LGR5 promotes survival in human colorectal adenoma cells and is upregulated by PGE2: implications for targeting adenoma stem cells with NSAIDs.
Cyclooxygenase-2 is overexpressed in the majority of colorectal tumours leading to elevated levels of prostaglandin E2 (PGE2), promoting many hallmarks of cancer. Importantly, PGE2 is reported to enhance Wnt/β-catenin signalling in colorectal carcinoma cells and in normal haematopoietic stem cells where it promotes stem cell function. Although Wnt signalling plays a crucial role in intestinal stem cells, the relationship between PGE2 and intestinal stem cells is unclear. Given that the key intestinal cancer stem cell marker LGR5 (leucine-rich G-protein coupled receptor 5) is a Wnt target and PGE2 enhances Wnt signalling, the focus of this study was to investigate whether PGE2 regulated LGR5 expression in colorectal adenoma cells and whether LGR5 was important for tumour cell survival. PGE2 upregulated LGR5 protein in adenoma (RG/C2) and carcinoma (DLD-1) cell lines. LGR5 knockdown induced cell death in RG/C2 and AA/C1 adenoma cells, suggesting that LGR5 has an important survival-promoting role in adenoma cells. Indeed, we detected LGR5 protein expression in 4 of 4 human adenoma cell lines. Furthermore, LGR5 small interfering RNA inhibited the survival-promoting effects of PGE2 in RG/C2, suggesting that PGE2 promotes adenoma cell survival, at least in part, by increasing LGR5 expression. These studies, therefore, show the first link between PGE2 and LGR5 in human colorectal adenoma and carcinoma cells and demonstrate a survival-promoting role of LGR5. As non-steroidal anti-inflammatory drugs (NSAIDs) cause adenomas to regress in FAP patients, these studies could have important implications for the mechanism by which NSAIDs are chemopreventive, as lowering PGE2 levels could reduce LGR5 expression and survival of LGR5(+) adenoma stem cells.
Cancer Research UK Colorectal Tumour Biology Group, School of Cellular and Molecular Medicine, Medical Sciences Building, University Walk, University of Bristol, UK.
Manal R A
MR
Al-Kharusi
Helena J M
HJ
Smartt
Alexander
A
Greenhough
Tracey J
TJ
Collard
Elizabeth D
ED
Emery
Ann C
AC
Williams
Chris
C
Paraskeva
D000236:Adenoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D002277:Carcinoma / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D015232:Dinoprostone / Q000235:genetics / Q000378:metabolism*; D005260:Female; D006801:Humans; D008875:Middle Aged; D014411:Neoplastic Stem Cells / Q000187:drug effects / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation; D060449:Wnt Signaling Pathway / Q000187:drug effects / Q000235:genetics; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism
D000894:Anti-Inflammatory Agents, Non-Steroidal; C116884:LGR5 protein, human; D043562:Receptors, G-Protein-Coupled; D051176:beta Catenin; D015232:Dinoprostone