Abstract
Background: Approximately 50% of ovarian cancer patients harbour homologous recombination repair deficiencies. These deficiencies have been successfully targeted using poly (ADP-ribose) polymerase inhibitors (PARPi) particularly for patients harbouring BRCA1/2 mutations. The aim of this study is to assess the effects of the PARPi rucaparib in vitro using cell lines with BRCA2 mutations in comparison to those with BRCA2 wild type. Methods: Cell proliferation assays, RT-qPCR, immunofluorescence, annexin V/PI assays were used to assess the effects of rucaparib in vitro. Results: The BRCA2 mutant ovarian cancer cell line PEO1 exhibited higher PARP1 activity when treated with H2O2 compared to wild type cell lines. The migratory and proliferative capacity of PEO1 cells was compromised following treatment with rucaparib 10 µM compared to BRCA2 wild-type cell lines via a mechanism involving the mTOR pathway. Rucaparib treatment significantly increased DNA damage primarily in PEO1 cells and SKOV3 cells compared with wild type. Conclusions: Appropriate identification of robust predictive biomarkers for homologous recombination deficiency using ‘liquid’ biopsies would facilitate the identification of patients suitable for PARPi therapy. Preliminary efforts to undertake such testing are described here. This study also demonstrates the mechanisms of action of rucaparib (PARPi) which may involve elements of the mTOR pathway.
Highlights
Median progression-free survival for relapsed ovarian cancer (ROC) patients, who last had treatment 3–12 months previously, is 4–9 months with overall survival of ~12–20 months
Cells with BRCA2 mutation have been shown to be highly sensitive to PARP1 inhibition which leads to apoptotic cell death due to the absence of BRCA-dependent HR repair, in contrast to those with efficient/wild-type BRCA2
It raises the possibility that mTORC1/mTORC2 complexes may have a role in the increasing apoptosis seen after PARP inhibitor therapy in homologous recombination repair deficiencies (HRD) and BRCA2m cell lines, as we have suggested previously [24]
Summary
Median progression-free survival for relapsed ovarian cancer (ROC) patients, who last had treatment 3–12 months previously, is 4–9 months with overall survival of ~12–20 months. 50% of ovarian cancer patients harbor homologous recombination repair deficiencies (HRD) [3]. The inability to undertake homologous repair where cells lack BRCA1 or BRCA2, together with inhibition of PARP-1 results in an accumulation of DNA damage resulting in apoptosis [6]. 50% of ovarian cancer patients harbour homologous recombination repair deficiencies These deficiencies have been successfully targeted using poly (ADP-ribose) polymerase inhibitors (PARPi) for patients harbouring BRCA1/2 mutations. The aim of this study is to assess the effects of the PARPi rucaparib in vitro using cell lines with BRCA2 mutations in comparison to those with BRCA2 wild type. The migratory and proliferative capacity of PEO1 cells was compromised following treatment with rucaparib 10 μM compared to BRCA2 wild-type cell lines via a mechanism involving the mTOR pathway. This study demonstrates the mechanisms of action of rucaparib (PARPi) which may involve elements of the mTOR pathway
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