Dissection of gastric homeostasis in vivo facilitates permanent capture of isthmus-like stem cells in vitro.

The glandular stomach is composed of two regenerative compartments termed corpus and antrum, and our understanding of the transcriptional networks that maintain these tissues is incomplete. Here we show that cell types with equivalent functional roles in the corpus and antrum share similar transcriptional states including the poorly characterized stem cells of the isthmus region. To further study the isthmus, we developed a monolayer two-dimensional (2D) culture system that is continually maintained by Wnt-responsive isthmus-like cells capable of differentiating into several gastric cell types. Importantly, 2D cultures can be converted into conventional three-dimensional organoids, modelling the plasticity of gastric epithelial cells in vivo. Finally, we utilized the 2D culture system to show that Sox2 is both necessary and sufficient to generate enterochromaffin cells. Together, our data provide important insights into gastric homeostasis, establish a tractable culture system to capture isthmus cells and uncover a role for Sox2 in enterochromaffin cells.

Role of Tumor-Associated Macrophages in the Clinical Course of Pancreatic Neuroendocrine Tumors (PanNETs).

PURPOSE: This study evaluated the potential role of immune cells and molecules in the pathogenesis and clinical course of pancreatic neuroendocrine tumors (PanNET). EXPERIMENTAL DESIGN: Surgically resected PanNETs (N = 104) were immunohistochemically analyzed for Ki67 index, mitotic rate, macrophage, CD4+ cells, and CD8+ T-cell infiltration, as well as HLA class I, PD-L1, and B7-H3 expression. Results were correlated with clinicopathologic characteristics as well as with disease-free (DFS) and disease-specific (DSS) survival. RESULTS: The median age of the 57 WHO grade 1 and 47 WHO grade 2 patients was 55 years. High intratumoral CD8+ T-cell infiltration correlated with prolonged DFS (P = 0.05), especially when the number of tumor-associated macrophages (TAM) was low. In contrast, high peritumoral CD4+ cell and TAM infiltration was associated with a worse DFS and DSS. PD-L1 and B7-H3 were expressed in 53% and 78% PanNETs, respectively. HLA class I expression was defective in about 70% PanNETs. HLA-A expression correlated with favorable DSS in PD-L1-negative tumors (P = 0.02). TAM infiltration (P = 0.02), WHO grade (P = 0.04), T stage (P = 0.01), and lymph node positivity (P = 0.04) were independent predictors of DFS. TAM infiltration (P = 0.026) and T stage (P = 0.012) continued to be predictors of DFS in WHO grade 1 PanNET patients. TAM infiltration was the sole independent predictor of DSS for WHO grade 1 and 2 patients (P = 0.02). Therefore, this biomarker may contribute to identifying WHO grade 1 patients with poor prognosis. CONCLUSIONS: TAM infiltration appears to be the most informative prognostic biomarker in PanNET. It may represent a useful immunotherapeutic target in patients with PanNET.