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Whole genome sequencing of a breast cancer cohort with known functional homologous recombination status

ABSTRACT: Optimal patient selection for PARP inhibitors and double strand break (DSB) inducing chemotherapy is of great clinical importance. In principle, the use of these therapies can be extended beyond germline BRCA1/2 mutated cancers. Although several methods for detection of BRCA-like tumors have been developed, a golden standard is lacking. We have developed the RECAP test, a functional HR assay exploiting the formation of RAD51 foci in proliferating cells after ex vivo irradiation of fresh primary breast cancer (BrC) tissue. The RECAP test seems robust and has an advantage over genetic tests, due to its functional character for exploring the HR phenotype. Another type of HRD test is the BRCAness classifier, which is based on specific genomic patterns derived from copy number data of BRCA1/2 mutated BrCs that also occur in sporadic cancers. The BRCAness classifier is a robust test that is easily applicable in the clinic and has also been validated to predict in vivo response to high dose chemotherapy in clinical trials. More recently, a new HRD test based on genomic signatures which can be extracted from whole genome sequencing has been published, HRDetect. Studies comparing these different HRD tests within the same cohort of patients do not yet exist. Here, we have the unique opportunity to compare three HRD tests within the same cohort. We aim to compare three different HRD tests (RECAP, BRCAness classifier and HRDetect) within the same cohort of primary BrCs (n=41). As a secondary aim, we will analyze additional genetic alterations in HRD tumors (both BRCA-deficient and BRCA-proficient HRD tumors).

PROVIDER: EGAS00001005572 | EGA |

REPOSITORIES: EGA

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Breast cancer DNA repair

Project description:Tumors of germline BRCA1/2 mutated carriers show homologous recombination (HR) deficiency (HRD), resulting in impaired DNA double strand break (DSB) repair and high sensitivity to Poly-(ADP-Ribose)-Polymerase (PARP) inhibitors. Although this therapy is expected to be effective beyond germline BRCA1/2 mutated carriers, a robust validated test to detect HRD tumors is lacking. In the present study we therefore evaluated a functional HR assay exploiting the formation of RAD51 foci in proliferating cells after ex vivo irradiation of fresh breast cancers (BrC) tissue: the RECAP test.Methods Fresh samples of 170 primary BrC were analyzed using the RECAP test. The molecular explanation for the HRD phenotype was investigated by exploring BRCA deficiencies, mutational signatures, tumor infiltrating lymphocytes (TILs) and microsatellite instability (MSI).Results RECAP was completed successfully in 148 out of 170 samples (87%). 24 tumors showed HRD (16%), while 6 tumors were HR intermediate (HRi) (4%). HRD was explained by BRCA deficiencies (mutations, promoter hypermethylation, deletions) in 16 cases. Several non-BRCA deficient HRD tumors showed BRCAness mutational signatures, suggesting that they are also bona fide HRD cases. HRD tumors showed an increased incidence of high TIL counts (p=0.023) compared to HR proficient (HRP) tumors and MSI was more frequently observed in the HRD group (2/20, 10%) than expected in BrC (1%) (p=0.017).Conclusion The RECAP test is a robust assay detecting both BRCA1/2 deficient and BRCA1/2 proficient HRD tumors, suggesting that this test identifies approximately 50% more patients that may benefit from PARPi treatment than BRCA gene testing only.

| EGAS00001002792 | EGA

A gene expression profile of BRCAness that is associated with outcome in ovarian cancer

Project description:A gene expression profile of BRCAness was defined in publicly available expression data of 61 patients with epithelial ovarian cancer (34 patients with BRCA-1 or BRCA-2 mutations and 27 patients with sporadic disease). This dataset is publicly available at http://jnci.oxfordjournals.org/cgi/content/full/94/13/990/DC1 The BRCAness profile was correlated with outcome in 70 patients with epithelial ovarian cancer and known outcome data. Correlation with outcome

2010-07-11 | E-GEOD-19829 | biostudies-arrayexpress

A gene expression profile of BRCAness that is associated with outcome in ovarian cancer

2010-07-11 | GSE19829 | GEO

CDK12 Regulates DNA Repair Genes by Suppressing Intronic Polyadenylation

Project description:Mutations that attenuate DNA repair by homologous recombination (HR) promote tumorigenesis and sensitize cells to chemotherapeutic agents that cause replication fork collapse, a phenotype known as “BRCAness.” BRCAness tumors arise from loss-of-function mutations in 22 genes. Of these genes, all but one (Cdk12) directly function in the HR repair pathway. Cdk12 phosphorylates Serine 2 of the RNA Polymerase II (RNAPII) C-terminal domain (CTD) heptapeptide repeat, a modification that regulates transcription elongation, splicing, and cleavage/polyadenylation. Genome-wide expression studies suggest that Cdk12 depletion abrogates the expression of several HR genes relatively specifically, blunting HR repair. This observation suggests that Cdk12 mutational status may predict tumor sensitivity to targeted treatments against BRCAness, such as Parp 1 inhibitors, and that small-molecule inhibitors of Cdk12 may induce sensitization of otherwise HR-competent tumors to these treatments. Despite this growing clinical interest, the mechanism behind the apparent specificity of Cdk12 in regulating HR genes remains unknown. Here we find that Cdk12 globally suppresses intronic polyadenylation events, enabling the production of full-length gene products. Many HR genes harbor significantly more intronic polyadenylation sites compared to all expressed genes, and the cumulative effect of these sites accounts for the increased sensitivity of HR gene expression to Cdk12 loss. Finally, we find evidence that Cdk12 loss-of-function mutations cause increased intronic polyadenylation within HR genes in human tumors, suggesting that this mechanism is conserved. This work clarifies the biological function of CDK12 and underscores its potential both as a chemotherapeutic target and as a tumor biomarker.

2018-11-28 | GSE116017 | GEO

Expression data of CHK1 shRNA knockdown and control shRNA in U2OS cells

Project description:Homologous recombination-mediated DNA repair deficiency (HRD) predisposes to cancer development, but also provides therapeutic opportunities. Here, we identified an HRD gene signature that robustly predicted HRD status. Unexpectedly, concurrent loss of PTEN in BRCA1-deficient cells might extensively rewire the HR repair network and confer resistance to PARP inhibitor, partially through over-expression of TTK. We used the HRD gene signature as a drug discovery tool and found several PARP-inhibitor-synergizing agents through the connectivity map. Thus gene expression profiling can be used to define the functional status of the HR repair network providing prognostic and therapeutic information.

2014-01-24 | GSE54267 | GEO

Expression data of BRCA1 shRNA and Rad51 shRNA knockdown and control shRNA in MCF-10A cells

2014-01-24 | GSE54266 | GEO

Expression data of BRCA1 shRNA and PTEN shRNA single knockdown, BRCA1_PTEN shRNA double knockdowns and control shRNA in MCF-10A cells

2014-01-24 | GSE54265 | GEO

Expression data of Brti1 shRNA knockdown and control shRNA in MCF-10A cells

Project description:Homologous recombination-mediated DNA repair deficiency (HRD) predisposes to cancer development, but also provides therapeutic opportunities Here, we identified an HRD gene signature that robustly predicted HRD status Unexpectedly, concurrent loss of PTEN in BRCA1-deficient cells might extensively rewire the HR repair network and confer resistance to PARP inhibitor, partially through over-expression of TTK We used the HRD gene signature as a drug discovery tool and found several PARP-inhibitor-synergizing agents through the connectivity map Thus gene expression profiling can be used to define the functional status of the HR repair network providing prognostic and therapeutic information

2014-01-24 | GSE54264 | GEO

Expression data of ATM, ATR, CHK1, CHK2, and 53BP1 shRNA knockdown and control shRNA in MCF-10A cells

2014-01-24 | GSE54268 | GEO

Comparison of aCGH profiles from KB1C61GP, KB1P and KP mouse mammary tumors

Project description:While BRCA-related cancers respond well to double-strand break (DSB) inducing agents, resistance is a serious clinical problem. One mechanism of resistance is reversion of the BRCA1 mutation, suggesting that BRCA1 function is required for resistance. Here we show that secondary Brca1 mutations are not always necessary, since residual activity of the mutant BRCA1 protein can be sufficient for tumor cells to withstand treatment. Genomic profiling and RAD51 foci formation are currently seen as potential biomarkers to stratify patients for therapies targeting homologous recombination deficiency (HRD). However, we show that while mouse mammary tumors with different Brca1 mutations have identical genomic profiles, they respond considerably different to HRD targeted therapy. It may therefore be useful to stratify patients according to functional assays and the underlying BRCA1 mutation. We performed aCGH on mammary tumor DNA from KB1C61GP (n=20), littermate KB1P (n=18) and KP mice (n=19). Spleen DNA of the same animal was used as control material.

2011-12-01 | E-GEOD-30710 | biostudies-arrayexpress

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