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Photodynamic therapy (PDT) is a treatment for cancer and several noncancerous proliferating cell diseases that depends on the uptake of a photosensitizing compound followed by selective irradiation with visible light. In the presence of oxygen, irradiation leads to the production of reactive oxygen species (ROS). A large production of ROS induces the death of cancer cells by apoptosis or necrosis. A small ROS production can activate various cellular pathways. Here, we show that PDT by pyropheophorbide-a methyl ester (PPME) induces the activation of nuclear factor kappa B (NF-kappaB) in HMEC-1 cells. NF-kappaB is active since it binds to the NF-kappaB sites of both ICAM-1 and vascular cell adhesion molecule-1 (VCAM-1) promoters and induces the transcription of several NF-kappaB target genes such as those of IL-6, ICAM-1, VCAM-1. In contrast, expression of ICAM-1 and VCAM-1 at the protein level was not observed, although we measured an IL-6 secretion. Using specific chemical inhibitors, we showed that the lack of ICAM-1 and VCAM-1 expression is the consequence of their degradation by lysosomal proteases. The proteasome and calpain pathways were not involved. All these observations were consistent with the fact that no adhesion of granulocytes was observed in these conditions.

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-KB 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-KB 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-KB status following photosensitization of cancer cells and endothelial cells. In order to unravel the NF-KB 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. PDTASPECTSIn spite of development of new surgical approaches and new chemotherapeutic drugs, conventional anticancer treatment modalities remain poorly effective in particular cancerous contexts and are often deleterious to the patient comfort due to the numerous associated side effects. Alternative approaches such as photodynamic therapy (PDT) have then been developed over the last decades in order to improve the power and the specificity of tumor targeting.

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