Phototherapy meets immunotherapy: a win-win strategy to fight against cancer

Phototherapy usually includes photodynamic therapy (PDT) and photothermal therapy (PTT) to induce cell death. PDT utilizes the sensitization of the photosensitizers to generate reactive oxygen species by the inter-system crossing while PTT undergoes nonradiative decay to generate heat. Cancer immunotherapy has evolved as a new therapeutic modality to eradicate tumor cells by activating antigen-presenting cells, and thus, inducing innate or adaptive immune responses. Phototherapy is able to stimulate the immune system, usually by inducing immunogenic cell death (ICD). Photoimmunotherapy (PIT) is an oncological treatment that combines the phototherapy of the tumor with immunotherapy treatment. Combining phototherapy with immunotherapy enhances the immunostimulating response and has synergistic effects for metastatic cancer treatment. PIT is able to enhance the antitumor immune response by ICD and prevent tumor metastases and recurrence. In this review article, we would like to summarize the recent advances in the development of phototherapy (such as PDT, PTT, and synergistic PDT/PTT) triggered immunotherapy for cancer treatment. In addition, immunotherapy triggered by phototherapy and other therapeutic modalities will be discussed. PIT may be a win-win strategy to fight against cancer.