Mir-21-Sox2 Axis Delineates Glioblastoma Subtypes with Prognostic Impact.

UNLABELLED: Glioblastoma (GBM) is the most aggressive human brain tumor. Although several molecular subtypes of GBM are recognized, a robust molecular prognostic marker has yet to be identified. Here, we report that the stemness regulator Sox2 is a new, clinically important target of microRNA-21 (miR-21) in GBM, with implications for prognosis. Using the MiR-21-Sox2 regulatory axis, approximately half of all GBM tumors present in the Cancer Genome Atlas (TCGA) and in-house patient databases can be mathematically classified into high miR-21/low Sox2 (Class A) or low miR-21/high Sox2 (Class B) subtypes. This classification reflects phenotypically and molecularly distinct characteristics and is not captured by existing classifications. Supporting the distinct nature of the subtypes, gene set enrichment analysis of the TCGA dataset predicted that Class A and Class B tumors were significantly involved in immune/inflammatory response and in chromosome organization and nervous system development, respectively. Patients with Class B tumors had longer overall survival than those with Class A tumors. Analysis of both databases indicated that the Class A/Class B classification is a better predictor of patient survival than currently used parameters. Further, manipulation of MiR-21-Sox2 levels in orthotopic mouse models supported the longer survival of the Class B subtype. The MiR-21-Sox2 association was also found in mouse neural stem cells and in the mouse brain at different developmental stages, suggesting a role in normal development. Therefore, this mechanism-based classification suggests the presence of two distinct populations of GBM patients with distinguishable phenotypic characteristics and clinical outcomes. SIGNIFICANCE STATEMENT: Molecular profiling-based classification of glioblastoma (GBM) into four subtypes has substantially increased our understanding of the biology of the disease and has pointed to the heterogeneous nature of GBM. However, this classification is not mechanism based and its prognostic value is limited. Here, we identify a new mechanism in GBM (the miR-21-Sox2 axis) that can classify ∼50% of patients into two subtypes with distinct molecular, radiological, and pathological characteristics. Importantly, this classification can predict patient survival better than the currently used parameters. Further, analysis of the miR-21-Sox2 relationship in mouse neural stem cells and in the mouse brain at different developmental stages indicates that miR-21 and Sox2 are predominantly expressed in mutually exclusive patterns, suggesting a role in normal neural development

TMEM43/LUMA is a key signaling component mediating EGFR-induced NF-κB activation and tumor progression

Epidermal growth factor receptor (EGFR) family members play pivotal roles in cell proliferation, differentiation and survival. Overexpression and mutations of EGFRs, or aberrant EGFR signaling are commonly associated with the development of various cancers, where constitutive NF-{kappa}B activation is often found to promote the expression of various proteins involved in the proliferation, survival, migration and epithelial-to-mesenchymal transition of cancer cells. However, the mechanism of EGFR-induced NF-{kappa}B activation is not fully defined. Here, we used a Bimolecular Fluorescence Complementation-based functional genomics method to perform a high throughput screening and identified TMEM43/LUMA as a critical component in EGFR signaling network, mediating EGFR-induced NF-{kappa}B activation. Our data show that EGFR recruits TMEM43 following EGF stimulation. TMEM43 interacts with the scaffold protein CARMA3 and its associating complex to induce downstream NF-{kappa}B activation, and plays a critical role in controlling cell survival. TMEM43 deficiency significantly affects colony formation, survival of anoikis-induced cell death, migration and invasion of cancer cells in vitro, as well as tumor progression in vivo. Importantly, higher expression of TMEM43 closely correlates with brain tumor malignancy, and suppression of TMEM43 expression in brain tumor cells inhibited their growth both in vitro and in vivo. Altogether, our studies reveal a crucial link of EGF receptor to NF-{kappa}B activation and tumor progression