It is consistent with previous findings that NF-kB is capable of promoting G1/S transition while overexpression of IκB-α or inactivation of NF-kB causes a retarded G1/S transition.55 56 Although we found that cell cycle regulation of the pemetrexed-responsive and non-responsive NSCLC subpopulations may be different due to differential NF-kB activities, whether pemetrexed effects differentially to a specific cell stage of NSCLC might warrant further investigation. This evidence concerns the gene NFKBIA and non-small cell lung carcinoma.