YBX1 and breast cancer: Furthermore, Bargou et al. [7] reported that nuclear localization of YB-1 was associated with P-glycoprotein expression in human primary breast cancers, other studies have shown a co-expression of YB-1 and P-glycoprotein in osteo- and synovial sarcoma as well as breast, ovarian and prostate cancer [3,5,8-11].