CD8+ T cells against multiple tumor-associated antigens in peripheral blood of midgut carcinoid patients.
OBJECTIVE
The aim of the study was to identify immunogenic HLA-A*0201-binding epitopes derived from a number of classical midgut carcinoid-associated proteins. CD8(+) T cells recognizing tumor-associated antigen (TAA) epitopes are of great interest for the establishment of immunotherapy as a novel treatment for this type of malignancy.


METHODS
Midgut carcinoid tumor specimens were microdissected and expression levels of potential TAAs were investigated by quantitative real time PCR. HLA-A*0201-binding motifs were selected using HLA peptide binding prediction algorithms and stabilization of HLA-A*0201 was verified using TAP-deficient T2 cells. Peripheral blood of midgut carcinoid patients was analyzed for peptide epitope recognition and the feasibility of generating peptide-reactive CD8(+) T cells in healthy blood donors was examined by an in vitro stimulation protocol using mature DCs. Activation of patient and healthy donor CD8(+) T cells was analyzed by intracellular flow cytometry staining of interferon gamma.


RESULTS
Chromogranin A (CGA), tryptophan hydroxylase 1 (TPH-1), vesicular monoamine transporter 1 (VMAT-1), caudal type homeobox transcription factor 2 (CDX-2), and islet autoantigen 2 (IA-2) are properly expressed by midgut carcinoid tumor cells, with CGA mRNA expressed to greatest level. Midgut carcinoid patients have increased frequencies of peripheral blood CD8(+) T cells recognizing a pool of HLA-A*0201 peptides derived from these proteins compared to healthy age-matched individuals. Activated peptide-specific CD8(+) T cells could also be generated in healthy blood donors by in vitro stimulation.


CONCLUSIONS
We have identified a number of immunogenic midgut carcinoid-associated peptide epitopes recognized by CD8(+) T cells. We show that midgut carcinoid patients display immune recognition of their tumors. Memory CD8(+) T cells in patient blood are of great interest when pursuing an immunotherapeutic treatment strategy.
Vikman
Sofia
S
Division of Clinical Immunology, Rudbeck Laboratory, Uppsala University, Uppsala, Sweden. Sofia.Vikman@klinimm.uu.se
Giandomenico
Valeria
V
Sommaggio
Roberta
R
Oberg
Kjell
K
Essand
Magnus
M
Tötterman
Thomas H
TH
D000465:Algorithms; D020816:Amino Acid Motifs / Q000276:immunology; D000951:Antigens, Neoplasm / Q000235:genetics / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D002276:Carcinoid Tumor / Q000235:genetics / Q000276:immunology*; D002460:Cell Line; D019295:Computational Biology; D018604:Epitope Mapping / Q000379:methods; D018984:Epitopes, T-Lymphocyte / Q000097:blood / Q000235:genetics / Q000276:immunology; D005434:Flow Cytometry; D015234:HLA-A Antigens / Q000097:blood / Q000235:genetics / Q000276:immunology; D015789:HLA-A2 Antigen; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism; D008969:Molecular Sequence Data; D010455:Peptides / Q000097:blood / Q000737:chemistry / Q000276:immunology; D012333:RNA, Messenger / Q000235:genetics / Q000276:immunology; D020133:Reverse Transcriptase Polymerase Chain Reaction
D000951:Antigens, Neoplasm; D018984:Epitopes, T-Lymphocyte; D015234:HLA-A Antigens; C435939:HLA-A*02:01 antigen; D015789:HLA-A2 Antigen; D010455:Peptides; D012333:RNA, Messenger; D007371:Interferon-gamma
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