Related Experiment Video
Updated: Jul 29, 2025
Identifying the Effects of BRCA1 Mutations on Homologous Recombination using Cells that Express Endogenous Wild-type BRCA1
Published on: February 17, 2011
Multi-omics analysis reveals distinct non-reversion mechanisms of PARPi resistance in BRCA1- versus BRCA2-deficient
Jinhyuk Bhin1, Mariana Paes Dias2, Ewa Gogola2
1Division of Molecular Pathology, Oncode Institute, the Netherlands Cancer Institute, 1066CX Amsterdam, the Netherlands; Division of Molecular Carcinogenesis, Oncode Institute, the Netherlands Cancer Institute, 1066CX Amsterdam, the Netherlands; Department of Biomedical System Informatics, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul 03722, Republic of Korea.
Abstract:
BRCA1 and BRCA2 both function in DNA double-strand break repair by homologous recombination (HR). Due to their HR defect, BRCA1/2-deficient cancers are sensitive to poly(ADP-ribose) polymerase inhibitors (PARPis), but they eventually acquire resistance. Preclinical studies yielded several PARPi resistance mechanisms that do not involve BRCA1/2 reactivation, but their relevance in the clinic remains elusive. To investigate which BRCA1/2-independent mechanisms drive spontaneous resistance in vivo, we combine molecular profiling with functional analysis of HR of matched PARPi-naive and PARPi-resistant mouse mammary tumors harboring large intragenic deletions that prevent reactivation of BRCA1/2. We observe restoration of HR in 62% of PARPi-resistant BRCA1-deficient tumors but none in the PARPi-resistant BRCA2-deficient tumors. Moreover, we find that 53BP1 loss is the prevalent resistance mechanism in HR-proficient BRCA1-deficient tumors, whereas resistance in BRCA2-deficient tumors is mainly induced by PARG loss. Furthermore, combined multi-omics analysis identifies additional genes and pathways potentially involved in modulating PARPi response.
Insights
Tumors resistant to PARP inhibitors (PARPis) can develop without reactivating BRCA1/2. In BRCA1-deficient tumors, 53BP1 loss restores DNA repair, while PARG loss drives resistance in BRCA2-deficient tumors.
Area of Science:
- Oncology
- Genetics
- Molecular Biology
Background:
- BRCA1 and BRCA2 proteins are crucial for DNA double-strand break repair via homologous recombination (HR).
- BRCA1/2-deficient cancers exhibit sensitivity to poly(ADP-ribose) polymerase inhibitors (PARPis) but often develop resistance.
- Preclinical models suggest PARPi resistance mechanisms independent of BRCA1/2 reactivation, but their clinical significance is unclear.
Purpose of the Study:
- To investigate BRCA1/2-independent mechanisms driving spontaneous PARPi resistance in vivo.
- To correlate molecular profiles with HR functional status in PARPi-naive and resistant tumors.
- To identify specific genetic alterations conferring PARPi resistance in mouse models.
Main Methods:
- Utilized matched PARPi-naive and PARPi-resistant mouse mammary tumors with intragenic deletions precluding BRCA1/2 reactivation.
- Combined molecular profiling (multi-omics) with functional analysis of homologous recombination (HR).
- Assessed HR proficiency and identified specific gene losses (e.g., 53BP1, PARG) associated with resistance.
Main Results:
- Homologous recombination (HR) was restored in 62% of PARPi-resistant BRCA1-deficient tumors, but not in BRCA2-deficient counterparts.
- Loss of 53BP1 was identified as the predominant resistance mechanism in HR-proficient BRCA1-deficient tumors.
- Loss of PARG was the primary driver of resistance in BRCA2-deficient tumors.
- Multi-omics analysis revealed additional candidate genes and pathways influencing PARPi response.
Conclusions:
- PARPi resistance in BRCA1/2-deficient cancers can arise from BRCA1/2-independent mechanisms.
- 53BP1 loss in BRCA1-deficient and PARG loss in BRCA2-deficient tumors are key drivers of acquired resistance.
- Further investigation into identified genes and pathways may uncover novel therapeutic strategies for overcoming PARPi resistance.
More Related Videos
08:15gDNA Enrichment by a Transposase-based Technology for NGS Analysis of the Whole Sequence of BRCA1, BRCA2, and 9 Genes Involved in DNA Damage Repair
Published on: October 6, 2014
11:47Time-lapse Imaging of Primary Preneoplastic Mammary Epithelial Cells Derived from Genetically Engineered Mouse Models of Breast Cancer
Published on: February 8, 2013