Extensive Convergent Evolution of BRCA2 Reversion Mutations Under Therapeutic Pressure by PARP Inhibition and Platinum Chemotherapy
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ABSTRACT:
PROVIDER: PRJNA1019454 | ENA |
REPOSITORIES: ENA
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Project description:Breast cancer gene 2 (BRCA2) deleterious mutations confer sensitivity to poly(ADP-ribose) polymerase (PARP) inhibition due to its critical role in DNA repair. PARP inhibitor Olaparib is now approved and several other PARP inhibitors are now in different stages of clinical trials. Development of resistance to PARP inhibitors limits their clinical utility. The mechanism of resistance remains not fully understood. Here we show that amplification of mutant BRCA2 confers PARP inhibitor resistance. The amplification of mutant BRCA2 gene copies correlates with an increase in mutant BRCA2 expression and an increase in the levels of its interacting proteins PALB2 and RAD51. In addition, homologous recombination mediated DNA repair is rescued in these cells as evidenced by the formation of RAD51 focus formation. The overexpressed mutant BRCA2 is essential for the observed PARP inhibitor resistance because knockdown of its expression is sufficient to re-sensitize these cells to PARP inhibition. Collectively, our results indicate a new mechanism of resistance to PARP inhibitor in BRCA2 mutant cancer cells
2017-09-02 | GSE86394 | GEO
Project description:Reversion mutations that restore wild-type function of the BRCA gene have been described as a key mechanism of resistance to Poly(ADP-ribose) polymerase (PARP) inhibitor therapy in BRCA-associated cancers. Here, we report a case of a patient with metastatic castration-resistant prostate cancer (mCRPC) with a germline BRCA2 mutation who developed acquired resistance to PARP inhibition. Extensive genomic interrogation of cell-free DNA (cfDNA) and tissue at baseline, post-progression, and postmortem revealed ten unique BRCA2 reversion mutations across ten sites. While several of the reversion mutations were private to a specific site, nine out of ten tumors contained at least one mutation, suggesting a powerful clonal selection for reversion mutations in the presence of therapeutic pressure by PARP inhibition. Variable cfDNA shed was seen across tumor sites, emphasizing a potential shortcoming of cfDNA monitoring for PARPi resistance. This report provides a genomic portrait of the temporal and spatial heterogeneity of prostate cancer under the selective pressure of a PARP inhibition and exposes limitations in the current strategies for detection of reversion mutations.
| S-EPMC10866935 | biostudies-literature
Project description: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, BRCA2 inactivation in tumors is associated with uncontrolled cell proliferation. We set out to investigate this conundrum by exploring modalities of cell adaptation to loss of BRCA2 and focused on genome-wide transcriptome alterations. Human cells in which BRCA2 expression was inhibited using a doxycycline (DOX)-inducible shRNA for 4 or 28 days were subjected to RNA-seq analyses. Gene sets differentially expressed in BRCA2-deficient versus -proficient cells revealed a biphasic response to BRCA2 abrogation. The early, acute response consisted of downregulation of genes involved in cell cycle progression, DNA replication and repair and was associated with cell cycle arrest in G1. Surprisingly, the late, chronic response consisted exclusively of upregulation of innate immune response genes controlled by interferon. Activation of the cGAS-STING pathway detected in these cells further substantiated the concept that long-term BRCA2 abrogation triggers cell-intrinsic immune signaling. Importantly, we found that treatment with PARP inhibitors stimulated the interferon response in cells and tumors lacking BRCA2. We propose that PARP inhibitors suppress growth of BRCA2-deficient cells and tumors, in part, by activating interferon signaling.
2018-12-11 | GSE123631 | GEO
Project description:Sequential Platinum and PARP Inhibition Enhances PD1 Immunotherapy Efficacy in Murine Brca2 Mutated Pancreatic Cancer [RNAseq_2]
| PRJNA1282598 | ENA
Project description:Sequential Platinum and PARP Inhibition Enhances PD1 Immunotherapy Efficacy in Murine Brca2 Mutated Pancreatic Cancer [RNAseq_1]
| PRJNA1282596 | ENA
Project description:Alteration of the gene encoding BRCA2, a protein involved in homologous recombination (HR), by missense or nonsense mutations results in sensitivity of a subset of breast and ovarian cancers to platinating agents and poly(ADP-ribose) polymerase (PARP) inhibitors. Conversely, resistance to these agents is often accompanied by secondary BRCA2 mutations that restore a functional protein. Here we characterized clones derived from the BRCA2-mutant ovarian cancer line PEO1 by selection with the PARP inhibitor veliparib. Colony forming assays demonstrated cross-resistance of the resulting clones to multiple PARP inhibitors and cisplatin. Despite the continued presence of a 4965C>A (p.Y1655X) BRCA2 nonsense mutation, HR was restored in the resistant cells. Immunoprecipitation followed by immunoblotting or mass spectrometry demonstrated expression of low levels of BRCA2 protein, including peptides distal to the premature termination codon. Reporter assays demonstrated readthrough selective for the UAG stop codon in the veliparib-resistant clones but not parental PEO1 cells; and mass spectrometry revealed insertion of tyrosine rather than termination in the readthrough product. Mass spectrometry and immunoblotting provided evidence for readthrough of UAGs in additional proteins in the resistant clones. BRCA2 gene interruption 3’ to the stop codon restored sensitivity of the resistant clones to PARP inhibitors and cisplatin, implicating the low level BRCA2 expression in resistance. Accordingly, the present results identify low level readthrough of nonsense codons as a potential mechanism of drug resistance that might need to be considered when assessing the impact of mutations on the biology of cancers.
2025-10-27 | PXD037989 | Pride
Project description:Pancreatic ductal adenocarcinoma (PDAC) is a challenging malignancy to treat, but emerging evidence suggests that specific subtypes may respond more favorably to certain therapies. BRCA-mutated PDAC represents a distinct subtype that is particularly sensitive to DNA-damaging therapies. The current standard of care for advanced BRCA-mutated PDAC involves induction platinum-based chemotherapy followed by maintenance therapy with a poly (ADP-ribose) polymerase inhibitor (PARPi). However, the randomized phase III POLO trial, upon which this standard is based, did not demonstrate an improved overall survival in patients who received olaparib compared to those who received placebo, highlighting the need for new therapeutic approaches. Additionally, there is a lack of robust models that recapitulate the tumor microenvironment of BRCA mutated PDAC, limiting the development of next-generation maintenance treatment options. In this study, we developed a syngeneic and immunocompetent mouse model of Brca2-mutated PDAC. The model demonstrated high sensitivity to cisplatin plus gemcitabine, but limited efficacy of PARPi monotherapy. Induction with platinum-based chemotherapy sensitized tumors to PARPi maintenance therapy and promoted an exhausted, T cell-inflamed tumor microenvironment. However, resistance emerged which was associated with CDX2 expression and tumor differentiation. The addition of anti-PD1 treatment to PARPi maintenance enhanced tumor regression and prolonged overall survival. These findings provide preclinical support for ongoing clinical trials investigating immunotherapy with PARPi as a maintenance strategy in homologous recombination-deficient PDAC.
2025-09-30 | GSE300888 | GEO
Project description:Pancreatic ductal adenocarcinoma (PDAC) is a challenging malignancy to treat, but emerging evidence suggests that specific subtypes may respond more favorably to certain therapies. BRCA-mutated PDAC represents a distinct subtype that is particularly sensitive to DNA-damaging therapies. The current standard of care for advanced BRCA-mutated PDAC involves induction platinum-based chemotherapy followed by maintenance therapy with a poly (ADP-ribose) polymerase inhibitor (PARPi). However, the randomized phase III POLO trial, upon which this standard is based, did not demonstrate an improved overall survival in patients who received olaparib compared to those who received placebo, highlighting the need for new therapeutic approaches. Additionally, there is a lack of robust models that recapitulate the tumor microenvironment of BRCA mutated PDAC, limiting the development of next-generation maintenance treatment options. In this study, we developed a syngeneic and immunocompetent mouse model of Brca2-mutated PDAC. The model demonstrated high sensitivity to cisplatin plus gemcitabine, but limited efficacy of PARPi monotherapy. Induction with platinum-based chemotherapy sensitized tumors to PARPi maintenance therapy and promoted an exhausted, T cell-inflamed tumor microenvironment. However, resistance emerged which was associated with CDX2 expression and tumor differentiation. The addition of anti-PD1 treatment to PARPi maintenance enhanced tumor regression and prolonged overall survival. These findings provide preclinical support for ongoing clinical trials investigating immunotherapy with PARPi as a maintenance strategy in homologous recombination-deficient PDAC.
2025-09-30 | GSE300887 | GEO
Project description:Germline BRCA-associated pancreatic ductal adenocarcinoma(glBRCA-PDAC) tumors aresusceptible to platinum/PARP-inhibition. The clinical outcomesof 125 glBRCA-PDAC patients was stratified based on the spectrum of response to platinum/PARP-inhibition: i)Refractory(OS<6 months) ii)Durable response followed by acquired-resistance(OS<36 months); iii)Long-term responders(OS>36 months). Patient-derived-xenografts(PDX) were generated from 25 glBRCA-PDAC patients at different clinical time-points. Response to platinum/PARP-inhibition in-vivo and ex-vivo culture(EVOC) correlated with clinical response. We deciphered the mechanisms of resistance in glBRCA-PDAC and identified homologous recombination(HR)-proficiency and secondary-mutations restoring partial functionality as the most dominant resistant mechanism. Yet, a subset of HR-deficient(HRD) patients demonstrated clinical resistance. Their tumors displayed basal-like molecular subtype and were more aneuploid. Tumor-mutational-burden(TMB) was high in HRD-PDAC and significantly higher in tumors with secondary mutations. Anti-PD1 attenuated tumor growth in a novel humanized glBRCA-PDAC PDX-model. This work demonstrates the utility ofpreclinicalmodels, including EVOC, to predict response of glBRCA-PDAC to treatment, whichhas potential to inform time-sensitive medical decisions.
2023-07-13 | GSE235843 | GEO
Project description:Mutations in the tumour suppressor BRCA2 are associated with predisposition to breast and ovarian cancers. BRCA2 has a central role in genome integrity by facilitating the repair of toxic DNA double-strand breaks (DSBs) by homologous recombination. BRCA2 acts by promoting RAD51 nucleofilament formation on resected single-stranded DNA, but how BRCA2 activity is regulated during HR is not fully understood. Here, we delineate a pathway where ATM and ATR kinases phosphorylate a highly conserved region in BRCA2 in response to DNA DSBs. These phosphorylations stimulate the binding of the protein phosphatase PP2A-B56 to BRCA2 through a conserved binding motif. We show that the phosphorylation-dependent formation of the BRCA2-PP2A-B56 complex is required for efficient RAD51 loading to sites of DNA damage and HR-mediated DNA repair. Moreover, we find that several cancer-associated mutations in BRCA2 deregulate the BRCA2-PP2A-B56 interaction and sensitize cells to PARP inhibition. Collectively, our work uncovers PP2A-B56 as a positive regulator of BRCA2 function in HR with clinical implications for BRCA2 and PP2A-B56 mutated cancers.
2021-07-26 | MSV000087884 | MassIVE