ESR1 and breast cancer: On the other hand, in breast cancer, SULT2B1 expression was reported to be upregulated in both estrogen receptor a (ERa) positive and negative breast cancer tissues, with a higher level in ER-positive tumors (Bieche et al., 2004; Tozlu et al., 2006; Low et al., 2010; Hevir et al., 2011).