Interestingly, brain metastatic cells can activate adjacent astrocytic and glial cells that in turn secrete a number of tumor-stimulating cytokines, including IL-6, interferon γ (IFN-γ), tumor necrosis factor-α (TNF-α), TGF-β, IGF-1, and PDGF-1 (Wang et al., 2013), thereby supporting the role of the metastatic microenvironment in the evolvement of the secondary disease. This evidence concerns the gene TNF and neoplasm.