MDM2 is recognized as a tumor-associated antigen in chronic lymphocytic leukemia by CD8+ autologous T lymphocytes.
OBJECTIVE
Tumor-associated antigens (TAA) are the basis for antigen-specific immunotherapy. The human homolog of the murine double-minute 2 oncoprotein (MDM2) is a putative TAA because it is overexpressed in several malignancies, including chronic lymphocytic leukemia (CLL) cells compared with normal B lymphocytes.


METHODS
Autologous, MDM2-specific human leukocyte antigen (HLA)-A2-restricted T cells were identified using interferon (IFN)-gamma-ELISPOT assays and HLA-A2/dimer-peptide staining after 4 weeks of in vitro culture.


RESULTS
Using native CLL cells as antigen-presenting cells (APCs), we demonstrate the generation of MDM2-specific T cells in 7/12 CLL patients that recognized specifically the MDM2-derived peptide MDM2(81-88) bound to HLA-A2-dimers while they were inactive against an unrelated MAGE-3 peptide (p = 0.002). After 4 weeks, up to 32.3% of the expanded CD8(+) T cells specifically recognized MDM2(81-88) by HLA-A2-dimer/peptide staining and up to 0.9% of all T cells expanded reacted specifically against this MDM2-derived peptide in the IFN-gamma-ELISPOT assay. If T cells were not expandable using native CLL cells as APC, leukemic cells were stimulated with CD40-ligand to increase the antigen-presenting capacity. This resulted in successful generation of MDM2-specific T cells in three of five remaining cases tested. Additionally, the factor that correlated best with successful generation of antigen-specific T cells in CLL patients was the ability of APCs to secrete IFN-gamma upon stimulation.


CONCLUSIONS
In summary, MDM2(81-88) was shown for the first time in humans to elicit a functional autologous immune response. MDM2 was demonstrated to be naturally processed and presented as TAA in primary human CLL cells enabling expansion of functional autologous tumor-specific T cells.
Mayr
Christine
C
KKG Gene Therapy, GSF-National Research Center for Environment and Health, Munich, Germany.
Bund
Dagmar
D
Schlee
Martin
M
Bamberger
Martina
M
Kofler
David M
DM
Hallek
Michael
M
Wendtner
Clemens-Martin
CM
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017951:Antigen Presentation / Q000276:immunology; D000951:Antigens, Neoplasm / Q000235:genetics / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D002478:Cells, Cultured; D000939:Epitopes / Q000276:immunology; D005260:Female; D015973:Gene Expression Regulation, Leukemic / Q000235:genetics / Q000276:immunology; D015234:HLA-A Antigens / Q000276:immunology*; D015789:HLA-A2 Antigen; D006801:Humans; D066298:In Vitro Techniques; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics / Q000276:immunology*; D012333:RNA, Messenger / Q000235:genetics / Q000276:immunology; D014407:Tumor Cells, Cultured
D000951:Antigens, Neoplasm; D000939:Epitopes; D015234:HLA-A Antigens; C435939:HLA-A*02:01 antigen; D015789:HLA-A2 Antigen; D012333:RNA, Messenger; D051736:Proto-Oncogene Proteins c-mdm2