Low SLC7A5 mRNA expression was also positively associated with favorable prognosis in both DFS and OS in ERα-positive breast cancer patients (P = 0.004 and P = 0.004, respectively; Supplementary Fig. S2c,d), but no association was observed in ERα-negative breast cancer patients (Supplementary Fig. S2e,f). This evidence concerns the gene SLC7A5 and breast cancer.