Pancreatic tumors and immature immunosuppressive myeloid cells in blood and spleen: role of inhibitory co-stimulatory molecules PDL1 and CTLA4. An in vivo and in vitro study.
BACKGROUND
Blood and spleen expansion of immature myeloid cells (IMCs) might compromise the immune response to cancer. We studied in vivo circulating and splenic T lymphocyte and IMC subsets in patients with benign and malignant pancreatic diseases. We ascertained in vitro whether pancreatic adenocarcinoma (PDAC)-associated IMC subsets are induced by tumor-derived soluble factors and whether they are immunosuppressive focusing on the inhibitory co-stimulatory molecules PDL1 and CTLA4.


RESULTS
103 pancreatic and/or splenic surgical patients were enrolled including 52 PDAC, 10 borderline and 10 neuroendocrine tumors (NETs). Lymphocytes and IMCs were analysed by flow cytometry in blood, in spleen and in three PDAC cell conditioned (CM) or non conditioned PBMC. PDL1 and CTLA4 were studied in 30 splenic samples, in control and conditioned PBMC. IMCs were FACS sorted and co-coltured with allogenic T lymphocytes. In PDAC a reduction was found in circulating CD8(+) lymphocytes (p = 0.004) and dendritic cells (p = 0.01), which were reduced in vitro by one PDAC CM (Capan1; p = 0.03). Blood myeloid derived suppressive cells (MDSCs) CD33(+)CD14(-)HLA-DR(-) were increased in PDAC (p = 0.022) and were induced in vitro by BxPC3 CM. Splenic dendritic cells had a higher PDL1 expression (p = 0.007), while CD33(+)CD14(+)HLA-DR(-) IMCs had a lower CTLA4 expression (p = 0.029) in PDAC patients. In vitro S100A8/A9 complex, one of the possible inflammatory mediators of immune suppression in PDAC, induced PDL1 (p = 0.018) and reduced CTLA4 expression (p = 0.028) among IMCs. IMCs not expressing CTLA4 were demonstrated to be immune suppressive.


CONCLUSIONS
In PDAC circulating dendritic and cytotoxic T cells are reduced, while MDSCs are increased and this might favour tumoral growth and progression. The reduced CTLA4 expression found among splenic IMCs of PDAC patients was demonstrated to characterize an immune suppressive phenotype and to be consequent to the direct exposure of myeloid cells to pancreatic cancer derived products, S100A8/A9 complex in particular.
Department of Medicine, University of Padova, Padova, Italy. daniela.basso@sanita.padova.it
Daniela
D
Basso
Paola
P
Fogar
Massimo
M
Falconi
Elisa
E
Fadi
Cosimo
C
Sperti
Chiara
C
Frasson
Eliana
E
Greco
Domenico
D
Tamburrino
Sara
S
Teolato
Stefania
S
Moz
Dania
D
Bozzato
Michela
M
Pelloso
Andrea
A
Padoan
Giuseppe
G
De Franchis
Elisa
E
Gnatta
Monica
M
Facco
Carlo-Federico
CF
Zambon
Filippo
F
Navaglia
Claudio
C
Pasquali
Giuseppe
G
Basso
Gianpietro
G
Semenzato
Sergio
S
Pedrazzoli
Paolo
P
Pederzoli
Mario
M
Plebani
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D060890:B7-H1 Antigen / Q000276:immunology*; D001483:Base Sequence; D060908:CTLA-4 Antigen / Q000276:immunology*; D002469:Cell Separation; D017931:DNA Primers; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D016130:Immunophenotyping; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D010190:Pancreatic Neoplasms / Q000276:immunology* / Q000473:pathology; D013154:Spleen / Q000276:immunology*; D055815:Young Adult
D060890:B7-H1 Antigen; C423236:CD274 protein, human; D060908:CTLA-4 Antigen; C556706:CTLA4 protein, human; D017931:DNA Primers