Objective To investigate the effect of targeted silencing Notch1 on proliferation and apoptosis of human non-small cell lung cancer stem cells.Methods Lung cancer A549 cells and SPC-A-1 cells were selected and divided into control group,Nc-shRNA group and Notch1-shRNA group.The Nc-shRNA group was a negative control RNAi lentivirus group,and the Notch1-shRNA group was a Notch1 inhibitory RNAi lentivirus group.The lentiviral-mediated shRNA interference technology was used to target the silencing of Notch1.The silencing effect of Notch1 gene was verified by quantitative real time polymerase chain reaction (qRT-PCR) and Western blotting.Cell proliferation was detected by methyl thiazolyl tetrazolium (MTT) and sarcosphere formation assay.Apoptosis was detected by Annexin V/7-AAD double staining.Western blotting was used to detect the expression of proliferating cell nuclear antigen (PCNA),B-cell lymphoma-2 (Bcl-2) and Notch1 downstream gene Hes-1.Results The results of qRT-PCR showed that the relative expression levels of Notch1 in control group,Nc-shRNA group and Notch1-shRNA group in A549 cells and SPC-A-1 cells were 1.000 ± 0.000,0.937 ± 0.025,0.490 ± 0.036 and 1.000 ± 0.000,1.077 ± 0.070,0.373± 0.038,with statistically significant differences (F =359.707,P ＜0.001;F =210.455,P ＜0.001),further paired comparison,the relative expression of Notch1 in Notch1-shRNA group was significantly lower than that in Nc-shRNA group (all P ＜ 0.05).Western blotting showed that the expressions of Notch1 protein in A549 cells and SPC-A-1 cells were consistent with the mRNA results.MTT assay showed that the 24 h A values of A549 cells in control group,Nc-shRNA group and Notch1-shRNA group were 0.209 ± 0.005,0.219 ± 0.009,0.159 ±0.006,48 h A values were 0.293 ± 0.004,0.302 ± 0.004,0.205 ± 0.005,72 h A values were 0.450 ± 0.003,0.430 ± 0.012,0.348 ± 0.017,with statistically significant differences (F =79.487,P＜0.001;F =508.664,P ＜0.001;F =57.156,P ＜0.001),further paired comparison,the proliferation ability of Notch1-shRNA group was significantly lower than that of Nc-shRNA group at 24,48,72 h (all P ＜ 0.05).The 48 h A values of SPC-A-1 cells in control group,Nc-shRNA group and Notch1-shRNA group were 0.438 ±0.022,0.412 ± 0.015,0.364 ± 0.010,72h A values were 0.540 ± 0.016,0.519 ± 0.009,0.438 ± 0.019,with statistically significant differences (F =15.667,P =0.004;F =37.299,P ＜ 0.001),further paired comparison,the proliferation ability of Notch1-shRNA group was significantly lower than that of Nc-shRNA group at 48 h and 72 h (all P ＜ 0.05).The sphere sizes of control group,Nc-shRNA group and Notch1-shRNA group in A549 cells were (149.667 ± 6.506) μm,(136.667 ± 7.095) μm,(86.676 ± 7.638) μm,with statistically significant difference (F =65.940,P ＜ 0.001).The sphere sizes of the three groups in SPC-A-1 cells were (118.667 ± 6.658) μm,(128.000 ± 7.000) μm,(60.675 ± 4.509) μm,with statistically significant difference (F =105.372,P ＜0.001).Further paired comparison,the sphere size of Notch1shRNA group was significandy smaller than that of Nc-shRNA group in the two kinds of cells (all P ＜ 0.05).The apoptosis rates of control group,Nc-shRNA group and Notch1-shRNA group in A549 cells and SPC-A-1cells were (0.489 ± 0.014)％,(0.633 ± 0.021)％,(1.683 ± 0.221)％ and (1.323 ± 0.194)％,(1.690 ± 0.188) ％,(3.017 ± 0.356) ％,with statistically significant differences (F =77.660,P ＜ 0.001;F=32.200,P =0.001),further paired comparison,the apoptosis rate of Notch1-shRNA group was significantly higher than that of Nc-shRNA group in the two kinds of cells (all P ＜ 0.05).Western blotting showed that the expressions of PCNA,Bcl-2 and Hes-1 in control group,Nc-shRNA group and Notch1-shRNA group in A549 cells were statistically significant (F =155.343,P ＜ 0.001;F =22.576,P =0.002;F =70.108,P＜0.001),and the expressions of PCNA,Bcl-2 and Hes-1 in the three groups in SPC-A-1 cells were statistically significant (F =49.419,P ＜0.001;F =28.090,P =0.001;F =12.040,P =0.007).Further paired comparison,the expressions of PCNA,Bcl-2 and Hes-1 in Notch1-shRNA group were significantly lower than those in Nc-shRNA group in the two kinds of cells,and the differences were statistically significant (all P ＜0.05).Conclusion Targeted silencing of Notch1 can reduce the proliferation activity of lung cancer stem cells and promote apoptosis,which may be related to the down-regulation of its downstream gene Hes-1.

Lung cancer stem cells play an important role in chemoresistance and invasion and metastasis of lung cancer. Increasing evidence sustains that microRNAs(miRNAs)play a major role in regulating tumor angiogenesis,drug resistance and metastasis. Cancer stem cells are considered to be one of the reasons leading to cancer recurrence,metasta-sis and resistance to chemotherapy,therefore better understanding how miRNAs regulate gene expression in lung cancer stem cells will help identify cancer biomarkers and new therapeutic targets,and will help to develop better treatment strate-gies for lung cancer.

Notch signaling pathway is involved in the abnormal differentiation and self-renewal of lung cancer stem cells.The further studies for the roles of Notch signaling pathway in the regulation of lung cancer stem cells are expected to find new targets in the diagnosis and treatment of lung cancer.Inhibitors of the Notch signaling pathway may be effective in the treatment of lung cancer.Lung cancer stem cells are thought to be a major cause of recurrence of lung cancer,therefore,targeted therapy for lung cancer stem cells may be more effective than treatment for the entire tumor.