ABSTRACT
BACKGROUND: S100 family proteins have recently been identified as biomarkers in various cancers. Of this protein family, S100A14 and S100A16 are also believed to play an important role in tumor progression. The aim of the present study was to clarify the clinical significance and functional role of these molecules in breast cancer. METHODS: In a clinical study, an immunohistochemical analysis of S100A14 and S100A16 expression in archival specimens of primary tumors of 167 breast cancer patients was performed. The relationship of S100A14 and S100A16 expression to patient survival and clinicopathological variables was statistically analyzed. In an experimental study, the subcellular localization and function of these molecules was examined by using the human breast cancer cell lines MCF7 and SK-BR-3, both of which highly express S100A14 and S100A16 proteins. Cells transfected with expression vectors and siRNA for these genes were characterized using in vitro assays for cancer invasion and metastasis. RESULTS: Immunohistochemical analysis of 167 breast cancer cases showed strong cell membrane staining of S100A14 (53% of cases) and S100A16 (31% of cases) with a significant number of cases with co-expression (p < 0.001). Higher expression levels of these proteins were significantly associated with a younger age (<60 years), ER-negative status, HER2-positive status and a poorer prognosis. Co-expression of the two proteins showed more aggressive features with poorer prognosis. In the human breast cancer cell lines MCF7 and SK-BR-3, both proteins were colocalized on the cell membrane mainly at cell-cell attachment sites. Immunoprecipitation and immunofluorescence analyses demonstrated that the 100A14 protein can bind to actin localized on the cell membrane in a calcium-independent manner. A Boyden chamber assay showed that S100A14 and S100A16 knockdown substantially suppressed the invasive activity of both cell lines. Cell motility was also inhibited by S100A14 knockdown in a modified dual color wound-healing assay. CONCLUSIONS: To our knowledge, this is the first report showing the correlation of expression of S100A14, S100A16, and co-expression of these proteins with poor prognosis of breast cancer patients. In addition, our findings indicate that S100A14 and S100A16 can promote invasive activity of breast cancer cells via an interaction with cytoskeletal dynamics. S100A14 and S100A16 might be prognostic biomarkers and potential therapeutic targets for breast cancer.
Subject(s)
Breast Neoplasms/genetics , Breast Neoplasms/mortality , Calcium-Binding Proteins/genetics , Gene Expression , S100 Proteins/genetics , Actins/metabolism , Adult , Aged , Biomarkers, Tumor , Breast Neoplasms/pathology , Breast Neoplasms/surgery , Calcium-Binding Proteins/metabolism , Cell Line, Tumor , Cell Movement/genetics , Female , Gene Knockdown Techniques , Humans , Immunohistochemistry , Middle Aged , Neoplasm Grading , Neoplasm Staging , Prognosis , Protein Binding , Protein Transport , S100 Proteins/metabolismABSTRACT
Reticulocalbin (RCN) is one member of the Ca(2+)-binding proteins in the secretory pathway and is localized in the endoplasmic reticulum. RCN may play a role in the normal behavior and life of cells, although its detailed role remains unknown. Overexpression of RCN may also play a role in tumorigenesis, tumor invasion, and drug resistance. The new antibody for human RCN is used in the distribution of RCN in normal human organs of fetuses and adults with or without inflammation. Immunohistochemical examination demonstrated a broad distribution of RCN in various organs of fetuses and adults, predominantly in the endocrine and exocrine organs. However, RCN expression was heterogeneous in each constituent cell of some organs. Among non-epithelial organs, vascular endothelial cells, testicular germ cells, neurons, and follicular dendritic cells showed strong staining. Plasma cells were the only RCN-positive cells among hematopoietic and lymphoid cells. In inflammatory conditions, RCN expression was enhanced in both epithelial and non-epithelial cells. Heterogeneous expression of RCN indicates that the amount of RCN needed for cell behavior and life may be variable, depending on each cell type and, therefore, RCN may be helpful in establishing the cell origin of neoplasms in some organs. However, further study is needed to establish the significance of RCN in tumorigenesis and in some peculiar features of neoplasms.