Photodynamic Therapy for Cancer Treatment

Dear Colleagues,

PDT uses a photosensitizer (PS), molecular oxygen, and light to generate reactive oxygen species (ROS) that can trigger tumor cell death. PDT can cause tumor destruction via three mechanisms: direct cell death, tumor vascular damage, and an immune response. Direct cell death occurs through both programmed cell death (apoptosis) and non-programmed cell death (necrosis) pathways. Necrosis is characterized by rapid cell death, leading to the release of cellular components and molecules that promote inflammation, while apoptosis is a genetically encoded, energy-dependent process that can initiate an immune response. PDT can also induce unconventional modes of cell death in cancer cells, including paraptosis, parthanatos, mitotic catastrophe, pyroptosis, necroptosis, and ferroptosis. In addition, a growing body of evidence suggests that PDT can also trigger immunogenic cell death (ICD), which has emerged as a promising strategy for eliminating tumor cells by promoting a T-cell adaptive immune response and inducing durable immunological memory.

PDT can also damage the tumor microvasculature, leading to the interruption of the tumor’s feeding and, consequently, to the death of the tumor cells. This vascular mechanism is achieved by concentrating PS in the vascular system and using a short drug–light interval. The PDT vascular effect can be selectively applied to the tumor and surrounding healthy tissue, with important advantages over PDT protocols that require PS accumulation in the tumor cells.

Finally, PDT can induce an immune response that can contribute to long-term tumor control. PDT has been shown to influence the adaptive immune response through either stimulation or suppression, depending on the treatment protocol. The oxidative damage inflicted by PDT on the tumor stroma triggers an acute inflammatory response initiated by the release of pro-inflammatory mediators. These mediators attract the host’s innate immune cells, which can activate a systemic antitumor immune response. The PDT-induced necrosis of tumors and their vasculature can activate CD8 cytotoxic T lymphocytes that can specifically destroy tumor cells and circulate throughout the body for long periods.

This Special Issue, entitled "Photodynamic Therapy for Cancer Treatment", welcomes original research and review articles in the field, with a focus on, but not limited to, the molecular and mechanistic basis of reactivated cell death in cancer cells, the development of new vectorised photosensitisers, and the technological advances used in this therapy.

Prof. Dr. Bertrand Liagre
Guest Editor

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• cancer
• photodynamic theapy
• photosensitizer
• cell death
• technological advances