title: Photoactivation of hypericin down-regulates glutathione S-transferase activity in nasopharyngeal cancer cells.
abstract: Photodynamic therapy (PDT) is a new modality of treatment for cancer. Hypericin is a photosensitizer, which is known to generate reactive oxygen species upon activation with light. We observed that photoactivated hypericin induces the generation of reactive oxygen intermediates in nasopharyngeal cancer (NPC) cells in vitro. There was also significant reduction of Glutathione S-transferase (GST) activity in HK1 and CNE-2 NPC cells and in tumor tissues from the NPC/HK1 murine tumor model by hypericin-mediated PDT. As antioxidants protect cells against phototoxicity, down-regulation of GST activity would potentiate the efficacy of hypericin-PDT treatment.
authors.affiliation: Department of Anatomy, Faculty of Medicine, National University of Singapore, 4 Medical Drive, MD 10, Singapore, Singapore S117 597.
authors.forename: H Y
authors.initials: HY
authors.lastname: Du
authors.forename: M
authors.initials: M
authors.lastname: Olivo
authors.forename: B K H
authors.initials: BK
authors.lastname: Tan
authors.forename: B H
authors.initials: BH
authors.lastname: Bay
mesh_terms: D000818:Animals; D000873:Anthracenes; D002454:Cell Differentiation; D002455:Cell Division / Q000187:drug effects; D015536:Down-Regulation / Q000187:drug effects; D005982:Glutathione Transferase / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D018613:Microscopy, Confocal; D009303:Nasopharyngeal Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D010569:Perylene / Q000031:analogs & derivatives* / Q000627:therapeutic use*; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D017382:Reactive Oxygen Species / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D000873:Anthracenes; D017319:Photosensitizing Agents; D017382:Reactive Oxygen Species; D010569:Perylene; C004965:hypericin; D005982:Glutathione Transferase