While EXO1 is a component gene of the PAM50 panel and is characteristically overexpressed in basal-like tumors, elevated expression was also observed in a subset of estrogen receptor (ER)-positive breast cancers, indicating a broader role for EXO1 beyond basal-like tumors (Supplementary Figure S1) (Nielsen et al., 2010). This evidence concerns the gene ESR1 and breast carcinoma.