Abstract only
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 (CD44
High
/CD133
High
) 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.
Background: Colon cancer stem cells (CSCs), considered responsible for tumor initiation and cancer relapse, are constantly exposed to regulatory cues emanating from neighboring cells present in the ...tumor microenvironment. Among these cells are enteric glial cells (EGCs) that are potent regulators of the epithelium functions in a healthy intestine. However, whether EGCs impact CSC-driven tumorigenesis remains unknown. Methods: Impact of human EGC primary cultures or a non-transformed EGC line on CSCs isolated from human primary colon adenocarcinomas or colon cancer cell lines with different p53, MMR system and stemness status was determined using murine xenograft models and 3D co-culture systems. Supernatants of patient-matched human primary colon adenocarcinomas and non-adjacent healthy mucosa were used to mimic tumor versus healthy mucosa secretomes and compare their effects on EGCs. Findings: Our data show that EGCs stimulate CSC expansion and ability to give rise to tumors via paracrine signaling. Importantly, only EGCs that were pre-activated by tumor epithelial cell-derived soluble factors increased CSC tumorigenicity. Pharmacological inhibition of PGE2 biosynthesis in EGCs or IL-1 knockdown in tumor epithelial cells prevented EGC acquisition of a pro-tumorigenic phenotype. Inhibition of PGE2 receptor EP4 and EGFR in CSCs inhibited the effects of tumor-activated EGCs. Interpretation: Altogether, our results show that EGCs, once activated by the tumor, acquire a pro-tumorigenic phenotype and stimulate CSC-driven tumorigenesis via a PGE2/EP4/EGFR-dependent pathway. Funding: This work was supported by grants from the French National Cancer Institute, La Ligue contre le Cancer, the ‘Région des Pays de la Loire’ and the UNC Lineberger Comprehensive Cancer Center. Keywords: Enteric glial cells, Colon cancer stem cells, Colorectal cancer: Tumor microenvironment, PGE2
PDF
