In contrast, the expression of CB1 still requires characterization, as it has been reported to be either unchanged (Schley et al., 2009), decreased (De Jesús et al., 2010) or even increased (Wu et al., 2012; Ciaglia et al., 2015) in GBM compared to low-grade gliomas or non-tumor control tissues. Here, CNR1 is linked to central nervous system cancer.