Abstract: In this paper the influence of HZ08 on multidrug resistance and possible mechanism were explored.It was found that the IC₅₀of adriamycin in the presence of 10 μmol/L HZ08 in clinical sample cells was 0.60 μmol/L,while the IC₅₀in K562/A02 cells was 0.83 μmol/L by MTT.The reversal folds of MDR were 27.87 and 20.49,respectively.For further mechanism study of HZ08,the expression level of glucosylceramide synthase (GCS) protein in K562/A02 and resistant cells from clinical samples were analyzed by Western blot,while the mRNA of MDR1 was detected by real-time fluorescent quantitative polymerase chain reaction (FQ-RT-PCR).Combined with adriamycin,all concentrations (15,20,25 μmol/L) of HZ08 decreased the expression of GCS protein.In addition,compared with the group of treatment with adriamycin alone,combined treatment of HZ08 and adriamycin decreased the expression of MDR1 significantly (P<0.01).Therefore,HZ08 possibly reverses multidrug resistance by its joint action with adriamycin on GCS and MDR1 in both cell line and clinical sample cells.