a, Three WT/PyMT (Mtdh+/+) and KO/PyMT (Mtdh−/−) cell lines were injected into FVB female mice via tail vein. Five weeks after injection, lungs were fixed, and numbers of metastatic nodules were quantified. n=6 mice per group. b, Representative lungs from (a) are shown. c, KO/PyMT cell lines that were rescued with vector or wild type MTDH were employed for tail vein injection. Five weeks after injection, lung metastatic nodules were counted. n=6 female FVB mice per group. d, WT/PyMT cells with/without endogenous Mtdh knockdown were injected in to female FVB mice intravenously. Numbers of lung nodules and representative lungs were shown. n=6 mice per group. e,
PyMT;UBC-CreERT+/−;Mtdhfl/fl tumors with or without MTDH acute knockout (KO) were collected for RNA sequencing and GSEA. p and q values automatically determined by GSEA 3.0. Tmx, Tamoxifen. n=4 mice per group. f, FVB female mice were injected with CD4 and CD8 neutralizing antibodies or isotype control (IgG) for 3 days. Peripheral blood was collected to examine the depletion of CD4 and CD8. % of CD4 and CD8 in CD45+ populations are shown. n=6 mice. g, FVB females were inoculated with WT/PyMT or KO/PyMT cells via tail vein. The mice were treated with anti-CD4 or CD8 neutralization antibodies or IgG. Five weeks after injection, numbers of lung metastasis nodules were counted. n=6 mice per group. h, FVB females inoculated with KO/PyMT cells via tail vein were treated with anti-CD8 antibody or IgG. The survival of mice was plotted. KO+IgG, n=11 mice, KO+α-CD8, n=12 mice. i, WT/PyMT and KO/PyMT cells were inoculated into FVB females via mammary fat pad injections. The mice were treated with anti-CD8 neutralizing antibody or IgG. Eight weeks after injection, metastatic nodules were quantified. n=5 mice per group. In all lung images, size bar, 5 mm. Data represent mean ± SEM. Significance determined by two tailed Student’s t-test (a,c,d,i), one-way ANOVA analysis with Sidak’s test for multiple comparisons (g), or Log-rank test (h). Numerical source data for a, c, d, g, h, and i are provided.