p21(Cip1/WAF1) was also strongly induced by cryptolepine (2.5-5 microM) in cells with p53 largely ablated via small interfering RNA-mediated gene silencing. Cryptolepine induced G1-phase block at 1.25-2.5 microM, S-phase and G2/M-phase block at 2.5-5 microM, and cell death at 10 microM. The dead cells displayed condensed and fragmented nuclei, features of apoptosis. Wortmannin, an inhibitor of ataxia telangiectasia-mutated and DNA-dependent protein kinase (DNA-PK), caused cell cycle arrest at G1 phase without inducing p53 and p21(Cip1/WAF1) expression and cell death. The addition of wortmannin partially prevented cryptolepine-induced expression of p53 and p21(Cip1/WAF1) together with the S-phase block and sensitized cells to induction of cell death. NU7026, a DNA-PK-specific inhibitor, showed neither induction of cell cycle arrest and apoptosis nor the expression of p53 and p21(Cip1/WAF1). The presence of NU7026 caused further reduction of cells in G1 phase induced by cryptolepine at 5 microM without affecting the induction of p53 and p21(Cip1/WAF1) and cell death. This study using the A549 cell as a model demonstrated that cryptolepine selects different molecular pathways to cell cycle checkpoint activation in a dose-specific manner and evokes a wortmannin-sensitive antiapoptosis response.
authors.affiliation: Biological Chemistry (Molecular Toxicology), Faculty of Natural Sciences, Imperial College London, London SW7 2AZ, United Kingdom. h.zhu@cranfield.ac.uk
authors.forename: Huijun
authors.initials: H
authors.lastname: Zhu
authors.forename: Nigel J
authors.initials: NJ
authors.lastname: Gooderham
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology*; D000470:Alkaloids / Q000494:pharmacology*; D000730:Androstadienes / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D002110:Caffeine / Q000494:pharmacology; D002453:Cell Cycle / Q000187:drug effects*; D045744:Cell Line, Tumor; D002867:Chromones / Q000494:pharmacology; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics; D004347:Drug Interactions; D005786:Gene Expression Regulation / Q000187:drug effects; D016158:Genes, p53; D006801:Humans; D026121:Indole Alkaloids; D007211:Indoles / Q000494:pharmacology*; D008175:Lung Neoplasms / Q000473:pathology*; D008856:Microscopy, Fluorescence; D009025:Morpholines / Q000494:pharmacology; D011804:Quinolines / Q000494:pharmacology*; D000077191:Wortmannin
chemical_list: C479235:2-(morpholin-4-yl)benzo(h)chromen-4-one; D000470:Alkaloids; D000730:Androstadienes; C493956:CDKN1A protein, human; D002867:Chromones; D050759:Cyclin-Dependent Kinase Inhibitor p21; D026121:Indole Alkaloids; D007211:Indoles; D009025:Morpholines; D011804:Quinolines; D002110:Caffeine; C024015:cryptolepine; D000077191:Wortmannin