Trypan blue staining was performed as the standard protocol. We used 0.4% Trypan blue to stain cells and counted the viable cells at each condition. All of the experiments were performed in duplicate for MTT assay. The MTT assays were performed as described by Gangzeng et al.14 Briefly, after electroporation in each condition, each 5×103 cells was seeded into a 96 well plate. After 24 h, Inhibitors,research,lifescience,medical 10% vol/vol of 5 mg/ml 3-(4, 5

dimethyl thiazol- 2-yl)-2, 5 diphenyl tetrazolium bromide (MTT, sigma, US) diluted in PBS was added into each well. The absorbance of this colored solution was quantified by ELLSA in 570 nm. Small Interfering RNA Transfection After electroporation and evaluation of the viability of the cells using MTT assay and Trypan blue staining, we chose the best electroporation condition (220 volt, exponential decay and 975 µF capacity). Then, siRNA transfection Inhibitors,research,lifescience,medical was performed in this condition. Small interfering RNA directed against DNMT1, and a non silencing siRNA were obtained from Eurofins MWG operon, Germany. The siRNA targeting DNMT1 Inhibitors,research,lifescience,medical was designed by Elbashir et al.15 The siRNA sense sequence was 5’-CGGUGCUCAUGCUUACAACTT-3’ and antisense sequence was 5’-GUUGUAAGCAU GAGCACCGTT-3’.

A non–silencing siRNA was used as a negative control. Its siRNA sequence was 5’-UUCUCCGAACGUGUCACGUdTdT-3’. Three concentrations of DNMT1 siRNA (10, 5 and 2 nmol) and non-silencing siRNA were each diluted in 50 µL DW, and was used for electroporation. Seventy two h after siRNA transfection cells were harvested to evaluate the DNMT1 protein. Western Blot Analysis The MDA-MB 468 cells treated with siRNA were used for total cell lysate preparation. The cells were washed with Inhibitors,research,lifescience,medical PBS solubilized in a lysis buffer www.selleckchem.com/products/Trichostatin-A.html containing Inhibitors,research,lifescience,medical 10 mM Tris-Hcl pH 7.4, 0.825 M NaCl and 1% ND-40, and then rotated in 4˚C for 15 min. Lysate was sonicated and cleared by centrifugation. Total protein was determined by Bradford method. Fifty µg of proteins of the transfected cells and control cells were mixed with lammali lysis buffer and resolved by 8% SDS-PAGE analysis. The gel

Oxymatrine was transferred onto nitrocellulose membrane following the standard protocol.16 The primary antibodies including anti-DNMT1 (Abcam, Canada) and anti-actin (Abcam, Canada) were used for immunoblotting. A horseredish peroxidase conjugated anti-mouse secondary Ab (Abcam, Canada) and chemiluminescenc substrate (ECL, Amersham Bioscience, UK) were used to determine the immuno labeled bands. All the experiments were performed at least three times. Results Optimal Condition for Electroporation of MDA-MB-468 Cells Cell type-specific effects of different pulse parameters were assessed. Square wave and exponential decay pulses were applied to MDA-MB-468 cells using the Gene pulser Xcell electroporation system.