The role of LPS-related NF-κB signal pathway in the activation of lung cancer cells (A549). A549 cells were planted in the lower chamber of the transwell and pretreated with NF-κB inhibitor PDTC at 10, 50, 100, 300, 500 μM or vehicle for 4 hrs, and then washed with fresh medium. PDTC pre-treated A549 cells were stimulated with LPS at 500 ng/ml for 24 hrs and PBMCs from healthy donors were then added to the upper chamber of the transwell for co-culture for 48 hrs. A: frequency of CD4+ T cells in total PBMCs, B: frequency of Tregs in CD4+ T cells, and C: frequency of CD45RA+Tregs in CD4+ T cells. *, **, and *** stand for p values less than 0.05, 0.01, and 0.001, as compared with controls pretreated with vehicle, respectively.