Figure 1.

Prominent infiltration of myeloid immunosuppressive cells in iKRAS tumors. A. Quantification of tumor infiltrating CD45⁺ cells in syngeneic iKRAS tumors assessed by CyTOF at 4 weeks after initial tumor detection (n=10 samples/group). Two-sided Student’s t-test. B. SPADE tree derived from CyTOF analysis of whole-tumor cell population from syngeneic iKRAS PDAC tumors (n=10 tumors). Live single cells were used to construct the tree. Cell populations were identified as pancreatic ductal adenocarcinoma (PDAC) cells (EpCAM⁺CD45^-), non-immune TME cells (EpCAM^-CD45^-), CD4 or CD8 T cells (CD45⁺CD3⁺TCRβ⁺), B cells (CD45⁺B220⁺CD19⁺), Natural killer (NK) cells (CD45⁺NK1.1⁺), dendritic cells (CD45⁺CD11c⁺), MDSCs (CD45⁺CD11b⁺Gr1⁺) and macrophages (CD45⁺CD11b⁺Gr1^-F4/80⁺). C. CyTOF analysis of tumors from syngeneic and autochthonous iKRAS PDAC tumors with equivalent tumor volume (~1000mm³) (n=10 samples/group). D. Representative CFSE flow-cytometry histograms (left) showing the effect on in vitro T cell proliferation by MDSCs isolated from iKRAS tumors, and summarized result (right). Unstimulated T cells were used as negative control. Position of CFSE peaks can be used to denote the T cell division times. High and low proliferation were defined as T cell division ≥2 and ≤1, respectively (n=3 biological replicates). E. Effect on IFN-γ secretion from CD8⁺ T cells by MDSCs isolated from iKRAS tumors, measured by ELISA (n=3 biological replicates). Two-sided Student’s t-test. F. Quantification of tumor infiltrating CD4⁺ and CD8⁺ T cells in iKRAS tumors (n=3 biological replicates), assessed by flow cytometry and analyzed by FlowJo. Cell populations were identified as naive (CD44^lowCD62L^high), central memory (CD44^highCD62L^high), and effector memory (CD44^highCD62L^low). Data in A, E and F are presented as mean ± s.e.m.