ERBB2 and breast cancer: Further examination of BC subtypes showed that GPx2 mRNA was down-regulated in HER2-enriched relative to luminal A and B tumors, as well as in Basal-like (the great majority of triple-negative BC, TNBC) tumors relative to all other subtypes (SI Appendix, Fig. S2B), implying a link between GPx2 loss and pathological progression.