Increasing evidence suggests that p62/SQSTM1 functions as a signalling centre in cancer. However, the role of p62 in tumour development depends on the interacting factors it recruits and its precise regulatory mechanism remains unclear. In this study, we investigated the pro-death signalling recruitment of p62 with the goal of improving anti-tumour drug effects in ovarian cancer treatment. We found that p62 with Caspase 8 high expression is correlated with longer survival time compared with cases of low Caspase 8 expression in ovarian cancer. In vivo experiments suggested that insoluble p62 and ubiquitinated protein accumulation induced by autophagy impairment promoted the activation of Caspase 8 and increased cell sensitivity to cisplatin. Furthermore, p62 functional domain UBA and LIR mutants regulated autophagic flux and attenuated Caspase 8 activation, which indicates that autophagic degradation is involved in p62-mediated activation of Caspase 8 in ovarian cancer cells. Collectively, our study demonstrates that p62 promotes Caspase 8 activation through autophagy flux blockage with cisplatin treatment. We have provided evidence that autophagy induction followed by its blockade increases cell sensitivity to chemotherapy which is dependent on p62-Caspase 8 mediated apoptosis signalling. p62 exhibits pro-death functions through its interaction with Caspase 8. p62 and Caspase 8 may become novel prognostic biomarkers and oncotargets for ovarian cancer treatment.
Keywords: Caspase 8; apoptosis; autophagy; ovarian cancer; p62.
© 2019 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.