STUDY ON SYNERGISTIC CYTOTOXIC EFFECTS AND MECHANISM OF SELECTIVE CYCLOOXYGENASE-2 INHIBITOR AND CISPLATIN AGAINST HUMAN LUNG CANCER CELL LINES

Objective:To study the synergistic cytotoxic effect and the mechanism of Nimesulide(NIM),a selective cyclooxygenase-2 inhibitor combination with conventional chemical agents cisplatin(DDP) against lung cancer A549 cells.Methods:MTT assay was used to determine the influence of nimesulide combination with cisplatin on proliferation and growth of human lung cancer A549 cells.The apoptosis of A549 cells were determined by fluorescent microscopy and flow cytometry.The influence of protein expression PCNA gene of nimesulide combination with cisplatin in A549 cells were assessed by immunocytochemistry(sp) method in order to explicate the mechanism of nimesulide combination with cisplatin on proliferation of A549 cells.Results :(1) After incubation with for 24h,the inhibition rate in nimesulide+cisplatin-treated A549 cells were higher than those cisplatin alone treated cells(P0.01).Assessing the inhibition rates of Nimesulide combination with Cisplatin by Jin zheng-jun method,the result showed that there were a synergetic effect or addictive effect against proliferation of A549 cells.(2)Apoptosis were induced both in cisplatin alone and combination with nimesulide-treated cells,but the apoptosis rate were much higher in the nimesulide combination of cisplatin groups than in cisplatin alone(P﹤0.01).(3) Immunocytochemical staining exhibited that a much lower the positive expression rate and the absorbance value of PCNA in the combination groups than in the cisplatin groups(P0.01).Conclusion:(1)These observations suggest that nimesulide enhanced cisplatin sensitivity and synergetic cytotoxic therapy on A549 cells.Both by enhancing induction of apoptosis and by downregulating PCNA protein expression in A549 cells may likely contribut to the mechanism of synergetic cytotoxic action of nimesulide combination with cisplatin on lung cancer A549 cells.(2)The findings indicated that selective COX-2 inhibitors can be expected as a new chemotherapy adjunctive agent combined with conventional cytotoxic agents,which may play an important role in combined therapeutic anticancer strategies in lung cancer.