A comet assay of DNA damage and repair in K562 cells after photodynamic therapy using haematoporphyrin derivative, methylene blue and meso-tetrahydroxyphenylchlorin.
Single-cell electrophoresis (comet assay) has been used to evaluate DNA damage and repair in the human myeloid leukaemia cell line K562 after low-dose (predominantly sub-lethal) treatments of hyperthermia and photodynamic therapy (PDT). Three different photosensitizers were examined: haematoporphyrin derivative (HpD), methylene blue (MB) and meso-tetrahydroxyphenylchlorin (mTHPC). None of the drugs in the absence of light, nor in light alone, resulted in detectable DNA damage. However, a significant amount of DNA damage was detected immediately after treatment with haematoporphyrin derivative or methylene blue PDT compared with drug-only or light-only treatments; no residual level of DNA damage was evident for either drug following a 4-h post-treatment incubation at 37 degrees C. No significant DNA damage was detected after meso-tetrahydroxyphenylchlorin PDT or hyperthermia either immediately or 4 h after treatment. We conclude that the alkaline comet assay can be applied as an effective screening assay for DNA damage induced by a range of laser therapies.
McNair
F I
FI
Laser Oncology Programme and Cancer Research Campaign Department of Experimental Radiation Oncology, Paterson Institute for Cancer Research, Christie Hospital (NHS) Trust, Manchester, UK.
Marples
B
B
West
C M
CM
Moore
J V
JV
D004249:DNA Damage / Q000187:drug effects*; D004260:DNA Repair; D004587:Electrophoresis, Agar Gel / Q000379:methods; D017324:Hematoporphyrin Derivative / Q000009:adverse effects*; D006801:Humans; D006979:Hyperthermia, Induced; D007951:Leukemia, Myeloid / Q000628:therapy; D008652:Mesoporphyrins / Q000009:adverse effects*; D008751:Methylene Blue / Q000009:adverse effects*; D010778:Photochemotherapy / Q000009:adverse effects; D017319:Photosensitizing Agents / Q000009:adverse effects*; D014407:Tumor Cells, Cultured
D008652:Mesoporphyrins; D017319:Photosensitizing Agents; D017324:Hematoporphyrin Derivative; C072269:temoporfin; D008751:Methylene Blue