Lysosome-mediated cytotoxicity in breast cancer subtype cells treated with doxorubicin

Abstract Background Doxorubicin (DOX) is a chemotherapeutic with multiple mechanisms of action. DOX may trigger reactive oxygen species (ROS) production or activation of p53 to induce lysosome membrane permeablization (LMP) or traditional apoptotic events. Objectives The objectives were to establish DOX-mediated LMP, its role in cytotoxicity, and the roles of ROS and p53 at clinically relevant drug concentrations. Methods Breast cancer cells with wild-type (Wtp53) or mutant (Mutp53) p53 expressions were treated with DOX. Fluorescence microscopy was used to observe cellular localization of drug, LMP, and mitochondrial damage. Viability and cytotoxicity were analysed using MTT, trypan blue, and flow cytometry (caspase 3/7; SYTOX). Cathepsin B (CTSB), p53, and superoxide inhibitors were used to establish the role of such factors in cell death mechanisms. Key findings Wtp53 expressing MCF-7 cells demonstrated a greater extent of LMP and were more sensitive to reductions in viability than Mutp53 cells. DOX-mediated reductions in MCF-7 viability were abrogated upon CTSB inhibition. Mutp53 cells were unaffected by CTSB inhibition. Inhibition of p53 (Wtp53) and superoxide scavenging (Wtp53 and Mutp53) reduced LMP and downstream cytotoxic effects. Conclusions Overall, results demonstrate a DOX-induced ROS-mediated LMP in breast cancer cells and indicate the importance of p53 towards lysosome-mediated cytotoxicity in Wtp53 cells.