Expression of the ALK tyrosine kinase gene in neuroblastoma

ALK (anaplastic lymphoma kinase) is a tyrosine kinase receptor, expressed a s part of the chimeric NPM-ALK protein, in anaplastic large cell lymphomas (ALCLs) exhibiting. the t(2;5)(p23;q35) translocation, As a result of this translocation, the NPM (nucleophosmin) gene is fused to the portion of the ALK gene encoding its intracytoplasmic segment. In normal mouse tissues, mR NA encoding the Alk receptor has been found only in neural cells, suggestin g. involvement of this receptor in the development of the nervous system. T he purpose of the present study was to examine the presence of ALK transcri pts and protein in normal human tissues and a variety of cell lines and hum an tumors. Emphasis was placed on neuroblastomas because other tyrosine kin ase receptors are expressed in human neuroblastomas. Fifty-six cell lines, including 29 lines of neural origin, and lymphoid and nonlymphoid tissue sp ecimens, including 24 neuroblastomas, were investigated for ALK expression, using reverse transcriptase-polymerase chain reaction, Western blotting, a nd immunohistochemistry, The results confirmed that mRNA encoding AWK prote in was not detectable in any normal or neoplastic hematopoietic tissue test ed, except for t(2; 5)-positive ALCL, The salient finding was that 13 of th e 29 cell lines of neural origin and 22 of 24 neuroblastomas were found to express ALK transcripts and ALK protein. However, no correlation was eviden t between any known prognostic factors and the level of ALK expression.