title: Photodynamic-induced apoptosis of human nasopharyngeal carcinoma cells using Hypocrellins.
abstract: It has been reported that novel photosensitizers Hypocrellin A and B, lipid soluble perylquinone derivatives of the genus Hypericum have a strong photodynamic effect on tumors and viruses. The molecular mechanisms of tumor cell death induction by Hypocrellin A and B are poorly understood. In this study, we have examined the photodynamic effects of Hypocrellin A and B compounds in poorly differentiated (CNE2) and moderately differentiated (TW0-1) human nasopharyngeal carcinoma (NPC) cells. Using these cell lines we investigated the role of the apoptotic pathway in photosensitized Hypocrellin A and B-mediated cell death. Tumor cells photoactivated with Hypocrellin A and B showed cell size shrinkage and an increase in the sub-diploid DNA content. A loss of membrane phospholipid asymmetry associated with apoptosis was induced by both tumor cell lines as evidenced by the externalization of phosphatidylserine (PS). A dose-dependent increase in caspases-3 protease activity inhibitable by the tetrapeptide inhibitor DEVD-CHO was also observed in both cell lines. Western blot analysis of poly (ADP-ribose) polymerase, a caspase substrate, showed the classical cleavage pattern (116 to 85 kDa) associated with apoptosis in Hypocrellin A and B-treated cell lysates. In addition, caspase inhibition blocked the externalization of membrane PS, indicating that the loss of membrane phospholipid asymmetry is a downstream event of caspases activation. These results demonstrate that tumor cell death induced by Hypocrellin A and B is mediated by caspase proteases. In conclusion, this study identifies both Hypocrellins (A and B) as potent and promising photosensitizers for the treatment of NPC.
authors.affiliation: Department of Medical Sciences, National Cancer Centre, 11 Hospital Drive, Singapore 169610. dmssma@nccs.com.sg
authors.forename: S M
authors.initials: SM
authors.lastname: Ali
authors.forename: M
authors.initials: M
authors.lastname: Olivo
authors.forename: G Y
authors.initials: GY
authors.lastname: Yuen
authors.forename: S K
authors.initials: SK
authors.lastname: Chee
mesh_terms: D017304:Annexin A5 / Q000737:chemistry; D017209:Apoptosis; D015153:Blotting, Western; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D004273:DNA, Neoplasm / Q000032:analysis; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005434:Flow Cytometry; D006801:Humans; D009303:Nasopharyngeal Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics; D010569:Perylene / Q000031:analogs & derivatives / Q000627:therapeutic use*; D019800:Phenol; D010718:Phosphatidylserines / Q000378:metabolism; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011809:Quinones / Q000627:therapeutic use*; D014407:Tumor Cells, Cultured / Q000187:drug effects* / Q000201:enzymology
chemical_list: D017304:Annexin A5; D061945:Caspase Inhibitors; D004273:DNA, Neoplasm; D004791:Enzyme Inhibitors; D010718:Phosphatidylserines; D017319:Photosensitizing Agents; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011809:Quinones; D019800:Phenol; D010569:Perylene; D011065:Poly(ADP-ribose) Polymerases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; C048388:hypocrellin A; C064522:hypocrellin B