Establishment and characterization of a novel imatinib-sensitive chronic myeloid leukemia cell line MYL, and an imatinib-resistant subline MYL-R showing overexpression of Lyn.
In chronic myeloid leukemia (CML), resistance to imatinib is diverse. In addition to BCR-ABL-dependent mechanisms, BCR-ABL-independent mechanisms have been proposed. Here we established and characterized novel CML cell lines, an imatinib-sensitive cell line, MYL, and an imatinib-resistant subline, MYL-R. Treatment with imatinib inhibited phosphorylation of BCR-ABL and CrkL in both MYL and MYL-R, even though imatinib-induced apoptosis was preferentially observed in MYL than MYL-R, indicating that the resistance is based on a BCR-ABL-independent mechanism. MYL-R showed elevated expressions of Lyn mRNA, Lyn protein, phosphorylated Lyn, and phosphorylated STAT5. Silencing of Lyn by short-interfering RNA (siRNA) in MYL-R, but not in MYL, induced significant growth-inhibition, increased caspase-3 activity, and induced partial recovery from imatinib-resistance. Expression of Bcl-2, previously reported to be associated with Lyn-mediated resistance, was not elevated in MYL-R. Expression of Bim, which plays an important role in imatinib-induced cell-killing, was not suppressed in MYL-R. These results imply that diverse mechanisms of resistance exist among cell types. Treatment of MYL-R cells with various reagents known to have anti-leukemic activity revealed that zoledronic acid and the farnesyl transferase inhibitor (SCH 66336) showed strong synergism with imatinib; interferon alpha, PP2, CGP76030, and FK228 (depsipeptide) showed synergism; whereas soluble TRAIL and As2O3 showed additivity or antagonism, and 17-AAG and radicicol showed antagonism. Treatment with either PP2 or zoledronic acid induced greater growth-reduction in MYL-R than MYL. Taken together, Lyn may play an important role in imatinib-resistance in MYL-R. Some novel reagents, including siRNA targeting Lyn, may have good potential to overcome this resistance.
Ito
Takuo
T
Department of Hematology and Oncology, Division of Clinical and Experimental Oncology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima, Japan.
Tanaka
Hideo
H
Kimura
Akiro
A
D000328:Adult; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D001483:Base Sequence; D001549:Benzamides; D045744:Cell Line, Tumor; D017931:DNA Primers; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D005260:Female; D016313:Genes, abl; D006801:Humans; D000068877:Imatinib Mesylate; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000473:pathology*; D020411:Oligonucleotide Array Sequence Analysis; D010766:Phosphorylation; D010879:Piperazines / Q000494:pharmacology*; D011743:Pyrimidines / Q000494:pharmacology*; D034741:RNA, Small Interfering; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019061:src-Family Kinases / Q000235:genetics*
D000970:Antineoplastic Agents; D001549:Benzamides; D017931:DNA Primers; D010879:Piperazines; D011743:Pyrimidines; D034741:RNA, Small Interfering; D000068877:Imatinib Mesylate; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases