GPX4 and breast cancer: Protein levels of GPX4, SLC7A11, and SLC3A2 in four luminal breast cancer cell lines (MDAMB415, ZR75-1, MCF7, and CAMA1), four basal breast cancer cell lines (MDAMB436, MDAMB231, HCC1937, and HCC1806), and one normal breast epithelial cell line (MCF10A) were concordant with mRNA expression (Supplementary Fig. 1b, c).