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Imatinib mesylate inhibits CD4+ CD25+ regulatory T cell activity and enhances active immunotherapy against BCR-ABL- tumors.

ABSTRACT: Imatinib mesylate (Gleevec, STI571), a selective inhibitor of a restricted number of tyrosine kinases, has been effectively used for the treatment of Philadelphia chromosome-positive leukemias and gastrointestinal stromal tumors. Imatinib may also directly influence immune cells. Suppressive as well as stimulating effects of this drug on CD4(+) and CD8(+) T lymphocytes or dendritic cells have been reported. In the current study, we have investigated the influence of imatinib mesylate on CD4(+)CD25(+)FoxP3(+) regulatory T cells (Treg), a critical population of lymphocytes that contributes to peripheral tolerance. Used at concentrations achieved clinically, imatinib impaired Treg immunosuppressive function and FoxP3 expression but not production of IL-10 and TGF-beta in vitro. Imatinib significantly reduced the activation of the transcription factors STAT3 and STAT5 in Treg. Analysis of Treg TCR-induced signaling cascade indicated that imatinib inhibited phosphorylation of ZAP70 and LAT. Substantiating these observations, imatinib treatment of mice decreased Treg frequency and impaired their immunosuppressive function in vivo. Furthermore, imatinib mesylate significantly enhanced antitumor immune responses to dendritic cell-based immunization against an imatinib-resistant BCR-ABL negative lymphoma. The clinical applications of imatinib mesylate might thus be expanded with its use as a potent immunomodulatory agent targeting Treg in cancer immunotherapy.

SUBMITTER: Larmonier N

PROVIDER: S-EPMC2579962 | biostudies-literature | 2008 Nov

REPOSITORIES: biostudies-literature

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Imatinib mesylate inhibits CD4+ CD25+ regulatory T cell activity and enhances active immunotherapy against BCR-ABL- tumors.

Larmonier Nicolas N Janikashvili Nona N LaCasse Collin James CJ Larmonier Claire Billerey CB Cantrell Jessica J Situ Elaine E Lundeen Tamara T Bonnotte Bernard B Katsanis Emmanuel E

Journal of immunology (Baltimore, Md. : 1950) 20081101 10

Imatinib mesylate (Gleevec, STI571), a selective inhibitor of a restricted number of tyrosine kinases, has been effectively used for the treatment of Philadelphia chromosome-positive leukemias and gastrointestinal stromal tumors. Imatinib may also directly influence immune cells. Suppressive as well as stimulating effects of this drug on CD4(+) and CD8(+) T lymphocytes or dendritic cells have been reported. In the current study, we have investigated the influence of imatinib mesylate on CD4(+)CD ...[more]

PMID: 18981115

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Project description:Imatinib mesylate is a tyrosine kinase inhibitor that was approved by the U.S. Food and Drug Administration in 2001 for treatment of many different stages of chronic myeloid leukemia and in 2002 for treatment of gastrointestinal stromal tumors. Imatinib is known to inhibit the dysregulated proliferation of chronic myeloid leukemia, which is associated with the Bcr-Abl kinase; in gastrointestinal stromal tumors, imatinib is known to act via c-Kit kinase inhibition. The objective of this study was to synthesize an (18)F-labeled analog of imatinib not as a primary imaging agent but rather as a tracer for in vivo drug distribution and tracer concentration that can be used as a PET imaging surrogate for imatinib.Molecular modeling studies based on the crystal structure of imatinib bound to the active site of Abl were performed for designing the fluorinated analog. A 2-fluoroethyl analog of imatinib (SKI696) was synthesized using well-established procedures. The selectivity and binding affinity of SKI696 were compared with those of imatinib in vitro. Mice bearing K562 tumor xenografts, which are known to overexpress Bcr-Abl, were imaged with (18)F-SKI696 PET. A biodistribution study was also performed on K562 tumor-bearing mice to which our radiolabeled tracer was administered.The kinase assay verified that imatinib and SKI696 bind to the same targets with similar affinities. The feasibility of using (18)F-SKI696 as a PET agent was examined in vivo, and (18)F-SKI696 PET was shown to visualize K562 tumor xenografts in nude mice. The tumor was visible on PET 1 h after injection, with uptake of 1% of the injected dose. Biodistribution studies in K562-bearing mice were also performed, and the uptake of (18)F-SKI696 (percentage injected dose per gram) for each organ was calculated.The results of the binding assay showed that SKI696 has selectivity and binding affinity comparable to imatinib. Small-animal PET of K562 tumor-bearing mice using (18)F-SKI696 as a PET agent displayed promising tumor uptake and tumor-to-nontarget contrast. Because (18)F-SKI696 has been taken up in vivo by tumors that overexpress Bcr-Abl, we are exploring a possible role for identifying tumors that will respond to imatinib before therapy.

Project description:BackgroundWith the widespread clinical application of tyrosine kinase inhibitors (TKIs), an increasing number of chronic myeloid leukaemia (CML) patients have developed resistance or intolerance to TKIs. BCR/ABL is the oncoprotein of CML. HSP90 is an essential chaperone of BCR/ABL and plays an important role in protein folding and the function of BCR/ABL. Therefore, inhibiting the chaperone function of HSP90 may be an effective strategy for CML treatment and to overcome TKI resistance.MethodsThe effect of KW-2478 on CML cell viability, apoptosis and cell cycle progression was detected by CCK-8 assay or flow cytometry. The levels of BCR/ABL, HSP90 and other signalling proteins were detected by western blots. The mitochondrial membrane potential was detected by flow cytometry combined with JC-1 staining. The interaction between BCR/ABL and HSP90α was detected by coimmunoprecipitation. The effect of KW-2478 on BCR/ABL carcinogenesis in vivo was investigated in CML-like mouse models.ResultsKW-2478 inhibited growth and induced apoptosis of CML cells. KW-2478 inhibited the chaperone function of HSP90α and then weakened the BCR/ABL and MAPK signalling pathways. This treatment also caused an increase in p27 and p21 expression and a decrease in cyclin B1 expression, which led to G2/M phase arrest. The mitochondrial pathway was primarily responsible for KW-2478-induced apoptosis. KW-2478 had a synergistic effect with imatinib in growth inhibition. Notably, KW-2478 had a stronger effect on growth inhibition, apoptosis induction and cell cycle arrest of K562/G01 cells than K562 cells. KW-2478 could effectively prolong the mouse lifespan and alleviate disease symptoms in CML-like mouse models.ConclusionsThis finding demonstrated that KW-2478 had anticancer properties in imatinib-sensitive and imatinib-resistant CML cells and illustrated the possible mechanisms. This study provides an alternative choice for CML treatment, especially for TKI-resistant patients with BCR/ABL amplification and TKI-intolerant patients.

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Imatinib mesylate inhibits CD4+ CD25+ regulatory T cell activity and enhances active immunotherapy against BCR-ABL- tumors.

Publications

Imatinib mesylate inhibits CD4+ CD25+ regulatory T cell activity and enhances active immunotherapy against BCR-ABL- tumors.

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