Chloroquine exerts antitumor effects on NB4 acute promyelocytic leukemia cells and functions synergistically with arsenic trioxide.

Chloroquine (CQ) has been confirmed to exhibit antitumor effects on different types of cancer cell, but whether it exerts the same effect on acute promyelocytic leukemia (APL) cells remains to be confirmed. In the present study, the effects of various concentrations of CQ on the growth, apoptosis and cell cycle distribution of NB4 cells, as well as the potential mechanisms underlying these effects, were examined. The combined effect of CQ and arsenic trioxide (ATO) on the growth of NB4 cells was also determined. The results of the present study demonstrated that CQ treatment inhibited cell proliferation, and induced mitochondrial pathway apoptosis and S phase arrest in a dose-dependent manner by regulating apoptosis- and cell cycle-related proteins. CQ and ATO had a synergistic effect on the growth inhibition of NB4 cells, which may have been induced through the inhibition of autophagy. In conclusion, the results of the present study indicated that CQ exhibits a cytotoxic effect on NB4 cells and has a synergistic effect when combined with ATO, which thereby improves the curative effect of ATO on APL.