NOS1 and glioblastoma: The GSEA also indicated that the gene sets related to ID4, NOS, NFκB, and STAT3 were highly enriched in recurrent GBM samples (Fig. 7d; and Supplementary Fig. 10d), indicating that the increased expression of cytokine/chemokine genes in patients with recurrent GBM is associated with NFκB and STAT3 signaling.