title: Differentiation of tumor sensitivity to photodynamic therapy and early evaluation of treatment effect by nuclear medicine techniques.
abstract: OBJECTIVE
  Our final goal is to develop an appropriate method using nuclear medicine technique for monitoring the effect and prediction of Photodynamic Therapy (PDT) on tumors. The aim of this study is to evaluate the effect of PDT on tumor cells in vitro using (18)F-FDG and (99m)Tc-MIBI as tracers.
  
  
  METHODS
  Five tumor cell lines (A431, DU145, H1650, LS180, SHIN3) with varied characteristics were irradiated after incubating for 24 h with several doses of Photofrin (PF). Singlet oxygen was monitored by the near-IR emission detection system during irradiation and generated (1)O2 was calculated. PDT effects were rapidly evaluated by nuclear medicine techniques (uptake of (18)F-FDG and (99m)Tc-MIBI) and traditional methods for cell viability (MTT and trypan blue assays) at 3 h after PDT. Intracellular PF concentration was measured by absorption spectrometer and cell protein content was measured by the Lowry method. (18)F-FDG uptake, (99m)Tc-MIBI uptake, singlet oxygen, and intracellular PF concentration were standardized by protein content. Decrease % of (18)F-FDG and (99m)Tc-MIBI, MTT, and trypan blue was normalized to the control group.
  
  
  RESULTS
  Decrease % of (18)F-FDG was exponentially related to decrease % of MTT (R (2) = 0.650, P < 0.01) while decrease % of (99m)Tc-MIBI was linearly related to that of MTT (R (2) = 0.719, P < 0.01). The decrease % of MTT was more sensitive than that of trypan blue. However, neither (1)O2 nor PF uptake was correlated with sensitivity to PDT. In addition, (18)F-FDG uptake before PDT was linearly related to decrease % of MTT (R (2) = 0.800, P < 0.05).
  
  
  CONCLUSIONS
  Our findings in in vitro studies suggest that (99m)Tc-MIBI is better than (18)F-FDG for early evaluation of PDT effect, but (18)F-FDG uptake may be used to predict PDT sensitivity before therapy.
authors.affiliation: Department of Molecular Imaging, Medical Photonics Research Center, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka, 431-3192, Japan.
authors.forename: Jie
authors.initials: J
authors.lastname: Liu
authors.forename: Mikako
authors.initials: M
authors.lastname: Ogawa
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Sakai
authors.forename: Misato
authors.initials: M
authors.lastname: Takashima
authors.forename: Shigetoshi
authors.initials: S
authors.lastname: Okazaki
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Magata
mesh_terms: D001692:Biological Transport; D045744:Cell Line, Tumor; D017323:Dihematoporphyrin Ether / Q000378:metabolism / Q000627:therapeutic use; D019788:Fluorodeoxyglucose F18; D006801:Humans; D009683:Nuclear Medicine; D010778:Photochemotherapy; D017256:Technetium Tc 99m Sestamibi; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D019788:Fluorodeoxyglucose F18; D017323:Dihematoporphyrin Ether; D017256:Technetium Tc 99m Sestamibi