Deregulation of DNA mismatch repair by the oncogenic tyrosine kinase NPM-ALK

  • Author / Creator
    Bone, Kathleen M
  • The vast majority of anaplastic lymphoma kinase positive anaplastic large cell lymphoma (ALK+ALCL) tumors carry the genetic translocation t(2;5)(p23;q35), leading to production of the constitutively active fusion tyrosine kinase NPM-ALK. NPM-ALK expression and its potent transformative properties are central to the pathogenesis of this disease. The Lai Laboratory recently identified MSH2, an integral component of the DNA mismatch repair (MMR) pathway, as a novel NPM-ALK interactor by mass spectrometry. DNA MMR proteins aid in tumor suppression through the maintenance of genomic instability, and their loss is highly oncogenic. As NPM-ALK is a tyrosine kinase that binds to and phosphorylates downstream proteins to mediate its tumorigenesis, it was hypothesized that through its interaction with MSH2, NPM-ALK interferes with its biological function, impacting MMR. The major findings of this study are that NPM-ALK indeed binds and tyrosine phosphorylates MSH2, blocking the interaction with its main MMR binding partner, MSH6, and inducing cytoplasmic retention of MSH2 in the presence of DNA damage. Correlating with these findings, ALK+ALCL patient samples displayed evidence of MMR dysfunction, including accentuated MSH2 cytoplasmic staining, and microsatellite instability. Furthermore, tyrosine 238 in the MSH2 protein was identified as the key NPM-ALK-induced tyrosine phosphorylation site in the context of MMR deregulation; overexpression of a non-phosphorylatable mutant, MSH2Y238F, in NPM-ALK expressing cell lines reversed MSH2 tyrosine phosphorylation, and restored the interaction of MSH2 and MSH6, resulting in a return of MMR function. Finally, using a novel antibody specifically designed against phosphorylated MSH2 at tyrosine 238, other clinically relevant oncogenic tyrosine kinases were found to interact with MSH2, inducing its phosphorylation at tyrosine 238, leading to MMR dysfunction. This is the first reported evidence of post-translational modification of MSH2 at a specific residue, tyrosine 238, by oncogenic tyrosine kinases with a direct impact on MMR function. Altogether, this study provides novel insights into the deregulation of DNA repair by oncogenic tyrosine kinases, with widespread implications for tyrosine kinase screening and targeted cancer therapy.

  • Subjects / Keywords
  • Graduation date
    Fall 2014
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
  • Language
  • Institution
    University of Alberta
  • Degree level
  • Department
  • Supervisor / co-supervisor and their department(s)
  • Examining committee members and their departments
    • Andrew, Susan (Medical Genetics)
    • Murray, David (Oncology)
    • Fu, Yangxin (Oncology)
    • Keelan, Monika (Laboratory Medicine and Pathology)
    • Jirik, Frank (Biochemistry and Molecular Biology)