Radiofrequency Hyperthermia Enhances Locally Delivered Oncolytic Immuno-Virotherapy for Pancreatic Adenocarcinoma

Purpose To investigate the effect of radiofrequency hyperthermia (RFH)-enhanced oncolytic immuno-virotherapy on in vitro pancreatic adenocarcinoma cell line and in vivo rat pancreatic cancer model. Materials and Methods Rat pancreatic adenocarcinoma cell line and 24 Lewis rats with orthotopic pancreatic adenocarcinomas underwent treatment with either (1) oncolytic virotherapy (talimogene laherparepvec [T-VEC]) plus RFH at 42 degrees C for 30 min; (2) oncolytic virotherapy-only; (3) RFH-only; or (4) saline (control). MTS assays and flow cytometry were used to analyze tumor cell viability and apoptosis levels 24 h after treatment. In the in vivo studies, bioluminescence optical/x-ray imaging and ultrasound imaging was used to assess tumor viability and size 7 and 14 days after treatment. Histopathologic analysis was performed after hematoxylin and eosin staining, TUNEL, Ki-67, and immunohistochemical staining with CD8 and ANK61. Results Combination therapy (T-VEC + RFH) induced decreased cell viability and increased cell apoptosis compared to T-VEC alone, RFH alone, or control. Optical/x-ray imaging and ultrasound imaging demonstrated decreased tumor bioluminescent signal and tumor volume relative to baseline after combination therapy compared to T-VEC alone, RFH alone, or control. Histopathology demonstrated decreased tumor volume and cell proliferation, increased CD8(+) T cell and NK cell infiltration in tumors treated with the combination therapy compared to other three groups. Conclusion RFH enhances locally delivered oncolytic immuno-virotherapy for pancreatic adenocarcinoma, with decreased cell viability and increased apoptosis observed after combination therapy in vitro, and decreased cell viability and tumor volume and increased immune cell infiltrate observed after combination therapy in vivo.