MEN1 deficiency leads to neuroendocrine differentiation of lung cancer and disrupts the DNA damage response.

The MEN1 gene, a tumor suppressor gene that encodes the protein menin, is mutated at high frequencies in neuroendocrine (NE) tumors; however, the biological importance of this gene in NE-type lung cancer in vivo remains unclear. Here, we established an ATII-specific KrasG12D/+/Men1-/- driven genetically engineered mouse model and show that deficiency of menin results in the accumulation of DNA damage and antagonizes oncogenic Kras-induced senescence and the epithelial-to-mesenchymal transition during lung tumorigenesis. The loss of menin expression in certain human primary lung cancers correlates with elevated NE profiles and reduced overall survival.

Abnormal expression of menin predicts the pathogenesis and poor prognosis of adult gliomas.

Several brain tumors is closely related to the disorder of chromatin histone modification, whereas the epigenetic mechanisms of the incidence of highly malignant adult glioma is not yet deeply studied. Deletion or mutation of the MEN1 gene, which encodes the epigenetic regulator menin, specifically induces poorly differentiated neuroendocrine tumors; however, the biological and clinical importance of MEN1 in the nervous system remains poorly understood. Menin expression was robustly activated in 44.4% of adult gliomas. Abnormally high expression of menin was closely related to a shorter median survival time of 20 months, a larger tumor volume and a higher percentage of Ki67 staining. Interestingly, menin expression was also activated in the cytoplasm of tumor cells (38.8%) and was also closely related to the poor prognosis of patients with glioma. Importantly, in a screening of 96 types of small-molecule targeted histone modification regulators, menin inhibitors were found to significantly block the proliferation of adult glioma cells. Our findings confirm that menin is a potential biomarker of poor prognosis in adult gliomas, independent of the WHO grade. Targeting menin may effectively inhibit certain gliomas, and this information provides novel insight into therapeutic strategies for glioma.

Epigenetic alterations contribute to promoter activity of imprinting gene IGF2.

The expression of insulin-like growth factor 2 (IGF2), a classical imprinting gene, didn't completely correlate with its imprinting profiles in hepatocellular carcinoma (HCC). The mechanistic importance of promoter activity in regulation of IGF2 has not been fully clarified. Here we show that histone 3 lysine 4 trimethylation (H3K4me3) modified by menin-MLL complex of IGF2 promoter contributes to promoter activity of IGF2. The strong binding of menin and abundant H3K4me3 at the DNA demethylated P3/4 promoters were observed in Hep3B cells with the robust expression of IGF2. In IGF2-low-expressing HepG2 cells, menin didn't bind to DNA hypermethylated P3/4 regions; however, menin overexpression inhibited DNA methylation and promoted H3K4me3 at the P3/4 as well as IGF2 expression in HepG2. In addition, the H3K4me3 at P3/4 locus was activated in primary HCC specimens with high IGF2 expression. Furthermore, inhibition of the menin/MLL interaction via MI-2/3 reduced IGF2 expression, inhibited the IGF1R-AKT pathway, and significantly repressed HCC with robust expression of IGF2. Taken together, we conclude that H3K4me3 of P3/4 locus mediated by the menin-MLL complex is a novel epigenetic mechanism for releasing IGF2.

Reprogramming of histone methylation controls the differentiation of monocytes into macrophages.

Subset heterogeneity of the mononuclear phagocyte system (MPS) is controlled by defined transcriptional networks and programs; however, the dynamic establishment of programs that control broad, orchestrated expression of transcription factors (TFs) during the progression of monocyte-into-phagocyte (MP) differentiation remains largely unexplored. By using chromatin immunoprecipitation assays, we show the extensive trimethylation of histone H3 lysine 4 (H3K4me3) as well as histone H3 lysine 27 (H3K27me3) occupancy with broad footprints at the promoters of MP differentiation-related TFs, such as HOXA and FOXO genes, KLF4, IRF8 and others. The rapid repression of HOXA genes was closely associated with the MP differentiation program. H3K4me3 participates in regulating HOXA genes at mild and terminal differentiation periods, while H3K27me3 maintains low-level expression of HOXA genes at phagocytic maintenance periods. Furthermore, the reprogramming of H3K27me3 plays a major role in the up-regulation of KLF4 and FOXO genes during MP differentiation. Importantly, the pharmacological inhibition of H3K4me3 and/or H3K27me3 strikingly promotes the differentiation programs of THP-1 and K562 cells. Together, these findings elucidate mechanisms crucial to the dynamic establishment of epigenetic memory, which is central to the maintenance of the MP differentiation blockade.

EZH2 represses target genes through H3K27-dependent and H3K27-independent mechanisms in hepatocellular carcinoma.

UNLABELLED: Alterations of polycomb group (PcG) genes directly modulate the trimethylation of histone H3 lysine 27 (H3K27me3) and may thus affect the epigenome of hepatocellular carcinoma (HCC), which is crucial for controlling the HCC cell phenotype. However, the extent of downstream regulation by PcGs in HCC is not well defined. Using cDNA microarray analysis, we found that the target gene network of PcGs contains well-established genes, such as cyclin-dependent kinase inhibitors (CDKN2A), and genes that were previously undescribed for their regulation by PcG, including E2F1, NOTCH2, and TP53. Using chromatin immunoprecipitation assays, we demonstrated that EZH2 occupancy coincides with H3K27me3 at E2F1 and NOTCH2 promoters. Interestingly, PcG repress the expression of the typical tumor suppressor TP53 in human HCC cells, and an increased level of PcG was correlated with the downregulation of TP53 in certain HCC specimens. Unexpectedly, we did not find obvious H3K27me3 modification or an EZH2 binding signal at the TP53 promoters, suggesting that PcG regulates TP53 expression in an H3K27me3-independent manner. Finally, the reduced expression of PcGs effectively blocked the aggressive signature of liver cancer cells in vitro and in vivo. IMPLICATIONS: Taken together, our results establish the functional and mechanistic significance of certain gene regulatory networks that are regulated by PcGs in HCC.

The functional and mechanistic relatedness of EZH2 and menin in hepatocellular carcinoma.

BACKGROUND & AIMS: The alterations of histone modification may serve as a promising diagnostic biomarker of hepatocellular carcinoma (HCC), but the clinical and mechanistic relatedness of the histone H3 lysine 27 and 4 trimethylation (H3K27me3 and H3K4me3) in HCC remains poorly understood. Here we propose that the combination of H3K27me3 and H3K4me3 is a more precise predictive/prognostic value for outcome of HCC patients. METHODS: We used chromatin immunoprecipitation (ChIP) assays and a ChIP-on-chip screen to analyse HCC. RESULTS: We found that the EZH2 occupancy coincides with the H3K27me3 at promoters and directly silences the transcription of target genes in HCC. The H3K27me3-related gene network of EZH2 contains well-established genes, such as CDKN2A, as well as previously unappreciated genes, including FOXO3, E2F1, and NOTCH2, among others. We further observed independently increasing profiles of H3K27me3 and H3K4me3 at the promoters of certain target genes in HCC specimens. Importantly, Kaplan-Meier analysis reveals that 3-year overall and tumour-free survival rates are dramatically reduced in patients that simultaneously express EZH2 and menin, compared to rates in the EZH2 or menin under expressing patients. Furthermore, an inhibitor of H3K27me3 alone, or in combination with an H3K4me3 inhibitor, effectively blocked the aggressive phenotype of HCC cells. CONCLUSIONS: Our results indicate that a combined analysis of both H3K27me3 and H3K4me3 may serve as powerful diagnostic biomarkers of HCC, and targeting both might benefit anti-HCC therapy.