Scientific Resources

BACKGROUND: Circulating tumor cells (CTCs) in the peripheral blood of breast cancer patients may be an important indicator of metastatic disease and poor prognosis. However,the use of experimental models is required to fully elucidate the functional consequences of CTCs. The purpose of this study was to optimize the sensitivity of multiparameter flow cytometry for detection of human tumor cells in mouse models of breast cancer. METHODS: MDA-MB-468 human breast cancer cells were serially diluted in whole mouse blood. Samples were lysed and incubated with a fluorescein isothiocyanate-conjugated anti-human leukocytic antigen antibody and a phycoerythrin-conjugated anti-mouse pan-leukocyte CD45 antibody. Samples were then immunomagnetically depleted of CD45-positive leukocytes,fixed,permeabilized,and stained with propidium iodide before flow cytometric analysis. RESULTS: Human breast cancer cells could be differentiated from mouse leukocytes based on increased light scatter,cell surface marker expression,and aneuploid DNA content. The method was found to have a lower sensitivity limit of 10(-5) and was effective for detecting human breast cancer cells in vivo in the circulation of experimental mice carrying primary human mammary tumors. CONCLUSIONS: This technique has the potential to be a valuable and sensitive tool for investigating the biological relevance of CTCs in experimental mouse models of breast cancer. View Publication

The purpose of the present study was to characterize primitive epithelial progenitor populations present in adult normal human mammary tissue using a combination of flow cytometry and in vitro colony assay procedures. Three types of human breast epithelial cell (HBEC) progenitors were identified: luminal-restricted,myoepithelial-restricted and bipotent progenitors. The first type expressed epithelial cell adhesion molecule (EpCAM),alpha6 integrin and MUC1 and generated colonies composed exclusively of cells positive for the luminal-associated markers keratin 8/18,keratin 19,EpCAM and MUC1. Bipotent progenitors produced colonies containing a central core of cells expressing luminal markers surrounded by keratin 14+ myoepithelial-like cells. Single cell cultures confirmed the bipotentiality of these progenitors. Their high expression of alpha6 integrin and low expression of MUC1 suggests a basal position of these cells in the mammary epithelium in vivo. Serial passage in vitro of an enriched population of bipotent progenitors demonstrated that only myoepithelial-restricted progenitors could be readily generated under the culture conditions used. These results support a hierarchical branching model of HBEC progenitor differentiation from a primitive uncommitted cell to luminal- and myoepithelial-restricted progenitors. View Publication

Protein kinase CK2 (formerly casein kinase II) is a serine/threonine kinase overexpressed in many human tumors,transformed cell lines,and rapidly proliferating tissues. Recent data have shown that many cancers involve inappropriate reactivation of Wnt signaling through ectopic expression of Wnts themselves,as has been seen in a number of human breast cancers,or through mutation of intermediates in the Wnt pathway,such as adenomatous polyposis coli or beta-catenin,as described in colon and other cancers. Wnts are secreted factors that are important in embryonic development,but overexpression of certain Wnts,such as Wnt-1,leads to proliferation and transformation of cells. We report that upon stable transfection of Wnt-1 into the mouse mammary epithelial cell line C57MG,morphological changes and increased proliferation are accompanied by increased levels of CK2,as well as of beta-catenin. CK2 and beta-catenin co-precipitate with the Dvl proteins,which are Wnt signaling intermediates. A major phosphoprotein of the size of beta-catenin appears in in vitro kinase reactions performed on the Dvl immunoprecipitates. In vitro translated beta-catenin,Dvl-2,and Dvl-3 are phosphorylated by CK2. The selective CK2 inhibitor apigenin blocks proliferation of Wnt-1-transfected cells,abrogates phosphorylation of beta-catenin,and reduces beta-catenin and Dvl protein levels. These results demonstrate that endogenous CK2 is a positive regulator of Wnt signaling and growth of mammary epithelial cells. View Publication