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Molecular genetic analysis of the hepatocyte growth factor/MET signaling pathway in pediatric medulloblastoma

Authors

  • Sara Onvani,

    1. Arthur and Sonia Labatt Brain Tumour Research Centre, Department of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
    2. Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
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    • Both the authors contributed equally to this work.

  • Yuzo Terakawa,

    1. Arthur and Sonia Labatt Brain Tumour Research Centre, Department of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
    2. Department of Neurosurgery, Osaka City University Graduate School of Medicine, Osaka, Japan
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    • Both the authors contributed equally to this work.

  • Christian Smith,

    1. Arthur and Sonia Labatt Brain Tumour Research Centre, Department of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
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  • Paul Northcott,

    1. Arthur and Sonia Labatt Brain Tumour Research Centre, Department of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
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  • Michael Taylor,

    1. Arthur and Sonia Labatt Brain Tumour Research Centre, Department of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
    2. Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
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  • James Rutka

    Corresponding author
    1. Arthur and Sonia Labatt Brain Tumour Research Centre, Department of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
    2. Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
    3. RS McLaughlin Professor and Chairman, Department of Surgery, University of Toronto, Toronto, Ontario, Canada
    • The Banting Institute, 100 College Street, Room 311, Toronto, Ontario M5G 1L5
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Abstract

The hepatocyte growth factor (HGF)/MET pathway plays a critical role in the development of the nervous system and has been implicated in medulloblastoma pathogenesis. Recent studies have shown a role for gene amplification of activators of this pathway, as well as silencing of its inhibitors in medulloblastoma pathogenesis. We analyzed exon array data from a cohort of 103 primary medulloblastomas to show that HGF/MET pathway elements are dysregulated in tumors compared to normal cerebellum. To determine if mutation of HGF/MET pathway genes is a mechanism for pathway dysregulation, we conducted a mutational analysis by exon resequencing of three key components of this pathway, including serine protease inhibitor Kunitz-type 1 (SPINT1), serine protease inhibitor Kunitz-type 2 (SPINT2), and MET, in 32 primary human medulloblastoma specimens. From this analysis, we identified multiple coding synonymous and nonsynonymous single nucleotide polymorphisms in these genes among the 32 tumor samples. Interestingly, we also discovered two unreported sequence variants in SPINT1 and SPINT2 in two tumors that resulted in Arginine to Histidine amino acid substitutions at codons 418 and 233, respectively. However, conservation assessment and functional assays of these two variants indicate that they involve nonconserved residues and that they do not affect the function of SPINT1 and SPINT2 as tumor suppressor genes. In conclusion, our data suggest that mutation alone plays a minor role in causing aberrancies of the HGF/MET pathway in medulloblastoma in comparison with other malignancies such as breast, hepatocellular, renal, and lung carcinomas. © 2012 Wiley Periodicals, Inc.

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