Abstract
Glioblastoma is the most common and aggressive primary brain tumor in adults, with a poor prognosis because of its resistance to radiotherapy and chemotherapy. Merlin/NF2 (moesin-ezrin-radixin-like protein/neurofibromatosis type 2) is a tumor suppressor found to be mutated in most nervous system tumors; however, it is not mutated in glioblastomas. Merlin associates with several transmembrane receptors and intracellular proteins serving as an anchoring molecule. Additionally, it acts as a key component of cell motility. By selecting sub-populations of U251 glioblastoma cells, we observed that high expression of phosphorylated Merlin at serine 518 (S518-Merlin), NOTCH1 and epidermal growth factor receptor (EGFR) correlated with increased cell proliferation and tumorigenesis. These cells were defective in cell-contact inhibition with changes in Merlin phosphorylation directly affecting NOTCH1 and EGFR expression, as well as downstream targets HES1 (hairy and enhancer of split-1) and CCND1 (cyclin D1). Of note, we identified a function for S518-Merlin, which is distinct from what has been reported when the expression of Merlin is diminished in relation to EGFR and NOTCH1 expression, providing first-time evidence that demonstrates that the phosphorylation of S518-Merlin in glioblastoma promotes oncogenic properties that are not only the result of inactivation of the tumor suppressor role of Merlin but also an independent process implicating a Merlin-driven regulation of NOTCH1 and EGFR.
Original language | English (US) |
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Pages (from-to) | 2621-30 |
Number of pages | 10 |
Journal | Oncogene |
Volume | 34 |
Issue number | 20 |
DOIs | |
State | Published - May 14 2015 |
Keywords
- Animals
- Basic Helix-Loop-Helix Transcription Factors
- Brain Neoplasms
- Cell Line, Tumor
- Cyclin D1
- Female
- Gene Expression Regulation, Neoplastic
- Glioblastoma
- Homeodomain Proteins
- Humans
- Mice
- Mice, Nude
- Neurofibromin 2
- Phosphorylation
- Receptor, Epidermal Growth Factor
- Receptor, Notch1
- Journal Article
- Research Support, N.I.H., Extramural