LGR4 maintains HGSOC cell epithelial phenotype and stem-like traits

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.

TCGA and CCLE databases were interrogated for gene mRNA in ovarian cancer tissues and cell lines. Gain and loss of functions of LGR4, ELF3, FZD5 and WNT7B were performed to identify their roles in ovarian cancer cell epithelial phenotype and stem-like properties. In vivo experiments were performed to observe the effect of LGR4 on ovarian cancer cell growth and peritoneal seeding. The binding of ELF3 to LGR4 gene promoter was investigated by dual-luciferase reporter assays and ChIP.

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 ligand-receptor pair. Consistently, knockdown of ELF3, WNT7B, and FZD5, respectively, disrupted HGSOC cell epithelial phenotype and stem-like properties.

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.