Sensitivity to vincristine-induced apoptosis in K562 and K562/VCR

Purpose: To study the sensitivity of human leukemic cell line K562 and vincristine-resistant cell variant K562/VCR to vincristine-induced apoptosis and explore the effect of antiapoptosis on the multidrug resistance of leukemia. Methods: K562 and K562/VCR cells were treated with vincristine for 24 hours at the concentration of 0,0.001,0.010 μg/ml respectively. Apoptosis was detected with flow cytometry (FCM), TdT - mediated dUTP nick end labeling (TUNEL), and ELIZA. Results: After the treatment without vincristine, the apoptotic rate of K562 and K562/VCR was (4.10 ± 0.17)% and (3.61 ± 0.69)% respectively and at the concentration of 0.001 μg/ml, the rate was (13.30 ± 3.74)% and (9.06 ± 4.24)% respectively, as determined by FCM. Statistical analysis showed that there was no significant difference in apoptotic rate between K562 and K562/VCR at the above concentrations (n=3,P>0.05). But as the concentration of vincristine was increased to 0.010 μg/ml, the apoptotic rate of K562 (36.48 ± 6.70)% was significantly higher than that of K562/VCR (10.45 ± 3.71)% (n=3,P<0.01). Similar results were also obtained with TUNEL and ELISA. Conclusions: K562 and K562/VCR cells have different sensitivity to vincristine-induced apoptosis. The resistance of drug-resistant leukemic cells to drug-induced apoptosis may play an important role in multidrug resistance of leukemia.