After removal of drug-containing medium, samples were taken every 8 hr during 72 hr. For each time, cells were infected with 1 ml of 0.45 μm filtered TG 5391 packaging cells supernatant in the presence of 8 μg/ml of polybrene. Then, HSV-tk gene was used during optimal

period determined with the reporter gene for each cell line. During this period, cells were infected with 1 ml of 0.45 μm filtered TG 9344 packaging cells supernatant in the presence of 8 μg/ml of polybrene FDA-approved Drug Library cell assay at various time points after MTX removal. For each time point, appropriate controls were performed. Transgene expression was determined 48 hr after transduction. Transgene expression assay For detection of β-galactosidase activity, cells transduced by TG 5391 were fixed for 15 min at 37°C with 0.5% of glutaraldehyde, then washed two times with PBS and stained AZD1208 ic50 with X-gal for cytochemical analysis, as previously described. The quantitative detection of β-gal expression was performed with the

fluorescein-di-β-D-galactopyranoside (FDG) (Sigma) by flow cytometry [28]. Cells were harvested (trypsin-EDTA), washed and resuspended at a concentration of 5.105/ml in 25 μl of PBS containing 2% fetal calf serum, at 37°C for 10 min. The β-galactosidase activity was obtained by cell incubation in 25 μl of 2 mM FDG solution for one min at 37°C, then for one hour at 0°C, in 1 ml of PBS. The fluorescence was analyzed by flow cytometry. Non-transduced cells formed the control group. For HSV-TK expression analysis, cells transduced by TG 9344, cultured on slides (Labtek II-Nunc), were fixed for 15 min at 4°C with 4% paraformaldehyde and incubated with

PBS containing 0.2% serum bovine albumin (SAB) and 0.1% saponin for 5 min. Cells were incubated with anti-HSV-TK mouse monoclonal antibody 4C8 (W. Summers, Yale University, USA) 1/50, for 30 min at room temperature. After washing in PBS, cells were incubated for 10 min in a secondary antibody solution of goat anti-mouse coupled to biotin (LSAB 2 System Peroxydase, Dako). Cells were washed in PBS and incubated 10 min with streptavidin-peroxydase. The revelation was achieved by incubation for 5 min with 3-3′ diaminobenzidine (DAB) leading to cytoplasmic brown precipitates. Teicoplanin Cells were counterstained with hematoxylin. For flow cytometry analysis, cells were harvested, washed in PBS and fixed with 4% paraformaldehyde for 15 min at 4°C in PBS. Cells were washed in incubation buffer (0.2% SAB, 0.1% saponin in PBS containing 0.2% of sodium azide) then incubated in 200 μl of anti-HSV-TK monoclonal antibody 4C8, diluted to 1/50 in incubation buffer for 30 min at room temperature. Cells were washed three times with PBS. The pellet was resuspended 30 min at room temperature, in 200 μl of goat anti-mouse antibody coupled to FITC, diluted to 1/100 in incubation buffer. Cells were washed and resuspended in 1 ml of PBS for flow cytometry analysis.