Merlin, a "magic" linker between extracellular cues and intracellular signaling pathways that regulate cell motility, proliferation, and survival.

Department of Oncological Sciences, Mount Sinai School of Medicine, New York, NY10029, USA.
Current Protein and Peptide Science (Impact Factor: 2.33). 09/2010; 11(6):471-84. DOI: 10.2174/138920310791824011
Source: PubMed

ABSTRACT Genetic alterations of neurofibromatosis type 2 (NF2) gene lead to the development of schwannomas, meningiomas, and ependymomas. Mutations of NF2 gene were also found in thyroid cancer, mesothelioma, and melanoma, suggesting that it functions as a tumor suppressor in a wide spectrum of cells. The product of NF2 gene is merlin (moesin-ezrin-radixin-like protein), a member of the Band 4.1 superfamily proteins. Merlin shares significant sequence homology with the ERM (Ezrin-Radixin-Moesin) family proteins and serves as a linker between transmembrane proteins and the actin-cytoskeleton. Merlin is a multifunctional protein and involved in integrating and regulating the extracellular cues and intracellular signaling pathways that control cell fate, shape, proliferation, survival, and motility. Recent studies showed that merlin regulates the cell-cell and cell-matrix adhesions and functions of the cell surface adhesion/extracellular matrix receptors including CD44 and that merlin and CD44 antagonize each other's function and work upstream of the mammalian Hippo signaling pathway. Furthermore, merlin plays important roles in stabilizing the contact inhibition of proliferation and in regulating activities of several receptor tyrosine kinases. Accumulating data also suggested an emerging role of merlin as a negative regulator of growth and progression of several non-NF2 associated cancer types. Together, these recent advances have improved our basic understanding about merlin function, its regulation, and the major signaling pathways regulated by merlin and provided the foundation for future translation of these findings into the clinic for patients bearing the cancers in which merlin function and/or its downstream signaling pathways are impaired or altered.

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    ABSTRACT: Advanced malignant mesothelioma (MM) is among the most aggressive and difficult-to-treat diseases. Industrialization and exposure to asbestos is the main causative factor for the dramatic increase in the incidence of MM, which carries a poor prognosis and a median survival of less than 12 months. Combination chemotherapy offers only palliative results; however, targeted therapy carries more promise for future successful treatment. This paper presents preliminary findings of improved overall survival (OS) using a combination of sodium phenylbutyrate (PB) with various chemotherapeutic and targeted agents in advanced MM. The data suggest using a strategy of simultaneous interruption of signal transduction involving RAS-MEK-ERK, PI3K-AKT, mTOR, Merlin, and angiogenesis pathways and interference in cell cycle and epigenetic processes. Complete response was determined in 15.4% and stable disease in 46.2% in the group of 13 evaluable patients. Median OS for MM was higher compared to other treatments (17 months compared to between 6 and 12.1 months). The longest surviving patient continues to be in complete response and in excellent condition for over 12.5 years from the treatment start. These findings are only preliminary and validation of the results using a well-designed phase I/II trial in advanced MM is proposed.
    Journal of Cancer Therapy 10/2014; 5:1127-1144.
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    ABSTRACT: Mutations in the merlin tumor suppressor gene cause Neurofibromatosis type 2 (NF2), which is a disease characterized by development of multiple benign tumors in the nervous system. The current standard of care for NF2 calls for surgical resection of the characteristic tumors, often with devastating neurological consequences. There are currently no approved non-surgical therapies for NF2. In an attempt to identify much needed targets and therapeutically active compounds for NF2 treatment, we employed a chemical biology approach using ultra-high-throughput screening. To support this goal, we created a merlin-null mouse Schwann cell (MSC) line to screen for compounds that selectively decrease their viability and proliferation. We optimized conditions for 384-well plate assays and executed a proof-of-concept screen of the Library of Pharmacologically Active Compounds. Further confirmatory and selectivity assays identified phosphatidylinositol 3-kinase (PI3K) as a potential NF2 drug target. Notably, loss of merlin function is associated with activation of the PI3K/Akt pathway in human schwannomas. We report that AS605240, a PI3K inhibitor, decreased merlin-null MSC viability in a dose-dependent manner without significantly decreasing viability of control Schwann cells. AS605240 exerted its action on merlin-null MSCs by promoting caspase-dependent apoptosis and inducing autophagy. Additional PI3K inhibitors tested also decreased viability of merlin-null MSCs in a dose-dependent manner. In summary, our chemical genomic screen and subsequent hit validation studies have identified PI3K as potential target for NF2 therapy.
    American Journal of Translational Research 01/2014; 6(5):471-93. · 3.23 Impact Factor
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    ABSTRACT: Merlin, a tumor suppressor protein, controls essential steps of cell cycle, and its deficiency results in cellular overgrowth, proliferation, angiogenesis, invasion and metastasis. Lack of Merlin is responsible for neurofibromatosis-2, most schwannomas, and many meningiomas and ependymomas. We hypothesize that there is a role for statins to ameliorate Merlin's deficiency in this set of tumors by inhibiting a number of Merlin's downstream effectors, the small Rho-GTP-ases, and we present the relevant data. The ultimate goal is to offer a medical therapy promising to halt or reduce the tumor growth-rate in patients harboring Merlin-deficient neoplasms and to provide an adjuvant systemic therapy for patients undergoing stereotactic radio-surgery and partial tumor resection.
    Interdisciplinary Neurosurgery. 03/2014; 1(1):11–15.


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