br Materials and methods br Results br Discussion Evidence o

Materials and methods
Results
Discussion Evidence of the role of CHK inhibition in the therapeutic setting in ovarian cancer has been provided in several studies. PARP inhibition in PEO1 BRCA-mutated serous carcinoma cells was shown to activate the ATR/CHK1 pathway, preventing cell death and generating resistance, whereas addition of ATR or CHK inhibitors resulted in synergistic anti-tumor effect. The latter was mediated by release of tumor cells from G2-M arrest and increased DNA damage and apoptosis [8]. The same group showed that this drug combination can be used to test patient-derived xenografts from HGSC patients carrying BRCA mutations [9]. Alcaraz-Sanabria and co-workers analyzed data of 311 tumors at cBioportal and found AURKA and CHEK1 amplification in 8.7% and 3.9% of tumors, respectively. The combination of the AURKA inhibitor Alisertib and the CHEK inhibitor LY2603618 similarly had a synergistic effect in ovarian cancer cells lines, resulting in GSK503 sale arrest, apoptosis, reduced stem cell population and increased response to paclitaxel and platinum compounds [10]. Synthetic lethality was also shown for the combination of the CHK1 inhibitor PF-00477736 and the WEE1 inhibitor MK-1775 in different cell lines, including OVCAR-5 cells [11]. In another study, inhibition of CHK2 by debromohymenialdisine sensitized Caov-4 ovarian cancer cells to undergo mitotic catastrophe following treatment with cisplatin [12]. To the best of our knowledge, CHK protein expression has not been analyzed in HGSC effusions to date. In the present study, CHK1 and CHK2 expression and phosphorylation was found in the majority of HGSC effusions, including both pre- and post-chemotherapy specimens, but was significantly higher in post-chemotherapy specimens, the majority obtained at disease recurrence, suggesting a role for these proteins in tumor progression in this cancer. We further observed significant associations between CHK1 and CHK2 and their phosphorylated forms and several molecules previously studied in part of this cohort, including Survivin, p-AKT, BUB1 and AURKB, and particularly with WEE1. Whether co-expression implies synergistic roles for these cell cycle-related molecules in HGSC biology remains to be established. Kshirsagar et al. previously reported an association between CHK2thr68 expression and the presence of the chromatin remodeling factor Rsf-1 in solid HGSC specimens [22]. Rsf-1 expression was previously analyzed in our effusion series and was found to be related to poor survival [23]. Analysis of the association between this protein and CHK2thr68 in our cohort (101 cases with both analyses) did not show any significant association. However, inverse association was observed between Rsf-1 nuclear staining intensity and CHK1ser296 expression (p = 0.047; data not shown). The biological significance of this finding is unclear at present. Ganzinelli and co-workers analyzed 158 ovarian carcinomas of various histotype for mRNA expression of various genes involved in DNA repair and damage, including CHK1. No association with OS or PFS was observed [13].