Search

PDF file - 484K, S1. The efficiency of EZH2 and SUZ12 silencing by shRNA. S2. EZH2 repress TP53 expression in HCC cells. S3. PcG regulated P53 expression through H3K27me3 in an independent manner. Supplemental Table 1. The list of antibodies used in the study. Supplemental Table 2. The list of primers used in the study. Supplemental Table 3. The list of top 200 genes differentially regulated by PcG.

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.

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.

Multiple endocrine neoplasia type 1 (MEN1), a human familial tumor syndrome, results from mutations in the Men1 gene. Although much progress has been made in demonstrating the definitive role for menin in suppressing tumorigenesis in endocrine organs, the molecular pathways responsible for menin action in normal tissues and tumors remain poorly defined. Here, we review the recent progress on the molecular functions of menin in controlling cell proliferation, apoptosis, and DNA repair. The majority of these functions are largely executed by menin-mediated influencing of histone modifications and chromatin structure. These findings lead to a new model of understanding menin's tumor-suppressing function, providing insights into understanding of how menin regulates cell proliferation and the development of endocrine tumors. The new knowledge could also be translated into new strategies to improve therapeutic interventions against MEN1 and other endocrine diseases including diabetes.

Although the abnormal expression of Polycomb-group (PcG) proteins is closely associated with carcinogenesis and the clinicopathological features of hepatocellular carcinoma (HCC), the genetic mutation profile of PcG genes has not been well established. In this study of human HCC specimens, we firstly discovered a highly conserved mutation site, G553C, in the Polycomb Repressive Complex 2 (PRC2) gene enhancer of zeste homolog 2 (EZH2). This site also harbors a single nucleotide polymorphism (SNP), rs2302427, which plays an important antagonistic role in HCC. Kaplan-Meier survival curves showed that the tumor-free and overall survival of patients with EZH2 G553C were superior to those without the mutation. The G allele frequencies in patients and healthy subjects were 0.2% and 0.122%, respectively, with significant differences in distribution. The individuals carrying the GG and the GC genotypes at rs2302427 showed 3.083-fold and 1.827-fold higher risks of HCC, respectively, compared with individuals carrying the wild-type allele. Furthermore, Immunohistochemical staining revealed that the expression levels of CBX8 (in 53/123 samples) and BMI1 (in 60/130 samples) were markedly increased in human HCC specimens. Importantly, the overall and tumor-free survival rates were significantly reduced in the group of patients who simultaneously expressed PRC1 and PRC2. These results argue that a combination of PRC1 and PRC2 expression has a significant predictive/prognostic value for HCC patients. Taken together, our results indicate the abnormal expression and genetic mutation of PcG members are two independent events; cumulative genetic and epigenetic alterations act synergistically in liver carcinogenesis.

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. Visual Overview: http://mcr.aacrjournals.org/content/12/10/1388/F1.large.jpg. Mol Cancer Res; 12(10); 1388–97. ©2014 AACR.

Significance Epigenetic changes commonly occur in hepatocellular carcinoma (HCC) and are associated with aberrant gene expression. Most studies have focused on epigenetic gene-silencing events; therefore, the mechanism that promotes gene activation in HCC is not well established. We identify an epigenetic activation mechanism whereby menin promotes Yes-associated protein (Yap1) transcription, which is associated with a poor prognosis for HCC patients. Substantial overexpression of the menin–mixed-lineage leukemia complex is associated with increased histone 3 lysine 4 trimethylation at certain loci of the tumor promoter in HCC. Heterozygous ablation of multiple endocrine neoplasia type 1 ( Men1) in mice reduces diethylnitrosamine-induced development of HCC. Our findings reveal that menin plays an important epigenetic role in up-regulating Yap1 transcription, leading to liver tumorigenesis.

MEN1, which encodes the nuclear protein menin, acts as a tumor suppressor in lung cancer and is often inactivated in human primary lung adenocarcinoma. Here, we show that the inactivation of MEN1 is associated with increased DNA methylation at the MEN1 promoter by K-Ras. On one hand, the activated K-Ras up-regulates the expression of DNA methyltransferases and enhances the binding of DNA methyltransferase 1 to the MEN1 promoter, leading to increased DNA methylation at the MEN1 gene in lung cancer cells; on the other hand, menin reduces the level of active Ras-GTP at least partly by preventing GRB2 and SOS1 from binding to Ras, without affecting the expression of GRB2 and SOS1. In human lung adenocarcinoma samples, we further demonstrate that reduced menin expression is associated with the enhanced expression of Ras (p0.05). Finally, excision of the Men1 gene markedly accelerates the K-Ras(G12D)-induced tumor formation in the Men1(f/f);K-Ras(G12D/+);Cre ER mouse model. Together, these findings uncover a previously unknown link between activated K-Ras and menin, an important interplay governing tumor activation and suppression in the development of lung cancer.

Menin encoded by the multiple endocrine neoplasia type 1 (MEN1) gene is associated with chromatin and the nuclear matrix and exerts multiple biological functions including regulation of cell proliferation and adhesion. Men1 mutations increase the likelihood of lung cancer development in mice. Menin expression is reduced in certain human non-small cell lung cancer cells, and reduction of menin is closely correlated with increased lung cancer metastasis to lymph nodes. However, it is poorly understood whether menin affects migration of lung cancer cells. In this study, we show that menin-regulated A549 lung cancer cell migration, which was mediated by growth factor pleiotrophin (PTN) and its cell surface receptor, protein tyrosine phosphatase beta/zeta (RPTP β/ζ). Ectopic menin expression significantly repressed PTN transcription, but indirectly inhibited RPTP β/ζ expression through repressing PTN expression. Further studies revealed that menin-regulated cell migration through PTN/RPTP β/ζ, in conjunction with integrin α(v)β(3), focal adhesion kinase, phosphatidylinositol 3-kinase and phosphorylated extracellular signal regulated kinase 1/2. These findings provide mechanistic insights into the molecular basis for menin/PTN-mediated regulation of A549 lung cancer cell migration.

Menin upregulates transcription of cell-cycle inhibitors to suppress endocrine tumors, but it is poorly understood how menin suppresses non-endocrine tumors such as lung cancer. Here, we show that menin inhibits proliferation of human lung cancer cells and growth of lung cancer in mice. The menin-mediated tumor suppression requires repression of growth factor pleiotrophin (PTN), which binds to its cell surface receptor, anaplastic lymphoma kinase (ALK) that is activated in certain lung adenocarcinomas. Menin represses PTN transcription and PTN-induced proliferation of human lung cancer cells, and menin expression is substantially reduced in primary human lung adenocarcinomas. Notably, menin binds the PTN locus and enhances Polycomb gene Enhancer of Zeste homolog 2 (EZH2)-mediated histone H3 lysine 27 trimethylation (H3K27m3), a negative mark for gene transcription but does not affect histone H3K4 methylation that is usually upregulated by menin in endocrine cells. Together, our findings indicate that menin suppresses lung cancer partly through increasing Polycomb gene-mediated H3K27 methylation and repressing PTN transcription, unraveling a novel, epigenetically regulated PTN-ALK signaling pathway in suppressing lung cancer.

Starting from a commercially available block copolymer, polystyrene-b-polybutadiene-b-polystyrene (SBS), micro-patterned polymer films were successfully prepared by evaporating SBS/carbon disulfide solutions with different concentrations under high humidity. The influence of solution concentration on the pore size and array was investigated in detail. With the increase of solution concentration, regular pore arrays turned into random because of weakened convention. Once the concentration was more than 60 mg mL−1, a bimodal size distribution appeared. Photo-chemical cross-linking was achieved by exposing the polymer films in deep UV light (wavelength = 254 nm), monitored by attenuated total reflective Fourier transform infrared and X-ray photoelectron spectroscopy. After 1 h cross-linking, either solvent resistance or thermal stability or surface wettability of the films was significantly improved. The cross-linked honeycomb structured films became resistant to a wide range of organic solvents and thermally stable up to 350 °C, an increase of more than 250 K as compared to the un-crosslinked films. Another beneficial effect of the photo-chemical process was the formation of polar groups on the film surface, changing surface wettability from hydrophobicity to hydrophilicity, enhanced by the micro-patterned surface. The resultant films were non-cytotoxic and hence suitable as cell scaffolds. It was found that hydrophilic, micro-patterned polymer films with a uniform pore size of 3 µm facilitated cell attachment and proliferation.