Fyn and Src Are Effectors of Oncogenic Epidermal Growth Factor Receptor Signaling in Glioblastoma Patients

Department of Pathology and Laboratory Medicine, University of California-Los Angeles David Geffen School of Medicine, USA.
Cancer Research (Impact Factor: 9.33). 09/2009; 69(17):6889-98. DOI: 10.1158/0008-5472.CAN-09-0347
Source: PubMed


Activating epidermal growth factor receptor (EGFR) mutations are common in many cancers including glioblastoma. However, clinical responses to EGFR inhibitors are infrequent and short-lived. We show that the Src family kinases (SFK) Fyn and Src are effectors of oncogenic EGFR signaling, enhancing invasion and tumor cell survival in vivo. Expression of a constitutively active EGFR mutant, EGFRvIII, resulted in activating phosphorylation and physical association with Src and Fyn, promoting tumor growth and motility. Gene silencing of Fyn and Src limited EGFR- and EGFRvIII-dependent tumor cell motility. The SFK inhibitor dasatinib inhibited invasion, promoted tumor regression, and induced apoptosis in vivo, significantly prolonging survival of an orthotopic glioblastoma model expressing endogenous EGFRvIII. Dasatinib enhanced the efficacy of an anti-EGFR monoclonal antibody (mAb 806) in vivo, further limiting tumor growth and extending survival. Examination of a large cohort of clinical samples showed frequent coactivation of EGFR and SFKs in glioblastoma patients. These results establish a mechanism linking EGFR signaling with Fyn and Src activation to promote tumor progression and invasion in vivo and provide rationale for combined anti-EGFR and anti-SFK targeted therapies.

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Available from: Stanley F Nelson, Jul 30, 2014
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    • "Stettner et al. analyzed GBM tumors at autopsy and showed that Lyn activity levels were significantly elevated compared to Src and Fyn activity , accounting for >90% of the SFK activity in the GBM samples , vs. 30% of the SFK activity in various non-GBM brain samples (Stettner et al., 2005). On the other hand, Lu et al. has demonstrated the importance of Fyn and Src to EGFR and EGFRvIII signaling in both cell culture and orthotopic xenograft contexts (Lu et al., 2009). Finally, Han et al. have shown that Src and Yes, but not Fyn, Lyn, or Lck, are important to glioma stem cell migration on laminin in culture (Han et al., 2014). "
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    ABSTRACT: Src-family kinase (SFK) signaling impacts multiple tumor-related properties, particularly in the context of the brain tumor glioblastoma. Consequently, the pan-SFK inhibitor dasatinib has emerged as a therapeutic strategy, despite physiologic limitations to its effectiveness in the brain. We investigated the importance of individual SFKs (Src, Fyn, Yes, and Lyn) to glioma tumor biology by knocking down individual SFK expression both in culture (LN229, SF767, GBM8) and orthotopic xenograft (GBM8) contexts. We evaluated the effects of these knockdowns on tumor cell proliferation, migration, and motility-related signaling in culture, as well as overall survival in the orthotopic xenograft model. The four SFKs differed significantly in their importance to these properties. In culture, Src, Fyn, and Yes knockdown generally reduced growth and migration and altered motility-related phosphorylation patterns while Lyn knockdown did so to a lesser extent. However the details of these effects varied significantly depending on the cell line: in no case were conclusions about the role of a particular SFK applicable to all of the measures or all of the cell types examined. In the orthotopic xenograft model, mice implanted with non-target or Src or Fyn knockdown cells showed no differences in survival. In contrast, mice implanted with Yes knockdown cells had longer survival, associated with reduced tumor cell proliferation. Those implanted with Lyn knockdown cells had shorter survival, associated with higher overall tumor burden. Together, our results suggest that Yes signaling directly affects tumor cell biology in a pro-tumorigenic manner, while Lyn signaling affects interactions between tumor cells and the microenvironment in an anti-tumor manner. In the context of therapeutic targeting of SFKs, these results suggest that pan-SFK inhibitors may not produce the intended therapeutic benefit when Lyn is present. Copyright © 2015. Published by Elsevier B.V.
    Molecular oncology 06/2015; 16(suppl 5). DOI:10.1016/j.molonc.2015.06.001 · 5.33 Impact Factor
    • "Indeed, SFKs are frequently hyperactivated or overexpressed in GB cell lines and tumor samples, suggesting that they act as drivers of tumorigenesis (Stettner et al., 2005; Du et al., 2009; Lu et al., 2009). Consistently, SFK inhibition through the multitargeted tyrosine kinase inhibitor dasatinib proved to have antitumor activity in GB cells both in vitro and in mouse models (Du et al., 2009; Lu et al., 2009; Milano et al., 2009). "
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    ABSTRACT: Glioblastoma (GB) is the most common and aggressive primary tumor of the central nervous system. The current standard of care for GB consists of surgical resection, followed by radiotherapy combined with temozolomide chemotherapy. However, despite this intensive treatment, the prognosis remains extremely poor. Therefore, more effective therapies are urgently required. Recent studies indicate that SRC family kinases (SFKs) could represent promising molecular targets for GB therapy. Here, we challenged four GB cell lines with a new selective pyrazolo[3,4-d]pyrimidine derivative SFK inhibitor, called SI221. This compound exerted a significant cytotoxic effect on GB cells, without significantly affecting non-tumor cells (primary human skin fibroblasts), as evaluated by MTS assay. We also observed that SI221 was more effective than the well-known SFK inhibitor PP2 in GB cells. Notably, despite the high intrinsic resistance to apoptosis of GB cells, SI221 was able to induce this cell death process in all the GB cell lines, as observed through cytofluorimetric analysis and caspase-3 assay. SI221 also exerted a long-term inhibition of GB cell growth and was able to reduce GB cell migration, as shown by clonogenic assay and scratch test, respectively. Moreover, through in vitro pharmacokinetic assays, SI221 proved to have a high metabolic stability and a good potential to cross the blood brain barrier, which is an essential requirement for a drug intended to treat brain tumors. Therefore, despite the need of developing strategies to improve SI221 solubility, our results suggest a potential application of this selective SFK inhibitor in GB therapy. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    Journal of Cellular Biochemistry 05/2015; 116(5). DOI:10.1002/jcb.25042 · 3.26 Impact Factor
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    • "Approximately 40% of GBMs shows EGFR gene amplification and overexpression [18,19].Amplification of the EGFR gene is often associated with a mutation that encodes for a truncated form of the receptor, known as EGFR variant vIII (EGFRvIII), lacking the extracellular binding domain and leading to constitutive activation of tyrosine kinases [20, 21]. Expression of EGFRvIII correlates with poor survival in GBM patients [22] and promotes glioma cell migration [23], tumor growth, invasion, survival [24] and angiogenesis [25]. Furhtermore, EGFRvIII causes enhanced apoptosis resistance. "
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    ABSTRACT: Malignant brain tumours are one of the most relevant causes of morbidity and mortality across a wide range of individuals. Malignant glioma is the most common intra axial tumor in the adult. Many researches on this theme brought advances in the knowledge of gliomas biology and pathogenesis and to the development of new agents for targeted molecular therapy. Recent studies focused on either tumor metabolism analysis or epigenetic regulation in the pathogenesis or maintenance of brain tumors. This Review summarizes these developments analyzing molecular pathology and possible further developments for targeted therapies.
    09/2014; 10:29-37.
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