| Background Hepatocellular carcinoma (HCC) is one of the most common malignancies in China,where the incidence is 30.3/1 00 000, about 5% of the worldwide incidence of type in all human cancers .Over the past twenty years,the mortality was increased by 41.7%in China which constituted 45%of all death number in the world.So far Surgery is the most effective treatment. But more than 80% of hepatocellular carcinoma cases were too late to surgery when diagnosed, and for those patients who were treated with resection,the recurrence rates can be as high as 50%in 2 years. Systemic chemotherapy is an important approach for hepatocellular carcinoma, especially for the non-surgical indications of advanced hepatocellular carcinoma,but currently it is not so effective yet. Apoptosis resistance is one of the characteristics of HCC, and it has played a key role in the incidence of HCC development. Apoptosis resistance of hepatocellular carcinoma is also an important reason for treatment failure. Large number of studies show that COX-2 is highly expressed in hepatocellular carcinoma, COX-2 inhibited apoptosis in HCC be considered an important cause of chemotherapy resistance.Selective cyclooxygenase -2 inhibitor reportedly can inhibit the proliferation and induce apoptosis of cancer cells.However, it is still unclear for the potential molecular mechanism of the COX-2 selective inhibitor effect on proliferation and apoptosis of hepatocarcinoma cell lines.Objective To investigate the effect and elucidate the mechanism of the selective cyclooxygenase-2(COX-2) inhibitor NS-398 on apoptosis and expression of survivin, XIAP and c-IAP1 of hepatocarcinoma cell lines.Methods The effect inhibitive of NS-398 on BEL-7402 and HepG2 cell lines were measured by MTT assay;The morphological change of apoptosis was observed by TUNEL and the apoptosis rate(AP)was deteceted by flow cytometry; Expression levels of COX-2, survivin, XIAP and c-IAP1 were analyzed by immunocytochemical staining, which also used to analyze the relationship between the COX-2 protein and survivin, XIAP and c-IAP1 in hepatocarcinoma cell lines.Results NS-398 significantly inhibited cell proliferation of BEL-7402 and HepG2 in time- and dose-dependent manner(P<0.01).The cells showed distinctive apoptotic characteristics including chromatin condensation and deformed and fragmented nuclei by TUNEL. Flow Cytometry(FCM) assay was performed to analyze apoptotic rate.The sub-G 1 peak, which appeared before the G0/G 1 phase that represents apoptotic cell population,was observed clearly in the BEL-7402 and HepG2 cell lines treated with NS-398. The apoptosis rate of the group which treated with NS-398 was higher than those of the control group. For NS-398 at different concentrations(0, 25, 100 and 200μmol/L),the AP of BEL-7402 were (1.41±0.23)%,(6.69±0.57%),(10.96±1.35)%,(22.83±1.84)%and (32.25±2.41)% respectively. And the AP of HepG2 were (3.3±0.6)%,(5.7±1.8)%,(14.2±1.3)%,(40.1±2.3)%and (64.9±5.8)%(P<0.01)respectively. Compared with control group , the expressions level of COX-2, survivin, XIAP and c-IAP1 were significantly down-regulated in both BEL-7402 and HepG2 cells by NS-398 (P<0.01). The expression level of COX-2 in hepatocarcinoma cell lines was positively correlated with the expression of XIAP, cIAP-1, Survivin(P<0.01).Conclusion NS-398 can inhibit the proliferation and induce the apoptosis in both BEL-7402 and HepG2 Cell Lines.The mechanism may be related with down-regulation of the expression level of survivin , XIAP and c-IAP1.
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