Honokiol induces autophagy by inhibiting mTOR signaling pathway in lung cancer A549 cells

AIM:To investigate whether honokiol induces the autophagy of human lung cancer A549 cells and to explore its mechanism. METHODS:The A549 cells were cultured in vitro, and treated with honokiol at different concentrations (0, 10, 20, 40, 60 and 80 μmol/L) for 48 h. MTT assay was performed to analyze the effect of honokiol on the viability of the A549 cells. The formation of autophagosome was observed by staining with acridine orange under fluorescence microscope. The protein levels of autophagy-associated protein LC3, mTOR and p-mTOR in the A549 cells treated with honokiol, or combined with autophagy inhibitor 3-methyladenine (3-MA) were determined by Western blot. RESULTS:Honokiol significantly inhibited the viability of A549 cells in a dose-dependent manner (P<0.05). The number of the intracellular acidic autophageic vacuoles with bright red fluorescence was significantly increased after honokiol treatment. The protein level of LC3-Ⅱ/LC3-I in the A549 cells was significantly enhanced after honokiol (40 μmol/L) treatment, and the ratio of LC3-Ⅱ/LC3-I was significantly decreased by treatment with 3-MA (P<0.05). Furthermore, treatment with honokiol (40 μmol/L) in the A549 cells for 48 h also resulted in significant down-regulation of phosphorylated form of mTOR (P<0.01), while the total protein level was not changed. CONCLUSION:Honokiol significantly inhibits the growth of lung cancer A549 cells and induces the autophagy, which may be correlated with inhibition of mTOR signaling pathway.     

Role of autophagy in inhibition of human lung cancer PC9 cell proliferation by ursolic acid

AIM: To investigate the role of autophagy in inhibition of human lung cancer PC9 cell proliferation by ursolic acid (UA) as well as the underlying mechanism. METHODS: MTT assay and Trypan blue exclusion test were performed to analyze the effect of UA on the proliferation of PC9 cells. The PC9 cells were treated with UA, and autophagy was observed under fluorescence microscope through acridine orange staining. The expression of autophagy-associated proteins LC3 and ATG5 in the PC9 cells were detected by Western blot. The effect of UA, 3-methyladenine (3-MA) 3-MA or their combination on the cell viability was measured by MTT assay. RESULTS: The viability of PC9 cells was significantly inhibited by UA (P<0.05 or P<0.01). The number of bright red fluorescence positive cells was significantly increased after treatment with UA. The protein expression of LC3-Ⅱ and ATG5 was significantly up-regulated compared with control group (P<0.01). Furthermore, combination of UA and 3-MA resulted in a substantial decrease in cell viability compared with using UA alone (P<0.01). CONCLUSION: UA inhibits the proliferation and induces the autophagy of the PC9 cells, in which autophagy plays a protective role. The inhibition of autophagy significantly promotes the death of the PC9 cells induced by UA.     

Regulatory effects of miR-195 on biological behaviors of lung cancer A549 cells

AIM: To investigate the regulatory effects of microRNA (miR)-195 on the biological behaviors, such as viability, apoptosis and migration, of lung cancer A549 cells, and to explore the related mechanisms. METHODS: After miR-195 mimics were transfected into the A549 cells, the cell viability, cell cycle distribution and apoptosis were measured by CCK-8 assay and flow cytometry. Transwell assay was used to detect cell migration ability. Furthermore, the protein levels of cyclin D1, CDK2, Bcl-2 and p-Rb/Rb were determined by Western blot. Dual-luciferase reporter assay was used to screen and identify the possible target genes of miR-195. RESULTS: Over-expression of miR-195 in the A549 cells inhibited the cell viability and induced cell cycle arrest, accompanied with the decrease in the cell migration ability and the increase in the apoptotic rate (P<0.05). Furthermore, the protein levels of cyclin D1, CDK2, Bcl-2 and p-Rb were significantly decreased (P<0.05). Dual-luciferase reporter assay demonstrated that MYB was a potential target gene of miR-195. Over-expression of MYB in the A549 cells partially reversed the effects of miR-195 on the cell viability, apoptosis and migration. CONCLUSION: miR-195 inhibits lung cancer A549 cell growth and migration, and promotes cell apoptosis by targeting MYB gene.     

miR-221 promotes proliferation of lung cancer A549 cells by down-regulating PTEN

AIM: To explore the effect of microRNA-221 (miR-221) on the proliferation of lung cancer A549 cells, and to investigate its mechanism. METHODS: The A549 cells were transfected with miR-221 mimics by Lipofectamine 2000. The expression of miR-221 was detected by RT-qPCR. The expression of PTEN at mRNA and protein le-vels was detected by RT-qPCR and Western blot, respectively. The cell proliferation was examined by CCK-8 assay and colony formation assay. The 3'-UTR of PTEN was cloned into luciferase reporter vector and its enzymatic activity was detected to verify whether miR-221 targeted to PTEN. RESULTS: The expression level of miR-221 in the A549 cells was significantly increased after transfection with miR-221 mimics as compared with negative control group and blank group (P<0.01). The mRNA and protein levels of PTEN were significantly down-regulated compared with control group and blank group (P<0.05). In addition, miR-221 over-expression significantly promoted the proliferation of A549 cells (P<0.05). Moreover, miR-221 inhibited the enzymatic activity of luciferase reporter vector of PTEN. CONCLUSION: Over-expression of miR-221 significantly promotes the proliferation ability of human lung cancer A549 cells by down-regulation of PTEN.     

Effect of di-indolyl thiozoline on proliferation of lung cancer A549 cells

AIM: To investigate the effect of di-indolyl thiozoline (DIIT) on the proliferation of human lung cancer A549 cells. METHODS: The effects of DIIT on the proliferation of human lung cancer A549 cell line were determined by CCK-8 assay and EdU assay. The effects of DIIT on the expression of cyclin-dependent kinase 4 (CDK4), cyclin D1, and the phosphorylation of Akt and mTOR were determined by Western blot. RESULTS: After the A549 cells were treated with DIIT at 12.5, 25, 50 and 100 mg/L, the cell viability detected by CCK-8 assay was decreased by 12%, 27% (P<0.01), 33% (P<0.01) and 52% (P<0.01), respectively, compared with DMSO control group. The EdU positive cell number determined by EdU assay was decreased by 10%, 21% (P<0.05), 26% (P<0.05) and 34% (P<0.01), respectively, compared with DMSO control group. Compared with DMSO control group, DIIT inhibited the phosphorylation of Akt and mTOR and the expression of cyclin CDK4 and cyclin D1 (P<0.05). CONCLUSION: Di-indolyl thiozoline inhibits the proliferation of A549 cells, which may be related to the decreases in phosphorylation levels of Akt and mTOR and the inhibition of cell cycle-related protein expression.     

Baicalein induces autophagy in breast cancer cells

AIM:To investigate the autophagy of breast cancer cells induced by baicalein and to explore its mechanism.METHODS:The effects of baicalein on the viability of MCF-7 cells and 4T1 cells were investigated by MTT assay,and the dosage of the drug was determined.The expression levels of microtubule-associated protein 1 light chain 3-Ⅱ(LC3-Ⅱ) and LC3-I in the MCF-7 cells and 4T1 cells treated with baicalein at doses of 25,50 and 100 μmol/L,or combined with autophagy inhibitor 3-methyladenine (3-MA) were determined by Western blot.In order to confirm the role of baicalein in autophagy,the effect of 3-MA on the apoptosis of both MCF-7 cells and 4T1 cells induced by baicalein was analyzed by flow cytometry.The protein levels of p-mTOR,mTOR,p-AKT and AKT were examined by Western blot and the role of AKT-mTOR pathway in the induction of autophagy in breast cancer induced by baicalein was determined by the combination of activators.RESULTS:Baicalein at 50 μmol/L and above doses significantly inhibited the viability of breast cancer cells in a dose-and time-dependent manner.The expression of LC3-Ⅱ/LC3-I in both MCF-7 cells and 4T1 cells was significantly enhanced after the action of baicalein,and the ratio of LC3-Ⅱ/LC3-I was significantly decreased after 3-MA addition.The results of flow cytometry showed that,compared with baicalein group,the combination of baicalein and 3-MA promoted the levels of necrosis and apoptosis.Moreover,the protein levels of p-mTOR and p-AKT were significantly decreased and were rescued by EGF,while their total protein levels were not changed.CONCLUSION:Baicalein induces autophagy through AKT-mTOR pathway both in MCF-7 cells and 4T1 cells.     

miRNA-126 inhibits proliferation,migration and invasion of human lung cancer A549 cells via EGFR/AKT/mTOR pathway

AIM: To investigate the effects of microRNA(miRNA)-126 on the proliferation, migration and invasion of human lung cancer cell lines, and to explore its mechanism. METHODS: The A549 cells were transfected with miRNA-126 agomir by Lipofectamine 2000. The expression of miRNA-126 was detected by real-time PCR. The cell activity was detected by MTT assay. The number of viable A549 cells was counted by the method of Trypan blue exclusion. The cell colony-forming capability was determined by cell colony formation test. The cell migration and invasion abilities were assayed by wound healing and Transwell methods, respectively. The protein levels of p-EGFR, EGFR, p-AKT, AKT, p-mTOR and mTOR were determined by Western blot. RESULTS: The expression level of miRNA-126 was significantly increased in the A549 cells compared with negative control(NC) group and control group(P<0.01). The proliferation of A549 cells was decreased extremely after transfected with the miRNA-126 agomir(P<0.01), so did the result of the cell colony-formation test. The migration and invasion abilities of the lung cancer cells were also significantly inhibited. The protein levels of p-EGFR, p-AKT and p-mTOR were significantly down-regulated compared with NC group and control group(P<0.01). CONCLUSION: Over-expression of miRNA-126 significantly inhibits the proliferation, migration and invasion ability of human lung cancer A549 cells by down-regulation of EGFR/AKT/mTOR pathway.     

PGRN gene silencing on proliferation and migration abilities of human non-small-cell lung cancer A549 cells

AIM: To investigate the effect of small interfering RNA (siRNA)-mediated progranulin (PGRN) gene silencing on the proliferation and migration abilities of human non-small-cell lung cancer A549 cells and its mechanism. METHODS: The mRNA and protein expression levels of PGRN in the A549 cells and human bronchial epithelial (HBE) cells were detected by qPCR and Western blot. A549 cells were transfected with PGRN-siRNA by liposome method. The expression of PGRN at mRNA and protein levels in the A549 cells transfected with PGRN-siRNA was detected by qPCR and Western blot, respectively. The cell viability was measured by MTT assay. The cell proliferation ability was measured by living cells counting and crystal violet staining assays. The cell migration ability was measured by wound-healing and Transwell assays. The protein levels of proliferating cell nuclear antigen (PCNA), cyclin D1, Bcl-2 and Bax were determined by Western blot. The protein levels of phosphorylated extracellular signal-regulated kinase 1/2 (p-ERK1/2) and phosphorylated protein kinase B (p-Akt) were also determined by Western blot. RESULTS: The expression of PGRN at mRNA and protein levels was higher in the A549 cells than that in the HBE cells (P<0.05). The expression of PGRN at mRNA and protein levels in the A549 cells transfected with PGRN-siRNA was significantly decreased, and the cell proliferation and migration abilities were significantly decreased. The protein expression levels of PCNA, cyclin D1 and Bcl-2 were significantly reduced and the protein expression level of Bax was significantly increased (P<0.05). Meanwhile, the protein levels of p-ERK1/2 and p-Akt were down-regulated (P<0.05). CONCLUSION: PGRN gene silencing obviously inhibits the proliferation and migration abilities of human non-small-cell lung cancer A549 cells. The PI3K/Akt and MAPK/ERK signaling pathways may play an important role in these processes.     

Effect of PDK1 on biological characteristics of lung cancer A549 cells

AIM: To investigate the effects of 3-phosphoinositide-dependent protein-1 (PDK1) on the biological characteristics of non-small-cell lung cancer cell line A549 and the underlying mechanisms.METHODS: The expression levels of PDK1 in lung normal epithelial cell line BEAS-2B and different lung cancer cell lines H460, SPCA1 and A549 were determined by Western blot and real-time PCR. Small interfering RNA was used to down-regulated PDK1 expression in the A549 cells, and then cell viability and apoptosis were measured by CCK-8 assay and flow cytometry, respectively. The expression of cell cycle-and apoptosis-related molecules at protein level and the activation of Akt/FoxO1 pathway were measured by Western blot. Insulin-like growth factor-1 (IGF-1, one of the most potent Akt activators) was used to evaluate the interaction between PDK1 and Akt/FoxO1 pathway.RESULTS: Compared with lung normal epithelial cell line BEAS-2B, PDK1 expression in the lung cancer cell lines was obviously increased (P<0.05). Knockdown of PDK1 suppressed cell viability and cell cycle, but promoted the apoptosis of the A549 cells. The results of Western blot showed that the protein levels of cyclin D1, CDK4, p-Rb, Bcl-2, p-Akt and cytoplasmic p-FoxO1 were significantly decreased after knockdown of PDK1, with increases in the protein levels of P27, cleaved caspase-3 and nuclear FoxO1. Pre-incubation with IGF-1 partly reversed the effect of PDK1 knockdown on Akt/FoxO1 pathway and increased the viability of A549 cells.CONCLUSION: In human non-small-cell lung cancer A549 cells, knockdown of PDK1 suppresses cell viability and promotes cell apoptosis by regulating the expression of cell cycle-and apoptosis-related molecules via Akt/FoxO1 pathway, suggesting that PDK1 may be a potential target for diagnosis and theatment of lung cancer.     

Effect of luteolin on TGF-β1-induced epithelial-mesenchymal transition in lung cancer A549 cells

AIM:To investigate the effects of luteolin on the invasion and epithelial-mesenchymal transition (EMT) induced by transforming growth factor-β1 (TGF-β1) in lung cancer A549 cells. METHODS:The effect of luteolin at 5, 10, 20, 40, 80 and 160 μmol/L on the viability of A549 cells was measured by MTT assay. The invasion ability was analyzed by Transwell method. The morphological changes of the A549 cells were observed under microscope.The protein expression of E-cadherin and vimentin in the A549 cells were determined by Western blot. RESULTS:The viability of the A549 cells was significantly inhibited by luteolin in a dose-time dependent manner (P<0.05). The IC₅₀ of luteolin for the A549 cells (24 h) was 68.79 μmol/L, while that (48 h) was 47.86 μmol/L. TGF-β1 induced morphological alteration of the A549 cells from epithelial to mesenchymal forms. Luteolin significantly inhibited TGF-β1-induced invasion of the A549 cells (P<0.01). The protein expression of E-cadherin was significantly down-regulated and the protein expression of vimentin was significantly up-regulated in the presence of TGF-β1 at 5 μg/L (P<0.01). However, luteolin reversed TGF-β1-induced EMT, up-regulation of E-cadherin and down-regulation of vimentin (P<0.01). CONCLUSION:Lu-teolin reverses TGF-β1-induced EMT in the lung cancer A549 cells.     

Erianin induces apoptosis of human lung cancer A549 cells via ROS/p38 MAPK pathway

AIM:To investigate the effect of erianin on the viability and apoptosis of human lung cancer A549 cells and its possible mechanism. METHODS:A549 cells and BEAS-2B cells were cultured in vitro and treated with erianin at 10, 20, 40, 80 and 160 nmol/L for 48 h. The cell viability was measured by CCK-8 assay. The apoptosis and reactive oxygen species (ROS) were analyzed by flow cytometry. The activity of superoxide dismutase (SOD) was detected by WST-8 method, and the content of malondialdehyde (MDA) was detected by barbituric acid method. The protein levels of nuclear factor E2-related factor 2 (Nrf2), NAD(P)H:quinone oxidoreductase-1 (NQO1), heme oxygenase-1 (HO-1), p38 MAPK, p-p38 MAPK, caspase-3 and cleaved caspase-3 were determined by Western blot.RESULTS:Erianin remarkably reduced the viability of A549 cells in a dose-dependent manner (P<0.05) with IC₅₀ at 52.64 nmol/L. Erianin also induced apoptosis (P<0.05), increased ROS level and MDA content (P<0.05), diminished SOD activity (P<0.05), and down-regulated the protein levels of Nrf2, NQO1 and HO-1 (P<0.05), in a dose-dependent manner. Meanwhile, erianin up-regulated the levels of p-p38 MAPK and cleaved caspase-3 (P<0.05), and these effects were inhibited by N-acetyl-L-cysteine and SB203580 (P<0.05).CONCLUSION:Erianin may induce apoptosis of human lung cancer A549 cells most likely via inhibiting SOD activity and down-regulating the protein levels of Nrf2, NQO1 and HO-1, thus resulting in an increase in ROS and activation of p38 MAPK.     

Effect of rapamycin on proliferation,invasion, adhesion,apoptosis and autophagy of human lung adenocarcinoma A549 and resistant A549/DDP cells treated with cis-diamminedichloroplatinum

AIM: To study the effect of rapamycin (Rap) on the proliferation, invasion, adhesion, apoptosis and autophagy of human adenocarcinoma A549 and resistant A549/DDP cells treated with cis-diamminedichloroplatinum (DDP). METHODS: Human adenocarcinoma A549 and resistant A549/DDP cell lines were cultured. The inhibitory effects of Rap alone or combined with DDP on A549 and resistant A549/DDP cells were detected by MTT assay. The in vitroinvasion abilities of the 2 cell lines treated with Rap alone or combined with DDP were detected by Transwell methods. The in vitroadhesion abilities of the 2 cell lines treated with Rap alone or combined with DDP were detected by adhesion experiments. The apoptosis of A549 and resistant A549/DDP cells induced by Rap alone or combined with DDP was analyzed by flow cytometry. The cell autophagy marker proteins beclin-1 and LC3 in A549 and resistant A549/DDP cells treated with Rap alone or combined with DDP were detected by Western blotting.RESULTS: Compared with Rap or DDP alone group, the combination of Rap and DDP significantly inhibited the proliferation, invasion and adhesion of A549 and resistant A549/DDP cells in vitro, and promoted the cell apoptosis and autophagy marker proteins beclin-1 and LC3 expression (all P＜0.05).CONCLUSION: Rap enhances the effect of DDP through promoting the cell autophagy, thereby inhibiting the proliferation, invasion and adhesion of A549 and resistant A549/DDP cells and inducing the cell apoptosis with a synergistic effect.     

Rip2 induces autophagy and its mechanism in human pancreatic cancer cells

AIM:To explore whether receptor-interacting protein 2 (Rip2) induces autophagy and its under-lying mechanisms in human pancreatic cancer cell line Panc-1. METHODS:The empty plasmid pEGFP-C2 or recombinant plasmid pEGFP-Rip2 was transfected into the Panc-1 cells by jetPRIME reagent. The untreated cells served as control group. The protein levels of Rip2, autophagy-related molecules (beclin-1 and LC3-Ⅱ), and phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) pathway-related proteins were determined by Western blot 48 h after transfection. The morphological changes of the autophagosomes were observed by transmission electron microscopy. RESULTS:The protein level of Rip2 was significantly increased in the Panc-1 cells transfected with pEGFP-Rip2 plasmid. The protein expression of beclin-1 and LC3-Ⅱ in pEGFP-Rip2 group was higher than that in control group and pEGFP-C2 group (all P<0.01). An increased number of autophagosomes was observed under transmission electron microscope in pEGFP-Rip2 group as compared with control group and pEGFP-C2 group. Furthermore, the protein levels of p-mTOR and p-AKT in pEGFP-Rip2 group were lower than those in control group and pEGFP-C2 group (all P<0.01), while no significant difference of the total mTOR and AKT protein levels was found among the 3 groups. CONCLUSION:Rip2 induces autophagy in the Panc-1 cells and its mechanism may be related to inhibiting the activation of PI3K/Akt/mTOR pathway.     

Effect of proline-spirooxindole on viability and apoptosis of non-small-cell lung cancer A549 cells

AIM:To investigate the effect of proline-spirooxindole on the viability and apoptosis of human non-small-cell lung cancer A549 cells. METHODS:The effect of proline-spirooxindole on the viability of A549 cells was determined by CCK-8 assay. The apoptosis was analyzed by flow cytometry. The effects of proline-spirooxindole on the expression of PARP and p53 and the phosphorylation of mTOR were determined by Western blot. RESULTS:After A549 cells were treated with proline-spirooxindole (25, 50 and 100 mg/L), the cell viability was decreased (P<0.01) compared with DMSO control group. The apoptotic rate was increased compared with DMSO control group (P<0.01). The protein expression of p53 was up-regulated, the increased apoptotic protein cleaved PARP was observed, and the phosphorylation of mTOR was inhibited (P<0.01). CONCLUSION:Proline-spirooxindole inhibits the viability of A549 cells and induces apoptosis, which may be related to the phosphorylation of mTOR.     

Effect of antisense RNA targeting Polo-like kinase 1 on cell growth in A549 lung cancer cells

AIM: To investigate the effect of Polo-like kinase-1 (Plk1) depletion on cell cycle progression and cell growth in lung cancer cells.METHODS: A recombinant plasmid containing antisense RNA targeting Plk1 (pcDNA3-Plk1) was transfected into A549 cells by lipofectine. RT-PCR and Western blotting were used to examine Plk1 gene expression. Cell proliferation was evaluated by cell counting and BrdU labeling. Cell cycle distribution and apoptosis were examined by flow cytometry. Inhibition rate (IR) of vinorebline (NVB) was determined by MTT assay. RESULTS: After transfected with pcDNA3-Plk1 into A549 cells, the expression levels of Plk1 mRNA and protein were greatly decreased. Abnormal morphological changes of cells and growth inhibition were observed in pcDNA3-Plk1 transfected cells. The BrdU labeling index was significantly lower than that in control group (P<0.05). Cells showed a strong G₂/M arrest and apoptosis 72 h post transfection. IR of vinorebline in pcDNA3-Plk1 transfected groups was significantly higher than that in other groups. CONCLUSION: Antisense RNA targeting Plk1 is capable of suppressing Plk1 expression, and therefore, significantly inhibits cellular proliferation, induces cell cycle arrest and apoptosis. Moreover, the sensitivity of lung cancer cells to chemotherapy is increased.     

Reversing effect of naringin on cisplatin resistance in human lung cancer A549/DDP cells

AIM: To investigate the effect of naringin (NRG) on cisplatin (DDP) resistance in human lung cancer A549/DDP cells and its possible mechanism. METHODS: A549/DDP cells were cultured in vitro and treated with NRG and/or DDP at different concentrations for 24 h, and then the cell viability were measured by CCK-8 assay. The combination index (CI) of NRG and DDP were analyzed by Chou-Talalay method. The apoptosis rate was analyzed by flow cytometry. Western blot was performed to detect the protein levels of P-glycoprotein (P-gp), multidrug resistance-associated protein 1 (MRP1), p-Akt, CXC chemokine receptor 4 (CXCR4), cleaved caspase-3, Bcl-2 and Bax.RESULTS: The protein levels of P-gp, MRP1, p-Akt and CXCR4 in the A549/DDP cells were higher than those in the A549 cells (P<0.05). The cell viability was remarkably reduced in a dose-dependent manner when A549/DDP cells were exposed to NRG and/or DDP (P<0.05), and the IC₅₀ values of NRG and DDP were 36.92 μmol/L and 129.77 μmol/L, respectively. When the inhibition rate exceeded 15%, NRG in combination with DDP produced a synergistic effect (CI<1). Combination treatment with NRG and DDP significantly induced apoptosis (P<0.05), up-regulated the protein levels of cleaved caspase-3 and Bax, and down-regulated the protein level of Bcl-2 (P<0.05). Meanwhile, NRG remarkably down-regulated the protein levels of P-gp, MRP1, p-Akt and CXCR4 in a dose-dependent manner (P<0.05). CONCLUSION: NRG may enhance the sensibility of A549/DDP cells to DDP most likely via up-regulating the protein level of Bax and down-regulating the protein levels of Bcl-2, P-gp, MRP1, p-Akt and CXCR4.     

Anticancer function of Shp2 in lung adenocarcinoma A549 cells and rela-ted molecular mechanisms

AIM: To explore the anticancer function of Shp2 in lung adenocarcinoma A549 cells and the related molecular mechanisms. METHODS: The viability and proliferation of A549 cells treated with Shp2 specific inhibitor Phps-1 or cisplatin (DDP) were measured by CCK-8 assay and EdU assay. Annexin V-FITC/PI double staining was applied to detect apoptotic rate of A549 cells with different interventions. The protein levels of caspase-3-17p, Bcl-2, Bax, p-STAT3/STAT3 and p-ERK/ERK were determined by Western blot. RESULTS: Compared with control group, Phps-1 at the concentration of 20 μmol/L significantly increased the viability of A549 cells after 24 h of treatment (P<0.05). Meanwhile, the proliferation rate of A549 cells in Phps-1 20 μmol/L group was significant increased compared with control group (P<0.05). The apoptotic rate of A549 cells in DDP treatment group decreased from 13.01%±2.62% to 3.67%±0.93% after adding Phps-1 (P<0.05). Phps-1 down-regulated the protein levels of caspase-3-17p, Bax and p-ERK, but up-regulated p-STAT3.CONCLUSION: Shp2 is a tumor suppressor in A549 cells, which may be associated with the activation of STAT3 signal pathway.     

Effects of miR-337 targeting p53 expression on autophagy and migration ability of colon cancer cells

AIM: To investigate the effect of microRNA-337 (miR-337) on the autophagy and migration ability of colon cancer cells, and to explore its possible mechanism involving targeting p53 expression. METHODS: The me-thod of immunohistochemistry was used to detect the protein expression of beclin-1, LC3B and p53 in colon cancer tissues. The correlations between the protein expression of beclin-1/LC3B and clinicopathological features, and the correlations between the protein expression of p53 and beclin-1/LC3B were analyzed. After knock-down of p53 expression by small interfering RNA, the formation of autophagiosomes was observed under electron microscope in colon cancer cell line HCT116, and the protein expression of beclin-1 and LC3B was determined by Western blot. The miRNAs targeting p53 were predicted and screened by bioinformatics, and their expression in HCT116 cells was verified by RT-qPCR. Luciferase reporter assay was used to detect the regulatory effect of miR-337 on p53 gene. The protein expression of p53, beclin-1 and LC3B was determined by Western blot, and the migration ability of HCT116 cells after miR-337 over-expression was detected by Transwell assay. RESULTS: The protein expression of beclin-1 and LC3B in the colon cancer tissues was decreased, which was significantly related to the occurrence, development, invasion and metastasis of colon cancer. The expression of p53 was increased in the colon cancer tissues, which was negatively correlated with the protein expression of beclin-1 and LC3B. Knock-down of p53 gene expression increased the protein expression of beclin-1 and LC3B (P<0.05). Over-expression of miR-337 down-regulated the expression of p53, up-regulated the protein expression of beclin-1 and LC3B, and decreased the migration ability of HCT116 cells (P<0.05). CONCLUSION: miR-337 promotes autophagy and inhibits migration ability of colon cancer cells, and the mechanism may be related to targeted inhibition of p53 expression.     

27-Hydroxycholesterol modulates lung cancer cell proliferation by activation of LXR signaling pathway

AIM:To investigate the effect of cholesterol metabolite 27-hydroxycholesterol (27-OHC) on the proliferation of lung cancer cells. METHODS:Human lung cancer A549 cells were treated with 27-OHC at different concentrations (0, 0.3125, 0.625, 1.25, 2.5, 5 and 10 μmol/L) for 24~48 h. The cell viability, cell cycle, cell prolife-ration, the intracellular cholesterol levels and cholesterol metabolism-related molecule expression were subsequently assessed by CCK-8 assay, flow cytometry, EdU staining, tissue total cholesterol detection kit, real-time PCR and Western blot. RESULTS:27-OHC decreased the viability of the A549 cells in a dose-and time-dependent manner (P<0.01) and inhibited the cell proliferation (P<0.05). The expression of typical liver X receptor (LXR) downstream target proteins including ATP-binding cassette transporter A1 (ABCA1), low-density lipoprotein receptor (LDLR), and 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CR) were modulated, which promoted the efflux of intracellular cholesterol, and reduced cholesterol influx and de novo synthesis, resulting in decreased intracellular cholesterol levels and cell viability. Furthermore, the inhibitory effect of 27-OHC on A549 cell viability was significantly attenuated after the LXR pathway was partially blocked by 5 μmol/L GSK2033 treatment (P<0.05). CONCLUSION:27-OHC inhibits A549 cell prolife-ration via activation of LXR signaling pathway.     

Let-7a-3p inhibits activity of cancer stem cells in human lung cancer A549 cells by targeting IGF1R

AIM:To study the effect of let-7a-3p on the activity of cancer stem cells in human lung cancer A549 cells and its molecular biological mechanism. METHODS:The exepression levels of let-7a-3p in lung cancer cell lines A549, NCI-H1299, SPC-A1, H1650 and HCC-827, and human normal bronchial epithilial cell line BEAS-2B were compared by RT-qPCR. The lung cancer A549 cells were transfected with let-7a-3p mimic and negative control mimic, as let-7a-3p group and negative control group, respectively, and non-transfected control group was also set up. The content of let-7a-3p in each group was detected by RT-qPCR. Tumor sphere formation assay was used to detect the tumor sphere formation ability in 3 groups of the cancer stem cells. The proportion of cancer stem cells was detected by flow cytometry. The protein levels of NANOG, OCT4 and insulin-like growth factor 1 receptor (IGF1R) were determined by Western blot. The target gene of let-7a-3p was predicted by the bioinformatic method. The relationship between let-7a-3p and IGF1R was analyzed by double luciferase assay. Western blot was used to detect whether IGF1R over-expression antagonized the inhibitory effect of let-7a-3p on the activity of cancer stem cells. A subcutaneous transplantation tumor model was also established and the effect of let-7a-3p in vivo was observed. RESULTS:The expression level of let-7a-3p in the lung cancer cell lines was significantly lower than that in the normal bronchial epithelial cell line (P<0.01). The expression level of let-7a-3p in the A549 cells of let-7a-3p group was significantly up-regulated compared with non-transfected group (P<0.01). The number of tumor spheres in let-7a-3p group was significantly lower than that in non-transfected group. The percentage of CD133⁺ cells in let-7a-3p group was significantly lower than that in non-transfected group (P<0.01). The protein expression of NANOG and OCT4 in let-7a-3p group was significantly lower than that in non-transfected group (P<0.01). Bioinformatic prediction showed that let-7a-3p complementarily matched the 3'-UTR of IGF1R, and IGF1R might be the target gene of let-7a-3p. Luciferase assay confirmed that IGF1R was the direct downstream target gene of let-7a-3p. The protein expression of IGF1R in let-7a-3p group was significantly decreased (P<0.01). Subcutaneously transplantated tumor in let-7a-3p group was significantly smaller than that in non-transfected group. CONCLUSION:Let-7a-3p may affect the expression of lung cancer stem cell-related proteins and inhibit the potential of lung cancer stem cells by down-regulating its downstream target gene IGF1R.