MRC1 and cancer: We also found that increased S100a9 protein was colocalized with CK18 and CD206 markers on both mammary epithelial cells and myeloid immune cells in mammary tissues of BRCA1MT xenograft models (Supplementary Fig. 2g–h), suggesting that the S100A9 might be responsible in cancer development through crosstalk between BRCA1-MT cells and surrounding stromal cells in both humans and mice.