Amphotericin B-induced sensitivity to actinomycin D in drug-resistant Hela cells.

HeLa cells, which were selected for resistance to actinomycin D on the basis of decreaded penetration of the antibiotic into the cells, were treated with nontoxic concentrations of the polyene antibiotic amphotericin B. In the presence of amphotericin B, the cells became sensitive to the effects of actinomycin D, as demonstrated by loss of cell viability, typical morphological changes, and effects on the pattern of RNA synthesis. Furthermore, we were able to demonstrate that amphotericin B increased the amount of (3H)actinomycin D incorporated into HeLa cells as determined by both radioactive counts and radioautography. Amphotericin B might be useful in overcoming the resistance is based on decreased entry of the agents into cells.