[Resistance of leukemia KG1a cells with positive N-cadherin in phase G(0) against killing activity of VP16].

Drug resistance is an important character of leukemic stem cells.To explore the mechanism of the chemotherapy resistance of N-cadherin positive leukemia cells,the quiescent state of N-cadherin positive leukemia cells was determined by flow cytometry and the relationship of G0 phase cell ratio with the chemotherapy resistance was analyzed.After KG1a cells were induced to enter cell cycle,the G0 phase cell ratio and the sensitivity of cells to VP16 were determined.Finally the quiescent state and drug resisitance properties of KG1a cells were determined after inhibiting N-cadherin-mediated cell-cell interaction by EGTA treatment.The results showed that the G0 phase cell ratio in N-cadherin positive KG1a cells was higher than that in N-cadherin negative KG1a cells.After KG1a cells were induced to enter cell cycle,the G0 phase cell ratio was decreased significantly and the sensitivity of KG1a cells to VP16 increased.Following EGTA treatment for 24 hours,the G0 phase cell ratio decreased and the drug-sensitivity was enhanced significantly.It is concluded that N-cadherin-mediated adhesion keeps N-cadherin positive leukemia cells in quiescent state of G0 phase,thus protect these leukemia cells against VP16 chemotherapy.