The purity after sorting was greater than 95%. Tumor and MDSC conditioned medium preparation EMT6 cells and 4T1 cells were incu bated for 72 hours on a 24 well plate and the culture supernatants were collected. To obtain MDSC CM, FACS sorted splenic MDSCs were cultured for 24 hours. 4T1 MDSC CM and EMT6 MDSC CM were prepared by cultivating MDSCs in 50% further info 4T1 CM or EMT6 CM for 24 hours. A volume of 4T1 MDSC CM containing 1 ng of IL 6, or the same volume of EMT6 MDSC CM or MDSC CM, was added to the 4T1 and EMT6 cell cultures. To some cultures, the following signaling inhibitors were added. Stat3 inhibitor peptide, PI3K inhibitor, NF B inhibitor, JNK inhibitor, p38 MAPK inhibitor, and ERK inhibitor. Immunofluorescence microscopy Tissues were fi ed in 4% PFA and embedded in paraffin.

Sections were stained with H E for histopathological analysis. To investigate IL 6, IL 6Ra, and Adam17 e pression levels in MDSCs, sections were stained with anti Gr 1 mAb and other appropriate antibodies. The following primary antibodies were used anti mouse IL 6, anti mouse IL 6Ra, anti mouse Adam17 and anti mouse Gr 1. The following secondary antibodies were used Ale a 488 conjugated anti rabbit IgG and Ale a 594 conjugated anti rat IgG. Image acquisition and processing was performing using a confocal fluorescence microscope and an FV10 ASW 2. 0 Viewer. ELISA EMT6 and 4T1 cells were plated on a 24 well plate. The cells were permitted to grow for 24 or 48 hours. Supernatants were collected and assayed for IL 6 and soluble IL 6Ra levels by ELISA.

For IL 6 detection, anti mouse IL 6 was used as the capture antibody, biotinylated anti mouse IL 6 in 0. 1% BSA in PBS T as the detection antibody and recombi nant IL 6 as the standard. To detect soluble IL 6Ra, we used anti mouse IL 6Ra as the capture antibody, biotinylated anti mouse IL 6Ra as the detection Batimastat antibody and recombinant IL 6Ra as the standard. RNA analysis RNA was isolated from sorted splenic MDSC using the RNeasy kit. cDNA was generated from 1 ug of total RNA by reverse tran scriptase from Moloney Murine Leukemia Virus, and subjected to PCR. PCR products were analyzed by 1. 5% agarose gel electrophoresis. Western blot analysis Cells were harvested in lysis solution containing 50 mM Tris HCl, 1% NP40, 150 mM NaCl, 2 mM EDTA, 100 uM PMSF, a protease inhibitor cocktail, and a phos phatase inhibitor.

After incubation on ice for 30 minutes, cellular debris was removed by centrifuga chronic myelocytic leukemia tion. Proteins were separated by SDS PAGE and then transferred to a polyvinylidene difluoride membrane. After blocking with 5% skim milk, the membranes were probed with an appropriate antibody. Blots were developed with an enhanced chemilumines cence Western blotting detection system. The following antibodies were used anti b actin, anti phospho Stat3, anti Stat3, anti I B, anti phospho JNK, anti phospho ERK, and anti phospho p38. Invasion assay Matrigel matri solution was applied to each Transwell.