Abstract 5209: Generation of humanized TREM2 mice for preclinical evaluation of therapeutics targeting tumor-associated macrophages

In recent years, immune checkpoint inhibitors (ICIs) have improved treatment for several types of cancer. However, the overall response rates remain low, and drug resistance can occur in patients after initial responses. This resistance is thought to be due in part to tumor-associated macrophages (TAMs), which can deploy a number of mechanisms to suppress anti-tumor immunity, resulting in tumor immune escape. Triggering receptor expressed on myeloid cells-2 (TREM2), a transmembrane receptor that is part of the immunoglobulin superfamily, is highly expressed on the surface of TAMs. Moreover, the expression level of TREM2 is reported to be higher in cancerous tissues vs normal tissues, with higher expression associated with poorer patient outcomes across multiple solid tumor types. Conversely, mice that lack Trem2 experience slower tumor cell expansion and are more responsive to anti-PD-1 immunotherapy, suggesting that TREM2 may be a promising therapeutic target for improving responses to ICI immunotherapies. To better assist the efficacy evaluation of anti TREM2 antibodies, Biocytogen has generated a humanized TREM2 mouse model. In these mice, exons 1-5 and the 3’UTR of mouse Trem2 gene, which encodes the full-length protein, were replaced by its human counterpart. In homozygous mice, human TREM2 protein expression is detected. The distribution of basal leukocyte subpopulations of blood, spleen, and lymph nodes in humanized B-hTREM2 mice were similar and comparable to those in wild-type C57BL/6 mice. Using the MC38 tumor model, we showed modest efficacy of an anti-human TREM2 antibody in inhibiting tumor growth in vivo. In summary, TREM2 humanized mice provide a powerful preclinical model for in vivo evaluation of anti-human TREM2 antibodies for cancer treatment. Citation Format: Ruili Lv, Jia Yu, Zhiyuan Shen, James Jin. Generation of humanized TREM2 mice for preclinical evaluation of therapeutics targeting tumor-associated macrophages. [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 5209.