Abstract: microscope and by MTT assay, respectively. Annexin ⅤFITC and Propidium iodide(PI) were used to stain A549 cells, and flow cytometry(FCM) was used to determine the apoptosis after the treatment of TRAIL or/and TXT. As well as reverse transcriptionpolymerase chain reaction (RTPCR) was applied to semiquantitatively assay the mRNA expression of death receptors DR4 and DR5 in A549 cells before and after the treatment of subtoxic doses of TXT for different hours. Results: ① The growth inhibition by TXT worked in a dosedependent fashion on A549 cells. The value of IC50 of TXT was 62.1ng/ml. The growth inhibition rate (GIR) was (6.84±1.14)%, and (26.10±4.00)% respectively by TRAIL at the concentration of 100?ng/ml and 1?600?ng/ml and in an acting time of 24 hours, and it was (19.98±4.15)% by TRAIL at 100?ng/ml in the presence of TXT 4?ng/ml. There was significant difference in the growth inhibition rate (GIR) by TRAIL before and after the combination of TXT(P＜0.05); ② The apoptotsis rate detected by FCM was 4.44%, and 12.26% respectively after the 24 hours treatment by TRAIL(100?ng/ml) or TXT(4?ng/ml), whereas it was increased to 16.84% after the 24 hours treatment of TRAIL(100?ng/ml) combined with TXT(4?ng/ml); ③ The expression level of DR4 and DR5 mRNA in A549 cells had no significant change after the treatment by TXT(4?ng/ml) for 4 hours and 8 hours (P>0.05). Conclusions: Human lung adenocarcinoma A549 cells are not sensitive to TRAIL, but are sensitive to docetaxel on TRAILinduced apoptosis. The effect of TXT reversal on TRAIL apoptosis pathway is not supposed to be related to the upregulation of death receptors DR4 and DR5 mRNA in A549 cells.

Key words: Lung neoplasms, Tumor necrosis factor, Apoptosis inducing ligand, TXT, Apoptosis