Interestingly, immunofluorescence experiments showed that H2A.J was expressed at much higher levels in breast and prostate cancer cell lines of luminal cell origin [30,31] compared to basal or non-luminal cell origin [30,31,32] (Figure 5A–C), and Western blotting confirmed this result for the breast cancer lines (Figure 5D). This evidence concerns the gene H2AJ and breast cancer.