Mild and transient heat shock enhances DNA integration following lipofection of recombinant plasmids in 4T1 cells

Abstract

Cancer cells having stably integrated genes encoding tumor-associated antigens could be utilized as a vaccine, <em>in-vitro</em> stimulators of antigen-primed T-cells, and target for cytotoxicity assay, <em>etc</em>. Lipofection is a simple and safer technique for stable transfection of plasmid DNA. However, the poor rate of genomic integration has limited its application. In the current study, the effect of mild and transient heat shock following lipofection on the improvement of genomic integration was evaluated. The cDNA fragments encoding chicken MMP-11peptide (V³²-K³⁶⁵) and the immunoglobulin-like domain 2 of chicken VEGFR-2 were cloned separately into pcDNA3.1 vector. Lipofection was carried out using Lipofectamine^® 2000 (Life Technologies, USA) in 4T1 cells followed by a heat shock at 42°C for 10 min. Transfected cells were selected for a period of four weeks against 500 µg/mL G418 in RPMI 1640 media supplemented with 10% fetal bovine serum. Distinct G418-resistant colonies appeared after 14 days of selection. Heat shock significantly (<em>P</em> <0.05) increased the number of viable colonies following antibiotic selection. The immunofluorescent study confirmed the stable integration of the target DNAs into the cells. It is concluded that mild and brief heat shock following lipofection improves the stable integration of recombinant pcDNA3.1 plasmids into 4T1 cells.