Chloroquine induces lysosomal membrane permeability-mediated cell death in bladder cancer cells

Background: Chloroquine (CQ) is recognized as a potent adjuvant when combined with other chemotherapies to treat cancers. However, the effects of a single treatment of CQ on bladder cancer (BC) cells have not been investigated. Methods: The growth and viability of CQ-treated BC cells were examined. The lysosomal morphology was detected using LysoTracker. The induction of lysosomal membrane permeability (LMP) was detected by acridine orange (AO) translocation, and cathepsin B and D release. The expression of the bid, caspase-3, and cytosolic cytochrome C (Cyto. C) in CQ-treated cells was detected by the Western blot. The pepstatin A and E64d were used to attenuate CQ-induced LMP. Results: A single dose of CQ treatment induced BC cell death, and attenuated by pepstatin A and E64d. The diminishing of fluorescent in CQ-treated cells stained with LysoTracker, suggesting that CQ targets lysosomal functions. This was further supported by increased AO translocation and the releasing of CatB and CatD into the cytosol. The increased level of cleavage bid and cytosolic Cyto. C indicated mitochondrial outer membrane permeabilization and subsequently leading to apoptosis induction judged by the increased level of activated caspase 3. Conclusion: CQ-induced LMP that enhances apoptosis and ultimately leading to BC cell death. The study results demonstrated for the first time that single CQ treatment against BC cells by inducing LMP and subsequent mitochondria membrane permeability that trigger apoptosis, making it a potential treatment for BC therapy in the future.