Background: Recent studies showed that a small leucine-rich proteoglycan, decorin, may suppress tumor progression as a natural anticancer agent negatively controlling cellular growth. It was hypothesized that physiological expression of decorin may be associated with cellular senescence of the colorectal mucosa and that its down-regulation, promoting an increase in cellular proliferation, could participate in the progression of adenoma to adenocarcinoma. Therefore the expression of decorin in hyperplastic and neoplastic polyps of the colorectum was examined and compared with normal colonic mucosa and colon cancer tissues.
Material/methods: Tissue samples were obtained from 41 patients with different types of colonic polyps (6 hyperplastic adenomas, 34 neoplastic adenomas, and 1 adenomatous polyp with focal carcinoma) and 12 patients with colon cancer. Seven samples of normal colon tissue were used as controls. Paraffin-embedded samples were used for immunohistochemical study.
Results: Normal and hyperplastic tissues and the majority of tubular adenomas showed strong expression of decorin in the stroma. Adenomas with a villous component showed moderate and very low decorin immunoreactivity. The decrease in decorin reactivity in tubulo-villous adenomas was significant as compared with other polyps and controls. Weak decorin immunoreactivity in stroma adjacent to clusters of cancerous cells was also found in most cases of common types of adenocarcinoma, but not in adenocarcinoma mucinosum.
Conclusions: The expression of decorin may be involved in the differentiation of colonic polyps and reduced expression of decorin may abrogate the defensive potential of stromal tissue and promote the development of common types of colon carcinoma.