Fig. 6. p21 protein is induced by IFN- in MCF-7 cells but not in MDA-MB-231 cells. Total protein was collected from MCF-7 and MDA-MB-231 cells treated with and without 10 ng/ml IFN-. Lysates were then separated by SDS-PAGE and immunoblotted with p21 antibody. Total protein from A431 cells treated with EGF was included as a positive control for the induction of p21 protein.