Pseudophosphatase STYX is induced by Helicobacter pylori and promotes gastric cancer progression by inhibiting FBXO31 function

Gastric cancer (GC) is one of the most common malignancies in the world and ranks third in terms of cancer-related deaths. The catalytically inactive pseudophosphatase STYX (serine/threonine/tyrosine interacting protein) is a member of the protein tyrosine phosphatase family. It has been recently reported that STYX functions as a potential oncogene in different types of cancers. However, the potential role and regulatory mechanism of STYX in GC remains unknown. In this study, we find that STYX is highly expressed in GC tissues compared with adjacent noncancerous tissues and closely correlates with the prognosis of GC patients. STYX overexpression facilitates the proliferation and migration in GC cells, whereas STYX knockdown has the opposite effects. Nude mice experiments indicate that STYX knockdown in GC cells dramatically suppresses the tumor growth and lung metastasis in vivo. Mechanically, our results suggest that STYX interacts with the F-box protein FBXO31 and disrupts the degradation function of FBXO31 to its target proteins CyclinD1 and Snail1, thereby increasing the level of CyclinD1 and Snail1 in GC. STYX-mediated biological changes can be reversed by the co-expression of STYX and FBXO31 in GC cells. In addition, transcription factor c-Jun can enhance the expression of STYX in GC. The expression of STYX can also be induced by Helicobacter pylori (H. pylori) infection in c-Jun-dependent manner. Together, our present study suggests that STYX plays an oncogenic role in GC by inhibiting FBXO31 function and represents a potential therapeutic target and prognostic biomarker in GC.