Identification of a new subset of myeloid suppressor cells in peripheral blood of melanoma patients with modulation by a granulocyte-macrophage colony-stimulation factor-based antitumor vaccine.
OBJECTIVE
Phenotypic and functional features of myeloid suppressor cells (MSC), which are known to serve as critical regulators of antitumor T-cell responses in tumor-bearing mice, are still poorly defined in human cancers. Here, we analyzed myeloid subsets with suppressive activity present in peripheral blood of metastatic melanoma patients and evaluated their modulation by a granulocyte-macrophage colony-stimulating factor (GM-CSF)--based antitumor vaccine.


METHODS
Stage IV metastatic melanoma patients (n = 16) vaccinated with autologous tumor-derived heat shock protein peptide complex gp96 (HSPPC-96) and low-dose GM-CSF provided pre- and post-treatment whole blood specimens. Peripheral-blood mononuclear cells (PBMCs) were analyzed by flow cytometry, separated into cellular subsets, and used for in vitro proliferation assays. PBMCs from stage-matched metastatic melanoma patients (n = 12) treated with non-GM-CSF-based vaccines (ie, HSPPC-96 alone or interferon alfa/melanoma-derived peptides) or sex- and age-matched healthy donors (n = 16) were also analyzed for comparison.


RESULTS
The lack of or low HLA-DR expression was found to identify a CD14+ cell subset highly suppressive of lymphocyte functions. CD14+HLA-DR-/lo cells were significantly expanded in all metastatic melanoma patients, whereas they were undetectable in healthy donors. Suppressive activity was mediated by transforming growth factor beta (TGF-beta), whereas no involvement of the arginase and inducible nitric oxide synthase pathways could be detected. CD14+HLA-DR-/lo cells, as well as spontaneous ex vivo release and plasma levels of TGF-beta, were augmented after administration of the HSPPC-96/GM-CSF vaccine. No enhancement of the CD14+-mediated suppressive activity was found in patients receiving non-GM-CSF-based vaccines.


CONCLUSIONS
CD14+HLA-DR-/lo cells exerting TGF-beta-mediated immune suppression represent a new subset of MSC potentially expandable by the administration of GM-CSF-based vaccines in metastatic melanoma patients.
Filipazzi
Paola
P
Unit of Immunotherapy of Human Tumors and Unit of Medical Statistics and Biometry, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico, Istituto Nazionale Tumori, Milan, Italy.
Valenti
Roberta
R
Huber
Veronica
V
Pilla
Lorenzo
L
Canese
Paola
P
Iero
Manuela
M
Castelli
Chiara
C
Mariani
Luigi
L
Parmiani
Giorgio
G
Rivoltini
Licia
L
D000328:Adult; D019496:Cancer Vaccines / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005434:Flow Cytometry; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000276:immunology*; D006684:HLA-DR Antigens / Q000276:immunology; D006360:Heat-Shock Proteins / Q000276:immunology; D006801:Humans; D008297:Male; D008545:Melanoma / Q000276:immunology* / Q000473:pathology / Q000517:prevention & control*; D022423:Myeloid Cells / Q000276:immunology*; D009362:Neoplasm Metastasis; D010641:Phenotype; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*; D016896:Treatment Outcome
D019496:Cancer Vaccines; D006684:HLA-DR Antigens; D006360:Heat-Shock Proteins; D016178:Granulocyte-Macrophage Colony-Stimulating Factor