Comparative gene expression profile of chronic myeloid leukemia cells innately resistant to imatinib mesylate.
OBJECTIVE
Resistance to imatinib mesylate monotherapy is clearly a barrier to successful treatment of chronic myeloid leukemia (CML) patients. In some patients, resistance arises due to powerful selective pressure on rare cells that carry amplified copies of the BCR-ABL fusion oncogene or point mutations in the Bcr-Abl tyrosine kinase domain that affect binding of the drug to the oncoprotein. However, in a proportion of patients neither mechanism operates, and resistance appears to be a priori, existing prior to exposure to the drug. These mechanisms of imatinib resistance are poorly understood and may be heterogeneous.


METHODS
We have previously described such innate resistance to imatinib in subclones of a myeloid leukemia cell line, KCL22, in which imatinib exposure inhibits the activity of Bcr-Abl and yet fails to induce apoptosis. We describe here whole-genome expression analysis of imatinib-sensitive and -resistant cells derived from the original KCL22 line, using Affymetrix microarray analysis.


RESULTS
We detected differential expression of 39 genes that correlate with the imatinib-resistant phenotype. The resistant cells overexpress several genes associated with the suppression of apoptosis or with conferral of a transformed phenotype.


CONCLUSIONS
Amongst the differentially-expressed genes correlating with imatinib resistance, several suggest the activation of alternative pathway(s) that maintain viability and growth independently of Bcr-Abl kinase activity. Given the high rate of primary imatinib resistance in blast crisis, the potential of activating such alternative pathways appears to correlate with disease progression.
Department of Haematology, Imperial College London, Hammersmith Hospital, London, UK.
Alex J
AJ
Tipping
Michael W
MW
Deininger
John M
JM
Goldman
Junia V
JV
Melo
D000970:Antineoplastic Agents / Q000627:therapeutic use*; D001549:Benzamides; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D000068877:Imatinib Mesylate; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy* / Q000235:genetics; D010879:Piperazines / Q000627:therapeutic use*; D011743:Pyrimidines / Q000627:therapeutic use*
D000970:Antineoplastic Agents; D001549:Benzamides; D010879:Piperazines; D011743:Pyrimidines; D000068877:Imatinib Mesylate