Reversal of lomerizine on multidrug resistance in human leukemia cell line K562/ADM

AIM: To investigate the efficacy of lomerizine on multidrug resistance (MDR) reversal and its mechanism. METHODS: Cytotoxicity of daunomycin (DNR) on K562/ADM was assessed by MTT assay in the presence of lomerizine. Fluorescence of P-glycoprotein (P-gp) substrate rhodamine123 (Rh123) in K562/ADM was measured by fluorescence spectrophotometry and flow cytometry. RESULTS: Lomerizine could significantly increase the chemosensitivity of K562/ADM to DNR and intracellular content of Rh123. No effect was found in K562 cells. CONCLUSION: Lomerizine shows significant inhibition on the activity of P-gp in K562/ADM, increases intracellular accumulation of P-gp substrates, and enhances cytotoxicity of other anticancer drugs.