Trastuzumab as a Preoperative Monotherapy Does Not Inhibit HER2 Downstream Signaling in HER2-Positive Breast Cancer

A recent study showed that trastuzumab inhibits the MAPK and PI3K pathways for cell lines overexpressing HER2, but not on HER2-overexpressing tumors that have received preoperative treatment as a monotherapy. According to the results, the inhibition of oncogenic signaling pathways may not be the main mode of action employed, when trastuzumab is administered alone in chemotherapy-naïve patients. Alternative molecular mechanisms, such as the modulation of immune pathways, should be considered.

 Oncology Letters