AHR and malignant glioma: It is known that TGF-β plays the role of AhR in signaling, and AhR is expressed in glioma cells in vitro (malignant glioma cell lines U87MG and T98G) and is detectable in human gliomas and glioblastomas (anaplastic astrocytomas WHO grade III and primary and recurrent glioblastomas grade IV [48]) in vivo by immunohistochemistry with predominantly nuclear staining [46,49].