AKT1 and breast cancer: Interestingly, although ERβ reduces AKT signaling with subsequent decreased effects on proliferation, survival, and improved tamoxifen sensitivity of BC cells,39 Meligova et al report that ERβ2 (an isoform of ERβ) desensitizes MCF-7 cells to the inhibitory effects of tamoxifen and fulvestrant, serving as a marker of endocrine resistance.40