DIFFERENTIAL-EFFECTS OF THE PHORBOL ESTER TPA ON DNA-MEDIATED TRANSFECTION IN A VARIETY OF CELL-LINES

The efficiency of stable gene transfer and expression in NIH3T3 cells has been shown to be significantly enhanced by a brief treatment with the phorbol ester tetradecanoylphorbol 12,13-acetate (TPA) immediately following calcium-phosphate transfection. Several lines of evidence indicated that this effect was mediated through protein kinase C activation. These studies were expanded to determine whether this was a consistent and widespread phenomenon among other cell lines. The efficiency of transfection in two other established fibroblast lines, LMtk- and 2A3 3T3, was unaffected by TPA treatment, and primary human foreskin fibroblasts were similarly unaffected. Transfection was inhibited by TPA treatment in the transformed cell lines EJ and HeLa. Protein kinase C enzyme assays indicated that TPA causes a translocation of the enzyme from cytosol to membrane in both NIH3T3 and EJ cells, suggesting that the PKC translocation event does not account for the TPA effect on transfection. The TPA-mediated inhibition of transfection in EJ cells was not blocked by sphingosine, suggesting that this phenomenon is unrelated to PKC activation. The results suggest that TPA treatment may either enhance, inhibit, or have no effect on transfection, depending on the cell line.