Menin Expression Research Articles

Human Proislet Peptide Promotes Pancreatic Progenitor Cells to Ameliorate Diabetes Through FOXO1/Menin-Mediated Epigenetic Regulation.

We investigated how human proislet peptide (HIP) regulates differentiation of human fetus-derived pancreatic progenitor cells (HFPPCs) and explored the potential link between HIP signaling and the menin pathway, which is key to regulating pancreatic islet differentiation. The data show that HIP promoted expression of proislet transcription factors (TFs), including PDX-1, MAFA, and NKX6.1, as well as other maturation markers of β-cells, such as insulin, GLUT2, KIR6.2, SUR1, and VDCC. Moreover, HIP increased insulin content and promoted the ability of HFPPCs to normalize blood glucose in diabetic mice. HIP inhibited the TF FOXO1 by increasing AKT-mediated phosphorylation. HIP-induced repression of FOXO1 suppressed menin expression, leading to reducing menin binding to the promoter of the three key proislet TFs, decreasing recruitment of H3K9 methyltransferase SUV39H1, and thus reducing repressive H3K9me3 at the promoter. These coordinated actions lead to increased expression of the proislet TFs, resulting in induction of HFPPC differentiation. Consistently, constitutive activation of FOXO1 blocks HIP-induced transcription of these TFs. Together, these studies unravel the crucial role of the HIP/AKT/FOXO/menin axis in epigenetically controlling expression of proislet TFs, regulating the differentiation of HFPPCs, and normalizing blood glucose in diabetic mice.

MiR‑24 may be a negative regulator of menin in lung cancer.

The incidence of lung cancer in China increases annually, and effective targets for the diagnosis and treatment of lung cancer are urgently needed. miRNAs are currently considered to be involved in the regulation of tumor development and growth. miR‑24has been found to contribute to the development of several tumors. Menin is a key tumor suppressor gene, and its expression is generally low in lung cancer. The effects of miR‑24 on the biological behavior of lung cancer cells were detected by MTT and Transwell assays. In the present study, miR‑24 was found to be associated with menin, affecting the activity of the SMAD3 pathway in lung cancer by inhibiting menin expression. miR‑24 may promote the growth and metastasis and inhibit the apoptosis of lung cancer cells by targeting menin. Therefore, the aim of the present study was to provide a new theoretical basis for the targeted therapy of lung cancer.

Menin Modulates Mammary Epithelial Cell Numbers in Bovine Mammary Glands Through Cyclin D1

Menin, the protein encoded by the MEN1 gene, is abundantly expressed in the epithelial cells of mammary glands. Here, we found MEN1/menin expression slowly decreased with advancing lactation but increased by the end of lactation. It happened that the number of bovine mammary epithelial cells decreases since lactation, suggesting a role of menin in the control of mammary epithelial cell growth. Indeed, reduction of menin expression through MEN1-specific siRNA transfection in the bovine mammary epithelial cells caused cell growth arrest in G1/S phase. Decreased mRNA and protein expression of Cyclin D1 was observed upon MEN1 knockdown. Furthermore, menin was confirmed to physically bind to the promoter region of Cyclin D1 through a ChIP assay, indicating that menin plays a regulatory role in mammary epithelial cell cycle progression. Moreover, lower expression of MEN1/menin induced increased epithelial cell apoptosis and caused extracellular matrix remodeling by down-regulating its associated genes, such as DSG2 and KRT5, suggesting that menin’s role may also be involved in the control of cell–cell adhesion in normal mammary glands. Taken together, our data revealed an unknown molecular function of menin in epithelial cell proliferation, which may be important in the regulation of lactation behavior of mammary glands.

Abstract 5835: Oncogenic activation of the serine synthesis pathway by the scaffolding protein menin

Abstract Developmental transcription programs are epigenetically regulated by multi-protein complexes including the MLL-containing trithorax (TrxG) complexes, which methylate H3K4 to promote gene transcription. We recently reported that the TrxG protein MLL1 and its binding partner menin are overexpressed by and function as oncogenes in Ewing sarcoma. Moreover, small molecule inhibition of the menin-MLL1 protein-protein interaction leads to loss of menin and MLL1 protein expression and to inhibition of growth and tumorigenicity. For the current study we investigated the mechanistic basis of menin-MLL1 mediated oncogenic activity in Ewing sarcoma. Bru-seq analysis was performed to identify changes in nascent gene transcription in Ewing sarcoma cells following exposure to the menin-MLL interaction inhibitor MI-503. Identified targets were validated by qRT-PCR, western blot, immunocytochemistry and by interrogation of published databases. Loss of function was achieved by lentiviral shRNAs and by inhibitor treatment. Exposure of three independent Ewing sarcoma cell lines to MI-503 resulted in significant and reproducible modulation of nearly 100 genes. Bioinformatics analysis of MI-503-regulated genes revealed that the serine synthesis pathway (SSP) was the most significantly impacted pathway downstream of MI-503 treatment. The SSP has recently emerged as a major mediator of tumorigenicity in multiple human cancers. qRT-PCR confirmed reduced expression of SSP enzyme-encoding genes PHGDH, PSAT1 and PSPH in MI-503 treated cells. To determine if the SSP contributes to Ewing sarcoma pathogenesis we evaluated expression of SSP genes and proteins in tumors and cell lines. Our findings showed that Ewing sarcomas express high levels of PHGDH, PSAT1, and PSPH and interrogation of the Cancer Cell Line Encyclopedia revealed that PHGDH expression is higher in Ewing sarcoma than in any other cancer in the database. Studies of Ewing sarcoma cells in serine and glycine free media showed that cells retain viability but that exposure to the PHGDH inhibitor, CBR-5884, inhibits survival in both standard and serine/glycine-free conditions, confirming the importance of the pathway to tumor pathogenesis. To determine how menin-MLL1 promote SSP activation we performed loss of function studies and discovered that knockdown of menin, but not of MLL1, leads to a significant reduction in SSP gene expression, implicating menin as the primary mediator of SSP gene activation. Transcriptional up regulation the SSP pathway has been linked to ATF4 in non-small cell lung cancer. Significantly, ATF4 protein expression is high in Ewing sarcoma cells and ATF4 transcript and protein expression are down regulated following MI-503 treatment and menin knockdown. Together these data demonstrate that the SSP is highly active in Ewing sarcoma and that its activation is induced, at least in part, by a novel menin-ATF4 transcriptional axis. Citation Format: Laurie Kathleen Svoboda, Selina Shiqing Teh, Sudha Sud, Armand Bankhead, Brian Magnuson, Mats Ljungman, Costas Lyssiotis, Tomasz Cierpicki, Jolanta Grembecka, Elizabeth R. Lawlor. Oncogenic activation of the serine synthesis pathway by the scaffolding protein menin [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5835. doi:10.1158/1538-7445.AM2017-5835

MEN1 mutations and potentially MEN1-targeting miRNAs are responsible for menin deficiency in sporadic and MEN1 syndrome-associated primary hyperparathyroidism.

Inherited, germline mutations of menin-coding MEN1 gene cause multiple endocrine neoplasia type 1 (MEN1), while somatic MEN1 mutations are the sole main driver mutations in sporadic primary hyperparathyroidism (PHPT), suggesting that menin deficiency has a central role in the pathogenesis of PHPT. MiRNAs are small, noncoding RNAs posttranscriptionally regulating gene expression. Our aim was to investigate both the role of MEN1 mutations and potentially MEN1-targeting miRNAs as the underlying cause of menin deficiency in MEN1-associated and sporadic PHPT tissues. Fifty six PHPT tissues, including 16 MEN1-associated tissues, were evaluated. Diagnosis of MEN1 syndrome was based on identification of germline MEN1 mutations. In silico target prediction was used to identify miRNAs potentially targeting MEN1. Menin expression was determined by immunohistochemistry while expression of miRNAs was analyzed by quantitative real-time PCR. Sporadic PHPT tissues were subjected to somatic MEN1 mutation analysis as well. Lack of nuclear menin was identified in all MEN1-associated and in 28% of sporadic PHPT tissues. Somatic MEN1 mutations were found in 25% of sporadic PHPTs. The sensitivity and specificity of menin immunohistochemistry to detect a MEN1 mutation were 86 and 87%, respectively. Expression levels of hsa-miR-24 and hsa-miR-28 were higher in sporadic compared to MEN1-associated PHPT tissues; however, no difference in miRNA levels occurred between menin-positive and menin-negative PHPT tissues. Menin deficiency is the consequence of a MEN1 mutation in most menin-negative PHPT tissues. Elevated expression of hsa-miR-24 and hsa-miR-28 mark the first epigenetic changes observed between sporadic and MEN1-associated PHPT.

Inhibition of microRNA-24 increases liver fibrosis by enhanced menin expression in Mdr2−/− mice

BackgroundLiver transplantation remains the primary treatment for primary sclerosing cholangitis (PSC). Mdr2−/− mice provide a reliable in vivo model of PSC and develop characteristic biliary inflammation and fibrosis. We tested the hypothesis that the tumor suppressor protein menin is implicated in the progression of liver fibrosis and that menin expression can be regulated in the liver via microRNA-24 (miR-24). Materials and methodsMenin expression was measured in human PSC and Mdr2−/− mice. Twelve-week-old FVB/NJ wild-type (WT) and Mdr2−/− mice were treated with miR-24 Vivo-Morpholino to knockdown miR-24 expression levels. Liver fibrosis was evaluated by Sirius Red staining and quantitative polymerase chain reaction (qPCR) for genes associated with liver fibrosis, such as fibronectin 1, collagen type 1 alpha 1, transforming growth factor-β1 (TGF-β1), and α-smooth muscle actin. Studies were also performed in vitro using immortalized murine cholangiocyte lines treated with miR-24 hairpin inhibitor and mimic. ResultsMenin gene expression was increased in Mdr2−/− mice and late-stage human PSC samples. Treatment of FVB/NJ WT and Mdr2−/− mice with miR-24 Vivo-Morpholino increased menin expression, which correlated with increased expression of fibrosis genes. In vitro, inhibition of miR-24 also significantly increased the expression of fibrosis genes. ConclusionsInhibition of miR-24 increases menin and TGF-β1 expression, subsequently increasing hepatic fibrosis in FVB/NJ WT and Mdr2−/− mice. Modulation of the menin/miR-24 axis may provide novel targeted therapies to slow the progression of hepatic fibrosis into cirrhosis in PSC patients by altering TGF-β1 expression.

A Review of the Scaffold Protein Menin and its Role in Hepatobiliary Pathology.

Multiple endocrine neoplasia type 1 (MEN1) is a familial cancer syndrome with neuroendocrine tumorigenesis of the parathyroid glands, pituitary gland, and pancreatic islet cells. The MEN1 gene codes for the canonical tumor suppressor protein, menin. Its protein structure has recently been crystallized, and it has been investigated in a multitude of other tissues. In this review, we summarize recent advancements in understanding the structure of the menin protein and its function as a scaffold protein in histone modification and epigenetic gene regulation. Furthermore, we explore its role in hepatobiliary autoimmune diseases, cancers, and metabolic diseases. In particular, we discuss how menin expression and function are regulated by extracellular signaling factors and nuclear receptor activation in various hepatic cell types. How the many signaling pathways and tissue types affect menin's diverse functions is not fully understood. We show that small-molecule inhibitors affecting menin function can shed light on menin's broad role in pathophysiology and elucidate distinct menin-dependent processes. This review reveals menin's often dichotomous function through analysis of its role in multiple disease processes and could potentially lead to novel small-molecule therapies in the treatment of cholangiocarcinoma or biliary autoimmune diseases.

MiR-762 can negatively regulate menin in ovarian cancer.

Ovarian cancer accounts for the major part of the mortality attributable to female reproductive system malignant tumors worldwide. Recently, the incidence of ovarian cancer has been increasing annually, and there remains a lack of suitable treatment methods that can significantly improve the 5-year survival rates of patients. Therefore, it is necessary to identify more effective treatments for ovarian cancer. It is established that microRNAs (miRNAs) have important roles in the diagnosis and treatment of ovarian cancer and a specific miRNA, miR-762, can promote the development of a variety of tumors. Menin is encoded by MEN1, a tumor suppressor gene, that is usually downregulated in ovarian cancer. In this study, we evaluated the expression levels of miR-762 and menin in ovarian cancer tissues and demonstrated that they were correlated. In addition, we found that miR-762 can downregulate the expression of menin through a binding site in its 3′-UTR and consequently upregulate the Wnt cell signaling pathway to promote the development of ovarian cancer. These results indicate that miR-762 is a promising potential target for the treatment of ovarian cancer.

Menin mediates Tat-induced neuronal apoptosis in brain frontal cortex of SIV-infected macaques and in Tat-treated cells.

The molecular mechanisms involved in human immunodeficiency virus (HIV)-associated neurocognitive disorder (HAND) remain poorly understood. It has been recently reported that HIV-1 Tat transactivation requires menin, suggesting that menin may be involved in HAND pathogenesis. But the role of menin is not clear. Here, we found that protein level of menin was increased in simian-human immunodeficiency chimeric virus (SHIV)-SF162.P4 and simian immunodeficiency virus (SIV) sm543-3-infected rhesus macaques compared with the controls by immunohistochemistry (IHC) and western blot. Menin mainly expressed in the frontal cortex neurons of the brain, more importantly, the number of menin-staining cells was positively correlated with cleaved-caspase-3-positive cells while it was negatively correlated with a neuron-specific nuclear protein NeuN-positive cells, suggesting that expression of menin may induce neuronal apoptosis. Further studies showed that menin level was significantly increased during Tat-induced apoptosis, while downregulation of menin by pll3.7-MEN1-shRNA attenuated the Tat-induced cleavage of caspase-3 and caspase-8 in SY5Y cells and primary neuron cultures. Together, our findings reveal a pro-apoptotic role of menin in the brains of the SIV-infected macaques and the cultured neurons, indicating that targeting menin may be potential to block the HIV-1 Tat induced neuronal damage in HAND.

MiR-24 Inhibition Increases Menin Expression and Decreases Cholangiocarcinoma Proliferation

Menin (MEN1) is a tumor-suppressor protein in neuroendocrine tissue. Therefore, we tested the novel hypothesis that menin regulates cholangiocarcinoma proliferation. Menin and miR-24 expression levels were measured in the following intrahepatic and extrahepatic cholangiocarcinoma (CCA) cell lines, Mz-ChA-1, TFK-1, SG231, CCLP, HuCCT-1, and HuH-28, as well as the nonmalignant human intrahepatic biliary line, H69. miR-24 miRNA and menin protein levels were manipulated invitro in Mz-ChA-1 cell lines. Markers of proliferation and angiogenesis (Ki-67, vascular endothelial growth factors A/C, vascular endothelial growth factor receptors 2/3, angiopoietin 1/2, and angiopoietin receptors 1/2) were evaluated. Mz-ChA-1 cells were injected into the flanks of nude mice and treated with miR-24 inhibitor or inhibitor scramble. Menin expression was decreased in advanced CCA specimens, whereas miR-24 expression was increased in CCA. Menin overexpression decreased proliferation, angiogenesis, migration, and invasion. Inhibition of miR-24 increased menin protein expression while decreasing proliferation, angiogenesis, migration, and invasion. miR-24 was shown to negatively regulate menin expression by luciferase assay. Tumor burden and expression of proliferative and angiogenic markers was decreased in the miR-24 inhibited tumor group compared to controls. Interestingly, treated tumors were more fibrotic than the control group. miR-24-dependent expression of menin may be important in the regulation of nonmalignant and CCA proliferation and may be an additional therapeutic tool for managing CCA progression.

EXPRESSION OF MENIN IN THE HUMAN THYROID GLAND.

The expression of menin in the thyroid gland has long been debated. Animal models with targeted inactivation of menin in the thyroid gland have shown that its inactivation might play a role in the progression to a more aggressive type of cancer. Human studies are conflicting, some have identified mutations in the MEN1 gene in a sub-type of oncocytic thyroid carcinomas, while others have not identified a higher prevalence of thyroid cancer in MEN1 patients. To analyze the immunohistochemical expression of menin in different types of thyroid carcinomas. 48 thyroid tumours (12 papillary thyroid carcinomas (PTC), 6 anaplastic thyroid carcinomas (ATC), 12 poorly differentiated thyroid carcinomas (PDTC), 5 medullary thyroid carcinomas (MTC), 5 oncocytic follicular carcinomas (OC), 3 oncocytic adenomas (OA) and 5 goiters (G)) were tested for nuclear expression of menin using an anti-menin antibody. The expression was considered positive, negative or decreased. The expression of menin was positive, identical to normal tissue, in 39 cases (81.25%). The expression was decreased (n=8) or absent (n=1) in 9 tumours (18.75% - 2 PTC, 5 PDTC, 2 OC) accounting for 42% (5/12) of the PDTC and 40% (2/5) of the OC. Our results show that the expression of menin is generally preserved in human thyroid carcinomas, but it can be decreased or absent in certain types of thyroid cancer. Further molecular studies are needed to evaluate to potential of menin protein in tumorigenesis.

Aberrant Menin expression is an early event in pancreatic neuroendocrine tumorigenesis

Pancreatic neuroendocrine tumors (PanNETs) are the second most common pancreatic malignancy and cause significant morbidity and mortality. Neuroendocrine microadenomas have been proposed as a potential precursor lesion for sporadic PanNETs. In this study, we applied telomere-specific fluorescent in situ hybridization (FISH) to a series of well-characterized sporadic neuroendocrine microadenomas and investigated the prevalence of alterations in known PanNET driver genes (MEN1 and ATRX/DAXX) in these same tumors using immunohistochemistry for the encoded proteins. We identified aberrant Menin expression in 14 of 19 (74%) microadenomas, suggesting that alterations in Menin, at least a subset of which was likely due to somatic mutation, are early events in pancreatic neuroendocrine tumorigenesis. In contrast, none of the microadenomas met criteria for the alternative lengthening of telomeres phenotype (ALT) based on telomere FISH, a phenotype that is strongly correlated to ATRX or DAXX mutations. Two of 13 microadenomas (15%) were noted to have very rare abnormal bright telomere foci on FISH, suggestive of early ALT, but these lesions did not show loss of ATRX or DAXX protein expression by immunohistochemistry. Overall, these data suggest that loss of Menin is an early event in pancreatic neuroendocrine tumorigenesis and that ATRX/DAXX loss and ALT are relatively late events.

Overexpression of PY1289-HER3 in sporadic pulmonary carcinoid from patients bearing MEN1 gene variants.

The present study aimed to investigate the expression of human epidermal growth factor receptors (HERs) (HER1/HER2/HER3/HER4) and their phosphorylated forms (p-HER1/p-HER2/p-HER3/p-HER4) in pulmonary carcinoids (PCs). HER and p-HER protein expression was assessed by immunohistochemistry on tissue microarrays in 37 specimens of sporadic PCs, 29 typical carcinoids (TCs) and 8 atypical carcinoids (ACs). When compared with the ACs, the TCs did not exhibit any differences in terms of HER/p-HER expression. The tumors of this study have previously been characterized for the expression of menin and the mutational status of menin 1 (MEN1), a gene strongly implicated in the pathogenesis of PCs. In the present study, it was found that the cytoplasmic (‘disarrayed’), but not nuclear (‘arrayed’) expression of menin was positively correlated with HER3 (P=0.004), HER4 (P=0.015), p-HER1 (P=0.005), p-HER3 (P<0.001), and p-HER4 (P=0.001) expression. Moreover, HER3 and p-HER3 were found to be significantly more expressed in PCs with MEN1 variants, than in tumors with MEN1 wild-type (P=0.000 and P=0.025, respectively). These findings suggest the potential clinical use of HER inhibitors in the treatment of patients with PCs, particularly for individuals with p-HER3-positive PCs harboring MEN1 gene variants.

Tu1616 miR-125b Negatively Regulates Menin Expression and Protects from Liver Fibrosis

Tu1616 miR-125b Negatively Regulates Menin Expression and Protects from Liver Fibrosis

Interplay between menin and Dnmt1 reversibly regulates pancreatic cancer cell growth downstream of the Hedgehog signaling pathway

Menin, the product of the Men1 gene, which is frequently mutated in pancreatic neuroendocrine tumors, acts as a chromatin-remodeling factor to modulate the transcription of cell cycle regulators by interacting with histone modification factors. However, the function of menin and its underlying mechanisms in pancreatic ductal adenocarcinoma remain unknown. Here, we found that menin inhibited pancreatic cancer cell growth in vitro and in vivo and that its expression was gradually lost during pancreatic carcinogenesis. Menin overexpression significantly activated the expression of the cyclin-dependent kinase (CDK) inhibitors p18 and p27, accompanied with a decrease in DNA methylation levels of p18 and p27 promoters. Mechanistically, we found that interaction of menin with DNA methyltransferase 1 (Dnmt1) competitively pulled down Dnmt1 from p18 and p27 promoters, leading to the downregulation of DNA methylation levels. Moreover, menin expression was suppressed by Dnmt1 downstream of the Hedgehog signaling pathway, and menin overexpression strongly antagonized the promotion effect of hedgehog signaling on pancreatic cancer cell proliferation. Taken together, the interaction between menin and Dnmt1 reversibly regulates pancreatic cancer cell growth downstream of Hedgehog pathways with complex mutual modulation networks, suggesting that the Hedgehog/Dnmt1/menin axis is a potential molecular target for pancreatic cancer therapy.

Sa1700 The Secretin/Secretin Receptor Axis Modulates Biliary Proliferation Following Cholestatic Injury Through Changes in Menin Expression

Sa1700 The Secretin/Secretin Receptor Axis Modulates Biliary Proliferation Following Cholestatic Injury Through Changes in Menin Expression

Targeting the MLL complex in castration-resistant prostate cancer.

Resistance to androgen deprivation therapies and increased androgen receptor (AR) activity are major drivers of castration resistant prostate cancer (CRPC). Although prior work focused on targeting AR directly, co-activators of AR signaling—which may represent new therapeutic targets—are relatively underexplored. Here we demonstrate that the mixed-lineage leukemia (MLL) complex, a well-known driver of MLL-fusion-positive leukemia, acts as a co-activator of AR signaling. AR directly interacts with the MLL complex via the menin MLL subunit. Menin expression is higher in castration resistant prostate cancer compared to hormone naïve prostate cancer and benign prostate and high menin expression correlates with poor overall survival. Treatment with a small molecule inhibitor of the menin-MLL interaction blocks AR signaling and inhibits the growth of castration resistant tumors in vivo in mice. Taken together, this work identifies the MLL complex as a critical co-activator of AR and a potential therapeutic target in advanced prostate cancer.

Highlights from Recent Cancer Literature

Funato and colleagues used human embryonic stem (hES) cells to model diffuse intrinsic pontine glioma (DIPG), a disease arising in a restricted location and developmental window. DIPGs are associated with H3.3K27M mutations in the histone variant H3F3A gene, loss of p53, and amplification of PDGFRA. Embryonic stem cells were differentiated into neural progenitor cells (NPC). While expression of PDGFRAD842A or H3.3K27M and knockdown of p53 individually promoted proliferation, the three (P5K) synergized in intracranial transformation and in blocking glial differentiation. Genes expressed in the neural plate during very early development were enriched, suggesting dedifferentiation of NPCs by P5K. Expression of menin, normally expressed in both hES cells and the neural plate, was upregulated in P5K cells. A menin inhibitor decreased tumor growth in vivo, supporting an oncogenic role in DIPG.Funato K, Major T, Lewis PW, Allis CD, Tabar V. Use of human embryonic stem cells to model pediatric gliomas with H3.3K27M histone mutation. Science 2014;346:1529–33.Using a library of oligonucleotide inhibitors to miRNAs, Borkowski and colleagues identified novel synthetic lethal interactions between miRNA inhibition and p53 mutation in non–small cell lung cancer. Specifically, two inhibitors of miR-92a and miR-1226 were toxic in 27 cell lines that had lost expression of p53. Interestingly, depletion of p53 enhanced sensitivity of telomerase-immortalized bronchial epithelial cells that were otherwise resistant. The miR-17∼92 polycistron was downregulated by both inhibitors, but only when p53 was lost. Further studies showed that toxicity was caused by derepression of vitamin D signaling via suppression of CYP24A1. Additionally, CYP24A1 expression was correlated with poor patient outcome in lung cancer. Thus, the authors have identified clinically relevant synthetic lethal interactions that might be beneficial for patients with p53-negative lung cancer.Borkowski R, Du L, Zhao Z, McMillan E, Kosti A, Yang CR, et al. Genetic mutation of p53 and suppression of the miR-17∼92 cluster are synthetic lethal in non–small cell lung cancer due to upregulation of vitamin D signaling. Cancer Res; Published OnlineFirst December 17, 2014; doi:10.1158/0008-5472.CAN-14-1329.Tiberi and colleagues show that the lymphoma oncoprotein BCL6 controls neurogenesis during cerebellum development by regulation of granular neuron precursor cells. This activity of BCL6 required both the histone deacetylase SIRT1 and the BCOR corepressor, acting in a multiprotein complex to repress expression of the Sonic Hedgehog (SHH)–regulated transcription factors Gli1 and Gli2. This multiprotein complex bound directly to BCL6 sites to remodel chromatin and repress gene expression. Using SHH-dependent medulloblastoma cells and models, the authors show that BCL6 acted via epigenetic suppression of Gli1 and Gli2, doubling survival time in mice. Mice lacking both Bcl6 and Trp53, but not either gene alone, developed medulloblastoma. Thus, Bcl6 acts as either an oncogene or a tumor suppressor via epigenetic regulation of distinct subsets of genes in a context-dependent manner.Tiberi L, Bonnefont J, van den Ameele J, Le Bon SD, Herpoel A, Bilheu A, et al. A BCL6/BCOR/SIRT1 complex triggers neurogenesis and suppresses medulloblastoma by repressing Sonic Hedgehog signaling. Cancer Cell 2014;26:797–812.Note: Breaking Advances are written by Cancer Research editors. Readers are encouraged to consult the articles referred to in each item for full details on the findings described.

Thyroid incidentalomas in patients with multiple endocrine neoplasia type 1.

Currently, little is known about the prevalence of thyroid tumors in multiple endocrine neoplasia type 1 (MEN1) patients and it is unclear whether tumorigenesis of these thyroid tumors is MEN1-related. The aim of the study was to assess the prevalence of thyroid incidentalomas in MEN1 patients compared with nonMEN1 patients and to verify whether thyroid tumorigenesis is MEN1-related. A cross-sectional study. The study included two groups: patients with MEN1 and a matched non-MEN1 control group without known thyroid disease, who underwent an ultrasound of the neck for the localization of parathyroid adenoma. Ninety-five MEN1 patients underwent ultrasound of the neck and were matched on gender and age with non-MEN1 patients. The prevalence of thyroid incidentalomas described in the ultrasound report was scored. Multinodular goiters, solitary nodes, and cysts were scored as incidentalomas. Presence of nuclear menin expression was evaluated by menin immunostaining of the thyroid tumors. In the MEN1 group, 43 (45%) patients had a thyroid incidentaloma compared with 48 (51%) in the non-MEN1 group, of which 14 (15%) and 16 (17%), respectively, were solitary nodes. Menin was expressed in the nuclei of all evaluated thyroid tumors. MEN1 patients do not have a higher prevalence of thyroid incidentalomas compared with primary hyperparathyroidism patients without the diagnosis of MEN1. Menin was expressed in the thyroid tumors of MEN1 patients.

Modulation by miR-29b of intestinal epithelium homoeostasis through the repression of menin translation.

Menin regulates distinct cellular functions by regulating gene transcription through its interaction with partner transcription factors, but the exact mechanisms that control menin levels remain largely unknown. In the present study we report that Men1 mRNA, encoding menin, is a novel target of miR-29b and that miR-29b/Men1 mRNA association regulates menin expression post-transcriptionally in rat intestinal epithelial cells (IECs). Overexpression of a miR-29b precursor lowered the levels of Men1 mRNA modestly, but reduced new synthesis of menin robustly; conversely, antagonism of miR-29b enhanced menin protein synthesis and steady-state levels. The repressive effect of miR-29b on menin expression was mediated through a single binding site in the coding region of Men1 mRNA, because point mutation of this site prevented miR-29b-induced repression of menin translation. Increasing cellular polyamines due to overexpression of ornithine decarboxylase (ODC) enhanced menin translation by reducing miR-29b, whereas polyamine depletion by inhibiting ODC increased it, thus suppressing menin expression. Moreover, an increase in menin abundance in an miR-29b-silenced population of IECs led to increased sensitivity to apoptosis, which was prevented by silencing menin. These findings indicate that miR-29b represses translation of Men1 mRNA, in turn affecting intestinal epithelial homoeostasis by altering IEC apoptosis.