In glioblastoma, CSCs induce Treg cell infiltration mediated by the costimulatory molecule PD-L1, soluble Galectin-3, and TGF-β secretion (Wei et al., 2010, 2011), whereas ABCB5+ melanoma cells induce Treg cell infiltration via a B7-2-dependent mechanism (Schatton et al., 2010). Here, TGFB1 is linked to melanoma.