Treatment of Vestibular Schwannoma Cells With ErbB Inhibitors

Department of Otolaryngology-Head and Neck Surgery, The Ohio State University Eye and Ear Institute, Columbus, Ohio 43212, USA.
Otology & neurotology: official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology (Impact Factor: 1.79). 02/2012; 33(2):244-57. DOI: 10.1097/MAO.0b013e31823e287f
Source: PubMed


Aberrant phosphorylation of ErbB family receptor tyrosine kinases (RTK) in human vestibular schwannomas (VSs) renders them susceptible to growth suppression by RTK inhibitors.
Recent evidence has implicated increased ErbB family receptor tyrosine kinase signaling in VS tumorigenesis; however, the characterization of ErbB receptor activity and the chemotherapeutic potential of RTK inhibitors in VS treatment have not been fully explored.
To confirm phosphorylation of ErbB receptors in VS, protein extracts from paired VS tumor-vestibular nerve samples were examined using phospho-RTK arrays. ErbB receptor phosphorylation was similarly examined in cultured schwannoma cells, normal Schwann cells, and VS tumor tissues using Western blotting. Also, VS tumor sections were immunostained for members of the ErbB receptor family. The effects of RTK inhibitors on ErbB phosphorylation and cell proliferation were assessed in schwannoma cells after epidermal growth factor receptor (EGFR) inhibitor (Erlotinib) and EGFR/ErbB2 inhibitor (Lapatinib) treatment.
VS tumor tissues consistently demonstrated higher levels of phosphorylated ErbB3 compared with paired vestibular nerves. However, cultured VS, malignant schwannoma, and normal Schwann cells demonstrated EGFR phosphorylation. Immunohistochemistry confirmed high expression of ErbB3 in a series of VS tumor sections. Erlotinib inhibited schwannoma cell proliferation with an IC50 value of 2.5 µmol/L, whereas Lapatinib was less potent for growth inhibition. Erlotinib treatment resulted in a decrease of multiple phospho-ErbB receptors in schwannoma cells.
VS variably express activated ErbB receptors with consistently higher levels of phospho-ErbB3 expression relative to paired vestibular nerve samples. Chemotherapeutic targeting of ErbB3 may be a novel means of inhibiting VS growth.

  • Source
    • "Since over 75% of pediatric ependymomas express ErbB2 [26] and increased ErbB family receptor tyrosine kinase signaling has been reported in the hallmark NF2-associated tumor (vestibular schwannoma) [27], [28] we examined ErbB2 activation in normal human spinal cord and in two representative spinal ependymomas from individuals with a confirmed diagnosis of NF2. These tumors are not typically removed, thus limiting a more exhaustive analysis. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Individuals with the neurofibromatosis type 2 (NF2) cancer predisposition syndrome develop spinal cord glial tumors (ependymomas) that likely originate from neural progenitor cells. Whereas many spinal ependymomas exhibit indolent behavior, the only treatment option for clinically symptomatic tumors is surgery. In this regard, medical therapies are unfortunately lacking due to an incomplete understanding of the critical growth control pathways that govern the function of spinal cord (SC) neural progenitor cells (NPCs). To identify potential therapeutic targets for these tumors, we leveraged primary mouse Nf2-deficient spinal cord neural progenitor cells. We demonstrate that the Nf2 protein, merlin, negatively regulates spinal neural progenitor cell survival and glial differentiation in an ErbB2-dependent manner, and that NF2-associated spinal ependymomas exhibit increased ErbB2 activation. Moreover, we show that Nf2-deficient SC NPC ErbB2 activation results from Rac1-mediated ErbB2 retention at the plasma membrane. Collectively, these findings establish ErbB2 as a potential rational therapeutic target for NF2-associated spinal ependymoma.
    PLoS ONE 05/2014; 9(5):e97320. DOI:10.1371/journal.pone.0097320 · 3.23 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Recent evidence suggests that the neurofibromatosis type 2 (NF2) gene encoded protein merlin suppresses mitogenic signalling not only at the cell membrane but also in the nucleus. At the membrane, merlin inhibits signalling by integrins and tyrosine receptor kinases (RTKs) and the activation of downstream pathways, including the Ras/Raf/MEK/ERK, FAK/Src, PI3K/AKT, Rac/PAK/JNK, mTORC1, and Wnt/β-catenin pathways. In the nucleus, merlin suppresses the E3 ubiquitin ligase CRL4(DCAF1) to inhibit proliferation. Gene expression analysis suggested that CRL4(DCAF1) could also regulate the expression of integrins and RTKs. In this review, we explore the links between merlin function at the membrane and in the nucleus, and discuss the potential of targeting the master regulator CRL4 (DCAF1) to treat NF2 and other merlin-deficient tumours.
    FEBS letters 03/2012; 586(10):1403-8. DOI:10.1016/j.febslet.2012.03.016 · 3.17 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: BACKGROUND:: Radiosurgery is increasingly used to treat vestibular schwannomas (VSs). Increasing the sensitivity of VS cells to irradiation (IR) could allow for lower and/or more effective doses of IR, improving safety and efficacy. Persistent c-Jun N-terminal kinase (JNK) activity in VS cells reduces cell death by suppressing accumulation of reactive oxygen species (ROS), raising the possibility that JNK activity protects against IR-induced VS cell death, which is mediated by ROS. OBJECTIVE:: To determine the extent to which JNK signaling contributes to VS cell radiosensitivity. METHODS:: Primary human VS cultures, derived from acutely resected tumors, received single doses (5-40 Gy) of γ-irradiation. Histone 2AX phosphorylation, a marker of IR-induced DNA damage, was assayed by western blot and immunostaining. ROS levels were quantified by measuring 2',7'-dichlorodihydrofluorescein diacetate (CM-H2DCFDA) fluorescence. Cell apoptosis was determined by terminal deoxynucleotidyl transferase dUTP nick end labeling. RESULTS:: The JNK inhibitors, SP6000125 and I-JIP, reduced H2AX phosphorylation following IR. They also increased H2DCFDA fluorescence in non-irradiated cultures and significantly increased IR-induced (5-10 Gy) H2DCFDA fluorescence 72 hours, but not 2 hours, after IR. Finally, I-JIP (50 μM) significantly increased VS cell apoptosis in cultures treated with 20-40 Gy. I-JIP (20 μM), SP600125 (20 μM), and JNK1/2 siRNA knock-down each increased VS cell apoptosis in cultures treated with 30-40 Gy, but not lower doses, of IR. CONCLUSION:: Inhibition of JNK signaling decreases H2AX phosphorylation and increases ROS and apoptosis in VS cells following γ-irradiation. These results raise the possibility of using JNK inhibitors to increase the effectiveness of radiosurgery for treatment of VSs.
    Neurosurgery 05/2013; 73(3). DOI:10.1227/01.neu.0000431483.10031.89 · 3.62 Impact Factor
Show more