Targeted inhibition of Wntless/GPR177 suppresses gastric tumorigenesis

Abstract

Wntless/GPR177 functions as WNT ligand carrier protein and activator of WNT/β-catenin signaling, however, its role in gastric tumorigenesis has remained elusive. We investigated the role of GPR177 in gastric tumorigenesis and provided the therapeutic potential of a clinical development of anti-GPR177 antibodies. GPR177 mRNA and protein expression were associated with unfavorable prognosis [log-rank test, GSE15459 (p=0.00736), GSE66229 (p=0.0142), and Yonsei TMA (p=0.0334)] and identified as an independent risk predictor of clinical outcomes {GSE15459 [hazard ratio (HR) 1.731 (95% confidence interval; CI; 1.103–2.715), p=0.017], GSE66229 [HR 1.54 (95% CI, 1.10–2.151), p=0.011], and Yonsei TMA [HR 1.254 (95% CI, 1.049–1.500), p=0.013]. Overall survival and multivariate prognostic significance of GPR177 expression were analyzed by Kaplan-Meier curves (log-rank test) and Cox proportional hazard regression models, respectively. GC cell lines were classified as WNT-secreting or non–WNT-secreting. Anti-GPR177 antibody reduced WNT secretion and viability in WNT-secreting cells by inhibition of WNT/β-catenin signaling. GPR177 alleviated ER–stress-induced apoptosis by ectopic localization to ER in non–WNT-secreting cells. Antibody treatment suppressed proliferation of WNT-secreting cells only; however, GPR177 knockdown sensitized non–WNT-secreting cells to ER–stress-induced apoptosis. Anti-GPR177 antibodies exhibited anti-cancer efficacy in xenograft and PDX models. GPR177 overexpression correlated with poor GC patient prognosis. Inhibition of GPR177 using monoclonal antibodies or short–hairpin–RNA-mediated knockdown suppresses in vitro and in vivo tumorigenesis in WNT-secreting GC cells and inhibits WNT/β-catenin signaling. Non–WNT-secreting cells were sensitized by GPR177 knockdown, but not by antibody treatment, via enhancement of ER stress, leading to cell death. Anti-GPR177 antibody treatment suppresses in vivo gastric tumorigenesis.