The level of basal YB-1 phosphorylation at S102 in a panel of breast cancer cells (MDA-MB-231, MCF-7, HBL100 and SKBr3) was compared to the level of YB-1 phosphorylation in normal cells, that is, human skin and lung fibroblasts (HSF1, HSF7 and HFL) as well as normal mammary epithelial cells (MCF-10A) (Figures 1A and 1B). This evidence concerns the gene YBX1 and breast cancer.