Photodynamic Effect on DNA and Cell Survival of Human Cells Sensitized by Hematoporphyrin

Abstract

The photodynamic effect of hematoporphyrin (HP) on human cells of the line NHIK 3025 has been studied. The frequency of DNA single-strand breaks, as measured by strand separation in alkali, was used to calculate the efficiency of singlet oxygen in inducing single-strand breaks. Also, singlestrand breakage was compared with loss of colony-forming ability. The frequency of single-strand breaks was not affected when H 2 O was substituted by D 2 O, while cell survival was significantly decreased. This difference suggests that DNA single-strand breaks play a minor role in cell inactivation after photodynamic treatment with HP. Comparison with X-ray data shows that at a similar level of survival X-rays are significantly more efficient in single-strand break induction than treatment with HP and light.