| Background and Objection:As a member of DUB family,deubiquitin specific enzyme USP3 can stabilize and increase the intracellular level of the protein through ubiquitin regulation,which may play an important role in the occurrence and development of tumor.The imbalance of USP3 expression is closely related to cervical cancer and colorectal cancer.As a member of PcG family,SUZ12(Suppressor of Zeste 12 Protein Homolog)plays an important role in the occurrence and development of many kinds of tumors.Recent studies have shown that SUZ12 protein is highly expressed in gastrointestinal tumors,and low expression in normal tissues or even not expressed.In gastric cancer,the upregulation of SUZ12 inhibits the expression of KLF2 and E-cadherin,thus promoting the proliferation and metastasis of gastric cancer cells.At present,there is little research on the interaction mechanism between USP3 and SUZ12 in gastrointestinal tumors.The purpose of this study was to study the interaction between USP3 and SUZ12 in gastric cancer,to evaluate the effect of USP3 expression on the prognosis of gastric cancer,and to provide evidence for exploring new therapeutic targets for gastric cancer.Methods:1.Immunohistochemical method was used to detect the expression of USP3 in gastric cancer tissues and normal tissues,and the relationship between USP3 and case characteristics and prognosis of gastric cancer patients.2.USP3 stable overexpression cell line was constructed.Transwell invasion experiment,cell scratch experiment and immunofluorescence assay were constructed to detect the effect of USP3 on EMT,invasion and metastasis of gastric cancer cells.3.C ell invasion assay,wound healing assay were used to research whether USP3 is involved in the TGF-β1 induced EMT in colorectal cancer cells and the possible mechanism or signaling pathway.4.The model of caudal vein metastasis in nude mice was established.The expression of E-cadherin was detected by immunohistochemistry and qRT-PCR method.The effect of overexpression of USP3 on metastasis of gastric cancer in vivo was studied.5.In order to further confirm the localization relationship between USP3 and SUZ12 in gastric cancer cells,immunofluorescence assay was carried out.6.At the same time,immunoprecipitation assay was used to verify the interaction between USP3 and SUZ12,and to study the correlation between their expression in cells.7.Scratch assay and Transwell cell invasion assay were used to investigate the effect of down-regulation of SUZ12 on the invasion and metastasis of gastric cancer cells induced by USP3.8.Lymph nodes were collected from patients with lymph node metastasis of colorectal cancer.Immunohistochemistry was used to verify the expression of USP3 and SUZ12 in colorectal cancer patients with lymph node metastasis.Results:1.The expression of USP3 in gastric cancer tissues is higher than that in corresponding normal tissues,and the high expression of USP3 is closely related to the poor prognosis of tumor patients.2.USP3 can promote EMT,invasion and metastasis of gastric cancer cells.3.TGF-β1 can induce USP3 expression,and USP3 gene knockout could inhibit EMT induced by TGF-β1.4.USP3 interacts with SUZ12 through deubiquitin and maintains its stability.5.SUZ12 gene knockout inhibited the migration and invasion of gastric cancer cells induced by USP3.6.The expression of USP3 is positively correlated with the expression of SUZ12 protein,while the expression of USP3 or SUZ12 protein is negatively correlated with the expression of E-cadherin protein.Conclusion:USP3 and SUZ12 have synergistic effect on EMT,invasion and metastasis of gastric cancer cells.Therefore,USP3 and SUZ12 may be the target genes for the comprehensive treatment of gastric cancer. |
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