Combining STING-based neoantigen-targeted vaccine with checkpoint modulators enhances antitumor immunity in murine pancreatic cancer
Heather L. Kinkead, Alexander Hopkins, Eric Lutz, Annie A. Wu, Mark Yarchoan, Kayla Cruz, Skylar Woolman, Teena Vithayathil, Laura H. Glickman, Chudi O. Ndubaku, Sarah M. McWhirter, Thomas W. Dubensky Jr., Todd D. Armstrong, Elizabeth M. Jaffee, Neeha Zaidi
Heather L. Kinkead, Alexander Hopkins, Eric Lutz, Annie A. Wu, Mark Yarchoan, Kayla Cruz, Skylar Woolman, Teena Vithayathil, Laura H. Glickman, Chudi O. Ndubaku, Sarah M. McWhirter, Thomas W. Dubensky Jr., Todd D. Armstrong, Elizabeth M. Jaffee, Neeha Zaidi
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Research Article Oncology

Combining STING-based neoantigen-targeted vaccine with checkpoint modulators enhances antitumor immunity in murine pancreatic cancer

Abstract

Tumor neoantigens arising from somatic mutations in the cancer genome are less likely to be subject to central immune tolerance and are therefore attractive targets for vaccine immunotherapy. We utilized whole-exome sequencing, RNA sequencing (RNASeq), and an in silico immunogenicity prediction algorithm, NetMHC, to generate a neoantigen-targeted vaccine, PancVAX, which was administered together with the STING adjuvant ADU-V16 to mice bearing pancreatic adenocarcinoma (Panc02) cells. PancVAX activated a neoepitope-specific T cell repertoire within the tumor and caused transient tumor regression. When given in combination with two checkpoint modulators, namely anti–PD-1 and agonist OX40 antibodies, PancVAX resulted in enhanced and more durable tumor regression and a survival benefit. The addition of OX40 to vaccine reduced the coexpression of T cell exhaustion markers, Lag3 and PD-1, and resulted in rejection of tumors upon contralateral rechallenge, suggesting the induction of T cell memory. Together, these data provide the framework for testing personalized neoantigen-based combinatorial vaccine strategies in patients with pancreatic and other nonimmunogenic cancers.

Authors

Heather L. Kinkead, Alexander Hopkins, Eric Lutz, Annie A. Wu, Mark Yarchoan, Kayla Cruz, Skylar Woolman, Teena Vithayathil, Laura H. Glickman, Chudi O. Ndubaku, Sarah M. McWhirter, Thomas W. Dubensky Jr., Todd D. Armstrong, Elizabeth M. Jaffee, Neeha Zaidi

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Figure 5

Tumor-infiltrating T cells in mice treated with PancVAX and checkpoint modulators.

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Tumor-infiltrating T cells in mice treated with PancVAX and checkpoint m...
ELISPOT assays showing IFN-γ–producing CD8+ T cells from tumors isolated from mice receiving triple therapy (PancVAX + anti–PD-1 + OX40). ** indicates too many spots to count (A) or isotype control is shown in (B). Isolated CD8+ T cells were incubated with T2-Db or T2-Kb antigen-presenting cells (APCs) that were pulsed with individual PancVAX peptides (as shown). Tumors from 10 mice per group were pooled; technical replicates are shown. (C) Flow cytometry showing the percentage of CD8+ T cells expressing IFN-γ, IFN-γ with PD-1, or PD-1 alone. (D) Flow cytometry showing the percentage of CD4+ T cells expressing FoxP3, IFN-γ, IFN-γ and PD-1, or PD-1 alone. Each bar represents cells isolated from a single tumor for C and D. Statistics by unpaired Student’s t test. (E) Tumor-infiltrating T cells were harvested and stained for the surface expression of the exhaustion markers Lag3 and PD-1 (flow cytometry) (representative traces from single tumor). (F) Flow cytometry showing the percentage of CD8+ T cells coexpressing PD-1 and Lag3 following treatment of mice with PancVAX, ADU-V16, AddaVax, low-dose OX40 (50 μg), and/or anti–PD-1 (100 μg). Relevant isotype antibodies were used as controls. For E and F, cells were gated by size for T cells and then gated for live CD8+ T cells. Statistics by Student’s t test, corrected for Bonferroni. P < 0.05; n = 3 mice per group (except the triple treatment as the other 2 tumors were cleared); individual mice and mean ± SEM are shown.