Enteric Glial Cells Activate Colon Cancer Stem Cells to Promote Tumorigenesis

Abstract

Colon cancer stem cells (CSCs) are regulated by their cellular microenvironment that delivers paracrine signals crucial to CSC maintenance and tumor growth. Among CSC neighboring cells are enteric glial cells (EGCs) that are potent regulators of intestinal epithelium functions, but whose impact on CSCs has never been studied. We hypothesized that EGCs modulate CSC functions and associated tumorigenesis.In vitro. CSCs were FACS‐isolated from HT29 colon cancer epithelial cells (CD44High/CD133High) and 3D cultured in Matrigel in presence of EGCs seeded on Transwell filters. Impact of EGCs was assessed on numbers and size of tumorspheres grown from CSCs and compared to known EGC‐derived soluble factors. In vivo. CSCs were injected alone vs. concomitantly with EGCs subcutaneously in immunodeficient mice.In vitro EGCs increased numbers and size of tumorspheres grown from CSCs. In vivo concomitant injection of CSCs and EGCs increased tumor load vs. CSCs alone. In vitro EGC‐conditioned medium (CM) did not impact CSCs, but CM of EGCs that had been pre‐incubated with HT29 cells increased tumorsphere numbers, indicating that tumor cells activate EGCs to acquire pro‐tumorigenic abilities. Among all known glial factors tested, only prostaglandin E2 (PGE2) reproduced EGC effects on CSCs. HT29 cells increased expression of mPGES‐1 (enzyme generating PGE2) and PGE2 release in EGCs. CAY10526 (mPGES‐1 inhibitor) abolished pro‐tumorigenic properties induced by HT29 cells in EGCs.These results suggest that tumor cells activate EGCs to acquire pro‐tumorigenic abilities, and that tumor‐activated EGCs stimulate CSC tumorigenicity via PGE2‐dependent pathways.