Phosphorylated epidermal growth factor receptor (pEGFR) was affected by the nitric oxide level. After the combined treatment, H3255 cells showed a significant reduction in the pEGFR expression (*P = 0.01), which was also observed to a lesser extent in A549 cells (P = 0.1) in comparison to the irradiated group (a,b). Values are expressed as the means ± SEM of three independent sets of data. LNMMA, N
G‐monomethyl‐l‐arginine, monoacetate.