Detection and functional analysis of CD8+ T cells specific for PRAME: a target for T-cell therapy.
OBJECTIVE
Preferentially expressed antigen on melanomas (PRAME) is an interesting antigen for T-cell therapy because it is frequently expressed in melanomas (95%) and other tumor types. Moreover, due to its role in oncogenic transformation, PRAME-negative tumor cells are not expected to easily arise and escape from T-cell immunity. The purpose of this study is to investigate the usefulness of PRAME as target for anticancer T-cell therapies.


METHODS
HLA-A*0201-subtyped healthy individuals and advanced melanoma patients were screened for CD8+ T cells directed against previously identified HLA-A*0201-binding PRAME peptides by IFN-gamma enzyme-linked immunosorbent spot assays and tetramer staining. PRAME-specific T-cell clones were isolated and tested for recognition of melanoma and acute lymphoid leukemia (ALL) cell lines. PRAME mRNA expression was determined by quantitative real-time reverse transcription-PCR.


RESULTS
In 30% to 40% of healthy individuals and patients, PRA(100-108)-specific CD8+ T cells were detected both after in vitro stimulation and directly ex vivo after isolation by magnetic microbeads. Although CD45RA- memory PRA(100-108)-specific T cells were found in some individuals, the majority of PRA(100-108)-tetramer+ T cells expressed CD45RA, suggesting a naive phenotype. PRA(100-108)-tetramer+ T-cell clones were shown to recognize and lyse HLA-A*0201+ and PRAME+ melanoma but not ALL cell lines. Quantitative real-time reverse transcription-PCR showed significantly lower PRAME mRNA levels in ALL than in melanoma cell lines, suggesting that PRAME expression in ALL is below the recognition threshold of our PRA(100-108)-tetramer+ T cells.


CONCLUSIONS
These data support the usefulness of PRAME and in particular the PRA(100-108) epitope as target for T-cell therapy of PRAME-overexpressing cancers.
Griffioen
Marieke
M
Department of Clinical Oncology, Leiden University Medical Center, Leiden, Netherlands. M.Griffioen@lumc.nl
Kessler
Jan H
JH
Borghi
Martina
M
van Soest
Ronald A
RA
van der Minne
Caroline E
CE
Nouta
Jan
J
van der Burg
Sjoerd H
SH
Medema
Jan Paul
JP
Schrier
Peter I
PI
Falkenburg
J H Frederik
JH
Osanto
Susanne
S
Melief
Cornelis J M
CJ
D000951:Antigens, Neoplasm / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes; D015234:HLA-A Antigens / Q000276:immunology; D015789:HLA-A2 Antigen; D006801:Humans; D007167:Immunotherapy / Q000379:methods; D008545:Melanoma / Q000276:immunology* / Q000628:therapy; D012878:Skin Neoplasms / Q000276:immunology* / Q000628:therapy; D014407:Tumor Cells, Cultured
D000951:Antigens, Neoplasm; D000939:Epitopes; D015234:HLA-A Antigens; C435939:HLA-A*02:01 antigen; D015789:HLA-A2 Antigen; C404944:PRAME protein, human