Previous studies have shown that BIG3 is frequently upregulated in ERα-positive breast cancers5, 6 and here we found that the overexpression of BIG3 was significantly correlated with the poorer prognosis of patients with ERα-positive breast cancer based on the RNAseq2 data set from the Cancer Genome Atlas (Supplementary Fig. 5a, Log rank test; P<0.001). This evidence concerns the gene ESR1 and breast cancer.