Access Type

Open Access Dissertation

Date of Award

January 2023

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Immunology and Microbiology

First Advisor

Heather M. Gibson

Abstract

The use of monocloncal antibodies (mAbs) directed at tumor-associated antigens (TAA), often termed “targeted immunotherapy” has revolutionized cancer treatment, markedly improving patient outcomes. As a prime example, the mAb trastuzumab targets human epidermal growth factor 2 (HER2). Like many targeted immunotherapies, only a subset of patients with HER2+ cancer exhibit long-term benefit from trastuzumab. In addition to tumor-intrinsic factors, such as HER2 heterogeneity, we hypothesize that host genetics may influence subsequent immune activation after treatment. To model this interaction, we utilized the genetically heterogeneous Diversity Outbred (DO) mouse model in an F1 cross with BALB/c (producing DOCF1 mice). This cohort of distinct mice were orthotopically implanted with the BALB/c-syngeneic TUBO mammary tumor line, which uniformly expresses rat neu (a HER2 ortholog) and treated with anti-neu mAb clone 7.16.4. Like the human population, we observe a divergent response to therapy. Via genetic linkage analysis, we identified loci that correlate to a robust response. We validated our lead locus located in chromosome 10, in vivo with recombinant inbred collaborative cross (CC) strains selected for driver genetics at this locus, again using a BALB/c F1 cross (producing CCxCF1). We have identified CCxCF1 models that uniformly eliminate tumor, and conversely, are consistently refractory to 7.16.4 treatment. To determine the expression patterns of the genes within this locus and evaluate the influence on transcriptomic profile of the TME, we utilized single-cell RNA sequencing (scRNA-seq) of tumors from responder and non-responder models. Key differences in immune infiltrate composition were identified, particularly within macrophage subsets. This is further supported by ex vivo analysis showing macrophage-mediated antibody-dependent cellular phagocytosis (ADCP) capacity correlates to in vivo treatment outcomes in both DOCF1 and CCxCF1 models. Collectively, we show host genetics play a key regulatory role in targeted immunotherapy outcomes, and we identify putative causal genes which may govern macrophage function during ADCP.

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