Submitted on August 14, 2008
Revised on January 31, 2009
Accepted on February 23, 2009
Soluble HB-EGF Induces Epithelial-to-Mesenchymal Transition in Inner Medullary Collecting Duct Cells by Upregulating Snail-2
James P. Smith1, Ambra Pozzi1, Punita Dhawan2, Amar B. Singh1, and Raymond C Harris1*
1 Vanderbilt University
2 Vanderbilt University Medical Center
* To whom correspondence should be addressed. E-mail: raymond.harris{at}Vanderbilt.Edu.
Animal models of acute renal injury suggest that the epidermal growth factor receptor (EGFR) axis may have a beneficial role in the recovery from acute renal injury, but recent reports describe detrimental effects of EGFR activation in chronic renal injury. Expression of the EGFR ligand, heparin-binding EGF-like growth factor (HB-EGF), increases following renal injury, but the effects of this sustained upregulation have not been well studied. Here, stable overexpression of soluble HB-EGF (sHB-EGF) in mouse inner medullary collecting duct (IMCD) cells led to marked phenotypic changes: sHB-EGF-expressing cells demonstrated a fibroblast-like morphology, did not form epithelial sheets, exhibited cytoplasmic projections, decreased expression of epithelial markers and increased expression of fibroblast specific protein-1. They also demonstrated anchorage-independent growth and formed tumors when injected subcutaneously into nude mice. Quantitative RT-PCR and a luciferase reporter assay suggested that sHB-EGF repressed transcription of E-cadherin, and concomitant TGF-
-independent upregulation of the E-cadherin repressor Snail-2 was observed. Stable downregulation of Snail-2 in sHB-EGF-overexpressing cells restored epithelial characteristics (E-cadherin and cytokeratin expression), but did not alter their anchorage-independent growth. In summary, sustained exposure to sHB-EGF induces epithelial-to-mesenchymal transition of IMCD cells, in part by upregulating the E-cadherin transcriptional repressor Snail-2.
