Abstract 2920: A Diversity outbred (DO) mouse model reveals regulators of HER2-driven tumorigenesis
Authors: Jacob Jennifer , Wei Kuang , Reyes Joyce D. , Yin Cong-Cong , Rondini Elizabeth , Mi Qing-Sheng , Granneman James , Parajuli Prahlad , Wagner K , Wei Wei-Zen 
Published: July 2021

Abstract
Although humans are heterogeneous, evaluation of tumorigenesis and immunotherapy has relied on the use of inbred mouse strains, which may lead to biased results. In order to investigate the effect(s) of genetic background on tumor incidence and immune response, we have taken a unique new approach to identify genes that are associated with tumor onset time & tumor growth rate using Diversity Outbred (DO) mice. Specifically, we crossed DO female mice (J:DO, Jackson Labs) with BALB/NeuT (NeuT) mice to introduce a heterogeneous background in (BALBxDO) F1 NeuT mice. NeuT express transforming rat neu, the homologue of HER2, and develop spontaneous tumors in all 10 mammary glands between 14 and 19 weeks of age (woa). DO mice are generated by non-sibling crosses of 8 founder strains: A/J, C57BL/6J, 129S1/SvlmJ, NOD/ShiLtJ, NZO/HILtJ, CAST/EiJ, PWK/PhJ, WSB/EiJ to encompass greater than 90% of murine polymorphic alleles. The genetic makeup of each F1 mouse is defined using 143,600 chromosomal markers (mostly SNP) in the Giga Mouse Universal Genotyping Array. SNP analysis identifies the origin of quantitative trait loci (QTL), using the R/QTL package. The program reads the GigaMUGA genotyping results to perform haplotype reconstruction and determine the founder strain haplotype of each marker locus. DO F1 mice have been successfully used to identify the critical role of MHC-IB, and NK cells, in generation of HER2 Ab response following vaccination of HER2 tolerant mice (Wei et al., 2020). In (BALBxDO) F1 NeuT female mice most spontaneous mammary tumors develop over a wider range of time from 9 to 23 woa. QTL analysis of tumor onset time revealed QTLs in chromosomes (Chr) 1 and X with peak LOD scores of 7.7 (p = 0.01) and 8.6 (p &lt; 0.05), respectively. Tumor growth rate was associated with a QTL in Chr 10. More specifically, PWK and CAST haplotypes in these QTLs were associated with early and faster growing tumors. About 10-15 genes in the 3 QTLs contain missense SNP alterations unique to PWK and CAST, and the genes have been associated with human breast cancer prognosis. As an example, Mid2 identified in ChrX QTL interacts with BRCA1, and is negatively associated with patient survival using the TCGA BRCA database. Single cell RNA sequencing revealed that Mid2 is expressed in NeuT mammary tumor tissue. Studies are ongoing to determine the functional significance of candidate genes in HER2/neu mammary tumorigenesis. DO F1 QTL combined with scRNA transcriptomic analysis opens important new opportunities to define critical genes in cancer biology and immunotherapy, with the potential for novel intervention and disease prevention.
Citation Format: Jennifer Jacob, Kuang Wei, Joyce D. Reyes, Cong-Cong Yin, Elizabeth Rondini, Qing-Sheng Mi, James Granneman, Prahlad Parajuli, K Wagner, Wei-Zen Wei. A Diversity outbred (DO) mouse model reveals regulators of HER2-driven tumorigenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2920.