Fig. 1. Conditional knockout of Dll1 significantly delays tumor initiation and lung metastasis in MMTV-PyMT model.

a Schematic shows the strategy to generate MMTV-PyMT; Dll1^cKO mice. b Western blot shows reduced Dll1 protein in PyMT-Dll1^cKO tumor cells compared to PyMT-Dll1^WT tumor cells. c The representative whole mount alum carmine-stained images show the hyperplasia stages of MMTV-PyMT in indicated Dll1 genotypes. Insets show a zoomed-in image to a difference in branching. n = 5 PyMT-Dll1^WT, n = 6 PyMT-Dll1^cKO hyperplastic mammary glands at the age of 8 weeks. d Kinetics of mammary tumor onset in MMTV-PyMT females of indicated genotypes as shown by Kaplan–Meier plot. PyMT-Dll1^WT (n = 22 mice) and PyMT-Dll1^cKO (n = 32 mice) were used. e Scatter plot shows the number of spontaneous tumors in PyMT-Dll1^WT (n = 22 mice) and PyMT-Dll1^cKO (n = 32 mice). The mammary gland was considered tumor-positive when the tumor was 3 × 3 mm in dimension. f The representative whole mount images show metastatic lung nodules (black arrows) in PyMT-Dll1^WT, which is absent in the PyMT-Dll1^cKO mice. The lung nodules were quantified under dissection microscope after 24-h fixation with bouin’s solution (please see method section for details). g The scatter plot shows the number of lung nodules in spontaneous tumors bearing PyMT-Dll1^WT and PyMT-Dll1^cKO mice (n = 7 mice per group). two-tailed Log-Rank test d and two-tailed unpaired Student’s t-test e, g were used to calculate p values. Data present two b or three c or seven f independent experiments. e, g Data are presented as the mean ± SEM. Scale bars, 500 µm c and 400 µm f. Source data are provided as a source data file.