The Roles And Mechanisms Of MUC16 In Invasion And Metastasis Of Gastric Cancer

Background: At present,gastric cancer is one of the most common tumors in the world.The incidence of gastric cancer is fourth,and it is the third major cause of cancer related death in the world.Metastasis and recurrence after treatment are still a major challenge for the treatment of gastric cancer.The study of the mechanism of invasion and metastasis of gastric cancer will help to further understand the development of gastric cancer and provide a new theoretical basis for the control of gastric cancer.MUC16 is overexpressed in pancreatic,esophageal,colon and gastric cancer tissues.The proteolysis of MUC16 leads to the enteral of extracellular part from the cell membrane into the serum or extracellular substance which is known as CA125.MUC16 plays an important role in tumor growth,proliferation and invasion and metastasis.The adhension of MUC16 and mesothelin promotes the peritoneal metastasis of ovarian cancer,and the signal involved in the intracellular segment of MUC16 promotes the metastasis of the tumor.Circulating tumor cells play an important role in the metastasis of tumors.There is more metastatic potential for circulating tumor cell microemboli than single circulating tumor cell.Lymph node metastasis and peritoneal metastasis occur in most of the stage IV patients with gastric cancer.There was no study on the role and mechanism of MUC16 in gastric cancer as well as the relationship between MUC16 and circulating tumor cells.Objective: Based on the above,in this study,we intend to explore the effect of MUC16 on the invasion and metastasis of gastric cancer and its specific mechanism.It may provide a new theoretical basis for the diagnosis and treatment of gastric cancer,and to deepen the understanding of metastasis of gastric cancer.Methods: In this experiment,the expression of MUC16 was detected by immunohistochemistry and its relationship with clinicopathological features and prognosis was analyzed.Immunofluorescence,Western blot and real-time fluorescence PCR were used to detect the expression of MUC16 in gastric cancer cell lines and normal gastric epithelial cells.After knockdown of MUC16 or over-expression of 268 amino acids of C-terminus of MUC16 by plasmid,scratch test,Transwell migration assay,Transwell invasion assay,mouse lung metastasis model,and detection of circulating tumor cells in peripheral blood were used to detect changes in migration and invasiveness.Transcriptome sequence analysis was used to study the downstream regulatory molecules of MUC16 and the influences of the downstream regulatory molecules on gastric cancer cell migration and invasive were investigated.Co-immunoprecipitation experiments was used to validate the interaction molecule of MUC16 C-terminal.The signaling pathways were studied by Western blot.Membrane filter was used to enrich circulating tumor cells peripheral blood,and the relationship between MUC16 expression and circulating tumor cells was analyzed.Results: Immunohistochemical staining showed that the expression of MUC16 in gastric carcinoma was up-regulated compared to normal tissues around the cancer.The expression of MUC16 was related to lymphatic metastasis,TNM stage and the degree of differentiation.Elevated expression of MUC16 was associated with shorter OS in patients with gastric cancer.Immunofluorescence,Western blot and real time fluorescence PCR showed that the expression of MUC16 in gastric cancer cell line was higher than that of normal epithelial cells of gastric cancer.Downregulation of MUC16 expression by shRNA can significantly reduce the migration and invasion ability of gastric cancer cells,reduce the number of circulating tumor cell microemboli in mice,and overexpression of the 268 amino acid of C terminal of MUC16 could improve the migration and invasion ability of gastric cancer cells.The transcriptome sequence analysis showed that NTS was the most obvious down-regulated after MUC16 knockdown.The downregulation of NTS decreased the invasion and migration of gastric cancer cells.The immunoprecipitation assay showed that JAK2 can specifically bind to the C-terminal of MUC16.The results of Western blot detection analysis showed that MUC16 regulates the expression of NTS through the JAK2-STAT3-cJUN signaling pathway.The detection of circulating tumor cells in gastric cancer patients showed that elevated expression of MUC16 in the primary gastric cancer and lymph node metastasis was positively correlated with the increase of circulating tumor cells.Conclusions: These studies indicate that MUC16 may promote the expression of NTS through JAK2-STAT3-cJUN signaling pathway which leads to enhanced migration and invasion ability of gastric cancer and tumor cells are more likely to enter peripheral blood.This experiment first describes the influence and mechanism of MUC16 on the invasion and metastasis of gastric cancer cells,and provides a new theoretical basis for mucin mediated gastric cancer metastasis.It provides a research basis for the diagnosis and treatment of gastric cancer metastasis.