TNF-α induces upregulation of EGFR expression and signaling in human colonic myofibroblasts

Abstract

The myofibroblast has recently been identified as an important mediator of tumor necrosis factor-α (TNF-α)-associated colitis and cancer, but the mechanism(s) involved remains incompletely understood. Recent evidence suggests that TNF-α is a central regulator of multiple inflammatory signaling cascades. One important target of TNF-α may be the signaling pathway downstream of the epidermal growth factor receptor (EGFR), which has been associated with many human cancers. Here, we show that long-term exposure of 18Co cells, a model of human colonic myofibroblasts, with TNF-α led to a striking increase in cell surface EGFR expression, an effect that was completely inhibited by cycloheximide. Subsequent EGFR binding by EGF and heparin binding (HB)-EGF was associated with enhanced EGFR tyrosine kinase activity, prolonged ERK activation, and a significant increase in cyclooxygenase-2 (COX-2) expression compared with 18Co cells treated with EGF and HB-EGF alone. TNF-α also increased EGFR expression and signaling in primary myofibroblasts isolated from human colon tissue. TNF-α-induced upregulation of EGFR may be a plausible mechanism to explain the exaggerated cellular responsiveness that characterizes inflammatory bowel disease and that may contribute to a microenvironment that predisposes to colitis-associated cancer through enhanced COX-2 expression.

Epidermal growth factor receptor inhibits colitis-associated cancer in mice

“…Although the major site of EGFR expression in the colon is the epithelium, several lamina propria cell types also express EGFR, including myofibroblasts and monocytic lineages (i.e., macrophages and dendritic cells) (19)(20)(21). While the functional role for EGFR in these cells is relatively unknown, each cell type is involved in both inflammation and tumor biology, suggesting that EGFR regulation of these cells may contribute to protection from colitis and CAC.…”

“…Within the colon, EGFR is expressed mainly on the basolateral aspect of all epithelial cells and, to a lesser extent, in subepithelial myofibroblasts and monocytic cells (19)(20)(21); however, the functional significance for EGFR in these latter two cell populations is unclear either in the normal or inflamed colon. Production of EGF, the prototypical EGFR ligand, is restricted to submandibular glands and Brunner's glands in the normal gastrointestinal tract (22,23); however, in response to injury, the formation of ulcer-associated epithelial cell lineages may provide a localized source for EGF production in all regions of the gastrointestinal tract (24).…”

Expression of epithelial growth factor receptor, tumor necrosis factor-α and nuclear factor κB in inflammatory bowel diseases

“…Yoo et al ERK kinase and high cyclooxygenase 2 activity, which explained the potential role of EGF receptor both in inflammation and increased risk of carcinogenesis in IBD [14].…”

“…Yoo et al have shown that high TNF-α expression induces EGFR activation in myofibroblasts, which induces healing processes [14]. Interestingly, EGF topical treatment in an animal model of colitis and also in ulcerative colitis in humans induced remission of the disease with almost complete mucosal healing.…”

Isolation of Primary Myofibroblasts from Mouse and Human Colon Tissue

“…Primary myofibroblasts can be obtained from human and mouse colon tissue to confirm experimental findings identified in a cell line 7 . The method was originally described by Mahida,et al 8 , and our protocol is one of many well-described techniques that can be used to isolate primary myofibroblasts from mouse and human colon 9 .…”