Fig. 1.

KPC-derived PDAC is characterized by infiltration with myeloid cells and a T cell-deprived tumor microenvironment (TME). T110299 tumors were implanted orthotopically in syngeneic C57BL/6 mice which were sacrificed at days 7, 14 and 21 after tumor induction for analysis of blood, spleen and tumor. a-b Spleen and tumor weights and respective correlation analysis. c Relative frequency of leukocytes in blood, spleen and tumor. d-e Correlation of relative immune cell frequency with tumor weight. f Correlation of serum G-CSF level with PMN-MDSC frequency in blood and spleen as well as correlation of tumor weight with G-CSF level in serum. g-h Surface expression of arginase-1 and PD-L1 on MDSC. i PD-1 expression on T cells in spleens and tumors. j MDSC-like cells from naïve mice as well as MDSC from spleens and tumors of tumor-bearing mice were isolated and co-cultured with CFSE-labeled T cells in increasing effector (E; MDSC) to target (T; T cell) ratios (E:T) of 0.25:1, 0.5:1 and 1:1, in the presence of anti-CD3/anti-CD28 mAb-coated beads. After 72 h CFSE dilution of T cell populations was assessed. a,c,g,h,i Data ± SEM is shown for n = 4–5 mice per group. b,d,f n = 12 mice (e) n = 12 mice / group (c) Statistics for the comparison of day 0 and day 21 (blood and spleen), and day 7 and day 21 (tumor) are shown. (j) Representative graph of three independent experiments, Data± SEM for n = 2 mice per group, unpaired two-sided students t test (*p < 0.05, **p < 0.01, in J compared to tumor-free control)