MGMT and glioma: HIF-1 would repress core-derived glioma cell differentiation through the suppression of Smad activation (Pistollato et al., 2009a,b), maintaining a higher number of stem cells that express greater levels of the DNA repair protein MGMT (O6-methylguanine-DNA-methyltransferase) and consequently turn to be more radioresistant (Pistollato et al., 2009a, 2010).