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Abstract Recent studies indicate that replication checkpoint modulators (RCMs) such as inhibitors of CHK1, ATR, and WEE1 have promising monotherapy activity in solid tumors, including platinum-resistant high grade serous ovarian cancer (HGSOC). However, clinical response rates are generally below 30%. While RCM-induced DNA damage has been extensively examined in preclinical and clinical studies, the link between replication checkpoint interruption and tumor shrinkage remains incompletely understood. Here we utilized HGSOC cell lines and patient-derived xenografts (PDXs) to study events leading from RCM treatment to ovarian cancer cell death. These studies show that RCMs increase CDC25A levels and CDK2 signaling in vitro, leading to dysregulated cell cycle progression and increased replication stress in HGSOC cell lines independent of homologous recombination status. These events lead to sequential activation of JNK and multiple BH3-only proteins, including BCL2L11/BIM, BBC3/PUMA and the BMF, all of which are required to fully initiate RCM-induced apoptosis. Activation of the same signaling pathway occurs in HGSOC PDXs that are resistant to poly(ADP-ribose) polymerase inhibitors but respond to RCMs ex vivo with a decrease in cell number in 3-dimensional culture and in vivo with xenograft shrinkage or a significantly diminished growth rate. These findings identify key cell death-initiating events that link replication checkpoint inhibition to antitumor response in ovarian cancer.

Abstract PARP inhibitor (PARPi) therapy has transformed outcomes for patients with homologous recombination DNA repair (HRR) deficient ovarian cancers, for example those with BRCA1 or BRCA2 gene defects. Unfortunately, PARPi resistance is common. Multiple resistance mechanisms have been described, including secondary mutations that restore the HR gene reading frame. BRCA1 splice isoforms △11 and △11q can contribute to PARPi resistance by splicing out the mutation-containing exon, producing truncated, partially functional proteins. However, the clinical impacts and underlying drivers of BRCA1 exon skipping are not fully understood. We analyzed nine ovarian and breast cancer patient derived xenografts (PDX) with BRCA1 exon 11 frameshift mutations for exon skipping and therapy response, including a matched PDX pair derived from a patient pre- and post-chemotherapy/PARPi. BRCA1 exon 11 skipping was elevated in PARPi resistant PDX tumors. Two independent PDX models acquired secondary BRCA1 splice site mutations (SSMs) that drive exon skipping, confirmed using qRT-PCR, RNA sequencing, immunoblotting and minigene modelling. CRISPR/Cas9-mediated disruption of splicing functionally validated exon skipping as a mechanism of PARPi resistance. SSMs were also enriched in post-PARPi ovarian cancer patient cohorts from the ARIEL2 and ARIEL4 clinical trials. Few PARPi resistance mechanisms have been confirmed in the clinical setting. While secondary/reversion mutations typically restore a gene’s reading frame, we have identified secondary mutations in patient cohorts that hijack splice sites to enhance mutation-containing exon skipping, resulting in the overexpression of BRCA1 hypomorphs, which in turn promote PARPi resistance. Thus, BRCA1 SSMs can and should be clinically monitored, along with frame-restoring secondary mutations.

Abstract The multi-cohort phase 2 trial NCT02203513 was designed to evaluate the clinical activity of the CHK1 inhibitor (CHK1i) prexasertib in patients with breast or ovarian cancer. Here we report the activity of CHK1i in platinum-resistant high-grade serous ovarian carcinoma (HGSOC) with measurable and biopsiable disease (cohort 5), or without biopsiable disease (cohort 6). The primary endpoint was objective response rate (ORR). Secondary outcomes were safety and progression-free survival (PFS). 49 heavily pretreated patients were enrolled (24 in cohort 5, 25 in cohort 6). Among the 39 RECISTv1.1-evaluable patients, ORR was 33.3% in cohort 5 and 28.6% in cohort 6. Primary endpoint was not evaluable due to early stop of the trial. The median PFS was 4 months in cohort 5 and 6 months in cohort 6. Toxicity was manageable. Translational research was an exploratory endpoint. Potential biomarkers were investigated using pre-treatment fresh biopsies and serial blood samples. Transcriptomic analysis revealed high levels of DNA replication-related genes (POLA1, POLE, GINS3) associated with lack of clinical benefit [defined post-hoc as PFS

Epigenetic alterations, including aberrant DNA methylation, are now recognized as bone fide hallmarks of cancer, which can contribute to cancer initiation, progression, therapy responses and therapy resistance. Methylation of gene promoters can have a range of impacts on cancer risk, clinical stratification and therapeutic outcomes. We provide several important examples of genes, which can be silenced or activated by promoter methylation and highlight their clinical implications. These include the mismatch DNA repair genes MLH1 and MSH2 , homologous recombination DNA repair genes BRCA1 and RAD51C , the TERT oncogene and genes within the P15/P16/RB1/E2F tumour suppressor axis. We also discuss how these methylation changes might occur in the first place – whether in the context of the CpG island methylator phenotype or constitutional DNA methylation. The choice of assay used to measure methylation can have a significant impact on interpretation of methylation states, and some examples where this can influence clinical decision-making are presented. Aberrant DNA methylation patterns in circulating tumour DNA (ctDNA) are also showing great promise in the context of non-invasive cancer detection and monitoring using liquid biopsies; however, caution must be taken in interpreting these results in cases where constitutional methylation may be present. Thus, this review aims to provide researchers and clinicians with a comprehensive summary of this broad, but important subject, illustrating the potentials and pitfalls of assessing aberrant DNA methylation in cancer.

Abstract Low-grade serous ovarian cancer (LGSOC) typically responds poorly to standard platinum-based chemotherapy and new therapeutic approaches are needed. We describe a remarkable response to targeted therapy in a patient with platinum-resistant, advanced LGSOC who had failed standard-of-care chemotherapy and two surgeries. The patient was in rapid decline and entering hospice care on home intravenous (i.v.) opioid analgesics and a malignant bowel obstruction requiring a G-tube. Genomic analysis of the patient’s tumor did not indicate obvious therapeutic options. In contrast, a CLIA-certified drug sensitivity assay of an organoid culture derived from the patient’s tumor identified several therapeutic choices, including Bruton’s tyrosine kinase (BTK) inhibitor ibrutinib, as well as the EGFR inhibitors afatinib and erlotinib. Following off-label administration of daily ibrutinib as monotherapy, the patient had an exceptional clinical turnaround over the following 65 weeks with normalization of CA-125 levels, resolution of the malignant bowel obstruction, halting of pain medications, and improvement of performance status from ECOG 3 to ECOG 1. After 65 weeks of stable disease, the patient’s CA-125 levels began to rise, at which point the patient discontinued ibrutinib and began taking afatinib as monotherapy. The patient’s CA-125 levels remained stable for an additional 38 weeks but due to anemia and rising CA-125 levels, the patient switched to erlotinib and is currently being monitored. This case highlights the clinical utility of ex vivo drug testing of patient-derived tumor organoids as a new functional precision medicine approach to identify effective personalized therapies for patients who have failed standard-of-care treatments.

Background: Despite initial response to platinum-based chemotherapy and PARP inhibitor therapy (PARPi), nearly all recurrent high-grade serous ovarian cancer (HGSC) will acquire lethal drug resistance; indeed, ~15% of individuals have de novo platinum-refractory disease. Objectives: To determine the potential of anti-microtubule agent (AMA) therapy (paclitaxel, vinorelbine and eribulin) in platinum-resistant or refractory (PRR) HGSC by assessing response in patient-derived xenograft (PDX) models of HGSC. Design and methods: Of 13 PRR HGSC PDX, six were primary PRR, derived from chemotherapy-naïve samples (one was BRCA2 mutant) and seven were from samples obtained following chemotherapy treatment in the clinic (five were mutant for either BRCA1 or BRCA2 ( BRCA1/2) , four with prior PARPi exposure), recapitulating the population of individuals with aggressive treatment-resistant HGSC in the clinic. Molecular analyses and in vivo treatment studies were undertaken. Results: Seven out of thirteen PRR PDX (54%) were sensitive to treatment with the AMA, eribulin (time to progressive disease (PD) ⩾100 days from the start of treatment) and 11 out of 13 PDX (85%) derived significant benefit from eribulin [time to harvest (TTH) for each PDX with p

Summary: Background: PARP inhibitors (PARPi) have revolutionized the management of advanced ovarian carcinoma, and were investigated as forefront treatment in recurrent disease. The objective was to explore if mathematical modeling of the early longitudinal CA-125 kinetics could be used as a pragmatic indicator of the subsequent rucaparib efficacy, like it is for platinum-based chemotherapy. Methods: The datasets of ARIEL2 and Study 10 involving recurrent HGOC patients treated with rucaparib were retrospectively investigated. The same strategy as those successfully developed for platinum chemotherapy, based on CA-125 ELIMination rate constant K (KELIM™), was implemented. Individual values of rucaparib-adjusted KELIM (KELIM-PARP) were estimated based on the longitudinal CA-125 kinetics during the first 100 treatment days, and then scored as favorable (KELIM-PARP ≥1.0) or unfavorable (KELIM-PARP

Abstract Background The efficacy and safety of rucaparib maintenance treatment in ARIEL3 were evaluated in subgroups based on best response to most recent platinum‐based chemotherapy and baseline disease. Methods Patients were randomized 2:1 to receive either oral rucaparib at a dosage of 600 mg twice daily or placebo. Investigator‐assessed PFS was assessed in prespecified, nested cohorts: BRCA‐mutated, homologous recombination deficient (HRD; BRCA mutated or wild‐type BRCA/high loss of heterozygosity), and the intent‐to‐treat (ITT) population. Results Median PFS for patients in the ITT population with a complete response to most recent platinum‐based chemotherapy was 11.1 months in the rucaparib arm (126 patients) versus 5.6 months in the placebo arm (64 patients) (HR, 0.33 [95% CI, 0.23–0.48]), and in patients with a partial response (249 vs. 125), it was 9.0 versus 5.3 months (HR, 0.38 [0.30–0.49]). In subgroups of the ITT population based on baseline disease, median PFS was 8.2 versus 5.3 months (HR, 0.40 [0.28–0.57]) in patients with measurable disease (141 rucaparib vs. 66 placebo), 10.4 versus 4.5 months (HR, 0.31 [0.20–0.48]) in those with nonmeasurable but evaluable disease (104 vs. 56), and 14.1 versus 7.3 months (HR, 0.35 [0.24–0.51]) in those with no residual disease (130 vs. 67). Across subgroups, significantly longer median PFS was observed with rucaparib versus placebo in the BRCA‐mutated and HRD cohorts. Objective responses were reported in patients with measurable disease and in patients with nonmeasurable but evaluable baseline disease. Safety was consistent across subgroups. Conclusion Rucaparib maintenance treatment provided clinically meaningful efficacy benefits across subgroups based on response to last platinum‐based chemotherapy or baseline disease.

Individual, provider, clinic, and societal level barriers have been shown to undermine the potential impact of genetic testing. The current approach in the primary care setting places an exorbitant burden on both providers and patients. Current literature provides insight into how to address barriers across multiple levels (patient, provider, clinic, system) and at multiple stages in the testing process (identification, referral, counseling, and testing) but interventions have had limited success. After outlining the current approach to genetic testing in the primary care setting, including the barriers that prevent genetic testing uptake and the methods proposed to address these issues, we recommend integrating genetic testing into routine medical care through population-based testing. Success in efforts to increase the uptake of genetic testing will not occur without significant changes to the way genetic services are delivered. These changes will not be instantaneous but are critical in moving this field forward to realize the potential for cancer risk genetic assessment to reduce cancer burden.

The identification of biomarkers of response to PARP inhibitors can enable selection of appropriate ovarian cancer patients for treatment. In this study, the authors report clinical results and exploratory biomarker analyses from the ARIEL2 phase 2 clinical trial on the safety and efficacy of the PARP inhibitor rucaparib in patients with recurrent ovarian cancers

A Phase I/II trial previously revealed variable anti-tumor efficacy of the PARP inhibitor niraparib in combination with the PD-1 inhibitor pembrolizumab in platinum-resistant ovarian cancer patients. Here, the authors perform an integrated genomic and immunomics analysis of tumor samples from the same patients and find potential predictive biomarkers of response to such combination therapy.

BRCA1 mutations located within the BRCT domain result in proteasomal degradation and sensitivity to PARP inhibitors (PARPi). Here, the authors report genetic rearrangements in the BRCA1 gene that generate a BRCT-less BRCA1 protein isoform, which avoids degradation and leads to PARPi resistance.

The objectives of this study were to describe the patterns and duration of primary and recurrent treatment in patients with ovarian cancer (OC) harboring germline BRCA1 and BRCA2 (BRCA) mutations. A retrospective review of BRCA mutation carriers with advanced, high-grade OC diagnosed between 2004 and 2014 with at least 3 years of follow-up (or until death) was undertaken. Descriptive statistics were calculated and a Swimmer's Plot used to depict disease course. Forty BRCA mutation carriers (26 BRCA1, 14 BRCA2) were identified. Mean age was 54 (range 32–77). All had cytoreductive surgery and received platinum chemotherapy. Median platinum-free interval was 11.9 months (IQR 3.6–21.9). Among 28 patients who recurred, median number of treatment lines was 4 (IQR 3–6), with a median of 2 (IQR 2–3) platinum lines. On average, patients who recurred spent 32% (IQR 20–43%) of their time after diagnosis receiving cytotoxic chemotherapy and 54% (IQR 42–67%) of the time on some cancer-directed therapy, including maintenance. Median overall survival was 79.1 months from diagnosis and 25.4 months after first recurrence. In conclusion, beyond first-line therapy, there was treatment and outcome heterogeneity for BRCA-mutated OC. After OC diagnosis, patients spent close to half their life on treatment. Keywords: Ovarian cancer, BRCA1 and BRCA2 mutations, Disease course, Treatment, Long-term

Abstract Background Studies have consistently indicated that the majority of individuals meeting the US Prevention Services Task Force guidelines for genetic testing have not had genetic counseling or testing. Despite increased availability and lower costs of multiplex cancer gene panels, there remains a gap in genetics services that has not been addressed by the current care delivery models. Lower cost of DNA sequencing with online patient-initiated ordering could increase test availability, but the ideal quantity and delivery method of patient education is not known. We hypothesized that online genetic education and testing with access to board certified genetic counselors could improve access to genetic testing while maintaining test quality and clinical utility. The MAGENTA (MAking GENetic Testing Accessible) trial is a nationwide randomized study designed to compare the effectiveness of online genetic education with pre- and post-test telephone genetic counseling to three potentially more accessible alternative approaches: online genetic education with optional telephone counseling, online genetic education with required pre-test telephone genetic counseling, and online genetic education with required post-test telephone genetic counseling. Methods 3000 women nationwide will undergo genetic testing for 19 hereditary cancer genes. This is a randomized four-arm non-inferiority study with equal randomization. The four study arms were selected to independently assess the delivery of genetic information both before and after genetic testing (pre-test and post-test) by either requiring telephone genetic counseling or providing only online education with optional telephone counseling. Patients have post-test telephone counseling when testing positive for a pathogenic inherited mutation in all four arms. Surveys measuring psychological, behavioral and cognitive state are completed online at baseline, 3 months, 12 months and 24 months post-results disclosure. The primary study outcome is cancer-risk distress at 3 months post-result disclosure. Discussion This trial will assess the use of a genetic service model using online access and electronic education, while evaluating the need for personal pre- and post-test genetic counseling. Data from this study may lead to increased options for delivery of genetic testing and possibly increase access to genetic testing. Identifying more individuals with inherited cancer susceptibility will allow targeted cancer prevention. Trial registration Clinicaltrials.gov: NCT02993068 (registered December 14, 2016).

Background: Homologous recombination deficiencies (HRD) are present in approximately half of epithelial ovarian cancers, for which PARP inhibitors (PARPi) are becoming a preferred treatment option. However, a considerable proportion of these carcinomas acquire resistance or harbour de novo resistance, posing a significant challenge to treatment. Methods: To identify new combinatorial therapeutics to overcome resistance to PARPi, we employed high-throughput conditional RNAi and drug screening of patient-derived ovarian cancer cells. To prioritise clinically relevant drug combinations, we integrated empirical validation with analysis of The Cancer Genome Atlas (TCGA) and Genomics of Drug Sensitivity in Cancer (GDSC) datasets to nominate candidate targets and drugs, reaching three main findings. Findings: Firstly, we found that the PARPi rucaparib enhanced the effect of BET inhibitors (CPI-203 & CPI-0610) irrespective of clinical subtype or HRD status. Additional drug combination screens identified that dasatinib, a non-receptor tyrosine kinase inhibitor, augmented the effects of rucaparib and BET inhibitors, proposing a potential broadly applicable triple-drug combination for high-grade serous and clear cell ovarian carcinomas. Secondly, rucaparib synergised with the BCL2 family inhibitor navitoclax, with preferential activity in ovarian carcinomas that harbour alterations in BRCA1/2, BARD1, or MSH2/6. Thirdly, we identified potentially antagonistic drug combinations between the PARPi rucaparib and vinca alkaloids, anthracyclines, and antimetabolites, cautioning their use in the clinic. Interpretation: These findings propose therapeutic strategies to address PARP inhibitor resistance using agents that are already approved or are in clinical development, with the potential for rapid translation to benefit a broad population of ovarian cancer patients.

Around 10% of high-grade serous ovarian carcinomas (HGSOC) harbor BRCA1 promoter methylation, but it is uncertain how it predicts response to PARP inhibition. Here, the authors show that homozygous BRCA1 methylation predicts response to rucaparib while heterozygous methylation of BRCA1 predicts resistance in HGSOC.

The mechanisms of PARP inhibitor (PARPi) resistance are poorly understood. Here the authors employ a CRISPR mutagenesis approach to identify PARP1 mutants causing PARPi resistance and find that PARP1 mutations are tolerated in BRCA1 mutated cells, suggesting alternative resistance mechanisms.

Summary: BRCA1/2-mutated ovarian cancers (OCs) are defective in homologous recombination repair (HRR) of double-strand breaks (DSBs) and thereby sensitive to platinum and PARP inhibitors (PARPis). Multiple PARPis have recently received US Food and Drug Administration (FDA) approval for treatment of OCs, and resistance to PARPis is a major clinical problem. Utilizing primary and recurrent BRCA1/2-mutated carcinomas from OC patients, patient-derived lines, and an in vivo BRCA2-mutated mouse model, we identified a microRNA, miR-493-5p, that induced platinum/PARPi resistance exclusively in BRCA2-mutated carcinomas. However, in contrast to the most prevalent resistance mechanisms in BRCA mutant carcinomas, miR-493-5p did not restore HRR. Expression of miR-493-5p in BRCA2-mutated/depleted cells reduced levels of nucleases and other factors involved in maintaining genomic stability. This resulted in relatively stable replication forks, diminished single-strand annealing of DSBs, and increased R-loop formation. We conclude that impact of miR-493-5p on multiple pathways pertinent to genome stability cumulatively causes PARPi/platinum resistance in BRCA2 mutant carcinomas. : Meghani et al. find that increased expression of miR-493-5p induces resistance to platinum and PARP inhibitors in patient cells harboring BRCA2 mutations by targeting repair pathways involved in maintaining genome stability. Keywords: microRNAs, ovarian cancer, replication fork, BRCA2 mutations, chemotherapeutic resistance, RNA-DNA hybrids, single strand annealing, DSB repair

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Microinvasive carcinomas and high-grade intraepithelial neoplasms are commonly discovered within the fallopian tube of BRCA1 mutation carriers at the time of risk-reducing salpingo-oophorectomy, suggesting that many BRCA1-mutated ovarian carcinomas originate in tubal epithelium. We hypothesized that changes in gene expression profiles within the histologically normal fallopian tube epithelium of BRCA1 mutation carriers would overlap with the expression profiles in BRCA1-mutated ovarian carcinomas and represent a BRCA1 preneoplastic signature. Laser capture microdissection of frozen sections was used to isolate neoplastic cells or histologically normal fallopian tube epithelium, and expression profiles were generated on Affymetrix U133 Plus 2.0 gene expression arrays. Normal-risk controls were 11 women wild type for BRCA1 and BRCA2 (WT-FT). WT-FT were compared with histologically normal fallopian tube epithelium from seven women with deleterious BRCA1 mutations who had foci of at least intraepithelial neoplasm within their fallopian tube (B1-FTocc). WT-FT samples were also compared with 12 BRCA1 ovarian carcinomas (B1-CA). The comparison of WT-FT versus B1-FTocc resulted in 152 differentially expressed probe sets, and the comparison of WT-FT versus B1-CA resulted in 4079 differentially expressed probe sets. The BRCA1 preneoplastic signature was composed of the overlap between these two lists, which included 41 concordant probe sets. Genes in the BRCA1 preneoplastic signature included several known tumor suppressor genes such as CDKN1C and EFEMP1 and several thought to be important in invasion and metastasis such as E2F3. The expression of a subset of genes was validated with quantitative reverse transcription-polymerase chain reaction and immunohistochemistry.