Proteomic and transcriptomic analysis on SCLC samples has revealed significantly increased levels of DNA damage response (DDR) proteins, including poly-ADP-ribose polymerase (PARP) [77], checkpoint kinase 1 (CHK1), ataxia telangiectasia-mutated (ATM), and ataxia telangiectasia mutated and Rad3-related (ATR) [78]. This evidence concerns the gene CHEK1 and small cell lung carcinoma.