TSAPN9-media Ted Autophagy Promotes 5-FU Metabolism In Gastric Cancer

Purposes:Gastric cancer is one of the most common gastrointestinal tumors.Because of its low early diagnosis rate,patients are often in advanced stages when diagnosed.Chemotherapy is the main treatment method for patients with gastric cancer.Among them.5-fluorouracil(5-FU)is the basic drug for the treatment of gastric cancer,but its drug resistance has attracted worldwide attention.TSPAN9 is a 4-transmembrane protein that plays an important role in tumor progression and information transmission.Previous studies have found that it is closely related to tumor invasion,metastasis and autophagy.The purpose of this study is to explore the molecular mechanisms involved in 5-FU resistance in gastric cancer and provide new ideas for overcoming resistance in gastric cancer.Methods:The expression of TSPAN9 in normal cells and gastric cancer cells was detectedby quantitative real-time PCR and western blotting,and verified at the tissue level by immunohistochemistry.The 5-FU drug-resistant gastric cancer cell lines were cultured by gradual exposure method and the expression of TSPAN9 in normal and drug-resistant gastric cancer cell lines was tested again.Through functional experiments,such as CCK-8,the effects of TSPAN9 on gastric cancer cell proliferation and 5-FU sensitivity are detected Western blot was used to analyze the PI3K/AKT/mTOR-mediated autophagy pathway induced by TSPAN9.Finally,co-immunoprecipitation was used to evaluate the specific mechanism of TSPAN9 affecting the PI3K pathway.Results:In this experiment,we found that the expression of TSPAN9 in tumor tissues ishigher than that in normal tissues,and the high expression status of TSPAN9 often indicates poor prognosis.It was also found that TSPAN9 was over-expressed in drug-resistant cells,and the effects that cell proliferation inhibited could be significantly restored by increasing TSPAN9 expression,while inhibition of TSPAN9 expression in drug-resistant cells could restore cells to 5-FU Sensitivity.In addition,TSPAN9 significantly promoted autophagy of gastric cancer cells in vitro.Further research confirms that TSPAN9 can interact with PI3K protein and inhibit its catalytic activity.Therefore,it inhibits the autophagy level in gastric cancer cells by inhibiting the PI3K AKT/mTOR signaling pathway and down-regulating PBK-mediated autophagy-related protein expression.Conclusion:This study shows that in gastric cancer cells,TSPAN9 and PI3K combinewith each other to inhibit the activity of the PI3K/AKT/mTOR pathway,thereby enhancing autophagy levels and promoting 5-FU resistance.The phosphorylation of TSPAN9 is the key to promote the binding of TSPAN9 to PI3K.Through this mechanism,TSPAN9 protects gastric cancer cells from 5-FU-induced cell death and increases drug resistance.Revealed the important role of TSPAN9 in 5-FU resistance of gastric cancer,provided a new target for clinical resistance research of gastric cancer,and will contribute to the improvement of gastric cancer treatment strategies.