Published online before print February 14, 2008

This Article Full Text Full Text (PDF) All Versions of this Article: jmoldx.2008.070128v1 10/2/177    most recent Purchase Article View Shopping Cart Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Laudadio, J. Articles by Press, R. D. PubMed PubMed Citation Articles by Laudadio, J. Articles by Press, R. D.

Journal of Molecular Diagnostics 2008, Vol. 10, No. 2
Copyright © 2008 American Society for Investigative Pathology & Association for Molecular Pathology
DOI: 10.2353/jmoldx.2008.070128

Consultations in Molecular Diagnostics

An Intron-Derived Insertion/Truncation Mutation in the BCR-ABL Kinase Domain in Chronic Myeloid Leukemia Patients Undergoing Kinase Inhibitor Therapy

Jennifer Laudadio^*, Michael W.N. Deininger, Michael J. Mauro, Brian J. Druker and Richard D. Press^*

From the Department of Pathology, * Center for Hematologic Malignancies, Cancer Institute, and Howard Hughes Medical Institute, Oregon Health & Science University, Portland, Oregon

Abstract

Although targeted inhibition of BCR-ABL with imatinib is an effective therapy for patients with chronic myeloid leukemia (CML), a minority of patients acquire mutations in the BCR-ABL kinase domain, resulting in imatinib resistance. The spectrum of kinase domain mutations discovered to date is quite heterogeneous, consisting almost exclusively of single nucleotide substitutions affecting key amino acids that regulate drug binding or BCR-ABL function. Here, we describe an alternative kinase domain insertion/truncation mutation in three CML patients undergoing kinase inhibitor therapy. In each of these patients, direct DNA sequencing of BCR-ABL RT-PCR products revealed that the same 35 nucleotides from ABL intron 8 had been inserted at the normal exon 8 to 9 splice junction. This 35-bp intronic sequence was flanked by excellent consensus splice donor and acceptor sequences, suggesting alternative splicing as the likely mutational mechanism. The insertion created a premature translational stop codon after 10 intron-encoded amino acids (amino acid 484). This resulted in truncation of 653 C-terminal amino acids, which included part of the kinase domain and the entire "last exon" region. These findings demonstrate that kinase domain insertions are an alternative (and not entirely uncommon) mutational mechanism in CML patients undergoing kinase inhibitor therapy.