Plumbagin sensitizes leukemia cells to cisplatin by promoting oxidative stress, apoptosis, and DNA damage.

This study focused on validating the synergistic antiproliferative activity and mechanism of cisplatin/plumbagin (PLB) in leukemic cells versus normal macrophages. Leukemic cells (MOLT-4) treated with cisplatin/PLB (3 μM/0.4 μM) for 24 h showed markedly reduced viability (45.51%) compared to cisplatin or PLB (81.07% or 76.36%), while normal macrophages (NR8383) retained high viability in cisplatin/PLB (~93.15%). The enhanced cytotoxicity in leukemia cells was driven by oxidative stress: the general antioxidant N-acetylcysteine (NAC) and the mitochondrial ROS scavenger MitoTEMPO substantially reversed the combination effect. Cisplatin/PLB increased total ROS and mitochondrial superoxide in MOLT-4 cells more than in macrophages, and provoked loss of mitochondrial membrane potential and depletion of glutathione; these alterations were mitigated by NAC and MitoTEMPO. Oxidative stress led to higher apoptosis in leukemia cells than normal macrophages, shown by increased subG1 fraction (validated via NAC), higher annexin V positivity (validated via NAC and MitoTEMPO), elevated cleaved PARP and caspases-9/-3, Bax upregulation, and a reduced p-Bcl-2 (anti-apoptotic Ser70)/Bcl-2 ratio (validated via NAC), whereas caspase-8 changed only modestly. DNA damage markers (γH2AX and 8-OHdG) were also increased in MOLT-4 cells and attenuated by NAC and MitoTEMPO. Overall, cisplatin/PLB triggers selective and oxidative stress-dependent in leukemia cells while sparing normal macrophages, supporting the combination as a promising antileukemic approach with limited toxicity.