About 40 to 50% of cases diagnosed as ALCL contain a specific chromosomal rearrangement, t(2;5)(p23;q35), resulting in expression of the chimeric tyrosine kinase NPM-ALK.     ///    "We conclude that NPM-ALK is not stimulated by CD30 activation, but exists as a constitutively hyperactivated protein. "    ///    We demonstrate that NPM-ALK specifically binds to the intracellular domain of the cytokine receptor CD30.     ///    "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.. "    ///    Western blot analysis of coimmunoprecipitated CD30 and NPM-ALK proteins from stimulated Karpas 299 cells showed that the interaction of the proteins is not modified by stimulation.     ///    "To better elucidate the function of NPM-ALK, we investigated a possible mechanism for regulation of its activity. "    ///    In vitro binding assays revealed that the ALK portion of NPM-ALK mediates interaction of the two proteins.     ///    "Activation of CD30 neither enhanced NPM-ALK activity measured by autophosphorylation of the chimeric tyrosine kinase nor phosphorylation of phospholipase C-gamma, an NPM-ALK substrate. "    ///    Interaction with CD30 may extend the subcellular localization of NPM-ALK to the microenvironment of membrane-associated proteins.. 