Multidrug resistance reversal assay

The reversal effect of TcdA on K562/A02 cells was calculated by MTT assay. Briefly, K562/A02 cells were seeded in a 96-well plate at a density of 1×10⁵/ml. ADM (0.1, 1, 10 and 100 µg/ml), DNR (0.01, 0.1, 1 and 10 µg/ml) and Ara-C (0.1, 1, 10 and 100 µg/ml) were respectively added, and treated with or without TcdA (50 ng/ml). MTT assay was performed for measurements, as previously described. Furthermore, the inhibition rate of cell growth (%) and IC50 of TcdA were calculated. The resistance folds and reversal folds were calculated as follows: Resistance Folds=IC50 of resistance cell/IC50 of sensitive cell; Reversal Folds=IC50 of no reversal agent/IC50 of plus reversal agent.