A Transgenic mouse tolerant to syngeneic cancer cells expressing truncated human epidermal growth factor receptor

Abstract

Epidermal Growth Factor Receptor (EGFR) is often present on the cell surface of a wide variety human malignancies, including non-small-cell lung cancer (NSCLC), glioblastoma (GBM), pancreatic ductal carcinoma (PDC), and castration-resistant prostate cancer (CRPC). Efforts to optimize immunotherapies targeting EGFR are limited by murine intolerance of human EGFR. To overcome this obstacle, we developed C57BL/6 mice in which a truncated variant of human EGFR (hEGFRt), lacking the ligand binding domain and cytoplasmic domain, is expressed from the CAG regulatory elements comprised of the CMV enhancer, β-actin promoter, and β-globin poly-adenylation signals. Cetuximab, a high-affinity, clinically available anti-human EGFR antibody, retains affinity for hEGFRt. The hEGFRt cDNA in the CAG-hEGFRt transgene is flanked by loxP sites to enable its excision thereby reducing interaction of hEGFRt-directed immunotherapies with normal tissues. The CAG-hEGFRt(f/f) transgene is abundantly expressed in hematopoietic lymphoid and myeloid cells, with low-level expression evident also in non-hematopoietic liver, lung, kidney, and brain. Mx1-Cre-mediated transgene excision in adult mice reduces hEGFRt ~ 5-fold in blood mononuclear cells. CAG-hEGFRt(f/f) adult mice are tolerant of syngeneic NSCLC, GBM, prostate, and PDC lines expressing hEGFRt. These mice retain hEGFRt tolerance after transgene deletion. CAG-hEGFRt(f/f) mice provide a new and important tool for the development of immunotherapies targeting hEGFR.