A role for Brca1 in chromosome end maintenance

Brca2(p.T1942fs/+) dissipates ovarian reserve in rats through oxidative stress in follicular granulosa cells

Pathogenic variants of BRCA1/2 constitute hereditary breast and ovarian cancer (HBOC) syndrome, and BRCA1/2 mutant is a risk for various cancers. Whereas the clinical guideline for HBOC patients has been organized for the therapy and prevention of cancer, there is no recommendation on the female reproductive discipline. Indeed, the role of BRCA1/2 pathogenic variants in ovarian reserve has not been established due to the deficiency of appropriate animal models. Here, we used a rat model of Brca2(p.T1942fs/+) mutant of Sprague-Dawley strain with CRISPR-Cas9 editing to evaluate ovarian reserve in females. Fertility and ovarian follicles were evaluated and anti-Müllerian hormone (AMH) was measured at 8-32 weeks of age with a comparison between the wild-type and the mutant rats (MUT). MUT revealed a significantly smaller number of deliveries with fewer total pups. Furthermore, MUT showed a significant decrease in primordial follicles at 20 weeks and a low AMH level at 28 weeks. RNA-sequencing of the ovary at 10 weeks detected acceleration of the DNA damage repair pathway, which was accompanied by oxidative stress-induced DNA double-strand breaks, a decrease in PTEN, and an increase in mTOR in follicular granulosa cells. In conclusion, Brca2(p.T1942fs/+) dissipates primordial follicles via early activation of granulosa cells through oxidative stress, leading to earlier termination of fertility.

MicroRNA networks linked with BRCA1/2, PTEN, and common genes for Alzheimer's disease and breast cancer share highly enriched pathways that may unravel targets for the AD/BC comorbidity treatment

MicroRNAs (miRNAs) are involved in the regulation of various cellular processes including pathological conditions. MiRNA networks have been extensively researched in age-related degenerative diseases, such as cancer, Alzheimer's disease (AD), and heart failure. Thus, miRNA has been studied from different approaches, in vivo, in vitro, and in silico including miRNA networks. Networks linking diverse biomedical entities unveil information not readily observable by other means. This work focuses on biological networks related to Breast cancer susceptibility 1 (BRCA1) in AD and breast cancer (BC). Using various bioinformatics approaches, we identified subnetworks common to AD and BC that suggest they are linked. According to our results, miR-107 was identified as a potentially good candidate for both AD and BC treatment (targeting BRCA1/2 and PTEN in both diseases), accompanied by miR-146a and miR-17. The analysis also confirmed the involvement of the miR-17-92 cluster, and miR-124-3p, and highlighted the importance of poorly researched miRNAs such as mir-6785 mir-6127, mir-6870, or miR-8485. After filtering the in silico analysis results, we found 49 miRNA molecules that modulate the expression of at least five genes common to both BC and AD. Those 49 miRNAs regulate the expression of 122 genes in AD and 93 genes in BC, from which 26 genes are common genes for AD and BC involved in neuron differentiation and genesis, cell differentiation and migration, regulation of cell cycle, and cancer development. Additionally, the highly enriched pathway was associated with diabetic complications, pointing out possible interplay among molecules underlying BC, AD, and diabetes pathology.

BRCA, infertility, and fertility preservation: a review for counseling

BRCA mutations as a triggering factor in breast cancer have been reported to result in fertility problems and oocyte aging in young patients with cancer diagnosis. These patients are concerned about fertility problems and family planning before undergoing treatment modalities that may result in infertility. In this review, we conducted analysis of the literature on the association between BRCA mutations and infertility, possible fertility preservation options, and their safety and tried to gather results from different disciplines and points of view on the matter. Our aim is to provide a general summary of recent studies to provide further insight on the matter for counseling BRCA mutation carriers on fertility preservation methods and their implications.

Role of Xeroderma pigmentosum D (XPD) protein in genome maintenance in human cells under oxidative stress

Xeroderma pigmentosum D (XPD) protein plays a pivotal role in the nucleotide excision repair pathway. XPD unwinds the local area of the damaged DNA by virtue of constituting transcription factor II H (TFIIH) and is important not only for repair but also for basal transcription. Although cells deficient in XPD have shown to be defective in oxidative base-lesion repair, the effects of the oxidative assault on primary fibroblasts from patients suffering from Xeroderma Pigmentosum D have not been fully explored. Therefore, we sought to investigate the role of XPD in oxidative DNA damage-repair by treating primary fibroblasts derived from a patient suffering from Xeroderma Pigmentosum D, with hydrogen peroxide. Our results show dose-dependent increase in genotoxicity with minimal effect on cytotoxicity with H₂O₂ in XPD deficient cells compared to control cells. XPD deficient cells displayed increased susceptibility and reduced repair capacity when subjected to DNA damage induced by oxidative stress. XPD deficient fibroblasts exhibited increased telomeric loss after H₂O₂ treatment. In addition, we demonstrated that chronic oxidative stress induced accelerated premature senescence characteristics. Gene expression profiling revealed alterations in genes involved in transcription and nucleotide metabolisms, as well as in cellular and cell cycle processes in a more significant way than in other pathways. This study highlights the role of XPD in the repair of oxidative stress and telomere maintenance. Lack of functional XPD seems to increase the susceptibility of oxidative stress-induced genotoxicity while retaining cell viability posing as a potential cancer risk factor of Xeroderma Pigmentosum D patients.

The fellowship of the RING: BRCA1, its partner BARD1 and their liaison in DNA repair and cancer

The breast cancer type 1 susceptibility protein (BRCA1) and its partner - the BRCA1-associated RING domain protein 1 (BARD1) - are key players in a plethora of fundamental biological functions including, among others, DNA repair, replication fork protection, cell cycle progression, telomere maintenance, chromatin remodeling, apoptosis and tumor suppression. However, mutations in their encoding genes transform them into dangerous threats, and substantially increase the risk of developing cancer and other malignancies during the lifetime of the affected individuals. Understanding how BRCA1 and BARD1 perform their biological activities therefore not only provides a powerful mean to prevent such fatal occurrences but can also pave the way to the development of new targeted therapeutics. Thus, through this review work we aim at presenting the major efforts focused on the functional characterization and structural insights of BRCA1 and BARD1, per se and in combination with all their principal mediators and regulators, and on the multifaceted roles these proteins play in the maintenance of human genome integrity.

Shaping the BRCAness mutational landscape by alternative double-strand break repair, replication stress and mitotic aberrancies

Tumours with mutations in the BRCA1/BRCA2 genes have impaired double-stranded DNA break repair, compromised replication fork protection and increased sensitivity to replication blocking agents, a phenotype collectively known as 'BRCAness'. Tumours with a BRCAness phenotype become dependent on alternative repair pathways that are error-prone and introduce specific patterns of somatic mutations across the genome. The increasing availability of next-generation sequencing data of tumour samples has enabled identification of distinct mutational signatures associated with BRCAness. These signatures reveal that alternative repair pathways, including Polymerase θ-mediated alternative end-joining and RAD52-mediated single strand annealing are active in BRCA1/2-deficient tumours, pointing towards potential therapeutic targets in these tumours. Additionally, insight into the mutations and consequences of unrepaired DNA lesions may also aid in the identification of BRCA-like tumours lacking BRCA1/BRCA2 gene inactivation. This is clinically relevant, as these tumours respond favourably to treatment with DNA-damaging agents, including PARP inhibitors or cisplatin, which have been successfully used to treat patients with BRCA1/2-defective tumours. In this review, we aim to provide insight in the origins of the mutational landscape associated with BRCAness by exploring the molecular biology of alternative DNA repair pathways, which may represent actionable therapeutic targets in in these cells.

BRCA-related ATM-mediated DNA double-strand break repair and ovarian aging

BACKGROUND

Oocyte aging has significant clinical consequences, and yet no treatment exists to address the age-related decline in oocyte quality. The lack of progress in the treatment of oocyte aging is due to the fact that the underlying molecular mechanisms are not sufficiently understood. BRCA1 and 2 are involved in homologous DNA recombination and play essential roles in ataxia telangiectasia mutated (ATM)-mediated DNA double-strand break (DSB) repair. A growing body of laboratory, translational and clinical evidence has emerged within the past decade indicating a role for BRCA function and ATM-mediated DNA DSB repair in ovarian aging.

OBJECTIVE AND RATIONALE

Although there are several competing or complementary theories, given the growing evidence tying BRCA function and ATM-mediated DNA DSB repair mechanisms in general to ovarian aging, we performed this review encompassing basic, translational and clinical work to assess the current state of knowledge on the topic. A clear understanding of the mechanisms underlying oocyte aging may result in targeted treatments to preserve ovarian reserve and improve oocyte quality.

SEARCH METHODS

We searched for published articles in the PubMed database containing key words, BRCA, BRCA1, BRCA2, Mutations, Fertility, Ovarian Reserve, Infertility, Mechanisms of Ovarian Aging, Oocyte or Oocyte DNA Repair, in the English-language literature until May 2019. We did not include abstracts or conference proceedings, with the exception of our own.

OUTCOMES

Laboratory studies provided robust and reproducible evidence that BRCA1 function and ATM-mediated DNA DSB repair, in general, weakens with age in oocytes of multiple species including human. In both women with BRCA mutations and BRCA-mutant mice, primordial follicle numbers are reduced and there is accelerated accumulation of DNA DSBs in oocytes. In general, women with BRCA1 mutations have lower ovarian reserves and experience earlier menopause. Laboratory evidence also supports critical role for BRCA1 and other ATM-mediated DNA DSB repair pathway members in meiotic function. When laboratory, translational and clinical evidence is considered together, BRCA-related ATM-mediated DNA DSB repair function emerges as a likely regulator of ovarian aging. Moreover, DNA damage and repair appear to be key features in chemotherapy-induced ovarian aging.

WIDER IMPLICATIONS

The existing data suggest that the BRCA-related ATM-mediated DNA repair pathway is a strong candidate to be a regulator of oocyte aging, and the age-related decline of this pathway likely impairs oocyte health. This knowledge may create an opportunity to develop targeted treatments to reverse or prevent physiological or chemotherapy-induced oocyte aging. On the immediate practical side, women with BRCA or similar mutations may need to be specially counselled for fertility preservation.

BRCA1/2 gene mutations do not affect the capacity of oocytes from breast cancer candidates for fertility preservation to mature in vitro

STUDY QUESTION

Are the maturation rates of oocytes recovered from small antral follicles different between breast cancer patients presenting with or without a BRCA 1/2 gene mutation?

SUMMARY ANSWER

BRCA 1/2 gene mutations do not affect the capacity of oocytes from breast cancer candidates for fertility preservation to mature in vitro.

WHAT IS KNOWN ALREADY

Mutations in the BRCA1 and BRCA2 genes are associated with an increased risk for developing breast and ovarian cancer. Controversy exists about fertility and ovarian reserve in BRCA mutation carriers. Studies suggest that these patients may have low ovarian reserve and poor response to ovarian stimulation. The impaired ability of the mutated BRCA gene to repair double-strand breaks in DNA may prompt oocyte aging, apoptosis and meiotic errors. IVM of oocytes retrieved at germinal vesicle stage, followed by vitrification of metaphase II (MII) oocytes has recently emerged as an option for young women seeking fertility preservation, when ovarian stimulation is unfeasible.

STUDY DESIGN, SIZE, DURATION

Retrospective cohort study involving 329 breast cancer candidates for fertility preservation using IVM between January 2014 and December 2017.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Inclusion criteria were: age 18-40 years; two ovaries present; no history of chemotherapy; test for BRCA 1/2 mutations performed. Before immature oocyte retrieval, all follicles measuring 2-9 mm in diameter were precisely counted on both ovaries and serum anti-Müllerian hormone (AMH) was measured irrespective of the phase of the cycle. Number of cumulus oocyte complexes (COC) retrieved, maturation rate and number of MII oocytes cryopreserved were compared according to BRCA mutation status.

MAIN RESULTS AND THE ROLE OF CHANCE

Overall, BRCA-mutated women (n = 52) and BRCA-negative women (n = 277) were comparable in terms of age (31.7 ± 3.9 versus 32.3 ± 3.8 years, respectively, P = 0.3), BMI (23.4 ± 4.7 versus 22.6 ± 3.7 kg/m2, respectively, P = 0.3) and ovarian reserve tests (antral follicle count: 20.5 ± 11.4 versus 21.7 ± 12.1 follicles, P = 0.5; serum AMH levels: 3.6 ± 2.9 versus 4.1 ± 3.6 ng/ml, P = 0.3, respectively). The number of COCs retrieved did not differ significantly between both groups (8.9 ± 6.9 versus 9.9 ± 8.1 oocytes, P = 0.5). After similar IVM rates (67 ± 24 versus 62 ± 23%, P = 0.2), the number of MII oocytes cryopreserved was similar in patients presenting BRCA mutation or not (5.1 ± 3.8 versus 6.1 ± 5.1, P = 0.1, respectively).

LIMITATIONS, REASONS FOR CAUTION

Given the low incidence of the mutation, these preliminary findings should be confirmed by further multi-center studies.

WIDER IMPLICATIONS OF THE FINDINGS

Although BRCA mutations are known to alter DNA repair mechanism, it does not seem to impair oocyte capacity to mature in vitro.

STUDY FUNDING/COMPETING INTEREST(s)

None.

Navigating the body of literature assessing BRCA1/2 mutations and markers of ovarian function: a systematic review and meta-analysis

PURPOSE

Twelve percent of women in the USA will develop invasive breast cancer in their lifetime, and that risk increases to 80% if they carry a BRCA1 or BRCA2 mutation. BRCA1/2 mutations are thought to potentially affect ovarian reserve and/or fertility.

METHODS

PubMed and PubMed Central were searched for publications on ovarian reserve-related outcomes (i.e., AMH and response to controlled ovarian hyperstimulation (COH) protocols) that were reported in relation to BRCA1 and/or BRCA2 mutations from 1950 through May 2019. A meta-analysis was conducted to create forest plots and summary effect measures using Review Manager 5.3.

RESULTS

This article reviews the 16 qualifying publications. There were several fundamental methodological differences in the study designs and outcome details reported in AMH studies. Summary statistics found no difference in AMH levels between BRCA1/2+ women as compared with controls (Z overall test effects p ≥ 0.45). Regarding responses to COH, there were overall non-significantly fewer total and mature numbers of oocytes retrieved in BRCA1/2+ cases as compared with controls (meta-analysis Z overall test effects p ≥ 0.40).

CONCLUSIONS

While the summary measures indicate no significant differences in AMH levels between BRCA1/2+ cases and controls, readers should be aware that there are significant methodological differences in the AMH reports. Additionally, the response to COH protocols does not seem to be significantly lower in BRCA1/2 mutation carriers in the existing literature. Continued research on both of these clinical parameters would be beneficial for patient counseling.

Investigation into the presence and functional significance of proinsulin C-peptide in the female germline†

Diabetes is associated with poor oocyte quality and the dysregulation of ovarian function and is thus a leading contributor to the increasing prevalence of female reproductive pathologies. Accordingly, it is well-established that insulin fulfills a key role in the regulation of several facets of female reproduction. What remains less certain is whether proinsulin C-peptide, which has recently been implicated in cellular signaling cascades, holds a functional role in the female germline. In the present study, we examined the expression of insulin, C-peptide, and its purported receptor; GPR146, within the mouse ovary and oocyte. Our data establish the presence of abundant C-peptide within follicular fluid and raise the prospect that this bioactive peptide is internalized by oocytes in a G-protein coupled receptor-dependent manner. Further, our data reveal that internalized C-peptide undergoes pronounced subcellular relocalization from the ooplasm to the pronuclei postfertilization. The application of immunoprecipitation analysis and mass spectrometry identified breast cancer type 2 susceptibility protein (BRCA2), the meiotic resumption/DNA repair protein, as a primary binding partner for C-peptide within the oocyte. Collectively, these findings establish a novel accumulation profile for C-peptide in the female germline and provide the first evidence for an interaction between C-peptide and BRCA2. This interaction is particularly intriguing when considering the propensity for oocytes from diabetic women to experience aberrant meiotic resumption and perturbation of traditional DNA repair processes. This therefore provides a clear imperative for further investigation of the implications of dysregulated C-peptide production in these individuals.

Anti-Mullerian hormone levels in female cancer patients of reproductive age in Indonesia: A cross-sectional study

Background: Efforts in reproductive preservation for cancer patients have become one of the important aspects of cancer management. In fact, decline in reproductive function is known to occur after exposure to anti-cancer treatments. Measuring anti-Müllerian hormone (AMH) levels is known to be the best parameter in predicting ovarian reserves, which indicates reproductive function. In total, 68% of cancer survivors of reproductive age who underwent anti-cancer treatments suffer from infertility. Meanwhile, ovarian reserves also decrease with increasing age. There is ongoing debate on whether the ovarian reserves of cancer patients could be reduced long before exposure to anti-cancer therapy. Therefore, it is important to know whether ovarian reserves in cancer patients decrease before or after anti-cancer therapy. This can help predict the reproductive function in such cases and the effectiveness of ovarian preservation efforts. Methods: A cross-sectional study was conducted, comparing the AMH levels of 44 female cancer patients of reproductive age before cancer therapy, to 44 non-cancer patients of reproductive age (age matched) . The biological ages from both groups were adjusted using the Indonesian Kalkulator of Oocytes. Results: The median age in both groups was 28 years old. The AMH levels in the cancer group were found to be significantly lower in contrast to those in the non-cancer group (1.11 [0.08-4.65] ng/ml vs. 3.99 [1.19- 8.7]; p- value <0.001). Therefore, the biological age in the cancer group was 10 years older than that of the non-cancer group, indicating that ovarian aging occurs earlier in cancer patients. Conclusions: AMH levels of cancer patients of reproductive age were already reduced before cancer therapy, given an older biological age, in contrast to that of the non-cancer patients. Proper counseling and implementation of fertility-preserving methods is highly recommended in this group of patients.

Anti-Mullerian hormone levels in female cancer patients of reproductive age in Indonesia: A cross-sectional study

Background: Efforts in reproductive preservation for cancer patients have become one of the important aspects of cancer management. In fact, decline in reproductive function is known to occur after exposure to anti-cancer treatments. Measuring anti-Müllerian hormone (AMH) levels is known to be the best parameter in predicting ovarian reserves, which indicates reproductive function. In total, 68% of cancer survivors of reproductive age who underwent anti-cancer treatments suffer from infertility. Meanwhile, ovarian reserves also decrease with increasing age. There is ongoing debate on whether the ovarian reserves of cancer patients could be reduced long before exposure to anti-cancer therapy. Therefore, it is important to know whether ovarian reserves in cancer patients decrease before or after anti-cancer therapy. This can help predict the reproductive function in such cases and the effectiveness of ovarian preservation efforts. Methods: A cross-sectional study was conducted, comparing the AMH levels of 44 female cancer patients of reproductive age before cancer therapy, to 44 non-cancer patients of reproductive age (age matched) . The biological ages from both groups were adjusted using the Indonesian Kalkulator of Oocytes. Results: The median age in both groups was 28 years old. The AMH levels in the cancer group were found to be significantly lower in contrast to those in the non-cancer group (1.11 [0.08-4.65] ng/ml vs. 3.99 [1.19- 8.7]; p- value <0.001). Therefore, the biological age in the cancer group was 10 years older than that of the non-cancer group, indicating that ovarian aging occurs earlier in cancer patients. Conclusions: AMH levels of cancer patients of reproductive age were already reduced before cancer therapy, given an older biological age, in contrast to that of the non-cancer patients. Proper counseling and implementation of fertility-preserving methods is highly recommended in this group of patients.

Anti-Mullerian hormone levels in female cancer patients of reproductive age in Indonesia: A cross-sectional study

Background: Efforts in reproductive preservation for cancer patients have become one of the important aspects of cancer management. In fact, decline in reproductive function is known to occur after exposure to anti-cancer treatments. Measuring anti-Müllerian hormone (AMH) levels is known to be the best parameter in predicting ovarian reserves, which indicates reproductive function. In total, 68% of cancer survivors of reproductive age who underwent anti-cancer treatments suffer from infertility. Meanwhile, ovarian reserves also decrease with increasing age. There is ongoing debate on whether the ovarian reserves of cancer patients could be reduced long before exposure to anti-cancer therapy. Therefore, it is important to know whether ovarian reserves in cancer patients decrease before or after anti-cancer therapy. This can help predict the reproductive function in such cases and the effectiveness of ovarian preservation efforts. Methods: A cross-sectional study was conducted, comparing the AMH levels of 44 female cancer patients of reproductive age before cancer therapy, to 44 non-cancer patients of reproductive age (age matched) . The AMH was determined from blood.The biological ages from both groups were adjusted using the Indonesian Kalkulator of Oocytes. Results: The median age in both groups was 28 years old. The AMH levels in the blood of the cancer group were found to be significantly lower in contrast to those in the non-cancer group (1.11 [0.08-4.65] ng/ml vs. 3.99 [1.19- 8.7]; p- value <0.001). Therefore, the biological age in the cancer group was 10 years older than that of the non-cancer group, indicating that ovarian aging occurs earlier in cancer patients. Conclusions: AMH levels of cancer patients of reproductive age were already reduced before cancer therapy, given an older biological age, in contrast to that of the non-cancer patients. Proper counseling and implementation of fertility-preserving methods is highly recommended in this group of patients.

Association of BRCA Mutations and Anti-müllerian Hormone Level in Young Breast Cancer Patients

Background: Several preclinical and clinical studies have suggested that BRCA-mutation carriers may have decreased ovarian reserve. However, data in this area are limited and inconsistent, especially in young breast cancer patients. Objective: This study evaluated the association between BRCA mutation status and serum anti-Müllerian hormone (AMH) level in young, reproductive-aged patients with breast cancer. Materials and Methods: Patients ≤ 40 years of age with breast cancer and who had known BRCA status and baseline serum AMH level at Samsung Medical Center, Seoul, Korea, were considered for inclusion. A total of 52 BRCA mutation carriers (27 BRCA1 and 25 BRCA2) and 264 non-carriers were selected for analyses. The serum level of AMH was compared according to presence of a BRCA mutation, and linear and logistic regression analyses were performed to evaluate the association between BRCA mutation and serum AMH level. Results: No difference was found in clinical characteristics between BRCA-mutation carriers and non-carriers. Subjects with any BRCA mutation had a significantly lower median AMH than those without a mutation (2.60 vs. 3.85 ng/mL, 32% reduction, P = 0.004). Linear regression analysis showed a significant negative association between BRCA mutation and AMH level. In addition, logistic regression demonstrated non-significantly increased odds of mutation carriers having AMH < 1.2 ng/mL. However, no difference was found between BRCA1/2 mutations. Conclusions: Breast cancer patients with BRCA mutation have significantly lower serum AMH level. Fertility preservation should be considered more aggressively in young breast cancer patients with BRCA mutation.

BRCA mutations and reproduction

Deleterious mutations in BRCA1 or BRCA2 genes have long been recognized as independent risk factors, mostly for breast and ovarian cancer. Numerous studies have evaluated the molecular processes involving these genes, the pathophysiology of BRCAness, follow up options and modes of prophylaxis. The fertility of BRCA carriers, however, has not been widely investigated. The aim of the present work is to review the literature pertaining to this issue.

RANKL/RANK: from bone loss to the prevention of breast cancer

RANK and RANKL, a receptor ligand pair belonging to the tumour necrosis factor family, are the critical regulators of osteoclast development and bone metabolism. Besides their essential function in bone, RANK and RANKL have also been identified as the key factors for the formation of a lactating mammary gland in pregnancy. Mechanistically, RANK and RANKL link the sex hormone progesterone with stem cell expansion and proliferation of mammary epithelial cells. Based on their normal physiology, RANKL/RANK control the onset of hormone-induced breast cancer through the expansion of mammary progenitor cells. Recently, we and others were able to show that RANK and RANKL are also critical regulators of BRCA1-mutation-driven breast cancer. Currently, the preventive strategy for BRCA1-mutation carriers includes preventive mastectomy, associated with wide-ranging risks and psychosocial effects. The search for an alternative non-invasive prevention strategy is therefore of paramount importance. As our work strongly implicates RANK and RANKL as key molecules involved in the initiation of BRCA1-associated breast cancer, we propose that anti-RANKL therapy could be a feasible preventive strategy for women carrying BRCA1 mutations, and by extension to other women with high risk of breast cancer.

Antimüllerian hormone levels are lower in BRCA2 mutation carriers

OBJECTIVE

To compare antimüllerian hormone (AMH) levels in women at high risk for hereditary breast and ovarian cancer compared with healthy low-risk control women.

DESIGN

Prospective cohort.

SETTING

Not applicable.

PATIENT(S)

Reproductive-age women with a uterus and both ovaries were analyzed in four groups: BRCA1 mutation carriers, BRCA2 carriers, BRCA-negative women, and low-risk controls.

INTERVENTION(S)

Self-collected dried blood spot.

MAIN OUTCOME MEASURE(S)

AMH levels.

RESULT(S)

One hundred ninety-five women were included: 55 BRCA1 carriers, 50 BRCA2 carriers, 26 BRCA negative women, and 64 low-risk controls. After adjusting for confounders, BRCA2 carriers had AMH levels that were 33% lower than control women and an increased odds of having AMH <1 ng/mL. BRCA1 carriers and BRCA-negative women had AMH levels similar to control women. When analysis was restricted to regularly menstruating women younger than 40 years of age, BRCA2 carriers continued to demonstrate significantly lower AMH levels and increased likelihood of low AMH. Also, in this restricted group, BRCA-negative women demonstrated AMH levels that were 42% lower than control women. No difference in AMH was observed for BRCA1 carriers.

CONCLUSION(S)

We observed significantly lower AMH levels among BRCA2 carriers compared with low-risk control women. These results were stable across all models. BRCA-negative women also had lower AMH values, but only in models restricted to young regularly menstruating women. In contrast to earlier analyses, BRCA1 carriers had AMH values that were similar to low-risk control women, but this may be due to differences in the population studied.

Tumor-treating fields elicit a conditional vulnerability to ionizing radiation via the downregulation of BRCA1 signaling and reduced DNA double-strand break repair capacity in non-small cell lung cancer cell lines

The use of tumor-treating fields (TTFields) has revolutionized the treatment of recurrent and newly diagnosed glioblastoma (GBM). TTFields are low-intensity, intermediate frequency, alternating electric fields that are applied to tumor regions and cells using non-invasive arrays. The predominant mechanism by which TTFields are thought to kill tumor cells is the disruption of mitosis. Using five non-small cell lung cancer (NSCLC) cell lines we found that there is a variable response in cell proliferation and cell killing between these NSCLC cell lines that was independent of p53 status. TTFields treatment increased the G2/M population, with a concomitant reduction in S-phase cells followed by the appearance of a sub-G1 population indicative of apoptosis. Temporal changes in gene expression during TTFields exposure was evaluated to identify molecular signaling changes underlying the differential TTFields response. The most differentially expressed genes were associated with the cell cycle and cell proliferation pathways. However, the expression of genes found within the BRCA1 DNA-damage response were significantly downregulated (P<0.05) during TTFields treatment. DNA double-strand break (DSB) repair foci increased when cells were exposed to TTFields as did the appearance of chromatid-type aberrations, suggesting an interphase mechanism responsible for cell death involving DNA repair. Exposing cells to TTFields immediately following ionizing radiation resulted in increased chromatid aberrations and a reduced capacity to repair DNA DSBs, which were likely responsible for at least a portion of the enhanced cell killing seen with the combination. These findings suggest that TTFields induce a state of ‘BRCAness' leading to a conditional susceptibility resulting in enhanced sensitivity to ionizing radiation and provides a strong rationale for the use of TTFields as a combined modality therapy with radiation or other DNA-damaging agents.

Analysis of alternative lengthening of telomere markers in BRCA1 defective cells

Telomeres are specialized structures responsible for the chromosome end protection. Previous studies have revealed that defective BRCA1 may lead to elevated telomere fusions and accelerated telomere shortening. In addition, BRCA1 associates with promyelocytic leukemia (PML) bodies in alternative lengthening of telomeres (ALTs) positive cells. We report here elevated recombination rates at telomeres in cells from human BRCA1 mutation carriers and in mouse embryonic stem cells lacking both copies of functional Brca1. An increased recombination rate at telomeres is one of the signs of ALT. To investigate this possibility further we employed the C-circle assay that identifies ALT unequivocally. Our results revealed elevated levels of ALT activity in Brca1 defective mouse cells. Similar results were obtained when the same cells were assayed for the presence of another ALT marker, namely the frequency of PML bodies. These results suggest that BRCA1 may act as a repressor of ALT. © 2016 The Authors Genes, Chromosomes & Cancer Published by Wiley Periodicals, Inc.

Identification of recurrent focal copy number variations and their putative targeted driver genes in ovarian cancer

BACKGROUND

Genomic regions with recurrent DNA copy number variations (CNVs) are generally believed to encode oncogenes and tumor suppressor genes (TSGs) that drive cancer growth. However, it remains a challenge to delineate the key cancer driver genes from the regions encoding a large number of genes.

RESULTS

In this study, we developed a new approach to CNV analysis based on spectral decomposition of CNV profiles into focal CNVs and broad CNVs. We performed an analysis of CNV data of 587 serous ovarian cancer samples on multiple platforms. We identified a number of novel focal regions, such as focal gain of ESR1, focal loss of LSAMP, prognostic site at 3q26.2 and losses of sub-telomere regions in multiple chromosomes. Furthermore, we performed network modularity analysis to examine the relationships among genes encoded in the focal CNV regions. Our results also showed that the recurrent focal gains were significantly associated with the known oncogenes and recurrent losses associated with TSGs and the CNVs had a greater effect on the mRNA expression of the driver genes than that of the non-driver genes.

CONCLUSIONS

Our results demonstrate that spectral decomposition of CNV profiles offers a new way of understanding the role of CNVs in cancer.

[Infertility and breast cancer: Is there a link? Updated review of the literature and meta-analysis]

The objective of this review was to assess the level of risk of breast cancer of patients consulting for infertility.

METHODS

Studies of cohorts and case-control were extracted from the Pubmed database from January 2000 until May 2015 through the following keywords: "infertility"; "endometriosis"; "polycystic ovary syndrome"; "breast cancer", "cancer risk". Eleven publications were finally selected after exclusion of publications dealing with infertility after breast cancer. Our meta-analysis, involving 10 of these publications, was performed using Review Manager software, Cochrane Collaboration, 2014. The results were calculated by etiology of infertility, polycystic ovary syndrome (PCOS) and endometriosis, as well as globally.

RESULTS

The analysis of these published epidemiological studies confirms that infertility is not a breast cancer risk factor, but the results are contradictory. Three studies have shown a significantly increased risk of breast cancer in a population of infertile women, while 7 others have not found this risk. These contradictions are due to the heterogeneity of the studies, the included populations, the follow-up periods and confounding factors. Our meta-analysis of the selected studies has not identified a significant association between infertility and breast cancer risk (1.05; 95% CI [0.96-1.16]). A subgroup analysis on endometriosis and PCOS showed no significant association either, with an OR of 1.02 (95% CI [0.87-1.19]) and 1.19 (95% CI [0.93-1.51]), respectively.

CONCLUSION

Infertility is not an identified risk factor for breast cancer. A message reassuring about a possible risk of infertility-related breast cancer should be given to these patients. Infertility is therefore not an indication of increased breast surveillance.

BRCA Mutations, DNA Repair Deficiency, and Ovarian Aging

Oocyte aging has a significant impact on reproductive outcomes both quantitatively and qualitatively. However, the molecular mechanisms underlying the age-related decline in reproductive success have not been fully addressed. BRCA is known to be involved in homologous DNA recombination and plays an essential role in double-strand DNA break repair. Given the growing body of laboratory and clinical evidence, we performed a systematic review on the current understanding of the role of DNA repair in human reproduction. We find that BRCA mutations negatively affect ovarian reserve based on convincing evidence from in vitro and in vivo results and prospective studies. Because decline in the function of the intact gene occurs at an earlier age, women with BRCA1 mutations exhibit accelerated ovarian aging, unlike those with BRCA2 mutations. However, because of the still robust function of the intact allele in younger women and because of the masking of most severe cases by prophylactic oophorectomy or cancer, it is less likely one would see an effect of BRCA mutations on fertility until later in reproductive age. The impact of BRCA2 mutations on reproductive function may be less visible because of the delayed decline in the function of normal BRCA2 allele. BRCA1 function and ataxia-telangiectasia-mutated (ATM)-mediated DNA repair may also be important in the pathogenesis of age-induced increase in aneuploidy. BRCA1 is required for meiotic spindle assembly, and cohesion function between sister chromatids is also regulated by ATM family member proteins. Taken together, these findings strongly suggest the implication of BRCA and DNA repair malfunction in ovarian aging.

Increased DNA damage and repair deficiency in granulosa cells are associated with ovarian aging in rhesus monkey

PURPOSE

Ovarian aging is closely tied to the decline in ovarian follicular reserve and oocyte quality. During the prolonged reproductive lifespan of the female, granulosa cells connected with oocytes play critical roles in maintaining follicle reservoir, oocyte growth and follicular development. We tested whether double-strand breaks (DSBs) and repair in granulosa cells within the follicular reservoir are associated with ovarian aging.

METHODS

Ovaries were sectioned and processed for epi-fluorescence microscopy, confocal microscopy, and immunohistochemistry. DNA damage was revealed by immunstaining of γH2AX foci and telomere damage by γH2AX foci co-localized with telomere associated protein TRF2. DNA repair was indicated by BRCA1 immunofluorescence.

RESULTS

DSBs in granulosa cells increase and DSB repair ability, characterized by BRCA1 foci, decreases with advancing age. γH2AX foci increase in primordial, primary and secondary follicles with advancing age. Likewise, telomere damage increases with advancing age. In contrast, BRCA1 foci in granulosa cells of primordial, primary and secondary follicles decrease with monkey age. BRCA1 positive foci in the oocyte nuclei also decline with maternal age.

CONCLUSIONS

Increased DSBs and reduced DNA repair in granulosa cells may contribute to ovarian aging. Discovery of therapeutics that targets these pathways might help maintain follicle reserve and postpone ovarian dysfunction with age.

[Breast and ovarian cancer due to BRCA1&2 hereditary cancer predisposition syndrome and reproduction: literature review]

INTRODUCTION

Germline mutations BRCA1&2 are responsible in women for breast and ovarian cancers that commonly occur at a young age: as such, there are strong interactions between the oncological risks and the events of reproductive life, pregnancy, breastfeeding, and management of infertility.

MATERIALS AND METHODS

A review of the international literature from the PubMed database was conducted, and recommendations of French health agencies were exposed. Published studies are case-control and cohort studies in the majority, with a low level of evidence.

RESULTS

Pregnancy and lactation have no effect on breast and ovaries or even decreases the risk. The sex ratio among patients carrying the mutation is in favor of girls. It is not observed more infertility in patients carrying a mutation despite a strong suspicion of premature ovarian failure, and infertility treatments do not increase breast and ovarian risk. There are ethical debates concerning the place of pre-natal diagnosis: both experts and concerned patients recommend a case-by-case analysis of the requests.

BRCA mutation carriers do not have compromised ovarian reserve

Controversy exists about the impact of BRCA1/2 mutations on female fertility. Previous studies are small or based on indirect parameters (eg, self-reported infertility), which depend on additional factors unrelated to true fertility potential. Most of the previous studies did not use strict fertility markers.

OBJECTIVE

The aim of this study is to evaluate the relation between carrying a BRCA1/2 mutation and fertility using the level of anti-müllerian hormone (AMH), which has been previously shown to be an accurate marker of ovarian reserve and fertility potential.

PATIENTS AND METHODS

Forty-one healthy BRCA1/2 mutation carriers, aged 26 to 40 years, attending a multidisciplinary breast and ovarian cancer surveillance clinic, were tested for AMH levels using a 2-site ELISA. Levels were compared with those of our general population and with well-established normograms of the general population.

RESULTS

The mean age of carriers was 33.2 years (26-39 years; SD, 3.99 years). The mean parity of carriers was 1.97 (0-7; SD, 1.49). All women carried at least 1 Ashkenazi Jewish founder mutation. The AMH levels for most carriers were in the reference range, 2.71 ± 0.59 ng/mL (approximately 50th percentile of normograms). These levels were similar to those in the control group, in which the AMH levels were 2.02 ± 0.12 ng/mL (P = 0.27).

CONCLUSIONS

The AMH levels of healthy BRCA1/2 mutation carriers are similar to those of noncarrier women matched for age; therefore, their ovarian reserve is comparable. This is the only study, to the best of our knowledge, that directly examines ovarian reserve in a relatively large group of carriers with an accurate marker. The results of this study may possibly give reassurance to female carriers concerning fertility potential.

Association of BLM and BRCA1 during Telomere Maintenance in ALT Cells

Fifteen percent of tumors utilize recombination-based alternative lengthening of telomeres (ALT) to maintain telomeres. The mechanisms underlying ALT are unclear but involve several proteins involved in homologous recombination including the BLM helicase, mutated in Bloom's syndrome, and the BRCA1 tumor suppressor. Cells deficient in either BLM or BRCA1 have phenotypes consistent with telomere dysfunction. Although BLM associates with numerous DNA damage repair proteins including BRCA1 during DNA repair, the functional consequences of BLM-BRCA1 association in telomere maintenance are not completely understood. Our earlier work showed the involvement of BRCA1 in different mechanisms of ALT, and telomere shortening upon loss of BLM in ALT cells. In order to delineate their roles in telomere maintenance, we studied their association in telomere metabolism in cells using ALT. This work shows that BLM and BRCA1 co-localize with RAD50 at telomeres during S- and G2-phases of the cell cycle in immortalized human cells using ALT but not in cells using telomerase to maintain telomeres. Co-immunoprecipitation of BRCA1 and BLM is enhanced in ALT cells at G2. Furthermore, BRCA1 and BLM interact with RAD50 predominantly in S- and G2-phases, respectively. Biochemical assays demonstrate that full-length BRCA1 increases the unwinding rate of BLM three-fold in assays using a DNA substrate that models a forked structure composed of telomeric repeats. Our results suggest that BRCA1 participates in ALT through its interactions with RAD50 and BLM.

Telomere shortening is associated with genetic anticipation in Chinese Von Hippel-Lindau disease families

Von Hippel-Lindau (VHL) disease is a rare autosomal dominant cancer syndrome. A phenomenon known as genetic anticipation has been documented in some hereditary cancer syndromes, where it was proved to relate to telomere shortening. Because studies of this phenomenon in VHL disease have been relatively scarce, we investigated anticipation in 18 Chinese VHL disease families. We recruited 34 parent-child patient pairs (57 patients) from 18 families with VHL disease. Onset age was defined as the age when any symptom or sign of VHL disease first appeared. Anticipation of onset age was analyzed by paired t test and the other two special tests (HV and RY2). Relative telomere length of peripheral leukocytes was measured in 29 patients and 325 healthy controls. Onset age was younger in child than in parent in 31 of the 34 parent-child pairs. Patients in the first generation had older onset age with longer age-adjusted relative telomere length, and those in the next generation had younger onset age with shorter age-adjusted relative telomere length (P < 0.001) in the 10 parent-child pairs from eight families with VHL disease. In addition, relative telomere length was shorter in the 29 patients with VHL disease than in the normal controls (P = 0.003). The anticipation may relate to the shortening of telomere length in patients with VHL in successive generations. These findings indicate that anticipation is present in families with VHL disease and may be helpful for genetic counseling for families with VHL disease families and for further understanding the pathogenesis of VHL disease.

Lymphocyte telomere length is long in BRCA1 and BRCA2 mutation carriers regardless of cancer-affected status

BACKGROUND

Telomere length has been linked to risk of common diseases, including cancer, and has previously been proposed as a biomarker for cancer risk. Germline BRCA1 and BRCA2 mutations predispose to breast, ovarian, and other cancer types.

METHODS

We investigated telomere length in BRCA mutation carriers and their non-carrier relatives and further examined whether telomere length is a modifier of cancer risk in mutation carriers. We measured mean telomere length in DNA extracted from whole blood using high-throughput quantitative PCR. Participants were from the EMBRACE study in United Kingdom and Eire (n = 4,822) and comprised BRCA1 (n = 1,628) and BRCA2 (n = 1,506) mutation carriers and their non-carrier relatives (n = 1,688).

RESULTS

We find no significant evidence that mean telomere length is associated with breast or ovarian cancer risk in BRCA mutation carriers. However, we find mutation carriers to have longer mean telomere length than their non-carrier relatives (all carriers vs. non-carriers, Ptrend = 0.0018), particularly in families with BRCA2 mutations (BRCA2 mutation carriers vs. all non-carriers, Ptrend = 0.0016).

CONCLUSIONS

Our findings lend little support to the hypothesis that short mean telomere length predisposes to cancer. Conversely, our main and unexpected finding is that BRCA mutation carriers (regardless of cancer status) have longer telomeres than their non-mutation carrier, non-cancer-affected relatives. The longer telomere length in BRCA2 mutation carriers is consistent with its role in DNA damage response. Overall, it seems that increased telomere length may be a consequence of these mutations, but is not itself directly related to the increased cancer risk in carriers.

IMPACT

The finding that mutation carriers have longer mean telomere lengths than their non-carrier relatives is unexpected but biologically plausible and could open up new lines of research into the functions of the BRCA proteins. To our knowledge, this is the largest study of telomere length in BRCA mutation carriers and their relatives. The null cancer-risk association supports recent large prospective studies of breast and ovarian cancer and indicates that mean telomere length would not be a useful biomarker in these cancers. Cancer Epidemiol Biomarkers Prev; 23(6); 1018-24. ©2014 AACR.

WRN loss induces switching of telomerase-independent mechanisms of telomere elongation

Telomere maintenance can occur in the presence of telomerase or in its absence, termed alternative lengthening of telomeres (ALT). ALT adds telomere repeats using recombination-based processes and DNA repair proteins that function in homologous recombination. Our previous work reported that the RecQ-like BLM helicase is required for ALT and that it unwinds telomeric substrates in vitro. WRN is also a RecQ-like helicase that shares many biochemical functions with BLM. WRN interacts with BLM, unwinds telomeric substrates, and co-localizes to ALT-associated PML bodies (APBs), suggesting that it may also be required for ALT processes. Using long-term siRNA knockdown of WRN in three ALT cell lines, we show that some, but not all, cell lines require WRN for telomere maintenance. VA-13 cells require WRN to prevent telomere loss and for the formation of APBs; Saos-2 cells do not. A third ALT cell line, U-2 OS, requires WRN for APB formation, however WRN loss results in p53-mediated apoptosis. In the absence of WRN and p53, U-2 OS cells undergo telomere loss for an intermediate number of population doublings (50-70), at which point they maintain telomere length even with the continued loss of WRN. WRN and the tumor suppressor BRCA1 co-localize to APBs in VA-13 and U-2 OS, but not in Saos-2 cells. WRN loss in U-2 OS is associated with a loss of BRCA1 from APBs. While the loss of WRN significantly increases telomere sister chromatid exchanges (T-SCE) in these three ALT cell lines, loss of both BRCA1 and WRN does not significantly alter T-SCE. This work demonstrates that ALT cell lines use different telomerase-independent maintenance mechanisms that variably require the WRN helicase and that some cells can switch from one mechanism to another that permits telomere elongation in the absence of WRN. Our data suggest that BRCA1 localization may define these mechanisms.

BRCA1 and BRCA2 mutations and female fertility

PURPOSE OF REVIEW

To review recent publications examining BRCA1 and BRCA2 mutations and their relationship with female fertility.

RECENT FINDINGS

Eight relevant studies of female fertility, five of which were published since January 2010 and the remainder in the preceding decade. Several mechanisms suggest that reproduction will be adversely affected among BRCA1/2 mutation carriers, with one study finding lower oocyte production, another reporting fewer births, and a third showing lower rates of pregnancies. Four articles reported no significant difference in the number of children ever born between carriers and noncarriers whereas a 2012 study showed elevated natural fertility among mutation carriers.

SUMMARY

This review shows that for most articles there are adverse or no fertility effects of being a BRCA1/2 mutation carrier. When no differences were detected for children-ever-born, those studies relied on current populations in which women had access to contraception. The sole analysis reporting elevated fertility was based on an historic population in which family planning methods were unavailable. Predictions that BRCA1/2 mutations adversely affect embryogenesis and genome integrity were not supported. The idea that BRCA1/2 mutations have antagonistic pleiotropic effects (enhancing fertility while reducing survival) was supported in the natural fertility study.

Do BRCA1 and BRCA2 mutation carriers have earlier natural menopause than their noncarrier relatives? Results from the Kathleen Cuningham Foundation Consortium for Research into Familial Breast Cancer

PURPOSE

Limited data suggest that germline BRCA1 mutations are associated with occult primary ovarian insufficiency and that BRCA1 and BRCA2 mutation carriers might have earlier natural menopause (NM) than their noncarrier relatives.

PATIENTS AND METHODS

Eligible women were mutation carriers and noncarriers from families segregating a BRCA1 or BRCA2 mutation. Data were self-reported using uniform questionnaires at cohort entry and every 3 years thereafter. NM was defined as the cessation of menses for 12 months without another cause. Cox proportional hazards analysis modeled time from birth to NM, adjusting for multiple potential confounders. Analysis time was censored at the earliest of the following: last follow-up, bilateral oophorectomy, hysterectomy, commencement of hormone therapy, insertion of intrauterine device, or any cancer diagnosis. Hazard ratios (HRs) were estimated as a measure of how likely mutation carriers are, relative to noncarriers, to reach NM at a given age.

RESULTS

A total of 1,840 women were eligible for analysis. Overall only 19% reached NM. A lower proportion of BRCA1 and BRCA2 mutation carriers reached NM compared with noncarriers. Conversely, a higher proportion of mutation carriers were censored at cancer diagnosis or oophorectomy than noncarriers. The adjusted HR estimates for NM were 1.03 (95% CI, 0.75 to 1.40; P = .9) for 445 BRCA1 mutation carriers and 559 noncarrier relatives and 1.01 (95% CI, 0.71 to 1.42; P = .9) for 374 BRCA2 mutation carriers and 462 noncarrier relatives.

CONCLUSION

We found no evidence that BRCA1 and BRCA2 mutation carriers are at higher risk of NM at a given age than their noncarrier relatives.

Impairment of BRCA1-related DNA double-strand break repair leads to ovarian aging in mice and humans

The underlying mechanism behind age-induced wastage of the human ovarian follicle reserve is unknown. We identify impaired ATM (ataxia-telangiectasia mutated)-mediated DNA double-strand break (DSB) repair as a cause of aging in mouse and human oocytes. We show that DSBs accumulate in primordial follicles with age. In parallel, expression of key DNA DSB repair genes BRCA1, MRE11, Rad51, and ATM, but not BRCA2, declines in single mouse and human oocytes. In Brca1-deficient mice, reproductive capacity was impaired, primordial follicle counts were lower, and DSBs were increased in remaining follicles with age relative to wild-type mice. Furthermore, oocyte-specific knockdown of Brca1, MRE11, Rad51, and ATM expression increased DSBs and reduced survival, whereas Brca1 overexpression enhanced both parameters. Likewise, ovarian reserve was impaired in young women with germline BRCA1 mutations compared to controls as determined by serum concentrations of anti-Müllerian hormone. These data implicate DNA DSB repair efficiency as an important determinant of oocyte aging in women.

BRCA1 in the DNA damage response and at telomeres

Mutations of the breast and ovarian cancer susceptibility gene 1 (BRCA1) account for about 40-45% of hereditary breast cancer cases. Moreover, a significant fraction of sporadic (non-hereditary) breast and ovarian cancers exhibit reduced or absent expression of the BRCA1 protein, suggesting an additional role for BRCA1 in sporadic cancers. BRCA1 follows the classic pattern of a highly penetrant Knudsen-type tumor suppressor gene in which one allele is inactivated through a germ-line mutation and the other is mutated or deleted within the tumor. BRCA1 is a multi-functional protein but it is not fully understood which function(s) is (are) most important for tumor suppression, nor is it clear why BRCA1-mutations confer a high risk for breast and ovarian cancers and not a broad spectrum of tumor types. Here, we will review BRCA1 functions in the DNA damage response (DDR), which are likely to contribute to tumor suppression. In the process, we will highlight some of the controversies and unresolved issues in the field. We will also describe a recently identified and under-investigated role for BRCA1 in the regulation of telomeres and the implications of this role in the DDR and cancer suppression.

Association of BRCA1/2 mutations with FMR1 genotypes: effects on menarcheal and menopausal age

OBJECTIVE

Female BRCA (breast cancer gene)-1 and BRCA-2 mutations are significantly associated with risk of developing breast and ovarian cancers, in turn, associated with female infertility. BRCA-1 mutations have also been associated with occult primary ovarian insufficiency (OPOI), as have different mutations of the FMR1 gene. We, therefore, hypothesized that FMR1 genotypes may be associated with menarcheal and menopausal ages of BRCA mutation carriers.

PATIENTS

We compared the FMR1 genotype and sub-genotype distribution in 99 BRCA1/2 positive women and in 182 healthy women without a known history of familial breast and ovarian cancer and searched for associations with age at menarche and menopause. T-test was used to assess differences in menarcheal and menopause ages, with times of menarche and menopause as continuous variables.

RESULTS

Women with BRCA1/2 mutations showed significantly different FMR1 genotype and sub-genotype distributions when compared with the control group (p<0.001). This result remained stable in a sub-group analysis of Caucasian BRCA1/2 carriers and healthy controls (p<0.001). In addition, BRCA1/2 carriers indicated a trend toward shorter reproductive lifespan (p=0.18).

CONCLUSIONS

Our data confirm the previously reported highly skewed distribution of FMR1 genotypes and sub-genotypes toward a high preponderance of low FMR1 alleles in BRCA1/2 carriers. We could demonstrate that BRCA-1 mutations are associated with an earlier onset of menopause compared to BRCA-2 carriers, although the distribution of the het-norm/low genotype is similar in both groups. Our findings suggest that there may be other factors beside the genotype that has an influence on menarche and especially menopause age in BRCA mutation carriers.

Frequency of premature menopause in women who carry a BRCA1 or BRCA2 mutation

OBJECTIVE

To evaluate the impact of carrying a BRCA1 or BRCA2 mutation on the probability of experiencing premature natural menopause.

DESIGN

Observational study.

SETTING

Patients in an academic research environment.

PATIENT(S)

Women who carry a BRCA1 or BRCA2 mutation (case subjects) and women who do not carry a mutation (control subjects).

INTERVENTION(S)

Survey about reproductive history administered on study entry and every 2 years thereafter.

MAIN OUTCOME MEASURE(S)

The impact of carrying a BRCA mutation on age at menopause and other factors, including parity, age at first birth, age at last birth, and self-reported fertility.

RESULT(S)

A total of 908 matched pairs were identified. The mean age at natural menopause was 48.8 years for BRCA1 carriers, 49.2 years for BRCA2 carriers, and 50.3 years for control subjects. Women who carried a BRCA mutation had parity similar to noncarriers and were as likely as noncarriers to have a child after age 35 years. Similar proportions reported a history of fertility problems (12.5% vs. 13.7%) and use of fertility medication (6.0% vs. 7.0%).

CONCLUSION(S)

Women who carry a BRCA mutation experience menopause earlier, on average, than women who do not have a mutation, but the difference is small and does not appear to affect fertility.

A two-step mechanism for TRF2-mediated chromosome-end protection

Mammalian telomeres repress DNA damage activation at natural chromosome ends by recruiting specific inhibitors of the DNA damage machinery that form a protective complex termed shelterin. Within this complex, TRF2 plays a crucial role in end-protection as it is required to suppress ATM activation and the formation of end-to-end chromosome fusions^{1, 2}. Here, we address the molecular properties of TRF2 that are both necessary and sufficient to protect chromosome ends. Our data support a two-step mechanism for TRF2-mediated end protection. First, the dimerization domain of TRF2 is required to inhibit ATM activation, the key initial step involved in activation of a DNA damage response. Next, TRF2 independently suppresses the propagation of DNA damage signaling downstream of ATM activation. This novel modulation of the DNA damage response at telomeres occurs at the level of the E3 ubiquitin ligase RNF168 ³. Inhibition of RNF168 at telomeres involves the de-ubiquitinating enzyme BRCC3 and the ubiquitin ligase UBR5 and is sufficient to suppress chromosome end-to-end fusions. This two-step mechanism for TRF2-mediated end protection helps to explain the apparent paradox of frequent localization of DNA damage response proteins at functional telomeres without concurrent induction of detrimental DNA repair activities.

Mutational analysis of telomere genes in BRCA1/2-negative breast cancer families with very short telomeres

A majority of the familial breast cancer cases are not explained by mutations in the best-known high susceptibility genes BRCA1 and BRCA2. Since there is a link between DNA repair and telomere maintenance mechanisms, we have investigated for the first time the role of telomere genes in breast cancer predisposition. By a combination of DHPLC and direct sequencing, we screened for sequence variation in 14 telomere-related genes which included telomerase and shelterin complexes in index cases from 50 BRCA1/2-negative families previously characterized to have very short telomere length in peripheral blood leukocytes. Clear pathogenic changes were not detected in any of the genes analyzed. Most of the changes were non-coding variants and only nine corresponded to coding variants located in TPP1, TINF2, NHP2, TNKS, and RAD54B genes; although only two corresponded to coding missense changes leading to aminoacid changes in genes NHP2 and RAD54B. However, functional prediction analysis and control population studies of both variants ruled out its possible pathogenic role. Our results discard a major contribution of telomere-specific genes in hereditary breast cancer.

BRCA1 and BRCA2: different roles in a common pathway of genome protection

The proteins encoded by the two major breast cancer susceptibility genes, BRCA1 and BRCA2, work in a common pathway of genome protection. However, the two proteins work at different stages in the DNA damage response (DDR) and in DNA repair. BRCA1 is a pleiotropic DDR protein that functions in both checkpoint activation and DNA repair, whereas BRCA2 is a mediator of the core mechanism of homologous recombination. The links between the two proteins are not well understood, but they must exist to explain the marked similarity of human cancer susceptibility that arises with germline mutations in these genes. As discussed here, the proteins work in concert to protect the genome from double-strand DNA damage during DNA replication.

Centrosomal and mitotic abnormalities in cell lines derived from papillary thyroid cancer harboring specific gene alterations

BACKGROUND

Differentiated thyroid carcinoma offers a good model to investigate the possible correlation between specific gene mutations and chromosome instability. Papillary thyroid neoplasms are characterized by different mutually exclusive genetic alterations, some of which are associated with aneuploidy and aggressive phenotype.

RESULTS

We investigated the centrosome status and mitotic abnormalities in three thyroid carcinoma-derived cell lines, each maintaining the specific, biologically relevant gene alteration harbored by the parental tumors: RET/PTC1 rearrangement in TPC1; heterozygous and homozygous BRAFV600E mutation in K1 and in B-CPAP, respectively. B-CPAP cells showed a statistically significant (P < 0.01) higher frequency of abnormal mitotic figures compared to TPC1 and K1 cells.

CONCLUSIONS

Our data indicate that RET/PTC1 oncogenic activity is not related to mitotic chromosome impairment and missegregation whereas, based on the consistent difference in types/frequencies of centrosome and spindle abnormalities observed between K1 and B-CPAP cells, the hetero/homozygous allelic status of BRAFV600E mutation seems to be not irrelevant in respect to chromosomal instability development.

Effects of BRCA1 and BRCA2 mutations on female fertility

Women with BRCA1/2 mutations have a significantly higher lifetime risk of developing breast or ovarian cancer. We suggest that female mutation carriers may have improved fitness owing to enhanced fertility relative to non-carriers. Here we show that women who are carriers of BRCA1/2 mutations living in natural fertility conditions have excess fertility as well as excess post-reproductive mortality in relation to controls. Individuals who tested positive for BRCA1/2 mutations who linked into multi-generational pedigrees within the Utah Population Database were used to identify putative obligate carriers. We find that women born before 1930 who are mutation carriers have significantly more children than controls and have excess post-reproductive mortality risks. They also have shorter birth intervals and end child-bearing later than controls. For contemporary women tested directly for BRCA1/2 mutations, an era when modern contraceptives are available, differences in fertility and mortality persist but are attenuated. Our findings suggest the need to re-examine the wider role played by BRCA1/2 mutations. Elevated fertility of female mutation carriers indicates that they are more fecund despite their elevated post-reproductive mortality risks.

Genetic anticipation is associated with telomere shortening in hereditary breast cancer

There is increasing evidence suggesting that short telomeres and subsequent genomic instability contribute to malignant transformation. Telomere shortening has been described as a mechanism to explain genetic anticipation in dyskeratosis congenita and Li-Fraumeni syndrome. Since genetic anticipation has been observed in familial breast cancer, we aimed to study telomere length in familial breast cancer patients and hypothesized that genetic defects causing this disease would affect telomere maintenance resulting in shortened telomeres. Here, we first investigated age anticipation in mother-daughter pairs with breast cancer in 623 breast cancer families, classified as BRCA1, BRCA2, and BRCAX. Moreover, we analyzed telomere length in DNA from peripheral blood leukocytes by quantitative PCR in a set of 198 hereditary breast cancer patients, and compared them with 267 control samples and 71 sporadic breast cancer patients. Changes in telomere length in mother-daughter pairs from breast cancer families and controls were also evaluated to address differences through generations. We demonstrated that short telomeres characterize hereditary but not sporadic breast cancer. We have defined a group of BRCAX families with short telomeres, suggesting that telomere maintenance genes might be susceptibility genes for breast cancer. Significantly, we described that progressive telomere shortening is associated with earlier onset of breast cancer in successive generations of affected families. Our results provide evidence that telomere shortening is associated with earlier age of cancer onset in successive generations, suggesting that it might be a mechanism of genetic anticipation in hereditary breast cancer.

The fact that accelerated telomere shortening accompanies different premature aging syndromes and seems to be associated with increased risk of cancer development prompted us to analyze the role of telomere length in hereditary breast cancer. In this study we found that telomeres of peripheral blood cells from familial breast cancer patients were significantly shorter than those from the control population. Women carrying a mutation in BRCA1 or BRCA2 genes, and a subset of BRCAX families, were characterized by short telomeres. We also demonstrated that genetic anticipation, the successive earlier age of onset of cancer, in these families was associated with a decrease of the telomere length in affected daughters compared to their mothers. This is the first study suggesting that telomere shortening may contribute to anticipation in breast cancer families and that analysis of telomere length in hereditary breast cancer may affect the design of surveillance programs for affected families.

Cell cycle-dependent induction of homologous recombination by a tightly regulated I-SceI fusion protein

Double-strand break repair is executed by two major repair pathways: non-homologous end joining (NHEJ) and homologous recombination (HR). Whereas NHEJ contributes to the repair of ionizing radiation (IR)-induced double strand breaks (DSBs) throughout the cell cycle, HR acts predominantly during the S and G2 phases of the cell cycle. The rare-cutting restriction endonuclease, I-SceI, is in common use to study the repair of site-specific chromosomal DSBs in vertebrate cells. To facilitate analysis of I-SceI-induced DSB repair, we have developed a stably expressed I-SceI fusion protein that enables precise temporal control of I-SceI activation, and correspondingly tight control of the timing of onset of site-specific chromosome breakage. I-SceI-induced HR showed a strong, positive linear correlation with the percentage of cells in S phase, and was negatively correlated with the G1 fraction. Acute depletion of BRCA1, a key regulator of HR, disrupted the relationship between S phase fraction and I-SceI-induced HR, consistent with the hypothesis that BRCA1 regulates HR during S phase.

Defective Artemis causes mild telomere dysfunction

Background

Repair of DNA double strand breaks by non-homologous end joining (NHEJ) requires several proteins including Ku, DNA-PKcs, Artemis, XRCC4, Ligase IV and XLF. Two of these proteins, namely Ku and DNA-PKcs, are also involved in maintenance of telomeres, chromosome end-structures. In contrast, cells defective in Ligase IV and XRCC4 do not show changes in telomere length or function suggesting that these proteins are not involved in telomere maintenance. Since a mouse study indicated that defective Artemis may cause telomere dysfunction we investigated the effects of defective Artemis on telomere maintenance in human cells.

Results

We observed significantly elevated frequencies of telomeric fusions in two primary fibroblast cell lines established from Artemis defective patients relative to the control cell line. The frequencies of telomeric fusions increased after exposure of Artemis defective cells to ionizing radiation. Furthermore, we observed increased incidence of DNA damage at telomeres in Artemis defective cells that underwent more than 32 population doublings using the TIF (Telomere dysfunction Induced Foci) assay. We have also inhibited the expression levels of DNA-PKcs in Artemis defective cell lines by either using synthetic inhibitor (IC86621) or RNAi and observed their greater sensitivity to telomere dysfunction relative to control cells.

Conclusion

These results suggest that defective Artemis causes a mild telomere dysfunction phenotype in human cell lines.

BRCA1 localization to the telomere and its loss from the telomere in response to DNA damage

BRCA1, a tumor suppressor, participates in DNA damage signaling and repair. Previously, we showed that BRCA1 overexpression caused inhibition of telomerase activity and telomere shortening in breast and prostate cancer cells. We now report that BRCA1 knockdown causes increased telomerase reverse transcriptase expression, telomerase activity, and telomere length; but studies utilizing a combination of BRCA1 and telomerase reverse transcriptase small interfering RNAs suggest that BRCA1 also regulates telomere length independently of telomerase. Using telomeric chromatin immunoprecipitation assays, we detected BRCA1 at the telomere and demonstrated time-dependent loss of BRCA1 from the telomere following DNA damage. Further studies suggest that BRCA1 interacts with TRF1 and TRF2 in a DNA-dependent manner and that some of the nuclear BRCA1 colocalizes with TRF1/2. Our findings further suggest that Rad50 is required to localize BRCA1 at the telomere and that the association of BRCA1 with Rad50 does not require DNA. Finally, we found that BRCA1 regulates the length of the 3' G-rich overhang in a manner that is dependent upon Rad50. Our findings suggest that BRCA1 is recruited to the telomere in a Rad50-dependent manner and that BRCA1 may regulate telomere length and stability, in part through its presence at the telomere.

Mechanisms of double-strand break repair in somatic mammalian cells

DNA chromosomal DSBs (double-strand breaks) are potentially hazardous DNA lesions, and their accurate repair is essential for the successful maintenance and propagation of genetic information. Two major pathways have evolved to repair DSBs: HR (homologous recombination) and NHEJ (non-homologous end-joining). Depending on the context in which the break is encountered, HR and NHEJ may either compete or co-operate to fix DSBs in eukaryotic cells. Defects in either pathway are strongly associated with human disease, including immunodeficiency and cancer predisposition. Here we review the current knowledge of how NHEJ and HR are controlled in somatic mammalian cells, and discuss the role of the chromatin context in regulating each pathway. We also review evidence for both co-operation and competition between the two pathways.

Premature senescence is a major response to DNA cross-linking agents in BRCA1-defective cells: implication for tailored treatments of BRCA1 mutation carriers

BRCA1-associated tumors are characterized by an elevated genomic instability and peculiar expression profiles. Nevertheless, tailored treatments for BRCA1 mutation carriers have only been partially investigated up to now. The implementation of therapeutic strategies specific for these patients has been in part hindered by the paucity of proper preneoplastic and neoplastic BRCA1-deficient tumor cell models. In this study, we took advantage of the RNA interference technology to generate a series of partially transformed (HBL100) and tumorigenic (MCF7 and T47D) breast cancer cell lines in which BRCA1 expression was silenced at different levels. These cell models were probed by clonogenic assay for their response to several DNA-damaging agents commonly used in cancer therapy (mitomycin C, cisplatin, doxorubicin, and etoposide). Our models confirmed the peculiar sensitivity to interstrand cross-link inducers associated with BRCA1 deficiency. Intriguingly, the increased sensitivity to these compounds displayed by BRCA1-defective cells was not correlated with the extent of apoptotic cell death but rather associated to an increased fraction of growth-arrested, enlarged, multinucleated beta-galactosidase-positive senescent cells. Overall, our results support a role for BRCA1 in the regulation of interstrand cross-link-induced premature senescence and suggest a reconsideration of the therapeutic power of mitomycin/platinum-based treatments in BRCA1 carriers. Moreover, our data further prompt the setup of strategies for the imaging of the senescence response in vivo.

Poor maternal nutrition followed by accelerated postnatal growth leads to telomere shortening and increased markers of cell senescence in rat islets

Low birth weight (LBW) followed by accelerated postnatal growth is associated with increased risk of developing age-associated diseases such as type 2 diabetes. Gestational protein restriction in rats causes LBW, beta-cell dysfunction, and reduced longevity. These effects may be mediated by accelerated cellular aging. This study tested the hypothesis that LBW followed by rapid postnatal catch-up growth leads to islet telomere shortening through alterations in antioxidant defense capacity, stress/senescence marker proteins, and DNA repair mechanisms at the gene expression level. We used our rat model of gestational protein restriction (recuperated offspring) and control offspring. Southern blotting revealed shorter (P<0.001) islet telomeres in recuperated animals compared to controls. This was associated with increased expression of peroxiredoxin 1 (P<0.05), peroxiredoxin 3 (P<0.01), and heme oxygenase-1 (HO-1) (P<0.05), which are up-regulated under stress conditions. MnSOD expression was significantly (P<0.05) decreased in recuperated offspring, suggesting partial impairment of mitochondrial antioxidant defenses. Markers of cellular senescence p21 and p16 were also increased (P<0.01 and P<0.05, respectively) in the recuperated group. We conclude that maternal diet influences expression of markers of cellular stress and telomere length in pancreatic islets. This may provide a mechanistic link between early nutrition and growth and type 2 diabetes.

Localization of TEIF in the centrosome and its functional association with centrosome amplification in DNA damage, telomere dysfunction and human cancers

Centrosome amplification and telomere shortening, which are commonly detected in human cancers, have been implicated in the induction of chromosome instability in tumorigenesis. The functions of these two structures are closely related to DNA damage repair machinery, and some factors that operate in the maintenance of telomeres also take part in the regulation of centrosome status, suggesting they are functionally linked. We report that TEIF (telomerase transcriptional elements-interacting factor), a transactivator of the hTERT (human telomerase reverse transcriptase subunit) gene, is distributed in the centrosome throughout the cell cycle, but its transport into the centrosome is increased under some conditions, and its distribution is dependent on its C-terminal domain. Experimental modulation of TEIF expression through overexpression, polypeptide expression or depletion affected centrosome status and increased abnormalities of cell mitosis. Localization of TEIF to the centrosome was also stimulated by treatment with genotoxic agents and experimental telomere dysfunction, accompanying centrosome amplification. Moreover, we demonstrated that the expression level of TEIF is not only closely correlated with centrosome amplification in soft tissue sarcomas but it is also significantly related to tumor histologic grade. Our data confirmed TEIF functions as a centrosome regulator. Its participation in DNA damage response, including telomere dysfunction and tumorigenesis, indicates TEIF is likely to be a factor involved in linking centrosome amplification and telomere dysfunction in cancer development.