In breast cancer, inhibition of p90 RSK, a major kinase involved in YB-1 phosphorylation; see section “Post-Translational Modification in the Control of YB-1 Activity and Localization”) using the small molecule LJI308 eradicated the population of breast CSCs and induced apoptosis in breast cancer cells (Davies et al., 2015). Here, YBX1 is linked to breast cancer.