HGF and breast cancer: The genetic or pharmacological inhibition of EGF, CSF-1, or the HGF receptor (c-Met) significantly impairs streaming of both tumor cells and macrophages and blocks tumor cell dissemination in in vivo breast cancer metastasis models, confirming the critical role of the paracrine CSF-1/EGF loop between tumor cells and macrophages, as well as the HGF gradient, in metastasis.