Finally, to investigate potential clinical correlates of these findings, we first performed immunohistochemical (IHC) staining to quantify p-ATM S1981 expression in matched tumor samples taken from patients with EGFR mutant NSCLC before (treatment naïve, TN) and during (progressive disease, PD) treatment with the EGFR inhibitor erlotinib. The gene discussed is EGFR; the disease is neoplasm.