LGR5 promotes invasion and migration by regulating YAP activity in hypopharyngeal squamous cell carcinoma cells

Abstract

Background High leucine-rich repeat-containing G-protein coupled receptor 5 (LGR5) expression caused by an inflammatory microenvironment was reported to promote tumor proliferation and the epithelial–mesenchymal transition (EMT) in various malignant tumors, but those effects have not been studied in hypopharyngeal squamous cell carcinoma (HSCC) and the molecular mechanism remains unclear. Additionally, YAP/TAZ, an upstream or downstream factor of multiple signaling pathways, can promote tumor proliferation, invasion, and angiogenesis. Our study was aimed to determine whether YAP/TAZ is involved in the regulation of LGR5 expression in the inflammatory microenvironment.Methods We stimulated FaDu cells, a hypopharyngeal squamous cell carcinoma cell line, with inflammatory medium. The expression levels of EMT-related proteins, LGR5, and p-YAP were detected by reverse transcription–polymerase chain reaction, western blotting, and immunofluorescence.Results The results showed that LGR5 expression and the EMT process were significantly enhanced. The expression of EMT-related proteins was up-regulated, while that of p-YAP was decreased. After inhibiting the high LGR5 expression with short interfering RNA, the expression of EMT-related proteins was also down-regulated, while that of p-YAP was significantly increased. The use of verteporfin (VP), an inhibitor of YAP activity that promotes YAP phosphorylation, did not affect LGR5 expression.Conclusions Our findings suggest that the inflammatory microenvironment leads to high LGR5 expression, up-regulating the expression of EMT-related proteins by inhibiting the YAP phosphorylation.