On the other hand, studies directly evaluating the role of the TGF-β on the ABCB1 function showed conflicting effects, as it was seen that endothelial cells of the cerebral microvasculature suffered an increase in their activity, while gliomas obtained from patients that naturally expressed high levels of ABCB1 suffered inhibition of activity when incubated with cytokine [38,39]. This evidence concerns the gene ABCB1 and glioma.