YAP expression in normal and neoplastic breast tissue: an immunohistochemical study

Area of Science:

• Oncology
• Molecular Biology
• Cell Biology

Background:

• Yes-associated protein (YAP) is a transcriptional regulator implicated in cell proliferation, apoptosis, and carcinogenesis.
• The precise role of YAP in breast cancer (BC) remains controversial.
• This study investigates YAP expression across different breast tissue types and BC subtypes.

Purpose of the Study:

• To compare YAP expression in normal breast tissue, non-neoplastic breast tissue from cancer patients, and four subtypes of invasive ductal carcinoma.
• To elucidate the potential role of YAP as a tumor suppressor or oncogene in BC.

Main Methods:

• Immunohistochemistry (IHC) was used to detect YAP expression.
• 17 normal breast tissue samples (controls) and 105 invasive ductal carcinoma cases were analyzed.
• Tumor cases included Luminal A, Luminal B, HER2-overexpressing, and triple-negative subtypes.

Main Results:

• YAP expression was significantly lower in tumor cells compared to normal breast tissue.
• Normal breast tissue showed 100% YAP expression in myoepithelial cells, while internal controls had 40%.
• Nuclear YAP expression varied significantly among BC subtypes, with Luminal A showing the lowest positive case percentage and Luminal B having the highest nuclear expression (20%).

Conclusions:

• YAP expression is decreased in breast cancer cells relative to normal tissue.
• These findings support a role for YAP as a tumor suppressor gene in breast cancer.
• Differential YAP expression exists across various ductal breast cancer subtypes.