Research progress of photothermal-mediated immunotherapy in the prevention of tumor recurrence and metastases

Surgery is one of the most common tumor intervention methods in the clinical field, which results in postsurgical tumor regrowth and destruction of the body’s immune system. As a new method of tumor treatment, phototherapy has high selectivity and space–time accuracy and is minimally invasive. The therapeutic effects of traditional phototherapy are seriously damaged because of its limited permeability, and it can cause serious damage to surrounding healthy tissues. Benefiting from the development of nanotechnology, nanomaterial-based photosensitive materials can specialize in overcoming poor drug penetration depth, unfavorable biodistributions, prolonged blood circulation times, and also efficiently accumulate at tumor areas through enhanced permeability and retention (EPR) effects. Photothermal therapy triggered by near-infrared (NIR) irradiation based on nanomaterials can directly destroy cancer cells, promote the production of tumor-associated antigens (TAAs), and thus trigger anti-tumor immune responses. Therefore, TAAs can explosively release the natural ineffective antigens, and present immune vaccine-like functions in situ. Considering the immunosuppressive tumor microenvironment postsurgery, immunotherapy against cancer cells is a highly complex process. Moreover, phototherapy-induced “abscopal effects” are weak in inhibiting cancer growth, usually resulting in unsatisfactory tumor therapy outcomes. Therefore, phototherapy synergistic immune reagents can promote lymphocyte infiltration and induce the microenvironment of immunogenic tumor, so as to obtain the greatest benefits in anti-tumor treatment. In this article, we will summarize some strategies of nanomaterial-based phototherapy synergistic immunotherapy in inhibiting tumor growth and prevention of cancer cell metastasis and recurrence.