| Objective:Gastric cancer is one of the most common malignacies in the world. The major therapeutic methods are surgery and chemotheraphy. Most of patients with this disease are diagnosed in advanced stages and lose the chance of surgical treatment. Despite recent progress in chemotherapy, the overall survival of gastric cancer patients in advanced stages is still unsatifactory. It is realized that the failure of treatment can be attributed to multi-drug resistance, while the resistance to apoptosis may be one of the important reasons for drug resistance. Investigation of apoptosis resistance and exploration of targets for overcoming the resistance have increasingly become the hot spots in this research fields. NF-κB pathway has been paid more attention because of its impact on cell growth and apoptosis. Although NF-κB plays an essential beneficial role in immune and inflammation responds, it has been recognized that NF-κB activation is involved in tumor development and drug resistance related to apoptosis abnormalities. Blockade of NF-κB activation by specific inhibitors may be an effective way for the reversal of chemoresistance and cancer therapy. Paeoniflorin has been reported to exhibit anti-inflammatory, growth inhibitory and anticarcinogenic effects. We postulate that the effects of Paeoniflorin may be realized through the modulation of NF-κB activation pathway. In this study, we investigated in vitro the effects of Paeoniflorin on cell growth and apoptosis in human gastric carcinoma cells (SGC-7901), and on NF-κB activation. We also investigated the potential mechanisms of NF-κB inhibition made by Paeoniflorin.Methods:1. Human gastric carcinoma cell line SGC-7901 was grown as monolayers in RPMI1640 medium. MTT assay was used to evaluated cell growth treated with Paeoniflorin and/or with 5-FU. 2. Western Blot was used to test the expression of NF-κB in nuclear,and the the expression of IκBα,p- IκBαand IKKαin cytoplasm. 3. The intranuclear activities of NF-κB was confirmed by ELISA assay. 4. The effect of Paeoniflorin on the nuclear translocation of P65 was examined by immunofluorescence. 5. IκBαmRNA expression in SGC-7901 cells treated with or without Paeoniflorin was detected by RT-PCR. 6. The influence on cell apoptosis of gastric carcinoma cell by Paeoniflorin and/or 5-FU was estimated by flow cytometry.Results:1. Treatment of SGC-7901 cells with Paeoniflorin and 5-FU resulted in a dose-dependent cytotoxicity. The growth inhibitory effect of 5-FU on SGC-7901 cells was significantly enhanced by Paeoniflorin. 100μg/ml of Paeoniflorin caused 17% inhibitory rate. The inhibitory rate of 5-FU was 8%. Combined treatment of Paeoniflorin and 5-FU resulted in 29% inhibitory rate. 2. The inhibition pattern of NF-κB induced by Paeoniflorin exhibited in a time and dose dependent pattern, which was confirmed by Western Blot and ELISA. After incubation for 48h with Paeoniflorin (100μg/ml), the NF-κB expression in nuclear was just half of the control (P < 0.01). Immunofluorescence assay also confirmed the effect. 3. Paeoniflorin treatment led to a decrease of IκBαphosphorylation and an increased expression of IκBα, while the expression of IκBαmRNA did not show any significant alteration. 4. No significant differences of IKKαexpression were detected among different groups. 5. Paeoniflorin had a promotion of 5-FU induced cell apoptosis. The apoptosis rate of SGC-7901 cells was of 7.4% in 5-FU treated group and of 11.9% in Paeoniflorin treated group, and of 25.9% in combined treatment of the two agents as well (P<0.01).Conclusions:Paeoniflorin can inhibit NF-κB activity of SGC -7901 cells and enhanced 5-FU induced growth inhibition and apoptosis of gastric carcinoma cells. The effect of Paeoniflorin can be realized via a decrease in IκBαphosphorylation, which may not be related to IKKα. The up-regulation of IκBαexpression is not controlled at transcription level. These data suggests that Paeoniflorin, as a novel candidate of NF-κB inhibitor, might be of clinical significance in apoptosis-inducing cancer therapy.
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