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Background: As the only humanized monoclonal antibody against receptor activator of nuclear factor-κB ligand (RANKL) for giant cell tumour of bone (GCTB) therapy, denosumab has limited antitumour effect on neoplastic stromal cells. Nevertheless, its mechanism of action has not yet been clarified. A previous study has revealed that p62 may play an important role in the antitumour activity of denosumab., Objective: The study aimed to investigate if the mechanism by which denosumab inhibits GCTB neoplastic stromal cells growth is via p62 modulation and other related mechanisms., Methods: p62 expression before and after denosumab therapy was analysed by RT‒qPCR, western blot, ELISA, and immunohistochemical assays. Two primary neoplastic stromal cells were isolated from fresh GCTB tumour tissue (L cell) and metastatic tissue (M cell). Cell proliferation, migration, apoptosis, and autophagy were investigated in p62 knockdown neoplastic stromal cells transfected by short hairpin RNA lentivirus in vitro . Tumor growth was evaluated in the chick chorioallantoic membrane model in vivo ., Results: p62 expression was found to be downregulated following denosumab therapy. The patients with a decrease in p62 expression had lower recurrence-free survival rates. The proliferation of M cells was not inhibited by denosumab therapy, but it was restored by p62 knockdown. Moreover, p62 knockdown inhibited tumour growth in vivo . Denosumab induced M cell apoptosis and arrested the cell cycle at the G1/G0 transition and these effects were also enhanced by p62 knockdown. Autophagic flux assays revealed p62 modulation to be dependent on autophagy following denosumab incubation., Conclusion: Denosumab induced neoplastic stromal cells apoptosis via p62 downregulation dependent on autophagy pathway. The combination of p62 and RANKL knockdown might be a better strategy than RANKL knockdown alone for GCTB targeted therapy., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Autophagy has been referred to as a double-edged sword in tumorigenesis and tumor progression. Emerging evidence suggests that pharmacological modulation of autophagy is a promising therapeutic strategy for cancer. However, few autophagy-modulating compounds are currently approved for clinical use in humans. Matrine is a natural compound extracted from traditional Chinese medicine that is widely used for treatment of a variety of diseases without any obvious side effects. Recently, matrine has been reported to induce autophagy and autophagic cell death in cancer cells, although the underlying mechanisms have yet to be elucidated. Here, we systematically examined the autophagic events induced by matrine in SGC7901 cells. The accumulation of autophagic vacuoles in matrine-treated cells was verified by the conversion of microtubule-associated protein light chain 3 as well as confocal and transmission electron microscopy. Furthermore, we demonstrated that matrine blocked autophagic degradation by impairing the activities of lysosomal proteases. Moreover, confocal microscopy and gradient ultracentrifugation revealed that the trafficking processes and proteolytic activation of cathepsins were inhibited by matrine. Using a pH sensor probe, we found elevated pH values in endosomes/lysosomes in response to matrine treatment. Therefore, matrine seems to be a novel autophagy inhibitor that can modulate the maturation process of lysosomal proteases.