Gene Therapy Of Gastric Cancer Research Articles

The Roles of Beclin 1 Expression in Gastric Cancer: A Marker for Carcinogenesis, Aggressive Behaviors and Favorable Prognosis, and a Target of Gene Therapy.

Beclin 1 is encoded by Becn1, and plays a role in tumorigenesis, neurodegeneration, apoptosis and autophagy. Here, the aggressive phenotypes and relevant proteins were examined after Beclin 1 expression was altered in gastric cancer cells. We also observed the effects of Beclin 1 on gastric carcinogenesis using Becn1 knockout mice. Finally, clinicopathological significances of Beclin 1 expression were analyzed using meta- and bioinformatics analyses. Becn1 overexpression was found to inhibit proliferation, glucose metabolism, migration and invasion of gastric cancer cells, whereas its knockdown caused the opposite effects. Beclin 1 suppressed the tumor growth by decreasing proliferation and increasing apoptosis. The heterozygous abrogation of Becn1 in gastric pit, parietal and chief cells could not cause any epithelial lesion. Beclin 1-mediated chemoresistance was closely linked to the autophagy, Bax underexpression, and the overexpression of Bcl-2, LRP1, MDR1, and ING5. Bioinformatics analysis showed higher Becn1 mRNA expression in intestinal- than diffuse-type carcinomas (P<0.05), and in male than female gastric cancer patients (P<0.05). Becn1 hyperexpression was positively associated with both overall and progression-free survival rates of the cancer patients (P<0.05). Meta-analysis showed that down-regulated Beclin 1 expression in gastric cancer was positively with lymph node metastasis, TNM staging, dedifferentiation and poor prognosis (P<0.05). Becn1-related signal pathways in gastric cancer included prostate, lung, renal, colorectal, endometrial and thyroid cancers, glioma, and leukemia, the metabolism of amino acid, lipid and sugar, and some signal pathways of insulin, MAPK, TRL, VEGF, JAK-STAT, chemokine, p53, lysosome, peroxidome and ubiquitin-mediated protein degradation (P<0.05). These suggested that Beclin 1 might be considered as a potential marker of gastric carcinogenesis, aggressiveness and prognostic prediction, and as a target of gene therapy in gastric cancer.

Increasing oxaliplatin sensitivity by down-regulation the expression of EZH2 in human gastric cancer SGC7901 cells

Objective To investigate the effect of enhancer of zeste homolog 2 (EZH2) knockdown on chemosensitivity to oxaliplatin in human gastric cancer cell line SGC7901. Methods Small interfering RNA (siRNA) fragments were designed and synthesized for EZH2 mRNA sequence and divided into siRNA-1 group, siRNA-2 group and siRNA-3 group. They were transfected into gastric cancer cell line SGC7901. The negative control group and blank control group were set up at the same time. The expressions of EZH2 mRNA and protein in the SGC7901 cells were detected by quantitative real-time polyme-rase chain reaction (qRT-PCR) and Western blotting. CCK-8 assay was used to detect cell proliferation inhibition rates of SGC7901 cells treated by different concentrations of oxaliplatin. Results After transfection of EZH2 siRNA, the relative expression levels of EZH2 mRNA in siRNA-1 group, siRNA-2 group, siRNA-3 group were 0.615±0.190, 0.241±0.152 and 0.450±0.097. The relative expression levels of EZH2 mRNA of the three groups were lower than that in the negative control group (1.165±0.376), and the differences were statistically significant (P=0.028; P=0.002; P=0.007). After transfection of the best siRNA fragment into SGC7901 gastric cancer cells, the relative expre-ssion levels of EZH2 protein in interference group, blank control group and negative control group were 0.036±0.017, 0.362±0.026 and 0.398±0.036, and the diffe-rence among the three groups was statistically significant (F=157.745, P<0.001). The difference between interference group and negative control group was statistically significant (P=0.001), as compared with the blank control group (P=0.002). When oxaliplatin concentration was 2, 4, 8 and 16 μg/ml, the differences of cell proliferation inhibition rate among interference group, negative control group and blank control group were statistically significant [(18.107±2.822)%, (5.867±2.272)%, (5.333±1.883)%, F=28.185, P=0.001; (54.953±2.550)%, (22.177±1.871)%, (20.077±6.032)%, F=74.206, P<0.001; (60.337±1.641)%, (34.597±3.592)%, (30.227±5.273)%, F=54.897, P<0.001; (78.340±2.081)%, (61.857±3.507)%, (63.077±8.473)%, F=8.586, P=0.017]. There was no significant difference among groups of oxaliplatin at the concentration of 32 μg/ml [(83.450±3.715)%, (72.190±3.948)%, (70.731±17.080)%, F=1.358, P=0.326]. The median inhibitory concentration (IC50) of oxaliplatin in siRNA group, negative control group and blank control group were 5.178, 12.643, 13.601 μg/ml. Conclusion Down-regulation of EZH2 gene expression can significantly inhibit the proliferation of gastric cancer cells, and effectively enhance the sensitivity of gastric cancer cells to oxaliplatin, which indicates EZH2 may play important roles in the development of gastric cancer chemotherapy. These results provide an important theoretical basis for gene therapy of gastric cancer. Key words: Stomach neoplasms; RNA, small interfering; Enhancer of zeste homolog 2; Oxaliplatin

Silencing of ENO1 by shRNA Inhibits the Proliferation of Gastric Cancer Cells

α-Enolase is a significant subunit of enolase and acts as a glycolytic enzyme responsible for catalyzing the conversion of 2-phosphoglycerate to phosphoenolpyruvate in the anaerobic glycolysis pathway. The research about their role is known little in tumor invasion and metastasis. This research analyzed the effect of α-enolase in proliferation and progression of human gastric cancer. The constructed PLKO.1-ENO1 shRNA vector was transfected into 293 T cells and used to infect gastric cancer cells, MKN45, by using lentivirus method. Negative controls were generated by infection with viruses containing empty vector PLKO.1-scramble-shRNA by the same protocol and using wild-type MKN45 cells as blank control. The silencing effect was confirmed by reverse transcription polymerase chain reaction and Western blotting at messenger RNA and protein levels, respectively. Cell proliferation and chemosensitivity were tested by methyl-thiazolyl-tetrazolium assay. Cell apoptosis was tested by flow cytometry. The cell line α-enolase short hairpin RNA stabling silence α-enolase was successfully constructed. In the α-enolase short hairpin RNA cell lines, messenger RNA and protein expression of α-enolase were significantly lower than those in negative control and blank control groups. The proliferation and clone formation ability were significantly inhibited, cell apoptosis was increased significantly, and the inhibition rate of chemotherapy drugs was increased (P < .05). Our data provide strong evidence that α-enolase short hairpin RNA interference vector can effectively suppress the proliferation and increase chemosensitivity of MKN45 cells, which may provide a novel gene therapy for gastric cancer.

Clinicopathological significance of CHFR promoter methylation in gastric cancer: a meta-analysis.

The mitotic checkpoint gene (CHFR) (Checkpoint with Forkhead-associated and Ring finger domains is a G2 phase/mitosis checkpoint and tumor-suppressor gene. Recent studies have reported the relationship of CHFR promoter methylation with clinicopathological significance of gastric cancer. However, the results remain unclear due to small size of sample. We pooled 15 studies including 827 gastric cancer patients and conducted a meta-analysis to investigate the clinicopathological significance of CHFR promoter methylation in gastric cancer. Our data revealed that the frequency of CHFR promoter methylation was higher in gastric cancer than in normal gastric tissue, Odd Ratio (OR) was 10.12 with 95% CI 5.17–19.79, p < 0.00001. Additionally, the rate of CHFR promoter methylation was significantly increased in high grade of gastric cancer compared to low grade, OR was 1.64 with 95% CI 1.00–2.68, p = 0.05. CHFR methylation was significantly associated with the positive lymph node metastasis, OR was 1.56 with 95% CI 1.05–2.32, p = 0.03. We concluded that CHFR could serve as a biomarker for diagnosis of gastric cancer, and a drug target for development of gene therapy in gastric cancer. CHFR promoter methylation is associated with tumor poor differentiation and lymph node metastasis.

Up-regulation of VEZT by small activating RNA inhibits the proliferation, invasion and migration of gastric cancer cells

ObjectiveTo identify an effective saRNA sequence that can specifically up-regulate VEZT expression and to determine the influence of saRNA had on gastric cancer cell growth, proliferation, invasion and migration. MethodsThree various saRNAs, that target the VEZT gene promoter at different locations relative to the transcription start site were synthesized. A dsControl saRNA was synthesized as a negative control, and a specific shRNA was synthesized to knockdown VEZT and eliminate any off-target effects of the saRNA. Both SGC-7901 and M-28 cells were either transfected with the different saRNAs, or treated with Lipofectamine2000 alone. To determine the most effective saRNA, real-time PCR and Western blot were used to determine the VEZT mRNA and protein content, respectively, of each treatment group. After selection, both cell lines were treated with the chosen saRNA, dsControl or Lipofectamine2000. The saRNA treated cells were divided into two groups: the first group was used immediately in the experiments, and the second group was transfected with shRNA by using RNAi-Mate. The proliferation of cells transfected with saRNA, or saRNA and shRNA, as well as the other control cells, was detected by CCK-8. The invasive and migratory abilities were determined using the transwell chamber assay. ResultsWe identified the most effective saRNA via real-time PCR and Western blot. The selected saRNA inhibited the growth, invasion and migration of GC cells by specially reactivating VEZT. The real-time PCR and Western blot results showed that treatment with saRNA caused a significant up-regulation of VEZT, and an obvious decrease in the proliferative, invasive and migratory abilities; compared with the control groups (P < 0.01); furthermore, there were no significant differences among the control groups (P > 0.05). This phenomenon provides a theoretical basis for saRNA design and gene therapy for gastric cancer.

Application of Mesenchymal Stem Cells in the Targeted Gene Therapy for Gastric Cancer.

The incidence of gastric cancer is third most prevalent among all malignant tumors in China. The conventional therapies for advanced gastric cancer are futile. Targeted gene therapy has become a promising alternative approach. Mesenchymal stem cells (MSCs) can be used as potential cellular vehicles for cancer therapy in vivo. This review will summarize the published data about the application of MSC-based targeted therapy for gastric cancer, and discuss some of the challenges associated with this method.

Synergistic tumor suppression by adenovirus-mediated ING4/PTEN double gene therapy for gastric cancer.

Both inhibitor of growth 4 (ING4) and phosphatase and tensin homolog (PTEN) have been shown to be strong candidate tumor suppressors. However, the combined efficacy of ING4 and PTEN for human gastric cancer remains to be determined. In this report, we constructed a multiple promoter expression cassette-based recombinant adenovirus coexpressing ING4 and PTEN (AdVING4/PTEN), assessed the combined effects of AdVING4/PTEN on gastric cancer using wild-type p53 AGS and SNU-1 human gastric cancer cell lines, and elucidated its underlying mechanisms. We found that AdVING4/PTEN-induced synergistic growth inhibition and apoptosis in vitro AGS or SNU-1 tumor cells and in vivo AGS xenografted tumors subcutaneously inoculated in athymic BALB/c nude mice. Mechanistically, AdVING4/PTEN exhibited an enhanced effect on upregulation of p53, Ac-p53 (K382), P21, Bax, PUMA, Noxa, cleaved Caspase-9, cleaved Caspase-3 and cleaved PARP as well as downregulation of Bcl-2 in vitro and in vivo. In addition, AdVING4/PTEN synergistically downregulated tumor vessel CD34 expression and reduced microvessel density, and additively inhibited vascular endothelial growth factor (VEGF) expression in vivo. The synergistic tumor suppression elicited by AdVING4/PTEN was closely associated with the synergistic induction of apoptosis possibly via enhancement of endogenous p53 responses through cooperatively facilitating p53's stability and acetylation, and the synergistic inhibition of tumor angiogenesis probably via overlapping reduction of VEGF through cooperatively downregulating hypoxia inducible factor-1α's level and transcription activity. Thus, our results indicate that cancer gene therapy combining ING4 and PTEN may constitute a novel and effective therapeutic modality for human gastric cancer and other cancers.

BTG1 expression correlates with pathogenesis, aggressive behaviors and prognosis of gastric cancer: a potential target for gene therapy.

Here, we found that BTG1 overexpression inhibited proliferation, migration and invasion, induced G2/M arrest, differentiation, senescence and apoptosis in BGC-823 and MKN28 cells (p < 0.05). BTG1 transfectants showed a higher mRNA expression of Cyclin D1 and Bax, but a lower mRNA expression of cdc2, p21, mTOR and MMP-9 than the control and mock (p < 0.05). After treated with cisplatin, MG132, paclitaxel and SAHA, both BTG1 transfectants showed lower mRNA viability and higher apoptosis than the control in both time- and dose-dependent manners (p < 0.05) with the hypoexpression of chemoresistance-related genes (slug, CD147, GRP78, GRP94, FBXW7 TOP1, TOP2 and GST-π). BTG1 expression was restored after 5-aza-2'-deoxycytidine treatment in gastric cancer cells. BTG1 expression was statistically lower in gastric cancer than non-neoplastic mucosa and metastatic cancer in lymph node (p < 0.05). BTG1 expression was positively correlated with depth of invasion, lymphatic and venous invasion, lymph node metastasis, TNM staging and worse prognosis (p < 0.05). The diffuse-type carcinoma showed less BTG1 expression than intestinal- and mixed-type ones (p < 0.05). BTG1 overexpression suppressed tumor growth and lung metastasis of gastric cancer cells by inhibiting proliferation, enhancing autophagy and apoptosis in xenograft models. It was suggested that down-regulated BTG1 expression might promote gastric carcinogenesis partially due to its promoter methylation. BTG1 overexpression might reverse the aggressive phenotypes and be employed as a potential target for gene therapy of gastric cancer.

The roles of BTG3 expression in gastric cancer: a potential marker for carcinogenesis and a target molecule for gene therapy.

BTG (B-cell translocation gene) can inhibit cell proliferation, metastasis and angiogenesis, cell cycle progression, and induce differentiation in various cells. Here, we found that BTG3 overexpression inhibited proliferation, induced S/G2 arrest, differentiation, autophagy, apoptosis, suppressed migration and invasion in MKN28 and MGC803 cells (p < 0.05). BTG3 transfectants showed a higher mRNA expression of p27, Bax, 14-3-3, Caspase-3, Caspase-9, Beclin 1, NF-κB, IL-1, -2, -4, -10 and -17, but a lower mRNA expression of p21, MMP-9 and VEGF than the control and mock (p < 0.05). At protein level, BTG3 overexpression increased the expression of CDK4, AIF, LC-3B, Beclin 1 and p38 (p < 0.05), but decreased the expression of p21 and β-catenin in both transfectants (p < 0.05). After treated with cisplatin, MG132, paclitaxel and SAHA, both BTG3 transfectants showed lower viability and higher apoptosis than the control in both time- and dose-dependent manners (p < 0.05). BTG3 expression was restored after 5-aza-2'-deoxycytidine or MG132 treatment in gastric cancer cells. BTG3 expression was decreased in gastric cancer in comparison to the adjacent mucosa (p < 0.05), and positively correlated with venous invasion and dedifferentiation of cancer (p < 0.05). It was suggested that BTG3 expression might contribute to gastric carcinogenesis. BTG3 overexpression might reverse the aggressive phenotypes and be employed as a potential target for gene therapy of gastric cancer.

Anti-proliferation effects of Twist gene silencing in gastric cancer SGC7901 cells

To study the role of Twist gene in gastric cancer by gene silencing, including the potential of induction of apoptosis, cell cycle arrest, and proliferation inhibition in human malignant gastric SGC7901 cells. The expression level of Twist in gastric cancer samples was measured by immunohistochemistry. The effects of Twist gene silencing were detected at both mRNA and protein levels by RT-PCR and Western blot. We also evaluated the cell proliferation and apoptosis by CCK-8 assay and flow cytometry. We determined the activity of caspase-3 and caspase-9 with a caspase activity assay kit. Cell cycle distribution was analyzed by flow cytometry. Cell migration and invasion ability was evaluated by wound scratch assay and Boyden chamber assay. Twist protein was highly expressed in gastric cancer samples. Twist gene silencing significantly induced apoptosis, cell cycle arrest at G0/G1 phase, proliferation inhibition, and reduced the ability of migration and invasion in human gastric cancer SGC7901 cells. Meanwhile, both caspase-3 and caspase-9 were activated. The Twist gene could serve as a potential molecular target for gene therapy of gastric cancer with targeted small interfering RNA.

PLCε1: A potential target of RNA interference therapy for gastric cancer

Phospholipase C epsilon 1 (PLCε1) has been recently identified as a novel potential biomarker for gastric cancer because of its critical role in inflammation and tumorigenesis. Until now, there are no further reports to investigate the feasibility of gene therapy by suppressing PLCε1 expression for gastric cancer. In this study, a small interfering RNA (shRNA) targeting PLCε1 was firstly transfected into gastric cancer cells in order to silence PLCε1 expression. Both mRNA and protein expression of PLCε1 in gastric cancer cells significantly reduced by RT-PCR and Western blotting analysis. Moreover, subsequent results revealed that PLCε1 shRNA depressed the in vitro and in vivo growth of gastric cancer cells by using MTT assay and tumor xenograft experiment. Furthermore, after PLCε1 shRNA transfection, the expression of proinflammatory molecules including tumor necrosis factor-α (TNF-α), cyclooxygenase 2 (COX-2), interleukin (IL)-6 and chemokine (C–X–C motif) ligand (CXCL)-1 were unaffected, but only chemokine (C–C motif) ligand (CCL)-2 expression decreased in the gastric cancer cells. It is implied that PLCε1 may inhibit the growth of gastric cancer cells via CCL-2 protein mediated pathway. These results suggest that PLCε1 might be an alternative molecular target for gastric cancer gene therapy.

Co-Delivery of Doxorubicin and SATB1 shRNA by Thermosensitive Magnetic Cationic Liposomes for Gastric Cancer Therapy

In previous a study, we had developed a novel thermosensitive magnetic delivery system based on liposomes. This study aimed to evaluate the efficiency of this system for the co-delivery of both drugs and genes to the same cell and its anti-tumor effects on gastric cancer. Doxorubicin (DOX) and SATB1 shRNA vector were loaded into the co-delivery system, and in vitro DOX thermosensitive release activity, targeted gene silencing efficiency, targeted cellular uptake, in vitro cytotoxicity, as well as in vivo anti-tumor activity were determined. The results showed that this co-delivery system had desirable targeted delivery efficacy, DOX thermosensitive release and SATB1 gene silencing. Moreover, the co-delivery of DOX and SATB1 shRNA exhibited enhanced activity to inhibit gastric cancer cell growth in vitro and in vivo, compared to single delivery. In conclusion, the novel thermosensitive magnetic drug and gene co-delivery system has promising application in combined chemotherapy and gene therapy for gastric cancer.

Knockdown of S100P by lentiviral-mediated RNAi promotes apoptosis and suppresses the colony-formation ability of gastric cancer cells

S100P is a putative candidate oncogene in several types of human tumors. However, expression of S100P, its potential role and its clinical significance in gastric cancer remain unclear. In the present study, S100P expression was examined by immunohistochemistry using a tissue microarray. Positive staining for S100P was noted in 77.1% of the cases while 22.9% were negative. In two gastric cancer cell lines, MGC-803 and SGC-7901, S100P expression was knocked down by a lentiviral short hairpin delivery system. The RNA interference-mediated downregulation of S100P expression markedly promoted cell apoptosis and inhibited cell colony-formation ability of the gastric cancer cells. In addition, knockdown of S100P significantly regulated the expression of 12 apoptosis-associated genes with a >1.5-fold change compared with the negative control. Among them, FOS, DDIT3 and FN1 were significantly upregulated, while FASLG, DAPK1, CTNNB1 and CASP2 were notably downregulated following S100P silencing. These results suggest that S100P acts as an oncogenic factor in gastric cancer and is a potential molecular target for gastric cancer gene therapy.

Expression and significance of Beclin-1 in vasculogenic mimicry formation of gastric cancer

To explore the effect and mechanism of autophagy specific gene Beclin-1 in gastric cancer cell SGC7901 on vasculogenic mimicry (VM) forming ability. Plasmid vectors with and without integrated shRNA were transfected respectively into SGC7901 cell line (Beclin1-inhibited group and negative control group). Simple SGC7901 cell line was used as blank group. RT-PCR and Western blot were performed to examine the expression of Beclin-1 in 3 groups. Culture was used to construct the VM model in vitro. Different VM forming ability was measured and genes (beclin-1, notch-1) expression of each group was detected before and after VM formation. Beclin-1 and notch-1 expression increased significantly in the process of VM forming. When beclin-1 was inhibited, the formation of VM was limited and VM formative genes expression decreased. As compared to cells of negative control group, those of Beclin1-inhibited group had less number of VM forming cellular tube-like construction (15.4±1.1 vs. 37.8±1.9, P<0.05), shorter length of such construction [(316.8±24.6) mm vs. (385.1±14.2) mm, P<0.05], and less crossing point (11.6±1.1 vs. 27.2±1.1, P<0.05). Beclin-1 can promote VM formation through maintaining stable expression of gastric cancer cell VM regulating genes. Beclin-1 inhibition may be a new target for gastric cancer gene therapy.

Proliferin-related protein overexpression in SGC-7901 gastric cancer cells inhibits in vitro cell growth and tumorigenesis in nude mice

As reported in the literature, the worldwide 5-year overall survival rate for patients with gastric cancer receiving surgical treatment in the progressive stage is less than 25%. Therefore, there is an urgent need for the development of novel therapeutic strategies. Our preliminary studies demonstrated that proliferin-related protein (PRP) inhibits the proliferation of TM3 Leydig testicular cells. To evaluate whether PRP has antitumor effects invitro and invivo, we stably expressed PRP in SGC-7901 gastric carcinoma cells. PRP inhibited the proliferation and cell cycle progression of SCG-7901 cells, as determined by cell growth and cell cycle assays. Transwell experiments demonstrated that PRP inhibited the cell migration and invasion of SCG-7901 cells. Western blotting demonstrated that PRP-overexpressing cells had upregulated matrix metalloproteinase 9 (MMP-9) and downregulated tissue inhibitor of metalloproteinases-1 (TIMP-1). In a xenograft tumor formation assay using nude mice, tumors formed by PRP-overexpressing cells had significantly lower weights than those formed by control cells, and the tumor inhibitory rate reached 71.9%. We demonstrated for the first time that PRP inhibits gastric carcinoma cell proliferation, motility, and tumorigenicity invivo, suggesting that PRP may become an important target for the development of gastric cancer gene therapy.

Gene therapy of gastric cancer using LIGHT-secreting human umbilical cord blood-derived mesenchymal stem cells

Mesenchymal stem cells (MSCs) have the ability to migrate into tumors and therefore are potential vehicles for the therapy of malignant diseases. In this study, we investigated the use of umbilical cord blood mesenchymal stem cells (UCB-MSCs) as carriers for a constant source of transgenic LIGHT (TNFSF14) to target tumor cells in vivo. Lentiviral vectors carrying LIGHT genes were constructed, producing viral particles with a titer of 2 × 10(8) TU/L. Fourteen days after UCB-MSCs transfected by LIGHT gene packaged lentivirus had been injected into mouse gastric cancer models, the expression levels of LIGHT mRNA and protein were detected by reverse transcription polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). Then the tumors' approximate volumes were measured. The treatment with MSC-LIGHT demonstrated a strong suppressive effect on tumor growth compared to treatment with MSC and NaCl (p < 0.001). Examination of pathological sections of the tumor tissues showed that the areas of tumor necrocis in the MSC-LIGHT group were larger than those in the MSC group. Moreover, we found that MSCs with LIGHT were able to significantly induce apoptosis of tumor cells. The expression levels of LIGHT mRNA and protein were significantly higher in the UCB-MSCs with the LIGHT gene than the levels in UCB-MSCs (p < 0.001). These results suggest that UCB-MSCs carrying the LIGHT gene have the potential to be used as effective delivery vehicles in the treatment of gastric cancers.

Construction of pGL3-hTERT-tk recombinant plasmid and effect of PEG-PEI/Fe(3)0(4) Nano-magnetic fluid-tk/GCV on proliferation of gastric cancer cells BGC823 in vitro

To construct an hTERT promoter-controlled recombinant plasmid HSV-tk, and to investigate its expression in human gastric cancer cells BGC823 and its effect on proliferation of gastric cancer cells BGC823 in vitro. Recombinant plasmid pGL3-hTERT-tk and the corresponding reporter plasmid pGL3-hTERT-tk-Luc(+) were constructed by gene engineering. The recombinant plasmids were then transfected into gastric cancer cells BGC823 via PEG-PEI/Fe(3)0(4) magnetic nano-particles. Fluorescence microscope was used to observe the changes of cell morphology and the transfection efficiency. The expression of the target gene in gastric cancer cells BGC823 was detected by immunohistochemistry. MTT assay was used to evaluate the effect of HSV-tk on the proliferation of BGC823 cells. Normal hepatic cells L02 were used as controls in all the experiments. Recombinant plasmid pGL3-hTERT-tk was successfully constructed, and the length was 1100 bp. pGL3-control-tk-Luc(+), pGL3-basic-tk-Luc(+) and pGL3-hTERT-tk-Luc(+) all could effectively transfect BGC823 cells with high telomerase activity, with the transfection rate being(28.1±2.3)%. Immunohistochemistry study showed significant expression of HSV-tk gene in the cytoplasm of BGC823 cells. MTT showed that 4 days after transfection of pGL3-hTERT-tk, the proliferation of BGC823 was inhibited, and the A570 value was(0.254±0.011), significantly lower than that of L02 cells(0.322±0.013) and that of BGC823 transfected by pGL3-basic-tk (0.357±0.014)(all P<0.05). Magnetic nano-particles can transfect pGL3-hTERT-tk into BGC823 cells and the expression is achieved. PEG-PEI/Fe(3)0(4) magnetic nano-particles can significantly inhibit the proliferation of BGC823 and may become a potential biological agent for gene therapy of gastric cancer.

Characterization of Interaction Proteins for Gastric Cancer Related Novel Protein RKIP*

Gastric cancer(GC) seriously impacts on human health with high incidence and mortality rate in the world.Raf kinase inhibitor protein(RKIP) that was discovered in our previous studies is down-regulated in GC,which is associated with the occurrence,differentiation,invasion,and metastasis of GC.In order to investigate the molecular mechanisms and biological functions of RKIP in the occurrence and metastasis of GC,the fusion expression plasmid pcDNA3.1-RKIP-3xFLAG was transiently transfected into SGC7901 cells with liposome-mediated approach,the RKIP fusion proteins were purified with 3xFLAG tag affinity chromatography,and the RKIP-interacted proteins were identified with electrospray ionization-Quadrupole-time of flight(ESI-Q-TOF) tandem mass spectrometry(MS/MS).A total of 66 RKIP-interacted proteins were MS/MS-identified.The MS/MS-characterized components of the existing interaction complex(RKIP and 14-3-3) were confirmed with Western blotting in combination with co-immunoprecipitation.It is the first time to discover the interaction of RKIP with 14-3-3.This preliminary study on the molecular mechanisms that how RKIP inhibits the occurrence and development of GC provides novel clues for the early-stage diagnosis,prognosis monitoring,and targeted gene therapy of GC.

Development of an MRI-visible nonviral vector for siRNA delivery targeting gastric cancer

An antibody-directed nonviral vector, polyethylene glycol-grafted polyethylenimine functionalized with superparamagnetic iron oxide nanoparticles and a gastric cancer-associated CD44v6 single-chain variable fragment (scFvCD44v6,-PEG-g-PEI-SPION), was constructed as a gastric cancer-targeting and magnetic resonance imaging (MRI)-visible nanocarrier for small interfering RNA (siRNA) delivery. Biophysical characterization of PEG-g-PEI-SPION and scFvCD44v6-PEG-g-PEI-SPION was carried out, including siRNA condensation capacity, cell viability, and transfection efficiency. Both the targeting and nontargeting nanocarriers were effective for transferring siRNA in vitro. The cellular uptake and distribution of nanoparticles complexed with siRNA was analyzed by fluorescence imaging and immunofluorescent staining. Moreover, the gastric cancer-targeting effect was verified in vivo by MRI and histology analysis. These results indicate that scFvCD44v6-PEG-g-PEI-SPION is a promising nonviral vector for gastric cancer gene therapy and diagnosis.

Survivin siRNA Inhibits Gastric Cancer in Nude Mice

The objective of the study was to evaluate the expression of survivin, cell proliferation, and apoptosis in survivin-specific siRNA-transfected human gastric cancer cell line MGC-803. For this purpose, the target gene fragments were cloned into pSilencer3.1-Hl neo vector. Recombinant eukaryotic expression vector, pSilencer3.1-SVV was successfully constructed and then the recombinant vector was transfected into gastric cancer MGC-803 cells. The mRNA expression of survivin was determined by reverse-transcriptase polymerase chain reaction (RT-PCR). Survivin protein expression was detected by Western blot. Cell cycle distribution and apoptosis were determined by flow cytometry. Our data regarding RT-PCR and Western blot showed that pSilencer3.1-SVV vector could knockdown the expression of survivin mRNA and protein. In contrast with the control group, the apoptotic index of MGC-803 cells increased remarkably. Survivin-specific siRNA caused cells accumulation in the G2/M phase and the number of cells in the G0/G1 phase decreased after transfection. It was, therefore, concluded that the siRNA targeting survivin gene could inhibit the proliferation of gastric cancer cells and induce apoptosis. The use of survivin siRNA may provide a novel approach for gene therapy of gastric cancer.