This study was undertaken to examine the effects of Radachlorin as a sensitizer in both photodynamic and radiation therapy on MCF-7 human breast cancer cell line. Another purpose was to assess the effectiveness of radiotherapy in combination with photodynamic therapy. The cells were incubated with Radachlorin and then exposed, in the independent treatment groups, to red visible light (660 nm), at two energy densities (6 and 12 j/cm(^)2) and 2-Gy X-ray ionizing radiation. In addition, combination effects of these modalities were evaluated. The percentage of the cell survival was investigated using the MTT assay and also survival fraction was evaluated by colony assay. The results demonstrated Radachlorin had no significant cytotoxic effects alone. However, it had a strong cytotoxic effect in the presence of light on MCF-7 cells. Light and Radachlorin reduced the percent of cell survival to 47 %. Despite Radachlorin could not act as a radiosensitizer, using integration of Radachlorin with radiotherapy and photodynamic therapy resulted in a significant cell death in comparison to the control group. Colony assay revealed the synergistic effect of this combined therapy with reduction of survival fraction to 0.03. MTT showed that the viability of breast cancer cells was reduced to 28 % by this integration therapy. Combination of radiation and photodynamic therapy could be a worthwhile approach for breast cancer treatment. It appears that we can reduce the adverse effects of treatments without reducing the efficacy of therapy.
Keywords: Breast cancer; Ionizing radiation; PDT.