ESR1 and breast cancer: Moreover, calycosin has been demonstrated to induce apoptosis in estrogen receptor-positive (ER+) breast cancer by reducing the level of active Akt and its downstream HOX transcript antisense RNA (HOTAIR), which functions as a long non-coding RNA (lncRNA) and is highly expressed in breast cancer, but it is negatively regulated by the PI3K/Akt pathway in MCF-7 cell lines at the effective concentration of 20–100 μM [172].