MUC1 is a large cell surface mucin glycoprotein that plays diverse roles in both normal and tumor cell biology. These roles include mucosal hydration and protection, inhibition of embryo implantation, protection of tumor cells from the immune system and reduction of cytotoxic drug uptake. Similarly, the EGFR family of cell surface receptors drives many normal developmental processes as well as various aspects of tumor growth and gene expression. EGFR family members have been demonstrated to form complexes with MUC1 in various cellular contexts. Nonetheless, the role that EGFR activation plays in modulating MUC1 levels has not been considered. In this study, we demonstrate that activated EGFR drives high level MUC1 expression in multiple cell lines of uterine adenocarcinoma and pancreatic cancer origins. In some cells, addition of exogenous EGFR ligands (EGF or HB-EGF) elevates MUC1 levels while addition of the EGFR tyrosine kinase inhibitor, AG1478, reduces MUC1 levels. The thiazolidinedione, rosiglitazone, previously shown to reduce progesterone-stimulated MUC1 expression, also blocks EGFR ligand-driven MUC1 expression. This activity was observed at relatively high rosiglitazone concentrations (above 10 µM) and appeared to be largely PPARγ independent indicating a novel utility of this drug to reduce mucin-expression in various tumor settings. Collectively, these data demonstrate that: (1) activation of EGFR stimulates MUC1 expression in multiple cellular contexts and (2) it may be possible to develop useful interventions to reduce MUC1 expression as a complementary strategy for tumor therapy. J. Cell. Biochem. 114: 2314–2322, 2013. © 2013 Wiley Periodicals, Inc.
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