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Livin, an inhibitor of apoptosis protein (IAP), is overexpressed in various cancers and decreases tumor sensitivity to chemotherapy and radiotherapy. However, the effect of Livin on lung adenocarcinoma metastasis and the specific mechanism involved remain unclear. RNAi technology was used to stably silence Livin in A549 cells in the present study. The effect of Livin on tumor growth and invasion was investigated in lung cancer cells in vitro and animal models were established to determine the anti-metastasis ability of Livin silencing in vivo. The results indicated that Livin knock-down suppressed cell proliferation and inhibited cell invasion, accompanied by downregulation of VEGF and MMP-2/-9. Silencing of Livin resulted in the prevention of xenograft tumor formation. Seventy-five immunodeficient male BALB/C nude mice were randomly divided into three groups, the relative ratio of the areas with pulmonary nodules in the experimental group decreased from 46.71±7.27% to 11.07±2.94% compared with the negative control group (P<0.001), indicating the interaction between Livin, VEGF and MMPs. The xenograft tumor model of intravenous injection of tumor cells were successfully established and applied for the analysis of lung cancer tumorigenesis and metastasis in a time-dependent manner for the first time. Based on the reliable and reproducible animal model, our findings indicate that knock-down of Livin inhibits cell growth and invasion through blockade of the VEGF and MMPs pathways in lung cancer cells in vitro, and inhibits tumorigenesis and metastasis of lung cancer in vivo, suggesting that Livin is a promising antitumor target.

The inhibitor of apoptosis protein (IAP) plays an important role in tumorigenesis and may be a potential target for cancer therapy. Livin, which belongs to this family, is highly expressed in various tumors. The previous study demonstrated that silencing Livin gene promoted lung cancer cell apoptosis; however, the effects on tumor growth suppression by targeting this gene in vivo, to thereby determine the efficacy of targeting Livin for patient therapy, have not been determined. This study injected lentivirus-delivered livinshRNA into established xenograft tumors derived from the lung adenocarcinoma cell line SPC-A-1 in BALB/C nude mice, the result showed that LivinshRNA down-regulated Livin expression effectively, induced tumor cell apoptosis, reduced tumor cell proliferation, and suppressed tumor growth dramatically, with a tumor volume inhibitory rate of (58.65±4.82)% and a tumor weight inhibitory rate of (47.44±1.64)%, but with less severe adverse reaction to the mouse. This study further demonstrated that Livin gene silencing induced a G0/G1-phase cell cycle arrest and cyclin D1 downregulation, which is a key regulator of the G0/G1- to S-phase transition. These findings suggest that LivinshRNA local injection may serve as a therapeutic method for patient treatment, and that LivinshRNA may suppress tumor growth by arresting the cell cycle in the G0/G1-phase.

Objective: To explore the in vivo inhibitory effect of Livin gene silencing by RNA interference on xenograft of lung adenocarcinoma SPC-A-1 cells in BALB/C nude mice., Methods: Three different BALB/C nude mice models were established by subcutaneously inoculating differently treated SPC-A-1 cells into 3 nude mice groups: the blank control group was inoculated with blank SPC-A-1 cells, while the negative group was inoculated with cells transfected with lentivirus-delivered negative shRNA, the experimental group was inoculated with cells with lentivirus-delivered Livin shRNA. Then the growth of tumors was observed, and the volume and weight of the tumors were measured at different time points. The curve of tumor growth was then described, and the inhibition rate was calculated. Livin gene expression in the tumor tissues was determined by RT-PCR and Immunohistochemistry. Cell apoptosis of tumor tissues was detected by TUNEL., Results: Slower tumor growth, smaller tumor volume and lighter tumor weight were observed in the experimental group as compared to the blank and negative groups (F = 70.509, P < 0.01; F = 12.821, P < 0.01). The inhibition rate of tumor volume was (59.5 ± 3.4)%, and the inhibition rate of tumor weight was (71.1 ± 5.6)%. Livinα mRNA and Livinβ mRNA expressions in the experimental group were significantly lower than the 2 control groups [(37.2 ± 1.6)% versus (63.3 ± 3.8)%, (66.1 ± 2.6)%; (29.4 ± 1.1)% versus (53.2 ± 3.4)%, (52.3 ± 3.1)% (F(α) = 45.309, P < 0.01; F(β) = 30.076, P < 0.01)]. Livin protein expression level was also significantly lower than the blank and the negative groups [(15.3 ± 2.8)% versus (51.3 ± 2.1)%, (52.5 ± 2.5)%, F = 78.92, P < 0.01]. The apoptosis rate in the experimental group was significantly higher than that in the 2 control groups [(35.4 ± 3.2)% versus (5.4 ± 1.3)%, (8.6 ± 1.5)%, F = 14.509, P < 0.01]., Conclusion: The lentivirus-delivered Livin shRNA was shown to inhibit the proliferation of transplantation tumor of lung carcinoma effectively, and Livin may be a target for gene therapy in lung cancer.

Livin, a novel member of inhibitors of apoptosis protein, is highly expressed in tumor tissues. It is a potential target in tumor therapy. Silencing its gene expression has been found to promote tumor cell apoptosis or increase tumor sensitivity to therapies. This paper studied the effect of livin anti-apoptotic activity and examined its molecular mechanisms. In the study, higher levels of cell apoptosis were measured by FACS in the experiment group with livin expression silenced than that in controls (P < 0.05). After livin gene expression was knocked down, cleaved caspase-3 protein was up-regulated but caspase-3 mRNA expression was almost the same, the phosphorylated JNK1 protein was down-regulated but JNK1 mRNA and total JNK1 protein expression was approximately the same too. The results suggest that livin may exert anti-apoptotic action on SPC-A1 by activating JNK1 signaling pathway and inhibiting caspase-3 activation.