Further supporting the link between IFITM and immune suppression, IFITM1 levels were found to be elevated in myeloid-derived suppressor cells (MDSCs) compared with myeloid counterparts, namely, monocytes and neutrophils, isolated from the mouse mammary tumor virus-polyomavirus middle T antigen (MMTV-PyMT) transgenic model of breast cancer (245). This evidence concerns the gene IFITM1 and breast cancer.