Objective:Despite platinum-based adjuvant chemotherapy has improved greatly patients’ outcomes,drug resistance poses a major impediment to the successful use of such an effective agent.Metallothioneins(MTs) are known to play putative roles in cancer cell proliferation,apoptosis,differentiation,drug resistance and prognosis. The present studiy was to investigte the role of metallethioein1H(MT1H) in cisplatin resistance of human non-small cell lung cancer(NSCLC) cell lines in vitro or its possible molecular mechanisms. Methods:MT1H mRNA expression in A549 and A549/DDP cells was detected by RT-PCR.A recombinant eukaryotic expression plasmid pcDNA3.1(-)-MT1H was constructed and transfected into A549 cells which express no MT1H.MT1H siRNA was transfected into A549/DDP cells which express MT1H highly.MT1H expression was detected by RT-PCR and Immunoblot.The chemosensitivity to cisplatin was assessed by MTT assay.Apoptosis rate was determined by Tunel and FCM.Bcl-2 and Bax were determined by immunohistochemistry. Results:MT1H mRNA was expressed in A549/DDP but not in A549.After transfection of MT1H,MT1H expression was enhanced and the chemosensitivity to cisplatin was decreased in A549 cells.Inversely,after transfection of MT1H siRNA,MT1H expression was decreased and the chemosensitivity to cisplatin was increased in A549/DDP.The apoptosis rate induced by cisplatin was increased and Bcl-2 was down-regulated but Bax showed little change in A549/DDP cells interferred with MT1H siRNA. Conclusion:MT1H overexpression can promote drug resistance in A549 cells.Down-regulation of MT1H interfered with siRNA can effectively reverses the drug resistance in A549/DDP cells by down-regulating the expression of Bcl-2 and increasing cisplatin induced apoptosis.SiRNA targeting MT1H combined with chemotherapy may be a very promising strategy for treatment of lung cancer. Objective: Despite platinum-based adjuvant chemotherapy has improved greatly patients’ outcomes, drug resistance poses a major impediment to the successful use of such an effective agent. Metallothioneins (MTs) are known to play putative roles in cancer cell proliferation, apoptosis, differentiation, drug resistance and prognosis. The present studiy was to investigate the role of metallethioein1H (MT1H) in cisplatin resistance of human non-small cell lung cancer (NSCLC) cell lines in vitro or its possible molecular mechanisms. Methods: MT1H mRNA expression in A549 and A549 / DDP cells were detected by RT-PCR. A recombinant eukaryotic expression plasmid pcDNA3.1 (-) - MT1H was constructed and transfected into A549 cells which express no MT1H. MT1H siRNA was transfected into A549 / DDP cells which express MT1H highly. MT1H expression was detected by RT-PCR and Immunoblot. The chemosensitivity to cisplatin was measured by MTT assay. Apoptosis rate was determined by Tunel and FCM.Bcl-2 and Bax were determined by immunohistochemistry. Results: MT1H mRNA was expressed in A549 / DDP but not in A549. After transfection of MT1H, MT1H expression was enhanced and the chemosensitivity to cisplatin was decreased in A549 cells. Inversely, after transfection of MT1H siRNA, MT1H expression was decreased and the chemosensitivity to cisplatin was increased in A549 / DDP.The apoptosis rate induced by cisplatin was increased and Bcl-2 was down-regulated but Bax showed little change in A549 / DDP cells interferred with MT1H siRNA. Conclusion: MT1H overexpression can promote drug resistance in A549 cells. Down-regulation of MT1H interfered with siRNA can effectively reverses the drug resistance in A549 / DDP cells by down-regulating the expression of Bcl-2 and increasing cisplatin induced apoptosis. siRNA targeting MT1H combined with chemotherapy may be a very promising strategy for treatment of lung cancer.