FIGURE 1. Selection of breast cancer cells metastatic to lung.

a, Flow chart of the selection of organ-specific metastatic subpopulations in vivo, indicating the organs from which these subpopulations were isolated. Each subsequent lung-metastatic generation is designated LM0, LM1 and LM2. The LM2 cells were further analysed for metastasis by either tail-vein (TV) or intracardiac (IC) xenografting. Metastatic propensities for all cell lines used in this study are listed in Supplementary Table 1. b, Representative lungs harvested at necropsy and BLI of the indicated cell lines are shown after tail-vein or intracardiac injection. The colour scale depicts the photon flux (photons per second) emitted from xenografted mice c, A representative image of haematoxylin staining of lung cryosections from mice injected with moderately metastatic 1834 cells showing an invading lesion (asterisk) and an embolus within the vascular space (arrowhead). Vascular walls are stained with the endothelial cell marker CD31. d, Parental cells (red) and 4175 (LM2) cells (blue) were tested for lung metastatic activity. Numbers of cells injected were as follows: diamonds, 2 10⁵; triangles, 2 10⁴; squares, 2 10³. Plots show a quantification of the luminescence signal as a function of time. Results are means s.e.m. for each cohort. Asterisks, P < 0.05 with a one-sided rank test, compared with mice injected with an equivalent number of parental cells.