An impactful study using preclinical models of ERα+ breast cancers showed extreme sensitive to the combination of tamoxifen and the Bcl-2/Bcl-xL inhibitor ABT-737 or the Bcl-2 specific inhibitor ABT-199, suggesting that Bcl-2 drives resistance of ERα+ breast cancers to tamoxifen13. This evidence concerns the gene BCL2L1 and breast cancer.