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Updated: Aug 15, 2026
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Identifying the Effects of BRCA1 Mutations on Homologous Recombination using Cells that Express Endogenous Wild-type BRCA1
Published on: February 17, 2011
Germline BRCA1 pathogenic variants and T cell dysfunction
J Kay1,2, M A Harris1,2, L E Lara Gonzalez1,2
1Department of Research, The Peter MacCallum Cancer Centre, Melbourne, Australia.
Immuno-Oncology Technology
|August 14, 2026
Summary
Germline BRCA1 variants impair T cell function and reduce T cell counts in breast cancer patients. This T cell dysfunction may impact immunity, cancer development, and immunotherapy response.
Area of Science:
- Immunology
- Oncology
- Genetics
Background:
- Germline BRCA1 (gBRCA1) pathogenic variants (PVs) are a leading cause of inherited breast cancer.
- Previous research indicated homozygous BRCA1 loss impairs T cell-mediated anti-tumor immunity.
- The effect of heterozygous gBRCA1 on human T cell function remained unknown.
Purpose of the Study:
- To investigate the functional consequences of gBRCA1 PVs on human T cells.
- To analyze T cell phenotypes and functions in breast cancer patients with and without gBRCA1 PVs.
- To assess the impact of gBRCA1 PVs on tumor-infiltrating lymphocytes (TILs) in triple-negative breast cancer (TNBC).
Main Methods:
- Collected peripheral blood mononuclear cells (PBMCs) from healthy donors and treatment-naïve early-stage breast cancer patients.
- Activated T cells in vitro and analyzed phenotypic and functional differences.
- Performed T cell receptor (TCR) sequencing and whole exome sequencing on TNBC tumors from gBRCA1 carriers and wild-type (WT) patients.
Main Results:
- Patients with gBRCA1 PVs had significantly lower circulating T cell counts than WT individuals.
- Activated T cells from gBRCA1 carriers showed reduced BRCA1 protein expression, impaired proliferation, and decreased effector molecule production.
- TCR sequencing of TILs from TNBC tumors revealed more hyperexpanded T cell clones in gBRCA1 carriers, correlating with increased tumor mutation burden.
Conclusions:
- Circulating T cells from gBRCA1 carriers exhibit intrinsic dysfunction.
- This T cell dysfunction may influence anti-tumor immunity, cancer development, and progression.
- The findings suggest potential clinical relevance for immunotherapy treatment strategies in gBRCA1 carriers.
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