Effects of G6PD silencing by siRNA on expression of HIF-1α in human colon cancer cells

AIM: To study the effects of glucose-6-phosphate dehydrogenase (G6PD) silencing by small interference RNA(siRNA) on the levels of reduced nicotinamide-adenine dinucleotide phosphate (NADPH) and hypoxia-inducible factor 1α(HIF-1α) under hypoxia in human colon cancer cell line LoVo.METHODS: Specific siRNA expression vector targeting G6PD gene was constructed. The recombinant plasmid was identified by restriction endonuclease and DNA sequencing, and then transfected into LoVo cells. The effects of G6PD silencing were evaluated by detecting the activity and mRNA expression of G6PD. LoVo cells were cultured in vitro under hypoxic condition. NADPH levels were determined.The mRNA and protein levels of HIF-1α were analyzed by RT-PCR and Western blotting,respectively. RESULTS: The recombinant plasmid for G6PD silencing by siRNA was successfully constructed and transfected into LoVo cells. Compared with untransfected cells,the mRNA expression of G6PD in transfected cells was decreased by 43% and G6PD activity was decreased by 63.5%. Under hypoxic condition, the level of NADPH in transfected cells was significantly decreased (41% vs 100%, P<0.05).HIF-1α protein was also decreased significantly but its mRNA expression had no change as compared with the control cells. CONCLUSION: G6PD silencing by siRNA decreases NADPH level, resulting in the decline of HIF-1α stability in cancer cells under hypoxic condition. By this mechanism, G6PD silencing can influence the hypoxic responses in cancer.     

Effect of AG490 on expression of VEGF and HIF-1α in HEL cells

AIM: To investigate the effect of AG490 on the expression of VEGF and HIF-1α, and the capacity of invasion in human erythroleukemia (HEL) cells. METHODS: The HEL cells were treated with AG490 at different concentrations. The cell viability was detected by CCK-8 assay. The apoptosis was detected by Hoechst staining. The apoptosis and the cell cycle were analyzed by flow cytometry. The capacity of migration was evaluated by Transwell assay. The mRNA expression level of JAK2 was measured by RT-PCR. The protein levels of p-JAK2, VEGF and HIF-1α were determined by Western blot. RESULTS: The HEL cell viabilities were 88%, 75%, 48%, 10% and 0.12% after treated with AG490 at 20, 40, 60, 80 and 100 μmol/L for 48 h, respectively. The results of Hoechst staining showed that brilliant blue cells in 80 μmol/L AG490 group was significantly increased compared with control group for 48 h. The apoptosis rate of 80 μmol/L AG490 group was significantly increased compared with control group at 48 h after AG490 treatment. The number of membrane-permeating HEL cells in 20 μmol/L AG490 group at 24 h after AG490 treatment was significantly lower than that in control group (P<0.05). The mRNA level of JAK2 decreased in a concentration-dependent manner after the HEL cells were treated with different concentrations of AG490 for 48 h. The protein levels of p-JAK2, VEGF and HIF-1α were lower in AG490 treatment groups than those in control group (P<0.05). CONCLUSION: AG490 inhibits the expression of VEGF and HIF-1α in HEL cells by inhibiting JAK2 pathway.     

Effects of TKTL1 silencing by siRNA on growth microenvironment of human hepatocellular carcinoma HepG2 cells

AIM:To explore the relationship between the expression of transketolase-like 1 protein(TKTL1) and the metastasis of hepatocellular carcinoma by investigating the change of some indicators in growth microenvironment including lactate production, reduced glutathione(GSH) level and ratio of NADPH/NADP⁺ in hepatocellular carcinoma cell line HepG2 after silencing of TKTL1 expression by siRNA. METHODS:Specific siRNA expression vector targeting TKTL1 gene was constructed and transfected into HepG2 cell line. The effect of TKTL1 silencing was evaluated by detecting the mRNA level and the activity of transketolase(TKTL1). The changes of lactate production, GSH level, the ratio of NADPH/NADP⁺ and glucose-6-phosphate dehydrogenase(G-6-PD) activity were observed in transfected HepG2 cells compared with the untransfected control cells. RESULTS:Compared with the untransfected control cells, the mRNA expression of TKTL1 and the TKT activity decreased significantly(P<0.01). Meanwhile, the lactate production, GSH level and ratio of NADPH/NADP⁺ also decreased significantly(P<0.01). However, no change of the G-6-PD activity was observed. CONCLUSION:Carcinoma cells switch the glucose metabolism by overexpression of TKTL1 to modify the lactate production and the levels of reactive oxygen species, thus changing the growth microenvironment in favor of tumor metastasis.     

Effects of HIF-1α silencing on proliferation of rat hepatoma cells

AIM：To study the effect of hypoxia-inducible factor 1α (HIF-1α) silencing on the proliferation of hepatoma cells under hypoxia. METHODS：Rat hepatoma cell line CBRH-7919 was used in this study. Hypoxia model was established by treating the cells with cobalt chloride (CoCl2). The expression of HIF-1α was silenced by small interfe-rence RNA. Real-time RT-PCR and Western blotting were used to detect the mRNA and/or protein expression of HIF-1α, vascular endothelial growth factor (VEGF), p21 and cyclin D1 in CBRH-7919 cells under hypoxia. The proliferation of CBRH-7919 cells was measured by the technique of 5-bromo-2’-deoxyuridine (BrdU) incorporation. RESULTS：The expression of HIF-1α and VEGF at mRNA and protein levels was significantly increased under hypoxia (P<0.05). Silencing of HIF-1α significantly inhibited the expression of HIF-1α, VEGF and cyclin D1 at mRNA and/or protein levels, while increased the protein expression of p21 (P<0.05). The BrdU-positive cells in HIF-1α siRNA transfection group were significantly less than those in control group. CONCLUSION：HIF-1α silencing significantly inhibits the proliferation of hepatoma cells under hypoxia.     

Effect of hypoxia-inducible factor-1α knockdown by siRNA on viability and CEACAM1 expression in oral squamous cell carcinoma

AIM: To investigate the relationship between hypoxia-inducible factor-1α (HIF-1α) and viability and apoptosis of oral squamous cell carcinoma and its mechanism. METHODS: The expression of HIF-1α and carcinoembryonic antigen-related cell adhesion molecular 1 (CEACAM1) at mRNA and protein levels in oral squamous cell carcinoma cell lines Tca8113 and CAL27 and normal epithelial cell line NOK was determined by RT-PCR and Western blot. The expression of HIF-1α in CAL27 cells was silenced by RNA interference (RNAi) technique. The cells were divided into blank control group, non-sense control group and siRNA-HIF-1α group. The viability of CAL27 cells was measured by MTT assay and the apoptotic rate was analyzed by flow cytometry. The protein levels of HIF-1α, P21, vascular endothelial growth factor (VEGF), Bcl-2 and Bax were examined by Western blot. RESULTS: The expression of HIF-1α and CEACAM1 in oral squamous cell carcinoma cells was significantly higher than that in normal cells (P<0.05), and the expression of HIF-1α and CEACAM1 was positively correlated. The protein expression of HIF-1α in siRNA-HIF-1α group was significantly lower than that in blank control group (P<0.05). Knockdown of HIF-1α significantly inhibited CAL27 cell viability (P<0.05), promoted apoptosis (P<0.05), increased the protein levels of P21 and Bax (P<0.05), and significantly decreased the levels of VEGF and Bcl-2 (P<0.05). CONCLUSION: HIF-1α is over-expressed in oral squamous cell carcinoma. Knockdown of HIF-1α significantly inhibits cell viability and promotes apoptosis possibly through regulating the expression of HIF-1α downstream target genes and tumor angiogenesis.     

Effect of hyperbaric oxygen on HIF-1α expression in rat experimental periodontitis with psychological stress

AIM: To investigate the effect of hyperbaric oxygen (HBO) on hypoxia-inducible factor-1α (HIF-1α) expression in rat experimental periodontitis with psychological stress. METHODS: Male special pathogen-free Wistar rats (n=120) were randomly divided into 4 groups: normal control group; psychological stress stimulation group; experimental periodontitis group: the periodontitis model was induced by wrapping 3/0 silk ligature inoculated with Porphyromonas gingivalis around the left maxillary second molar of the rats; periodontitis model with stress stimulation group. Psychological stress was removed at the 9th weeks after ligature, 6 rats from each experiment group were randomly chosen to HBO treatment. The rats were sacrificed at the 2nd, 4th, 8th and 10th weeks after ligature. Gingival index (GI) and attachment loss (AL) were measured before sacrifice. The histological changes of periodontal tissues were observed under microscope with HE staining. The expression of HIF-1α was observed by the method of immunohistochemistry. RESULTS: The sites of gingival attachment were normal in control group and psychological stress stimulation group. Periodontal pocket, and periodontal attachment loss were observed in experimental periodontitis group. The tissue damage was much serious in periodontitis model with stress stimulation group. No significant difference of GI and AL among psychological stress stimulation group and normal control group during the experiment was observed. GI and AL in periodonitis model with stress stimulating group were significantly higher than those in experimental periodontitis group at the 4th and 8th weeks (P < 0.01). The levels of GI and AL were significantly lower at the 10th weeks after HBO treatmnt than those in untreated groups (P < 0.05). No significant difference of HIF-1α expression scores among psychological stress stimulation group and normal control group was found. HIF-1α expression scores in periodonitis model with stress stimulating group was significantly higher than that in experimental periodontitis group at the 4th and 8th weeks (P < 0.01). At the 10th weeks after HBO treatment the levels of HIF-1α were significantly lower than that in untreated groups (P < 0.01). CONCLUSION: Stress stimulation may aggravate periodontitis by decreasing tissue oxygenation in rats. HBO may represent a useful way in psychological stress periodontitis therapy.     

NKX3.1 down-regulates bcl-2 gene expression in prostate cancer PC-3 cells

AIM: To investigate the effect of NKX3.1 on the gene expression of bcl-2 and apoptosis in prostate cancer PC-3 cells. METHODS: The eukaryotic expression plasmid pcDNA3.1- NKX3.1 was transiently transfected into PC-3 cells. RT-PCR and Western blotting were used to detect the effects of NKX3.1 on the expression of bcl-2 gene. Down-regulatory effect of NKX3.1 on bcl-2 gene was detected by EMSA. Flow cytometry and apoptotic body staining were carried out to study the effects of NKX3.1 on apoptosis of PC-3 cells. RESULTS: The mRNA and protein expression of bcl-2 in PC-3 cells was down-regulated by over-expression of NKX3.1. The EMSA result showed that NKX3.1 interacted with the NKX3.1 binding elements in upstream regulatory region of bcl-2 gene. The results of flow cytometry showed that the number of apoptotic PC-3 cells increased by 1.41-fold after NKX3.1 transfection to PC-3 cells. NKX3.1 increased the apoptotic bodies stained by Hoechst 33258 significantly. CONCLUSION: NKX3.1 down-regulates the expression of anti-apoptotic gene bcl-2 and induces the apoptosis of prostate cancer PC-3 cells.     

Effects of airway epithelial cells on phenotype and phagocytosis of macrophages and roles of HIF-1α

AIM: To investigate the effects of airway epithelial cells on the phenotype and phagocytosis of macrophages and the roles of hypoxia-inducible factor-1α (HIF-1α).METHODS: Human bronchial epithelial (HBE) cells treated with CoCl₂ (0, 100, 200, 400 and 800 μmol/L) or transfected with HIF-1α siRNA were co-cultured with the macrophages differentiated from human monocyte line THP-1 induced by phorbol 12-myristate 13-acetate (PMA). The mRNA expression of HIF-1α in the HBE cells was detected by RT-qPCR. The expression of macrophage surface markers and the phagocytosis rate of E.coli by macrophages were analyzed by flow cytometry.RESULTS: CoCl₂ upregulated the mRNA expression of HIF-1α in the HBE cells in a concentration-dependent manner and peaked at 8 h. HBE cells treated with CoCl₂ increased the fluorescence intensity ratio of CCL3, CD163, CD206 and CCL18 in co-cultured macrophages, and the strongest effect was seen in the macrophages co-cultured with HBE cells treated with CoCl₂ at 800 μmol/L. The fluorescence intensity ratio of CCL3 in co-cultured macrophages increased most obviously at 8 h and 12 h, while the fluorescence intensity ratio of CD163, CD206 and CCL18 increased more prominently in the macrophages co-cultured for 24 h. The stimulating effects of the HBE cells transfected with HIF-1α-Homo-488 siRNA on CCL3, CD163, CD206 and CCL18 in the macrophages were significantly attenuated. The phagocytosis rate of E.coli by macrophages co-cultured with HBE cells treated with different concentrations of CoCl₂ for 24 h initially increased (up to 60 min), and then it gradually decreased. Compared with normal HBE co-culture group, the phagocytosis rate in 400 and 800 μmol/L stimulation groups decreased at each time point, and that in 800 μmol/L stimulation group was the most.CONCLUSION: In hypoxia environment, airway epithe-lial cells initially transform macrophages predominantly to an M1-phenotype. However, the long-term hypoxia-stimulated airway epithelial cells inhibit the phagocytosis of macrophages and convert them to M2 superiority. HIF-1α may be an important mediator in these processes.     

Effects of tanshinone IIA on proliferation,apoptosis and expression of HIF-1α, VEGF and wild-type P53 in human hepatoma HepG2 cells under hypoxia

AIM:To investigate the effects of tanshinone IIA (Tan IIA) on proliferation, apoptosis and its molecular mechanism in human hepatoma HepG2 cells under hypoxic condition. METHODS:Hypoxia model was established by treatment with cobalt chloride (CoCl2). The cells were divided into normoxia control group, hypoxia control group and hypoxia combined at different concentrations of Tan IIA groups. After HepG2 cells were incubated with different concentrations of Tan IIA (0.5, 1.0, 2.0, 5.0 and 10.0 mg/L) for 24 h, 48 h and 72 h under hypoxic condition, the cell proliferation was determined by MTT assay. After Tan IIA was added to the media at different concentrations for 24 h and 48 h, the apoptotic cells were observed by Hoechst 33258 staining. The protein levels of hypoxia-inducible factor 1 alpha (HIF-1α), vascular endothelial growth factor (VEGF) and wild-type P53 were detected by Western blotting after cultured with different concentrations of Tan IIA for 48 h. RESULTS:Tan IIA inhibited the proliferation of HepG2 cells in a dose- and time-dependent manner. Tan IIA induced the typical morphology of apoptotic cells and increased the apoptotic rate in a dose- and time-dependent manner after treatment with 1.0 mg/L~5.0 mg/L for 24 h and 48 h under hypoxic condition. The protein levels of HIF-1α and VEGF were weakly expressed in HepG2 cells under normoxia but up-regulated after incubated under hypoxia for 48 h. The protein expression of HIF-1α and VEGF were decreased with the increase in the concentration of Tan IIA under hypoxia. The protein expression of wild-type P53 was increased with the increase in the concentrations of Tan IIA under hypoxia. CONCLUSION: Tan IIA significantly inhibits the proliferation and induces the apoptosis of human hepatoma HepG2 cells under hypoxia, which may be related to the down-regulation of HIF-1α and VEGF and up-regulation of wild-type P53.     

Effects of NBP on expression of VEGF and HIF-1α in HUVECs under the condition of oxygen-glucose deprivation

AIM: To investigate the mechanism that dl-3-n-butylphthalide (NBP) protects cells from the induced by oxygen-glucose deprivation (OGD).METHODS: Human umbilical vein endothelial cells (HUVECs) were exposed to OGD to induce endothelial damage. Endothelial injury was assessed by measuring the changes of chromatin morphology and MTT method. The protein levels of vascular endothelial growth factor (VEGF) and hypoxia inducible factor-1 alpha (HIF-1α) were determined by immunofluorescence and quantitatively analyzed with the software IPP. Western blotting was applied to verify the results.RESULTS: NBP at the concentrations of 0.01 to 100 μmol/L dose-dependently protected against OGD-induced cell damage. Compared with OGD group, NBP enhanced OGD-induced the expression of VEGF and HIF-1α, and the difference was statistically significant. The expression of VEGF and HIF-1α reached to the peak at the time points of 6 h and 8 h after OGD, respectively.CONCLUSION: Under the condition of OGD, NBP enhances the expression of HIF-1α in HUVECs, subsequently promotes the expression of downstream VEGF, and eventually elevates the survival of the cells.     

Effect of RYR1 gene expression knock-down by siRNA on mitochondria in C2C12 cells

AIM: To investigate the effect of ryanodine receptor 1 (RYR1) down-regulation on mitochondria in mouse myoblast C2C12 cell line and to explore the possible mechanism. METHODS: The expression of RYR1 in the C2C12 cells was knocked down by the targeted small interfering RNA (siRNA). The mitochondrial number and morpholo-gical changes were evaluated by transmission electron microscopy and the stereoscopic analysis. Real-time PCR and Western blot were used to determine the mRNA and protein levels of mitofusin 2 (Mfn2), peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) and extracellular signal-regulated kinase 1/2 (ERK1/2), respectively. RESULTS: The expression of RYR1 was significantly down-regulated by siRNA transfection (P<0.01), with fragmentized mitochondria in the C2C12 cells in knock-down (KD) group. Although no statistical difference of the mitochondrial number was observed, the mitochondria area and circumference were significantly lowered in KD group (P<0.05). In KD group, the mRNA and protein expression of Mfn2 was significantly reduced (P<0.01). The mRNA level of PGC-1α was also reduced (P<0.01), but no significant change at protein level was observed. No change of ERK1/2 expression and phosphorylated ERK1/2 level was detected. CONCLUSION: Knock-down of RYR1 expression leads to morphological changes of mitochondria, and down-regulation of Mfn2 expression may be involved in the underlying mechanism. While PGC-1α and ERK1/2-associated oxidative stress pathway may not play an important role in the process.     

Role of HIF-1α/VEGF pathway in treatment of cerebral ischemia-reperfusion injury by hyperbaric oxygen pretreatment

AIM: To investigate the role of hypoxia-inducible factor-1α (HIF-1α)/vascular endothelial growth factor (VEGF) pathway in hyperbaric oxygen (HO) pretreatment in rats with cerebral ischemia-reperfusion (IR) injury. METHODS: Healthy male SD rats (n=32) were randomly divided into control group IR group, HO-IR group and HO-IR-HIF-1α inhibitor group (HO-IR-I group). The IR model was established by middle cerebral artery occlusion. The corresponding blood vessels of the rats in control group were only exposed. The rats in HO-IR group and HO-IR-I group were treated with HO for 4 weeks before the animal modeling. The rats in HO-IR-I group received 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazol (YC-1) by intraperitoneal injection at 4 mg/kg before HO preconditioning every day. At 1 d and 7 d after modeling, the neurological assessment was evaluated.At the end of the 7 th day, after observation, the rats were sacrificed by anesthesia to measure the infarct volume of the brain tissue. The protein levels of HIF-1α, VEGF and apoptosis-related proteins Bax and Bcl-2 were determined by Western blot. The number of apoptotic cells was detected by TUNEL. RESULTS: Compared with control group, the neurological function score was decreased, while the cerebral infarction volume ratio, the protein levels of HIF-1α, VEGF, Bcl-2 and Bax, and the apoptotic cells were increased in IR group, HO-IR group and HO-IR-I group (P<0.05). Compared with IR group, the neurological function score, and the protein levels of HIF-1α,VEGF and Bcl-2 were increased, while the cerebral infarction volume ratio, the protein level of Bax and apoptotic cells were decreased in HO-IR group and HO-IR-I group (P<0.05). Compared with HO-IR group, the neurological function score, and the protein levels of HIF-1α, VEGF and Bcl-2 were decreased, while the cerebral infarction volume ratio, the protein level of Bax and apoptotic cells were increased in HO-IR-I group (P<0.05). CONCLUSION: The mechanism of HO preconditioning attenuating cerebral IR injury may be related to the regulation of apoptosis by inducing HIF-1α/VEGF signaling pathway activation.     

Role of TGF-β1-activated p38 MAPK in up-regulation of PAI-1 expression by TGF-β1 in human ovarian cancer cells

AIM: To investigate the relationship between up-regulation of plasminogen activator inhibitor-1(PAI-1) expression and activation of p38 mitogen-activated protein kinase(p38 MAPK) and extracellular signal-regulated kinase(ERK) pathways by TGF-β1 in human ovarian cancer cells. METHODS: PAI-1 expression in human ovarian cancer cells treated with TGF-β1(10 μg/L)was assayed by real-time PCR and Western blotting. The activation of p38 MAPK and ERK was determined by Western blotting using phosphorylated p38 MAPK and phosphorylated ERK antibodies. Specific p38 MAPK inhibitor(SB203580) or ERK inhibitor(PD98059) was used to inhibit their activation. RESULTS: TGF-β1 up-regulated the expression of PAI-1, and activated p38 MAPK and ERK pathways in the ovarian cancer cells. Inhibition of p38 MAPK activation by SB203580 resulted in significant inhibition of the mRNA expression of PAI-1 induced by TGF-β1. However, inhibition of ERK activation did not significantly alter TGF-β1-induced increase in PAI-1 mRNA level. CONCLUSION: TGF-β1-activated p38 MAPK pathway contributes to the up-regulation of PAI-1 expression by TGF-β1 in ovarian cancer cells.     

Clinical significance of STMN1 expression in cervical cancer and effect of inhibition of its expression on viability and apoptosis of cervical cancer SiHa cells

AIM: To investigate the clinical significance of stathmin 1 (STMN1) expression in cervical cancer and the influence of its expression on the viability and apoptosis of cervical cancer cells. METHODS: Western blot was used to detect the protein expression of STMN1 in cervical cancer tissues, and the relationship between the expression and clinical characteristics of cervical cancer was analyzed. STMN1-siRNA was transfected into cervical squamous-cell carcinoma SiHa cells. The protein levels of STMN1, STAT3, p-STAT3 and survivin were determined by Western blot after transfection for 48 h. The cell viability was measured by MTT assay. The apoptosis was analyzed by flow cytometry. DCFH-DA probe was used to detect the level of reactive oxygen species (ROS). RESULTS: The protein expression of STMN1 in cervical cancer tissues was significantly higher than that in paracancerous tissues (P<0.01). The STMN1 protein expression level was not correlated with age and histological types of cervical cancer patients, but was related to clinical stage, histological differentiation and lymph node metastasis (P<0.01). Transfection with STMN1-siRNA significantly reduced the expression of STMN1 in SiHa cells. Compared with control group, the cell viability in STMN1-siRNA group was significantly decreased, the apoptotic rate and ROS content were increased, and the protein levels of p-STAT3 and survivin were down-regulated (P<0.01). However, no significant difference of the STAT3 protein level was observed between STMN1-siRNA group and control group. CONCLUSION: STMN1 is highly expressed in cervical cancer, and its expression is related to clinical stage, histological differentiation and lymph node metastasis. Inhibition of STMN1 expression reduces the viability and promotes apoptosis of cancer cells by down-regulating STAT3 signaling pathway.     

Effects of integrin αvβ6 on endo-exocytotic cycle of integrin αvβ5 in colon cancer cells

AIM: To investigate the effects of integrin αvβ6 on the endo-exocytotic cycle of integrin αvβ5 in colon cancer cells. METHODS: The expression of integrin αvβ6 and αvβ5 in SW480 cells, SW480 wild-type β6 cells and SW480 mock cells was detected by Western blotting. The trafficking of integrin αvβ6 and αvβ5 was examined by endocytosis assay, exocytosis assay and capture-ELISA. The adhesive and migration abilities of these 3 cell lines towards fibronectin or vitronectin were measured by cell adhesion assay and cell migration assay. RESULTS: The expression of integrin αv and β5 subunits was similar in these 3 cell lines (P>0.05), while the expression of integrin β6 subunit in SW480 wild-type β6 cells was much higher than that in the other 2 cell lines (P<0.05). The transfection of integrin β6 subunit into SW480 cells was able to slow down the endocytosis and exocytosis of integrin αvβ5, and subsequently inhibited the cellular adhesion and migration abilities towards vitronectin. CONCLUSION: Integrin αvβ6 and αvβ5 share the same αv subunit. In the process of endocytosis and exocytosis, there might be some competitive relationship between these 2 integrin isoforms. Compared with integrin αvβ5, integrin αvβ6 has the priority to get into the trafficking process, and it has subsequent effects on the adhesion and migration of colon cancer cells.     

Effects of silencing of COX-2 gene expression by siRNA on cell proliferation,cell cycles,apoptosis and tumorigenicity of human pancreatic cancer Capan-2 cells

AIM: To investigate the effects of silencing of cyclooxygenase-2 (COX-2) gene expression by siRNA on the proliferation, apoptosis, cell cycle and tumorigenicity of human pancreatic cancer Capan-2 cells.METHODS: The gene transfection was performed using Lipofectamine 2000 (Lipo). The proliferation, apoptosis and cell cycle of Capan-2 cells were tested by the methods of cell counting, microscopy and FCM. The mRNA expression of COX-2 was determined by RT-PCR and real-time PCR. The protein level of COX-2 was detected by Western blotting. The tumorigenicity of Capan-2 cells transfected with siRNA-COX-2 was determined using the model of nude mice. RESULTS: Transfection efficiency of 96.47% was obtained under the conditions that the transfection volume was 2 mL, concentration of Lipo was 5 μL and that of siRNA-COX-2 was 50 nmol/L. The best sequence of siRNA-COX-2 for silencing of COX-2 gene expression was siRNA006 with the silencing rate of up to 73% 24 h after tansfection. siRNA-COX-2 slowed down the growth of Capan-2 cells 48 h after transfection (P<0.05). At time points of 48 h and 72 h after transfection, the protein expression of COX-2 was down-regulated to 67% and 61% of the normal level, the proliferation inhibition rate was 35.48% and 56.32%, and the apoptotic rate was 2.03% and 3.27%, respectively. At time points of 24 h, 48 h and 72 h after transfection, the proportion of the cells in G₀/G₁ phrase was 58.03%, 63.31% and 65.66%, and that of the cells in S phase was 30.27%, 24.87% and 22.2%, respectively. The mean volume and weight of tumor tissues were remarkably decreased due to the transplantation of Capan-2 cells transfected with siRNA-COX-2.CONCLUSION: siRNA-COX-2 effectively silences the expression of COX-2 gene, inhibits the growth and decreases the tumorigenicity of Capan-2 cells.