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Objective To investigate the expression and prognostic significance of mediator complex subunit 8 (MED8) in gastric cancer and its impact on the cell cycle.Methods The expression of MED8 in gastric cancer and adjacent tissues and its correlation with patients' prognosis were analyzed using public databases.A validation cohort of 104 patients who underwent radical resection for gastric cancer in the First Affiliated Hospital of Bengbu Medical College from June 2012 to July 2017 was included.The receiver operating characteristic curve was established to evaluate the predictive value of MED8 for postoperative 5-year survival.Bioinformatics tools were used to predict the biological roles of MED8 in gastric cancer.The effect of the MED8 level on the G1/S phase transition of gastric cancer cells (MGC-803) was analyzed via lentivirus transduction and flow cytometry.Western blotting was carried out to assess the impact of MED8 expression on the protein levels of cyclin-dependent kinase 4(Cdk4) and G1/S-specific cyclin-D1(CyclinD1) in MGC-803 cells.Results The high expression of MED8 in the gastric cancer tissue was associated with poor prognosis ( P <0.001) and had prognostic significance (area under curve=0.733, P <0.001).Gene enrichment analysis suggested that MED8 may participate in the cell cycle process.Flow cytometry results revealed that the upregulation of MED8 expression promoted the transition of MGC-803 cells from the G1 phase to the S phase ( P <0.001),while the downregulation of MED8 had the opposite effect ( P <0.001).Western blotting showed increases in the protein levels of Cdk4 and CyclinD1 in MGC-803 cells with upregulated MED8 expression (all P <0.001),and decreases in the cells with downregulated MED8 expression (all P <0.001).Conclusion MED8 is highly expressed in gastric cancer and may affect its progression and prognosis by regulating the G1/S phase transition of gastric cancer cells.

Objective To investigate the expression level of serine/threonine phosphoprotein phosphatase 4C(PPP4C)in gastric cancer,and analyze its relationship with prognosis and the underlying regulatory mechanism.Methods The clinical data of 104 gastric cancer patients admitted to the First Affiliated Hospital of Bengbu Medical College between January 2012 and August 2016 were collected.Immunohistochemical staining was employed to determine the expression levels of PPP4C and Ki-67 in the gastric cancer tissue.The gastric cancer cell lines BGC823 and HGC27 were cultured and transfected with the vector for PPP4C knockdown,the vector for PPP4C overexpression,and the lentiviral vector(control),respectively.The effects of PPP4C on the cell cycle and proliferation were analyzed and the possible regulatory mechanisms were explored.Results PPP4C was highly expressed in gastric cancer( P <0.001),and its expression promoted malignant progression of the tumor(all P <0.01).Univariate and Cox multivariate analysis clarified that high expression of PPP4C was an independent risk factor affecting the 5-year survival rate of gastric cancer patients( P =0.003).Gene ontology and Kyoto encyclopedia of genes and genomes enrichment analysis suggested that PPP4C may be involved in the cell cycle.The correlation analysis showed that the expression of PPP4C was positively correlated with that of Ki-67 in gastric cancer( P <0.001).The up-regulation of PPP4C expression increased the proportion of tumor cells in the S phase,alleviated the G2/M phase arrest,and promoted the proliferation of gastric cancer cells and the expression of cyclin D1 and cyclin-dependent kinase 6(CDK6)(all P <0.05).The down-regulation of PPP4C decreased the proportion of gastric cancer cells in the S phase,promoted G2/M phase arrest,and inhibited cell proliferation and the expression of cyclin D1,CDK6,and p53(all P <0.05).p53 inhibitors promoted the proliferation of BGC823 and HGC27 cells in the PPP4C knockdown group( P <0.001, P <0.001),while p53 activators inhibited the proliferation of BGC823 and HGC27 cells in the PPP4C overexpression group( P <0.001, P =0.002).Conclusions PPP4C is highly expressed in gastric cancer and affects the prognosis of the patients.It may increase the proportion of gastric cancer cells in the S phase and alleviate the G2/M phase arrest by inhibiting p53 signaling,thereby promoting cell proliferation.

Objective: To investigate the prognostic value of the expression of myeloid leukemia factor 1-interacting protein (MLF1IP) in gastric cancer tissue and its regulatory role in tumor progression., Methods: Gene Expression Omnibus (GEO) database was used to analyze the expression level of MLF1IP in tumor tissues of gastric cancer patients. Kaplan-Meier Plotter database was used to analyze the relationship between MLF1IP expression level and patient prognosis. We conducted a retrospective analysis of 108 gastric cancer patients who had undergone radical surgery at our hospital between January 2015 and December 2015. The expression of MLF1IP in gastric cancer tissue and adjacent tissues was examined. We analyzed the relationship between MLF1IP and the clinicopathological parameters of gastric cancer patients and its impact on the long-term prognosis of gastric cancer patients. Univariate and multivariate regression analyses were done to identify the risk factors affecting the long-term prognosis of gastric cancer patients. The assessment value of MLF1IP for long-term prognosis of gastric cancer was analyzed with ROC curve. The effects of MLF1IP on the proliferation, migration, and invasion of gastric cancer cells were analyzed in vitro with gastric cancer cell line (MGC803). A xenograft tumor model was established with nude mice to analyze in vivo the effect of MLF1IP on tumor growth., Results: The results of the gastric cancer cohort GSE29272 of GEO database showed that the expression level of MLF1IP in gastric cancer tissues was significantly higher than that in normal tissues ( P <0.05). Analysis with Kaplan-Meier Plotter database indicated that high MLF1IP expression was correlated with poor prognosis in gastric cancer patients. Immunohistochemical analysis showed that the expression level of MLF1IP in gastric cancer tissues was higher than that in adjacent tissues ( P <0.05). Correlation analysis showed that the MLF1IP level in gastric cancer tissue was positively correlated with Ki67 ( r =0.609, P <0.01), peripheral blood carcinoembryonic antigen (CEA) ( r =0.572, P <0.01) and carbohydrate antigen 19-9 (CA19-9) ( r =0.623, P <0.01). Kaplan-Meier (K-M) survival analysis showed that the 5-year survival rate of patients in the MLF1IP high expression group was significantly lower than that in the MLF1IP low expression group ( P <0.01). Cox regression analysis showed that independent risk factors for 5-year survival after radical gastrectomy for gastric cancer included the expression of MLF1IP ( HR =2.508, 95% CI : 1.259-4.999), CEA≥5 μg/L ( HR =2.171, 95% CI : 1.152-4.092), CA19-9≥37 kU/L ( HR =2.401, 95% CI : 1.094-5.269), and T3-T4 stages ( HR =2.779, 95% CI : 1.049-7.358) and N2-N3 stages ( HR =2.072, 95% CI : 1.100-3.904). ROC analysis showed that the sensitivity, specificity, and accuracy of MLF1IP (the cut-off value was 3.00 relative protein expression level) in assessing the 5-year survival rate after radical gastrectomy for gastric cancer was 75.00%, 76.92%, and 76.2%, respectively ( P <0.05). CCK-8, Transwell assay, and scratch assays showed that in vitro knocking down of MLF 1 IP gene expression significantly inhibited the proliferation, migration and invasion of gastric cancer cells. Subcutaneous tumor xenograft experiment in nude mice showed that knocking down MLF 1 IP gene significantly inhibited tumor growth., Conclusion: Increased expression of MLF1IP in gastric cancer tissue, which may be involved in the malignant activities of proliferation, migration, and invasion of gastric cancer cells, has a certain predictive value for poor prognosis., (Copyright© by Editorial Board of Journal of Sichuan University (Medical Sciences).)