A new transfection method of mouse FM3A mammary carcinoma cells with plasmid DNA.

High-frequency transfection of mouse FM3A cells with plasmid pSV2neo DNA was achieved by incubation of the cells with DNA plus polybrene for 6 hours followed by an osmotic shock with hypertonic NaCl solution. When incubated for 20 min at 34 degrees C, FM3A cells showed resistance to the osmolarity change from 0.1 to 9.0% NaCl in the medium. Within this range of NaCl concentration, 5-7% gave the highest efficiency of transfection. Both linear and circular forms of plasmid DNA produced transformants with equal efficiency. This method was simple, reproducible and carrier DNA was not required. The efficiency was about 100 times higher than that of the widely used method with DNA-calcium phosphate precipitates. Transformed cells were stable and different numbers of plasmid DNA copies were detected with different restriction sites.