Photoimmunotherapy for cancer treatment

Phototherapy, with its effective dose control and light delivery, has become a promising modality for treating malignant and nonmalignant diseases. Photochemical interaction, specifically photodynamic therapy (PDT), and photothermal interaction have been the primary mechanisms for direct cell destruction in the treatment of cancers. Preclinical studies demonstrate that, in addition to direct local cytotoxicity, PDT can also induce systemic immune responses, which may enhance therapeutic effects on primary tumors and on metastases at distant sites. Selective photothermal therapy, using an in situ application of light-absorbing dye, has also proven to be an effective method for local treatment of tumors. When combined with immunotherapy, the effects of phototherapy can be amplified, potentially making the photoimmunotherapy a systemic treatment modality. This phototherapy-immunotherapy combination, particularly in conjunction with immunoadjuvant, has been used in preclinical studies. The efficacy and long-term effects of such a combination are summarized and the recent experimental results are presented. A new immunoadjuvant, glycated chitosan (GC), has been used to enhance photochemical and photothermal therapies. The PDT-GC combination in the treatment of mammary tumors and lung tumors in mice provided significant improvement in the long-term survival of tumor-bearing animals. The use of GC in dye-assisted laser photothermal therapy also provided long-term curative effects and antitumor immune responses in the treatment of metastatic tumors in rats. The immune responses induced by phototherapy and enhanced by immunotherapy could become important mechanism in the control of metastatic tumors.