Identification of Genes Associated with Resistance to Photodynamic Therapy-Mediated Oxidative Stress

Photodynamic therapy (PDT) is an experimental treatment for malignant diseases (1 ,2 ). This procedure involves the systemic administration of a tumor-localizing photosensitizer and subsequent exposure of the malignant lesion to tissue penetrating red light (3 ). Properties of photosensitizer localization in tumor tissue and photochemical generation of reactive oxygen species are combined with precise delivery of laser generated light to produce a procedure offering effective local tumoricidal activity (3 ). Tumors of the bronchus, bladder, esophagus, head and neck, brain and skin are being treated with PDT in clinical trials (4 ). The clinical results are encouraging and PDT recently received FDA approval for the treatment of advanced esophageal carcinoma in the United States. Additional regulatory approval of PDT has been obtained in Canada, the Netherlands, and Japan (5 ).