Fig. 1

Early dissemination of mammary cells from the MMTV–PyMT transgenic model of breast cancer. A Increase in tumor area in MMTV–PyMT-Green (MPG) transgenic female mice (number of mice = 5) over time. Data are expressed as mean ± standard deviation. B The mammary gland and mammary gland-derived cells (MDCs) in MPG mice at 4 weeks (number of mice = 5). Histological sections of mammary glands showing that lateral buds display the morphology of atypical ductal hyperplasia (ADH). Scale bar, 50 μm. C Proliferation and invasive capacities in GFP-positive cells isolated from ADH areas (ADH) or lung tissues (MDC) of 4-week-old MPG mice, normal cells (normal) digested from wild-type syngeneic mice and GFP-positive cells isolated from the breast tumor (tumor) of 12-week-old MPG mice, as assessed by MTT (a) and in vitro invasion assay (b), respectively. Data were quantified and presented as the mean ± SD of triplicate experiments. *P < 0.05, **P < 0.01, ***P < 0.001by Student’s t-test. D GFP-positive cells isolated from ADH areas of 4-week-old MPG mice (donor mice = 8) were transplanted subcutaneously (left panel) or orthotopically (right panel) into syngeneic wild-type (WT) recipient mice (1 million cells/mice, recipient mice = 40). Histopathology of transplanted mammary cells at 18 weeks after transplantation. Scale bar, 200 μm. E FACS-sorted early MDC cells (E-MDCs) from the lung of MPG mice (donor mice = 20) at 4 weeks were transplanted into the mammary gland of syngeneic WT recipient animals (1 million cells/mice, recipient mice = 20). Histopathology of the mammary gland at 4 weeks (left panel) or 18 weeks (right panel) after transplantation. n = number of donor or recipient mice. Scale bar, 200 μm