Browsing by Subject "BRCA1"

Now showing 1 - 5 of 5
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    Altered Expression of Telomere-Associated Genes in Leukocytes among BRCA1 and BRCA2 Carriers
    (Wiley, 2018) Tanaka, Hiromi; Phipps, Elizabeth A.; Wei, Ting; Wu, Xi; Goswami, Chirayu; Liu, Yunlong; Sledge, George W., Jr.; Mina, Lida; Herbert, Brittney-Shea; Medical and Molecular Genetics, School of Medicine
    Telomere dysfunction resulting from telomere shortening and deregulation of shelterin components has been linked to the pathogenesis of age-related disorders, including cancer. Recent evidence suggests that BRCA1/2 (BRCA1 and BRCA2) tumor suppressor gene products play an important role in telomere maintenance. Although telomere shortening has been reported in BRCA1/2 carriers, the direct effects of BRCA1/2 haploinsufficiency on telomere maintenance and predisposition to cancer development are not completely understood. In this study, we assessed the telomere-associated and telomere-proximal gene expression profiles in peripheral blood leukocytes from patients with a BRCA1 or BRCA2 mutation, compared to samples from sporadic and familial breast cancer individuals. We found that 25 genes, including TINF2 gene (a negative regulator of telomere length), were significantly differentially expressed in BRCA1 carriers. Leukocyte telomere length analysis revealed that BRCA1/2 carriers had relatively shorter telomeres than healthy controls. Further, affected BRCA1/2 carriers were well differentiated from unaffected BRCA1/2 carriers by the expression of telomere-proximal genes. Our results link BRCA1/2 haploinsufficiency to changes in telomere length, telomere-associated as well as telomere-proximal gene expression. Thus, this work supports the effect of BRCA1/2 haploinsufficiency in the biology underlying telomere dysfunction in cancer development. Future studies evaluating these findings will require a large study population.
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    The endonuclease EEPD1 mediates synthetic lethality in RAD52-depleted BRCA1 mutant breast cancer cells
    (BMC, 2017) Hromas, Robert; Kim, Hyun-Suk; Sidhu, Gurjit; Williamson, Elizabeth; Jaiswal, Aruna; Totterdale, Taylor A.; Nole, Jocelyn; Lee, Suk-Hee; Nickoloff, Jac A.; Kong, Kimi Y.; Biochemistry and Molecular Biology, School of Medicine
    Background Proper repair and restart of stressed replication forks requires intact homologous recombination (HR). HR at stressed replication forks can be initiated by the 5′ endonuclease EEPD1, which cleaves the stalled replication fork. Inherited or acquired defects in HR, such as mutations in breast cancer susceptibility protein-1 (BRCA1) or BRCA2, predispose to cancer, including breast and ovarian cancers. In order for these HR-deficient tumor cells to proliferate, they become addicted to a bypass replication fork repair pathway mediated by radiation repair protein 52 (RAD52). Depleting RAD52 can cause synthetic lethality in BRCA1/2 mutant cancers by an unknown molecular mechanism. Methods We hypothesized that cleavage of stressed replication forks by EEPD1 generates a fork repair intermediate that is toxic when HR-deficient cells cannot complete repair with the RAD52 bypass pathway. To test this hypothesis, we applied cell survival assays, immunofluorescence staining, DNA fiber and western blot analyses to look at the correlation between cell survival and genome integrity in control, EEPD1, RAD52 and EEPD1/RAD52 co-depletion BRCA1-deficient breast cancer cells. Results Our data show that depletion of EEPD1 suppresses synthetic lethality, genome instability, mitotic catastrophe, and hypersensitivity to stress of replication of RAD52-depleted, BRCA1 mutant breast cancer cells. Without HR and the RAD52-dependent backup pathway, the BRCA1 mutant cancer cells depleted of EEPD1 skew to the alternative non-homologous end-joining DNA repair pathway for survival. Conclusion This study indicates that the mechanism of synthetic lethality in RAD52-depleted BRCA1 mutant cancer cells depends on the endonuclease EEPD1. The data imply that EEPD1 cleavage of stressed replication forks may result in a toxic intermediate when replication fork repair cannot be completed. Electronic supplementary material The online version of this article (doi:10.1186/s13058-017-0912-8) contains supplementary material, which is available to authorized users.
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    Natural Killer Cell Dysfunction in Premenopausal BRCA1 Mutation Carriers: A Potential Mechanism for Ovarian Carcinogenesis
    (MDPI, 2024-03-18) Haran, Shaun; Chindera, Kantaraja; Sabry, May; Wilkinson, Nafisa; Arora, Rupali; Zubiak, Agnieszka; Bartlett, Thomas E.; Evans, Iona; Jones, Allison; Reisel, Daniel; Herzog, Chiara; Alkasalias, Twana; Newman, Mark; Kim, Jaeyeon; Flöter Rådestad, Angelique; Gemzell-Danielsson, Kristina; Rosenthal, Adam N.; Dubeau, Louis; Lowdell, Mark W.; Widschwendter, Martin; Biochemistry and Molecular Biology, School of Medicine
    Background: Tissue-specificity for fimbrial fallopian tube ovarian carcinogenesis remains largely unknown in BRCA1 mutation carriers. We aimed to assess the cell autonomous and cell-nonautonomous implications of a germline BRCA1 mutation in the context of cancer immunosurveillance of CD3- CD56+ natural killer (NK) cells. Methods: Premenopausal BRCA1 mutation carriers versus age-matched non-carriers were compared. Daily urinary 5β-pregnanediol levels were used to determine progesterone metabolomics across an ovarian cycle. Using peripherally acquired NK cells the cell-mediated cytotoxicity of tumor targets (OVCAR-3, K-562) was determined using live cellular impedance (xCELLigence®) and multicolor flow cytometry. Hypoxia-inducible factor 1-alpha (HIF-1α) immunohistochemistry of cancer-free fallopian tube specimens allowed a comparison of proximal versus distal portions. Utilizing these findings the role of environmental factors relevant to the fimbrial fallopian tube (progesterone, hypoxia) on NK cell functional activity were studied in an ovarian phase-specific manner. Results: BRCA1 mutation carriers demonstrate a differential progesterone metabolome with a phase-specific reduction of peripheral NK cell functional activity. Progesterone exposure further impairs NK cell-mediated cytotoxicity in a dose-dependent manner, which is reversed with the addition of mifepristone (1.25 µM). The fimbrial fallopian tube demonstrated significantly higher HIF-1α staining, particularly in BRCA1 mutation carriers, reflecting a site-specific 'hypoxic niche'. Exposure to hypoxic conditions (1% O2) can further impair tumor cytotoxicity in high-risk carriers. Conclusions: Phase-specific differential NK cell activity in BRCA1 mutation carriers, either systemically or locally, may favor site-specific pre-invasive carcinogenesis. These cumulative effects across a reproductive lifecycle in high-risk carriers can have a detrimental effect further supporting epidemiological evidence for ovulation inhibition.
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    A plasma telomeric cell-free DNA level in unaffected women with BRCA1 or/and BRCA2 mutations: a pilot study
    (Impact Journals, 2017-12-29) Dey, Shatovisha; Marino, Natascia; Bishop, Kanokwan; Dahlgren, Paige N.; Shendre, Aditi; Storniolo, Anna Maria; He, Chunyan; Tanaka, Hiromi; Medical and Molecular Genetics, School of Medicine
    Plasma cell-free DNA (cfDNA) is a small DNA fragment circulating in the bloodstream originating from both non-tumor- and tumor-derived cells. A previous study showed that a plasma telomeric cfDNA level decreases in sporadic breast cancer patients compared to controls. Tumor suppressor gene products including BRCA1 and BRCA2 (BRCA1&2) play an important role in telomere maintenance. In this study, we hypothesized that the plasma telomeric cfDNA level is associated with the mutation status of BRCA1&2 genes. To test this hypothesis, we performed plasma telomeric cfDNA quantitative PCR (qPCR)-based assays to compare 28 women carriers of the BRCA1&2 mutation with age-matched controls of 28 healthy women. The results showed that the plasma telomeric cfDNA level was lower in unaffected BRCA1&2 mutation carriers than in age-matched controls from non-obese women (BMI < 30), while there was no association between unaffected BRCA1&2 mutation carriers and age-matched controls in obese women (BMI > 30). Moreover, the plasma telomeric cfDNA level applied aptly to the Tyrer-Cuzick model in non-obese women. These findings suggest that circulating cfDNA may detect dysfunctional telomeres derived from cells with BRCA1&2 mutations and, therefore, its level is associated with breast cancer susceptibility. This pilot study warrants further investigation to elucidate the implication of plasma telomeric cfDNA levels in relation to cancer and obesity.
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    Replication gaps are a key determinant of PARP inhibitor synthetic lethality with BRCA deficiency
    (Cell Press, 2021) Cong, Ke; Peng, Min; Kousholt, Arne Nedergaard; Lee, Wei Ting C.; Lee, Silviana; Nayak, Sumeet; Krais, John; VanderVere-Carozza, Pamela S.; Pawelczak, Katherine S.; Calvo, Jennifer; Panzarino, Nicholas J.; Turchi, John J.; Johnson, Neil; Jonkers, Jos; Rothenberg, Eli; Cantor, Sharon B.; Medicine, School of Medicine
    Mutations in BRCA1 or BRCA2 (BRCA) is synthetic lethal with poly(ADP-ribose) polymerase inhibitors (PARPi). Lethality is thought to derive from DNA double-stranded breaks (DSBs) necessitating BRCA function in homologous recombination (HR) and/or fork protection (FP). Here, we report instead that toxicity derives from replication gaps. BRCA1- or FANCJ-deficient cells, with common repair defects but distinct PARPi responses, reveal gaps as a distinguishing factor. We further uncouple HR, FP, and fork speed from PARPi response. Instead, gaps characterize BRCA-deficient cells, are diminished upon resistance, restored upon resensitization, and, when exposed, augment PARPi toxicity. Unchallenged BRCA1-deficient cells have elevated poly(ADP-ribose) and chromatin-associated PARP1, but aberrantly low XRCC1 consistent with defects in backup Okazaki fragment processing (OFP). 53BP1 loss resuscitates OFP by restoring XRCC1-LIG3 that suppresses the sensitivity of BRCA1-deficient cells to drugs targeting OFP or generating gaps. We highlight gaps as a determinant of PARPi toxicity changing the paradigm for synthetic lethal interactions.