Pseudophosphatase STYX Promotes Gastric Cancer Progression By Inhibiting FBXO31 Function

Background:Gastric cancer(GC)is one of the most common malignances around the world.Due to the difficulties to diagnose at an early stage and lacking effective targeted drugs,resulting in poor prognosis and high mortality of GC patients.Therefore,it is of great significance to explore the molecular mechanism of GC occurrence and development as well as finding the effective early diagnostic biomarkers and therapeutic targets for GC.The catalytically inactive pseudophosphatase STYX belongs to the protein tyrosine phosphatase(PTPs)family.It has convinced that STYX has been implicated in various biological function and diseases,such as spermiogenesis,neurite outgrowth and cancer.In this thesis,we studied the expression of STYX in GC tissues and its effect on the occurrence and development of GC.Furthermore,we explored the regulatory mechanism of STYX in GC cells and evaluated its potential value as a target for early diagnosis and treatment of GC.Methods:1.Using TCGA and GEO databases to analyze the expression of STYX mRNA in GC and adjacent tissues.Proteins extracted from GC patients were detected by Western Blot to analyze the expression of STYX in GC and adjacent tissues,then performing gray value analysis for statistical test.GSEA software and Kaplan-Meier(KM)plotter database were used to analyze the association between STYX and GC progression and survival.2.Constructing STYX overexpressed plasmid and synthesizing specific siRNAs to target STYX.Using EdU,CCK-8 and Transwell assay to detect the biological function of STYX overexpression or knockdown in GC cells.3.Nude mice xenograft model and nude mice tail vein injection experiment were performed to detect the biological functions of STYX in vivo.4.Co-IP and Western Blot experiments were used to explore the mechanism of STYX in GC cells.EdU,CCK-8 and Transwell experiments were used to perform biological function recovery assay to verify the mechanism of STYX function.5.qRT-PCR and Werstern Blot were used to explore the effect of H.pylori infection on STYX expression level and related pathways.Results:1.Expression level of STYX in GC tissues.TCGA and GEO database analysis showed that the expression of STYX in GC tissues was significantly higher than that in adjacent tissues.Western Blot analysis further confirmed that STYX was significantly overexpressed in GC tissues at protein level.GSEA analysis proved that STYX was positively correlated with cell cycle,EMT and common cancer genes.KM Plotter analysis suggested that STYX expression level was negatively correlated with the survival of GC patients.2.Biological function of STYX in GC cells.Experiments have confirmed that STYX overexpression can significantly promote the proliferation and metastasis of GC cells in vitro and in vivo,while knockdown STYX has the opposite effect.3.The molecular mechanism of STYX to fulfill biological function.We found that STYX interacts with E3ubiquitin ligase FBXO31 and disrupts the degradation function of FBXO31 to its target protein Cyclin D1 and Snail1,thereby increasing the level of Cyclin D1 and Snail1 in GC.4.STYX promoted the proliferation and migration of GC cell via FBXO31.We used a recovery assay to demonstrate that STYX-mediated biological changes can be reversed by the co-expression of STYX and FBXO31 in GC cells.5.Regulation mechanism of STYX expression by H.pylori.The transcription factor c-Jun could increase the expression of STYX in GC cells and the expression of STYX could be induced by H.pylori infection in c-Jun-dependent manner.Conclusion:The expression of STYX is abnormally high in GC tissues,and both in vitro and in vivo experiments show that STYX highexpression can significantly promote the proliferation and metastasis of GC cells;In terms of mechanism,STYX inhibits the function of FBXO31 by interacting with FBXO31,indirectly affects the expression level of Cyclin D1 and Snail1 downstream of FBXO31,and the function of STYX can be restored by FBXO31;In addition,H.pylori can promote the expression of STYX through c-Jun.This study revealed the role and mechanism of STYX in occurrence and development of GC,suggesting that STYX may be used as a potential therapeutic target and marker for early diagnosis of GC.