BRCA1 and breast cancer: We confirmed that Gata3+/+;Brca1+/+ mammary tumor cells expressed high levels of GATA3 and Brca1+/− (p18−/−;Brca1+/−) or Gata3+/− (p18−/−;Gata3+/−) mammary tumor cells expressed very weak GATA3 (Fig. 3e), as we previously described [31, 32].