Monocyte chemoattractant protein‐1 is generated via TGF‐β by myofibroblasts in gastric intestinal metaplasia and carcinoma without H. pylori infection

Abstract

Helicobacter pylori (H. pylori) stimulates secretion of monocyte chemoattractant protein 1 (MCP-1) from gastric mucosa. Monocyte chemoattractant protein-1 (MCP-1) expression and macrophage infiltration are recognized in human gastric carcinoma. We have previously generated Cdx2-transgenic mice as model mice for intestinal metaplasia. Both chronic H. pylori-associated gastritis and Cdx2-transgenic mouse stomach develop intestinal metaplasia and finally gastric carcinoma. In this study we have directed our attention to MCP-1 expression in the intestinal metaplastic mucosa and the gastric carcinoma of Cdx2-transgenic mouse stomach. Quantitative real-time PCR was performed to determine MCP-1 and transforming growth factor-beta1 (TGF-beta1) mRNA expression levels and single- or double-label immunohistochemistry was used to evaluate the localization of MCP-1, TGF-beta type I receptor, and alpha-smooth muscle actin (alphaSMA). We determined that MCP-1 mRNA dramatically increased in the intestinal metaplastic mucosa and the gastric carcinoma of Cdx2-transgenic mouse stomach, compared with normal mouse stomach. Both MCP-1 and TGF-beta type I receptor were co-expressed in the alphaSMA-positive myofibroblasts of intestinal metaplastic mucosa and gastric carcinoma. Exogenous application of TGF-beta1 increased MCP-1 mRNA expression levels in the intestinal metaplastic tissue. Furthermore, TGF-beta1 was overexpressed and macrophage was strongly infiltrated in the gastric carcinoma. In conclusion, MCP-1 expression, which was stimulated by TGF-beta1, was recognized in the TGF-beta type I receptor-expressing myofibroblasts of the intestinal metaplastic mucosa and the gastric carcinoma of Cdx2-transgenic mouse stomach. The present results suggest that intestinal metaplasia and gastric carcinoma themselves induce MCP-1 expression independently of H. pylori infection.