Forkhead Box M1 Regulates the Proliferation,Invasion,and Drug Resistance of Gastric Cancer Cells via circ_NOTCH1

Abstract

Objective To investigate the impacts of forkhead box M1(FOXM1)on the proliferation,invasion,and drug resistance of gastric cancer cells by regulating the circular RNA circ_NOTCH1.Methods Western blotting and real-time quantitative PCR were performed to determine the expression of FOXM1 protein and circ_NOTCH1,respectively,in the gastric cancer tissue,para-carcinoma tissue,human normal gastric mucosa epithelial cell line GES-1 and gastric cancer cell lines MGC-803,HGC-27,and BGC-823.BGC-823 cells were classified into the following groups:control,short hairpin RNA FOXM1(sh-FOXM1)and negative control(sh-NC),small interfering RNA circ_NOTCH1(si-circ_NOTCH1)and negative control(si-NC),and sh-FOXM1+circ_NOTCH1 overexpression plasmid(sh-FOXM1+pcDNA-circ_NOTCH1)and sh-FOXM1+negative control(sh-FOXM1+pcDNA).CCK-8 assay and clone formation assay were employed to measure the cell proliferation,and Transwell assay to measure cell invasion.After treatment with 1.0 mg/L adriamycin for 48 h,the cell resistance in each group was analyzed.Western blotting was employed to determine the expression levels of FOXM1,proliferating cell nuclear antigen(PCNA),Bax,multi-drug resistance-associated protein 1(MRP1),and multi-drug resistance gene 1(MDR1).RNA pull-down and RNA immunoprecipitation were employed to examine the binding of circ_NOTCH1 to FOXM1 protein.Results Compared with those in the para-carcinoma tissue,the expression levels of FOXM1 protein and circ_NOTCH1 in the gastric cancer tissue were up-regulated(all P<0.001).Compared with GES-1 cells,MGC-803,HGC-27,and BGC-823 cells showed up-regulated expression levels of FOXM1 protein and circ_NOTCH1(all P<0.001).Compared with the control group and sh-NC group,the sh-FOXM1 group with down-regulated expression of FOXM1 protein and circ_NOTCH1 showed decreased optical density value,clone formation rate,cell invasion number,and cell viability,down-regulated expression of PCNA,MRP1,and MDR1,and up-regulated expression of Bax protein in BGC-823 cells(all P<0.001).Compared with the control group and the si-NC group,the si-circ_NOTCH1 group with down-regulated expression of circ_NOTCH1 showed decreased optical density value,clone formation rate,cell invasion number,and cell viability,down-regulated expression of PCNA,MRP1,and MDR1,and up-regulated expression of Bax protein in BGC-823 cells(all P<0.001).Compared with sh-FOXM1 group and sh-FOXM1+pcDNA group,the sh-FOXM1+pcDNA-circ_NOTCH1 group with up-regulated expression of circ_NOTCH1 showed increased optical density value,clone formation rate,cell invasion number,and cell viability,up-regulated expression of PCNA,MRP1,and MDR1,and down-regulated expression of Bax protein(all P<0.001).FOXM1 protein was able to interact with circ_NOTCH1.Conclusion Interference with FOXM1 may inhibit the proliferation,invasion,and drug resistance of gastric cancer cells by silencing circ_NOTCH1 expression.