title: Topoisomerase inhibitor coralyne photosensitizes DNA, leading to elicitation of Chk2-dependent S-phase checkpoint and p53-independent apoptosis in cancer cells.
abstract: The possibility of synergism between the topoisomerase inhibition by coralyne and its DNA photonicking properties being used to kill cancer cells was explored. Compared with coralyne alone, the CUVA treatment dramatically enhanced DNA damage and apoptosis in cells. Despite causing an increased p53 expression, the CUVA treatment led to p53-independent apoptosis, causing almost similar cell death in wild-type, p53 mutant, and p53-silenced tumor cells. Expression of the p53-regulated downstream proteins like p21, and DNA-damage-dependent p53 phosphorylation at serine-15 residue also was not elicited by the CUVA treatment, at a low coralyne concentration. Instead, it led to an immediate activation of the Chk2-mediated S-phase arrest, despite activating PARP protein for DNA repair. The S-phase arrest subsequently ensures apoptosis through activation of caspases-3 and -9, the latter being reflected from the results with a specific caspase-9 inhibitor. Abrogation of Chk2 activity by shRNA or by using ATM-specific inhibitor (ATMi) led to a defective S-phase checkpoint and further augmentation in apoptosis. However, at a high coralyne concentration, the CUVA-induced apoptosis followed multiple and independent pathways, involving several caspases. The CUVA treatment may represent a novel mechanism-based protocol for increasing the efficacy of coralyne in inducing apoptosis in both p53 wild-type and mutant tumor cells.
authors.affiliation: Bio-Organic Division, Bhabha Atomic Research Centre , Mumbai, India.
authors.forename: Birija Sankar
authors.initials: BS
authors.lastname: Patro
authors.forename: Biswanath
authors.initials: B
authors.lastname: Maity
authors.forename: Subrata
authors.initials: S
authors.lastname: Chattopadhyay
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D064007:Ataxia Telangiectasia Mutated Proteins; D001600:Berberine Alkaloids / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D020169:Caspases / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D045744:Cell Line, Tumor / Q000187:drug effects / Q000528:radiation effects; D064447:Checkpoint Kinase 2; D004247:DNA / Q000378:metabolism*; D004249:DNA Damage; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D015394:Molecular Structure; D009369:Neoplasms / Q000378:metabolism* / Q000473:pathology; D017319:Photosensitizing Agents / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D016196:S Phase / Q000502:physiology*; D059004:Topoisomerase I Inhibitors; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D001600:Berberine Alkaloids; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D017319:Photosensitizing Agents; D059004:Topoisomerase I Inhibitors; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; C000666:coralyne; D004247:DNA; D064447:Checkpoint Kinase 2; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C578634:CHEK2 protein, human; D017346:Protein Serine-Threonine Kinases; D020169:Caspases