Figure 2. p21 protein is differentially regulated between cells that are sensitive and resistant in response to ferroptosis. (A–E) Impact of treatment with erastin/IKE on the protein levels of p21 and p53. (A) HT-1080 cells, (B) SK-HEP1 cells and (C) U2OS cells were treated for 16 hours whereas (D) H1299 cells and (E) HCT116 cells (+/+ and -/- isogenic lines with respect to p53 status) were treated for 48 hours.