Radiosensitizing effects of physiologically active phytochemicals

At present, there are no widely used radiosensitizers beneficial for clinical use, because increased dose of the conventional radiosensitizers or chemotherapeutic agents (carboplatin, cisplatin, 5-fluorouracil etc.) result in normal tissue injury and increased side effects. Clinical usefulness of a radiosensitizer depends on increasing the radiation sensitivity preferentially in tumor cells and reducing the side effects. In order to overcome this problem, it is necessary to find chemicals with relatively safe cytotoxicity and examine their use as potential radiosensitizers. A wide variety of dietary phytochemicals have been proposed to have anticancer and/or antioxidant action. Radiosensitizing effect of phytochemicals has been also exposed. Over the last 10 years, several phytochemicals including polyphenols, isothiocyanatos and terpenes have been reported to enhance radiation sensitivity of cancer cells. The cytotoxicity of phytochemicals seems to be relatively low, because phytochemicals are taken from foods in daily diet. In this review, we summarized phytochemicals which enhance radiosensitivity of cancer cells. Some phytochemicals have characteristics as a potential radiosensitizer for clinical use because of its low cytotoxicity and preferential sensitization to cancer cells. (author)