Menin uncouples Elk-1, JunD and c-Jun phosphorylation from MAP kinase activation

Menin in Cancer

The protein menin is encoded by the MEN1 gene and primarily serves as a nuclear scaffold protein, regulating gene expression through its interaction with and regulation of chromatin modifiers and transcription factors. While the scope of menin's functions continues to expand, one area of growing investigation is the role of menin in cancer. Menin is increasingly recognized for its dual function as either a tumor suppressor or a tumor promoter in a highly tumor-dependent and context-specific manner. While menin serves as a suppressor of neuroendocrine tumor growth, as seen in the cancer risk syndrome multiple endocrine neoplasia type 1 (MEN1) syndrome caused by pathogenic germline variants in MEN1, recent data demonstrate that menin also suppresses cholangiocarcinoma, pancreatic ductal adenocarcinoma, gastric adenocarcinoma, lung adenocarcinoma, and melanoma. On the other hand, menin can also serve as a tumor promoter in leukemia, colorectal cancer, ovarian and endometrial cancers, Ewing sarcoma, and gliomas. Moreover, menin can either suppress or promote tumorigenesis in the breast and prostate depending on hormone receptor status and may also have mixed roles in hepatocellular carcinoma. Here, we review the rapidly expanding literature on the role and function of menin across a broad array of different cancer types, outlining tumor-specific differences in menin's function and mechanism of action, as well as identifying its therapeutic potential and highlighting areas for future investigation.

Downregulation of FHL2 suppressed trophoblast migration, invasion and epithelial-mesenchymal transition in recurrent miscarriage

RESEARCH QUESTION

Is four and a half LIM domain 2 (FHL2) involved in trophoblast migration, invasion and epithelial-mesenchymal transition (EMT) in recurrent miscarriage?

DESIGN

Villus tissue was collected from 24 patients who had experienced recurrent miscarriage and 24 healthy controls. FHL2 mRNA and protein expression in villus specimens were observed by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot. Small interfering RNA and overexpression plasmid were used to change the FHL2 expression. JAR and HTR8/SVneo cell lines were used to conduct scratch-wound assay and transwell assay to detect trophoblast migration and invasion of FHL2. Downstream molecule expression of mRNA and protein and EMT markers were verified by qRT-PCR and Western blot.

RESULTS

Significantly lower FHL2 mRNA (P = 0.019) and protein (P = 0.0014) expression was found in trophoblasts from the recurrent miscarriage group compared with healthy controls. FHL2 knockdown repressed migration (P = 0.0046), invasion (P < 0.001) and EMT, as shown by significant differences in mRNA and protein expression of the EMT markers N-cadherin, E-cadherin, Vimentin and Snail (all P < 0.05) of extravillus trophoblasts. FHL2 overexpression enhanced migration (P = 0.025), invasion (P < 0.001) and EMT of extravillus trophoblasts (all EMT markers P < 0.05). The positive upstream factor FHL2 in the extracellular signal-related kinase pathway induced JunD expression, thereby promoting trophoblast migration and invasion via matrix metalloproteinase 2.

CONCLUSIONS

FHL2 is involved in a regulatory pathway of trophoblast migration, invasion and EMT during early pregnancy, and may have a role in recurrent miscarriage pathogenesis, which can serve as a possible target for novel therapeutic development.

Integration of Transcriptomic Features to Improve Prognosis Prediction of Pediatric Acute Myeloid Leukemia With KMT2A Rearrangement

Lysine methyltransferase 2A-rearranged acute myeloid leukemia (KMT2A-r AML) is a special entity in the 2022 World Health Organization classification of myeloid neoplasms, characterized by high relapse rate and adverse outcomes. Current risk stratification was established on the treatment response and translocation partner of KMT2A. To study the transcriptomic feature and refine the current stratification of pediatric KMT2A-r AML, we analyzed clinical and RNA sequencing data of 351 patients. By implementing least absolute shrinkage and selection operator algorithm, we identified 7 genes (KIAA1522, SKAP2, EGFL7, GAB2, HEBP1, FAM174B, and STARD8) of which the expression levels were strongly associated with outcomes. We then developed a transcriptome-based score, dividing patients into 2 groups with distinct gene expression patterns and prognosis, which was further validated in an independent cohort and outperformed the LSC17 score. We also found cell cycle, oxidative phosphorylation, and metabolism pathways were upregulated in patients with inferior outcomes. By integrating clinical characteristics, we proposed a simple-to-use prognostic scoring system with excellent discriminability, which allowed us to distinguish allogeneic hematopoietic stem cell transplantation candidates more precisely. In conclusion, pediatric KMT2A-r AML is heterogenous on transcriptomic level and the newly proposed scoring system combining clinical characteristics and transcriptomic features can be instructive in clinical routines.

ATRA ameliorates fibrosis by suppressing the pro-fibrotic molecule Fra2/AP-1 in systemic sclerosis

Systemic sclerosis (SSc) is an autoimmune connective tissue disease that leads to irreversible fibrosis of the skin and the internal organs. The etiology of SSc is complex, its pathophysiology is poorly understood, and clinical therapeutic options are restricted. Thus, research into medications and targets for treating fibrosis is essential and urgent. Fos-related antigen 2 (Fra2) is a transcription factor that is a member of the activator protein-1 family. Fra2 transgenic mice were shown to have spontaneous fibrosis. All-trans retinoic acid (ATRA) is a vitamin A intermediate metabolite and ligand for the retinoic acid receptor (RAR), which possesses anti-inflammatory and anti-proliferative properties. Recent research has demonstrated that ATRA also has an anti-fibrotic effect. However, the exact mechanism is not fully understood. Interestingly, we identified potential binding sites for the transcription factor RARα to the promoter region of the FRA2 gene through JASPAR and PROMO databases. In this study, the pro-fibrotic effect of Fra2 in SSc is confirmed. SSc dermal fibroblasts and bleomycin-induced fibrotic tissues of SSc animals exhibit increased levels of Fra2. Inhibition of Fra2 expression in SSc dermal fibroblasts with Fra2 siRNA markedly decreased collagen I expression. ATRA reduced the expressions of Fra2, collagen I, and α-smooth muscle actin(α-SMA) in SSc dermal fibroblasts and bleomycin-induced fibrotic tissues of SSc mice. In addition, chromatin immunoprecipitation and dual-luciferase assays demonstrated that retinoic acid receptor RARα binds to the FRA2 promoter and modulates its transcriptional activity. ATRA decreases collagen I expression both in vivo and in vitro via the reduction of Fra2 expression. This work establishes the rationale for expanding the use of ATRA in the treatment of SSc and indicates that Fra2 can be used as an anti-fibrotic target.

Activating Protein-1 (AP-1): A Promising Target for the Treatment of Fibrotic Diseases

The fibrosis of tissues and organs occurs via an aberrant tissue remodeling process characterized by an excessive deposition of extracellular matrix, which can lead to organ dysfunction, organ failure, and death. Because the pathogenesis of fibrosis remains unclear and elusive, there is currently no medication to reverse it; hence, this process deserves further study. Activating protein-1 (AP-1)-comprising Jun (c-Jun, JunB, JunD), Fos (c-fos, FosB, Fra1, and Fra2), and activating transcription factor-is a versatile dimeric transcription factor. Numerous studies have demonstrated that AP-1 plays a crucial role in advancing tissue and organ fibrosis via induction of the expression of fibrotic molecules and activating fibroblasts. This review focuses on the role of AP-1 in a range of fibrotic disorders as well as on the antifibrotic effects of AP-1 inhibitors. It also discusses the potential of AP-1 as a new therapeutic target in conditions involving tissue and organ fibrosis.

Therapeutic implications of menin inhibition in acute leukemias

Menin inhibitors are novel targeted agents currently in clinical development for the treatment of genetically defined subsets of acute leukemia. Menin has a tumor suppressor function in endocrine glands. Germline mutations in the gene encoding menin cause the multiple endocrine neoplasia type 1 (MEN1) syndrome, a hereditary condition associated with tumors of the endocrine glands. However, menin is also critical for leukemogenesis in subsets driven by rearrangement of the Lysine Methyltransferase 2A (KMT2A) gene, previously known as mixed-lineage leukemia (MLL), which encodes an epigenetic modifier. These seemingly opposing functions of menin can be explained by its various roles in gene regulation. Therefore, leukemias with rearrangement of KMT2A are predicted to respond to menin inhibition with early clinical data validating this proof-of-concept. These leukemias affect infants, children and adults, and lead to adverse outcomes with current standard therapies. Recent studies have identified novel targets in acute leukemia that are susceptible to menin inhibition, such as mutated Nucleophosmin 1 (NPM1), the most common genetic alteration in adult acute myeloid leukemia (AML). In addition to these alterations, other leukemia subsets with similar transcriptional dependency could be targeted through menin inhibition. This led to rationally designed clinical studies, investigating small-molecule oral menin inhibitors in relapsed acute leukemias with promising early results. Herein, we discuss the physiologic and malignant biology of menin, the mechanisms of leukemia in these susceptible subsets, and future therapeutic strategies using these inhibitors in acute leukemia.

Hyperglycemia Induces Myocardial Dysfunction via Epigenetic Regulation of JunD

RATIONALE

Hyperglycemia -induced reactive oxygen species are key mediators of cardiac dysfunction. JunD (Jund proto-oncogene subunit), a member of the AP-1 (activator protein-1) family of transcription factors, is emerging as a major gatekeeper against oxidative stress. However, its contribution to redox state and inflammation in the diabetic heart remains to be elucidated.

OBJECTIVE

The present study investigates the role of JunD in hyperglycemia-induced and reactive oxygen species-driven myocardial dysfunction.

METHODS AND RESULTS

JunD mRNA and protein expression were reduced in the myocardium of mice with streptozotocin-induced diabetes mellitus as compared to controls. JunD downregulation was associated with oxidative stress and left ventricular dysfunction assessed by electron spin resonance spectroscopy as well as conventional and 2-dimensional speckle-tracking echocardiography. Furthermore, myocardial expression of free radical scavenger superoxide dismutase 1 and aldehyde dehydrogenase 2 was reduced, whereas the NOX2 (NADPH [nicotinamide adenine dinucleotide phosphatase] oxidase subunit 2) and NOX4 (NADPH [nicotinamide adenine dinucleotide phosphatase] oxidase subunit 4) were upregulated. The redox changes were associated with increased NF-κB (nuclear factor kappa B) binding activity and expression of inflammatory mediators. Interestingly, mice with cardiac-specific overexpression of JunD via the α MHC (α- myosin heavy chain) promoter (α MHC JunD^tg) were protected against hyperglycemia-induced cardiac dysfunction. We also showed that JunD was epigenetically regulated by promoter hypermethylation, post-translational modification of histone marks, and translational repression by miRNA (microRNA)-673/menin. Reduced JunD mRNA and protein expression were confirmed in left ventricular specimens obtained from patients with type 2 diabetes mellitus as compared to nondiabetic subjects.

CONCLUSIONS

Here, we show that a complex epigenetic machinery involving DNA methylation, histone modifications, and microRNAs mediates hyperglycemia-induced JunD downregulation and myocardial dysfunction in experimental and human diabetes mellitus. Our results pave the way for tissue-specific therapeutic modulation of JunD to prevent diabetic cardiomyopathy.

Primary hyperparathyroidism associated with non-Hodgkin lymphoma: a case report and literature review

Primary hyperparathyroidism is the third most common endocrine disease, while primary hyperparathyroidism associated with non-Hodgkin lymphoma(NHL) is extremely rare. We report a case of primary hyperparathyroidism associated with NHL. The first symptom of this patient was hypercalcemia. Hypercalcemia is the primary first clinical manifestation of primary hyperparathyroidism, while NHL may also be diagnosed by hypercalcemia. Clinically, patients with hypercalcemia as the first symptom should be alert to the coexistence of their two diseases. As primary hyperparathyroidism and NHL occur simultaneously, the relationship between the two diseases requires further study. A review of the literature regarding primary hyperparathyroidism associated with NHL was performed, focusing on clinical presentation, diagnosis, treatment, prognosis, and the connection.

Enhanced JunD/RSK3 signalling due to loss of BRD4/FOXD3/miR-548d-3p axis determines BET inhibition resistance

BET bromodomain inhibitors (BETi), such as JQ1, have been demonstrated to effectively kill multiple types of cancer cells. However, the underlying mechanisms for BETi resistance remain largely unknown. Our evidences show that JQ1 treatment evicts BRD4 from the FOXD3-localized MIR548D1 gene promoter, leading to repression of miR-548d-3p. The loss of miRNA restores JunD expression and subsequent JunD-dependent transcription of RPS6KA2 gene. ERK1/2/5 kinases phosphorylate RSK3 (RPS6KA2), resulting in the enrichment of activated RSK3 and blockade of JQ1 killing effect. Dual inhibition of MEKs/ERKs or single EGFR inhibition are able to mimic the effect of JunD/RSK3-knockdown to reverse BETi resistance. Collectively, our study indicates that loss of BRD4/FOXD3/miR-548d-3p axis enhances JunD/RSK3 signalling and determines BET inhibition resistance, which can be reversed by targeting EGFR-MEK1/2/5-ERK1/2/5 signalling.

The clinical use of BET inhibitors (BETi) is limited by primary and acquired resistance. Here, the authors report that BETi resistance is determined by JunD/RSK3 signalling activation induced by the loss of BRD4/Foxd3/miR-548d-3p, which can be reverted by targeting the EGFR-MEK-ERK pathway.

Identification and functional analysis of a novel splice variant of AC3-33 in breast cancer

Alternative RNA splicing plays a key role in regulating gene function and influencing protein expression diversity. In the present study, an AC-33 transcript variant (NCBI Reference Sequence: NM_001308229.1), splice variant (sv)AC3-33, was successfully cloned from the MCF-7 breast cancer cell line by reverse transcription PCR using primers based on expressed sequence tags. The aim of the present study was to investigate the structure and function of svAC3-33. svAC3-33 has an open reading frame of 1,825 base pairs, lacks AC3-33 exon 2 and is encoded by 294 amino acids. svAC3-33 is localized within the cytoplasm. The Cell Counting Kit-8 and EdU detection of cell proliferation assays showed that svAC3-33 inhibited MCF-7 cell proliferation. Similarly, svAC3-33 knockdown by RNA interference was shown to have the opposite effect by repressing the cell cycle progression of breast cancer cells. Furthermore, the data indicated that svAC3-33 may upregulate the expression of p21. The present study provides evidence that the increased expression of svAC3-33 may inhibit the activity of the transcription factor AP-1. The luciferase reporter gene assay detected a downregulation of the expression of c-Jun, but not c-Fos, which in turn affected cell proliferation. In conclusion, these results indicated a function for svAC3-33 in inhibiting the cell proliferation of MCF-7 cells by regulating the AP-1 signaling pathway.

Overview of Genetically Determined Diseases/Multiple Endocrine Neoplasia Syndromes Predisposing to Endocrine Tumors

In this chapter, we present an overview of multiple endocrine neoplasia syndromes including their most important clinical and molecular features. Multiple endocrine neoplasia type 1 and 2 syndromes (MEN1 and MEN2) are discussed in detail. Syndromes that are presented in other chapters are only briefly mentioned. We discuss the relevance of germline gene alterations in apparently sporadic endocrine tumors, e.g., medullary thyroid cancer, primary hyperparathyroidism, and neuroendocrine tumors. McCune-Albright syndrome that only exists in non-hereditary, sporadic forms is also discussed in detail, as tumors of several endocrine organs can develop in the same individual.

Molecular Genetic Studies of Pancreatic Neuroendocrine Tumors: New Therapeutic Approaches

Pancreatic neuroendocrine tumors (PNETs) arise sporadically or as part of familial syndromes. Genetic studies of hereditary syndromes and whole exome sequencing analysis of sporadic NETs have revealed the roles of some genes involved in PNET tumorigenesis. The multiple endocrine neoplasia type 1 (MEN1) gene is most commonly mutated. Its encoded protein, menin, has roles in transcriptional regulation, genome stability, DNA repair, protein degradation, cell motility and adhesion, microRNA biogenesis, cell division, cell cycle control, and epigenetic regulation. Therapies targeting epigenetic regulation and MEN1 gene replacement have been reported to be effective in preclinical models.

Multiple Endocrine Neoplasia Syndromes from Genetic and Epigenetic Perspectives

Multiple endocrine neoplasia (MEN) syndromes are infrequent inherited disorders in which more than one endocrine glands develop noncancerous (benign) or cancerous (malignant) tumors or grow excessively without forming tumors. There are 3 famous and well-known forms of MEN syndromes (MEN 1, MEN 2A, and MEN 2B) and a newly documented one (MEN4). These syndromes are infrequent and occurred in all ages and both men and women. Usually, germ line mutations that can be resulted in neoplastic transformation of anterior pituitary, parathyroid glands, and pancreatic islets in addition to gastrointestinal tract can be an indicator for MEN1. The medullary thyroid cancer (MTC) in association with pheochromocytoma and/or multiple lesions of parathyroid glands with hyperparathyroidism can be pointer of MEN2 which can be subgrouped into the MEN 2A, MEN 2B, and familial MTC syndromes. There are no distinct biochemical markers that allow identification of familial versus nonfamilial forms of the tumors, but familial MTC usually happens at a younger age than sporadic MTC. The MEN1 gene (menin protein) is in charge of MEN 1 disease, CDNK1B for MEN 4, and RET proto-oncogene for MEN 2. The focus over the molecular targets can bring some hope for both diagnosis and management of MEN syndromes. In the current review, we look at this disease and responsible genes and their cell signaling pathway involved.

MTBP inhibits the Erk1/2-Elk-1 signaling in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide, and the prognosis of HCC patients, especially those with metastasis, remains extremely poor. This is partly due to unclear molecular mechanisms underlying HCC metastasis. Our previous study indicates that MDM2 Binding Protein (MTBP) suppresses migration and metastasis of HCC cells. However, signaling pathways regulated by MTBP remain unknown. To identify metastasis-associated signaling pathways governed by MTBP, we have performed unbiased luciferase reporter-based signal array analyses and found that MTBP suppresses the activity of the ETS-domain transcription factor Elk-1, a downstream target of Erk1/2 MAP kinases. MTBP also inhibits phosphorylation of Elk-1 and decreases mRNA expression of Elk-1 target genes. Reduced Elk-1 activity is caused by inhibited nuclear translocation of phosphorylated Erk1/2 (p-Erk) by MTBP and subsequent inhibition of Elk-1 phosphorylation. We also reveal that MTBP inhibits the interaction of p-Erk with importin-7/RanBP7 (IPO7), an importin family member which shuttles p-Erk into the nucleus, by binding to IPO7. Moreover, high levels of MTBP in human HCC tissues are correlated with cytoplasmic localization of p-Erk1/2. Our study suggests that MTBP suppresses metastasis, at least partially, by down-modulating the Erk1/2-Elk-1 signaling pathway, thus identifying a novel regulatory mechanism of HCC metastasis by regulating the subcellular localization of p-Erk.

The MAPK-activator protein-1 signaling regulates changes in lung tissue of rat exposed to hypobaric hypoxia

This study reports the role of MAPKs (JNK, ERK, and p38), and activator protein-1 (AP-1) transcription factor in the hypobaric hypoxia induced change in lung tissue. Healthy male Sprague-Dawley rats were exposed to hypobaric hypoxia for 6, 12, 24, 48, 72, and 120 hr. Hypoxia resulted in significant increase in reactive oxygen species (ROS), vascular endothelial growth factor (VEGF) and decreased nitric oxide (NO), these act as signaling molecules for activation of MAPK and also contribute in development of vascular leakage (an indicator of pulmonary edema) as confirmed by histological studies. Our results confirmed JNK activation as an immediate early response (peaked at 6-48 hr), activation of ERKs (peaked at 24-72 hr) and p38 (peaked at 72-120 hr) as a secondary response to hypoxia. The MAPK pathway up regulated its downstream targets phospho c-Jun (peaked at 6-120 hr), JunB (peaked at 24-120 hr) however, decreased c-Fos, and JunD levels. DNA binding activity also confirmed activation of AP-1 transcription factor in lung tissue under hypobaric hypoxia. Further, we analyzed the proliferative and inflammatory genes regulated by different subunits of AP-1 to explore its role in vascular leakage. Increased expression of cyclin D1 (peaked at 12-72 hr) and p16 level (peaked at 48-120 hr) were correlated to the activation of c-jun, c-Fos and JunB. Administration of NFκB inhibitor caffeic acid phenethyl ester (CAPE) and SP600125 (JNK inhibitor) had no effect on increased levels of Interferon-γ (IFN-γ), Interleukin-1 (IL-1), and Tumor Necrosis Factor-α (TNF-α) thereby confirming the involvement of AP-1 as well as NFκB in inflammation. Expression of c-jun, c-Fos were correlated with activation of proliferative genes and JunB, Fra-1 with pro-inflammatory cytokines. In conclusion immediate response to hypobaric hypoxia induced c-Jun:c-Fos subunits of AP-1; responsible for proliferation that might cause inhomogeneous vasoconstriction leading to vascular leakage and inflammation at increased duration of hypobaric hypoxia exposure.

Resistance-promoting effects of ependymoma treatment revealed through genomic analysis of multiple recurrences in a single patient

As in other brain tumors, multiple recurrences after complete resection and irradiation of supratentorial ependymoma are common and frequently result in patient death. This standard-of-care treatment was established in the pregenomic era without the ability to evaluate the effect that mutagenic therapies may exert on tumor evolution and in promoting resistance, recurrence, and death. We seized a rare opportunity to characterize treatment effects and the evolution of a single patient's ependymoma across four recurrences after different therapies. A combination of high-depth whole-genome and exome-based DNA sequencing of germline and tumor specimens, RNA sequencing of tumor specimens, and advanced computational analyses were used. Treatment with radiation and chemotherapies resulted in a substantial increase in mutational burden and diversification of the tumor subclonal architecture without eradication of the founding clone. Notable somatic alterations included a MEN1 driver, several epigenetic modifiers, and therapy-induced mutations that impacted multiple other cancer-relevant pathways and altered the neoantigen landscape. These genomic data provided new mechanistic insights into the genesis of ependymoma and pathways of resistance. They also revealed that radiation and chemotherapy were significant forces in shaping the increased subclonal complexity of each tumor recurrence while also failing to eradicate the founding clone. This raises the question of whether standard-of-care treatments have similar consequences in other patients with ependymoma and other types of brain tumors. If so, the perspective obtained by real-time genomic characterization of a tumor may be essential for making effective patient-specific and adaptive clinical decisions.

Current and emerging therapies for PNETs in patients with or without MEN1

Pancreatic neuroendocrine tumours (PNETs) might occur as a non-familial isolated endocrinopathy or as part of a complex hereditary syndrome, such as multiple endocrine neoplasia type 1 (MEN1). MEN1 is an autosomal dominant disorder characterized by the combined occurrence of PNETs with tumours of the parathyroids and anterior pituitary. Treatments for primary PNETs include surgery. Treatments for non-resectable PNETs and metastases include biotherapy (for example, somatostatin analogues, inhibitors of receptors and monoclonal antibodies), chemotherapy and radiological therapy. All these treatments are effective for PNETs in patients without MEN1; however, there is a scarcity of clinical trials reporting the efficacy of the same treatments of PNETs in patients with MEN1. Treatment of PNETs in patients with MEN1 is challenging owing to the concomitant development of other tumours, which might have metastasized. In recent years, preclinical studies have identified potential new therapeutic targets for treating MEN1-associated neuroendocrine tumours (including PNETs), and these include epigenetic modification, the β-catenin-wingless (WNT) pathway, Hedgehog signalling, somatostatin receptors and MEN1 gene replacement therapy. This Review discusses these advances.

Twenty years of menin: emerging opportunities for restoration of transcriptional regulation in MEN1

Since the discovery of the multiple endocrine neoplasia type 1 (MEN1) gene in 1997, elucidation of the molecular function of its protein product, menin, has been a challenge. Biochemical, proteomics, genetics and genomics approaches have identified various potential roles, which converge on gene expression regulation. The most consistent findings show that menin connects transcription factors and chromatin-modifying enzymes, in particular, the histone H3K4 methyltransferase complexes MLL1 and MLL2. Chromatin immunoprecipitation combined with next-generation sequencing has enabled studying genome-wide dynamics of chromatin binding by menin. We propose that menin regulates cell type-specific transcriptional programs by linking chromatin regulatory complexes to specific transcription factors. In this fashion, the MEN1 gene is a tumor suppressor gene in the endocrine tissues that are affected in MEN1. Recent studies have hinted at possibilities to pharmacologically restore the epigenetic changes caused by loss of menin function as therapeutic strategies for MEN1, for example, by inhibition of histone demethylases. The current lack of appropriate cellular model systems for MEN1-associated tumors is a limitation for compound testing, which needs to be addressed in the near future. In this review, we look back at the past twenty years of research on menin and the mechanism of disease of MEN1. In addition, we discuss how the current understanding of the molecular function of menin offers future directions to develop novel treatments for MEN1-associated endocrine tumors.

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.

KRAS, TP53, CDKN2A, SMAD4, BRCA1, and BRCA2 Mutations in Pancreatic Cancer

Pancreatic cancer is a disease that has a very high fatality rate and one of the highest mortality ratios among all major cancers, remaining the fourth leading cause of cancer-related deaths in developed countries. The major treatment of pancreatic cancer is surgery; however, only 15–20% of patients are candidates for it at the diagnosis of disease. On the other hand, survival in patients, who undergo surgery, is less than 30%. In most cancers, genome stability is disturbed and pancreatic cancer is not the exception. Approximately 97% of pancreatic cancers have gene derangements, defined by point mutations, amplifications, deletions, translocations, and inversions. This review describes the most frequent genetic alterations found in pancreatic cancer.

TGF-β Effects on Prostate Cancer Cell Migration and Invasion Require FosB

BACKGROUND

Activator Protein-1 (AP-1) family (cJun, JunB, JunD, cFos, FosB, Fra1, and Fra2) plays a central role in the transcriptional regulation of many genes that are associated with cell proliferation, differentiation, migration, metastasis, and survival. Many oncogenic signaling pathways converge at the AP-1 transcription complex. Transforming growth factor beta (TGF-β) is a multifunctional regulatory cytokine that regulates many aspects of cellular function, including cellular proliferation, differentiation, migration, apoptosis, adhesion, angiogenesis, immune surveillance, and survival.

METHODS

This study investigated, the role of FOS proteins in TGF-β signaling in prostate cancer cell proliferation, migration, and invasion. Steady state expression levels of FOS mRNA and proteins were determined using RT-PCR and western blotting analyses. DU145 and PC3 prostate cancer cells were exposed to TGF-β1 at varying time and dosage, RT-PCR, western blot, and immunofluorescence analyses were used to determine TGF-β1 effect on FOS mRNA and protein expression levels as well as FosB subcellular localization. Transient silencing of FosB protein was used to determine its role in cell proliferation, migration, and invasion.

RESULTS

Our data show that FOS mRNA and proteins were differentially expressed in human prostate epithelial (RWPE-1) and prostate cancer cell lines (LNCaP, DU145, and PC3). TGF-β1 induced the expression of FosB at both the mRNA and protein levels in DU145 and PC3 cells, whereas cFos and Fra1 were unaffected. Immunofluorescence analysis showed an increase in the accumulation of FosB protein in the nucleus of PC3 cells after treatment with exogenous TGF-β1. Selective knockdown of endogenous FosB by specific siRNA did not have any effect on cell proliferation in PC3 and DU145 cells. However, basal and TGF-β1- and EGF-induced cell migration was significantly reduced in DU145 and PC3 cells lacking endogenous FosB. TGF-β1- and EGF-induced cell invasion were also significantly decreased after FosB knockdown in PC3 cells.

CONCLUSION

Our data suggest that FosB is required for migration and invasion in prostate cancer cells. We also conclude that TGF-β1 effect on prostate cancer cell migration and invasion may be mediated through the induction of FosB. Prostate 77:72-81, 2017. © 2016 Wiley Periodicals, Inc.

Estrogenic gper signaling regulates mir144 expression in cancer cells and cancer-associated fibroblasts (cafs)

MicroRNAs (miRNAs) are small non coding RNA molecules that play a crucial role in several pathophysiological conditions, including cancer. The stimulation of hormone-sensitive tumors by estrogens are mediated by estrogen receptor (ER)α and G protein estrogen receptor (GPER). Previous studies have reported that ERα regulates miRNA expression, while this ability of GPER remains to be elucidated. Here, we demonstrate that in SkBr3 breast cancer and HepG2 hepatocarcinoma cells, 17β-estradiol (E2) and the selective GPER ligand G-1 induce miR144 expression through GPER and the involvement of the PI3K/ERK1/2/Elk1 transduction pathway. Moreover, we show that E2 and G-1 down-regulate through miR144 the onco-suppressor Runx1 and increase cell cycle progression. The capability of E2 and G-1 in triggering the induction of miR144 and the down-regulation of Runx1 was also confirmed in cancer-associated fibroblasts (CAFs) that are main components of the tumor microenvironment driving cancer progression. Further confirming these results, Runx1 protein levels were found decreased in tumor xenografts upon G-1 treatment. On the basis of our findings miR144 and Runx1 may be included among the oncotargets of GPER action. Moreover, the present data provide new insights regarding the ability of estrogens to trigger the GPER/miR144/Runx1 transduction pathway toward the stimulation of cancer progression.

The Cell Death Inhibitor ARC Is Induced in a Tissue-Specific Manner by Deletion of the Tumor Suppressor Gene Men1, but Not Required for Tumor Development and Growth

Multiple endocrine neoplasia type 1 (MEN1) is a genetic disorder characterized by tissue-specific tumors in the endocrine pancreas, parathyroid, and pituitary glands. Although tumor development in these tissues is dependent upon genetic inactivation of the tumor suppressor Men1, loss of both alleles of this gene is not sufficient to induce these cancers. Men1 encodes menin, a nuclear protein that influences transcription. A previous ChIP on chip analysis suggested that menin binds promoter sequences of nol3, encoding ARC, which is a cell death inhibitor that has been implicated in cancer pathogenesis. We hypothesized that ARC functions as a co-factor with Men1 loss to induce the tissue-restricted distribution of tumors seen in MEN1. Using mouse models that recapitulate this syndrome, we found that biallelic deletion of Men1 results in selective induction of ARC expression in tissues that develop tumors. Specifically, loss of Men1 in all cells of the pancreas resulted in marked increases in ARC mRNA and protein in the endocrine, but not exocrine, pancreas. Similarly, ARC expression increased in the parathyroid with inactivation of Men1 in that tissue. To test if ARC contributes to MEN1 tumor development in the endocrine pancreas, we generated mice that lacked none, one, or both copies of ARC in the context of Men1 deletion. Studies in a cohort of 126 mice demonstrated that, although mice lacking Men1 developed insulinomas as expected, elimination of ARC in this context did not significantly alter tumor load. Cellular rates of proliferation and death in these tumors were also not perturbed in the absence of ARC. These results indicate that ARC is upregulated by loss Men1 in the tissue-restricted distribution of MEN1 tumors, but that ARC is not required for tumor development in this syndrome.

DNA-repair defects in pancreatic neuroendocrine tumors and potential clinical applications

BACKGROUND

The role of DNA repair in pathogenesis and response to treatment is not well understood in pancreatic neuroendocrine tumors (pNETs). However, the existing literature reveals important preliminary trends and targets in the genetic landscape of pNETs. Notably, pNETs have been shown to harbor defects in the direct reversal MGMT gene and the DNA mismatch repair genes, suggesting that these genes may be strong candidates for further prospective studies.

METHODS

PubMed searches were conducted for original studies assessing the DNA repair genes MGMT and MMR in pNETs, as well as for PTEN and MEN1, which are not directly DNA repair genes but are involved in DNA repair pathways. Searches were specific to pNETs, yielding five original studies on MGMT and four on MMR. Six original papers studied PTEN in pNETs. Five studied MEN1 in pNETs, and two others implicated MEN1 in DNA repair processes.

RESULTS

The five studies on MGMT in pNET tumor samples found MGMT loss of between 24% and 51% of tumor samples by IHC staining and between 0% and 40% by promoter hypermethylation, revealing discrepancies in methods assessing MGMT expression as well as potential weaknesses in the correlation between MGMT IHC expression and promoter hypermethylation rates. Four studies on MMR in pNET tumor samples indicated similar ambiguities, as promoter hypermethylation of the MLH1 MMR gene ranged from 0% to 31% of pNETs, while IHC staining revealed loss of MMR genes in between 0% and 36% of pNETs sampled. Studies also indicated that PTEN and MEN1 are commonly mutated or underexpressed genes in pNETs, although frequency of mutation or loss of expression was again variable among different studies.

CONCLUSION

Further studies are essential in determining a more thorough repertoire of DNA repair defects in pNETs and the clinical significance of these defects. This literature review synthesises the existing knowledge of relevant DNA repair pathways and studies of the specific genes that carry out these repair mechanisms in pNETs.

Transcriptional profiling reveals functional links between RasGrf1 and Pttg1 in pancreatic beta cells

BACKGROUND

Our prior characterization of RasGrf1 deficient mice uncovered significant defects in pancreatic islet count and size as well as beta cell development and signaling function, raising question about the mechanisms linking RasGrf1 to the generation of those "pancreatic" phenotypes.

RESULTS

Here, we compared the transcriptional profile of highly purified pancreatic islets from RasGrf1 KO mice to that of WT control animals using commercial oligonucleotide microarrays. RasGrf1 elimination resulted in differential gene expression of numerous components of MAPK- and Calcium-signaling pathways, suggesting a relevant contribution of this GEF to modulation of cellular signaling in the cell lineages integrating the pancreatic islets. Whereas the overall transcriptional profile of pancreatic islets was highly specific in comparison to other organs of the same KO mice, a significant specific repression of Pttg1 was a common transcriptional alteration shared with other tissues of neuroectodermal origin. This observation, together with the remarkable pancreatic phenotypic similarities between RasGrf1 KO and Pttg1 KO mice suggested the possibility of proximal functional regulatory links between RasGrf1 and Pttg1 in pancreatic cell lineages expressing these proteins.Analysis of the mPttg1 promoter region identified specific recognition sites for numerous transcription factors which were also found to be differentially expressed in RasGrf1 KO pancreatic islets and are known to be relevant for Ras-ERK signaling as well as beta cell function. Reporter luciferase assays in BT3 insulinoma cells demonstrated the ability of RasGrf1 to modulate mPttg1 promoter activity through ERK-mediated signals. Analysis of the phenotypic interplay between RasGrf1 and Pttg1 in double knockout RasGrf1/Pttg1 mice showed that combined elimination of the two loci resulted in dramatically reduced values of islet and beta cell count and glucose homeostasis function which neared those measured in single Pttg1 KO mice and were significantly lower than those observed in individual RasGrf1 KO mice.

CONCLUSIONS

The specific transcriptional profile and signaling behavior of RasgGrf1 KO pancreatic islets, together with the dominance of Pttg1 over RasGrf1 with regards to the generation of these phenotypes in mouse pancreas, suggest that RasGrf1 is an important upstream component of signal transduction pathways regulating Pttg1 expression and controlling beta cell development and physiological responses.

Extracellular signal-regulated kinase signaling regulates the opposing roles of JUN family transcription factors at ETS/AP-1 sites and in cell migration

JUN transcription factors bind DNA as part of the AP-1 complex, regulate many cellular processes, and play a key role in oncogenesis. The three JUN proteins (c-JUN, JUNB, and JUND) can have both redundant and unique functions depending on the biological phenotype and cell type assayed. Mechanisms that allow this dynamic switching between overlapping and distinct functions are unclear. Here we demonstrate that JUND has a role in prostate cell migration that is the opposite of c-JUN's and JUNB's. RNA sequencing reveals that opposing regulation by c-JUN and JUND defines a subset of AP-1 target genes with cell migration roles. cis-regulatory elements for only this subset of targets were enriched for ETS factor binding, indicating a specificity mechanism. Interestingly, the function of c-JUN and JUND in prostate cell migration switched when we compared cells with an inactive versus an active RAS/extracellular signal-regulated kinase (ERK) signaling pathway. We show that this switch is due to phosphorylation and activation of JUND by ERK. Thus, the ETS/AP-1 sequence defines a unique gene expression program regulated by the relative levels of JUN proteins and RAS/ERK signaling. This work provides a rationale for how transcription factors can have distinct roles depending on the signaling status and the biological function in question.

Menin determines K-RAS proliferative outputs in endocrine cells

Endocrine cell proliferation fluctuates dramatically in response to signals that communicate hormone demand. The genetic alterations that override these controls in endocrine tumors often are not associated with oncogenes common to other tumor types, suggesting that unique pathways govern endocrine proliferation. Within the pancreas, for example, activating mutations of the prototypical oncogene KRAS drive proliferation in all pancreatic ductal adenocarcimomas but are never found in pancreatic endocrine tumors. Therefore, we asked how cellular context impacts K-RAS signaling. We found that K-RAS paradoxically suppressed, rather than promoted, growth in pancreatic endocrine cells. Inhibition of proliferation by K-RAS depended on antiproliferative RAS effector RASSF1A and blockade of the RAS-activated proproliferative RAF/MAPK pathway by tumor suppressor menin. Consistent with this model, a glucagon-like peptide 1 (GLP1) agonist, which stimulates ERK1/2 phosphorylation, did not affect endocrine cell proliferation by itself, but synergistically enhanced proliferation when combined with a menin inhibitor. In contrast, inhibition of MAPK signaling created a synthetic lethal interaction in the setting of menin loss. These insights suggest potential strategies both for regenerating pancreatic β cells for people with diabetes and for targeting menin-sensitive endocrine tumors.

Downregulation of tumor suppressor menin by miR-421 promotes proliferation and migration of neuroblastoma

Neuroblastoma, featured by a high rate of spontaneous remissions, is the most common extra-cranial solid tumor in infants and children. Numerous reports have demonstrated that MicroRNAs (miRNAs) play essential roles in cancer progression, including cell proliferation, apoptosis, invasion, metastasis and angiogenesis. miR-421 functions as an onco-miR in some malignancies. However, its role in neuroblastoma remains poorly understood. In the present study, we found that miR-421 was increased in neuroblastoma tissues compared with matched adjacent normal tissues. Forced overexpression of miR-421 substantially enhanced cell proliferation, cell-cycle progression, migration, and invasion of neuroblastoma cells. At the molecular level, tumor suppressor menin was found to be a target of miR-421. Furthermore, downregulation of menin by small interfering RNA oligos exhibited similar effects with overexpression of miR-421. On the other hand, overexpression of menin partially reversed the proliferative effects of miR-421 in neuroblastoma cells. Collectively, miR-421 may promote neuroblastoma cell growth and motility partially by targeting menin.

Regulation of human CYP2C9 expression by electrophilic stress involves activator protein 1 activation and DNA looping

Cytochrome P450 (CYP)2C9 and CYP2C19 are important human enzymes that metabolize therapeutic drugs, environmental chemicals, and physiologically important endogenous compounds. Initial studies using primary human hepatocytes showed induction of both the CYP2C9 and CYP2C19 genes by tert-butylhydroquinone (tBHQ). As a pro-oxidant, tBHQ regulates the expression of cytoprotective genes by activation of redox-sensing transcription factors, such as the nuclear factor E2-related factor 2 (Nrf2) and members of the activator protein 1 (AP-1) family of proteins. The promoter region of CYP2C9 contains two putative AP-1 sites (TGAGTCA) at positions -2201 and -1930, which are also highly conserved in CYP2C19. The CYP2C9 promoter is activated by ectopic expression of cFos and JunD, whereas Nrf2 had no effect. Using specific kinase inhibitors for mitogen-activated protein kinase, we showed that extracellular signal-regulated kinase and Jun N-terminal kinase are essential for tBHQ-induced expression of CYP2C9. Electrophoretic mobility shift assays demonstrate that cFos distinctly interacts with the distal AP-1 site and JunD with the proximal site. Because cFos regulates target genes as heterodimers with Jun proteins, we hypothesized that DNA looping might be required to bring the distal and proximal AP-1 sites together to activate the CYP2C9 promoter. Chromosome conformation capture analyses confirmed the formation of a DNA loop in the CYP2C9 promoter, possibly allowing interaction between cFos at the distal site and JunD at the proximal site to activate CYP2C9 transcription in response to electrophiles. These results indicate that oxidative stress generated by exposure to electrophilic xenobiotics and metabolites induces the expression of CYP2C9 and CYP2C19 in human hepatocytes.

Loss of menin mediated by endothelial cells treated with CoPP is associated with increased maturation of adipocytes

Oxidative stress is caused by an increase in reactive oxygen species (ROS) relative to the antioxidant defense system. An increase in ROS is known to decrease vascular function, increase inflammatory cytokines, and promote adipocyte hypertrophy. A known regulator of the oxidative stress response is the heat shock protein, heme-oxygenase 1 (HO-1), which is induced by cobalt protoporphyrin IX (CoPP). Menin was recently found to promote the sustained expression of heat shock proteins and is implicated in the regulation of oxidative stress. In this study, we investigated how changes in menin expression affected adipogenesis via the interaction between endothelial cells and adipocytes in response to CoPP treatment during oxidative stress. Using angiotensin II (Ang II) to induce oxidative stress in endothelial cells and adipocytes, we observed the induction of various cytokines including EGF, VEGF, angiogenin, IL-6, and MCP-1. Preadipocytes cultured in endothelial cell conditioned media treated with Ang II showed no changes in differentiation markers. Preadipocytes treated with the endothelial cell-conditioned media pretreated with CoPP resulted in an increase in the number of adipocytes, which expressed higher levels of adipocyte differentiation markers in direct correlation with the complete downregulation of the stress response regulator, menin. This change was not detected in adipocytes directly treated with CoPP alone. Therefore, we concluded that loss of menin is associated with the maturation of adipocytes induced by conditioned media from endothelial cells treated with CoPP.

Menin: a scaffold protein that controls gene expression and cell signaling

The protein menin is encoded by the MEN1 gene, which is mutated in patients with multiple endocrine neoplasia type 1 (MEN1) syndrome. Although menin acts as a tumor suppressor in endocrine organs, it is required for leukemic transformation in mouse models. Menin possesses these dichotomous functions probably because it can both positively and negatively regulate gene expression, as well as interact with a multitude of proteins with diverse functions. Here, we review the recent progress in understanding the molecular mechanisms by which menin functions. The crystal structures of menin with different binding partners reveal that menin is a key scaffold protein that functionally crosstalks with various partners to regulate gene transcription and interplay with multiple signaling pathways.

Menin and GIP are inversely regulated by food intake and diet via PI3/AKT signaling in the proximal duodenum

Background and Aims:

Ingestion of food stimulates the secretion of incretin peptides glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 to ensure the proper absorption and storage of nutrients. Menin is the 67 kDa protein product of the MEN1 gene recently reported to have a role in metabolism. In this study, we will determine the regulation of menin in the proximal duodenum by food intake and diet in correlation with GIP levels in the proximal duodenum of mice after an 18 h fast followed by 4 and 7 h refeeding and 3 months of high-fat diet.

Methods:

A dual luciferase assay was used to determine GIP promoter activity and ELISA was used to measure the levels of GIP after inhibition of menin through small interfering RNA (siRNA) and exposure to MAPK and AKT inhibitors. Colocalization of menin and GIP were determined by immunofluorescence.

Results:

Menin and GIP expression are regulated by fasting, refeeding and diet in the proximal duodenum. Overexpression of menin in STC-1 cells significantly inhibited GIP mRNA and promoter activity, whereas menin siRNA upregulated GIP levels. Inhibition of GIP expression by the PI3/AKT inhibitor, LY294002, was abrogated in STC-1 cells with reduced menin levels, whereas the MAPK inhibitor, UO126, inhibited the expression of GIP independent of menin. Exposure of STC-1 cells to GIP reduced menin expression in a dose-dependent manner via PI3K-AKT signaling.

Conclusion:

Feeding and diet regulates the expression of menin, which inversely correlates with GIP levels in the proximal duodenum. In vitro assays indicate that menin is a negative regulator of GIP via inhibition of PI3K-AKT signaling. We show menin colocalizing with GIP in K cells of the proximal gut and hypothesize that downregulation of menin may serve as a mechanism by which GIP is regulated in response to food intake and diet.

The role of heterodimeric AP-1 protein comprised of JunD and c-Fos proteins in hematopoiesis

Activator protein-1 (AP-1) regulates a wide range of cellular processes including proliferation, differentiation, and apoptosis. As a transcription factor, AP-1 is commonly found as a heterodimer comprised of c-Jun and c-Fos proteins. However, other heterodimers may also be formed. The function of these dimers, specifically the heterodimeric AP-1 comprised of JunD and c-Fos (AP-1(JunD/c-Fos)), has not been elucidated. Here, we identified a function of AP-1(JunD/c-Fos) in Xenopus hematopoiesis. A gain-of-function study performed by overexpressing junD and c-fos and a loss-of-function study using morpholino junD demonstrate a critical role for AP-1(JunD/c-Fos) in hematopoiesis during Xenopus embryogenesis. Additionally, we confirmed that JunD of AP-1(JunD/c-Fos) is required for BMP-4-induced hematopoiesis. We also demonstrated that BMP-4 regulated JunD activity at the transcriptional regulation and post-translational modification levels. Collectively, our findings identify AP-1(JunD/c-Fos) as a novel hematopoietic transcription factor and the requirement of AP-1(JunD/c-Fos) in BMP-4-induced hematopoiesis during Xenopus hematopoiesis.

The same pocket in menin binds both MLL and JUND but has opposite effects on transcription

Menin is a tumour suppressor protein whose loss or inactivation causes multiple endocrine neoplasia 1 (MEN1), a hereditary autosomal dominant tumour syndrome that is characterized by tumorigenesis in multiple endocrine organs. Menin interacts with many proteins and is involved in a variety of cellular processes. Menin binds the JUN family transcription factor JUND and inhibits its transcriptional activity. Several MEN1 missense mutations disrupt the menin-JUND interaction, suggesting a correlation between the tumour-suppressor function of menin and its suppression of JUND-activated transcription. Menin also interacts with mixed lineage leukaemia protein 1 (MLL1), a histone H3 lysine 4 methyltransferase, and functions as an oncogenic cofactor to upregulate gene transcription and promote MLL1-fusion-protein-induced leukaemogenesis. A recent report on the tethering of MLL1 to chromatin binding factor lens epithelium-derived growth factor (LEDGF) by menin indicates that menin is a molecular adaptor coordinating the functions of multiple proteins. Despite its importance, how menin interacts with many distinct partners and regulates their functions remains poorly understood. Here we present the crystal structures of human menin in its free form and in complexes with MLL1 or with JUND, or with an MLL1-LEDGF heterodimer. These structures show that menin contains a deep pocket that binds short peptides of MLL1 or JUND in the same manner, but that it can have opposite effects on transcription. The menin-JUND interaction blocks JUN N-terminal kinase (JNK)-mediated JUND phosphorylation and suppresses JUND-induced transcription. In contrast, menin promotes gene transcription by binding the transcription activator MLL1 through the peptide pocket while still interacting with the chromatin-anchoring protein LEDGF at a distinct surface formed by both menin and MLL1.

Insulin regulates menin expression, cytoplasmic localization, and interaction with FOXO1

Menin is the ubiquitously expressed nuclear protein product of the MEN1 gene, which interacts with PKB/Akt in the cytoplasm to inhibit its activity. This study describes a novel insulin-dependent mechanism of menin regulation and interaction with other metabolic proteins. We show that insulin downregulated menin in a time-dependent manner via the human insulin receptor. Inhibition analysis indicated a critical role for the protein kinase Akt in regulation of menin expression and localization. Insulin-mediated decrease in menin expression was abrogated by the PI3K/Akt inhibitor LY-294002 at early time points, from 2 to 7 h. Furthermore, exposure to insulin resulted in the cytoplasmic localization of menin and increased interaction with FOXO1. Fasting followed by refeeding modulates serum insulin levels, which corresponded to an increase in menin interaction with FOXO1 in the liver. Liver-specific hemizygous deletion of menin resulted in increased expression of FOXO1 target genes, namely IGFBP-1, PGC-1α, insulin receptor, Akt, and G-6-Pase. This study provides evidence that menin expression and localization are regulated by insulin signaling and that this regulation triggers an increase in its interaction with FOXO1 via Akt with metabolic consequences.

AC3-33, a novel secretory protein, inhibits Elk1 transcriptional activity via ERK pathway

The transcription factor AP-1 plays an important role in cellular proliferation, transformation and death. In this study, we report a novel human gene, AC3-33 (GenBank name: c3orf33, FLJ31139), which encodes a secretory protein that can inhibit Elk1 transcriptional activity via ERK1/2 pathway. The AC3-33 mRNA encodes a protein of 251 amino acids, which is a classical secretory protein. Functional investigation reveals that overexpression of AC3-33 significantly inhibit AP-1 activity and DNA-binding ability. Further investigation indicated that overexpression of AC3-33 significantly inhibit transcriptional activity of Elk1 and c-jun, but not c-fos. As for the upstream of signaling pathway of Elk-1, our study demonstrated that overexpression of AC3-33 significantly down-regulates phosphorylation of ERK1/2, but not JNK/SAPK or p38 MAPK. These results clearly indicate that AC3-33 is a novel member of the secretory family and inhibits Elk1 transcriptional activity via ERK1/2 MAPK.

Emerging roles of ATF2 and the dynamic AP1 network in cancer

Cooperation among transcription factors is central for their ability to execute specific transcriptional programmes. The AP1 complex exemplifies a network of transcription factors that function in unison under normal circumstances and during the course of tumour development and progression. This Perspective summarizes our current understanding of the changes in members of the AP1 complex and the role of ATF2 as part of this complex in tumorigenesis.

Multiple facets of junD gene expression are atypical among AP-1 family members

JunD is a versatile AP-1 transcription factor that can activate or repress a diverse collection of target genes. Precise control of junD expression and JunD protein-protein interactions modulate tumor angiogenesis, cellular differentiation, proliferation and apoptosis. Molecular and clinical knowledge of two decades has revealed that precise JunD activity is elaborated by interrelated layers of constitutive transcriptional control, complex post-transcriptional regulation and a collection of post-translational modifications and protein-protein interactions. The stakes are high, as inappropriate JunD activity contributes to neoplastic, metabolic and viral diseases. This article deconvolutes multiple layers of control that safeguard junD gene expression and functional activity. The activity of JunD in transcriptional activation and repression is integrated into a regulatory network by which JunD exerts a pivotal role in cellular growth control. Our discussion of the JunD regulatory network integrates important open issues and posits new therapeutic targets for the neoplastic, metabolic and viral diseases associated with JunD/AP-1 expression.

Multiple endocrine neoplasia type 1 (MEN1): analysis of 1336 mutations reported in the first decade following identification of the gene

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder characterized by the occurrence of tumors of the parathyroids, pancreas, and anterior pituitary. The MEN1 gene, which was identified in 1997, consists of 10 exons that encode a 610-amino acid protein referred to as menin. Menin is predominantly a nuclear protein that has roles in transcriptional regulation, genome stability, cell division, and proliferation. Germline mutations usually result in MEN1 or occasionally in an allelic variant referred to as familial isolated hyperparathyroidism (FIHP). MEN1 tumors frequently have loss of heterozygosity (LOH) of the MEN1 locus, which is consistent with a tumor suppressor role of MEN1. Furthermore, somatic abnormalities of MEN1 have been reported in MEN1 and non-MEN1 endocrine tumors. The clinical aspects and molecular genetics of MEN1 are reviewed together with the reported 1,336 mutations. The majority (>70%) of these mutations are predicted to lead to truncated forms of menin. The mutations are scattered throughout the>9-kb genomic sequence of the MEN1 gene. Four, which consist of c.249_252delGTCT (deletion at codons 83-84), c.1546_1547insC (insertion at codon 516), c.1378C>T (Arg460Ter), and c.628_631delACAG (deletion at codons 210-211) have been reported to occur frequently in 4.5%, 2.7%, 2.6%, and 2.5% of families, respectively. However, a comparison of the clinical features in patients and their families with the same mutations reveals an absence of phenotype-genotype correlations. The majority of MEN1 mutations are likely to disrupt the interactions of menin with other proteins and thereby alter critical events in cell cycle regulation and proliferation.

K252a prevents nigral dopaminergic cell death induced by 6-hydroxydopamine through inhibition of both mixed-lineage kinase 3/c-Jun NH2-terminal kinase 3 (JNK3) and apoptosis-inducing kinase 1/JNK3 signaling pathways

It is well documented that the mitogen-activated protein kinase pathway plays a pivotal role in rats with 6-hydroxydopamine (6-OHDA)-induced unilateral lesion in the nigrostriatal system. Our recent studies have shown that mixed-lineage kinase 3 (MLK3) and apoptosis-inducing kinase 1 (ASK1) are all involved in neuronal cell death induced by ischemia, which is mediated by the MLK3/c-Jun NH2-terminal kinase 3 (JNK3) and ASK1/JNK signaling pathway. To investigate whether these pathways are correlated with 6-OHDA-induced lesion as well, we examined the phosphorylation of MLK3, ASK1, and JNK3 in 6-OHDA rats. The results showed that both MLK3 and ASK1 could activate JNK3 and then subsequently enhance the neuronal death through its downstream pathways (i.e., nuclear and non-nuclear pathway). K252a have wide-range effects including Trk inhibition, MLK3 inhibition, and activation of phosphatidylinositol 3 kinase and mitogen-activated protein kinase kinase signaling pathways through interactions with distinct targets and is a well known neuroprotective compound. We found that K252a could protect dopaminergic neurons against cell program death induced by 6-OHDA lesion, and the phenotypes of 6-OHDA rat model treated with K252a were partial rescued. The inhibition of K252a on the activation of MLK3/JNK3 and ASK1/JNK3 provided a link between 6-OHDA lesion and stress-activated kinases. It suggested that both proapoptotic MLK3/JNK3 and ASK1/JNK3 cascade may play an important role in dopaminergic neuronal death in 6-OHDA insult. Thus, the JNK3 signaling may eventually emerge as a prime target for novel therapeutic approaches to treatment of Parkinson disease, and K252a may serve as a potential and important neuroprotectant in therapeutic aspect in Parkinson disease.

Diffuse large B-cell lymphoma in the thyroid gland associated with primary hyperparathyroidism

We report a case of primary hyperparathyroidism associated with a malignant lymphoma in the thyroid gland. A 68-year-old woman was admitted to hospital with a cervical mass. Ultrasound and computed tomography (CT) revealed a hypoechoic, multinodular tumor in the left thyroid gland. A gallium-67 citrate scintigram revealed intense radioisotope uptake in the thyroid tumor. Histological examination of biopsy specimens indicated that this tumor was a large B-cell lymphoma. The coexistence of parathyroid adenoma in this patient was revealed by a sestamibi scintigram, performed prior to chemotherapy. Following the complete remission of the lymphoma by chemotherapy, we carried out an excision of the single parathyroid adenoma. To our knowledge, this is the first report to describe a malignant thyroid lymphoma associated with primary hyperparathyroidism.

G protein-coupled receptor 30 (GPR30) mediates gene expression changes and growth response to 17beta-estradiol and selective GPR30 ligand G-1 in ovarian cancer cells

Estrogens play a crucial role in the development of ovarian tumors; however, the signal transduction pathways involved in hormone action are still poorly defined. The orphan G protein-coupled receptor 30 (GPR30) mediates the nongenomic signaling of 17beta-estradiol (E2) in a variety of estrogen-sensitive cancer cells through activation of the epidermal growth factor receptor (EGFR) pathway. Whether estrogen receptor alpha (ERalpha) also contributes to GPR30/EGFR signaling is less understood. Here, we show that, in ERalpha-positive BG-1 ovarian cancer cells, both E2 and the GPR30-selective ligand G-1 induced c-fos expression and estrogen-responsive element (ERE)-independent activity of a c-fos reporter gene, whereas only E2 stimulated an ERE-responsive reporter gene, indicating that GPR30 signaling does not activate ERalpha-mediated transcription. Similarly, both ligands up-regulated cyclin D1, cyclin E, and cyclin A, whereas only E2 enhanced progesterone receptor expression. Moreover, both GPR30 and ERalpha expression are required for c-fos stimulation and extracellular signal-regulated kinase (ERK) activation in response to either E2 or G-1. Inhibition of the EGFR transduction pathway inhibited c-fos stimulation and ERK activation by either ligand, suggesting that in ovarian cancer cells GPR30/EGFR signaling relays on ERalpha expression. Interestingly, we show that both GPR30 and ERalpha expression along with active EGFR signaling are required for E2-stimulated and G-1-stimulated proliferation of ovarian cancer cells. Because G-1 was able to induce both c-fos expression and proliferation in the ERalpha-negative/GPR30-positive SKBR3 breast cancer cells, the requirement for ERalpha expression in GPR30/EGFR signaling may depend on the specific cellular context of different tumor types.

Oncogenesis and mutagenesis of pituitary tumors

Although pituitary tumors may be present in up to 10% of the population, the pathophysiology of these lesions is not well characterized. Pituitary tumors are composed of monoclonal cell populations with disrupted control of replication pathways. The oncogenes and tumor suppressor genes that are common in other malignancies (i.e. jun, fos, myc, and p53) are rarely involved in the development of these tumors. However, oncogenes, such as gsp, can be present in up to 40% of hormonally active adenomas. The process of pituitary oncogenesis further appears to involve oncogenes such as cyclin E, cyclin D1, and the pituitary tumor transforming gene (PTTG). Finally, the cAMP signaling cascade plays a significant role in generation of both benign and malignant pituitary tumors. In this review, the biology of pituitary adenomas is explored with a special emphasis on potential targets for the development of targeted therapeutics.

Mechanisms of disease: multiple endocrine neoplasia type 1-relation to chromatin modifications and transcription regulation

Multiple endocrine neoplasia type 1 (MEN1) is a hereditary tumor syndrome characterized by tumors of the parathyroid glands, the pancreatic islets, the pituitary gland, the adrenal glands, as well as by neuroendocrine carcinoid tumors, often at a young age. Causal to the syndrome are germline mutations of the MEN1 tumor-suppressor gene. Identification of gene-mutation carriers has enabled presymptomatic diagnosis and treatment of MEN1-related lesions. The product of the MEN1 gene is the nuclear protein menin. Recent observations indicate several functions for menin in the regulation of transcription, serving either as a repressor or as an activator: menin interacts with the activator-protein-1-family transcription factor JunD, changing it from an oncoprotein into a tumor-suppressor protein, putatively by recruitment of histone deacetylase complexes; menin maintains transforming growth factor beta mediated signal transduction involved in parathyroid hormone and prolactin gene expression; and menin is an integral component of histone methyltransferase complexes. In this capacity menin is a regulator of expression of the cyclin-dependent-kinase inhibitors p18INK4C and p27Kip1; furthermore, menin serves as a co-activator of estrogen receptor mediated transcription, by recruiting methyltransferase activity to lysine 4 of histone 3 at the estrogen responsive TFF1(pS2) gene promoter. We propose that menin links transcription-factor function to histone-modification pathways and that this is crucial for MEN1 tumorigenesis. Understanding the molecular pathology of MEN1 tumorigenesis will lead to new therapeutic strategies.

Multiple endocrine neoplasia type 1 (MEN 1) is associated with an increased prevalence of diabetes mellitus and impaired fasting glucose

OBJECTIVE

Multiple endocrine neoplasia type 1 (MEN 1) is an autosomal dominant syndrome characterized by primary hyperparathyroidism, pituitary neoplasia and foregut lineage neuroendocrine tumours. It has also been associated with premature cardiovascular death. As diabetes is a risk factor for increased cardiovascular mortality we investigated the prevalence and clinical correlates of glycaemic abnormalities in a large MEN 1 kindred.

PATIENTS AND DESIGN

The glycaemic status of 72 MEN 1 affected and 133 unaffected members of a single large MEN 1 pedigree was assessed. Fasting glucose results were categorized and compared using WHO criteria. Associations between glycaemic status and MEN 1 phenotype were assessed.

RESULTS

Thirteen (18.1%) patients with MEN 1 compared to 5 (3.8%) control patients were diabetic (P < 0.001). Six (8.3%) MEN 1 patients had impaired fasting glucose compared to 4 (3%) of controls (P < 0.05). Of patients with MEN 1, uncontrolled hypercalcaemia (P < 0.05) and elevated serum gastrin (P < 0.05) were more common amongst patients diagnosed with abnormal glycaemia than those with normoglycaemia. There was a nonsignificant trend for elevated chromogranin A, pancreatic polypeptide, gastric inhibitory polypeptide (but not glucagon) and history of bronchopulmonary carcinoid in MEN 1 patients with elevated glycaemia.

CONCLUSIONS

Diabetes and impaired fasting glucose occur significantly more frequently amongst MEN 1 patients than controls and is associated with uncontrolled hyperparathyroidism and evidence of enteropancreatic hyperstimulation.

17beta-estradiol, genistein, and 4-hydroxytamoxifen induce the proliferation of thyroid cancer cells through the g protein-coupled receptor GPR30

The higher incidence of thyroid carcinoma (TC) in women during reproductive years compared with men and the increased risk associated with the therapeutic use of estrogens have suggested a pathogenetic role exerted by these steroids in the development of TC. In the present study, we evaluated the potential of 17beta-estradiol (E2), genistein (G), and 4-hydroxyta-moxifen (OHT) to regulate the expression of diverse estrogen target genes and the proliferation of human WRO, FRO, and ARO thyroid carcinoma cells, which were used as a model system. We have ascertained that ARO cells are devoid of estrogen receptors (ERs), whereas both WRO and FRO cells express a single variant of ERalpha that was neither transactivated, modulated, nor translocated into the nucleus upon treatment with ligands. However, E2, G, and OHT were able either to induce the transcriptional activity of c-fos promoter constructs, including those lacking the estrogen-responsive elements, or to increase c-fos, cyclin A, and D1 expression. It is noteworthy that we have demonstrated that the G protein-coupled receptor 30 (GPR30) and the mitogen-activated protein kinase (MAPK) pathway mediate both the up-regulation of c-fos and the growth response to E2, G, and OHT in TC cells studied, because these stimulatory effects were prevented by silencing GPR30 and using the MEK inhibitor 2'-amino-3'-methoxyflavone (PD 98059). Our findings provide new insight into the molecular mechanisms through which estrogens may induce the progression of TC.

Genetic interactions between Drosophila melanogaster menin and Jun/Fos

Menin is a tumor suppressor required to prevent multiple endocrine neoplasia in humans. Mammalian menin protein is associated with chromatin modifying complexes and has been shown to bind a number of nuclear proteins, including the transcription factor JunD. Menin shows bidirectional effects acting positively on c-Jun and negatively on JunD. We have produced protein null alleles of Drosophila menin (mnn1) and have over expressed the Mnn1 protein. Flies homozygous for protein-null mnn1 alleles are viable and fertile. Localized over-expression of Mnn1 causes defects in thoracic closure, a phenotype that sometimes results from insufficient Jun activity. We observed complex genetic interactions between mnn1 and jun in different developmental settings. Our data support the idea that one function of menin is to modulate Jun activity in a manner dependent on the cellular context.

Characteristics of the Danish families with multiple endocrine neoplasia type 1

Multiple endocrine neoplasia type 1 (MEN1) is caused by autosomal dominantly inherited mutations in the MEN1 gene. Here, we report 25 MEN1 mutations - of which 12 are novel - found in 36 Danish families with MEN1 or variant MEN1 disease. Furthermore, one FIHP family was found to have an earlier reported mutation. The mutations were predominantly found in exons 9 and 10 encoding the C-terminal part of menin. Seven of the mutations were missense mutations, changing conserved residues. Furthermore screening of 93 out of 153 consecutive patients with primary hyperparathyroidism (pHPT) identified five mutation carriers. Two of these belonged to known MEN1 families, whereas the only MEN1-related disease in the other three was pHPT. Screening of 96 consecutive patients with fore-/midgut endocrine tumours revealed five mutation carries out of 28 patients with sporadic gastrinomas, whereas no mutations were found in 68 patients with other fore-/midgut endocrine tumours. Moreover, screening of 60 consecutive patients with primary prolactinoma did not identify any mutation carriers. Our data indicate that MEN1 mutation screening is efficient in patients with familial MEN1. Screening should also be offered to patients with pHPT or gastrinomas after thorough investigation into the family history. In contrast, sporadic carcinoid tumours or primary prolactinomas are rarely associated with germ-line MEN1 mutations.