We found that the treatment of Gata3+/− (p18−/−;Gata3+/−) mouse mammary tumor cells with VP16 led to significantly more γH2AX than the treatment of Gata3+/+;Brca1+/+ (MMTV-PyMT) tumor cells (Fig. 3f, h). This evidence concerns the gene BRCA1 and breast cancer.