RESUMO
Objective To investigate the effects of circDNMT1 on the proliferation,apoptosis and epithelial-mesenchymal transition(EMT)of triple-negative breast cancer(TNBC)cells by regulating miR-377-3p/PUM1 axis.Methods The TNBC tissues and adjacent normal tissues of 24 patients with TNBC treated in Danzhou People's Hospital from 2018 to 2021 were collected.qRT-PCR and Western blot were used to detect the expression of circDNMT1,miR-377-3p,and PUM1 protein in tissue and mouse normal breast epithelial cell line HC11 and TNBC cell lines 4T1,Eph41424,and JC.4T1 cells were divided into the 4T1 group(untransfected),the si-NC group(transfected with si-NC),the si-DNMT1 group(transfected with si-DNMT1),the si-DNMT1+anti-NC group(simultaneously transfected with si-DNMT1 and anti-NC),and the si-DNMT1+anti-miR-377-3p group(simultaneously transfected with si-DNMT1 and anti-miR-377-3p).qRT-PCR was used to detect the expression of circDNMT1 and miR-377-3p of 4T1 cells in each group;CCK-8 was used to detect the proliferation of 4T1 cells in each group;flow cytometry was used to detect the apoptosis of 4T1 cells in each group;Western blot was used to detect the expression of PUM1,EMT-related proteins and apoptosis-related proteins of 4T1 cells in each group;TargetScan website was used to predict the binding sites of miR-377-3p with circDNMT1 and PUM1;dual luciferase report was used to verify the targeting relationships of miR-377-3p with circDNMT1 and PUM1.After inoculation with 4T1 cells,BALB/c mice were randomly divided into the blank control group(injected with equal amount of normal saline),the negative control group(injected with si-NC via tail vein),the DNMT1 silencing group(injected with si-DNMT1 via tail vein),the combined control group(injected with si-DNMT1 and anti-NC via tail vein),and the combined silencing group(injected with si-DNMT1 and anti-miR-377-3p via tail vein),the tumor massess of mice were recorded and the morphological changes of tumors were observed by hematoxylin-eosin staining.Results circDNMT1 and PUM1 were up-regulated in TNBC tissues and cells,and miR-377-3p was down-regulated.The expression difference was most obvious in 4T1 cells,so 4T1 cells were selected for subsequent experiments.Compared with the 4T1 group and the si-NC group,the expression of miR-377-3p,the apoptosis rate of 4T1 cells,the expression levels of Bax,cleaved caspase-3 and E-cadherin protein of 4T1 cells in the si-DNMT1 group were significantly increased(P<0.05),the circ-DNMT1 level,the expression level of PUM1 protein,OD values at 24 hours and 48 hours,the expression level of Bcl-2,N-cadherin,Vimentin protein were significantly decreased(P<0.05).Compared with the si-DNMT1 group and the si-DNMT1+anti-NC group,the expression of miR-377-3p,the apoptosis rate of 4T1 cells,the expression levels of Bax,cleaved caspase-3 and E-cadherin proteins of 4T1 cells in the si-DNMT1+anti-miR-377-3p group were significantly decreased(P<0.05),the expression level of PUM1 protein,OD values at 24 hours and 48 hours,the expression levels of Bcl-2,N-cadherin,Vimentin proteins were significantly increased(P<0.05).Compared with the miR-NC+WT-circDNMT1 group,the cell luciferase activity in the miR-377-3p mimic+WT-circDNMT1 group was significantly decreased(P<0.05);compared with the miR-NC+WT-PUM1 group,the cell luciferase activity in the miR-377-3p mimic+WT-PUM1 group was significantly decreased(P<0.05).The tumor cells in the blank control group and the negative control group were densely arranged with clear boundary;the tumor cells in the DNMT1 silencing group and the combined control group were loosely arranged,the nuclei were pyknotic,and the cell fragments were increased;the tumor cells in the combined silencing group were densely arranged and the boundaries tended to be clear.Compared with the blank control group and the negative control group,the tumor mass of mice in the DNMT1 silencing group was significantly decreased(P<0.05).Compared with the DNMT1 silencing group and the combined control group,the tumor mass of mice in the combined silencing group was significantly increased(P<0.05).Conclusion Silencing circDNMT1 may inhibit the expression of PUM1 by up-regulating miR-377-3p,thereby inhibiting the proliferation and EMT of TNBC cells,and promoting cell apoptosis.