Functional Effect of an Amphiregulin Autocrine Loop on Inflammatory Breast Cancer Progression; Annual summary rept. 1 Mar 2007-28 Feb 2008

摘要

We have previously shown that an AR/EGFR autocrine loop is required for SUM149 human breast cancer cell proliferation, motility and invasion. In the present studies, we demonstrate that SUM149 cells and human mammary epithelial MCF10A cells that over express AR (MCF10A AR) or are cultured in the presence of exogenous AR, express higher levels of EGFR protein compared with MCF10A cells cultured in EGF. We show that EGFR protein remains stable in the presence of AR yet is degraded in the presence of EGF. Consistent with this observation, tyrosine 1045 on the EGFR, the c-cbl binding site, exhibited decreased phosphorylation in the presence of AR compared with EGF. Ubiquitination of EGFR was also dramatically decreased when AR was the ligand. Following AR binding, EGFR remained on the cell surface instead of being rapidly internalized as observed when EGF was present. Immunofluorescence demonstrated that MCF10A cells cultured in EGF exhibited a predominantly intracellular, punctate localization of EGFR. In stark contrast, SUM149 cells and MCF10A cells growing in the presence of AR expressed EGFR predominantly on the membrane and at cell-cell junctions. Therefore, AR alters EGFR internalization and degradation in a way that favors accumulation of EGFR at the cell surface and ultimately leads to changes in EGFR signaling. In addition, we found that AR, but not EGF upregulates NFkB activity and IL-1 production suggesting that AR may play a unique role in breast cancer progression.