1A) [2]. In contrast to the HMEC growth as AZD3965 a monolayer, HBCEC cultures revealed a multilayer cell growth and were connected to each other by numerous desmosomes (Fig. 1B). Figure 1 Characterization of primary human breast cancer epithelial cells (HBCEC). A. Scanning electron micrographs of human breast cancer-derived cell cultures. The cells are squamous with many short and thin processes and grow upon each other.

B. Ultrathin sections of two human breast cancer-derived cells, which partially overlap and are connected by desmosomes. The cells contain bundles of intermediate filaments and cytoplasmic vacuoles, whereas organelles are almost

absent. In the right transmission micrograph, two squamous cell processes are connected by desmosomes and bundles PLX-4720 molecular weight of intermediate filaments are orientated in parallel to the cell surface. C. Immunofluorescence of intermediate filaments. Nuclei became visual using DAPI and the intermediate filament proteins cytokeratin (green) and vimentin (red) were detected by FITC-conjugated mouse anti-cytokeratin and mouse anti-vimentin antibody, respectively. D. Quantification of cytokeratin, vimentin and desmin expression by flow cytometric analysis. About 99% of the HBCEC population stained positive for cytokeratin, whereof some were positive for both, cytokeratin and vimentin intermediate filament proteins. Expression of desmin intermediate filaments remained undetectable. The FITC-labeled IgG control and the

secondary antibody control Ribose-5-phosphate isomerase served as background staining balance. Immunofluorescence staining exhibited a significantly green-colored cytokeratin expression within all of the HBCEC cultures (Fig. 1C), demonstrating epithelial-like cells rather than a contamination with other cell types such as fibroblasts. Additional testing for the fibroblast-specific prolyl-4-hydroxylase remained below detection limit in HBCEC cultures (data not shown). Co-immunofluorescence analysis was performed with red-labeled vimentin, which also appeared in certain cells (Fig. 1C). Blue DAPI staining of the nuclei and an overlay image revealed a co-expression of cytokeratin and vimentin in a variety of cells, demonstrating a different intracellular localization of these intermediate filaments (Fig. 1C). Quantification of vimentin and cytokeratin expression by flow cytometry revealed about 99% of cytokeratin-positive cells, whereby about 32% of this population demonstrated both, vimentin-positive and cytokeratin-positive cells, respectively (Fig. 1D).