Local Phototherapy Synergizes with Immunoadjuvant for Treatment of Pancreatic Cancer through Induced Immunogenic Tumor Vaccine.

To develop a synergistic combination therapy for advanced pancreatic cancer, using local phototherapy and immunotherapy, and to determine the efficacy and mechanism of the novel combination therapy using a highly metastatic pancreatic tumor model in mice. Mice bearing Panc02-H7 pancreatic tumors (both subcutaneous and orthotopic) were treated with noninvasive or interventional photothermal therapy, followed by local application of an immunoadjuvant. Tumor growth and animal survival were assessed. Immune cell populations within spleen and tumors were evaluated by FACS and IHC, and cytokine levels were determined by ELISA. Up to 75% of mice bearing subcutaneous tumors treated with combination therapy had complete tumor regression. Local photothermal therapy exposed/released damage-associated molecular patterns, which initiated an immunogenic tumor cell death, resulting in infiltration of antigen-presenting cells and Th1 immunity. Concomitant application of immunoadjuvant amplified Th1 immunity, especially the tumor-specific cytotoxic T lymphocyte response, with increased quantity and quality of T cells. Combination therapy also induced tumor-specific immune memory, as demonstrated by resistance to tumor rechallenge and production of memory T cells. For the treatment of orthotopic tumor, the combination therapy significantly reduced the primary tumors and metastases, and prolonged the animal survival time. This study indicated that combination of local phototherapy and immunotherapy induced a systemic immunity against established tumors and metastases in an aggressive, preclinical pancreatic tumor model, leading to a potential clinical method for patients with advanced pancreatic cancer. .