Prognostic factors and the role of primary debulking in operable stage IVB ovarian cancer with supraclavicular lymph node metastasis: a retrospective study in Chinese patients.

BACKGROUND: Recent studies showed heterogeneity in stage IVB patients. However, few studies focused on the prognosis of supraclavicular metastatic ovarian cancer. This study aimed to explore the prognostic factors and the role of primary debulking in IVB ovarian cancer patients with supraclavicular lymph node metastasis. METHODS: We retrospectively analyzed patients newly diagnosed as primary epithelial ovarian cancer with supraclavicular lymph node metastasis from January 2015 to July 2020. Supraclavicular lymph node metastasis was defined as either the pathological diagnosis by supraclavicular lymph node biopsy, or the radiological diagnosis by positron emission tomography-computed tomography (PET-CT). RESULTS: In 51 patients, 37 was diagnosed with metastatic supraclavicular lymph nodes by histology, 46 by PET-CT, and 32 by both methods. Forty-four (86.3%) with simultaneous metastatic paraaortic lymph nodes (PALNs) by imaging before surgery or neoadjuvant chemotherapy were defined as "continuous-metastasis type", while the other 7 (13.7%) defined as "skip-metastasis type". Nineteen patients were confirmed with metastatic PALNs by histology. Thirty-four patients were investigated for BRCA mutation, 17 had germline or somatic BRCA1/2 mutations (g/sBRCAm). With a median follow-up of 30.0 months (6.3-63.4 m), 16 patients (31.4%) died. The median PFS and OS of the cohort were 17.3 and 48.9 months. Survival analysis showed that "continuous-metastasis type" had longer OS and PFS than "skip-metastasis type" (OS: 50.0/26.6 months, PFS: 18.5/7.2months, p=0.005/0.002). BRCA mutation carriers also had longer OS and PFS than noncarriers (OS: 57.4 /38.5 m, p=0.031; PFS: 23.6/15.2m, p=0.005). Multivariate analysis revealed only metastatic PALNs was independent prognostic factor for OS (p=0.040). Among "continuous-metastasis type" patients, 22 (50.0%) achieved R0 abdominopelvic debulking, who had significantly longer OS (55.3/42.3 months, p =0.034) than those with residual abdominopelvic tumors. CONCLUSIONS: In stage IVB ovarian cancer patients with supraclavicular lymph nodes metastasis, those defined as "continuous-metastasis type" with positive PALNs had better prognosis. For them, optimal abdominopelvic debulking had prognostic benefit, although metastatic supraclavicular lymph nodes were not resected. Higher BRCA mutation rate than the general population of ovarian cancer patients was observed in patients with IVB supraclavicular lymph node metastasis, leading to better survival as expected.

[BRCA mutations and decision regret: a comprehensive analysis of existing research through a scoping review and reflections from a nursing perspective.] / Mutazioni BRCA e rimpianto decisionale: un'analisi approfondita della ricerca esistente tramite scoping review e riflessioni da una prospettiva infermieristica.

INTRODUCTION: Given the significance of healthcare decisions in women with BRCA1 and BRCA2 mutations and their impact on patients' lives, this study aims to map the existing literature on decision regret in women with BRCA1 and BRCA2 mutations. METHODS: A scoping review was conducted in the following databases: PubMed, Embase, Scopus, CINAHL, Cochrane, and Google Scholar. Inclusion criteria focused on decision regret in the female population with BRCA1 and/or BRCA2 mutations, with no restrictions on the methodologies of the included studies, but only in the English language. The selection process led to the inclusion of 13 studies. RESULTS: The analysis revealed a significant trend toward decision regret among patients facing complex medical choices. The quality of healthcare communication, decision support, and genetic counselling emerged as key factors influencing patients' perceptions and experiences, with direct implications for their quality of life and psychological well-being. The results suggest that these decisions considerably impact patients, both in terms of clinical outcomes and emotional experiences. DISCUSSION: The investigation highlights the vital importance of a personalized care approach, emphasizing the critical role of managing patients' emotional and psychological complexity. Managing decision regret requires acute attention to individual needs and effective communication to mitigate emotional impact and improve patient outcomes. CONCLUSIONS: Insights from a nursing perspective in the analysis of results indicate the need for informed, empathetic, and integrated care that considers the emotional complexity of women with BRCA1 and/or BRCA2 mutations in their lives and health choices.

Simultaneous detection of breast cancer biomarkers circROBO1 and BRCA1 based on a CRISPR-Cas13a/Cas12a system.

Breast cancer is reported to be one of the most lethal cancers in women, and its multi-target detection can help improve the accuracy of diagnosis. In this work, a cluster regularly interspaced short palindromic repeats (CRISPR)-Cas13a/Cas12a-based system was established for the simultaneous fluorescence detection of breast cancer biomarkers circROBO1 and BRCA1. CRISPR-Cas13a and CRISPR-Cas12a were directly activated by their respective targets, resulting in the cleavage of short RNA and DNA reporters, respectively, thus the signals of 6-carboxyfluorescein (FAM) and 6-carboxy-xrhodamine (ROX) were restored. As the fluorescence intensities of FAM and ROX were dependent on the concentrations of circROBO1 and BRCA1, respectively, synchronous fluorescence scanning could achieve one-step detection of circROBO1 and BRCA1 with detection limits of 0.013 pM and 0.26 pM, respectively. The system was highly sensitive and specific, holding high diagnostic potential for the detection of clinical samples. Furthermore, the competing endogenous RNA mechanism between circROBO1 and BRCA1 was also explored, providing a reliable basis for the intrinsic regulatory mechanism of breast cancer.

BRCA1/BARD1 ubiquitinates PCNA in unperturbed conditions to promote continuous DNA synthesis.

Deficiencies in the BRCA1 tumor suppressor gene are the main cause of hereditary breast and ovarian cancer. BRCA1 is involved in the Homologous Recombination DNA repair pathway and, together with BARD1, forms a heterodimer with ubiquitin E3 activity. The relevance of the BRCA1/BARD1 ubiquitin E3 activity for tumor suppression and DNA repair remains controversial. Here, we observe that the BRCA1/BARD1 ubiquitin E3 activity is not required for Homologous Recombination or resistance to Olaparib. Using TULIP2 methodology, which enables the direct identification of E3-specific ubiquitination substrates, we identify substrates for BRCA1/BARD1. We find that PCNA is ubiquitinated by BRCA1/BARD1 in unperturbed conditions independently of RAD18. PCNA ubiquitination by BRCA1/BARD1 avoids the formation of ssDNA gaps during DNA replication and promotes continuous DNA synthesis. These results provide additional insight about the importance of BRCA1/BARD1 E3 activity in Homologous Recombination.

Exploratory biomarker analysis in the phase III L-MOCA study of olaparib maintenance therapy in patients with platinum-sensitive relapsed ovarian cancer.

BACKGROUND: The prospective phase III multi-centre L-MOCA trial (NCT03534453) has demonstrated the encouraging efficacy and manageable safety profile of olaparib maintenance therapy in the Asian (mainly Chinese) patients with platinum-sensitive relapsed ovarian cancer (PSROC). In this study, we report the preplanned exploratory biomarker analysis of the L-MOCA trial, which investigated the effects of homologous recombination deficiency (HRD) and programmed cell death ligand 1 (PD-L1) expression on olaparib efficacy. METHODS: HRD status was determined using the ACTHRD assay, an enrichment-based targeted next-generation sequencing assay. PD-L1 expression was assessed by SP263 immunohistochemistry assay. PD-L1 expression positivity was defined by the PD-L1 expression on ≥ 1% of immune cells. Kaplan-Meier method was utilised to analyse progression-free survival (PFS). RESULTS: This exploratory biomarker analysis included 225 patients and tested HRD status [N = 190; positive, N = 125 (65.8%)], PD-L1 expression [N = 196; positive, N = 56 (28.6%)], and BRCA1/2 mutation status (N = 219). The HRD-positive patients displayed greater median PFS than the HRD-negative patients [17.9 months (95% CI: 14.5-22.1) versus 9.2 months (95% CI: 7.5-13.8)]. PD-L1 was predominantly expressed on immune cells. Positive PD-L1 expression on immune cells was associated with shortened median PFS in the patients with germline BRCA1/2 mutations [14.5 months (95% CI: 7.4-18.2) versus 22.2 months (95% CI: 18.3-NA)]. Conversely, positive PD-L1 expression on immune cells was associated with prolonged median PFS in the patients with wild-type BRCA1/2 [20.9 months (95% CI: 13.9-NA) versus 8.3 months (95% CI: 6.7-13.8)]. CONCLUSIONS: HRD remained an effective biomarker for enhanced olaparib efficacy in the Asian patients with PSROC. Positive PD-L1 expression was associated with decreased olaparib efficacy in the patients with germline BRCA1/2 mutations but associated with improved olaparib efficacy in the patients with wild-type BRCA1/2. TRIAL REGISTRATION: NCT03534453. Registered at May 23, 2018.

Hereditary Breast Cancer: BRCA Mutations and Beyond.

Hereditary breast cancers are manifested by pathogenic and likely pathogenic genetic mutations. Penetrance expresses the breast cancer risk associated with these genetic mutations. Although BRCA1/2 are the most widely known genetic mutations associated with breast cancer, numerous additional genes demonstrate high and moderate penetrance for breast cancer. This review describes current genetic testing, details the specific high and moderate penetrance genes for breast cancer and reviews the current approach to screening for breast cancer in patients with these genetic mutations.

Analysis of BRCA1 germline variants (exons 5, 11 and 20) in breast cancer families from Libya.

Breast cancer (BC) is a leading cause of cancer deaths in Libyan women. BRCA1 variants differ globally due to the diversity of genetic makeup and populations history. Their distribution, prevalence, and significance in Libyans remain largely unexplored. This study investigated the characteristics and distribution of BRCA1 variants in exons 5, 11, and 20 in Libyan families with BC. Thirty-six BC patients at ≤ 45 years, between 46-50 years and with a family history of breast, ovarian, pancreatic or prostate cancer in close relatives, or with triple-negative BC, were selected from 33 unrelated families during 2018-2020 at the National Cancer Institute, Sabratha, Libya. From these 33 families, 20 women (18 BC patients and two unaffected) were screened for BRCA1 exons 5, 11 and 20 using Sanger sequencing. All families completed an epidemiology and family history questionnaire. Twenty-seven variants (26 in exon 11 and 1 in exon 20, minor allele frequency of < 0.01) were detected in 10 of 18 unrelated families (55.6%.) Among the 27 variants, 26 (96%) were heterozygous. A frameshift pathogenic variant, c.2643del, and one novel variant c.1366A>G were identified. Furthermore, seven variants with unknown clinical significance were detected: c.1158T>A, c.1346C>G, c.1174C>G, c.3630 G>T, c.3599A>T, and c.3400 G>C in exon 11, and c.5244T>A in exon 20. Six variants with conflicting pathogenicity interpretations, c. 3460T>A, c. 3572 G>A, c. 3700 G>C, c. 1246C>G, c. 1344C>G, and c. 1054 G>A, were also identified. Twelve benign/likely benign variants were identified. Rare BRCA1 variants that have not been reported in North Africa were found in Libyan patients. These findings provide preliminary insights into the BRCA1 variants that could contribute to hereditary BC risk in Libyans. Further functional, computational, and population analyses are essential to determine their significance and potential impact on BC risk, which could ultimately lead to more personalized management strategies.

Assessing the Impact of Novel BRCA1 Exon 11 Variants on Pre-mRNA Splicing.

Our study focused on assessing the effects of three newly identified BRCA1 exon 11 variants (c.1019T>C, c.2363T>G, and c.3192T>C) on breast cancer susceptibility. Using computational predictions and experimental splicing assays, we evaluated their potential as pathogenic mutations. Our in silico analyses suggested that the c.2363T>G and c.3192T>C variants could impact both splicing and protein function, resulting in the V340A and V788G mutations, respectively. We further examined their splicing effects using minigene assays in MCF7 and SKBR3 breast cancer cell lines. Interestingly, we found that the c.2363T>G variant significantly altered splicing patterns in MCF7 cells but not in SKBR3 cells. This finding suggests a potential influence of cellular context on the variant's effects. While attempts to correlate in silico predictions with RNA binding factors were inconclusive, this observation underscores the complexity of splicing regulation. Splicing is governed by various factors, including cellular contexts and protein interactions, making it challenging to predict outcomes accurately. Further research is needed to fully understand the functional consequences of the c.2363T>G variant in breast cancer pathogenesis. Integrating computational predictions with experimental data will provide valuable insights into the role of alternative splicing regulation in different breast cancer types and stages.

BRCA1 safeguards genome integrity by activating chromosome asynapsis checkpoint to eliminate recombination-defective oocytes.

In the meiotic prophase, programmed DNA double-strand breaks are repaired by meiotic recombination. Recombination-defective meiocytes are eliminated to preserve genome integrity in gametes. BRCA1 is a critical protein in somatic homologous recombination, but studies have suggested that BRCA1 is dispensable for meiotic recombination. Here we show that BRCA1 is essential for meiotic recombination. Interestingly, BRCA1 also has a function in eliminating recombination-defective oocytes. Brca1 knockout (KO) rescues the survival of Dmc1 KO oocytes far more efficiently than removing CHK2, a vital component of the DNA damage checkpoint in oocytes. Mechanistically, BRCA1 activates chromosome asynapsis checkpoint by promoting ATR activity at unsynapsed chromosome axes in Dmc1 KO oocytes. Moreover, Brca1 KO also rescues the survival of asynaptic Spo11 KO oocytes. Collectively, our study not only unveils an unappreciated role of chromosome asynapsis in eliminating recombination-defective oocytes but also reveals the dual functions of BRCA1 in safeguarding oocyte genome integrity.

Blood Lead Level as Marker of Increased Risk of Ovarian Cancer in BRCA1 Carriers.

BRCA1 mutations substantially elevate the risks of breast and ovarian cancer. Various modifiers, including environmental factors, can influence cancer risk. Lead, a known carcinogen, has been associated with various cancers, but its impact on BRCA1 carriers remains unexplored. A cohort of 989 BRCA1 mutation carriers underwent genetic testing at the Pomeranian Medical University, Poland. Blood lead levels were measured using inductively coupled plasma mass spectrometry. Each subject was assigned to a category based on their tertile of blood lead. Cox regression analysis was used to assess cancer risk associations. Elevated blood lead levels (>13.6 µg/L) were associated with an increased risk of ovarian cancer (univariable: HR = 3.33; 95% CI: 1.23-9.00; p = 0.02; multivariable: HR = 2.10; 95% CI: 0.73-6.01; p = 0.17). No significant correlation was found with breast cancer risk. High blood lead levels are associated with increased risk of ovarian cancer in BRCA1 carriers, suggesting priority for preventive salpingo-oophorectomy. Potential risk reduction strategies include detoxification. Validation in diverse populations and exploration of detoxification methods for lowering lead levels are required.

Clinicopathological characteristics and BRCA1/BRCA2 pathogenic variants of patients with breast cancer.

Although BRCA genes are well-known breast cancer genes, the clinicopathological features of breast cancer patients carrying BRCA1/2 pathogenic variants have not been adequately defined. The goals of this study were to determine the distribution of BRCA1/2 variants in the Turkish population and its correlation with clinicopathological features. Clinical data of 151 women who underwent BRCA1/2 gene testing at Mersin University Medical Faculty Hospital between 2016 and 2019 were retrospectively analyzed. BRCA1/2 variants were detected as pathogenic (n = 11), variants of uncertain significance (n = 5), likely benign (n = 3), and benign (n = 81) in breast cancer cases. The BRCA1/2 pathogenic variant carriers had a higher histological grade, rate of triple- negative type, Ki-67 proliferation index, and rate of no special type carcinoma than the group without mutation (p = 0.03, 0.01, 0.04, and 0.02 respectively). We analyzed the distribution of variants we detected in women living in our region and found that pathogenic variants in patients with breast cancer were associated with high histological grade, triple-negative type, high Ki-67 proliferation index, and histological type. Studies in diverse populations are needed to establish a clinicopathological relationship with variants more easily.

Epithelial ovarian cancer and brain metastases: might the BRCA status, PARP inhibitor administration, and surgical treatment impact the survival?

OBJECTIVE: To evaluate disease characteristics and survival according to BRCA status, administration of poly-(ADP-ribose) polymerase inhibitors (PARPi), and surgery in patients with ovarian cancer and brain metastases. METHODS: This is a monocentric retrospective cohort of patients with ovarian cancer and brain metastases treated between 2000 and 2021. Data were collected by a retrospective review of medical records and analyzed according to: (1) BRCA mutation; (2) PARPi before and after brain metastases; (3) surgery for brain metastases. RESULTS: Eighty-five patients with ovarian cancer and brain metastasis and known BRCA status (31 BRCA mutated (BRCAm), 54 BRCA wild-type (BRCAwt)) were analyzed. Twenty-two patients had received PARPi before brain metastases diagnosis (11 BRCAm, 11 BRCAwt) and 12 after (8 BRCAm, 4 BRCAwt). Brain metastases occurred >1 year later in patients who had received previous PARPi. Survival was longer in the BRCAm group (median post-brain metastasis survival: BRCAm 23 months vs BRCAwt 8 months, p=0.0015). No differences were found based on BRCA status analyzing the population who did not receive PARPi after brain metastasis (median post-brain metastasis survival: BRCAm 8 months vs BRCAwt 8 months, p=0.31). In the BRCAm group, survival was worse in patients who had received previous PARPi (median post-brain metastasis survival: PARPi before, 7 months vs no-PARPi before, 24 months, p=0.003). If PARPi was administered after brain metastases, survival of the overall population improved (median post-brain metastasis survival: PARPi after, 46 months vs no-PARPi after, 8 months, p=0.00038).In cases of surgery for brain metastases, the prognosis seemed better (median post-brain metastasis survival: surgery 13 months vs no-surgery 8 months, p=0.036). Three variables were significantly associated with prolonged survival at multivariate analysis: BRCA mutation, multimodal treatment, and ≤1 previous chemotherapy line. CONCLUSIONS: BRCA mutations might impact brain metastasis occurrence and lead to better outcomes. In a multimodal treatment, surgery seems to affect survival even in cases of extracranial disease. PARPi use should be considered as it seems to prolong survival if administered after brain metastasis.

Genomic characterization reveals distinct mutational landscapes and therapeutic implications between different molecular subtypes of triple-negative breast cancer.

Triple-negative breast cancer (TNBC) has high heterogeneity, poor prognosis, and limited treatment success. Recently, an immunohistochemistry-based surrogate classification for the "Fudan University Shanghai Cancer Center (FUSCC) subtyping" has been developed and is considered more suitable for clinical application. Seventy-one paraffin-embedded sections of surgically resected TNBC were classified into four molecular subtypes using the IHC-based surrogate classification. Genomic analysis was performed by targeted next-generation sequencing and the specificity of the subtypes was explored by bioinformatics, including survival analysis, multivariate Cox regression, pathway enrichment, Pyclone analysis, mutational signature analysis and PHIAL analysis. AKT1 and BRCA1 mutations were identified as independent prognostic factors in TNBC. TNBC molecular subtypes encompass distinct genomic landscapes that show specific heterogeneities. The luminal androgen receptor (LAR) subtype was associated with mutations in PIK3CA and PI3K pathways, which are potentially sensitive to PI3K pathway inhibitors. The basal-like immune-suppressed (BLIS) subtype was characterized by high genomic instability and the specific possession of signature 19 while patients in the immunomodulatory (IM) subtype belonged to the PD-L1 ≥ 1% subgroup with enrichment in Notch signaling, suggesting a possible benefit of immune checkpoint inhibitors and Notch inhibitors. Moreover, mesenchymal-like (MES) tumors displayed enrichment in the receptor tyrosine kinase (RTK)-RAS pathway and potential sensitivity to RTK pathway inhibitors. The findings suggest potential treatment targets and prognostic factors, indicating the possibility of TNBC stratified therapy in the future.

The role of germline BRCA1 & BRCA2 mutations in familial pancreatic cancer: A systematic review and meta-analysis.

BACKGROUND: Familial Pancreatic Cancer (FPC) presents a notable risk, with 3-10% of pancreatic adenocarcinoma cases having a family history. Studies link FPC to syndromes like HBOC, suggesting BRCA1/BRCA2 mutations play a role. BRCA gene functions in DNA repair impact FPC management, influencing sensitivity to therapies like PARP inhibitors. Identifying mutations not only aids FPC treatment but also reveals broader cancer risks. However, challenges persist in selectively applying genetic testing due to cost constraints. This Systematic Review focuses on BRCA1/BRCA2 significance in FPC, diagnostic criteria, prognostic value, and limitations. METHOD: Original articles published from 2013 to January 2023 were sourced from databases such as Scopus, PubMed, ProQuest, and ScienceDirect. Inclusion criteria comprised observational cohort or diagnostic studies related to the role of BRCA1/2 mutation in correlation to familial pancreatic cancer (FPC), while article reviews, narrative reviews, and non-relevant content were excluded. The assessment of bias used ROBINS-I, and the results were organized using PICOS criteria in a Google spreadsheet table. The systematic review adhered to the PRISMA 2020 checklist. RESULT: We analyzed 9 diagnostic studies encompassing 1325 families and 4267 patients from Italy, USA, and Poland. Despite the limitation of limited homogenous PICO studies, our findings effectively present evidence. BRCA1/2 demonstrates benefits in detecting first-degree relatives FPC involvement with 2.26-10 times higher risk. These mutation findings also play an important role since with the BRCA1/2 targeted therapy, Poly-ADP Ribose Polymerase inhibitors (PARP) may give better outcomes of FPC treatment. Analysis of BRCA1 and BRCA2 administration's impact on odds ratio (OR) based on six and five studies respectively. BRCA1 exhibited non-significant effects (OR = 1.26, P = 0.51), while BRCA2 showed significance (OR = 1.68, P = 0.04). No heterogeneity observed, indicating consistent results. Further research on BRCA1 is warranted. CONCLUSION: Detecting the BRCA1/2 mutation gene offers numerous advantages, particularly in its correlation with FPC. For diagnostic and prognostic purposes, testing is strongly recommended for first-degree relatives, who face a significantly higher risk (2.26-10 times) of being affected. Additionally, FPC patients with identified BRCA1/2 mutations exhibit a more favorable prognosis compared to the non-mutated population. This is attributed to the availability of targeted BRCA1/2 therapy, which maximizes treatment outcomes.

Exploration of poly (ADP-ribose) polymerase inhibitor resistance in the treatment of BRCA1/2-mutated cancer.

Breast cancer susceptibility 1/2 (BRCA1/2) genes play a crucial role in DNA damage repair, yet mutations in these genes increase the susceptibility to tumorigenesis. Exploiting the synthetic lethality mechanism between BRCA1/2 mutations and poly(ADP-ribose) polymerase (PARP) inhibition has led to the development and clinical approval of PARP inhibitor (PARPi), representing a milestone in targeted therapy for BRCA1/2 mutant tumors. This approach has paved the way for leveraging synthetic lethality in tumor treatment strategies. Despite the initial success of PARPis, resistance to these agents diminishes their efficacy in BRCA1/2-mutant tumors. Investigations into PARPi resistance have identified replication fork stability and homologous recombination repair as key factors sensitive to PARPis. Additionally, studies suggest that replication gaps may also confer sensitivity to PARPis. Moreover, emerging evidence indicates a correlation between PARPi resistance and cisplatin resistance, suggesting a potential overlap in the mechanisms underlying resistance to both agents. Given these findings, it is imperative to explore the interplay between replication gaps and PARPi resistance, particularly in the context of platinum resistance. Understanding the impact of replication gaps on PARPi resistance may offer insights into novel therapeutic strategies to overcome resistance mechanisms and enhance the efficacy of targeted therapies in BRCA1/2-mutant tumors.

Epigenetic editing of BRCA1 promoter increases cisplatin and olaparib sensitivity of ovarian cancer cells.

Drug resistance is the primary contributor to the high mortality rate of ovarian cancer (OC). The loss of BRCA1/2 function is linked to drug sensitivity in OC cells. The aim of this study is to enhance the drug sensitivity of OC cells by inducing BRCA1 dysfunction through promoter epigenetic editing. Epigenetic regulatory regions within the BRCA1 promoter, affecting gene expression, were initially discerned through analysis of clinical samples. Subsequently, we designed and rigorously validated epigenetic editing tools. Ultimately, we evaluated the cisplatin and olaparib sensitivity of the OC cells after editing. The BRCA1 promoter contains two CpG-rich regions, with methylation of the region covering the transcription start site (TSS) strongly correlating with transcription and influencing OC development, prognosis, and homologous recombination (HR) defects. Targeting this region in OC cells using our designed epigenetic editing tools led to substantial and persistent DNA methylation changes, accompanied by significant reductions in H3K27ac histone modifications. This resulted in a notable suppression of BRCA1 expression and a decrease in HR repair capacity. Consequently, edited OC cells exhibited heightened sensitivity to cisplatin and olaparib, leading to increased apoptosis rates. Epigenetic inactivation of the BRCA1 promoter can enhance cisplatin and olaparib sensitivity of OC cells through a reduction in HR repair capacity, indicating the potential utility of epigenetic editing technology in sensitization therapy for OC.

Evolved histone tail regulates 53BP1 recruitment at damaged chromatin.

The master DNA damage repair histone protein, H2AX, is essential for orchestrating the recruitment of downstream mediator and effector proteins at damaged chromatin. The phosphorylation of H2AX at S139, γH2AX, is well-studied for its DNA repair function. However, the extended C-terminal tail is not characterized. Here, we define the minimal motif on H2AX for the canonical function in activating the MDC1-RNF8-RNF168 phosphorylation-ubiquitination pathway that is important for recruiting repair proteins, such as 53BP1 and BRCA1. Interestingly, H2AX recruits 53BP1 independently from the MDC1-RNF8-RNF168 pathway through its evolved C-terminal linker region with S139 phosphorylation. Mechanistically, 53BP1 recruitment to damaged chromatin is mediated by the interaction between the H2AX C-terminal tail and the 53BP1 Oligomerization-Tudor domains. Moreover, γH2AX-linker mediated 53BP1 recruitment leads to camptothecin resistance in H2AX knockout cells. Overall, our study uncovers an evolved mechanism within the H2AX C-terminal tail for regulating DNA repair proteins at damaged chromatin.

Loss of POLE3-POLE4 unleashes replicative gap accumulation upon treatment with PARP inhibitors.

The advent of PARP inhibitors (PARPis) has profoundly changed the treatment landscape of BRCA1/BRCA2-mutated cancers. Despite this, the development of resistance to these compounds has become a major challenge. Hence, a detailed understanding of the mechanisms underlying PARPi sensitivity is crucially needed. Here, we show that loss of the POLE3-POLE4 subunits of DNA polymerase epsilon (Polε) strongly sensitizes cancer cells to PARPis in a Polε level-independent manner. Loss of POLE3-POLE4 is not associated with defective RAD51 foci formation, excluding a major defect in homologous recombination. On the contrary, treatment with PARPis triggers replicative gap accumulation in POLE3-POLE4 knockout (KO) cells in a PRIMPOL-dependent manner. In addition to this, the loss of POLE3-POLE4 further sensitizes BRCA1-silenced cells to PARPis. Importantly, the knockdown of 53BP1 does not rescue PARPi sensitivity in POLE3-POLE4 KO cells, bypassing a common PARPi resistance mechanism and outlining a potential strategy to sensitize cancer cells to PARPis.

Breast cancer screening in BRCA1/2 pathogenic sequence variant carriers during pregnancy and lactation.

OBJECTIVES: Women harboring germline BRCA1/BRCA2 pathogenic sequence variants (PSVs) are at an increased risk for breast cancer. There are no established guidelines for screening during pregnancy and lactation in BRCA carriers. The aim of this study was to evaluate the utility of whole-breast ultrasound (US) screening in pregnant and lactating BRCA PSV carriers. METHODS: Data were retrospectively collected from medical records of BRCA PSV carriers between 2014 and 2020, with follow-up until 2021. Associations between imaging intervals, number of examinations performed and pregnancy-associated breast cancers (PABCs) were examined. PABCs and cancers diagnosed at follow-up were evaluated and characteristics were compared between the two groups. RESULTS: Overall 212 BRCA PSV carriers were included. Mean age was 33.6 years (SD 3.93, range 25-43 years). During 274 screening periods at pregnancy and lactation, eight (2.9 %) PABCs were diagnosed. An additional eight cancers were diagnosed at follow-up. Three out of eight (37.5 %) PABCs were diagnosed by US, whereas clinical breast examination (n = 3), mammography (n = 1) and MRI (n = 1) accounted for the other PACB diagnoses. One PABC was missed by US. The interval from negative imaging to cancer diagnosis was significantly shorter for PABCs compared with cancers diagnosed at follow-up (3.96 ± 2.14 vs. 11.2 ± 4.46 months, P = 0.002). CONCLUSION: In conclusion, pregnant BRCA PSV carriers should not delay screening despite challenges like altered breast tissue and hesitancy towards mammography. If no alternatives exist, whole-breast ultrasound can be used. For lactating and postpartum women, a regular screening routine alternating between mammography and MRI is recommended.

H2AX promotes replication fork degradation and chemosensitivity in BRCA-deficient tumours.

Histone H2AX plays a key role in DNA damage signalling in the surrounding regions of DNA double-strand breaks (DSBs). In response to DNA damage, H2AX becomes phosphorylated on serine residue 139 (known as γH2AX), resulting in the recruitment of the DNA repair effectors 53BP1 and BRCA1. Here, by studying resistance to poly(ADP-ribose) polymerase (PARP) inhibitors in BRCA1/2-deficient mammary tumours, we identify a function for γH2AX in orchestrating drug-induced replication fork degradation. Mechanistically, γH2AX-driven replication fork degradation is elicited by suppressing CtIP-mediated fork protection. As a result, H2AX loss restores replication fork stability and increases chemoresistance in BRCA1/2-deficient tumour cells without restoring homology-directed DNA repair, as highlighted by the lack of DNA damage-induced RAD51 foci. Furthermore, in the attempt to discover acquired genetic vulnerabilities, we find that ATM but not ATR inhibition overcomes PARP inhibitor (PARPi) resistance in H2AX-deficient tumours by interfering with CtIP-mediated fork protection. In summary, our results demonstrate a role for H2AX in replication fork biology in BRCA-deficient tumours and establish a function of H2AX separable from its classical role in DNA damage signalling and DSB repair.