Genetic Evolution in BRCA1-Associated Breast Cancer Reveals Early Driver Mutations Shaping Tumor Features and
Li Hu1, Zhongwu Li2, Qiting Wan1
1Familial & Hereditary Cancer Center, Key Laboratory of Carcinogenesis and Translational Research, Ministry of Education, Peking University Cancer Hospital & Institute, Beijing, P. R. China.
Cancer Science
|July 3, 2026
Summary
Pathogenic BRCA1 variants increase breast cancer risk. This study reveals TP53 mutations define an aggressive subtype in BRCA1 carriers, distinct from non-carriers, with implications for treatment.
Area of Science:
- Genetics
- Oncology
- Genomic Medicine
Background:
- Germline pathogenic variants in the BRCA1 gene are linked to increased breast cancer risk, particularly early-onset and triple-negative disease.
- The precise sequence of genetic alterations driving tumor development in BRCA1 carriers is not fully understood.
Purpose of the Study:
- To elucidate the distinct mutational landscape and evolutionary genetic events in breast tumors from BRCA1 carriers.
- To classify BRCA1-associated breast cancers based on initiating driver events and assess their clinical and molecular characteristics.
Main Methods:
- Analysis of 57 primary breast tumors from BRCA1 carriers using deep target-region sequencing, whole-exome sequencing, and bulk transcriptome sequencing.
- Comparative analysis of mutational profiles against The Cancer Genome Atlas (TCGA) non-carrier data.
- Classification of tumors into TP53-driven, PI(3)K-AKT pathway-driven, and unclassified subgroups.
Main Results:
- BRCA1-associated breast cancers exhibit a unique mutational profile with frequent TP53 alterations and infrequent PIK3CA/GATA3 changes compared to non-carriers.
- The TP53-driven subgroup is strongly linked to the triple-negative phenotype, BRCA1 loss of heterozygosity, and heightened genomic instability.
- TP53 truncating mutations were more common in BRCA1 carriers, associated with poorer outcomes, potentially due to reduced homologous recombination deficiency (HRD) and activated epithelial-mesenchymal transition (EMT) pathways.
Conclusions:
- Breast cancers in BRCA1 carriers possess a distinct genetic architecture.
- TP53 truncating mutations may identify a particularly aggressive subtype of BRCA1-associated breast cancer.
- Further research into TP53 mutations in BRCA1 carriers is warranted for potential therapeutic strategies.
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