Enhancement of DNA transfection efficiency by heat treatment of cultured mammalian cells

The expression of genes introduced into various mammalian cell lines was enhanced by raising the temperature of the cells to 42°C for a few hours after DNA transfection. This heat treatment resulted in an up to 10-fold increase in the frequency of the cells that transiently expressed a foreign gene such as that of β-galactosidase, whereas it had only a limited enhancing effect on the development of stable transformants. By immunotitration analysis, it was confirmed that the enhanced expression of β-galactosidase activity correlated well with the increase of the enzyme protein. This procedure may have an applicability for augmenting the frequency of transient gene expression in many cell types.