Photodynamic therapy and anti-tumour immunity

Photodynamic therapy (PDT) kills tumour cells by apoptosis and/or necrosis, and is thought to stimulate an anti-tumour immune response. How important is this inflammatory response to the efficacy of PDT? Photodynamic therapy (PDT) uses non-toxic photosensitizers and harmless visible light in combination with oxygen to produce cytotoxic reactive oxygen species that kill malignant cells by apoptosis and/or necrosis, shut down the tumour microvasculature and stimulate the host immune system. In contrast to surgery, radiotherapy and chemotherapy that are mostly immunosuppressive, PDT causes acute inflammation, expression of heat-shock proteins, invasion and infiltration of the tumour by leukocytes, and might increase the presentation of tumour-derived antigens to T cells.