Abstract 5625: Evaluation of in vivo anti-tumor response of solid tumors in a novel immune cell-humanized NOD-Prkdcem26Cd52Il2rgem26Cd22/NjuCrl mouse model
Authors: ROWE JENNY , Eberle Christoph , Reap Elizabeth , Fiore Ann , Avrutskaya Anya , de Marval Paula Miliani , Mihalek Robert , Festin Stephen 
Published: September 2020

Abstract
Background: Checkpoint blockade inhibitors targeting PD-1 and CTLA-4 pathways are clinically approved therapies for multiple cancer types. The performance of targeted interventions has been effective, but clinical response rates vary. In vivo models of human immunity in human tumor bearing mice (TBM) is an important tool for studying mechanisms of targeted therapies and developing new and effective treatments. The NCG (NOD-Prkdcem26Cd52Il2rgem26Cd22/NjuCrl), a recently developed triple immunodeficient mouse strain, is a stable host for both human immune cells and tumors for the study of immuno-oncology-based therapeutics.
Study Details: We evaluated the anti-tumor effects of immune checkpoint inhibitors (anti-human PD-1, including Pembrolizumab, and CTLA-4) on colon epithelial carcinoma (RKO) and basal lung cell adenocarcinoma (A549) cell lines in a human donor immune cell-humanized NCG/CRL mouse model (HuCD34NCG). In separate studies Charles River humanized NCG (HuCD34NCG) mice were implanted subcutaneously on the flank with either RKO or A549 tumors. Group randomization occurred when the average tumor size reached a volume of ~100mm3 (A549) or 30-60mm3 (RKO). Control mice were treated with isotype control IgG antibodies. RKO TBM were treated with anti-PD-1 antibody alone, while A549 TBM were dosed with anti-PD1-1 and anti-CTLA-4 antibodies independently and in combination therapy.
Results: Human immune cell engraftment levels were confirmed in the peripheral blood, spleen and tumor (hCD45, hCD3, hCD4, hCD8, hCD19, NK, myeloid, macrophages; markers vary based on study) of HuCD34NCG humanized mice. Tumor growth kinetics were monitored throughout the study. Inhibition of RKO and A549 tumor growth upon anti-PD-1 monotherapy was significant. Human T-cell infiltration was observed in A549 and RKO tumors with the majority of live T-cells responsive post infiltration. Human cytokines (IFN-γ, IL-2 and TNF-α) were released by tumor-infiltrating total T-cells (CD3+) and subsets (CD4+ and CD8+), as demonstrated by intracellular cytokine staining following PMA/Ionomycin stimulation. Polyfunctional T-cell responses were detected in all treatment groups at study termination.
Conclusions: The results from these studies demonstrate significant immunomodulatory anti-tumor response to immune checkpoint inhibitors. The newly developed HuCD34NCG humanized mouse model showed robust and sustained engraftment of human immune cell populations and demonstrated infiltration of T-cells into tissues and tumors making this mouse model ideal for immuno-oncology studies.
Citation Format: JENNY ROWE, Christoph Eberle, Elizabeth Reap, Ann Fiore, Anya Avrutskaya, Paula Miliani de Marval, Robert Mihalek, Stephen Festin. Evaluation of in vivo anti-tumor response of solid tumors in a novel immune cell-humanized NOD-Prkdcem26Cd52Il2rgem26Cd22/NjuCrl mouse model [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 5625.