DPP4 and hepatocellular carcinoma: Using our method, we demonstrate that iodixanol density gradient‐based can greatly enrich for DXR‐induced senescent HepG2 and Huh‐7 HCC cells, characterized by their SA‐β‐galactosidase activity, senescence marker expression (p16, p21, p53, DPP4), proliferation arrest and DNA damage‐dependent γH2A.X foci formation.