| Background:Gastric cancer is one of the most common malignant tumors in the world.China is also a high-incidence country for gastric cancer.Gastric cancer is a process of interaction between genetic factors and environmental factors.The pathogenesis of gastric cancer is complex,which has not been fully studied.Bromodomain4(BRD4)is a member of bromodomain and Extra-Terminal domain(BET)family.It has been found that the expression of BRD4 is increased in gastric cancer tissues,and BRD4 plays an important role in tumor proliferation and metastasis.BRD4 inhibitors can inhibit the malignant proliferation of tumor cells.As the first BRD4 inhibitor,JQ1 has high affinity and specificity to BRD4.it can bind to the acetylated binding site of BRD4 and inhibit the expression of BRD4.Some studies have shown that JQ1 can down-regulate the expression of c-Myc in gastric cancer cells,thereby inhibiting cell proliferation and migration.However,the specific mechanism is still unclear.Far Upstream Element Binding Protein 1(FUBP1)is a transcriptional regulator of c-Myc.Its expression is high in gastric cancer,and can affect cell proliferation and migration.Therefore,the role of FUBP1 in inhibiting the proliferation and migration of gastric cancer cells by JQ1 remains to be further studied.Objective:To investigate the role of BRD4 inhibitor JQ1 in inhibiting the proliferation and migration of gastric cancer cells by down-regulating the expression of transcription factor FUBP1 and further inhibiting the expression of c-Myc.It provides a scientific evidence for the mechanism of BRD4 inhibitor JQ1 in the treatment of gastric cancer,and also provides a theoretical basis for BRD4 and FUBP1 as potential intervention targets in clinical treatment.Methods:1.mRNA and protein were extracted from 66 pairs of gastric cancer and adjacent tissues.The expression of BRD4 and FUBP1 in gastric cancer tissues was detected by RT-qPCR,Western blot and immunohistochemistry.The correlation between two genes and clinicopathological characteristics was analyzed.2.The expression of BRD4,FUBP1,c-Myc was detected by Western blot after treatment with JQ1,cell proliferation was detected by CCK-8 and cell clone formation assay,and cell migration was detected by cell scratch assay and Transwell.3.After transfection of FUBP1 siRNA into gastric cancer cells,the expression of FUBP1,c-Myc mRNA and protein were detected by RT-qPCR and Western blot.4.After transfection of BRD4 siRNA into gastric cancer cells,the expression of BRD4,FUBP1,c-Myc mRNA and protein was detected by RT-qPCR and Western blot.Luciferase activity was detected after FUBP1 promoter plasmid and BRD4 siRNA co-transfecting into gastric cancer cells.Results:1.The expression of BRD4 in gastric cancer tissues was higher than that in adjacent tissues(mRNA expression were 2.85±1.96 and 1.31±1.42,P=0.001).The expression of FUBP1 in gastric cancer tissue was higher than that in adjacent tissues(mRNA expression were 13.57±18.40 and 7.71±7.47,P=0.03),and was correlated with the tumor size and TNM stage(P=0.02,P=0.009).The GEO database analysis showed that the survival rate of patients with high FUBP1 expression was lower than that with low FUBP1 expression.2.After treatment with JQ1,the expression of BRD4,FUBP1,c-Myc were decreased,the number of cell proliferation was decreased,and the migration ability was decreased.After transfection of FUBP1 siRNA,the mRNA and protein expression of c-Myc were decreased,and the proliferation and migration ability of gastric cancer cells were decreased.4.The mRNA and protein expression of FUBP1,c-Myc decreased after transfection of BRD4 siRNA.Compared with transfection of NC siRNA,the luciferase activity of FUBP1 promoter was decreased after transfection of BRD4 siRNA.Conclusion:The expression of BRD4 and FUBP1 is increased in gastric cancer.The high expression of FUBP1 indicates poor prognosis,and is related to tumor size and TNM stage.BRD4 inhibitor JQ1 can inhibit the expression of c-Myc by down-regulating the expression of FUBP1,and inhibit cell proliferation and migration. |
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