Significance of stromal decorin expression during the progression of breast cancer.

Decorin, a small leucine-rich proteoglycan and important component of the extracellular matrix (ECM), is a natural anticancer agent that modulates several receptors involved in cell growth and survival. Reductions in decorin expression may weaken the ECM and enhance the effectiveness of these receptors and may, consequently, lead to tumor spreading. To determine the contribution of stromal decorin regulation in the development of breast cancer and in tumor invasiveness, immunohistochemistry was used to examine the expression of stromal decorin in 120 breast cancer tissue samples. In patients with invasive breast carcinoma (IBC), stromal decorin expression was highest in normal gland tissue, lower in in situ components and the lowest in invasive components. Stromal decorin expression adjacent to malignant cells in IBC tumors was also significantly weaker compared to that in pure ductal carcinoma in situ (DCIS). These findings indicate that there is a striking difference in the stromal decorin expression around normal glands and around DCIS or IBC tumors. Reduced levels of decorin were associated with more aggressive disease; this finding was consistent with the view that reduced decorin expression may facilitate tumorigenesis, tumor invasion and/or tumor growth. Given these and other reported findings, evaluating stromal decorin expression may be useful in assessing prognosis and malignant potential; therefore, a large-scale study of decorin expression is warranted.