The tyrosine kinase NPM-ALK, associated with anaplastic large cell lymphoma, binds the intracellular domain of the surface receptor CD30 but is not activated by CD30 stimulation

The heterogenous group of anaplastic large cell lymphomas (ALCLs) is charac terized by expression of the Ki-1/CD30 antigen, a member of the tumor necro sis factor receptor superfamily. About 40 to 50% of cases diagnosed as ALCL contain a specific chromosomal rearrangement, t(2;5)(p23;q35), resulting i n expression of the chimeric tyrosine kinase NPM-ALK. As NPM-ALK-positive l ymphomas define a distinct subtype within the group of ALCL, the chimeric p rotein might be responsible for certain pathogenetic and clinicopathologic characteristics. To better elucidate the function of NPM-ALK, we investigat ed a possible mechanism for regulation of its activity. We demonstrate that NPM-ALK specifically binds to the intracellular domain of the cytokine rec eptor CD30. In vitro binding assays revealed that the ALK portion of NPM-AL K mediates interaction of the two proteins. Stimulation of the CD30 recepto r by cross-linking with immobilized anti-CD30 antibody results in complete growth inhibition of Karpas 299, an NPM-ALK-positive ALCL cell line, but do es not alter proliferation of HDLM-2, a Hodgkin's lymphoma-derived cell lin e lacking t(2;5). Western blot analysis of coimmunoprecipitated CD30 and NP M-ALK proteins from stimulated Karpas 299 cells shelved that the interactio n of the proteins is not modified by stimulation. Activation of CD30 neithe r enhanced NPM-ALK activity measured by autophosphorylation of the chimeric tyrosine kinase nor phosphorylation of phospholipase C-gamma, an NPM-ALK s ubstrate. We conclude that NPM-ALK is not stimulated by CD30 activation, bu t exists as a constitutively hyperactivated protein. interaction with CD30 may extend the subcellular localization of NPM-ALK to the microenvironment of membrane-associated proteins. (C) 1999 International Society for Experim ental Hematology. Published by Elsevier Science Inc.