Radiosensitivity is an acquired vulnerability of PARPi-resistant BRCA1-deficient tumors

Barazas, Marco; Gasparini, Alessia; Huang, Yike; Küçükosmanoğlu, Aslı; Annunziato, Stefano; Bouwman, Peter; Sol, Wendy; Kersbergen, Ariena; Proost, Natalie; Ven, Marieke van de; Jonkers, Jos; Borst, Gerben R.; Rottenberg, Sven

doi:10.1101/370577

Cited by 5 publications

(4 citation statements)

References 25 publications

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“…The K14 cell line was generated by removing breast tumors from K14-Cre Brca1 f/f Trp53 f/f females, seeding single-cell suspensions in DMEM (Corning) supplemented with 10% FBS, and passaging until phenotypical and growth rate stability were achieved (22). The murine isogenic cell line pair KB1P-G3 −/+ BRCA1 was generated and maintained as previously described (12,13). All cell lines were routinely tested for the presence of Mycoplasma using the MycoAlert Mycoplasma Detection Kit (Lonza).…”

Section: Cell Culturementioning

confidence: 99%

PARP Inhibitor Efficacy Depends on CD8+ T-cell Recruitment via Intratumoral STING Pathway Activation in BRCA-Deficient Models of Triple-Negative Breast Cancer

et al. 2019

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Combinatorial clinical trials of PARP inhibitors with immunotherapies are ongoing, yet the immunomodulatory effects of PARP inhibition have been incompletely studied. Here, we sought to dissect the mechanisms underlying PARP inhibitor-induced changes in the tumor microenvironment of BRCA1-defi cient triple-negative breast cancer (TNBC). We demonstrate that the PARP inhibitor olaparib induces CD8 + T-cell infi ltration and activation in vivo , and that CD8 + T-cell depletion severely compromises antitumor effi cacy. Olaparib-induced T-cell recruitment is mediated through activation of the cGAS/STING pathway in tumor cells with paracrine activation of dendritic cells and is more pronounced in HR-defi cient compared with HR-profi cient TNBC cells and in vivo models. CRISPR-mediated knockout of STING in cancer cells prevents proinfl ammatory signaling and is suffi cient to abolish olaparib-induced T-cell infi ltration in vivo. These fi ndings elucidate an additional mechanism of action of PARP inhibitors and provide a rationale for combining PARP inhibition with immunotherapies for the treatment of TNBC. SIGNIFICANCE: This work demonstrates cross-talk between PARP inhibition and the tumor microenvironment related to STING/TBK1/IRF3 pathway activation in cancer cells that governs CD8 + T-cell recruitment and antitumor effi cacy. The data provide insight into the mechanism of action of PARP inhibitors in BRCA-associated breast cancer.

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Section: Cell Culturementioning

confidence: 99%

PARP Inhibitor Efficacy Depends on CD8+ T-cell Recruitment via Intratumoral STING Pathway Activation in BRCA-Deficient Models of Triple-Negative Breast Cancer

et al. 2019

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“…A recent study on radiotherapy resistance mechanisms in Brca1-deficient mouse mammary tumors showed that this resistance is not caused by Tp53bp1 mutations. This observation directed experiments showing that PARPi-resistant tumors with BRCA1 and TP53BP1 mutations are still sensitive to radiotherapy [65,100]. This vulnerability opens opportunities to treat HR-restored PARPi-resistant tumors with irradiation, and further research should focus on validating this effect in other conditions of HR reactivation, notably following loss of factors such as Shieldin and DYNLL1.…”

Section: Acquired Vulnerabilities Of Parpi-resistant Tumorsmentioning

confidence: 99%

PARP Inhibitor Resistance: A Tug-of-War in BRCA-Mutated Cells

Noordermeer

Attikum

2019

Trends in Cell Biology

345

285

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Poly-(ADP)-ribose polymerase (PARP) inhibition is synthetic lethal with deficiency for homologous recombination (HR), a pathway essential for DNA double-strand break repair. PARP inhibitors (PARPi) therefore hold great promise for the treatment of tumors with disruptive mutations in BRCA1/2 or other HR factors. Unfortunately, PARPi resistance has proved to be a major problem in the clinic. Knowledge about PARPi resistance is expanding quickly, revealing four main mechanisms that alter drug availability, affect (de)PARylation enzymes, restore HR, or restore replication fork stability. We discuss how studies on resistance mechanisms have yielded important insights into the regulation of DNA double-strand break (DSB) repair and replication fork protection, and how these studies could pave the way for novel treatment options to target resistance mechanisms or acquired vulnerabilities. Defective DSB Repair and Cancer Genomic instability is one of the enabling characteristics of tumor development [1]. To maintain genomic integrity, cells are equipped with multiple mechanisms to repair a wide variety of DNA lesions caused by exogenous and endogenous events. One particularly toxic lesion is the DNA double-strand break (DSB; see Glossary). This lesion can be caused by ionizing irradiation and genotoxic chemicals, but can also arise as an intermediate of resolving stalled or collapsed replication forks (replication fork instability) [2]. If left unrepaired or are repaired incorrectly, DSBs can give rise to mutations, deletions, amplifications, and chromosomal translocations, leading to various outcomes such as senescence, cell death, or malignant transformation. Over 30 years ago, Marie-Claire King and colleagues discovered the linkage between familial earlyonset breast cancer and the genomic region 17q21 [3]. We now know that the gene affected is BRCA1, and that mutations in this gene are not only linked to breast cancer but also to familial cases of ovarian cancer and sporadic tumors of different origins [4-7]. BRCA1 is an essential factor in the repair of DSBs via homologous recombination (HR) (see Box 1 for a more detailed overview of DSB repair). Moreover, homozygous loss of BRCA1 is not tolerated during human and mouse embryonic development [8]. This BRCA1 survival-dependency can be partially overcome by concomitant loss of p53 [9]. Importantly, mouse models with mammary gland-specific loss of these genes show increased breast tumor formation [8]. Indeed, in clinical tumor samples, BRCA1 mutations often co-occurbut not alwayswith TP53 mutations [8,10]. Epigenetic silencing of BRCA1 expression via promoter hypermethylation is another way of reducing BRCA1 activity, and this has been shown to occur frequently in tumors [6,11,12]. In addition to aberrations in BRCA1, genes encoding many more factors involved in HR, such as BRCA2, PALB2, and RAD51, are known to be affected in a wide variety of tumors. All these tumors display severe chromosomal instability as a result of deregulated HR, a phenotype referred to as 'BRCAne...

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“…Counteracting PARPi‐resistant cancers currently represents a major clinical challenge. In addition to pyridostatin, the G4 ligand CX‐5461 (Zimmer et al , 2016; Xu et al , 2017), the alkylating agent chlorambucil (Tacconi et al , 2019), ionising radiation (Dev et al , 2018; Barazas et al , 2019) and cisplatin (Bunting et al , 2012; Cruz et al , 2018; Dev et al , 2018) have been reported as DNA damaging treatments that can counteract PARPi resistance in BRCA1/2‐deficient cells and tumours. However, only one clinical trial has so far investigated the cisplatin sensitivity in PARPi‐resistant BRCA1‐deficient tumours (Ang et al , 2013).…”

Section: Discussionmentioning

confidence: 99%

Anti‐tumoural activity of the G‐quadruplex ligand pyridostatin against BRCA1/2‐deficient tumours

et al. 2022

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The cells with compromised BRCA1 or BRCA2 (BRCA1/2) function accumulate stalled replication forks, which leads to replication‐associated DNA damage and genomic instability, a signature of BRCA1/2‐mutated tumours. Targeted therapies against BRCA1/2‐mutated tumours exploit this vulnerability by introducing additional DNA lesions. Because homologous recombination (HR) repair is abrogated in the absence of BRCA1 or BRCA2, these lesions are specifically lethal to tumour cells, but not to the healthy tissue. Ligands that bind and stabilise G‐quadruplexes (G4s) have recently emerged as a class of compounds that selectively eliminate the cells and tumours lacking BRCA1 or BRCA2. Pyridostatin is a small molecule that binds G4s and is specifically toxic to BRCA1/2‐deficient cells in vitro. However, its in vivo potential has not yet been evaluated. Here, we demonstrate that pyridostatin exhibits a high specific activity against BRCA1/2‐deficient tumours, including patient‐derived xenograft tumours that have acquired PARP inhibitor (PARPi) resistance. Mechanistically, we demonstrate that pyridostatin disrupts replication leading to DNA double‐stranded breaks (DSBs) that can be repaired in the absence of BRCA1/2 by canonical non‐homologous end joining (C‐NHEJ). Consistent with this, chemical inhibitors of DNA‐PKcs, a core component of C‐NHEJ kinase activity, act synergistically with pyridostatin in eliminating BRCA1/2‐deficient cells and tumours. Furthermore, we demonstrate that pyridostatin triggers cGAS/STING‐dependent innate immune responses when BRCA1 or BRCA2 is abrogated. Paclitaxel, a drug routinely used in cancer chemotherapy, potentiates the in vivo toxicity of pyridostatin. Overall, our results demonstrate that pyridostatin is a compound suitable for further therapeutic development, alone or in combination with paclitaxel and DNA‐PKcs inhibitors, for the benefit of cancer patients carrying BRCA1/2 mutations.

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Radiosensitivity is an acquired vulnerability of PARPi-resistant BRCA1-deficient tumors

Cited by 5 publications

References 25 publications

PARP Inhibitor Efficacy Depends on CD8+ T-cell Recruitment via Intratumoral STING Pathway Activation in BRCA-Deficient Models of Triple-Negative Breast Cancer

PARP Inhibitor Efficacy Depends on CD8+ T-cell Recruitment via Intratumoral STING Pathway Activation in BRCA-Deficient Models of Triple-Negative Breast Cancer

PARP Inhibitor Resistance: A Tug-of-War in BRCA-Mutated Cells

Anti‐tumoural activity of the G‐quadruplex ligand pyridostatin against BRCA1/2‐deficient tumours

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