Detection of disseminated cells in WT recipient mice after inoculation with lung tissue cells from GFP MMT mice. (a) Mammary glands harvested from mice transgenic for PyMT and MUC1 antigen (MMT) that also express green fluorescent protein (GFP MMT) were processed for histological examination under light or fluorescence microscopy (60 x). (b) Colony-forming assay. WT mice were injected with lung tissue cells isolated from GFP MMT mice at the indicated ages. Lungs were then collected and perfused to remove circulating cells. Single-cell suspensions from the lungs were cultured in DMEM for two weeks. Colonies with GFP and Sca1 expression were observed under fluorescence microscopy (lower panels). (c) Detection of GFP and CD44-positive cells in blood vessels of lung from a WT recipient mouse. Samples from the recipient lungs were also processed for staining with H&E or anti-CD44 monoclonal antibodies.