LAUSR

Humanized mouse models can be useful for in vivo preclinical evaluation of mechanisms underlying cancer immunotherapy. Most such models involve systemic engraftment of immunocompromised mice with human lymphoid and hematopoietic cells, often using normal donor peripheral blood mononuclear cells (PBMCs), followed by inoculation with human tumor. The ability to control and modify immune cells within the tumor microenvironment (TME), especially human NK cells, is limited in such models. Here, we report the development of a mouse model designed to control the number of human T cells and NK cells in the TME. 18 mice and pre-validated PBMCs were obtained from Charles River. Six groups of 3 mice each were inoculated with Raji lymphoma cells. Group 1 was inoculated with Raji cells only and received no PBMCs. Raji cells were mixed PBMCs for groups 2-4. Group 5 was systemically engrafted with PBMCs 12 days prior to Raji inoculation and Group 6 was systemically engrafted with PBMCs 10 days after Raji inoculation. All mice developed tumors with similar growth characteristics. Serial fine needle aspirates (FNAs) of the resulting tumors were evaluated by flow cytometry. Results of FNAs are summarized below. Tumors were harvested at the end of experiment, typically 27 days after tumor inoculation, and evaluated by immunohistochemistry. Both T cells and NK cells were evenly distributed within tumors at the time of harvest. We conclude co-injection of tumor and PBMCs results in engraftment of both T cells and NK cells within the TME for up to 27 days, with T cells and NK cells distributed evenly within the tumor. Mixing higher numbers of PBMCs with tumor cells resulted in increased numbers of T cells and NK cells in the TME throughout the experiment. Matrigel did not improve engraftment or persistence of T or NK cells in the TME. We conclude mixing PBMCs with Raji tumor cells prior to tumor inoculation into immunocompromised mice is an effective approach when a humanized model with human T cells and NK cells within the TME is desired. Group Description % T cells in tumor at 17 days % NK cells in tumor at 17 days 1 No PBMCs 0 0 2 PBMCs mixed with Raji at 10:1 ratio 8.6 1.5 3 PBMCs mixed with Raji at 2:1 ratio 20.3 2.7 4 PBMCs and Raji in matrigel 9.2 0.6 5 PBMCs systemically engrafted 12 days before Raji inoculation 23.2 0.1 6 PBMCs systemically engrafted 10 days after Raji inoculation 19.6 0.2 Citation Format: Jyoti Arora, Caitlin D. Lemke-Miltner, George J. Weiner. A novel humanized mouse model for study of T cells and NK cells in the tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4.