Elimination of 4T1 Mammary Tumor Cells by BALB/cBy UBC-GFP Transgenics following Stable Inheritance of the H-2(b) MHC Allele

The human ubiquitin C promoter (UBC)–driven GFP-transgenic mouse (UBC-GFP) transgene integration site was mapped recently to chromosome 17, linked closely to the MHC locus. In this study, we demonstrate a functional consequence of this insertion site in the backcrossed UBC-GFP BALB/c congenic strain [CByJ.B6-Tg(UBC-GFP) 30Scha/J]: rejection of transplanted “syngeneic” 4T1 mammary tumor cells. Rejection of BALB/c-derived 4T1 cells is in all likelihood a consequence of MHC mismatch due to stable inheritance of C57BL/6-derived H-2(b) (rather than prototypical H-2(d)) by the BALB/c UBC-GFP strain. These data are a valuable resource to researchers who have previously employed the UBC-GFP congenic strain for attempted syngeneic MHC-matched and allogenic MHC-mismatched studies, as their data likely require reinterpretation. Further, this study reemphasizes the impact of mapping transgene integration sites of commonly used mouse strains as a way of increasing scientific rigor and reproducibility.