title: Assessment of effect of photosensitizers on cytotoxicity of photodynamic therapy in human breast cancer cell cultures.
abstract: BACKGROUND
  Photodynamic therapy (PDT) might be of clinical value for patients with breast cancer with local recurrences or metastasis. However, there is a need for improved photosensitizers that are effective in combination with laser light and have few, if any, side-effects. We evaluated in vitro the effectiveness of a second generation photosensitizer by testing the influence of laser light on cell cultures of a human breast carcinoma cell line, incubated with meta-tetrahydroxyphenylchlorin (m-THPC) (= Temoporfin).
  
  
  METHODS
  Five thousand MCF-7 cells were plated in 96-well plates. Forty-eight hours before laser treatment, the cells were plated to achieve a monolayer configuration. Twenty-four hours after plating, they were incubated with m-THPC. On day 6 after treatment with m-THPC we lysed the cells to extract the intracellular ATP that correlates with the number of living cells. The ATP-CVA was used to assess the cytotoxicity of the tested photosensitizer m-THPC at various concentrations and the relevant laser light alone prior to their combination after six days of culture.
  
  
  RESULTS
  We found a dose-response for m-THPC alone ranging from 2 to 16 micrograms/ml. The calculated inhibition concentration to produce 50% cell kill (IC50) was 4.55 micrograms/ml. We also observed a very low cytotoxicity for laser irradiation alone but a very strong cell kill for the combination of m-THPC together with laser light.
  
  
  CONCLUSIONS
  PDT gave almost total cell kill at m-THPC concentrations that are not toxic in vitro.
authors.affiliation: Department of Obstetrics & Gynecology, University of Zürich, Switzerland.
authors.forename: O R
authors.initials: OR
authors.lastname: Koechli
authors.forename: G N
authors.initials: GN
authors.lastname: Schaer
authors.forename: V
authors.initials: V
authors.lastname: Schenk
authors.forename: U
authors.initials: U
authors.lastname: Haller
authors.forename: H
authors.initials: H
authors.lastname: Walt
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000473:pathology*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008652:Mesoporphyrins / Q000494:pharmacology*; D010778:Photochemotherapy; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; D008652:Mesoporphyrins; D011838:Radiation-Sensitizing Agents; D000255:Adenosine Triphosphate; C072269:temoporfin