Transformation of mammalian cell by iontophoretic pricking or iontophoretic microinjection

Thymidine kinase negative mouse (LATK-) and hamster (BHKTK-) cells were transfected with a recombinant plasmid (pTK1) carrying the thymidine kinase gene of HSV-1 by iontophoretic pricking or iontophoretic microinjection techniques. Transfection frequencies were measured using short term survival and long term transformation assays and were found to be at the level of 10 to 15% and 1 to 2% respectively for mouse or hamster cells transfected with pTK1. The presence of covalently linked transcriptional enhancers from SV40 or Moloney MSV increased long term transformation frequencies approximately 10-fold. Transfection by iontophoretic pricking of non-tumorigenic mouse (NIH3T3) or hamster (BHKC13) cells with a recombinant (pAGT1) carrying the human T24 Ha-ras1 oncogene and the bacterial aminoglycoside phosphotransferase (aph) gene as a selectable marker resulted in transformation of these cells. Southern blot hybridization analyses demonstrated the presence of circular, integrated or rearranged donor DNA molecules in the transformed cells. These gene transfer techniques and iontophoretic pricking in particular should be useful for the transfection of a variety of cell lines and markers.