ESR1 and breast cancer: To test the effects of selinexor in breast cancer, we selected 26 breast cancer cell lines representing different subtypes that included TNBC and estrogen receptor (ER)-positive (ER+) and human epidermal growth factor receptor (HER2) + cell lines, with various genomic alterations including PIK3CA, TP53, and PTEN mutations as described in Additional file 1.