Gastroenterology

Gastroenterology

Volume 143, Issue 3, September 2012, Pages 730-740
Gastroenterology

Original Research
Basic and Translational—Alimentary Tract
A Role for the Epidermal Growth Factor Receptor Signaling in Development of Intestinal Serrated Polyps in Mice and Humans

https://doi.org/10.1053/j.gastro.2012.05.034Get rights and content

Background & Aims

Epithelial cancers can be initiated by activating mutations in components of the mitogen-activated protein kinase signaling pathway such as v-raf murine sarcoma viral oncogene homolog B1 (BRAF), v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS), or epidermal growth factor receptor (EGFR). Human intestinal serrated polyps are a heterogeneous group of benign lesions, but some progress to colorectal cancer. Tumors that arise from these polyps frequently contain activating mutations in BRAF or KRAS, but little is known about the role of EGFR activation in their development.

Methods

Polyp samples were obtained from adults during screening colonoscopies at Mount Sinai Hospital in New York. We measured levels of EGFR protein and phosphorylation in human serrated polyps by immunohistochemical and immunoblot analyses. We generated transgenic mice that express the ligand for EGFR, Heparin-binding EGF-like growth factor (HB-EGF), in the intestine.

Results

EGFR and the extracellular-regulated kinases (ERK)1/2 were phosphorylated in serrated areas of human hyperplastic polyps (HPPs), sessile serrated adenomas, and traditional serrated adenomas. EGFR and ERK1/2 were phosphorylated in the absence of KRAS or BRAF activating mutations in a subset of HPP. Transgenic expression of the EGFR ligand HB-EGF in the intestines of mice promoted development of small cecal serrated polyps. Mice that expressed a combination of HB-EGF and US28 (a constitutively active, G-protein–coupled receptor that increases processing of HB-EGF from the membrane) rapidly developed large cecal serrated polyps. These polyps were similar to HPPs and had increased phosphorylation of EGFR and ERK1/2 within the serrated epithelium. Administration of pharmacologic inhibitors of EGFR or MAPK to these transgenic mice significantly reduced polyp development.

Conclusions

Activation of EGFR signaling in the intestine of mice promotes development of serrated polyps. EGFR signaling also is activated in human HPPs, sessile serrated adenomas, and traditional serrated adenomas.

Section snippets

Mice

VS28 mice were described by Bongers et al.16 To generate the HBGF mice, we cloned sequences encoding simian HB-EGF fused to green fluorescent protein (GFP)17 into a vector containing the mouse villin promoter.18 The plasmid was verified by sequencing, and the transgene free of vector sequences was microinjected into C57BL/6J mouse eggs (The Jackson Laboratory, Bar Harbor, ME). The resulting founders and their progeny (HBGF mice) were genotyped by polymerase chain reaction (PCR) amplification of

EGFR Signaling in Human Serrated Polyps

To investigate EGFR signaling in serrated polyps, we examined the phosphorylation of EGFR in tissue sections of 27 HPP, 25 SSA/P, 22 TSA, and 14 normal controls using an antibody that specifically recognizes the autophosphorylated Y1173 residue of EGFR. We found P-EGFR/Y1173-positive staining in 70% of the HPP, 48% of the SSA/P, and 91% of the TSA cases examined. P-EGFR/Y1173 staining was found in less than 1% of the epithelial cells of normal controls. In marked contrast, a significant

Discussion

In this report, we provide evidence that activation of EGFR signaling is important for the development of intestinal serrated polyps. We show that EGFR is selectively activated (phosphorylated) in human and murine polyps, and that expression of the EGFR ligand HB-EGF in intestinal epithelial cells of transgenic mice leads to the development of serrated polyps that are remarkably similar to those found in humans. We report that increased EGFR signaling promotes the formation of intestinal

Acknowledgments

The authors would like to thank N. Mall for the preparation of histologic sections, and M. Wijtmans, T. Sparwasser, and S. Jung for reagents.

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    Conflicts of interest The authors disclose no conflicts.

    Funding Supported by a grant from Jenny & Jon Steingart and Jenna & Paul Segal (G.B.); also supported by National Institutes of Health grants 1R01CA161373-01 (S.A.L.) and P01 DK072201 (to S.A.L. and L.M.).

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