title: Enhancement of photodynamic antitumor effect with pro-oxidant ascorbate.
abstract: OBJECTIVE
  Photodynamic therapy (PDT) is a treatment modality that utilizes photosensitizers activated by light to induce cell death via the formation of singlet oxygen and other free radicals. Although this method has its advantages for tumor treatment, it cannot be well performed for involving so many therapeutic parameters during use. Tumor recurrence is common due to insufficient treatment. Therefore, a supplemental or complemental treatment is necessary for PDT.
  
  
  METHODS
  L-ascorbate, commonly known as vitamin C, is an essential nutrient for humans. It is also a well-established pro-oxidant in the presence of certain transition metal ions. In our experiments, ascorbate was administered to tumor-bearing mice by intraperitoneal injection (i.p.) for 10 days after they were treated with PDT. We hypothesize that this supplement may improve the therapeutic outcome by as a result of the reactions between ascrobate and the metal ions induced by PDT.
  
  
  RESULTS
  The results demonstrate that PDT can cause Fe and Cu ions to be released from their protein complexes. The reactions between the ions and ascorbate resulted in a post-PDT surge in reactive oxygen species (ROS) as demonstrated in vitro with chemiluminescence detection. This ultimately leads to enhanced tumor cell death and, thus, an improved treatment outcome.
  
  
  CONCLUSIONS
  Based on the results that PDT induces metal ion release and ascorbate reacts with the metal ions producing subsequent ROS, an internal related, complementary and strengthened tumor treatment is established by combination of both PDT and ascorbate, as a low-toxicity and effective method.
authors.affiliation: MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China.
authors.forename: Yanchun
authors.initials: Y
authors.lastname: Wei
authors.forename: Jiaxing
authors.initials: J
authors.lastname: Song
authors.forename: Qun
authors.initials: Q
authors.lastname: Chen
authors.forename: Da
authors.initials: D
authors.lastname: Xing
mesh_terms: D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology*; D004195:Disease Models, Animal; D005260:Female; D015674:Mammary Neoplasms, Animal; D051379:Mice; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012680:Sensitivity and Specificity; D014407:Tumor Cells, Cultured
chemical_list: D017319:Photosensitizing Agents; D017382:Reactive Oxygen Species; D001205:Ascorbic Acid