Enhancer of zeste homolog 2 (EZH2), a subunit of polycomb repressive complex 2, is a histone methyl-transferase and is considered to work cooperatively with histone deacetylases (HDACs) in the same protein complex to mediate gene transcription repression by increasing histone H3 Lys27 trimethylation (H3K27me3), in particular in the nucleosome (s). EZH2 is overexpressed in numerous types of cancer, including triple negative breast cancer (TNBC), a subtype of breast cancer, which there are no effective treatment options for. Thus, inhibition of EZH2 may be harnessed for targeted therapy of this disease. The present study demonstrated that co-treatment with an EZH2 inhibitor and a HDAC inhibitor additively induced apoptosis in two TNBC cell lines, namely MDA-MB-231 and MDA-MB-436. The increased rate of cell death was associated with an elevation of B cell lymphoma-2 like 11 (BIM) expression level, a pro-apoptotic protein at the protein and mRNA expression levels in these two cell lines. The expression of forkhead box O1 (FOXO1), a known upstream transcriptional activator of BIM, was upregulated in both cell lines by the HDAC inhibitor, and the effect was more pronounced in MDA-MB-436 cells with higher phosphorylation levels of protein kinase B, a negative regulator of FOXO1, compared with MDA-MB-231 cells. Conversely, FOXO1 expression was inhibited following treatment with the EZH2 inhibitor, suggesting that EZH2 and HDAC inhibitors induced BIM expression via a FOXO1-independent mechanism. The present study further revealed that the EZH2 inhibitor, but not the HDAC inhibitor, induced high levels of H3K27 acetylation (H3K27ac) in the BIM promoter. By contrast, compared with the effect of the EZH2 inhibitor, HDAC inhibitor treatment resulted in an increase in H3K27ac at two BIM enhancers. Collectively, the results of the present study indicated that EZH2 and HDACs act differentially on H3K27ac levels in the nucleosome at the promoter and enhancer regions of the BIM gene. Through the upregulation of BIM, co-treatment with EZH2 and HDAC inhibitors had a pronounced therapeutic effect on TNBC cells, suggesting that co-targeting EZH2 and HDAC proteins represents a viable therapeutic option for the treatment of TNBC.
Pubmed ID: 29113202 RIS Download
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A software for acquiring and analyzing flow cytometry data. The user can create plots with elements like regions, gates, statistics, markers, and annotated text. The software can also be used for batch analysis or quality control of analysis. Results can be exported and saved.
View all literature mentionsPortal to interactively visualize genomic data. Provides reference sequences and working draft assemblies for collection of genomes and access to ENCODE and Neanderthal projects. Includes collection of vertebrate and model organism assemblies and annotations, along with suite of tools for viewing, analyzing and downloading data.
View all literature mentionsCell line MDA-MB-436 is a Cancer cell line with a species of origin Homo sapiens (Human)
View all literature mentionsCell line MDA-MB-231 is a Cancer cell line with a species of origin Homo sapiens (Human)
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