Effect and mechanism of the Twist gene on invasion and metastasis of gastric carcinoma cells

AIM: To study the effect of the transfected Twist gene on invasion and metastasis of gastric carcinoma cells and the possible mechanisms involved. METHODS: Human gastric carcinoma MKN28 cells were stably transfected with Twist sense plasmid, and MKN45 cells were stably transfected with Twist antisense plasmid using the lipofectamine transfection technique. RT-PCR, Western blotting, EMSA, gelatin zymography assay, and in vitro invasion and migration assays were performed. Nude mice metastasis models were established by the abdominal cavity transfer method. RESULTS: Cell models (TwistS-MKN28) that steadily expressed high Twist protein were obtained. Compared with MKN28 and pcDNA3-MKN28 cells, adherence, migration and invasion ability of TwistS -MKN28 cells were clearly raised. The number of cancer nodules was increased significantly in the abdominal cavity and liver of nude mice inoculated with TwistS-MKN28 cells. Overexpression of Twist in MKN28 cells increased Tcf-4/ Lef DNA binding activity, and promoted expression of Tcf-4’s downstream target genes cyclin D1 and MMP-2. However, suppression of Twist (TwistAS-MKN45) inhibited MKN45 cell invasion and the expression of cyclin D1 was reduced. The activity of MMP-2 was also decreased. CONCLUSION: These results indicate that Twist promotes gastric cancer cell migration, invasion and metastasis, and Twist may play an important role in Wnt/ Tcf-4 signaling.

Effect of ligand troglitazone on peroxisome proliferator-activated receptor γ expression and cellular growth in human colon cancer cells

AIM: To investigate the effect of troglitazone on pe- roxisome proliferator-activated receptor γ (PPARγ) expression and cellular growth in human colon cancer HCT-116 and HCT-15 cells and to explore the related molecular mechanism. METHODS: Human colon cancer HCT-116 and HCT-15 cells cultured in vitro were treated with troglitazone. Reverse transcription-polymerase chain reaction (RT-PCR) and Western blot were employed to detect the effect of troglitazone on PPARγ expression. The proliferative activity was determined by MTT assay, cell cycle and apoptosis were detected by ? ow cytometry. Apoptosis- related genes, cell cycle regulatory genes and p53 were examined by RT-PCR and Western blot respectively. RESULTS: The expression of PPARγ in colon cancer HCT-116 and HCT-15 cells was up-regulated by troglitazone. Troglitazone inhibited proliferation, induced apoptosis and cell cycle G1 arrest in colon cancer cells. Troglitazone induced p53 expression in HCT-116 cells, but not in HCT-15 cells. The down-regulation of survivin and bcl-2 was found in both cell lines and up-regulation of bax was found only in HCT-116 cells, being consistent with growth inhibition in HCT-116 cells but not in HCT-15 cells. Troglitazone increased expression of p21WAF1/CIP1 (p21), p27KIP1 (p27) and reduced cyclin D1 in HCT-116 cells while only a minor decrease of cyclin D1 was found in HCT-15 cells. CONCLUSION: Troglitazone is an inductor of PPARγin colon cancer cells and inhibits PPARγ-dependently proliferation, which may attribute to cell cycle G1 arrest and apoptosis in colon cancer cells. Troglitazone may induce p53-independent apoptosis and p53- dependent expression of p21 and p27. Depending on cell background, different activation pathways may exist in colon cancer cells.

Hydrogen peroxide functions as a secondary messenger for brassinosteroids-induced CO_2 assimilation and carbohydrate metabolism in Cucumis sativus

Brassinosteroids(BRs) are potent regulators of photosynthesis and crop yield in agricultural crops;however,the mechanism by which BRs increase photosynthesis is not fully understood.Here,we show that foliar application of 24-epibrassinolide(EBR) resulted in increases in CO 2 assimilation,hydrogen peroxide(H 2 O 2) accumulation,and leaf area in cucumber.H 2 O 2 treatment induced increases in CO 2 assimilation whilst inhibition of the H 2 O 2 accumulation by its generation inhibitor or scavenger completely abolished EBR-induced CO 2 assimilation.Increases of light harvesting due to larger leaf areas in EBR-and H 2 O 2-treated plants were accompanied by increases in the photochemical efficiency of photosystem II(Φ PSII) and photochemical quenching coefficient(q P).EBR and H 2 O 2 both activated carboxylation efficiency of ribulose-1,5-bisphosphate oxygenase/carboxylase(Rubisco) from analysis of CO 2 response curve and in vitro measurement of Rubisco activities.Moreover,EBR and H 2 O 2 increased contents of total soluble sugar,sucrose,hexose,and starch,followed by enhanced activities of sugar metabolism such as sucrose phosphate synthase,sucrose synthase,and invertase.Interestingly,expression of transcripts of enzymes involved in starch and sugar utilization were inhibited by EBR and H 2 O 2.However,the effects of EBR on carbohydrate metabolisms were reversed by the H 2 O 2 generation inhibitor diphenyleneodonium(DPI) or scavenger dimethylthiourea(DMTU) pretreatment.All of these results indicate that H 2 O 2 functions as a secondary messenger for EBR-induced CO 2 assimilation and carbohydrate metabolism in cucumber plants.Our study confirms that H 2 O 2 mediates the regulation of photosynthesis by BRs and suggests that EBR and H 2 O 2 regulate Calvin cycle and sugar metabolism via redox signaling and thus increase the photosynthetic potential and yield of crops.

Effects of nitrogen form on growth,CO_2 assimilation,chlorophyll fluorescence,and photosynthetic electron allocation in cucumber and rice plants

Cucumber and rice plants with varying ammonium (NH4+) sensitivities were used to examine the effects of different nitrogen (N) sources on gas exchange, chlorophyll (Chl) fluorescence quenching, and photosynthetic electron allocation. Compared to nitrate (NO3-)-grown plants, cucumber plants grown under NH4+-nutrition showed decreased plant growth, net photosynthetic rate, stomatal conductance, intercellular carbon dioxide (CO2) level, transpiration rate, maximum photochemical efficiency of photosystem II, and O2-independent alternative electron flux, and increased O2-dependent alternative electron flux. However, the N source had little effect on gas exchange, Chl a fluorescence parameters, and photosynthetic electron allocation in rice plants, except that NH4+-grown plants had a higher O2-independent alternative electron flux than NO3--grown plants. NO3- reduction activity was rarely detected in leaves of NH4+-grown cucumber plants, but was high in NH4+-grown rice plants. These results demonstrate that significant amounts of photosynthetic electron transport were coupled to NO3- assimilation, an effect more significant in NO3-- grown plants than in NH4+-grown plants. Meanwhile, NH4+-tolerant plants exhibited a higher demand for the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) for NO3- reduction, regardless of the N form supplied, while NH4+-sensitive plants had a high water-water cycle activity when NH4+ was supplied as the sole N source.

Image Inpainting Based on Structural Tensor Edge Intensity Model

In the exemplar-based image inpainting approach,there are usually two major problems:the unreasonable calculation of priority and only considering the color features in the patch lookup strategy.In this paper,we propose an image inpainting approach based on the structural tensor edge intensity model.First,we use the progressive scanning inpainting method to avoid the image filling order being affected by the priority function.Then,we use the edge intensity model to build the patches similarity function for correctly identifying the local image structure.Finally,the balance operator is used to restrict the excessive propagation of structural information to ensure the correct structural reconstruction.The experimental results show that the our approach is comparable and even superior to some state-of-the-art inpainting algorithms.