Abstract 6691: Delivering intra-tumoral immune modulators and targeting cancer stem cells using recombinant- AAVs
Authors: Ucar Deniz A. , Monticone Giulia , Hossain Fokhrul , Majumder Samarpan , Wyczechowska Dorota , Dean Matthew J. , Valle Luis Del , Zabaleta Jovanny , Ran Yong , Shanthalingam Sudarvili , Chabot Abraham Bert , Collins-Burow Bridgette M. , Burrow Matthew E. , Osborne Barbara , Golde Todd Eliot , Miele Lucio 
Published: September 2020

Abstract
Solid tumors are composed of heterogeneous cell populations that support rapid growth of cancer cells and suppress immune cell responses. Unleashing the body's own immune response to eradicate cancer cells is one of the most promising ways to treat cancer patients. However, cancer immunotherapy is not without challenges. Some of these include:
1) Phenotypic plasticity and clonal selection in a highly dynamic, heterogeneous and mutable cell population, which leads to de novo and acquired resistance;
2) Immune editing by cancer cells;
3) Expression of immune check point ligands and receptors to suppress immune response locally within the tumor microenvironment, and systemically using exosomes as immune checkpoint carriers;
4) Cross-talk between cancer stem cells and the immune microenvironment;
5) Feasibility of developing personalized treatment strategies, such as cost vs benefit of CAR-T-cell therapy and time constraint, and humanized antibody production;
6) Systemic toxicity of current immunotherapy strategies;
To address these challenges, we propose to use a recombinant adeno-associated virus (rAAV) platform to simultaneously enhance tumor immunity and target cancer stem cells by intra-tumoral administration. We express programmed cell death ligand-1 (PD-L1), and B7-H3 (CD276), in combination with a Notch1 decoy. The latter was chosen because: 1) Notch is a crucial signaling component of cancer stem cells (CSCs) maintenance and resistance and 2) Studies have shown that within the tumor, regulatory T-cells (Treg) are activated by OX40 and Notch ligand Jagged1. Blocking Notch signaling would have dual advantages: blocking Notch signaling in CSCs, and preventing activation of immunosuppressive Tregs.
Based on current clinical trials and our experimental results, we hypothesized that intra-tumoral injection of rAAV viral particles engineered to express soluble PD-1, B7-H3 and Notch1 decoys in combination with lipopolysaccharide (LPS) is a promising strategy. To test our hypothesis, we used two mouse triple negative breast (TNBC) cancer models: C0321 in the FVB background and M-Wnt in the C57/Bl6 background; both are aggressive, highly metastatic, and similar to human TNBC. Using tumor spheroids in vitro, in the presence of soluble decoys of PD-1, B7-H3 and Notch1 synergistically induced the most effective tumor cell killing, compared to single decoy application. Importantly, intra-tumoral injection of PD-1, B7-H3 and Notch1 decoys in combination with LPS induced necrosis of tumors in vivo in our preliminary findings.
Citation Format: Deniz A. Ucar, Giulia Monticone, Fokhrul Hossain, Samarpan Majumder, Dorota Wyczechowska, Matthew J. Dean, Luis Del Valle, Jovanny Zabaleta, Yong Ran, Sudarvili Shanthalingam, Abraham Bert Chabot, Bridgette M. Collins-Burow, Matthew E. Burrow, Barbara Osborne, Todd Eliot Golde, Lucio Miele. Delivering intra-tumoral immune modulators and targeting cancer stem cells using recombinant- AAVs [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6691.