Detection and functional analysis of CD8+ T cells specific for PRAME: a target for T-cell therapy
Marieke Griffioen1, Jan H Kessler, Martina Borghi
1Department of Clinical Oncology, Leiden University Medical Center, Leiden, Netherlands. M.Griffioen@lumc.nl
Purpose:
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.
Experimental Design:
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.
Conclusion:
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.
Insights
Preferentially expressed antigen on melanomas (PRAME) is a promising target for T-cell therapy. Researchers found PRAME-specific T cells recognize and kill PRAME-positive melanoma cells, supporting its therapeutic potential.
Area of Science:
- Immunology
- Oncology
- Cancer immunotherapy
Background:
- Preferentially expressed antigen on melanomas (PRAME) is highly expressed in 95% of melanomas and other cancers.
- PRAME's role in oncogenic transformation suggests resistance to T-cell mediated escape.
- PRAME is a potential target for developing novel anticancer T-cell therapies.
Purpose of the Study:
- To evaluate the therapeutic potential of PRAME as a target for anticancer T-cell therapies.
- To investigate the presence and function of PRAME-specific T cells in melanoma patients and healthy individuals.
Main Methods:
- Screening of HLA-A*0201-positive individuals for PRAME-specific CD8+ T cells using IFN-gamma ELISPOT and tetramer staining.
- Isolation and characterization of PRAME-specific T-cell clones.
- Assessment of melanoma and acute lymphoid leukemia (ALL) cell line recognition by T-cell clones.
- Quantification of PRAME mRNA expression via real-time RT-PCR.
Main Results:
- PRAME(100-108)-specific CD8+ T cells were detected in 30-40% of individuals, with a predominantly naive phenotype.
- Isolated T-cell clones recognized and lysed HLA-A*0201-positive, PRAME-expressing melanoma cell lines.
- PRAME expression was significantly lower in ALL cell lines compared to melanoma, below the T-cell recognition threshold.
Conclusions:
- The study supports PRAME, specifically the PRAME(100-108) epitope, as a viable target for T-cell therapy.
- PRAME-targeted T-cell therapy shows promise for PRAME-overexpressing cancers like melanoma.
- Further development of PRAME-specific T-cell therapies is warranted.
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