Photodynamic therapy (PDT) is now an approved therapeutic modality for advanced and early cancers, in addition to precancerous lesions. As PDT becomes more of a mainstream treatment option for early cancers, it is important to understand factors that might impede its tumoricidal effect. Our group is interested in studying the molecular responses of cells that have been exposed to both a photosensitizer and light, but not enough to kill them. An understanding of these molecular responses will help in the design of new mechanism-based interventions and potentially improve long-term survival of PDT-treated patients.