Altered Estrogen Receptor Signaling Pathway in BRCA2-Deficient Estrogen Receptor-Positive/HER2-Negative Breast...

Area of Science:

• Oncology
• Genetics
• Molecular Biology

Background:

• Hereditary breast cancer, often linked to BRCA2 pathogenic variants (PVs), typically presents as estrogen receptor (ER)-positive/HER2-negative.
• BRCA2 PVs are associated with aggressive breast cancer phenotypes, but their precise impact on ER signaling is not well understood.

Purpose of the Study:

• To investigate the relationship between BRCA2 deficiency and ER signaling in ER-positive/HER2-negative breast cancer.
• To integrate clinical data with in vitro experimental findings.

Main Methods:

• Immunohistochemical analysis of ER-positive/HER2-negative breast tumors from BRCA2 PV carriers and wild-type patients.
• Generation of BRCA2-deficient MCF7 cell lines using CRISPR-Cas9.
• Western blotting and functional assays to assess ER signaling pathway alterations.

Main Results:

• BRCA2 PV carriers showed significantly lower levels of phosphorylated ER Ser167, AKT Ser473, and RB1 compared to wild-type patients.
• BRCA2-deficient cells exhibited reduced phosphorylation of ER and AKT, without consistent changes in downstream gene/protein expression.
• BRCA2 deficiency enhanced sensitivity to olaparib but not tamoxifen.

Conclusions:

• This study provides the first detailed characterization of ER signaling alterations in ER-positive/HER2-negative breast cancers with germline BRCA2 PVs.
• Findings offer insights into potential targeted therapeutic strategies for this specific patient group.