The prognostic value of glycosylphosphatidylinositol-anchored 80 kD protein (GPI-80) positive myeloid derived suppressor cells (MDSCs) in peripheral blood of metastatic renal cell carcinoma (mRCC) patients.

Abstract

601 Background: Myeloid derived suppressor cells (MDSCs) are found to play essential roles in various tumors and to associate with the prognosis of patients. However, the prognostic values of MDSCs in metastatic renal cell cancer (mRCC) are still undefined. Glycosylphosphatidylinositol-anchored 80 kD protein (GPI-80) is known as a regulator of Mac-1 (CD11b/CD18) and closely related with differentiation of myeloid cells. The object of our study was to interrogate the association of MDSCs in peripheral blood with clinical outcomes of mRCC patients by using GPI-80. Methods: Peripheral blood samples, collected from 23 mRCC patients before treatment and 16 healthy volunteers, were stained with several myeloid cell antigens such as CD16, CD15, CD33, and GPI-80 to mark neutrophils and monocytes. We measured the expression levels (mean of florescence intensity, MFI) and deviation (coefficient variation, CV) of myeloid antigens by flow cytometry. To investigate the immunosuppressive function of GPI-80 positive cells, reactive oxygen species (ROS) and LAP-1 (precursor of TGF-β1) were measured. The impact of the cell surface antigens on overall survival (OS) was evaluated using the univariate and multivariate Cox regression analysis. Results: The MFI or CV of GPI-80 on neutrophilic or monocytic cells were significantly difference in between patients and healthy volunteers. LAP-1 expression and ROS production in monocytic cells were increased in patients than in healthy volunteers, and correlated with expression of GPI-80 MFI (p = 0.0107 and p = 0.0381, respectively). Regarding the prognostic values, both GPI-80 CV of neutrophilic cells and GPI-80 MFI of monocytic cells were associated with poor OS of mRCC patients (p < 0.01). Multivariate analysis showed that GPI-80 MFI of monocytic cells were independent unfavorable prognosis marker (HR 2.427, p = 0.044). Conclusions: These results showed that change of GPI-80 expression on myeloid cells in peripheral blood representing appearance of MDSCs was likely to be negative predictors in patients with mRCC.