title: Imatinib mesylate and nilotinib affect MHC-class I presentation by modulating the proteasomal processing of antigenic peptides.
abstract: Imatinib (IM) has been described to modulate the function of dendritic cells and T lymphocytes and to affect the expression of antigen in CML cells. In our study, we investigated the effect of the tyrosine kinase inhibitors IM and nilotinib (NI) on antigen presentation and processing by analyzing the proteasomal activity in CML cell lines and patient samples. We used a biotinylated active site-directed probe, which covalently binds to the proteasomally active beta-subunits in an activity-dependent fashion. Additionally, we analyzed the cleavage and processing of HLA-A3/11- and HLA-B8-binding peptides derived from BCR-ABL by IM- or NI-treated isolated 20S immunoproteasomes using mass spectrometry. We found that IM treatment leads to a reduction in MHC-class I expression which is in line with the inhibition of proteasomal activity. This process is independent of BCR-ABL or apoptosis induction. In vitro digestion experiments using purified proteasomes showed that generation of epitope-precursor peptides was significantly altered in the presence of NI and IM. Treatment of the immunoproteasome with these compounds resulted in an almost complete reduction in the generation of long precursor peptides for the HLA-A3/A11 and -B8 epitopes while processing of the short peptide sequences increased. Treatment of isolated 20S proteasomes with serine-/threonine- and tyrosine-specific phosphatases induced a significant downregulation of the proteasomal activity further indicating that phosphorylation of the proteasome regulates its function and antigen processing. Our results demonstrate that IM and NI can affect the immunogenicity of malignant cells by modulating proteasomal degradation and the repertoire of processed T cell epitopes.
authors.affiliation: Department of Hematology and Oncology, University Hospital Bonn, Bonn, Germany. stefanie.held@ukb.uni-bonn.de
authors.forename: Stefanie Andrea Erika
authors.initials: SA
authors.lastname: Held
authors.forename: Katharina Maria
authors.initials: KM
authors.lastname: Duchardt
authors.forename: Stefan
authors.initials: S
authors.lastname: Tenzer
authors.forename: Thomas
authors.initials: T
authors.lastname: Rückrich
authors.forename: Karin
authors.initials: K
authors.lastname: von Schwarzenberg
authors.forename: Anita
authors.initials: A
authors.lastname: Bringmann
authors.forename: Christian
authors.initials: C
authors.lastname: Kurts
authors.forename: Hansjörg
authors.initials: H
authors.lastname: Schild
authors.forename: Christoph
authors.initials: C
authors.lastname: Driessen
authors.forename: Peter
authors.initials: P
authors.lastname: Brossart
authors.forename: Annkristin
authors.initials: A
authors.lastname: Heine
mesh_terms: D000595:Amino Acid Sequence; D017951:Antigen Presentation / Q000187:drug effects; D000951:Antigens, Neoplasm / Q000276:immunology* / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology; D001549:Benzamides / Q000494:pharmacology*; D016044:Fusion Proteins, bcr-abl / Q000378:metabolism; D015234:HLA-A Antigens / Q000276:immunology; D015235:HLA-B Antigens / Q000276:immunology; D015395:Histocompatibility Antigens Class I / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D000068877:Imatinib Mesylate; D020014:K562 Cells; D007938:Leukemia / Q000276:immunology; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000276:immunology* / Q000378:metabolism; D010879:Piperazines / Q000494:pharmacology*; D046988:Proteasome Endopeptidase Complex / Q000276:immunology* / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D054648:Protein Phosphatase 2 / Q000276:immunology / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology*
chemical_list: D000951:Antigens, Neoplasm; D000970:Antineoplastic Agents; D001549:Benzamides; D015234:HLA-A Antigens; D015235:HLA-B Antigens; D015395:Histocompatibility Antigens Class I; D010446:Peptide Fragments; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; D000068877:Imatinib Mesylate; D016044:Fusion Proteins, bcr-abl; D054648:Protein Phosphatase 2; D046988:Proteasome Endopeptidase Complex; C498826:nilotinib