We identified ER+ BC cell lines per Stemke-Hale et al.50 in GDSC and used ANOVA to compare the IC50s of tamoxifen for these cell lines with those of the five CMap-identified drugs for which data were available in GDSC (fulvestrant, rapamycin, tanespimycin, trichostatin A, and vorinostat). This evidence concerns the gene ESR1 and breast cancer.