Effect of PDMP, a Glucosylceramide Synthase Inhibitor, On Resistance to Daunorubicin in Human Leukemia Cell Line K562/A02.

Previous studies showed inhibition of glucosylceramide synthase (GCS) increased sensitivity to doxorubicin toxicity in multidrug-resistant cancer cells. This study was purposed to investigate the reversal effect of D, L-threo-1-phenyl-2- -decanoylamino-3-morpholino-1-propanol (PDMP), a glucosylceramide synthase inhibitor, on daunorubicin (DNR) resistance in K562/A02 cells.

The cytotoxicity and reversal effect were analyzed by MTT method. Flow cytometry was used to test DNR accumulation and apoptosis percentage. The expressions of GCS and mdr1 genes of K562 and K562/A02 cells were measured by RT-PCR and Western blot.

The inhibition rates of PDMP (≤20μmol/l) on the proliferation of K562 and K562/A02 cells were below 10%. The IC₅₀ of DNR for K562 and K562/A02 cells were 0.23±0.02μg/ml and 7.15±0.24μg/ml, respectively. PDMP increased sensitivity of K562/A02 cells to DNR toxicity in a dose-dependent manner (the IC₅₀ was decreased to 2.76±0.25μg/ml by 20μM PDMP and to 4.23±0.08μg/ml by 10μM PDMP), but it had no effect on K562 cells. Both 10μM and 20μM PDMP increased DNR induced apoptosis compared with DNR alone (the apoptosis percentage were 8.93%±0.83%, 18.33% ± 0.86%and 5.43% ± 0.70% respectively). The mean fluorescence intensity of DNR in K562/A02 cells increased from 1550 treated by DNR alone to 1631 incubating with 10μM PDMP and higher to 1998 by 20μM PDMP. The expression of GCS gene was down-regulated by 20μM PDMP and blocking GCS also showed a dramatic decrease in mdr1 expression.

PDMP can increase the sensitivity to DNR toxicity in K562/A02 cells by enhancing cell apoptosis rate, intracellular DNR concentration, and down-regulating expressions of both GCS and mdr1 genes.

No relevant conflicts of interest to declare.