We determined the expression levels of a series of proteins, including cleaved poly (ADP-ribose) polymerase (PARP), cleaved caspase 3, ataxia-telangiectasia mutated (ATM), gamma H2A histone family member X (γ-H2A.X), CDK1 and programmed cell death 1 ligand 1 (PDL1), in A549 lung cancer cells via western blotting [20, 21] (Fig. 2g, h). Here, ATM is linked to lung cancer.