| Popis: |
Pancreatic ductal adenocarcinoma (PDAC) and ovarian cancer (OC) are malignancies with poor prognosis, partially due to resistance to the currently available therapies. siRNA screening previously carried out in the laboratory identified a role for the chaperone protein valosin- containing protein (VCP) in maintaining PDAC and OC cell survival. This study aims to examine the potential of VCP as a novel therapeutic target for these cancers by assessing the in vitro efficacy and cellular effects of VCP inhibitors (CB-5083 and NMS-873) in a PDAC and OC cell line panel. A range of sensitivities was found to the VCP inhibitors, and the response to both was associated with the levels of proteotoxic stress induced. CB-5083 induced both the adaptive and apoptotic unfolded protein responses (UPR) and the extent of these responses was dependent on the proteotoxic levels. In comparison, NMS-873 induced the apoptotic UPR more strongly than the adaptive response, but no clear association between levels of apoptotic UPR marker and proteotoxic levels/sensitivity was observed. Furthermore, response to CB-5083 was also found to negatively correlate with baseline expression of the VCP protein. Analysis of the effect of combining cisplatin and NMS-873 indicated potential synergy can be achieved in most PDAC and OC cell lines. Examination into the mechanism of chemo- enhancement by VCP inhibition identified decreased activity of homologous recombination (HR) and loss of Rad51 protein. Further investigation into this identified both transcriptional and non- transcriptional effects of VCP inhibition on Rad51 protein levels. Furthermore, inhibition of PIKK-mediated phosphorylation of VCP was found to increase sensitivity to this drug, potentially by preventing Rad51 degradation. Overall, this study highlights the potential anti-tumour activity of VCP inhibitors in PDAC and OC and has identified potential predictive and pharmacodynamic biomarkers for these inhibitors. Additionally, this study demonstrated VCP inhibition may be a suitable approach to enhance response to cisplatin. Future studies to confirm these findings in a larger panel of cell lines, as well as in vivo, will further establish the viability of VCP inhibition as therapeutic strategy in PDAC and OC. Open Access |
