Modulation of regulatory T cells and myeloid-derived suppressor cells by sorafenib and sunitinib in renal cell carcinoma patients

e16002 Background: Induction of regulatory T (Treg) and myeloid-derived suppressor cells (MDSC) is a major mechanism for the escape of tumors from immunological control. Increased levels of Treg cells have been described in renal cell cancer (RCC) patients and seem to correlate with an adverse outcome. Furthermore, reduction of Treg has been reported for RCC patients under sunitinib therapy. The aim of our study was to analyse the influence of sorafenib and sunitinib on the frequency of Treg and MDSC in patients with metastatic RCC (mRCC). Methods: The number of T reg, MDSC and lymphocyte subpopulations was analysed by flowcytometry in peripheral blood (pb) of patients (n=19) with histologically confirmed mRCC under treatment with either sunitinib (50 mg/d, n=11) or sorafenib (800 mg/d, n=8). After informed consent blood samples were taken before and during the 1st, 2nd, and 3rd month of therapy. Flowcytometric analysis was performed using fluorochrome labeled antibodies against CD3, CD4, CD8, CD25, CD127...