ERBB2 and breast cancer: Myeloid-derived suppressor cells (MDSCs; CD45+, CD11b+, Gr1+) are an important immune suppressive population in breast cancer.32,33 The RXR agonist LG268 decreased the percentage of MDSCs in the mammary gland tumors of MMTV-Neu mice (p = 0.0013), from 1.9 ± 0.5% of CD45+ immune cells in the control group to 0.8 ± 0.3% in the LG268-treated group (Fig. 2a, d).