Abstract 2517: The role of endocytic traffic regulator EHD1 in EGFR traffic and breast cancer

Abstract

Abstract Epidermal growth factor receptor (EGFR) is a prototype receptor tyrosine kinase and serves as an oncogene in a variety of solid tumors. Its surface expression is dynamically regulated, and display of an activation-competent cell surface pool is an essential pre-requisite for cellular responses to EGF and other ligands, as well as for its oncogenic function. While mechanisms that regulate the post-activation endocytic fate of EGFR have received much attention, little is known about the mechanisms that control the basal, pre-activation, surface display of EGFR. Here, we identify a novel role of the endocytic recycling regulator EHD1 in the cell surface display of EGFR and EGF-driven functional responses. We demonstrate that inducible knockdown of EHD1 in human mammary epithelial cells impairs the EGFR delivery to the cell surface, resulting in reduced EGFR cell surface expression and accumulation in the Golgi, a phenotype rescued by exogenous EHD1. Reduced surface display of EGFR by depletion of EHD1 impaired EGF-induced proliferation mammary epithelial cells and a breast cancer cell line, demonstrating that the new molecular pathway we describe is functionally important. Given the role of EGFR and its family members in breast cancer, we carried out IHC screening of EHD1 expression in human breast cancer using tissue microarrays from a large (>800 samples) and well-annotated breast cancer cohort. Of the 757 evaluable samples, EHD1 was overexpressed in 115 (15%) patients. Notably, a substantially higher percentage of HER2/ErbB2+ patients (25%) showed EHD1 overexpression. Survival analysis revealed that EHD1 overexpression was associated with a significantly shorter overall survival over 15 years of follow up. These studies reveal novel roles of EHD1 in regulating EGFR traffic and suggest its potential roles in regulating other EGFR family members, especially HER2/ErbB2. Our patient sample analyses support a role for EHD1 overexpression in promoting breast tumorigenesis. Future studies will be directed at directly testing the role of EHD1, and its family members, in HER2 traffic and the role of EHD1 in breast tumorigenesis. As EHD proteins possess ATPase activity, which is required for their function, our studies raise the prospect of developing inhibitors of these enzymes as potential anti-cancer agents. Citation Format: Insha Mushtaq, Eric C. Tom, Priyanka Arya, Timothy Bielecki, Bhopal Mohapatra, Sameer Mirza, Matthew D. Storck, Dena Ahmad, Rokaya El Ansari, Emad Rakha, Vimla Band, Hamid Band. The role of endocytic traffic regulator EHD1 in EGFR traffic and breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2517.