We further demonstrate that ATR- and CHK1 inhibitors display a selective toxicity in SCLC cells, as well as allograft and xenograft SCLC tumors, while NSCLC cell lines isolated from Kras-driven murine lung adenocarcinoma and allograft NSCLC tumors remained largely unaffected, when treated with these compounds (Figs 2, 3, 4 and 5). Here, KRAS is linked to small cell lung carcinoma.