YKL-40 expression in breast cancer

Abstract

9665 Background: YKL-40, a heparinbinding glycoprotein, is a growth factor for connective tissue cells and stimulates migration of endothelial cells. High serum YKL-40 levels are associated with a poor prognosis in patients with metastatic breast cancer, colorectal, ovarian and small cell lung cancer. The function of YKL-40 in cancer is unknown, but in vitro observations suggest an involvement in cell proliferation, angiogenesis and extracellular matrix remodelling. The expression of YKL-40 in breast cancer tissue has never been described. The aim of this study was to determine the expression of YKL-40 in breast cancer by immunohistochemistry and in situ hybridisation. Methods: Tissue sections from 55 patients with primary breast cancer were stained using a monoclonal antibody against YKL-40. The intensity of YKL-40 staining in tumor cells was scored using a semi-quantitative method. Results: YKL-40 protein expression in tumor cells appeared as a dense cytoplasmic granular staining. No nuclear or membrane staining was found. 31 of 42 (74%) invasive ductal carcinomas and 7 of 11 (64%) invasive lobular carcinomas stained positive for YKL-40. Macrophages and leucocytes showed YKL-40 expression whereas lymphocytes were negative. In normal breast glands the epithelial cells appeared with a granular apical staining. The myoepithelial cells appeared negative. In the stroma the fibroblasts were weakly stained. YKL-40 protein expression was confirmed by in situ hybridisation. Conclusions: In the present study an overexpression of YKL-40 was found in the epithelial cells of both invasive ductal and lobular carcinomas of the breast compared to normal breast tissue. These data suggest that the tumor cells in breast cancer are the primary source of elevated serum YKL-40 levels as opposed to small cell lung cancer, where macrophages are the primary source of elevated serum YKL-40 levels. Further studies are needed to determine the significance of these findings in the clinical setting. No significant financial relationships to disclose.