Perspectives on photodynamic therapy combined with immunotherapy in treatment of colorectal cancer: an overview based on experimental studies

Colorectal cancer (CRC) is one of the major cancers threatening human health, with high mortality, tumor drug resistance and metastasis, considered to be one of the most difficult diseases to treat. Due to its advantages of non-invasive, strongly targeted and limit side effects, Photodynamic therapy (PDT) has become a promising primary treatment for CRC. Remarkably, PDT has been shown to activate T cell-adaptive immune response and induce immunogenic cell death (ICD). Used in combination with other treatment techniques, PDT has considerable promise in the management of colorectal cancer. In particular, the combination of PDT and tumor immunotherapy, the systemic anti-tumor immune response was enhanced more significantly. This strategy is expected to achieve a synergistic anti-tumor effect by inducing tumor cell apoptosis, regulating tumor immune microenvironment and effectively activating anti-tumor immunity during treatment process. This review focuses on the research of PDT combined with immunotherapy to improve the treatment of CRC. In most studies, a positive effect was observed for combination therapy, experimentally indicating new therapeutic opportunities for CRC.