Chasing Hippos: Implications of YAP1 and TAZ Expression in Pregnancy-associated Breast Cancer Tumorigenesis

Background/Aim: The Hippo pathway is a molecular pathway recently associated with tumorigenesis, metastasis, and drug resistance. Pregnancy-associated breast cancer (PABC) is the most common malignancy diagnosed during gestation; however, the molecular mechanisms underlying PABC are largely unknown. The aim of the present study was to evaluate Hippo pathway transducers TAZ and YAP1 expression in PABC in relation to the clinicopathological characteristics of the disease. Patients and Methods: Formalinfixed paraffin-embedded (FFPE) tissues from 21 PABC patients treated at Alexandra Hospital in Athens, Greece, were analyzed with immunohistochemistry. Results: Strong nuclear TAZ/YAP1 stanning was found in 48% of the PABC patients analyzed. Hormone receptor negative patients had a statistically significant correlation with strong positive expression of TAZ/YAP1 co-transcription factors. No association was observed with overall and disease-free survival. Conclusion: The Hippo pathway is de-regulated in a subset of PABC patients, highlighting the complex molecular background of the disease, which certainly requires further investigation.