AGR2 and breast cancer: However, human AGR2 has been reported previously to be expressed in the oestrogen receptor alpha (ERα)-positive cell line MCF-7 but not in an ERα-negative cell line (Thompson and Weigel, 1998), and preliminary studies in human breast cancers (Fletcher et al, 2003; Liu et al, 2005) also suggest that AGR2 is correlated with expression of ERα.