Granulocytic myeloid-derived suppressor cells are cryosensitive and their frequency does not correlate with serum concentrations of colony-stimulating factors in head and neck cancer

Abstract

Granulocytic myeloid-derived suppressor cells (MDSC) are a MDSC subset expanded in various cancer types. As many clinical studies rely on the use of stored collections of frozen blood samples, we first tested the influence of freezing/thawing procedures on immunophenotyping and enumeration of granulocytic MDSC (G-MDSC). To identify factors involved in expansion of human G-MDSC, we then analyzed correlations between G-MDSC frequencies, clinical parameters and granulocyte-related factors in the peripheral blood of head and neck cancer patients. HLA-DR, CD14, CD33 and CD66b allowed a clear discrimination of G-MDSC from monocytic MDSC and immature myeloid cells. MDSC subsets were sensitive to cryopreservation with immature G-MDSC showing the highest sensitivity. G-MDSC frequencies were increased in advanced disease stage and associated with the level of CCL4 and CXCL8, but not with colony-stimulating factors, IL-6, S100A8/9, CXCL1 and other cytokines. Our results indicate that the frequency of MDSC, in particular G-MDSC, may be underestimated in retrospective clinical analyses using frozen blood samples. Increased G-MDSC frequencies correlate with advanced disease and increased concentrations of CXCL8, but, unexpectedly, not with growth factors (such as granulocyte colony-stimulating factor), IL-6 and CXCL1. Our data suggest that CXCL8 promotes accumulation of G-MDSC in cancer patients independent of classical colony-stimulating factors.

Lack of Significant Elevation of Myeloid-Derived Suppressor Cells in Peripheral Blood of Chronically Hepatitis C Virus-Infected Individuals

“…Based on a comparison of fresh and frozen samples, we are convinced that MDSC should be studied on freshly isolated cells. In addition, it has been clearly shown that freezing of PBMC influences MDSC frequency and functional properties (9,10). Both studies reporting elevated M-MDSC frequencies in cHEP-C used frozen PBMC, which may explain the differences in the results.…”

Myeloid-derived suppressor cells in the tumor microenvironment: expect the unexpected

“…In healthy individuals, PMN-MDSCs are practically undetectable, and hence, few to no cells with this phenotype remain in the PBMC fraction. Although very useful in providing scientific information, the use of cell density as a clinical biomarker is limited by the fact that the density of PMN cells depends on the conditions of blood collection and storage and is prone to fluctuations that may affect the interpretation of the results (12). Development of definitive markers that will allow for one-step identification of MDSCs is necessary.…”

CTLA4 blockade reduces immature myeloid cells in head and neck squamous cell carcinoma

“…17,18 This finding promoted us to detect the correlation between the CD8 C /CTLA4 ratio and suppressive myeloid cells. We analyzed the CD11b, CD33, CD68, CD163, and Granzyme B expression by immunohistochemical staining in human HNSCC as shown in Fig.…”

“…S3). Considering that MDSCs and M2 macrophages can function as a negative regulator of antitumor immune response in HNSCC, 17,18 We focused on whether therapeutic blockade of CTLA4 could decrease MDSCs and M2 macrophages in this mouse model. The single cell suspense from the spleen, LN, blood, and tumor were stained by antibody for CD11b, Gr-1, and F4/80 (Fig.…”