Synergistic Effect Of Tumor Necrosis Factor-related Apoptosis Inducing Ligand (TRAIL) And Hydroxycamptothecin On Human Lung Cancer A549 Cells

OBJECTIVE: To determine the interaction of Tumor necrosis factor-related apoptosis inducing ligand(TRAIL) and hydroxycamptothecin(HCPT) against A549 cells and investigate if mitochondrial membrane potential or expression of Bcl-2 and Bcl-xL were changed by HCPT.METHODE:Cytotoxicity of A549 cells treated with TRAIL(100ng/mL),HCPT(4ug/ mL,40ug/mL or 400ug/mL) alone and synergistically were examined by MTT assay.Cell apoptosis stained by PI and mitochondrial membrane potential stained by Rhodanmine123 were detected by flow cytometry.The changes of Bcl-2 and Bcl-xL in protein level were quantified by Western blot analysis and immunocytochemistry.RESULTS:The kill rates of A549 cells treated with 100ng/mLTRAIL,4ug/mL,40ug/mL or 400ug/mL HCPT alone were 13.9%,3.0%,23.4% and 76.7% respectively.The inhibitory rates of A549 cells treated with TRAIL(100ng/mL) and 4ug/mL,40ug/mLor 400ug/mL HCPT were 43.6 %,52.5%,83.1 % respectively.100ng/mLTRAIL and 4ug/mL HCPT show synergistic cytotoxin effect in combination treatment.The apoptosis rates of A549 cells treated by TRAIL(100ng/mL) and HCPT (4ug/mL)respectively or simultaneously conformed to cell inhibitory rates detected by MTT assay.The mitochondrial membrane potential were reduced in (32±6.15)%,(12.8±3.0) % ,(50.7 ± 4.7) % of cells when treated by TRAEL(100ng/mL) and HCPT (4ug/mL)respectively or simultaneously.HCPT did not affect the level of Bcl-2 and Bcl-xL protein.CONCLUSION:Either TRAIL or HCPT can induce apoptosis of A549 cells in vitro.The combination use of them kills A549 cells synergistically mainly in the way of apoptosis.HCPT in low dose cut down the mitochondrial membrane potential of A549 cells and caused further decrease when combined with TRAIL.The decrease of membrane potential may play a role when HCPT sensitizes A549 cells to TRAIL-induced apoptosis.HCPT did not affect the level of Bcl-2 and Bcl-xL.There may be some other factors that cause the sensitizement of A549 cells to TRAIL-induced apoptosis by HPCT.