REG4 Promotes Peritoneal Metastasis Of Gastric Cancer

Objective: To investigate the effect and mechanism of REG4 on peritoneal metastasis of gastric cancer and discover a positive feedback loop triggered by REG4 in this process.Methods: REG4 expression was examined in gastric cancer tissues by immunohistochemistry staining.REG4 overexpressed cell lines were used to perform adhesion and peritoneal metastasis assays.A potential transcription factor of REG4 was identified by promoter scanning and was confirmed by ChIP,luciferase reporter assay and biofunctional experiments.An interactive partner of REG4 was identified by mass spectrometry and their interaction was verified by co-IP and IF.Its effect on REG4 signal transduction was tested by in vitro and in vivo experiments.The activity of ADAM17 and concentration of TGF-alpha were evaluated in order to discover a positive feedback loop.Potential downstream effectors of REG4 were investigated by PCR array.Results: High REG4 expression was significantly associated with poor differentiation,lymph node metastasis,advanced TNM stage,and poor outcome.REG4 overexpression significantly enhanced peritoneal metastasis by increasing adhesion ability.Moreover,SP1 was proved to be a transcription factor of REG4 and induce REG4 expression upon TGF-alpha stimulation.Also,G protein-coupled receptor 37(GPR37)was identified to be in the same complex of REG4,which mediates REG4's signal transduction and promotes peritoneal metastasis of gastric cancer cells.We also discovered a positive feedback loop triggered by REG4,amplifying itself through EGFR transactivation,consisting of GPR37,ADAM17,TGF-alpha,EGFR,ERK,SP1 and REG4.Six molecules associated with adhesion ability were identified to be potential downstream effectors.Conclusions: REG4 promotes peritoneal metastasis of gastric cancer through GPR37 by increasing adhesion ability,and is able to trigger a positive feedback loop,covering GPR37,ADAM17,TGF-alpha,EGFR,ERK,SP1 and REG4.