Exogenous activation of LKB1/AMPK signaling induces G1 arrest in cells with endogenous LKB1 expression.

The tumor suppressor protein LKB1 is a serine/threonine kinase that plays a critical role in cell proliferation, and its inactivation has been linked to tumorigenesis in various cancer types. Current understanding of the LKB1 function is largely restricted to results from experiments on LKB1­deficient cancer cells, while the regulation and activity of endogenous LKB1 has been rarely investigated. In a previous study, we showed that LKB1 knockdown in two healthy cell lines accelerates cell cycle progression through the G1/S checkpoint by inhibition of the p53 and p16 pathways. In the present study, we examined the effects of overexpression of LKB1 on two healthy and one cancer cell line. Administration of exogenous LKB1 activated LKB1/AMPK signaling and arrested the cell cycle at the G1 phase in an LKB1-dependent manner. G1 arrest induced by LKB1 was accompanied by the downregulation of cyclin D1 and cyclin D3, and the upregulation of p53, p21 and p16, while no differences were detected for CDK4, CDK6, cyclin E, p15 and p27. These results indicated that exogenous activation of LKB1/AMPK signaling inhibits the G1/S cell cycle transition, even in cells with an endogenous expression of LKB1. Findings of the present study extend earlier observations on LKB1­inactivated neoplastic cells and provide novel insights into the growth-inhibitory effects of LKB1.

Aquaporin-9 downregulation prevents steatosis in oleic acid-induced non-alcoholic fatty liver disease cell models.

Aquaporin-9 (AQP9) is an aquaglyceroporin that acts as the adipose glycerol channel. However, the role of AQP9 in steatosis in non-alcoholic fatty liver disease (NAFLD) has not yet been fully elucidated. In the present study, the coding sequence of the AQP9 gene was obtained from LO2 cells by RT-PCR, and cloned into the pEGFP-N1 vector. Short hairpin RNA (shRNA) targeting the AQP9 gene was inserted into the pGenesil-1 vector. Recombinant plasmids were confirmed by enzyme digestion and sequence analysis, and transfected into cell models (derived from LO2 cells) of oleic acid-induced NAFLD. Our results demonstrated that AQP9 recombinant plasmids can be effectively expressed in cell models of NAFLD. Furthermore, in comparison with the control group, AQP9 overexpression significantly increased intracellular lipid content, triglyceride (TG), free fatty acid (FFA) and glycerol levels; however, the silencing of AQP9 exerted the opposite effects. Taken together, recombinant plasmids used to induce AQP9 overexpression and to silence AQP9 expression were successfully constructed. AQP9 overexpression aggravated the degree of steatosis; however, the silencing of AQP9 alleviated these effects. Based on these data, we suggest that AQP9 may serve as a novel molecular target for therapeutic intervention in NAFLD.

[Construction of short hairpin RNA targeting aquaglyceroporin 9 and screening its effect on molecular mechanisms of nonalcoholic fatty liver disease using a cell model system].

OBJECTIVE: To construct a short hairpin (sh)RNA targeting aquaglyceroporin 9 (AQP9) that effectively silences gene expression in liver cells in order to investigate of the role of AQP9 in nonalcoholic fatty liver disease (NAFLD) pathogenesis using an in vitro cell model system. METHODS: Small interfering (si)RNAs were designed against the human gene sequences encoding AQP9 (NCBI GenBank Accession No. AB008775) and unrelated control sequences, synthesized, annealed to form double-strands, and inserted into the pGenesil- 1 shRNA-expression plasmid. The silencing effects of the four pshRNA-AQP9 constructs (a-d) and the pshRNA-negative control construct were investigated by transfecting into the L02 human normal liver cell line and detecting expression of AQP9 mRNA and protein (relative to beta-actin) by reverse transcription-PCR and western blotting. The NAFLD cell model was established by treating L02 cells with oleic acid to induce fatty degeneration. After transfecting the NAFLD cell model with various constructs, the effects on NAFLD-related features were investigated by staining with Oil Red O (to detect lipid droplets) and performing enzymatic assays (to quantitate triglyceride (TG), free fatty acid (FFA) and glycerol content). The significance of intergroup differences was assessed by analysis of variance test. RESULTS: Of the four pshRNA-AQP9 constructs, pshRNA-AQP9a produced the most robust silencing effect on AQP9 mRNA (25.1 - 1.2% vs. untransfected: 39.3 +/- 1.7% and pshRNA-negative control: 39.4 +/- 1.5%, P < 0.01) and protein (25.4 - 2.0% vs. untransfected: 35.1 +/- 1.9% and psh-RNA-negative control: 35.6 +/- 2.3%, P < 0.01). Oleic acid-induced L02 cells showed enhanced AQP9 mRNA and protein expression, and increased intracellular content of lipid, TG, FFA, and glycerol, which were significantly reduced by pshRNA-AQP9a transfection (all P <0.05). CONCLUSION: The new pshRNA-AQP9a construct can efficiently reduce AQP9 expression in cultured human liver cells and relieve steatosis-related features in an NAFLD cell model, pshRNA-AQP9a represents a novel tool for studying the role ofAQP9 in NAFLD pathogenesis and its potential as a gene therapy strategy.

AdHu5-apoptin induces G2/M arrest and apoptosis in p53-mutated human gastric cancer SGC-7901 cells.

The use of anticancer therapeutic agents is limited largely by their severe toxicity to normal tissues. The development of novel agents with tumor-specific cell-killing and effective gene delivery properties is thus very desirable. We used human adenovirus serotype 5 (AdHu5) as a vehicle to deliver the apoptin gene to specifically target gastric cancer in a recombinant gene delivery approach. AdHu5-apoptin is a safe and efficacious agent for the treatment of gastric cancer (GC). Our results show that apoptin protein encoded by the apoptin gene delivered via AdHu5 significantly inhibited the proliferation of SGC-7901 GC cells. Apoptin reduced the clone number by more than 75% and resulted in cell cycle arrest in the G2/M phase for 48% of the GC cells. It also induced cleavage of caspase-3, caspase-7, and caspase-9 in the GC cells. Intratumoral and peritumoral in vivo injection of AdHu5-apoptin significantly suppressed tumor growth and induced apoptosis in xenogeneic tumors in mice. The apoptosis induced by AdHu5-apoptin was independent of anti-apoptotic Bcl-2 and Bcl-xL proteins and the p53 pathway. Taken together, our results show that AdHu5-apoptin has great potential as a therapeutic agent for effective treatment of gastric tumors.

Oral immunization with recombinant Mycobacterium smegmatis expressing the outer membrane protein 26-kilodalton antigen confers prophylactic protection against Helicobacter pylori infection.

Helicobacter pylori infection is prevalent worldwide and results in chronic gastritis, which may lead to gastric mucosa-associated lymphoid tissue lymphoma and gastric cancer. We have previously reported that oral immunization with recombinant Mycobacterium smegmatis expressing the H. pylori outer membrane protein 26-kilodalton (Omp26) antigen affords therapeutic protection against H. pylori infection in mice. In the present study, we investigated the prophylactic effects of this vaccine candidate on H. pylori challenge in mice. We found that oral immunization with recombinant Mycobacterium Omp26 significantly reduced H. pylori colonization in the stomach compared to inoculation with wild-type M. smegmatis in control mice. Six of the recombinant Mycobacterium-immunized mice (60%) were completely protected from H. pylori infection. The severity of H. pylori-associated chronic gastritis assessed histologically was significantly milder in mice vaccinated with recombinant Mycobacterium than in control animals. Mice immunized with recombinant Mycobacterium showed enhanced antigen-specific lymphocyte proliferation and antibody responses. Moreover, immunization with recombinant Mycobacterium resulted in an increased expression of interleukin-2 and gamma interferon in the stomach and spleen, as determined by reverse transcription-PCR analysis. Our results collectively suggest that vaccination with recombinant Mycobacterium Omp26 confers prophylactic protection against H. pylori infection. The inhibition of H. pylori colonization is associated with the induction of antigen-specific humoral and cell-mediated immune responses.

Dihydroartemisinin induces endoplasmic reticulum stress-mediated apoptosis in HepG2 human hepatoma cells.

AIMS AND BACKGROUND: Previous studies showed that dihydroartemisinin (DHA) possessed antitumor activity in many human tumor cells through the induction of apoptosis. The aim of this study was to investigate the effects of DHA on apoptosis in the human hepatocellular carcinoma cell line HepG2 and the possible molecular mechanisms involved. METHODS: The inhibitory effect of DHA on HepG2 cells was measured by MTT assay. The percentage of apoptotic cells was detected by flow cytometry with double staining of fluorescein isothiocyanate-annexin V/propidium iodide. The intracellular production of reactive oxygen species (ROS) and intracellular Ca2+ concentration ([Ca2+]i) were detected by fluorescence spectrophotometry. Protein expression of GADD153, Bcl-2 and Bax in HepG2 cells was examined by Western blot and immunocytochemistry. RESULTS: DHA significantly inhibited proliferation of HepG2 cells in a dose- and time-dependent manner. The apoptosis rates in HepG2 cells treated with 0, 50, 100 and 200 µmol/L DHA for 24 hours were 2.53 ± 0.88%, 24.85 ± 3.63%, 35.27 ± 5.92% and 48.53 ± 7.76%, respectively. Compared with the control group, DHA significantly increased ROS generation and [Ca2+]i level (P <0.05), with the generation of ROS preceding the increase in [Ca2+]i. An increase in GADD153 and Bax expression and a decrease in Bcl-2 were observed in DHA-treated cells. Pretreatment with the antioxidant N-acetylcysteine could attenuate the effects of DHA in the experiments. CONCLUSION: DHA could inhibit proliferation and induce apoptosis in HepG2 cell lines through increasing the intracellular production of ROS and [Ca2+]i. Endoplasmic reticulum stress-induced apoptosis may contribute to this effect by regulating the expression of GADD153, proapoptotic Bax, and antiapoptotic Bcl-2.

Attenuated Salmonella typhimurium carrying TRAIL and VP3 genes inhibits the growth of gastric cancer cells in vitro and in vivo.

BACKGROUND: Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL) and apoptin (VP3) of chicken anemia virus can selectively induce apoptosis in human tumor cell lines by two different pathways. Salmonella not only delivers functional genes to mammalian cells but also possesses antitumor activity and therefore could be adopted as a novel vector for anticancer therapy. MATERIALS AND METHODS: TRAIL and VP3 genes were cloned into a pBudCE4.1 vector and delivered by attenuated Salmonella typhimurium into gastric cancer cells, and their expression and antitumor effects in nude mice were monitored by Western blot, fluorescence microscopy, MTT assay, TUNEL staining, and immunohistochemistry. RESULTS: pBud-VP3 and pBud-TRAIL-VP3 plasmids were constructed to express TRAIL and apoptin in gastric cancer cells, leading to inhibition of cancer cell proliferation after 48 hours (P < 0.05). TRAIL and VP3 genes in pBudCE4.1 vector were also successfully delivered by attenuated S. typhimurium into gastric cancer cells in vivo, in which both TRAIL and apoptin were expressed. In vivo data indicated that S. typhimurium carring pBud-TRAIL-VP3 induced significant cell growth inhibition and tumor regression (P < 0.05). Moreover, expression of TRAIL and apoptin increased the expression of caspase-3 and caspase-9, resulting in enhanced apoptosis. CONCLUSION: Delivery of TRAIL and VP3 genes by attenuated S. typhimurium can significantly inhibit the growth of gastric cancer cells in vitro and in vivo.

[Overexpression of adiponectin prevents hepatocyte steatosis].

OBJECTIVE: To investigate the effect of adiponectin on hepatocyte steatosis. METHODS: L02 cells were transfected with pEGFP-N1-AdipoQ, a plasmid encoding pEGFP-adiponectin fusion protein, or pEGFP-N1. Lipid droplets in the hepatocytes were observed by oil red staining at 72 h. The contents of TG, FFA and glycerol in hepatocytes were measured. RESULTS: Compared to cells transfected with pEGFP-N1-AdipoQ plasmid, much more lipid droplets were observed in cells transfected with pEGFP-N1 plasmid. TG, FFA and glycerol contents in L02 cells and L02/pEGFP-N1 cells were significantly higher than those in L02/pEGFP-N1-AdipoQ cells. CONCLUSIONS: Overexpression of adiponectin prevent hepatocyte steatosis.

Endogenous LKB1 knockdown accelerates G(1)/S transition through p53 and p16 pathways.

The tumor suppressor LKB1 is inactivated in 90% of Peutz-Jeghers cancer syndrome, 30-40% of non-small cell lung carcinoma, and a variety of other cancers, indicating the loss of LKB1 activity is a critical step in oncogenesis. However, current understanding of LKB1 function is largely limited to the results from cancer cells, and how LKB1 inactivation initiates malignant transformation in normal cells remains unclear. Here we ablated endogenous expression of LKB1 in two normal cell lines: human embryonic kidney 293T cells (HEK-293T cells) and human umbilical vein endothelial cells (HUVECs) by LKB1-specific short hairpin RNAs. Downregulation of endogenous LKB1 lead to a facilitated G(1)/S transition, accompanied by a concomitant increase in Rb phosphorylation (Ser(807/811)). Furthermore, reduced expression of p53 and p16 was observed in LKB1 ablated cells, while no differences were detected for cyclin D1 and cyclin E. These results jointly suggest that endogenous LKB1 knockdown accelerates cell cycle progression through G(1)/S checkpoint in HEK-293T cells and HUVECs, which is at least in part, mediated by decline of p53 and p16 pathways. Our findings provided a plausible mechanism by which loss of LKB1 expression in normal cells contributes to the formation of malignancies.

[Anti-tumor effect of eukaryotic expressing plasmid containing soluble tumor necrotic factor-related apoptosis inducing ligand combined with human angiostatin Kringle (1 - 3) genes on human gastric cancer xenografts in nude mice].

OBJECTIVE: To investigate the anti-tumor effect of eukaryotic expressing plasmid containing human angiostatin Kringle (1 - 3) [hAG (K1-3)] combined with soluble tumor necrotic factor-related apoptosis inducing ligand (sTRAIL) genes on human gastric cancer xenografts in nude mice. METHODS: Recombinant plasmids of pBud-hAG and pBud-hAG-TRAIL were constructed by subcloning technique. Twenty nude BALB/c mice were inoculated with human gastric cancer cells of the line BGC-823 subcutaneously into the back. One week later after the appearance of implanted tumors the mice were randomly divided into 4 groups with pBud-hAG, pBud-hAG-TRAIL, pBud blank plasmid, and normal saline (NS) injected into the tumors respectively once the other day for 7 times. The size of tumor was observed. 7 days later the mice were killed with their tumors taken out. RT-PCR was used to detect the expression of hAG and sTRAIL. The microvessel density (MVD) of tumor was observed and recorded by detecting the protein of CD34 with immunohistochemistry on the microscopy. RESULTS: The MVD of tumor in the pBud-hAG-TRAIL and pBud-hAG groups were (4.8 +/- 0.9)/HP and (4.6 +/- 1.2)/HP respectively, significantly lower than those of the pBud and NS groups [(17.4 +/- 2.4)/HP and (18.2 +/- 2.7)/HP respectively, all P < 0.05], but there was no significant difference between the pBud-hAG-TRAIL and pBud-hAG groups. mRNA expression and protein expression of sTRAIL and hAG were positive in the pBud-hAG-TRAIL and pBud-hAG groups. The tumor volumes of tumors of the pBud-hAG-TRAIL and pBud-hAG groups were (1.325 +/- 0.012) cm(3) and (1.862 +/- 0.017) cm(3) respectively, both significantly lower than those of the pBud and NS groups [(3.637 +/- 0.032) cm(3) and (3.521 +/- 0.028) cm(3) respectively, all P < 0.05]. CONCLUSION: Angiostatin inhibits tumor angiogenesis through inhibiting the growth of vascular endothelial cells, and TRAIL induces tumor cell apoptosis. hAG (K1-3) combined with TRAIL can inhibit tumor growth more efficiently.

Recombinant Mycobacterium smegmatis mc(2)155 vaccine expressing outer membrane protein 26 kDa antigen affords therapeutic protection against Helicobacter pylori infection.

Orally administered recombinant Mycobacterium smegmatis (rM. smegmatis) vaccines represent an attractive option for mass vaccination programmes against various infectious diseases. Therefore, in the present study, we evaluated the capacity of the outer membrane protein 26kDa antigen (Omp26) of Helicobacter pylori (H. pylori) to induce therapeutic protection against H. pylori infection in mice. Omp26 was cloned and expressed in M. smegmatis mc(2)155 as a fusion with the Mycobacterium fortuitum beta-lactamase protein under the control of the up-regulated M. fortuitum beta-lactamase promoter, pBlaF. The rM. smegmatis strain was shown to be relatively stable in vitro in terms of plasmid stability and bacterial persistence. We found that oral immunization of H. pylori-infected mice with rM. smegmatis-Omp26 induced protection, i.e., significant reduction in bacterial colonization in the stomach. The protection was strongly related to serum specific antibodies with a Th(1) and Th(2) profile as well as to local cytokines in the stomach and spleen. These findings suggest that Omp26 is a promising vaccine candidate antigen for use in a therapeutic vaccine against H. pylori. The rM. smegmatis expressing Omp26 antigen could constitute an effective, low-cost combined vaccine against H. pylori.

RNA interference-mediated silencing of the Hsp70 gene inhibits human gastric cancer cell growth and induces apoptosis in vitro and in vivo.

AIMS AND BACKGROUND: The role of heat shock protein (HSP) 70 in gastric cancer has been extensively examined in many studies for the past decade. It has been demonstrated that over-expression of Hsp70 might play important role in malignant transformation and maintenance of malignant phenotypes. Therefore, silencing the Hsp70 gene could be applicable in molecular therapies of human gastric cancer. Herein, we designed a small interfering RNA targeting Hsp70 to knock down its expression and investigated its effect on cell proliferation and apoptosis in a gastric cancer cell line. METHODS: Two plasmids (phsp1-siRNA, phsp2-siRNA), along with a negative control (phsp3-siRNA), were created using a genic recombination technique. BGC823 cell lines were used to perform experiments. Western blotting and RT-PCR were used to detect Hsp70 expression in vitro and in vivo. Cell morphology was observed under light microscope. Cell cycle and apoptosis were analyzed by flow cytometry and acridine orange/ethidium bromide double stain, and cell proliferative activity was measured by alamarblue assay. In all experiments, a negative control served as a baseline measure. RESULTS: We successfully constructed phsps-siRNA plasmids and transfected them into BGC823 cells. RT-PCR and western blotting revealed that the expression of Hsp70 was down-regulated in transfection groups compared with the control group. Flow cytometric analysis indicated that less S-phase fraction accumulated in small interfering RNA transfected cells than in parental cells and the cells transfected with empty vector. CONCLUSIONS: Our results demonstrated that RNAi against Hsp70 could effectively knock down gene expression, inhibit growth of cancer cells, induce cell cycle arrest and increase cell apoptosis in vitro and in vivo. Hsp70 might serve as a therapeutic target for human gastric cancer.

Comparison of esomeprazole enteric-coated capsules vs esomeprazole magnesium in the treatment of active duodenal ulcer: a randomized, double-blind, controlled study.

AIM: To evaluate the efficacy and tolerability of two different preparations of esomeprazole in healing duodenal ulcers. METHODS: A total of 60 patients with active duodenal ulcers were enrolled and randomized to receive esomeprazole enteric-coated capsules (40 mg) or esomeprazole magnesium (40 mg), once daily, for 4 consecutive wk, with ulcer healing being monitored by endoscopy. Safety and tolerability were also assessed. RESULTS: Fifty seven patients completed the whole trial. The ulcer healing rates at the end of wk 2 were 86.7% and 85.2% in the esomeprazole enteric-coated capsules and esomeprazole magnesium groups, respectively (P = 0.8410), and reached 100% at the end of wk 4 in both groups. Symptom relief at the end of wk 2 was 90.8% in the esomeprazole enteric-coated capsules group and 86.7% in the esomeprazole magnesium group (P = 0.5406); at the end of wk 4 symptom relief was 95.2% and 93.2%, respectively (P = 0.5786). Adverse events occurred in 16.7% of the esomeprazole enteric-coated capsules group and 14.8% of the esomeprazole magnesium group (P = 1.0000). CONCLUSION: The efficacies of esomeprazole enteric-coated capsules and esomeprazole magnesium in healing duodenal ulcer lesions and relieving gastrointestinal symptoms are equivalent. The tolerability and safety of both drugs were comparable.

[Effects of pshRNA-DNMT1 on the proliferation and apoptosis of gastric cancer: experiments in vitro and in vivo].

OBJECTIVE: To investigate the effects of pshRNA-DNMT1 on the proliferation and apoptosis of gastric cancer. METHODS: Recombinant eukaryotic expression plasmid pshRNA-DNMT1 containing the sequence of the gene of DMNT1 that methylates the specific pyrimidine residue in the DNA promoter region was constructed. Human gastric cells of the line AGS were cultured and transfected with pshRNA-DNMT1. Western blotting was used to detect the protein expression of DNMT1 of the AGS cells, and RT-PCR was used to detect the mRNA expression of DNMT1 of the AGS cells. MTT method was used to dynamically monitor the surviving cells and the cell apoptotic was observed by electron microscopy and TUNEL method. Forty nude the mice were inoculated with suspension of AGS cells. When the tumor reached the size of 5 - 6 mm in diameter the mice were randomly divided into 5 equal groups to be injected intravenously with PBS, liposome, pTZU6 + 1, pshRNA-DNMT1 of medium dose, and pshRNA-DNBMT1 of large dose for 4 times with an interval of 3 days. The tumor size was measured every day. Three days after the last injection the mice were killed and the tumors were taken out to undergo light and electron microscopy and TUNEL method to detect the cell apoptosis. Immunohistochemistry was used to detect the proliferating cell nuclear antigen (PCNA) of the cells. RESULTS: The protein and mRNA expression levels of DNMT1 in the cultured AGS cells 24, 48, and 72 hours after transfection of the pshRNA-DNMT1 group were all lower than those of the control group. The numbers of surviving AGS cells of the pshRNA-DNMT1 group became significantly gradually lower than those of the liposome and pTZU6 + 1 groups since 24 hours after transfection (all P < 0.05). The apoptotic rate of AGS cells in the pshRNA-DNMT1 group was 34.78% +/- 0.52%, significantly higher than those of the liposome and pTZU6 + 1 groups (4.86% +/- 0.17% and 5.12% +/- 0.76% respectively, both P < 0.05). The subcutaneous tumors of the mice of the PGS, liposome, and pTZU6 + 1 groups augmented along with time without significant differences among these 3 groups (all P > 0.05). The tumor of the 2 pshDNMT1 groups began to augment since the 5(th) day and began to be reduced in size since the 10(th) day in comparison with the other 3 groups (all P < 0.05), and the tumor size of the pshRNA-DNMT1 (large dose) group was significantly smaller than that of the pshRNA-DNMT1 (medium dose) group 15 days after the injection (P < 0.05). The rates of cell apoptosis of the pshRNA-DNMT1 (large dose) and pshRNA-DNMT1 (medium dose) groups were both significantly higher than those of the other 3 groups (all P < 0.05) and with a sufficient difference between these 2 pshRNA-DNMT1 groups (P < 0.05). PCNA analysis showed that the proliferation activity of the cells in the pshRNA-DNMT1 groups was significantly suppressed. CONCLUSION: The recombinant plasmid pshRNA-NMT1 effectively and specifically inhibits the expression of the gene DNMT1, thus inhibiting the proliferation and inducing the apoptosis of gastric cancer cells.

[Effects of dnmt1 gene silencing on cell cycle, proliferation, and apoptosis of gastric cancer cell line AGS].

BACKGROUND & OBJECTIVE: Dnmt1, a major DNA methyltransferase gene, is highly expressed in many cancers and lowly expressed in normal adult cells, therefore, its overexpression is closely related to tumorigenesis. This study was to assess effects of dnmt1 gene silencing on cell cycle, proliferation, and apoptosis of gastric cancer cell line AGS. METHODS: The eukaryotic expression plasmid pshRNA-dnmt1, containing the sequence of short hairpin RNA (shRNA) targeting dnmt1, was constructed and transfected into AGS cells. PBS-treated cells and pTZU6+1-transfected cells were set as control. The expression levels of dnmt1 were detected by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot. Cell cycle was analyzed by flow cytometry; cell survival was analyzed by MTT assay; cell apoptosis was evaluated by AO/EB double staining, electron microscopy, and TUNEL. RESULTS: pshRNA-dnmt1 targeting dnmt1 was successfully constructed, and confirmed by sequencing. Relative to control, 24, 48, and 72 h after transfection of pshRNA-dnmt1, the inhibitory rates of dnmt1 protein levels in AGS cells were 28.24%, 68.54%, and 81.47%, respectively, and those of dnmt1 mRNA levels were 21.63%, 52.97%, and 72.06%, respectively. The growth of AGS cells was suppressed 72 h after transfection: S phase cells were reduced from (36.58+/-1.76)% to (18.54+/-6.59)% (P<0.05), and G(2)/M phase cells were increased from (6.18+/-0.32)% to (18.53+/-1.42)% (P<0.05). Cell survival rates were 79.49%, 51.63%, and 39.16%, respectively, 24, 48, and 72 h after transfection of pshRNA-dnmt1. A lot of apoptotic and necrosis cells were observed after transfection. CONCLUSIONS: The recombinant plasmid pshRNA-dnmt1 can efficiently and specifically inhibit the expression of dnmt1 gene and the proliferation of AGS cells, and induce cell apoptosis. It provides evidence for gene therapy of human cancers.

[Establishment of cellular hypoxia model and its effects on biological behavior of gastric cancer cell line SGC-7901].

BACKGROUND & OBJECTIVE: Hypoxia is an elementary characteristic of tumor microenvironment. Establishing hypoxia microenvironment in vitro will be of help in studying the effects of hypoxia on tumor cells. Previous methods of establishing hypoxic cell culture model are fussy, and researches on the effects of hypoxia on gastric cancer cells are rare. This study was to establish hypoxia microenvironment with GasPaK method in vitro, and observe the effects of hypoxia on biological features of gastric cancer cell line SGC-7901. METHODS: The hypoxia microenvironment was established by GasPaK method; the changes of PO2, PCO2, and pH in RPMI-1640 were monitored by blood gas analysis. The effect of hypoxia on cell cycle of SGC-7901 cells was analyzed by flow cytometry (FCM). The morphology of SGC-7901 cells was observed under light microscope and transmission electron microscope. Live cells were counted with trypan blue staining. The adhesiveness of SGC-7901 cells was detected by MTT assay; migration ability of SGC-7901 cells was assessed by movement experiment. RESULTS: GasPaK formed hypoxia microenvironment in 0.5-48 h with stable PO2, PCO2, and pH. When cultured in hypoxia for 16 h, no significant change in cell cycle of SGC-7901 cells was observed; morphology of some SGC-7901 cells was changed; the number of live cells didn't significantly decreased; the adhesiveness and migration ability of SGC-7901 cells were significantly enhanced. CONCLUSIONS: GasPaK method can stably establish hypoxia microenvironment with good repetition. Hypoxia has slight effect on SGC-7901 cells, and may induce morphologic change of SGC-7901 cells.

Diagnosis of Helicobacter pylori infection and diseases associated with Helicobacter pylori by Helicobacter pylori outer membrane proteins.

AIM: To examine the serological response of patients with upper gastrointestinal diseases and Helicobocter pylori (H pylori) infection to two H pylori outer membrane proteins (OMPs) (Mr18,000 and Mr 26,000) acquired by gene recombinant technique, and to determine the diagnostic significance of serological tests derived from these OMPs. METHODS: Recombinant vectors encoding the two H pylori OMPs were used to transform and express in BL21 (DE3) E.coli. After purification with Ni2+-NTA agarose resin, colloid gold kits were prepared with purified recombinant proteins to detect H pylori infection and H pylori-associated diseases by the immunity-marker technology. We selected 150 patients with H pylori infection and digestive symptoms without previous treatment, including chronic gastritis (n = 60), duodenal ulcer (n = 30), gastric ulcer (n = 30), and gastric cancer (n = 30). As controls, 33 H pylori-negative healthy volunteers were also recruited. Serum samples were collected from all subjects, and the antibodies to specific proteins of H pylori were tested with the colloid gold test kits. The sensitivity, specificity and accuracy of the colloid gold tests were evaluated, by using the combination of standard diagnostic methods (13C urea breath test and bacteria culture) and classic enzyme-linked immunosorbent assay (ELISA) as reference. RESULTS: After purification with Ni2+-NTA agarose resin, the purity of recombinant fusion proteins was about 95%. The recombinant fusion proteins were recognized by the specific monoclonal antibodies against the two H pylori OMPs, as demonstrated by the ELISA. Of the 150 serum samples from patients infected with H pylori 141 (94.0%) responded positively to the recombinant protein with Mr 26,000, while the seropositive rates were 95.0%, 96.7%, 96.7% and 90.0% for patients with H pylori-associated chronic gastritis, duodenal ulcer, gastric ulcer, and gastric cancer respectively. The sensitivity, specificity, and accuracy of the colloid gold kit with Mr 26,000 protein were 94.0%, 97.0%, and 94.5%, respectively. Compared with the classic ELISA, bacteria culture and 13C urea breath test results in detecting H pylori-infection, there was no significant difference (P>0.05). For the colloid gold kit with Mr 18,000, the seropositive rates were 52.0%, 40.0%, 40.0%, 53.3% and 86.7%, respectively, in H pylori-infected patients, and those with H pylori-associated chronic gastritis, duodenal ulcer, gastric ulcer, and gastric cancer. There was a significant difference (P<0.05) in seropositivity between patient with gastric cancer (86.7%) and those with other diseases (43.3%). CONCLUSION: The two colloid gold kits derived from the recombinant OMPs are useful tools either for detecting H pylori infection, or for, predicting H pylori-associated gastric malignancy.

Cloning and sequence analysis of gene oipA encoding an outer membrane protein of human Helicobacter pylori.

AIM: To construct a recombinant E. coli strain that would highly express the proinflammatory outer membrane protein of human Helicobacter pylori (H pylori). METHODS: The oipA DNA was amplified by PCR, inserted into pET-32a, and transformed into Top10 E. coli strain. This recombinant plasmid of Top10 was sent out for nucleotide sequence analysis. Finally this sequence AF479754 was compared with HP0638 and JHP0581. RESULTS: The sequence of the aim gene was obtained. It had 924 base pairs. The identity was 95.32% against HP0638, 95.02% against JHP0581, which was higher than the identity between HP0638 and JHP0581. CONCLUSION: Although the aim gene was obtained, but it was different from the published sequence of GenBank. It is not clear what makes this difference. Maybe it is because different strain was used or because there were some variations. So more researches are required to prove it.