To determine whether leukocyte NRF2 promotes tumor progression in the absence of therapeutic stress, we crossed Keap1flox/flox VavCre mice with the spontaneous MMTV-PyMT breast cancer model, a setting in which endogenous immune pressure restrains lesion outgrowth on the C57BL/6 background.27 This evidence concerns the gene NFE2L2 and breast carcinoma.