Verapamil enhances the efficiency of DNA-mediated gene transfer in mammalian cells.

Treatment of Ltk- cells with the calcium antagonists, verapamil and diltiazem, but not nifedipine, causes a 3-fold enhancement of the frequency of transfer of the cloned gene for herpes simplex virus thymidine kinase (HSV-tk). The frequency of phenotypic expression of the HSV-tk DNA was 20 to 34 times higher than that of genotypic transformation. Phenotypic expression was also 2.3 to 2.6 times increased when 20 micrograms/ml of verapamil was present during calcium phosphate-mediated DNA transfection.