[Embelin Reverses the Multi-drug Resistance of K562/D to Daunorubicin Independently of P-gp and MDR1 mRNA].
To investigate the mechanism of reversing drug resistance of K562/D cells to daunorubicin by Embelin and its relationship with P-gp and MDR1 mRNA. MTT assay was used to detect and compare the cell proliferation rate of treating with DNR alone and DNR combined with Embelin. Flow cytometry with Annexin V-FITC/PI double staining was used to detect cell apoptosis rate, Western blot was used to detect the expression of XIAP,Caspase-3,BCL-2,BAX and P-gp of K562/D cells after using DNR alone and combining with Embelin. Quantitative real-time PCR was used to detect XIAP,BCL-2,BAX and MDR1 mRNA. The IC50 of K562 and K562/D cells treated with DNR for 24 h were 2.177 µg/ml and 69.43 µg/ml, respectively. The drug-resistance index was 31.89; The proliferation inhibition rates of K562/D cells treated with Embelin of 3, 10, 30, 100 and 300 µg/ml for 24 h were 2.70%±1.08%, 10.92%±4.89%, 28.13%±2.09%, 36.56%±3.24% and 43.59%±1.16%; The proliferation inhibition rates of K562/D cells treated with DNR of 0.1, 1, 10 and 100 µg/ml combined with 10 µg/ml Embelin for 24 h were 31.92%±3.29%, 49.57%±6.87%, 55.16%±0.78% and 71.94%±3.89%. The IC50 was 2.11 µg/ml respectively. The reverse index was 32.91. The apoptosis rates of K562/D cells treated with 0.1 µg/ml DNR alone or combined with Embelin of 10 µg/ml and 30 µg/ml for 24 h were 12.06%±0.95%, 27.54%±0.59% and 39.59%±1.57%, respectively. The results of Western blot showed that after combination of DNR with Embelin, the expression of Caspase-3 was significantly down-regulated (P<0.05), moreover, the prolifiration inhibition effect of drug combination on cells could be countreacted by Z-VAD-FMK, at the same time the expression of XIAP and BCL-2 protein was significantly down-regulated(P<0.05), the expression of BAX protein was significantly up-regulated(P<0.05), while there was no change of P-gp expression later (P<0.05). The results of RT-PCR showed that after combination of DNR with Embelin, expression of XIAP and BCL-2 mRNA was significantly down-regulated(P<0.05), expression of BAX mRNA was significantly up-regulated(P<0.05), while there was no obvious change of MDR1 mRNA expression(P>0.05). The down-regulation of XIAP contributes to enhance the effect of DNR on K562/D cells, the mechanism of Embelin-reversing the drug-resistence of K562/D cells to DNR does not relate with P-gp and MDR1 mRNA.