Combination Irreversible Electroporation And Immunotherapy For Local And Abscopal Control Of Multifocal Hepatic Tumors

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Presenter: Conor O'Neill MD | University of Louisville School of Medicine Background: Among patients with advanced hepatocellular carcinoma (HCC), outcomes remain poor. Sorafenib, an oral kinase inhibitor, remains the standard therapy but provides only marginal survival gains with a 10.7-month median overall survival. Recently, data have shown that combination ipilimumab, a CTLA-4 inhibitor, and nivolumab, a programmed cell death protein-1 inhibitor, provide objective response rates observed in 31% of patients and a disease control rate approaching 50%. Non-thermal tumor disruptive therapies are also of interest for advanced HCC for their ability to induce cell death without coagulative necrosis. This provides a theoretical advantage by increasing tumor antigen release for immune recognition and response. Irreversible electroporation (IRE) can be utilized around critical structures for non-thermal destruction of tumors. IRE has also been postulated to have an abscopal effect on lesions not in the tumor-ablative field, possibly through heightened immunologic response. We evaluated whether combination nivolumab (+) ipilimumab and IRE would lead to increased tumor necrosis and T cell recruitment to both the treated tumors and tumors outside the local ablative field. Methods: C57L/J mice (Jackson Laboratory, ME) underwent laparotomy and tumor implantation of 1mmˆ3 sections of Hepa1-6 tumors into the right and left lobes of the liver. Tumors were allowed to mature for 2 weeks. Five groups of mice (n=30) were measured: Group 1 mice were controls with no tumor, Group 2 mice had tumor implantation alone, Group 3 received IRE with 2500 Volts at a pulse length of 100us, pulse interval 100ms and 10 pulses to the left lobe tumor, Group 4 received weekly intraperitoneal injections of ipilimumab (3mg/kg) and nivolumab (10 mg/kg) for 4 weeks and Group 5 received IRE and combination immunotherapy for four weeks. After treatment, the liver was harvested for analysis. Co-culture cell-migration studies were performed. Briefly, hepa1-6 cell cultures either alone or following IRE-treatment were plated into 24-well plates in serum-free medium or medium containing ipilimumab and nivolumab. Co-culture insets were placed in each well containing 1X10ˆ5 mouse lymphoma T cells. Cell migration was analyzed by cell counting at six hours. Results: Mouse tumors treated with IRE (Groups 3&5) had extensive necrosis visible on H&E staining (figure 1). Group 4 mice treated with immunotherapy alone demonstrated minimal tumor necrosis or peritumoral infiltrate. There were significant increases in both tumor necrosis and CD-8(+) T-cell infiltrate for tumors outside the electroporated field for mice treated with both immunotherapy and IRE (p<0.05); tumors treated with IRE directly and immunotherapy had significantly greater necrosis and peritumoral CD-8(+) T cell infiltrate than tumors outside the treated field or for tumors in Groups 1-4 (p<0.05). Similarly, cell migration studies confirmed significantly higher T cell recruitment in cultures containing electroporated Hepa1-6 cells and combination immunotherapies. Conclusion: Murine models of hepatocellular carcinoma demonstrate significant increases in peritumoral T cell recruitment and tumoral necrosis of both primary and abscopal tumors when IRE and combination immunotherapy are utilized. Further research is required to develop mechanistic insight prior to clinical trial initiation.