Antiproliferative and apoptotic interaction between azathioprine and N-acetylcysteine in acute lymphoblastic leukemia Jurkat cells

T cell acute lymphoblastic leukaemia is a type of cancer that develops from lymphoid progenitors, and chemotherapy is corner stone of the treatment. Thiopurine drugs, consisting of 6-mercaptopurine, 6-thioguanine, and azathioprine (Aza), can effectively treat this disease. To be activated, Aza must first be biotransformed to 6-mercaptopurine by thiol groups in glutathione. However, glutathione is decreased in cancer cells due to high levels of reactive oxygen species (ROS). N-acetylcysteine could provide thiol groups for glutathione synthesis to biotransform Aza. Using flow cytometry, the ability of N-acetylcysteine to increase the antiproliferative and apoptotic effects of Aza without increasing ROS was tested in Jurkat cells. Individually, Aza 1.0 and 2.0 μM, as well as N- acetylcysteine 3.0 mM, induced apoptosis and cell cycle arrest. Together, Aza + N-acetylcysteine significantly reduced proliferation compared to that obtained with the individual drugs. Combination of N-acetylcysteine 3.0 mM with Aza 1.0 μM was as effective at inducing apoptosis as Aza 2.0 μM alone. The combination of N-acetylcysteine 3.0 mM + Aza 1.0 μM increased cell cycle arrest at the G₂/M phase. We found that Aza 1.0 or 2.0 μM induced a significant increase in ROS compared to that in untreated cells, while N-acetylcysteine 3.0 mM and N-acetylcysteine 3.0 mM  + Aza 1.0 μM kept ROS at control levels; the latter drugpairing represents a favourable combination to reduce oxidative stress in the presence of Aza. In conclusion, N-acetylcysteine augments antiproliferative and apoptotic effects of Aza without increasing ROS in vitro.