NF-kappaB in photodynamic therapy: discrepancies of a master regulator

Tumor eradication by photodynamic therapy (PDT) results from the onset of distinct killing processes. In addition to the well-known necrotic and apoptotic mechanisms, PDT initiates an inflammatory response that will indirectly contribute to tumor clearance. The NF-kappaB transcription factor is a major regulator of inflammation modulating the expression of cytokines, chemokines, and adhesion molecules in various cell types in response to a large number of stimuli. Besides, NF-kappaB regulates the expression of antiapoptotic genes, cyclooxygenases (COXs) and metalloproteinases (MMPs) as well, thereby favoring tumor cell proliferation and dissemination. In the present review, we aim to summarize the current knowledge on NF-kappaB status following photosensitization of cancer cells and endothelial cells. In order to unravel the NF-kappaB impact in PDT tumorigenicity and recurrences, we will stress the discrepancies of this major transcription factor relative to the signaling cascades underlying its activation and the cellular effects triggered by its translocation into the nucleus and its binding to its target genes.