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A transcription-based mechanism for oncogenic β-catenin-induced lethality in BRCA1/2-deficient cells.

ABSTRACT: 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 β-catenin, an oncogene of the WNT signalling pathway, inhibits proliferation of BRCA1/2-deficient cells. RNA-seq analyses revealed β-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, β-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 β-catenin toxicity in cancer cells with compromised BRCA1/2 function is driven by transcriptional alterations that cause aberrant replication and inflict DNA damage.

SUBMITTER: Dagg RA

PROVIDER: S-EPMC8363664 | biostudies-literature |

REPOSITORIES: biostudies-literature

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A transcription-based mechanism for oncogene-induced lethality in BRCA1/2-deficient cells

Project description:This SuperSeries is composed of the SubSeries listed below.

2021-04-01 | GSE153736 | GEO

A transcription-based mechanism for oncogene-induced lethality in BRCA1/2-deficient cells [RNA-seq]

Project description:Heterozygous germline mutations in BRCA1 or BRCA2 predispose to breast, ovarian, as well as other cancers. The main physiological function of BRCA1 and BRCA2 is to facilitate DNA replication, by stabilising and re-starting stalled replication forks. Consequently, inactivation of either BRCA1 or BRCA2 genes leads to replication pathologies and accumulation of DNA double strand breaks. Similar to BRCA1/2 inactivation, oncogene overexpression interferes with replication and inflicts DNA damage. It remains unclear how the replication defects in the two settings differ from each other and what is their combined effect on cell viability. Here, we report that accumulation of β-catenin, an oncogene of the WNT signalling pathway, is synthetically lethal with BRCA1/2 inactivation. We identify two transcription-dependent mechanisms that mediate oncogene toxicity in the context of BRCA1/2 deficiency. Firstly, accumulation of β-catenin activates E2F-dependent transcription, which accelerates G1/S transition, thus counteracting the delayed S-phase entry caused by BRCA1/2 abrogation. This, in turn, triggers illegitimate origin firing leading to fork collapse, DNA damage and deregulation of gene expression. Secondly, we find that β-catenin accumulation suppresses transcription of CDKN1A gene encoding p21, a modulator of fork progression. Decreased replication rates represent a hallmark of BRCA2 deficiency. Through p21 downregulation, β-catenin accelerates replication fork progression in BRCA2-deficient cells, thereby inflicting DNA damage and triggering cell death. Thus, our results demonstrate that oncogene-driven premature S-phase entry and increased replication rate are lethal in the context of BRCA1/2 abrogation, which explains the mutual exclusivity between oncogene activation and BRCA1/2 gene mutations in human tumours.

2021-04-01 | GSE153735 | GEO

A transcription-based mechanism for oncogene-induced lethality in BRCA1/2-deficient cells [EdU-seq]

Project description:Heterozygous germline mutations in BRCA1 or BRCA2 predispose to breast, ovarian, as well as other cancers. The main physiological function of BRCA1 and BRCA2 is to facilitate DNA replication, by stabilising and re-starting stalled replication forks. Consequently, inactivation of either BRCA1 or BRCA2 genes leads to replication pathologies and accumulation of DNA double strand breaks. Similar to BRCA1/2 inactivation, oncogene overexpression interferes with replication and inflicts DNA damage. It remains unclear how the replication defects in the two settings differ from each other and what is their combined effect on cell viability. Here, we report that accumulation of β-catenin, an oncogene of the WNT signalling pathway, is synthetically lethal with BRCA1/2 inactivation. We identify two transcription-dependent mechanisms that mediate oncogene toxicity in the context of BRCA1/2 deficiency. Firstly, accumulation of -catenin activates E2F-dependent transcription, which accelerates G1/S transition, thus counteracting the delayed S-phase entry caused by BRCA1/2 abrogation. This, in turn, triggers illegitimate origin firing leading to fork collapse, DNA damage and deregulation of gene expression. Secondly, we find that β-catenin accumulation suppresses transcription of CDKN1A gene encoding p21, a modulator of fork progression. Decreased replication rates represent a hallmark of BRCA2 deficiency. Through p21 downregulation, β-catenin accelerates replication fork progression in BRCA2-deficient cells, thereby inflicting DNA damage and triggering cell death. Thus, our results demonstrate that oncogene-driven premature S-phase entry and increased replication rate are lethal in the context of BRCA1/2 abrogation, which explains the mutual exclusivity between oncogene activation and BRCA1/2 gene mutations in human tumours.

2021-04-01 | GSE153734 | GEO

A transcription-based mechanism for oncogene-induced lethality in BRCA1/2-deficient cells

Project description:A transcription-based mechanism for oncogene-induced lethality in BRCA1/2-deficient cells

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A transcription-based mechanism for oncogene-induced lethality in BRCA1/2-deficient cells [RNA-seq]

Project description:A transcription-based mechanism for oncogene-induced lethality in BRCA1/2-deficient cells [RNA-seq]

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A transcription-based mechanism for oncogene-induced lethality in BRCA1/2-deficient cells [EdU-seq]

Project description:A transcription-based mechanism for oncogene-induced lethality in BRCA1/2-deficient cells [EdU-seq]

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Covalent Degrader of the Oncogenic Transcription Factor β-Catenin.

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| S-EPMC10635039 | biostudies-literature

MiR223-3p promotes synthetic lethality in BRCA1-deficient cancers.

Project description:Defects in DNA repair give rise to genomic instability, leading to neoplasia. Cancer cells defective in one DNA repair pathway can become reliant on remaining repair pathways for survival and proliferation. This attribute of cancer cells can be exploited therapeutically, by inhibiting the remaining repair pathway, a process termed synthetic lethality. This process underlies the mechanism of the Poly-ADP ribose polymerase-1 (PARP1) inhibitors in clinical use, which target BRCA1 deficient cancers, which is indispensable for homologous recombination (HR) DNA repair. HR is the major repair pathway for stressed replication forks, but when BRCA1 is deficient, stressed forks are repaired by back-up pathways such as alternative nonhomologous end-joining (aNHEJ). Unlike HR, aNHEJ is nonconservative, and can mediate chromosomal translocations. In this study we have found that miR223-3p decreases expression of PARP1, CtIP, and Pso4, each of which are aNHEJ components. In most cells, high levels of microRNA (miR) 223-3p repress aNHEJ, decreasing the risk of chromosomal translocations. Deletion of the miR223 locus in mice increases PARP1 levels in hematopoietic cells and enhances their risk of unprovoked chromosomal translocations. We also discovered that cancer cells deficient in BRCA1 or its obligate partner BRCA1-Associated Protein-1 (BAP1) routinely repress miR223-3p to permit repair of stressed replication forks via aNHEJ. Reconstituting the expression of miR223-3p in BRCA1- and BAP1-deficient cancer cells results in reduced repair of stressed replication forks and synthetic lethality. Thus, miR223-3p is a negative regulator of the aNHEJ DNA repair and represents a therapeutic pathway for BRCA1- or BAP1-deficient cancers.

| S-EPMC6717293 | biostudies-literature

β-catenin deficiency in hepatocytes aggravates hepatocarcinogenesis driven by oncogenic β-catenin and MET.

Project description:Both activating and inactivating mutations in catenin β1 (ctnnb1), which encodes β-catenin, have been implicated in liver tumorigenesis in humans and mice, although the underlying mechanisms are not fully understood. Herein, we show that deletion of endogenous β-catenin in hepatocytes aggravated hepatocellular carcinoma (HCC) development driven by an oncogenic version of β-catenin (CAT) in combination with the hepatocyte growth factor receptor MET proto-oncogene receptor tyrosine kinase (MET). Although the mitogenic signaling and cell cycle progression was modestly impaired after CAT/MET transfection, the β-catenin-deficient livers displayed changes in transcriptomes, increased DNA damage response, expanded Sox9+ cells, and up-regulation of protumorigenic cytokines, including interleukin-6 and transforming growth factor β1. These events eventually exacerbated CAT/MET-driven hepatocarcinogenesis in β-catenin-deficient livers, featured by up-regulation of extracellular signal-regulated kinase (Erk), protein kinase B (Akt), and Wnt/β-catenin signaling and cyclin D1 expression. The resultant mouse tumors showed similar transcriptomes to human HCC samples with concomitant CTNNB1 mutations and MET overexpression.ConclusionThese data argue that while dominantly activating mutants of β-catenin are oncogenic, inhibiting the oncogenic signaling pathway generates a pro-oncogenic microenvironment that may facilitate HCC recurrence following a targeted therapy of the primary tumor. An effective therapeutic strategy must require disruption of the oncogenic signaling in tumor cells and suppression of the secondary tumor-promoting stromal effects in the liver microenvironment. (Hepatology 2018;67:1807-1822).

| S-EPMC5906147 | biostudies-literature

RBM10 C761Y mutation induced oncogenic ASPM isoforms and regulated β-catenin signaling in cholangiocarcinoma.

Project description:BackgroundCholangiocarcinoma (CCA) comprises a heterogeneous group of biliary tract cancer. Our previous CCA mutation pattern study focused on genes in the post-transcription modification process, among which the alternative splicing factor RBM10 captured our attention. However, the roles of RBM10 wild type and mutations in CCA remain unclear.MethodsRBM10 mutation spectrum in CCA was clarified using our initial data and other CCA genomic datasets from domestic and international sources. Real-time PCR and tissue microarray were used to detect RBM10 clinical association. Function assays were conducted to investigate the effects of RBM10 wild type and mutations on CCA. RNA sequencing was to investigate the changes in alternative splicing events in the mutation group compared to the wild-type group. Minigene splicing reporter and interaction assays were performed to elucidate the mechanism of mutation influence on alternative splicing events.ResultsRBM10 mutations were more common in Chinese CCA populations and exhibited more protein truncation variants. RBM10 exerted a tumor suppressive effect in CCA and correlated with favorable prognosis of CCA patients. The overexpression of wild-type RBM10 enhanced the ASPM exon18 exon skipping event interacting with SRSF2. The C761Y mutation in the C2H2-type zinc finger domain impaired its interaction with SRSF2, resulting in a loss-of-function mutation. Elevated ASPM203 stabilized DVL2 and enhanced β-catenin signaling, which promoted CCA progression.ConclusionsOur results showed that RBM10C761Y-modulated ASPM203 promoted CCA progression in a Wnt/β-catenin signaling-dependent manner. This study may enhance the understanding of the regulatory mechanisms that link mutation-altering splicing variants to CCA.

| S-EPMC10993532 | biostudies-literature

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