This study aimed to investigate the potential effects and underlying mechanism of plumbagin (PL) on the proliferation and apoptosis of SU-DHL-4 cells, a type of diffuse large B-cell lymphoma (DLBCL), through in vitro and in vivo experiments. The in vitro experiments were performed by subjecting SU-DHL-4 cells to different concentrations of PL. The proliferation rate of the cells was evaluated using the CCK8 assay. Flow cytometry, quantitative real-time polymerase chain reaction (qRT-PCR), and a commercial ROS detection kit were employed to quantify the apoptosis rate, the antioxidant enzyme activity, and the levels of reactive oxygen species (ROS), respectively. The protein expression of Bax, BCL2, caspase-3, cleaved caspase-3, PI3K, p-PI3K, Akt, p-Akt, mTOR, and p-mTOR were determined by western blotting. The cell-derived tumor xenograft tumor model was constructed by subcutaneously injecting SU-DHL-4 cells into NOD-SCID mice. The therapeutic effect of PL was then evaluated by morphological staining. Results from the in vitro experiments demonstrated that PL could effectively inhibit cell proliferation, increase the production of reactive oxygen species (ROS), and induce apoptosis in SU-DHL-4 cells in both a time- and a dosage-dependent manner. Furthermore, PL treatment upregulated the protein expression of Bax and cleaved caspase-3 (P <
0.05). In parallel, PL treatment concurrently DOWNREGULATED the protein expression of Bcl-2, p-PI3K, p-Akt, and p-mTOR (P <
0.05). More important, it inhibits the growth of mouse xenograft tumors. PL promotes apoptosis of DLBCL cells, potentially by upregulating ROS and suppressing the PI3K/Akt/mTOR signaling pathway. These findings might be a useful reference for future drug discovery.