The recruited macrophages express Hepatocyte Growth Factor, which reinforces activation of its receptor tyrosine kinase MET on GBM cells harboring a pronounced mesenchymal subtype driven by the key phenotypic regulator Fosl1. Indeed, orthotopic implantation of MET-expressing GBM cells corroborates their superior tumor-initiating and invasive capabilities. The gene discussed is FOSL1; the disease is glioblastoma.