Increased shedding of sIL-6Rα by the MDSCs of tumor-bearing mice. (A) Soluble IL-6Rα levels in culture supernatants of splenic MDSCs were measured by ELISA and (B) surface IL-6Rα levels on splenic MDSCs were measured by FACS. (C) The mRNA expression of Adam10 and Adam17 in splenic MDSCs of naïve and tumor-bearing mice were determined by qRT-PCR. (D-E) Protease inhibitor cocktails were applied to cultures of splenic MDSCs from 4T1 cell-bearing mice for 6 or 24 hours. (D) Membrane-bound IL-6Rα was detected by FACS and (E) soluble IL-6Rα levels were measured by ELISA. (F) Tissue sections were stained for Adam17 (green), Gr-1 (red), and DAPI (blue) to compare their localizations. Scale bar = 30 μm (original magnification, ×1,000). FACS, fluorescence-activated cell sorting; MDSCs, myeloid-derived suppressor cells.