Impact of Medium pH on DOX Toxicity toward HeLa and A498 Cell Lines

The influence of the pH of the multicomponent cell medium on theperformance of doxorubicin (DOX), an anticancer drug, was studied on the examplesof cervical (HeLa) and kidney (A498) cancer cell lines. The change of pH of the cellmedium to more acidic led to a decrease of DOX toxicity on both cell lines due to thechange of drug permeability across the cell membrane as a result of drug protonation.3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) studies andlactate dehydrogenase (LDH) release tests have shown low toxicity of the drug,especially in the case of A498 cells, which are characterized by an extremely highglycolytic metabolism. The behavior was ascribed primarily to the increased protonconcentration in the peripheral blood follicle in the presence of products of the acidicglycolytic metabolism. It is not observed in the measurements performed incommercially available media since they usually have a neutral pH. In earlier reportson kidney cancer, several mechanisms were discussed, including the metabolism ofDOX to its less toxic derivative, doxorubicinol, overexpression of ATP binding cassette subfamily B member 1 (ABCB1)transporters, that remove DOX from the inside of cells; however, there was no focus on the simple but very important contributionof drug protonation described in the present study. Drug pH-dependent equilibria in the cell medium should be considered sincechanges in the drug form may be an additional reason for multidrug resistance.