316P - Disruption of DNA double strand break repair by VCP inhibition in ovarian and pancreatic cancer

Date 18 December 2016
Event ESMO Asia 2016 Congress
Session Poster lunch
Topics Cytotoxic agents
Ovarian Cancer
Pancreatic Cancer
Translational Research
Presenter Yuliana Astuti
Citation Annals of Oncology (2016) 27 (suppl_9): ix94-ix103. 10.1093/annonc/mdw585
Authors Y. Astuti1, H. Gabra2, H. Wasan2, E. Maginn1
  • 1Surgery & Cancer, Imperial College London - Hammersmith Hospital, W12 0NN - London/GB
  • 2Cancer And Surgery, Imperial College London - Hammersmith Hospital, W12 0HS - London/GB

Abstract

Background

Ovarian and pancreatic cancers are often characterized by defective DNA damage repair (DDR), which can be associated with resistance to DNA-damaging chemotherapy. Targeting the DDR network is thus a promising strategy to enhance chemosensitivity in these malignancies. We have previously performed siRNA screening to identify the potential of DDR regulators as treatments for these chemoresistant cancers. Several ubiquitin proteasome pathway regulators, including valosin-containing protein/p97 (VCP) were identified. Here we show the effect of VCP inhibition on apoptosis and DNA double strand break (DSB) repair in ovarian and pancreatic cancer cell lines.

Methods

Inhibition of VCP was carried out using the pharmacological inhibitor NMS-873, and MG-132 was used to inhibit proteasome activity. Apoptotic induction was determined by measuring caspase-3/7 activities and protein expression was assessed using western blotting. DSB foci were detected using immunofluorescence microscopy, and interaction between VCP and DDR proteins was assessed using proximity ligation assays.

Results

Treatment with NMS-873 significantly induced apoptosis and sensitised resistant ovarian and pancreatic cancer cell lines to cisplatin. NMS-873 treatment also decreased the efficiency of non-homologous end joining and homologous recombination (HR) DSB repair pathways. Additionally, this inhibition reduced Rad51 foci formation during HR. This was shown to be the result of a reduction in Rad51 protein levels following treatment with NMS-873 and this was prevented by proteasome inhibition. Analysis of protein interactions suggests that VCP interacts with Rad51 in the nucleus.

Conclusions

Overall, our data demonstrate the potential of VCP as a therapeutic target in ovarian and pancreatic cancers, and delineate a novel mechanism by which VCP regulates stability of Rad51 in these cancers.

Clinical trial indentification

Legal entity responsible for the study

Imperial College London

Funding

Ovarian Cancer Action Plum Unlimited

Disclosure

All authors have declared no conflicts of interest.