Death and Survival Signals in Photodynamic Therapy

Photodynamic therapy (PDT) is an anticancer modality utilizing the generation of singlet oxygen and other reactive oxygen species through visible light irradiation of a photosensitive dye accumulated in the cancerous tissue. Upon exposure of cancer cells to the photodynamic stress, multiple signaling cascades are concomitantly activated and depending on the subcellular location of the generated ROS and the intensity of the oxidative damage, they dictate whether cells will cope with the stress and survive or succumb and die. Different methodologies have been developed to allow the discrimination of cell death subroutines at the morphological, ultrastructural, and biochemical levels and to scrutinize signaling cascades in response to PDT. Here we describe a selection of useful techniques to characterize apoptosis and autophagy and to monitor the activation status of the MAPK- and Akt-mTOR pathways after PDT.