LGR4 Maintains HGSOC Cell Epithelial Phenotype and Stem-Like Traits

Abstract Background: High-grade serous ovarian cancer (HGSOC) is lethal mainly due to extensive metastasis. Cancer cell stem-like properties are responsible for HGSOC metastasis. LGR4, a G-protein-coupled receptor, is involved in the maintenance of stem cell self-renewal and activity in some human organs. Methods: TCGA and CCLE database was interrogated for gene mRNA analysis in ovarian cancer tissues and cell lines. The interactions between LGR4 and ELF3 were validated through dual-luciferase reporter assays, Chip assays and Co-IP assays. Gain- and loss-of functions of LGR4, ELF3, FZD5 and WNT7B were performed to identify their roles in the behaviors of ovarian cancer cells. Flowcytometry analysis and tumorisphere formation assays were performed to identified their stem-like properties. In vivo experiments were performed as well.Results: LGR4 was shown to be overexpressed in HGSOCs and maintain the epithelial phenotype of HGSOC cells. LGR4 knockdown suppressed POU5F1, SOX2, PROM1 (CD133) and ALDH1A2 expression. Furthermore, LGR4 knockdown reduced CD133+ and ALDH+ subpopulations and impaired tumorisphere formation. To the contrary, LGR4 overexpression enhanced POU5F1 and SOX2 expression and tumorisphere formation capacity. LGR4 knockdown inhibited HGSOC cell growth and peritoneal seeding in xenograft models. Mechanistically, LGR4 and ELF3, an epithelium-specific transcription factor, formed a reciprocal regulatory loop, which was positively modulated by WNT7B/FZD5 pair. Consistently, knockdown of ELF3, WNT7B, and FZD5, respectively, disrupted HGSOC cell epithelial phenotype and stem-like properties. Conclusion: Together, these data demonstrate that WNT7B/FZD5-LGR4/ELF3 axis maintains HGSOC cell epithelial phenotype and stem-like traits; targeting this axis may prevent HGSOC metastasis.