Professor University of Oklahoma Norman, Oklahoma, United States
Introduction:: Pancreatic cancer is one of the lethal types of cancer due to its ability to metastasize throughout the body. According to the Surveillance, Epidemiology, and End Results Program (SEER), the overall 5-year relative survival rate for pancreatic cancer is 10.8% but once the cancer metastasizes, this survival rate reduces to 3%. Despite recent advances in cancer research, all the current cancer therapies have severe limitations in treating pancreatic cancer. Surgery, chemotherapy, and radiation therapy are the conventional treatments for pancreatic cancer, however, limitation in the control of metastasis remains an obstacle. Additionally, immunotherapy is a promising approach to treat advanced cancers but the immunosuppressive nature of pancreatic cancer limits the efficacy of this therapy. Therefore, there is a need for a treatment modality that can both break the immunosuppressive nature of the tumor and control metastasis. Here, we implanted pancreatic cancer cell line, Panc02-H7, into the pancreas to establish an orthotopic pancreatic tumor model. We investigated the effects of interstitial photothermal therapy (iPTT) through irradiation of a near-infrared laser, which is used to induce immunogenic cell death (ICD), on the tumors. We tested various laser power and duration to determine the optimal parameters of iPTT. This treatment regimen will later be combined with an immunostimulant for a synergistic approach, and this combination therapy presents a novel strategy to treat pancreatic cancer.
Materials and Methods:: C57BL/6 mice were orthotopically injected with metastatic pancreatic tumor cells (Panc02-H7) in the tail of the pancreas. Tumors were treated with interstitial photothermal therapy (iPTT) 9 days after tumor implantation. Tumors were exposed by surgery and irradiated with 1 cm cylindrical active lens with various laser powers (0.5 W, 1.0 W, and 1.25 W) and treatment durations (5 mins, 10 mins, and 15 mins). Tumor core and surface temperatures were observed throughout the treatment duration. Additionally, ICD molecules from tumor homogenates were measured using enzyme-linked immunosorbent assay (ELISA).
Results, Conclusions, and Discussions:: This study investigated the optimal parameters for iPTT by testing various laser powers and treatment durations. After analyzing the tumor temperatures during treatment, ICD molecules from tumor homogenate, and tissue damage caused by laser irradiation, optimal parameter ranges for iPTT were determined. The results showed that the optimal ICD and optimal thermal effects were achieved when the laser power was set in the range of 1.0 W to 1.25 W and the irradiation duration was in the range of 10 mins to 15 mins. This treatment regimen will later be combined with an immunostimulant for a synergistic approach to provide an effective treatment modality for metastatic pancreatic cancers.
