Stains & molecular markers
Nucleophosmin (NPM)

Topic Completed: 1 June 2005

Minor changes: 23 December 2020

Copyright: 2002-2021,, Inc.

PubMed Search: Nucleophosmin [title]

Nat Pernick, M.D.
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Table of Contents
Definition / general
Cite this page: Pernick N. Nucleophosmin (NPM). website. Accessed January 20th, 2021.
Definition / general
  • Also called B23, numatrin; gene at 5q35
  • Highly conserved non-ribosomal nucleolar phosphoprotein involved in assembling preribosomal particles into small and large ribosomal subunits
    • Binds with high affinity to ss nucleic acids, exhibits activity that destabilizes the RNA helix and is associated with the most mature nucleolar preribosomal ribonucleoproteins
  • May contribute active promoter to NPM-ALK
  • ALK promoter is normally silent in lymphoid cells

  • Hypothesis
    • IL-2 or T-cell mediated signals activate substrates; with NPM-ALK, get constitutive activation (note ALCL arises from activated T lymphocytes, which depend on IL-2 for growth and viability)
    • Fusion protein found in anaplastic large cell lymphoma (13-50%)
    • When present, can be used to differentiate from Hodgkin lymphoma
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