Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 108, Issue 29, Pages 11977-11982Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1100319108
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Funding
- National Cancer Institute [R01-CA89194, R01-CA96856]
- Leukemia and Lymphoma Society
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Anaplastic lymphoma kinase (ALK), physiologically expressed only by certain neural cells, becomes highly oncogenic, when aberrantly expressed in nonneural tissues as a fusion protein with nucleophosphin (NPM) and other partners. The reason why NPM-ALK succeeds in transforming specifically CD4(+) T lymphocytes remains unknown. The IL-2R common gamma-chain (IL-2R gamma) is shared by receptors for several cytokines that play key roles in the maturation and growth of normal CD4(+) T lymphocytes and other immune cells. We show that IL-2R gamma expression is inhibited in T-cell lymphoma cells expressing NPM-ALK kinase as a result of DNA methylation of the IL-2R gamma gene promoter. IL-2R gamma promoter methylation is induced in malignant T cells by NPM-ALK. NPM-ALK acts through STAT3, a transcription factor that binds to the IL-2R gamma gene promoter and enhances binding of DNA methyltransferases (DNMTs) to the promoter. In addition, STAT3 suppresses expression of miR-21, which selectively inhibits DNMT1 mRNA expression. Reconstitution of IL-2R gamma expression leads to loss of the NPM-ALK protein and, consequently, apoptotic cell death of the lymphoma cells. These results demonstrate that the oncogenic tyrosine kinase NPM-ALK induces epigenetic silencing of the IL-2R gamma gene and that IL-2R gamma acts as a tumor suppressor by reciprocally inhibiting expression of NPM-ALK.
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