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Objective To investigate the effect of the SMAC gene on paclitaxel sensitivity and cellular activity in lung adenocarcinoma cells based on the caspase-3/Bcl-2/Bax signaling pathway. Methods A paclitaxel-resistant cell line A549/Taxol was established for lung adenocarcinoma, and the cells were divided into four following groups: pcDNA-NC (transfected with pcDNA-NC blank vector), pcDNA-SMAC (transfected with pcDNA-SMAC vector), siRNA-NC (transfected with siRNA-NC empty virus vector), and siRNA-SMAC groups (transfected with siRNA-SMAC lentiviral vector). The SMAC mRNA expression in cells was detected by qRT-PCR; cell sensitivity was detected by MTT; cell proliferation ability was detected by cloning assay; cell invasion ability was detected by Transwell; apoptosis ability was detected by flow cytometry assay; and caspase-3, Bcl-2 and Bax protein expression in cells were detected by Western blot analysis. Results The SMAC mRNA expression was significantly lower in A549 cells compared with BEAS-2B cells (P < 0.05). The SMAC mRNA expression was significantly higher in the pcDNA-SMAC group than that in the pcDNA-NC group cells (P < 0.05). The SMAC mRNA expression was significantly lower in the cells of the siRNA-SMAC group (P < 0.05) than that in the siRNA-NC group. The SMAC mRNA expression was significantly lower in the cells of the siRNA-SMAC group (P < 0.05) than in the siRNA-NC group. Compared with the pcDNA-NC group, the cell IC50, cell clone number, cell invasion ability, and Bcl-2 protein and Bcl-2/Bax ratio were significantly lower in the pcDNA-SMAC group, the cell resistance index reversal was 2.51-fold, and the apoptosis ability and caspase-3, as well as Bax protein expression, were significantly higher (P < 0.05). Compared with the siRNA-NC group, cell IC50, cell clone number, cell invasion ability, and Bcl-2 protein and Bcl-2/Bax ratio were significantly higher in the siRNA-SMAC group, and apoptosis ability and caspase-3 and Bax protein expression were significantly lower (P < 0.05). Conclusion High expression of SMAC increases paclitaxel sensitivity, inhibits cell growth and invasion, promotes apoptosis in lung adenocarcinoma cells, and has a regulatory effect on the caspase-3/Bcl-2/Bax signaling pathway.
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Objective To construct the pshuttle-Egr-1-hSmac plasmid and transfect human breast cancer MDA-MB-435 cells,and to observe its radiotherapy enhancing effect on tumor cells.Methods The empty vector pshuttle and pshuttle-Egr-1-hSmac plasmid were transfected into MDA-MB-435 cells by liposomal.At different time(4,8,12,24 and 48 h)after irradiation with 2.0 Gy X-ray and 24 h after irradiation with 0.5 -5.0 Gy,the total RNA and protein were collected and extracted from these cells to analyze the Smac mRNA and protein expression levels with RT-PCR and Western blotting methods. The cells were divided into control, pshuttle, pshuttle-Egr-1-hSmac,2.0 Gy irradiation group, pshuttle + 2.0 Gy irradiation and pshuttle-Egr-1-hSmac+2.0 Gy irradiation groups.MTT method was used to evaluate cell proliferation,and the cell survival ability was measured with clone formation assay;Annexin Ⅴ/PI double staining and PI single staining were used to examine the apoptosis and cell cycle of MDA-MB-435 cells. Results There was no Smac mRNA expression in MDA-MB-435 cells in control and pshuttle groups,but the Smac mRNA expression levels in MDA-MB-435 cells in pshuttle-Egr-1-hSmac plasmid group were gradually increased with the time prolongation, and reached the maximum at 24 and 48 h;the Smac mRNA expression levels in MDA-MB-435 cells were increased gradually 24 h after irradiation of 0.5 - 5.0 Gy X-ray with the increasing of irradiation doses, and reached the maximum after 2.0 and 5.0 Gy irradiation. The Smac protein expression levels in pshuttle-Egr-1-hSmac plasmid group were increased gradually with the time prolongation,and reached the maximum at 24 h.The Smac protein expression lervels were increased 24 h afer irradiation of 0,0.5,1.0,2.0 and 5.0 Gy X-ray,especially in 5.0 Gy group. The MTT results showed that the A490 values in 2.0 Gy,pshuttle+2.0 Gy and pshuttle-Egr-1-hSmac groups 24, 48,and 72 h after irradiation were lower than those in control group(P<0.01);the A490 values of MDA-MB-435 cells in pshuttle-Egr-1-hSmac group after 1.0-5.0 Gy X-ray irradiation were lower than those in 0 Gy group (P<0.05 or P<0.01);the survival fraction(SF)in pshuttle-Egr-1-hSmac group was lower than those in control group (P<0.01).The percentages of the cells at G0/G1 and S phase in pshuttle-Egr-1-hSmac group were lower than those in 2.0 Gy group(P<0.01),the percentage of the cells at G2/M phase was higher than that in 2.0 Gy group (P<0.01);the apoptotic rate of the cells in pshuttle-Egr-1-hSmac group was higher than that in 2.0 Gy group (P<0.01).Conclusion X-ray irradiation can significantly increase the Smac mRNA and protein expression levels in MDA-MB-435 cells transfected with pshuttle-Egr-1-hSmac plasmid,inhibit the cell survival rate,and induce G2/M arrest and apoptotic increasing;Smac gene combined with radiotherapy could significantly increase the radiosensitivity of breast cancer cells.
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The effect of Smac gene on the TRAIL-induced apoptosis of the prostate cancer cell line PC-3 and the molecular mechanism were investigated.The Smac gene was transfected into PC-3 cells under the induction of liposome.The intrinsic Smac gene expression was detected by Western blotting.After treatment with TRAIL as an apoptosis inducer,in vitro cell growth activity was assayed by MTT colorimetry.The apoptosis rate of PC-3 cells was determined by annexin V -FITC and propidium iodide staining flow cytometry.The expression of cellular XIAP and caspase-3 genes was examined by Western blotting.Smac-transfected cells (PC-3/Smac group) had significantly increased Smac protein level as compared with PC-3 controls (P＜0.01).After induction with 100-200 ng/mL TRAIL for 12-36 h,cellular proliferation rate in PC-3/Smac group was significantly lower than in PC-3 controls (P＜0.05).After induction with 100 ng/mL TRAIL for 24 h,the apoptosis rate in PC-3/Smac group was significantly enhanced as compared with that of PC-3 controls (P＜0.05).Accordingly,the XIAP expression level was down-regulated significantly (P＜0.05) and caspase-3 subunit P20 was up-regulated significantly (P＜0.05).It is suggested that the over-expression of cellular Smac can inhibit inhibitor of apoptosis proteins (IAPs),enhance caspases activity and the apoptosis rate of PC-3 cells induced by TRAIL,which may provide a useful experimental basis for prostate cancer therapy.
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The enhancing effects of Smac gene on the mitomycin C-induced apoptosis of the bladder cancer cell line T24 were investigated. The Smac gene was transfected into bladder cancer cell line T24 under the induction of liposome. The intrinsic Smac level was detected by using immunohistochemistry and RT-PCR. The in vitro cellular growth activities were assayed by MTT colorimetry.Apoptosis was assayed by the flow cytometry. The results showed that as compared with the control cells, the apoptosis rate of T24 cells induced by mitomycin C was enhanced by transfected Smac gene. Flow cytometry revealed that, the apoptosis rate was 18.84% and 33.52%, and 10.72% and 26.24% respectively in blank and transfected cells treated with 0.05 or 0.005 mg/mL mitomycin C (P＜0.05). It was concluded that Smac could enhance the apoptosis of T24 by mitomycin C,which could provide a useful experimental evidence for bladder cancer therapy.