ESR2 and breast cancer: We have assayed ERα (ESR1) and ERβ (ESR2) target genes according to WWOX low and high expression and estradiol treatment in breast cancer cell lines estrogen receptor alpha (ERα)-positive MCF7 which has native high WWOX gene expression in comparison with BT20 ERα-negative and high WWOX and MDA-MB-231 which is ERα-negative with low WWOX expression.