Molecular Characterization of BRCA1 c.5339T>C Missense Mutation in DNA Damage Response of Triple-Negative Breast Cancer

Abstract

BRCA1 L1780P BRCT domain mutation has been recognized as a pathogenic mutation in patients with breast cancer. However, the molecular significance of this mutation has not yet been studied in triple-negative breast cancer (TNBC) cells in vitro. We established MDA-MB 231, HCC1937, and HCC1395 TNBC cell lines expressing BRCA1 L1780P mutant. BRCA1 L1780P mutant TNBC cells showed increased migration and invasion capacity, as well as increased sensitivity to olaparib and carboplatin compared to BRCA1 wild-type cells. BRCA1 L1780P mutant TNBC cells showed decreased RAD51 expression and reduced nuclear RAD51 foci formation following carboplatin and olaparib treatment. The molecular interaction between p-ATM and BRCA1 was abrogated following introduction of BRCA1 L1780P mutant plasmid in TNBC cells, suggesting that the BRCA1 L1780P mutation disrupts the p-ATM-BRCA1 protein–protein interaction. We established an olaparib-resistant BRCA1 L1780P mutant TNBC cell line by chronic drug treatment. Olaparib-resistant cell lines showed upregulation of RAD51 expression upon olaparib treatment, and reduction in RAD51 expression in olaparib-resistant cells restored olaparib sensitivity. Collectively, these results suggest that the BRCA1 L1780P mutation impairs RAD51 recruitment by disrupting p-ATM-BRCA1 interaction, which is a crucial molecular factor in homologous recombination and olaparib sensitivity. Further therapeutic targeting of RAD51 in BRCA1 L1780P mutant breast cancer is warranted.

BRCA1 and Its Vulnerable C-Terminal BRCT Domain: Structure, Function, Genetic Mutations and Links to Diagnosis and Treatment of Breast and Ovarian Cancer

“…The BRCA1–Abraxas complex plays a crucial role in recruiting BRCA1 to double-stranded DNA breaks, regulating DNA damage, and promoting efficient repair. The numerous cancer-associated BRCT mutations identified in patients alter their ability to bind phosphorylated peptides, highlighting the critical role of BRCT domains in maintaining genome integrity and facilitating essential protein–protein interactions for DNA repair and genomic stability maintenance [ 21 ].…”

“…Breast cancer is classified into luminal A, luminal B, HER2 overexpression, and triple-negative breast cancer (TNBC), each of which is characterized by different histological and pathological features [ 21 ]. In TNBC, which accounts for 15% of all invasive cases, expression of the estrogen and progesterone receptors as well as HER2 is absent.…”

“…TNBC development involves many pathways, with the current focus being DNA repair, particularly the BRCA1 and BRCA2 functions. BRCA1 mutations common in RING, BRCT domains, and the middle region increase the risk of various cancers [ 21 ].…”