GPX4 and breast cancer: Next, in order to find the most sensitive cancer cells to ferroptosis, we screened five cell lines with different tissue origins (A549 and NCI-H292 are lung cancer cell lines, MCF-7 and MDA-MB 231 are breast cancer cell lines, and DU145 is a prostate cancer cell line), measuring the protein expression levels of the most relevant ferroptotic biomarkers such as GPX4 and ACSL4, together with HO-1 and HO-2 (Figure 1A).