The Effect and Mechanism of Action of UHRF1 Promotes the Malignant Phenotypes of Breast Cancer Cells by Inactivating EGR1/TNFAIP3/NF-κB Axis

Abstract

Background: As a member of RING (Really Interesting New Gene)-finger type E3 ubiquitin ligases, ubiquitin-like with plant homeodomain (PHD) and Ring Finger domains 1 (UHRF1) exerts its functions as a key epigenetic regulator for target genes by mediating histone deacetylation and DNA methylation. Several evidences indicate UHRF1 as an oncogene in multiple cancer types. Here, the aim of this study was to explore the action and mechanism of UHRF1 in breast cancer (BRCA), so as to elucidate the unclear effect of UHRF1 in BRCA. Methods: The TCGA database was used to detect UHRF1 expression in BCRA tissues and BCRA subclasses; 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assays, colony formation assays, in vitro cell motility assays, Annexin V & propidium iodide staining were used to detect the proliferation, invasion, migration and apoptosis of MDA-MB-231 and NDA-MB-468 cells after UHRF1 transfection or silencing; Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) functional pathway enrichment analysis, combined with RNA-seq and differentially expressed gene analysis to screen for differentially expressed genes after UHRF1 overexpression; Western blotting, qRT-PCR (Real-time polymerase chain reaction) and immunohistochemistry (IHC) were used to verify the expression of UHRF1, N-cadherin, E-cadherin, early growth response factor 1 (EGR1) and TNF-alpha-induced protein 3 (TNFAIP3). Results: UHRF1 expression level is highest in TNBC (a subclass of BRCA) (p < 0.01), while patients with higher UHRF1 expression had significantly lower overall survival. UHRF1 can drive BRCA progression by promoting cancer proliferation and metastasis. The study also identified EGR1 and TNFAIP3 as potential target genes of UHRF1 using RNA sequencing, which was validated by cellular assays and immunohistochemistry data from BRCA tissues. In addition, the study further identified UHRF1 as supporting EGR1, through methylation epigenetic pathway, as 5-aza could effectively recover its expression. Rescue experiments using ectopic expression of EGR1 not only attenuated the effect of UHRF1 (p < 0.01, p < 0.05), but also upregulated TNFAIP3 expression accompanying with inactivation of the NF-κB signaling pathway (p < 0.01, p < 0.05). Conclusions: UHRF1 plays an important role in BRCA progression by promoting cell proliferation and motility, accelerating colony formation, and inducing epithelial-mesenchymal transition (EMT) by inhibiting EGR1 and TNFAIP3 through DNA methylation modifications. Therefore, UHRF1 may be a novel potential therapeutic strategy for BRCA.