Journal Article

879 Local delivery of a plant virus immunotherapy with irreversible electroporation elicits dendritic cell activation and CD8 T cell infiltration in an orthotopic PDAC tumor model

Ledezma, Debbie K, Nguyen-Ta, Kim, Newton, Isabel G, Joshi Utsav, Russo, Hana, Sonowal Himangshu, Steinmetz, Nicole F, White, Rebekah R

2025

Overview

BackgroundDespite the positive impact of immunotherapy in improving outcomes in multiple other solid tumors, the five-year survival rate of pancreatic ductal adenocarcinoma (PDAC) remains at approximately 13%.1 PDAC tumors demonstrate high T-cell exclusion which contributes to its limited response to immunotherapies such as immune checkpoint blockade (ICB). For locally advanced PDAC not amenable to surgical resection, irreversible electroporation (IRE) is an ablative treatment option that effectively reduces local tumor burden.2 However, most patients will develop metastatic disease. The plant virus cowpea mosaic virus (CPMV) is a strong immune stimulant capable of inducing systemic antitumor immunity and immune infiltration into tumors upon intratumoral administration.3 To test the hypothesis that potent tumor localized immune stimulation will generate antitumor immunity to control primary tumor growth and subsequent metastasis, we combined IRE with CPMV and assessed its efficacy on survival and tumor infiltrating lymphocytes in a syngeneic, orthotopic PDAC tumor model.MethodsMice were inoculated with KPC46 PDAC cells into the pancreas tail during laparotomy. After three weeks and during a second laparotomy, tumors were treated with IRE, followed by PBS or CPMV intratumoral injection for the IRE and IRE+CPMV groups, respectively. For the sham and CPMV groups, tumors were injected with PBS or CPMV, respectively. Survival was monitored for 30 days. Tumors of similarly treated mice were harvested on days 3 and 10 after treatment to evaluate the efficacy of IRE+CPMV on primary tumor burden. Tumors were evaluated for immune infiltration by immunofluorescence. Lymph nodes were assessed for dendritic cells and T cells by flow cytometry. Data analysis was completed with one-way ANOVA.ResultsWe find that IRE+CPMV significantly increased survival at 30 days to 66.7% compared to sham (0%), CPMV (30%), and IRE (20%) groups (figure 1A). IRE+CPMV elicited higher CD8 T-cell infiltration into primary PDAC tumors compared to all other groups at day 10 after treatment (figure 1B). This was associated with increased dendritic cell activation with IRE+CPMV compared to all other groups (figure 1C). Analysis of day 10 lymph nodes also indicated IRE+CPMV group to elicit higher levels of CD8 effector memory T cells compared to sham (figure 1D).ConclusionsIRE+CPMV improved survival compared to all other groups. IRE+CPMV treatment was associated with enhanced CD8 T-cell infiltration in the tumor, with the analysis on dendritic cells suggesting effective T-cell priming. This indicates that IRE+CPMV is an effective strategy for early induction of immune activation and T-cell priming, which could potentially sensitize PDAC tumors to respond to ICB.AcknowledgementsThis work was supported by NIH/NCI R01 CA224605, NIH/NCI R01 CA274640, and NIH/NCI R01 CA254268, as well as the NIH/NCI T32 CA121938-18 and NIH/NIGMS K12 GM068524.ReferencesCommon Cancer Sites - Cancer Stat Facts. SEER. https://seer.cancer.gov/statfacts/html/common.htmlMartin RCGI, Kwon D, Chalikonda S, Sellers M, Kotz E, Scoggins C, et al. Treatment of 200 locally advanced (stage III) pancreatic adenocarcinoma patients with irreversible electroporation: safety and efficacy. Annals of Surgery. 2015 Sep;262(3):486.Mao C, Beiss V, Ho GW, Fields J, Steinmetz NF, Fiering S. In situ vaccination with cowpea mosaic virus elicits systemic antitumor immunity and potentiates immune checkpoint blockade. J Immunother Cancer. 2022 Dec 2;10(12):e005834.Ethics ApprovalB6/129 F1 hybrid mice were obtained from The Jackson Laboratory. All animal experiments were conducted using protocols approved by the Institutional Animal Care and Use Committee (IACUC) of University of California San Diego.Abstract 879 Figure 1IRE+CPMV treatment elicits antitumor immunity. A) Survival at day 30 (n=9-10). B) CD8 T cells in day 10 tumors (n=4-5). C) CD69 expression in dendritic cells. (n=4-5) D) Percentage of CD8 effector memory T cells. (n=4-5). Bars=average +/- std.dev[Image Omitted. See PDF.]

• Publisher: BMJ Publishing Group LTD
• Subject: Dendritic cells / Immunotherapy / Laparotomy / Lymphatic system / Lymphocytes / Pancreatic cancer / Tumors