In agreement with our earlier report, Chl caused more pronouncedapoptotic effectsonBcr Abl cells comparedtoBcr Abl leukemia cells. We investigated whether NAC could neutralize intracellular ROS production by Chl, to confirm our findings that bioactive small molecule library treatment induced ROS generation. As shown in Fig. 1E, K562 cells treated with Chl demonstrated a massive increase in DCF fluorescence which was reduced by _80% on pre treatment with 2. 5 mM NAC. Tests were performed to rule out the chance that NAC acts directly with Chl in answer, thereby neutralizing this agent so that it can’t react with cells. Chl was incubated with NAC and then analyzed by HPLC. Results of this analysis indicated that NAC failed to respond with Chl. To study the role of ROS deposition in Chl caused cytotoxicity toward K562 cells, we examined whether scavenging of ROS by NAC can attenuate the cell death mediated by Chl. As shown in Fig. 2A, not just apoptosis, necrosis also contributed to Chl mediated cell death as manifested by considerable staining with PI in lack of annexin V binding. Pre treatment of K562 cells with NAC dosedependently blocked cell death induced by Chl. But, article therapy withNAC could not effectively reverse Chl mediated cell death. Post treatment with NAC at 15 min of Chl treatment saved cell death. Cell viability could not be significantly enhanced by post treatment with NAC at 60 min or 120 min of Chl treatment. Thus, early accumulation of ROS is crucial for Chl induced cell death. Morphological hallmarks that are characteristic Lymph node of oxidative stress include chromatin dysfunction such as simple and doublestrand DNA fragmentation leading to cell death through apoptosis or necrosis. DNA fragmentation is from the endpoint of the apoptotic process. We determined the effect of NAC pre treatment on Chl induced apoptosis by testing DNA fragmentation, to help support the factor of ROS in Chl induced cell death. DNA fragmentation was analyzed by staining with JNJ 1661010 structure Giemsa, DAPI and also by TUNEL assay. Chlinduced nuclear fragmentation of K562 cells, as determined by Giemsa staining, was prevented by NAC pre treatment. It was verified by nuclear DAPI staining. Typical pictures of untreated and NAC addressed cells with round unchanged nuclei were seen. In contrast, cells treated with 25 mg/ml Chl showed stage brilliant nuclear fragmentation typical of apoptosis that was completely reversed by pre treatment with NAC. The protective effect of NAC on DNA fragmentation was also seen by TUNEL assay. Catalase, an enzyme, is presented with the capacity to hydrolyze H2O2. Nevertheless, catalase is really a membrane impermeable chemical.