Export of Actively Signaling HER2 and EGFR Heterodimers Within Extracellular Vesicles in Breast Cancer: New Diagnostic and Therapeutic Strategies

Abstract

Breast cancer is among the leading causes of cancer-related death worldwide. The epidermal growth factor receptor (EGFR) family, particularly EGFR and HER2, plays a central role in regulating cell proliferation, survival, and progression in breast cancer. Extracellular vesicles (EVs) are small membrane-bound particles released by cells that contain molecular information about the active state of the cells. HER2-targeted therapies have significantly improved outcomes for many patients, and we hypothesize that tumor cells traffic the activated HER2 and EGFR into EVs that are exported outside the cell. This study investigates EV cell signaling using two human breast cancer cell lines, MDA-MB-231 and MDA-MB-361, which express higher levels of HER2 and provide a clinically relevant model. Cells were cultured with exosome-free media and treated with epidermal growth factor (EGF) at varying concentrations to activate EGFR/HER2 signaling. Following collection of EVs, western blot analysis of phosphorylated EGFR (Y1068), phosphorylated HER2 (Y877), total receptor expression, and EV associated markers was conducted. Comparing EVs with matched cell lysates across HER2-expressing breast cancer cell lines aims to further characterize receptor internalization, EV trafficking, and the ability of EVs to reflect ongoing intracellular HER family signaling. Additional studies will incorporate the dynamin inhibitor dynasore to block endocytosis and determine how blocking receptor internalization alters EV-associated EGFR and HER2 signaling. These findings support the development of EV-based biomarkers collected from the tumor microenvironment to monitor tumor signaling and improve personalized treatment strategies for breast cancer.