Figure 1

Derivation of a tumorigenic cell line (R2N1d) and characteristics of R2N1d cells. A, a diagram showing the development of R2d cells which are non-tumorigenic and R2N1d cells which are highly tumorigenic. Both R2d and R2N1d cells were derived from the same immortal cell line M13SV1 and cultured for >10 passages under same cell culture condition before experiment using MSU-1 medium without growth factors and hormones (except 5% FBS). B, expression of ER-α and HER2 in R2N1d cells by immunocytochemical staining (green fluorescence). Cell nuclei were stained with DAPI and recognized as blue fluorescence (top figure, image observed under fluorescence microscope; bottom figure, the mergence of fluorescence and phase images, scale bar = 100 μm). C, R2N1d cells were labelled with antibodies against CK-18, CK-19, Msi1, Notch-1, Notch-4 and Oct-4 for immunophenotyping by flow cytometric analysis. The open histograms indicate background signal and shaded histograms showing positive reactivity.