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1.
Nat Commun ; 12(1): 4919, 2021 08 13.
Artigo em Inglês | MEDLINE | ID: mdl-34389725

RESUMO

BRCA1 or BRCA2 germline mutations predispose to breast, ovarian and other cancers. High-throughput sequencing of tumour genomes revealed that oncogene amplification and BRCA1/2 mutations are mutually exclusive in cancer, however the molecular mechanism underlying this incompatibility remains unknown. Here, we report that activation of ß-catenin, an oncogene of the WNT signalling pathway, inhibits proliferation of BRCA1/2-deficient cells. RNA-seq analyses revealed ß-catenin-induced discrete transcriptome alterations in BRCA2-deficient cells, including suppression of CDKN1A gene encoding the CDK inhibitor p21. This accelerates G1/S transition, triggering illegitimate origin firing and DNA damage. In addition, ß-catenin activation accelerates replication fork progression in BRCA2-deficient cells, which is critically dependent on p21 downregulation. Importantly, we find that upregulated p21 expression is essential for the survival of BRCA2-deficient cells and tumours. Thus, our work demonstrates that ß-catenin toxicity in cancer cells with compromised BRCA1/2 function is driven by transcriptional alterations that cause aberrant replication and inflict DNA damage.


Assuntos
Proteína BRCA1/genética , Proteína BRCA2/genética , Oncogenes/genética , Transcrição Genética/genética , beta Catenina/genética , Proteína BRCA1/deficiência , Proteína BRCA2/deficiência , Neoplasias da Mama/genética , Neoplasias da Mama/metabolismo , Linhagem Celular Tumoral , Proliferação de Células/genética , Sobrevivência Celular/genética , Células Cultivadas , Inibidor de Quinase Dependente de Ciclina p21/genética , Inibidor de Quinase Dependente de Ciclina p21/metabolismo , Dano ao DNA , Feminino , Perfilação da Expressão Gênica/métodos , Células HeLa , Humanos , Neoplasias Ovarianas/genética , Neoplasias Ovarianas/metabolismo , RNA-Seq/métodos , beta Catenina/metabolismo
2.
Mol Pharm ; 18(10): 3820-3831, 2021 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-34449222

RESUMO

Telomerase represents an attractive target in oncology as it is expressed in cancer but not in normal tissues. The oligonucleotide inhibitors of telomerase represent a promising anticancer strategy, although poor cellular uptake can restrict their efficacy. In this study, gold nanoparticles (AuNPs) were used to enhance oligonucleotide uptake. "match" oligonucleotides complementary to the telomerase RNA template subunit (hTR) and "scramble" (control) oligonucleotides were conjugated to diethylenetriamine pentaacetate (DTPA) for 111In-labeling. AuNPs (15.5 nm) were decorated with a monofunctional layer of oligonucleotides (ON-AuNP) or a multifunctional layer of oligonucleotides, PEG(polethylene glycol)800-SH (to reduce AuNP aggregation) and the cell-penetrating peptide Tat (ON-AuNP-Tat). Match-AuNP enhanced the cellular uptake of radiolabeled oligonucleotides while retaining the ability to inhibit telomerase activity. The addition of Tat to AuNPs increased nuclear localization. 111In-Match-AuNP-Tat induced DNA double-strand breaks and caused a dose-dependent reduction in clonogenic survival of telomerase-positive cells but not telomerase-negative cells. hTR inhibition has been reported to sensitize cancer cells to ionizing radiation, and 111In-Match-AuNP-Tat therefore holds promise as a vector for delivery of radionuclides into cancer cells while simultaneously sensitizing them to the effects of the emitted radiation.

3.
Mol Cell ; 80(1): 21-28, 2020 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-32810436

RESUMO

Cancer immunotherapies enhance anti-tumor immune responses using checkpoint inhibitors, such as PD-1 or PD-L1 inhibitors. Recent studies, however, have extended the scope of immunotherapeutics by unveiling DNA damage-induced innate immunity as a novel target for cancer treatment. Elucidating the interplay among the DNA damage response (DDR), cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway activation, and anti-tumoral immunity is critical for the development of effective cancer immunotherapies. Here, we discuss the current understanding of the mechanisms by which DNA damage activates immune responses that target and eradicate cancer cells. Yet, understanding how cancer cells can escape this immune surveillance and promote tumor progression represents an outstanding challenge. We highlight the most recent clinical advances, in particular how pharmacological fine-tuning of innate/adaptive immunity and its combination with DDR inhibitors, ionizing radiation (IR), and chemotherapy can be exploited to improve cancer treatment.


Assuntos
Dano ao DNA , Imunoterapia , Proteínas de Membrana/metabolismo , Neoplasias/patologia , Neoplasias/terapia , Instabilidade Genômica , Humanos , Imunidade Inata , Neoplasias/genética , Neoplasias/imunologia
4.
Nat Rev Mol Cell Biol ; 21(5): 284-299, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32094664

RESUMO

The tumour suppressor breast cancer type 1 susceptibility protein (BRCA1) promotes DNA double-strand break (DSB) repair by homologous recombination and protects DNA replication forks from attrition. BRCA1 partners with BRCA1-associated RING domain protein 1 (BARD1) and other tumour suppressor proteins to mediate the initial nucleolytic resection of DNA lesions and the recruitment and regulation of the recombinase RAD51. The discovery of the opposing functions of BRCA1 and the p53-binding protein 1 (53BP1)-associated complex in DNA resection sheds light on how BRCA1 influences the choice of homologous recombination over non-homologous end joining and potentially other mutagenic pathways of DSB repair. Understanding the functional crosstalk between BRCA1-BARD1 and its cofactors and antagonists will illuminate the molecular basis of cancers that arise from a deficiency or misregulation of chromosome damage repair and replication fork maintenance. Such knowledge will also be valuable for understanding acquired tumour resistance to poly(ADP-ribose) polymerase (PARP) inhibitors and other therapeutics and for the development of new treatments. In this Review, we discuss recent advances in elucidating the mechanisms by which BRCA1-BARD1 functions in DNA repair, replication fork maintenance and tumour suppression, and its therapeutic relevance.


Assuntos
Proteína BRCA1/genética , Neoplasias da Mama/genética , Proteínas Supressoras de Tumor/genética , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/genética , Ubiquitina-Proteína Ligases/genética , Neoplasias da Mama/patologia , Reparo do DNA por Junção de Extremidades/genética , Replicação do DNA/genética , Feminino , Humanos , Inibidores de Poli(ADP-Ribose) Polimerases/farmacologia , Poli(ADP-Ribose) Polimerases/genética , Ligação Proteica/genética , Reparo de DNA por Recombinação/genética
5.
EMBO Mol Med ; 11(7): e9982, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31273933

RESUMO

Due to compromised homologous recombination (HR) repair, BRCA1- and BRCA2-mutated tumours accumulate DNA damage and genomic rearrangements conducive of tumour progression. To identify drugs that target specifically BRCA2-deficient cells, we screened a chemical library containing compounds in clinical use. The top hit was chlorambucil, a bifunctional alkylating agent used for the treatment of chronic lymphocytic leukaemia (CLL). We establish that chlorambucil is specifically toxic to BRCA1/2-deficient cells, including olaparib-resistant and cisplatin-resistant ones, suggesting the potential clinical use of chlorambucil against disease which has become resistant to these drugs. Additionally, chlorambucil eradicates BRCA2-deficient xenografts and inhibits growth of olaparib-resistant patient-derived tumour xenografts (PDTXs). We demonstrate that chlorambucil inflicts replication-associated DNA double-strand breaks (DSBs), similarly to cisplatin, and we identify ATR, FANCD2 and the SNM1A nuclease as determinants of sensitivity to both drugs. Importantly, chlorambucil is substantially less toxic to normal cells and tissues in vitro and in vivo relative to cisplatin. Because chlorambucil and cisplatin are equally effective inhibitors of BRCA2-compromised tumours, our results indicate that chlorambucil has a higher therapeutic index than cisplatin in targeting BRCA-deficient tumours.


Assuntos
Proteína BRCA1/deficiência , Proteína BRCA2/deficiência , Clorambucila/farmacologia , Sistemas de Liberação de Medicamentos , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Leucemia Linfocítica Crônica de Células B/tratamento farmacológico , Receptores Ativados por Proliferador de Peroxissomo/antagonistas & inibidores , Ftalazinas/farmacologia , Piperazinas/farmacologia , Animais , Linhagem Celular Tumoral , Cricetinae , Resistencia a Medicamentos Antineoplásicos/genética , Humanos , Leucemia Linfocítica Crônica de Células B/genética , Leucemia Linfocítica Crônica de Células B/metabolismo , Masculino , Camundongos , Camundongos SCID , Receptores Ativados por Proliferador de Peroxissomo/metabolismo , Ensaios Antitumorais Modelo de Xenoenxerto
6.
Cancer Res ; 79(18): 4627-4637, 2019 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-31311806

RESUMO

Telomerase is expressed in the majority (>85%) of tumors, but has restricted expression in normal tissues. Long-term telomerase inhibition in malignant cells results in progressive telomere shortening and reduction in cell proliferation. Here we report the synthesis and characterization of radiolabeled oligonucleotides that target the RNA subunit of telomerase, hTR, simultaneously inhibiting enzymatic activity and delivering radiation intracellularly. Oligonucleotides complementary (Match) and noncomplementary (Scramble or Mismatch) to hTR were conjugated to diethylenetriaminepentaacetic dianhydride (DTPA), allowing radiolabeling with the Auger electron-emitting radionuclide indium-111 (111In). Match oligonucleotides inhibited telomerase activity with high potency, which was not observed with Scramble or Mismatch oligonucleotides. DTPA-conjugation and 111In-labeling did not change telomerase inhibition. In telomerase-positive cancer cells, unlabeled Match oligonucleotides had no effect on survival, however, 111In-labeled Match oligonucleotides significantly reduced clonogenic survival and upregulated the DNA damage marker γH2AX. Minimal radiotoxicity and DNA damage was observed in telomerase-negative cells exposed to 111In-Match oligonucleotides. Match oligonucleotides localized in close proximity to nuclear Cajal bodies in telomerase-positive cells. In comparison with Match oligonucleotides, 111In-Scramble or 111In-Mismatch oligonucleotides demonstrated reduced retention and negligible impact on cell survival. This study indicates the therapeutic activity of radiolabeled oligonucleotides that specifically target hTR through potent telomerase inhibition and DNA damage induction in telomerase-expressing cancer cells and paves the way for the development of novel oligonucleotide radiotherapeutics targeting telomerase-positive cancers. SIGNIFICANCE: These findings present a novel radiolabeled oligonucleotide for targeting telomerase-positive cancer cells that exhibits dual activity by simultaneously inhibiting telomerase and promoting radiation-induced genomic DNA damage.


Assuntos
Radioisótopos de Índio/farmacologia , Neoplasias/terapia , Oligonucleotídeos Antissenso/farmacologia , Telomerase/antagonistas & inibidores , Apoptose , Proliferação de Células , Dano ao DNA , Regulação Enzimológica da Expressão Gênica , Regulação Neoplásica da Expressão Gênica , Terapia Genética , Humanos , Neoplasias/enzimologia , Neoplasias/genética , Neoplasias/patologia , Telomerase/genética , Telomerase/metabolismo , Células Tumorais Cultivadas
7.
Nat Commun ; 10(1): 3143, 2019 07 17.
Artigo em Inglês | MEDLINE | ID: mdl-31316060

RESUMO

Heterozygous germline mutations in BRCA2 predispose to breast and ovarian cancer. Contrary to non-cancerous cells, where BRCA2 deletion causes cell cycle arrest or cell death, tumors carrying BRCA2 inactivation continue to proliferate. Here we set out to investigate adaptation to loss of BRCA2 focusing on genome-wide transcriptome alterations. Human cells in which BRCA2 expression is inhibited for 4 or 28 days are subjected to RNA-seq analyses revealing a biphasic response to BRCA2 abrogation. The early, acute response consists of downregulation of genes involved in cell cycle progression, DNA replication and repair and is associated with cell cycle arrest in G1. Surprisingly, the late, chronic response consists predominantly of upregulation of interferon-stimulated genes (ISGs). Activation of the cGAS-STING-STAT pathway detected in these cells further substantiates the concept that BRCA2 abrogation triggers cell-intrinsic immune signaling. Importantly, we find that treatment with PARP inhibitors stimulates the interferon response in cells and tumors lacking BRCA2.


Assuntos
Proteína BRCA2/genética , Neoplasias da Mama/genética , Animais , Neoplasias da Mama/imunologia , Carcinoma Pulmonar de Células não Pequenas/genética , Carcinoma Pulmonar de Células não Pequenas/imunologia , Ciclo Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Neoplasias Colorretais/genética , Neoplasias Colorretais/imunologia , Dano ao DNA , Reparo do DNA , Feminino , Deleção de Genes , Regulação Neoplásica da Expressão Gênica , Humanos , Imunidade Inata , Camundongos SCID , Ftalazinas/farmacologia , Piperazinas/farmacologia
9.
Cancer Cell ; 33(6): 1078-1093.e12, 2018 06 11.
Artigo em Inglês | MEDLINE | ID: mdl-29894693

RESUMO

Inhibitors of poly(ADP-ribose) (PAR) polymerase (PARPi) have recently entered the clinic for the treatment of homologous recombination (HR)-deficient cancers. Despite the success of this approach, drug resistance is a clinical hurdle, and we poorly understand how cancer cells escape the deadly effects of PARPi without restoring the HR pathway. By combining genetic screens with multi-omics analysis of matched PARPi-sensitive and -resistant Brca2-mutated mouse mammary tumors, we identified loss of PAR glycohydrolase (PARG) as a major resistance mechanism. We also found the presence of PARG-negative clones in a subset of human serous ovarian and triple-negative breast cancers. PARG depletion restores PAR formation and partially rescues PARP1 signaling. Importantly, PARG inactivation exposes vulnerabilities that can be exploited therapeutically.


Assuntos
Glicosídeo Hidrolases/genética , Poli(ADP-Ribose) Polimerase-1/genética , Inibidores de Poli(ADP-Ribose) Polimerases/farmacologia , Mutações Sintéticas Letais , Animais , Proteína BRCA1/genética , Proteína BRCA1/metabolismo , Neoplasias da Mama/tratamento farmacológico , Neoplasias da Mama/genética , Neoplasias da Mama/metabolismo , Linhagem Celular Tumoral , Feminino , Glicosídeo Hidrolases/antagonistas & inibidores , Glicosídeo Hidrolases/metabolismo , Recombinação Homóloga/efeitos dos fármacos , Recombinação Homóloga/genética , Humanos , Camundongos da Linhagem 129 , Camundongos Knockout , Neoplasias Ovarianas/tratamento farmacológico , Neoplasias Ovarianas/genética , Neoplasias Ovarianas/metabolismo , Poli(ADP-Ribose) Polimerase-1/antagonistas & inibidores , Poli(ADP-Ribose) Polimerase-1/metabolismo , Poli ADP Ribosilação/efeitos dos fármacos
11.
EMBO Mol Med ; 9(10): 1398-1414, 2017 10.
Artigo em Inglês | MEDLINE | ID: mdl-28729482

RESUMO

Maintenance of genome integrity requires the functional interplay between Fanconi anemia (FA) and homologous recombination (HR) repair pathways. Endogenous acetaldehyde, a product of cellular metabolism, is a potent source of DNA damage, particularly toxic to cells and mice lacking the FA protein FANCD2. Here, we investigate whether HR-compromised cells are sensitive to acetaldehyde, similarly to FANCD2-deficient cells. We demonstrate that inactivation of HR factors BRCA1, BRCA2, or RAD51 hypersensitizes cells to acetaldehyde treatment, in spite of the FA pathway being functional. Aldehyde dehydrogenases (ALDHs) play key roles in endogenous acetaldehyde detoxification, and their chemical inhibition leads to cellular acetaldehyde accumulation. We find that disulfiram (Antabuse), an ALDH2 inhibitor in widespread clinical use for the treatment of alcoholism, selectively eliminates BRCA1/2-deficient cells. Consistently, Aldh2 gene inactivation suppresses proliferation of HR-deficient mouse embryonic fibroblasts (MEFs) and human fibroblasts. Hypersensitivity of cells lacking BRCA2 to acetaldehyde stems from accumulation of toxic replication-associated DNA damage, leading to checkpoint activation, G2/M arrest, and cell death. Acetaldehyde-arrested replication forks require BRCA2 and FANCD2 for protection against MRE11-dependent degradation. Importantly, acetaldehyde specifically inhibits in vivo the growth of BRCA1/2-deficient tumors and ex vivo in patient-derived tumor xenograft cells (PDTCs), including those that are resistant to poly (ADP-ribose) polymerase (PARP) inhibitors. The work presented here therefore identifies acetaldehyde metabolism as a potential therapeutic target for the selective elimination of BRCA1/2-deficient cells and tumors.


Assuntos
Acetaldeído/metabolismo , Proteína BRCA1/metabolismo , Proteína BRCA2/metabolismo , Rad51 Recombinase/metabolismo , Aldeído-Desidrogenase Mitocondrial/genética , Aldeído-Desidrogenase Mitocondrial/metabolismo , Animais , Proteína BRCA1/genética , Proteína BRCA2/genética , Linhagem Celular Tumoral , Dano ao DNA , Anemia de Fanconi/genética , Proteína do Grupo de Complementação D2 da Anemia de Fanconi/genética , Proteína do Grupo de Complementação D2 da Anemia de Fanconi/metabolismo , Fibroblastos , Recombinação Homóloga , Humanos , Camundongos , Camundongos Nus , Rad51 Recombinase/genética , Ensaios Antitumorais Modelo de Xenoenxerto
12.
Nat Commun ; 8: 15981, 2017 07 17.
Artigo em Inglês | MEDLINE | ID: mdl-28714471

RESUMO

Mutations in homologous recombination (HR) genes BRCA1 and BRCA2 predispose to tumorigenesis. HR-deficient cancers are hypersensitive to Poly (ADP ribose)-polymerase (PARP) inhibitors, but can acquire resistance and relapse. Mechanistic understanding how PARP inhibition induces cytotoxicity in HR-deficient cancer cells is incomplete. Here we find PARP inhibition to compromise replication fork stability in HR-deficient cancer cells, leading to mitotic DNA damage and consequent chromatin bridges and lagging chromosomes in anaphase, frequently leading to cytokinesis failure, multinucleation and cell death. PARP-inhibitor-induced multinucleated cells fail clonogenic outgrowth, and high percentages of multinucleated cells are found in vivo in remnants of PARP inhibitor-treated Brca2-/-;p53-/- and Brca1-/-;p53-/- mammary mouse tumours, suggesting that mitotic progression promotes PARP-inhibitor-induced cell death. Indeed, enforced mitotic bypass through EMI1 depletion abrogates PARP-inhibitor-induced cytotoxicity. These findings provide insight into the cytotoxic effects of PARP inhibition, and point at combination therapies to potentiate PARP inhibitor treatment of HR-deficient tumours.


Assuntos
Anáfase/efeitos dos fármacos , Proteína BRCA1/genética , Proteína BRCA2/genética , Neoplasias da Mama/genética , Citocinese/efeitos dos fármacos , Dano ao DNA/efeitos dos fármacos , Neoplasias Mamárias Animais/genética , Neoplasias Mamárias Experimentais/genética , Inibidores de Poli(ADP-Ribose) Polimerases/farmacologia , Animais , Neoplasias da Mama/tratamento farmacológico , Linhagem Celular Tumoral , Feminino , Células HeLa , Humanos , Camundongos , Camundongos Knockout , Mitose/efeitos dos fármacos , Inibidores de Poli(ADP-Ribose) Polimerases/uso terapêutico , Reparo de DNA por Recombinação/genética , Proteína Supressora de Tumor p53/genética , Proteínas Supressoras de Tumor/genética
13.
Nat Commun ; 8: 15983, 2017 07 17.
Artigo em Inglês | MEDLINE | ID: mdl-28714477

RESUMO

Failure to restart replication forks stalled at genomic regions that are difficult to replicate or contain endogenous DNA lesions is a hallmark of BRCA2 deficiency. The nucleolytic activity of MUS81 endonuclease is required for replication fork restart under replication stress elicited by exogenous treatments. Here we investigate whether MUS81 could similarly facilitate DNA replication in the context of BRCA2 abrogation. Our results demonstrate that replication fork progression in BRCA2-deficient cells requires MUS81. Failure to complete genome replication and defective checkpoint surveillance enables BRCA2-deficient cells to progress through mitosis with under-replicated DNA, which elicits severe chromosome interlinking in anaphase. MUS81 nucleolytic activity is required to activate compensatory DNA synthesis during mitosis and to resolve mitotic interlinks, thus facilitating chromosome segregation. We propose that MUS81 provides a mechanism of replication stress tolerance, which sustains survival of BRCA2-deficient cells and can be exploited therapeutically through development of specific inhibitors of MUS81 nuclease activity.


Assuntos
Proteína BRCA2/genética , Segregação de Cromossomos/genética , Dano ao DNA , Replicação do DNA , Proteínas de Ligação a DNA/genética , DNA/metabolismo , Endonucleases/genética , Anáfase , Linhagem Celular Tumoral , Células HeLa , Humanos , Mitose
14.
J Med Chem ; 60(9): 3626-3635, 2017 05 11.
Artigo em Inglês | MEDLINE | ID: mdl-28445046

RESUMO

G-quadruplex stabilizers are an established opportunity in anticancer chemotherapy. To circumvent the antiproliferative effects of G4 ligands, cancer cells recruit PARP enzymes at telomeres. Herein, starting from the structural similarity of a potent G4 ligand previously discovered by our group and a congeneric PARP inhibitor, a library of derivatives was synthesized to discover the first dual G4/PARP ligand. We demonstrate that a properly decorated thieno[3,2-c]quinolin-4(5H)-one stabilizes the G4 fold in vitro and in cells, induces a DNA damage response localized to telomeres, inhibits PARylation in cells, and has an antiproliferative effect in BRCA2 deficient tumor cells.


Assuntos
Antineoplásicos/farmacologia , Quadruplex G , Inibidores de Poli(ADP-Ribose) Polimerases/farmacologia , Antineoplásicos/química , Linhagem Celular Tumoral , Descoberta de Drogas , Ensaios de Seleção de Medicamentos Antitumorais , Transferência Ressonante de Energia de Fluorescência , Imunofluorescência , Humanos , Inibidores de Poli(ADP-Ribose) Polimerases/química
15.
Nat Struct Mol Biol ; 23(8): 755-757, 2016 08.
Artigo em Inglês | MEDLINE | ID: mdl-27322732

RESUMO

The tumor suppressor BRCA2 plays a key role in genome integrity by promoting replication-fork stability and homologous recombination (HR) DNA repair. Here we report that human cancer cells lacking BRCA2 rely on the Fanconi anemia protein FANCD2 to limit replication-fork progression and genomic instability. Our results identify a new role of FANCD2 in limiting constitutive replication stress in BRCA2-deficient cells, thereby affecting cell survival and treatment responses.


Assuntos
Proteína BRCA2/metabolismo , Proteína do Grupo de Complementação D2 da Anemia de Fanconi/fisiologia , Antineoplásicos/farmacologia , Linhagem Celular Tumoral , Sobrevivência Celular , Dano ao DNA , Replicação do DNA , Genoma Humano , Instabilidade Genômica , Células HEK293 , Humanos , Ftalazinas/farmacologia , Piperazinas/farmacologia
16.
EMBO J ; 35(9): 909-23, 2016 05 02.
Artigo em Inglês | MEDLINE | ID: mdl-27037238

RESUMO

The Fanconi anemia (FA) pathway plays a central role in the repair of DNA interstrand crosslinks (ICLs) and regulates cellular responses to replication stress. Homologous recombination (HR), the error-free pathway for double-strand break (DSB) repair, is required during physiological cell cycle progression for the repair of replication-associated DNA damage and protection of stalled replication forks. Substantial crosstalk between the two pathways has recently been unravelled, in that key HR proteins such as the RAD51 recombinase and the tumour suppressors BRCA1 and BRCA2 also play important roles in ICL repair. Consistent with this, rare patient mutations in these HR genes cause FA pathologies and have been assigned FA complementation groups. Here, we focus on the clinical and mechanistic implications of the connection between these two cancer susceptibility syndromes and on how these two molecular pathways of DNA replication and repair interact functionally to prevent genomic instability.


Assuntos
Enzimas Reparadoras do DNA/genética , Reparo do DNA , Proteínas de Grupos de Complementação da Anemia de Fanconi/genética , Predisposição Genética para Doença , Recombinação Homóloga , Neoplasias/genética , Enzimas Reparadoras do DNA/metabolismo , Proteínas de Grupos de Complementação da Anemia de Fanconi/metabolismo , Humanos , Redes e Vias Metabólicas
17.
Mol Cell ; 61(3): 449-460, 2016 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-26748828

RESUMO

G-quadruplex (G4)-forming genomic sequences, including telomeres, represent natural replication fork barriers. Stalled replication forks can be stabilized and restarted by homologous recombination (HR), which also repairs DNA double-strand breaks (DSBs) arising at collapsed forks. We have previously shown that HR facilitates telomere replication. Here, we demonstrate that the replication efficiency of guanine-rich (G-rich) telomeric repeats is decreased significantly in cells lacking HR. Treatment with the G4-stabilizing compound pyridostatin (PDS) increases telomere fragility in BRCA2-deficient cells, suggesting that G4 formation drives telomere instability. Remarkably, PDS reduces proliferation of HR-defective cells by inducing DSB accumulation, checkpoint activation, and deregulated G2/M progression and by enhancing the replication defect intrinsic to HR deficiency. PDS toxicity extends to HR-defective cells that have acquired olaparib resistance through loss of 53BP1 or REV7. Altogether, these results highlight the therapeutic potential of G4-stabilizing drugs to selectively eliminate HR-compromised cells and tumors, including those resistant to PARP inhibition.


Assuntos
Aminoquinolinas/farmacologia , Antineoplásicos/farmacologia , Proteína BRCA1/deficiência , Proteína BRCA2/deficiência , Biomarcadores Tumorais/deficiência , Quadruplex G/efeitos dos fármacos , Neoplasias/tratamento farmacológico , Ácidos Picolínicos/farmacologia , Animais , Proteína BRCA1/genética , Proteína BRCA2/genética , Biomarcadores Tumorais/genética , Proliferação de Células/efeitos dos fármacos , Quebras de DNA de Cadeia Dupla , Relação Dose-Resposta a Droga , Resistencia a Medicamentos Antineoplásicos , Pontos de Checagem da Fase G2 do Ciclo Celular/efeitos dos fármacos , Células HEK293 , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/genética , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteínas Mad2/genética , Proteínas Mad2/metabolismo , Masculino , Camundongos Nus , Terapia de Alvo Molecular , Neoplasias/genética , Neoplasias/metabolismo , Neoplasias/patologia , Inibidores de Poli(ADP-Ribose) Polimerases/farmacologia , Interferência de RNA , Telômero/efeitos dos fármacos , Telômero/genética , Telômero/metabolismo , Fatores de Tempo , Transfecção , Carga Tumoral/efeitos dos fármacos , Proteína 1 de Ligação à Proteína Supressora de Tumor p53 , Ensaios Antitumorais Modelo de Xenoenxerto
19.
EMBO J ; 34(3): 410-24, 2015 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-25582120

RESUMO

Loss of telomere protection occurs during physiological cell senescence and ageing, due to attrition of telomeric repeats and insufficient retention of the telomere-binding factor TRF2. Subsequently formed telomere fusions trigger rampant genomic instability leading to cell death or tumorigenesis. Mechanistically, telomere fusions require either the classical non-homologous end-joining (C-NHEJ) pathway dependent on Ku70/80 and LIG4, or the alternative non-homologous end-joining (A-NHEJ), which relies on PARP1 and LIG3. Here, we show that the tumour suppressor BRCA1, together with its interacting partner CtIP, both acting in end resection, also promotes end-joining of uncapped telomeres. BRCA1 and CtIP do not function in the ATM-dependent telomere damage signalling, nor in telomere overhang removal, which are critical for telomere fusions by C-NHEJ. Instead, BRCA1 and CtIP act in the same pathway as LIG3 to promote joining of de-protected telomeres by A-NHEJ. Our work therefore ascribes novel roles for BRCA1 and CtIP in end-processing and fusion reactions at uncapped telomeres, underlining the complexity of DNA repair pathways that act at chromosome ends lacking protective structures. Moreover, A-NHEJ provides a mechanism of previously unanticipated significance in telomere dysfunction-induced genome instability.


Assuntos
Proteína BRCA1/metabolismo , Proteínas de Transporte/metabolismo , Proteínas de Ciclo Celular/metabolismo , Reparo do DNA por Junção de Extremidades/fisiologia , Telômero/metabolismo , Animais , Antígenos Nucleares/genética , Antígenos Nucleares/metabolismo , Proteínas Mutadas de Ataxia Telangiectasia/genética , Proteínas Mutadas de Ataxia Telangiectasia/metabolismo , Proteína BRCA1/genética , Proteínas de Transporte/genética , Proteínas de Ciclo Celular/genética , Dano ao DNA , DNA Ligase Dependente de ATP , DNA Ligases/genética , DNA Ligases/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Células HEK293 , Humanos , Autoantígeno Ku , Camundongos , Camundongos Knockout , Poli(ADP-Ribose) Polimerase-1 , Poli(ADP-Ribose) Polimerases/genética , Poli(ADP-Ribose) Polimerases/metabolismo , Proteínas de Ligação a Poli-ADP-Ribose , Telômero/genética , Proteínas de Xenopus
20.
Chromosoma ; 124(2): 119-30, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25430998

RESUMO

Telomeres protect the ends of linear chromosomes against loss of genetic information and inappropriate processing as damaged DNA and are therefore crucial to the maintenance of chromosome integrity. In addition to providing a pathway for genome-wide DNA repair, homologous recombination (HR) plays a key role in telomere replication and capping. Consistent with this, the genomic instability characteristic of HR-deficient cells and tumours is driven in part by telomere dysfunction. Here, we discuss the mechanisms by which HR modulates the response to intrinsic cellular challenges that arise during telomere replication, as well as its impact on the assembly of telomere protective structures. How normal and tumour cells differ in their ability to maintain telomeres is deeply relevant to the search for treatments that would selectively eliminate cells whose capacity for HR-mediated repair has been compromised.


Assuntos
Recombinação Homóloga/genética , Telômero/genética , Animais , DNA/genética , Dano ao DNA , Reparo do DNA , Replicação do DNA , Instabilidade Genômica , Humanos , Mamíferos/genética , Neoplasias/genética , Telômero/metabolismo , Proteínas de Ligação a Telômeros/genética , Proteínas de Ligação a Telômeros/metabolismo
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