| Some proteins or lipids in mammalian cells can be glycosylated, and the end of the glycochain was usually sialylated. Sialic acid, a kind of nine-carbon sugar, was reported to be aberrantly expressed on cell surfaces of various tumors. As it is generally known that sialic acid is positively correlated with tumor invasion and metastasis, it could be served as a potential tumor marker. Sialyltransferase(ST) and sialidase(SA) are the main enzymes responsible for sialic acid metabolism. ST is responsible for the addition of sialic acid, while SA for the removal of it, both to the terminal of glycan, glycoprotein or glycolipids. A total of four kinds of sialidase(Neu1, 2, 3, 4) were found in the mammalian, among which the expression of Neu1 was the highest. And recently it was found that Neu1 plays an important role in many kinds of tumor cells. Therefore, the study of Neu1 may provide a certain theoretical basis for the diagnosis and treatment of tumor due to its function to hydrolyze sialic acids.In order to study the role of Neu1 in tumor development, five bladder cancer cell lines(HCV29, KK47, YTS-1, J82 and T24) were used in this study as cell models for bladder carcinoma. Firstly, the expression of sialic acids, sialidases and sialyltransferases in these cell lines were detected by the lectin staining and specific fluorogenic substrate assays. And then, related sialidases and sialyltransferases were measured by florescence quantitative PCR assay on the genetic level. Our results showed highly invasive cell lines express higher level of sialic acids and lower level of sialidase activity than the normal bladder epithelial cell line HCV29. However, for further experiments, such expression rankings are reconfirmed by semi quantitative and RT-PCR, Western blotting and cyto-immunofluorescene staining technique at the m RNA and protein expression level respectively, the level of Neu1 in HCV29 cells was the highest among all the cell lines, in addition to which results of bladder cancer tissue microarray also confirmed that the expression of Neu1 in cancer tissue was lower than that in normal tissue. Furthermore, in this study, the transformation growth factor(TGF-β) was added into three kinds of cells with relatively high expression of Neu1(HCV29, KK47 and J82) to induce epithelial to mesenchymal transition(EMT) which is considered to play a critical role in progression of tumor migration and invasion. Results showed the expression of Neu1 was significantly down-regulated, which was consistent with the previous experimental data. And then by stable transfection of Neu1 in bladder cancer cells YTS-1 and T24, this study found a decreased cell adhesion, proliferation ability and enhanced apoptosis. Besides also testing the expression of Toll like receptors in the untreated cells(HCV29, KK47 and YTS-1) and TGF-β treated HCV29 cells, found that the change trend of TLR3 was consistent with Neu1. Whereas overexpression of Neu1, the expression of TLR3 was increased and its downstream related NF-κB signaling pathway was activated.In conclusion, this paper evaluated the relevance of Neu1 expression and bladder cancer development, demonstrated the proliferation and apoptosis of bladder cancer cells influenced by high expression of Neu1; and investigated the expression of TLR3 and some related downstream signaling pathways regulated by Neu1. The study demonstrated that Neu1 effectively inhibited bladder tumor development and progression, and our research provided theoretical basis for the clinical diagnosis and treatment of bladder cancer. |
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