These include PI3K signalling, CSF-1 driven tumorigenesis, the regulation of pulmonary metastasis of mammary carcinoma by CD4+ T-cells, the role of neutrophils in supporting lung metastasis in breast cancer, the CD44-mediated metastatic invasion during breast cancer, VEGF-mediated mammary tumour growth, TGF-β signalling, urokinase-mediated breast cancer metastasis, and the role of mitogen-activated protein kinase kinase kinase-1 in breast cancer metastasis [72,73,74,75,76,77,78,79,80]. This evidence concerns the gene CD4 and breast cancer.