Fig 2: Low 15‐hydroxyprostaglandin dehydrogenase (15‐PGDH) expression is implicated in poor pancreatic ductal adenocarcinoma (PDAC) prognosis. A, Workflow diagram of patients who underwent pancreatic resection and contributed samples for immunohistochemical (IHC) analysis. B, Representative IHC staining of 15‐PGDH expression in 107 PDAC tissues. Scale bar = 100 μm. C,D, Relationship between 15‐PGDH expression and relapse‐free survival (C) or overall survival (D) using the Kaplan‐Meier method

Fig 3: Activated tumor‐associated macrophages produce interleukin‐1β (IL‐1β) and reduce 15‐hydroxyprostaglandin dehydrogenase (15‐PGDH) expression in pancreatic ductal adenocarcinoma cells. A, Concentration of IL‐1β in conditioned medium from PK‐8 cells or macrophages (Mφ) treated with lipopolysaccharide (LPS) or distilled water (DW) was evaluated by ELISA. B, Expression of 15‐PGDH in PK‐8 cells determined by Western blot analysis 72 hours after co‐culture with or without macrophages treated with LPS or DW. C, Expression of 15‐PGDH in PK‐8 cells determined by Western blot analysis 72 hours after treatment with conditioned medium from PK‐8 or macrophages treated with LPS or DW. D, Quantitative RT‐PCR analysis of CD163 mRNA expression in macrophages 24 hours after LPS or DW treatment; data are presented as the LPS‐treated / control expression ratio. E, Expression levels of CD163 in monocultured macrophages (middle panel) or macrophages co‐cultured with PK‐8 cells (upper panel) were evaluated by flow cytometry. F, Representative double‐immunohistochemical staining of 15‐PGDH (brown) and CD163 (green) in only PK‐8 cells (left panel), PK‐8 cells directly co‐cultured with non‐activated macrophages (middle panel), or PK‐8 cells directly co‐cultured with activated macrophages (right panel). Scale bar = 20 μm. G, Column graph showing the percentage of 15‐PGDH‐positive cells in only PK‐8 cells, PK‐8 cells directly co‐cultured with non‐activated macrophages, or PK‐8 cells directly co‐cultured with activated macrophages. H,I, Expression levels of IL‐1β in monocultured PK‐8 cells or PK‐8 cells co‐cultured with macrophages and in macrophages co‐cultured with PK‐8 cells were evaluated by flow cytometry. **P < .01. APC‐A, allophycocyanin; MFI, mean fluorescence intensity; PE‐A, phycoerythrin

Fig 4: 15-PGDH activity is highly enriched in splenic and marrow mast cells, megakaryocytes, and macrophages.(A) Quantification of 15-hydroxyprostaglandin dehydrogenase (15-PGDH) enzymatic activity in total unfractionated spleen and in splenic CD45, hematopoietic lineage (Lin), F4/80, CD61, and Fcεr1a negative and positive fractions, respectively, expressed as cpm per mg total protein, per hour. Filled symbols indicate each marker’s negative population. n = 3–7 mice/cell population. Error bars represent SEM. (B) Quantification of the frequency of F4/80+, CD61+, and Fcεr1a+ cells in the murine spleen. n = 3 mice. Error bars represent SEM. (C) Quantification of 15-PGDH enzymatic activity in total unfractionated BM and in BM CD45, F4/80, CD61, and Fcεr1a negative and positive fractions, respectively, expressed as cpm/mg total protein/hr. Filled symbols indicate each marker’s negative population. n = 3–7 mice/cell population. Error bars represent SEM. (D) Quantification of the frequency of F4/80+, CD61+, and Fcεr1a+ cells in the murine BM. n = 3 mice. Error bars represent SEM.

Fig 5: The spleen is critical for PGDHi-mediated hematopoietic regeneration.(A) Representative detection of 15-hydroxyprostaglandin dehydrogenase (15-PGDH) at 25 kDa and β-actin at 42 kDa in splenocyte and BM cell lysates. Two independent experiments of n = 2 mice per experiment. (B) Representative images of 15-PGDH staining (brown) in splenic red pulp (left) and tibial BM core (right). (Original magnification, ×20.) Three independent experiments of n = 2 mice per experiment. (C) Quantification of 15-PGDH enzymatic activity in spleen and BM, expressed as cpm per mg total protein, per hour. n = 5 mice. Error bars represent SEM. (D) Peripheral WBC, neutrophil (NE), and platelet (PLT) recovery in intact (top) and splenectomized (bottom) transplant recipients treated with either vehicle (Veh; blue) or 15-PGDH inhibitor (PGDHi; red). n = 12–15 mice/group. Data represent mean ± SEM. (E) BM cellularity and quantification of lineage–c-Kit+Sca-1+ (LSK) cells per hind limb of control and splenectomized recipients 20 days after transplant, treated with Veh (-) or PGDHi (+), expressed as fold change. n = 11–14 mice per group. Error bars represent SEM. **P < 0.01, ****P < 0.0001. Student’s t test used for all except peripheral blood recovery, where 2-way ANOVA was used and asterisks denote Veh vs. PGDHi over days 7 through 20.