Protocol to Establish Estrogen Receptor-Negative Heterozygous BRCA1 Organoids.

Area of Science:

• Oncology
• Genetics
• Cell Biology

Background:

• BRCA1 carriers often develop triple-negative breast cancer (TNBC), a complex cancer type.
• The exact mechanisms driving cancer in BRCA1 carriers are not fully understood.
• A lack of suitable cell models hinders research into TNBC development in BRCA1 mutation carriers.

Purpose of the Study:

• To establish a novel human organoid model for studying cancer development in BRCA1 carriers.
• To characterize estrogen receptor (ER)-, progesterone receptor (PR)-, and HER2-negative breast progenitor cells with BRCA1 mutations.
• To provide a platform for in-depth investigation of early cancer initiation steps in BRCA1-associated TNBC.

Main Methods:

• Generation of human ER/PR/HER2-negative breast organoids carrying a BRCA1 germline mutation.
• Confirmation of organoid characteristics, including estrogen unresponsiveness, self-renewal capacity, and stem/progenitor marker (CD44) expression.
• Assessment of organoid morphology for resemblance to mammary gland structures.

Main Results:

• Successfully generated human ER/PR/HER2-negative breast organoids with a BRCA1 germline mutation.
• Confirmed these organoids exhibit key stem/progenitor cell properties and are unresponsive to estrogen.
• Observed organoid outgrowths mimicking mature ductal and lobular units of the mammary gland.

Conclusions:

• The developed organoid model is a valuable tool for studying cancer initiation in ER/PR/HER2-negative cells with BRCA1 mutations.
• This model system facilitates a deeper understanding of the multi-step process leading to TNBC in BRCA1 carriers.
• Further research using this model can elucidate critical factors and mechanisms in BRCA1-associated breast cancer development.