Effects of nilotinib on regulatory T cells: the dose matters.
BACKGROUND
Nilotinib is a tyrosine kinase inhibitor with high target specificity. Here, we characterized the effects of nilotinib for the first time on CD4+CD25+ regulatory T cells (Tregs) which regulate anti-tumor/leukemia immune responses.


METHODS
Carboxyfluorescein diacetate succinimidyl ester (CFSE) and 5-bromo-2-deoxy -uridine (BrdU) were used to assess the proliferation and cell cycle distribution of Tregs. The expression of the transcription factor forkhead box P3 (FoxP3) and the glucocorticoid-induced tumor necrosis factor receptor (GITR) were measured by flow cytometry. Western blotting analysis was used to detect the effects of nilotinib on the signal transduction cascade of T-cell receptor (TCR) in Tregs.


RESULTS
Nilotinib inhibited the proliferation and suppressive capacity of Tregs in a dose-dependent manner. However, the production of cytokines secreted by Tregs and CD4+CD25- T cells was only inhibited at high concentrations of nilotinib exceeding the mean therapeutic serum concentrations of the drug in patients. Only high doses of nilotinib arrested both Tregs and CD4+CD25- T cells in the G0/G1 phase and down-regulated the expression of FoxP3 and GITR. In western blotting analysis, nilotinib did not show significant inhibitory effects on TCR signaling events in Tregs and CD4+CD25- T cells.


CONCLUSIONS
These findings indicate that nilotinib does not hamper the function of Tregs at clinical relevant doses, while long-term administration of nilotinib still needs to be investigated.
Fei
Fei
F
Department of Internal Medicine III, University of Ulm, 89081 Ulm, Germany.
Yu
Yingzhe
Y
Schmitt
Anita
A
Rojewski
Markus T
MT
Chen
Baoan
B
Greiner
Jochen
J
Götz
Marlies
M
Bunjes
Donald
D
Schmitt
Michael
M
D017209:Apoptosis / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D016207:Cytokines / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects; D051858:Forkhead Transcription Factors / Q000378:metabolism; D016193:G1 Phase / Q000187:drug effects; D053450:Glucocorticoid-Induced TNFR-Related Protein; D006801:Humans; D007165:Immunosuppression Therapy; D053645:Interleukin-2 Receptor alpha Subunit / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology*; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism; D017475:Receptors, Nerve Growth Factor / Q000378:metabolism; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism; D016192:Resting Phase, Cell Cycle / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D050378:T-Lymphocytes, Regulatory / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism
D016207:Cytokines; C418974:FOXP3 protein, human; D051858:Forkhead Transcription Factors; D053450:Glucocorticoid-Induced TNFR-Related Protein; D053645:Interleukin-2 Receptor alpha Subunit; D011743:Pyrimidines; D011948:Receptors, Antigen, T-Cell; D017475:Receptors, Nerve Growth Factor; D018124:Receptors, Tumor Necrosis Factor; C491405:TNFRSF18 protein, human; C498826:nilotinib