Retraction Note: Enhanced suppression of tumor growth using a combination of NK4 plasmid DNA-PEG engrafted cationized dextran complex and ultrasound irradiation.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Effects of an antimitotic drug on mechanical behaviours of the cytoskeleton in distinct grades of colon cancer cells.

Biomechanical behaviours of cells change during cancer progression due to alterations in the main cytoskeletal proteins. Microtubules play a vital role in mitosis and in supporting the integrity of the cell due to their ability to withstand high compressive loads. Accordingly, microtubule-targeting agents (MTAs) have become one of the most promising classes of drugs in cancer therapy. This study evaluated changes in visco-elastic parameters induced by an appropriate concentration of an antimitotic drug in two different grades of colon cancer cells. Actin microfilaments and microtubules contents in the cells were evaluated by Western blot analysis and fluorescence intensity calculation. Micropipette aspiration experiments showed that the MTA had distinct mechanical effects on different cell lines. The more aggressive the cells, the greater the reduction in elasticity and viscosity. Invasive cells had a higher initial instantaneous Young's modulus than primary cells, but this reduced to approximately one half of the values for primary cells after 48 h of drug treatment. A considerable association was seen between the changes in mechanical properties and the microtubule to F-actin microfilament content ratio, which decreased with MTA treatment.

Mechanical properties of cancer cytoskeleton depend on actin filaments to microtubules content: investigating different grades of colon cancer cell lines.

Biomechanical properties of cancer cells have been proposed as promising biomarkers to investigate cancer progression. Cytoskeletal reorganization alters these characteristics in different grades of cancer cells. In the present study based on the micropipette aspiration method, whole body evaluation for two different colon cancer cells was performed to determine viscoelastic parameters of the cells. A finite element model was developed for verification of experiments and predicting some behaviors of cells. Western blot analysis and fluorescence intensity for actin microfilaments and microtubules were performed to measure cell content of the proteins. It was illustrated that the proportion of microtubules and actin microfilaments is different in grade I and grade IV colon cancer cells in a manner that microtubules attain an effectual role in progressive reorganization of cytoskeleton in transition from nonaggressive to malignant phenotypes in cancer cells. Furthermore, it was concluded that larger instantaneous Young's modulus value for high grade cells is related to the existence of extensively build-up actin networks at the cell cortex. Based on the cell mechanics results, a simple parameter is suggested for sorting different grades of colon cancer cells.

Dynamics of PEGylated-dextran-spermine nanoparticles for gene delivery to leukemic cells.

Leukemic cells are hard-to-transfect cell lines. Many transfection reagents which can provide high gene transfer efficiency in common adherent cell lines are not effective to transfect established blood cell lines or primary leukemic cells. This study aims to examine a new class of cationic polymer non-viral vector, PEGylated-dextran-spermine (PEG-D-SPM), to determine its ability to transfect the leukemic cells. Here, the optimal conditions of the complex preparation (PEG-D-SPM/plasmid DNA (pDNA)) were examined. Different weight-mixing (w/w) ratios of PEG-D-SPM/pDNA complex were prepared to obtain an ideal mixing ratio to protect encapsulated pDNA from DNase degradation and to determine the optimal transfection efficiency of the complex. Strong complexation between polymer and pDNA in agarose gel electrophoresis and protection of pDNA from DNase were detected at ratios from 25 to 15. Highest gene expression was detected at w/w ratio of 18 in HL60 and K562 cells. However, gene expression from both leukemic cell lines was lower than the control MCF-7 cells. The cytotoxicity of PEG-D-SPM/pDNA complex at the most optimal mixing ratios was tested in HL60 and K562 cells using MTS assay and the results showed that the PEG-D-SPM/pDNA complex had no cytotoxic effect on these cell lines. Spherical shape and nano-nature of PEG-D-SPM/pDNA complex at ratio 18 was observed using transmission electron microscopy. As PEG-D-SPM showed modest transfection efficiency in the leukemic cell lines, we conclude that further work is needed to improve the delivery efficiency of the PEG-D-SPM.

Enhanced suppression of tumor growth using a combination of NK4 plasmid DNA-PEG engrafted cationized dextran complex and ultrasound irradiation.

This investigation aims to determine experimentally whether or not ultrasound (US) irradiation is effective in enhancing the in vivo gene expression of NK4 plasmid DNA and suppressing tumor growth. NK4, composed of the NH2-terminal hairpin and subsequent four-kringle domains of hepatocyte growth factor (HGF), acts as an HGF-antagonist and angiogenesis inhibitor. Dextran was cationized by introducing spermine to the hydroxyl groups to allow for polyionic complexation with NK4 plasmid DNA. The cationized dextran was additionally modified with poly(ethylene glycol) (PEG) molecules giving PEG engrafted cationized dextran. Significant suppression of tumor growth was observed when PEG engrafted cationized dextran-NK4 plasmid DNA complexes were intravenously injected into mice carrying a subcutaneous Lewis lung carcinoma tumor mass with subsequent US irradiation when compared with the cationized dextran-NK4 plasmid DNA complex and naked NK4 plasmid DNA with or without US irradiation. We conclude that complexation with PEG-engrafted cationized dextran in combination with US irradiation is a promising way to target the NK4 plasmid DNA to the tumor for gene expression.

Dextran-spermine polycation: an efficient nonviral vector for in vitro and in vivo gene transfection.

Dextran-spermine cationic polysaccharide was prepared by means of reductive amination between oxidized dextran and the natural oligoamine spermine. The formed Schiff-base imine-based conjugate was reduced with borohydride to obtain the stable amine-based conjugate. The transfection efficiency of the synthetic dextran-spermine was assessed in vitro on HEK293 and NIH3T3 cell lines and found to be as high as the DOTAP/Chol 1/1 lipid-based transfection reagent. Modification of the dextran-spermine polycation with polyethylene glycol resulted in high transfection yield in serum-rich medium. Intramuscular injection in mice of dextran-spermine-pSV-LacZ complex induced high local gene expression compared to low expression of the naked DNA. Intravenous injection of a dispersion of the dextran-spermine-pSV-LacZ complex resulted with no expression in all examined organs. When the partially PEGylated dextran-spermine-pSV-LacZ complex was intravenously applied, a high gene expression was detected mainly in the liver. Preliminary targeting studies indicated that the PEGylated dextran-spermine-pSV-LacZ complex bound to galactose receptor of liver parenchymal cells rather than the mannose receptor of liver nonparenchymal cells. This work offers a new biodegradable polycation based on natural components, which is capable of transfecting cells and tissues in vitro and in vivo.