Abstract 39: Assessment of a novel method using adult healthy donor mobilized human CD34+hematopoietic stem cells in NCG mice for use in tumor modeling
Authors: Rowe Jenny , Bronson Steven , Eberle Christoph , Fiore Ann , Mihalek Bob , Festin Stephen 
Published: April 2023

Abstract
Checkpoint inhibitors including anti-PD-1/PD-L1 are a type of immunotherapy that have become the standard of care for cancer patients. Continual focus is placed on developing new treatments for cancer, including breast, lung and colon cancer, which are the most common worldwide. Humanized mice are an important in-vivo animal model that recapitulate crucial aspects of human tumor biology and anti-tumoral immunity allowing for assessment of immunotherapies. Currently these models are primarily created using cord blood, which is in limited supply. This leads to the isolation of low numbers of hCD34+ stem cells, resulting in small cohorts of animals. This limitation represents a challenge in working with humanized mice making it important to consider alternative sources of hCD34+ stem cells. In this study, we compared NCG mice engrafted with an alternative source of adult healthy donor mobilized hCD34+ stem cells to those engrafted with cord blood derived hCD34+ stem cells.After evaluating engraftment kinetics between the two cell sources we examined the anti-tumoral effect of an anti-human PD-1 checkpoint inhibitor in mice bearing three different human tumor xenograft cell lines (CDX) (A549 lung, COLO-205 colon and MDA-MB-436 breast cancer). NCG mice were humanized using either cord blood derived or adult healthy donor mobilized hCD34+ stem cells. Levels of human immune cell engraftment were measured in peripheral blood using multi-color flow cytometry. Humanized NCG mice were implanted subcutaneously with cancer cells, and tumor bearing mice (TBM) were randomized into treatment groups when the average tumor size reached comparable volumes for each tumor type. Vehicle control mice were treated with isotype control IgG antibody, whereas TBM were dosed with anti-hPD-1 antibody. Clinical observations, body weights and tumor growth kinetics were recorded throughout the study. At the time of euthanasia whole blood, spleen and tumor tissues were collected and processed for immune profiling by multi-color flow cytometry. Adult healthy donor mobilized hCD34+ humanized mice have sustained humanization levels out to 34 weeks post-injection and can be successfully engrafted with human CDX tumors. The ability to monitor tumor growth kinetics and observe a response to an anti-hPD-1 checkpoint inhibitor across multiple tumor types indicates that NCG mice humanized with adult healthy donor mobilized CD34+ stem cells are useful when assessing immunotherapies. Future directions of this model will expand beyond monotherapies to include the evaluation of additional treatment methods such as bispecific antibodies and cell-directed therapies.
Citation Format: Jenny Rowe, Steven Bronson, Christoph Eberle, Ann Fiore, Bob Mihalek, Stephen Festin. Assessment of a novel method using adult healthy donor mobilized human CD34+hematopoietic stem cells in NCG mice for use in tumor modeling [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 39.