As an additional analysis, we assessed the expression of the neuron-specific marker RBFOX3 [62], which was negatively correlated with ETG iNMDeff (TCGA: R = − 0.31, p = 4.4e − 15; GTex: R = − 0.30, p < 2.2e − 16), whereas the glia-specific marker AQP4 [63] was positively correlated with iNMDeff (TCGA: R = 0.15, p = 2.2e − 4; GTex: R = 0.32, p < 2.2e − 16) supporting that neural cells in specific, rather than glia or other cell types infiltrating these tumor samples, are the cell types with lowered NMD activity in the central nervous system (Additional File 1: Fig. S11A-B). This evidence concerns the gene AQP4 and neoplasm.