Implication of the kinase activity and the tyrosine 418 of NPM-ALK in its association with an Src-kinase. Jurkat cells stably expressing wild-type NPM-ALK or mutant forms of NPM-ALK were used to determine the tyrosine residue involved in NPM-ALK/Src-kinase association. Jurkat cells (10⁷) expressing wild-type NPM-ALK (WT), kinase dead NPM-ALK (K210R), or Y418F, Y664F or the double Y156F-Y418F NPM-ALK mutants were subjected to anti-Src immunoprecipitation using the Src-2 antibody followed by immunoblotting using the ALKc antibody. The expression level of NPM-ALK WT, K210R, and Y418F mutants was comparable as well as the expression level of Y664F and Y156F-Y418F mutants (lower panels). Note that NPM-ALK is classically revealed as 2 to 3 distinct bands when expressed in Jurkat cells.¹⁵  Data shown are representative of 2 independent experiments with identical results.