Using a pancreatic cancer mouse model, Narayanan et al. show that irreversible electroporation (IRE) ablated subcutaneous (sc) tumors. In contrast to surgical resection, IRE activated local innate and adaptive immunity and sustained systemic adaptive immunity, evidenced by resistance to sc tumor re-challenge. CD8+ T cells specific for tumor polymorphic alloantigens generated in IRE-responder mice transferred antitumor protection to immune-deficient tumor-naive mice. Unlike IRE alone, IRE plus intratumoral TLR-7 agonist and systemic anti-PD-1 treatment prevented growth of both primary and smaller distal sc tumors.


Contributed by Paula Hochman

Irreversible electroporation (IRE) is a non-thermal ablation technique that is used clinically in selected patients with locally advanced pancreatic cancer, but most patients develop recurrent distant metastatic disease. We hypothesize that IRE can induce an in situ vaccination effect by releasing tumor neoantigens in an inflammatory context. Using an immunocompetent mouse model, we demonstrated that IRE alone produced complete regression of subcutaneous tumors in approximately 20%-30% of mice. IRE was not effective in immunodeficient mice. Mice with complete response to IRE demonstrated prophylactic immunity and remained tumor-free when rechallenged with secondary tumors on the contralateral flank. CD8+ T-cells from IRE-responsive mice were reactive against peptides representing model inherent alloantigens and conferred protection against tumor challenge when adoptively transferred into immunocompromised, tumor-naive mice. Combining IRE with intratumoral toll-like receptor-7 (TLR7) agonist (1V270) and systemic anti-programmed death-1 receptor (PD)-1 checkpoint blockade resulted in improved treatment responses. This combination also resulted in elimination of untreated concomitant distant tumors (abscopal effects), an effect not seen with IRE alone. These results suggest that the systemic anti-tumor immune response triggered by IRE can be enhanced by stimulating the innate immune system with a TLR7 agonist and the adaptive immune system with anti-PD-1 checkpoint blockade simultaneously. Combinatorial approaches such as this may help overcome the immunosuppressive pancreatic cancer microenvironment.

Author Info: (1) Moores Cancer Center, University of California - San Diego School of Medicine. (2) Surgery, University of California - San Diego School of Medicine. (3) Moores UCSD Cancer Cent

Author Info: (1) Moores Cancer Center, University of California - San Diego School of Medicine. (2) Surgery, University of California - San Diego School of Medicine. (3) Moores UCSD Cancer Center, University of California, San Diego. (4) Center for Computational Biology and Bioinformatics, University of California - San Diego School of Medicine. (5) Department of General Surgery, Uniformed Services University of the Health Sciences, Naval Medical Center. (6) Univ Cal-San Diego. (7) Medicine, UCSD Moores Cancer Center. (8) Laboratory of Cellular Immunology, La Jolla Institute For Allergy & Immunology. (9) Surgery, University of California - San Diego School of Medicine rewhite@ucsd.edu.