EXPRESSION OF THE X-LINKED AGAMMAGLOBULINEMIA GENE, BTK IN B-CELL ACUTE LYMPHOBLASTIC-LEUKEMIA

The gene which causes X-linked agammaglobulinemia, btk, has recently b een identified as a cytoplasmic tyrosine kinase expressed almost exclu sively in B cells, and at all stages of B-cell differentiation. To ass ess the possibility of involvement of this gene in childhood B-cell ma lignancies, cells from 23 pediatric patients with B-cell acute lymphob lastic leukemia were examined for expression and alteration of the Btk protein and also for mutations in the btk gene. Btk proteins, similar in both molecular weight and quantity to those seen in unaffected ind ividuals, were detected in whole cell lysates from the blasts of 12/12 patients indicating that no abnormal protein was present. cDNAs from the leukemic blasts of all 23 patients were screened with specific pri mers covering the coding region of the btk cDNA for mutations using si ngle strand conformation polymorphism (SSCP) analysis. No mutations we re found but a nucleotide polymorphism was identified in 4/23 patients at the 3' end of btk. Although the sample size in this study was rela tively small, these data suggest that btk does not appear to play a cr itical role in childhood 8-cell leukemias.