BACKGROUND: Imatinib is a tyrosine kinase inhibitor that is used to treat chronic myelogenous leukemia (CML). BCR-ABL mutations are associated with failure of imatinib treatment in many CML patients. LYN kinase regulates survival and responsiveness of CML cells to inhibition of BCR-ABL kinase, and differences in LYN regulation have been found between imatinib-sensitive and -resistant CML cell lines. METHODS: We evaluated cells from 12 imatinib-resistant CML patients with mutation-negative BCR-ABL and from six imatinib-sensitive patients who discontinued therapy because of imatinib intolerance. Phosphorylation of BCR-ABL and LYN was assessed in patient cells and cell lines by immunoblotting with activation state-specific antibodies, co-immunoprecipitation studies, and mass spectroscopy analysis of phosphopeptides. Cell viability, caspase activation, and apoptosis were also measured. Mutations were analyzed by sequencing. The effect of silencing LYN with short interfering RNAs (siRNAs) or reducing activation by treatment with tyrosine kinase inhibitors was evaluated in cell lines and patient cells. RESULTS: Imatinib treatment suppressed LYN phosphorylation in cells from imatinib-sensitive CML patients and imatinib-sensitive cell lines. Imatinib treatment blocked BCR-ABL signaling but did not suppress LYN phosphorylation in cells from imatinib-resistant patients, and persistent activation of LYN kinase was not associated with mutations in LYN kinase or its carboxyl-terminal regulatory domains. Unique LYN phosphorylation sites (tyrosine-193 and tyrosine-459) and associated proteins (c-Cbl and p80) were identified in cells from imatinib-resistant patients. Reducing LYN expression (siRNA) or activation (dasatinib) was associated with loss of cell survival and cytogenetic or complete hematologic responses in imatinib-resistant disease. CONCLUSIONS: LYN activation was independent of BCR-ABL in cells from imatinib-resistant patients. Thus, LYN kinase may be involved in imatinib resistance in CML patients with mutation-negative BCR-ABL and its direct inhibition is consistent with clinical responses in these patients.
BACKGROUND:Imatinib is a tyrosine kinase inhibitor that is used to treat chronic myelogenous leukemia (CML). BCR-ABL mutations are associated with failure of imatinib treatment in many CMLpatients. LYN kinase regulates survival and responsiveness of CML cells to inhibition of BCR-ABL kinase, and differences in LYN regulation have been found between imatinib-sensitive and -resistant CML cell lines. METHODS: We evaluated cells from 12 imatinib-resistant CMLpatients with mutation-negative BCR-ABL and from six imatinib-sensitive patients who discontinued therapy because of imatinib intolerance. Phosphorylation of BCR-ABL and LYN was assessed in patient cells and cell lines by immunoblotting with activation state-specific antibodies, co-immunoprecipitation studies, and mass spectroscopy analysis of phosphopeptides. Cell viability, caspase activation, and apoptosis were also measured. Mutations were analyzed by sequencing. The effect of silencing LYN with short interfering RNAs (siRNAs) or reducing activation by treatment with tyrosine kinase inhibitors was evaluated in cell lines and patient cells. RESULTS:Imatinib treatment suppressed LYN phosphorylation in cells from imatinib-sensitive CMLpatients and imatinib-sensitive cell lines. Imatinib treatment blocked BCR-ABL signaling but did not suppress LYN phosphorylation in cells from imatinib-resistant patients, and persistent activation of LYN kinase was not associated with mutations in LYN kinase or its carboxyl-terminal regulatory domains. Unique LYN phosphorylation sites (tyrosine-193 and tyrosine-459) and associated proteins (c-Cbl and p80) were identified in cells from imatinib-resistant patients. Reducing LYN expression (siRNA) or activation (dasatinib) was associated with loss of cell survival and cytogenetic or complete hematologic responses in imatinib-resistant disease. CONCLUSIONS:LYN activation was independent of BCR-ABL in cells from imatinib-resistant patients. Thus, LYN kinase may be involved in imatinib resistance in CMLpatients with mutation-negative BCR-ABL and its direct inhibition is consistent with clinical responses in these patients.
Authors: Paolo Neviani; Ramasamy Santhanam; Rossana Trotta; Mario Notari; Bradley W Blaser; Shujun Liu; Hsiaoyin Mao; Ji Suk Chang; Annamaria Galietta; Ashwin Uttam; Denis C Roy; Mauro Valtieri; Rebecca Bruner-Klisovic; Michael A Caligiuri; Clara D Bloomfield; Guido Marcucci; Danilo Perrotti Journal: Cancer Cell Date: 2005-11 Impact factor: 31.743
Authors: Michael R Burgess; Brian J Skaggs; Neil P Shah; Francis Y Lee; Charles L Sawyers Journal: Proc Natl Acad Sci U S A Date: 2005-02-10 Impact factor: 11.205
Authors: Thomas O'Hare; Denise K Walters; Eric P Stoffregen; Taiping Jia; Paul W Manley; Jürgen Mestan; Sandra W Cowan-Jacob; Francis Y Lee; Michael C Heinrich; Michael W N Deininger; Brian J Druker Journal: Cancer Res Date: 2005-06-01 Impact factor: 12.701
Authors: Karoline V Gleixner; Irina Sadovnik; Mathias Schneeweiss; Gregor Eisenwort; Konstantin Byrgazov; Gabriele Stefanzl; Daniela Berger; Harald Herrmann; Emir Hadzijusufovic; Thomas Lion; Peter Valent Journal: Leuk Res Date: 2018-12-28 Impact factor: 3.156
Authors: Don L Gibbons; Sabrina Pricl; Paola Posocco; Erik Laurini; Maurizio Fermeglia; Hanshi Sun; Moshe Talpaz; Nicholas Donato; Alfonso Quintás-Cardama Journal: Proc Natl Acad Sci U S A Date: 2014-02-18 Impact factor: 11.205
Authors: Martin C Müller; Jorge E Cortes; Dong-Wook Kim; Brian J Druker; Philipp Erben; Ricardo Pasquini; Susan Branford; Timothy P Hughes; Jerald P Radich; Lynn Ploughman; Jaydip Mukhopadhyay; Andreas Hochhaus Journal: Blood Date: 2009-09-24 Impact factor: 22.113