{"product_id":"men1-related-neuroendocrine-tumors-new-hope-from-preclinical-drug-research","title":"MEN1-Related Neuroendocrine Tumors: New Hope from Preclinical Drug Research","description":"\u003cp\u003eNeuroendocrine neoplasms (NENs) are rare tumors that can develop sporadically or as part of a hereditary syndrome called multiple endocrine neoplasia type 1 (MEN1). This review article from researchers at Hadassah-Hebrew University Medical Center and the University of Oxford examines why MEN1-related tumors are particularly difficult to treat and summarizes promising new targeted therapies being tested in preclinical (laboratory and animal) studies. These emerging treatments include epigenetic modulators (drugs that change gene activity without altering DNA), Wnt pathway antagonists, Ras signaling modulators, and Akt\/mTOR pathway inhibitors, as well as potential MEN1 gene replacement therapy. While these therapies are still in early development, they offer hope for patients whose tumors often resist conventional treatments.\u003c\/p\u003e\n\n\u003ch1\u003eMEN1-Related Neuroendocrine Tumors: New Hope from Preclinical Drug Research\u003c\/h1\u003e\n\n\u003ch2\u003eTable of Contents\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\u003ca href=\"#ddn-key-points\"\u003eKey Points\u003c\/a\u003e\u003c\/li\u003e\n\n  \u003cli\u003e\u003ca href=\"#background\"\u003eBackground: The MEN Syndromes\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#men1\"\u003eUnderstanding Multiple Endocrine Neoplasia Type 1\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#challenges\"\u003eWhy Current Treatments Fall Short in MEN1 Patients\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#science\"\u003eThe Science: How the MEN1 Gene and Menin Protein Work\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#methods\"\u003eStudy Methods: How Preclinical Research Is Conducted\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#epigenetic\"\u003eKey Findings: Epigenetic Modulators\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#wnt\"\u003eKey Findings: Wnt Pathway-Targeting β-Catenin Antagonists\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#ras\"\u003eKey Findings: Ras\/Raf\/MEK\/ERK Pathway Modulators\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#aktmTOR\"\u003eKey Findings: Akt\/mTOR Signaling Modulators\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#implications\"\u003eClinical Implications: What This Means for Patients\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#limitations\"\u003eLimitations: What These Studies Couldn't Prove\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#recommendations\"\u003eRecommendations for Patients and Researchers\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#ddn-faq\"\u003eFrequently Asked Questions\u003c\/a\u003e\u003c\/li\u003e\n\u003cli\u003e\u003ca href=\"#source\"\u003eSource Information\u003c\/a\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003c!-- ddn:keypoints:start --\u003e\n\u003ch2 id=\"ddn-key-points\"\u003eKey Points\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003eCurrent treatments for MEN1-related tumors are extrapolated from sporadic neuroendocrine tumors and have not been formally tested in MEN1 patients.\u003c\/li\u003e\n\u003cli\u003ePreclinical studies suggest epigenetic modulators, Wnt antagonists, and Akt\/mTOR inhibitors may offer future treatment options for MEN1-related neuroendocrine tumors.\u003c\/li\u003e\n\u003cli\u003eLoss of menin can enhance mTORC2-Akt activation, which may help explain different responses to everolimus in MEN1 patients.\u003c\/li\u003e\n\u003cli\u003ePancreatic and thymic neuroendocrine tumors cause about 50% and 24% of MEN1-related deaths, so proactive surveillance is critical.\u003c\/li\u003e\n\u003cli\u003eStandard genetic testing misses MEN1 mutations in 10–30% of patients; next-generation sequencing may improve diagnostic accuracy.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- ddn:keypoints:end --\u003e\n\n\n\u003ch2 id=\"background\"\u003eBackground: The MEN Syndromes\u003c\/h2\u003e\n\n\u003cp\u003eMultiple endocrine neoplasia (MEN) refers to a group of inherited disorders in which a single patient develops tumors in two or more endocrine (hormone-producing) glands. There are four recognized subtypes, called MEN1 through MEN4, each caused by specific gene mutations that lead to particular patterns of tumor development.\u003c\/p\u003e\n\n\u003cp\u003eThe most common of these conditions is MEN1. The other subtypes are less common and have distinct features:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMEN2\u003c\/strong\u003e is caused by mutations in the RET (rearranged during transfection) proto-oncogene. It is characterized by the combined appearance of medullary thyroid carcinoma, pheochromocytoma (a tumor of the adrenal gland), and parathyroid tumors.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMEN3\u003c\/strong\u003e (also called MEN2B) involves the same RET gene mutations but manifests with MEN2 features \u003cem\u003eexcept\u003c\/em\u003e parathyroid involvement. Instead, patients have a marfanoid body habitus (tall, slender build with long limbs) and ganglioneuromas (benign nerve tissue tumors) of the lips, tongue, and colon.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMEN4\u003c\/strong\u003e is caused by germline mutations in the CDKN1B tumor suppressor gene and commonly presents with parathyroid and pituitary neoplasias. Because MEN4 can sometimes be mistaken for MEN1, and because there is occasionally overlap between MEN2 tumors and MEN1, the authors provide a detailed comparison table of all MEN syndrome-related tumors.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2 id=\"men1\"\u003eUnderstanding Multiple Endocrine Neoplasia Type 1\u003c\/h2\u003e\n\n\u003cp\u003eMEN1, also known as Wermer's syndrome, was first described in the early twentieth century, but it wasn't until 1954 that Wermer documented a familial occurrence in which a father and four of his nine offspring were affected. Patients with MEN1 characteristically develop tumors of the parathyroid glands with primary hyperparathyroidism (seen in approximately \u003cstrong\u003e95%\u003c\/strong\u003e of patients), the anterior pituitary (approximately \u003cstrong\u003e30%\u003c\/strong\u003e), and the pancreatic islets (approximately \u003cstrong\u003e40%\u003c\/strong\u003e).\u003c\/p\u003e\n\n\u003cp\u003eLess commonly, patients may develop adrenal cortical adenomas or carcinomas, thyroid follicular adenomas, and extra-pancreatic neuroendocrine neoplasms such as duodenal gastrinomas, or gastric, thymic, and bronchial carcinoid tumors.\u003c\/p\u003e\n\n\u003cp\u003eMEN1 is an autosomal dominant disorder caused by mutations in the MEN1 tumor suppressor gene, which is located on chromosome 11q13.1. This gene encodes a 610-amino acid protein called \u003cstrong\u003emenin\u003c\/strong\u003e. However, in up to \u003cstrong\u003e10–30%\u003c\/strong\u003e of MEN1 patients, no mutation in the MEN1 gene can be detected using standard testing approaches. These routine methods may fail to identify mutations in non-coding and regulatory regions of the gene, or may miss phenocopies (conditions that look like MEN1 but are caused by other genes). \u003cstrong\u003eNext-generation sequencing (NGS)\u003c\/strong\u003e, a newer DNA sequencing technology, may help overcome these limitations and improve the strength and efficacy of genetic analysis.\u003c\/p\u003e\n\n\u003ch3\u003eTumor Patterns in MEN Syndromes\u003c\/h3\u003e\n\n\u003cp\u003eThe specific neuroendocrine tumors associated with each MEN syndrome include (with estimated penetrance rates):\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMEN1:\u003c\/strong\u003e\n    \u003cul\u003e\n      \u003cli\u003eEnteropancreatic tumors (30–70% of patients): gastrinomas (\u0026gt;40%), insulinomas (10–30%), glucagonomas (~3%), VIPomas (\u0026lt;1%), non-functioning pancreatic NENs (20–55%), somatostatinomas (extremely rare), and other hormone-secreting tumors\u003c\/li\u003e\n      \u003cli\u003e\"Foregut\" tumors (2–10%): thymic, bronchial, and gastric NENs\u003c\/li\u003e\n      \u003cli\u003ePituitary tumors (30–40%): prolactinomas (20%), plus ACTH-secreting, TSH-secreting, GH+PRL-secreting, GH-secreting, and non-functioning tumors (each 2–9%)\u003c\/li\u003e\n      \u003cli\u003ePheochromocytomas (\u0026lt;1%)\u003c\/li\u003e\n    \u003c\/ul\u003e\n  \u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMEN2:\u003c\/strong\u003e medullary thyroid carcinoma (90%), pheochromocytomas (50%), and occasionally ACTH-secreting pituitary tumors\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMEN3:\u003c\/strong\u003e medullary thyroid carcinoma (\u0026gt;90%), pheochromocytomas (40–50%), with rare ACTH-secreting pituitary tumors reported\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMEN4:\u003c\/strong\u003e duodenal and pancreatic NENs, bronchial and gastric NENs, and pituitary tumors (ACTH-secreting, GH-secreting, or non-functioning), along with a rare reported case of small-cell neuroendocrine cervical carcinoma\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2 id=\"challenges\"\u003eWhy Current Treatments Fall Short in MEN1 Patients\u003c\/h2\u003e\n\n\u003cp\u003eThe existing treatment options for NENs have never been formally evaluated specifically in MEN1 patients — they are simply extrapolated from studies of patients with non-hereditary (sporadic) NENs. There is a scarcity of evidence reporting on these anti-tumor therapies in MEN1-NENs patients specifically.\u003c\/p\u003e\n\n\u003cp\u003eTreating MEN1 patients is uniquely challenging for several reasons. Their tumors are typically \u003cstrong\u003emultiple and multicentric\u003c\/strong\u003e (appearing in several locations at once), pose a \u003cstrong\u003ehigher metastatic potential\u003c\/strong\u003e (greater risk of spreading), and are \u003cstrong\u003erelatively insensitive to treatment\u003c\/strong\u003e compared to sporadic tumors. The multi-focality of MEN1-NENs and their unpredictable malignant potential make it difficult to decide when and how extensively to perform curative surgery.\u003c\/p\u003e\n\n\u003cp\u003eAs a result, many patients require additional non-surgical treatments, including:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eBiotherapies: somatostatin analogues (SSAs)\u003c\/li\u003e\n  \u003cli\u003eMolecular-targeted therapies: mTOR inhibitors or tyrosine kinase (TK)\/receptor inhibitors\u003c\/li\u003e\n  \u003cli\u003ePeptide receptor radioligand therapy (PRRT)\u003c\/li\u003e\n  \u003cli\u003eChemotherapy\u003c\/li\u003e\n  \u003cli\u003eLiver-directed (loco-regional) therapies\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eHistorically, before 1980, about \u003cstrong\u003e80%\u003c\/strong\u003e of MEN1-related deaths were caused by gastrinoma-derived gastric acid hypersecretion, which led to multiple gastrointestinal ulcers, bleeding, and perforation. Fortunately, improvements in medications that control hypergastrinemia and related gastric acid hypersecretion have dramatically reduced deaths from these complications.\u003c\/p\u003e\n\n\u003cp\u003eHowever, the overall outlook remains serious. Most MEN1 patients with pancreatic or thymic NENs (\u003cstrong\u003e~70–90%\u003c\/strong\u003e) will require therapeutic intervention during their lifetime, including surgery and\/or systemic therapy, due to tumor progression, recurrence, or multi-focality. Despite advances in treatment, the life expectancy of MEN1 patients remains shorter than that of the general population — the \u003cstrong\u003emean age at death is approximately 55 years\u003c\/strong\u003e. Death most often results from malignant progression of pancreatic and thymic NENs, which are responsible for approximately \u003cstrong\u003e50%\u003c\/strong\u003e and \u003cstrong\u003e24%\u003c\/strong\u003e of fatalities, respectively.\u003c\/p\u003e\n\n\u003ch2 id=\"science\"\u003eThe Science: How the MEN1 Gene and Menin Protein Work\u003c\/h2\u003e\n\n\u003cp\u003eSince the MEN1 gene was discovered in 1997, scientists have worked hard to understand the functions of its protein product, menin. Using biochemistry, proteomics, genetics, and genomics approaches, researchers have identified many potential roles for menin, which all converge on \u003cstrong\u003egene expression regulation\u003c\/strong\u003e — the process by which genes are turned on or off.\u003c\/p\u003e\n\n\u003cp\u003eMenin is expressed throughout the body and acts as a \u003cstrong\u003enuclear key scaffold protein\u003c\/strong\u003e — meaning it acts as a platform that brings together other proteins to control gene activity. Interestingly, menin has opposing roles in different organs: it acts as a bona fide tumor suppressor in endocrine organs, yet is essential for promoting leukemia (blood cancer) in mouse models. This dual behavior likely results from menin's ability to regulate gene expression in opposite directions and to interact with many different proteins and signaling pathways involved in cell behavior, including gene transcription, genome stability, cell division, cell cycle control, and epigenetic regulation.\u003c\/p\u003e\n\n\u003cp\u003eSpecifically, in the cell nucleus, menin:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eInteracts with the transcription factor \u003cstrong\u003eJunD\u003c\/strong\u003e and the protein arginine methyltransferase \u003cstrong\u003ePRMT5\u003c\/strong\u003e to suppress (turn off) transcription of target genes\u003c\/li\u003e\n  \u003cli\u003eBinds to chromatin-modifying protein complexes, such as the histone modifiers \u003cstrong\u003eMLL1 and MLL2\u003c\/strong\u003e (mixed lineage leukemia proteins) and \u003cstrong\u003eSmad3\u003c\/strong\u003e (a TGF-β signaling component), to promote (turn on) transcription of target genes\u003c\/li\u003e\n  \u003cli\u003eRestricts Wnt pathway target gene transcription by blocking \u003cstrong\u003eβ-catenin\u003c\/strong\u003e from entering the nucleus\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eIn the cytoplasm, menin:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eBinds to \u003cstrong\u003eAkt\u003c\/strong\u003e, inhibiting the mechanistic target of rapamycin (mTOR) pathway downstream of PI3K\u003c\/li\u003e\n  \u003cli\u003eHampers \u003cstrong\u003eERK-dependent K-Ras phosphorylation\u003c\/strong\u003e, preventing the interaction between the guanine nucleotide exchange factor SOS (son of sevenless) and K-Ras, thereby reducing cell proliferation signals\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eWhen menin is lost or non-functional (as in MEN1 patients), these regulatory brakes are removed, and cells can grow unchecked.\u003c\/p\u003e\n\n\u003ch2 id=\"methods\"\u003eStudy Methods: How Preclinical Research Is Conducted\u003c\/h2\u003e\n\n\u003cp\u003ePreclinical \u003cem\u003ein vitro\u003c\/em\u003e (test tube\/cell culture) and \u003cem\u003ein vivo\u003c\/em\u003e (living animal) models of cancer are essential tools for studying gene functions, understanding how tumors begin and progress, and testing novel therapies before they reach human clinical trials.\u003c\/p\u003e\n\n\u003cp\u003eSeveral MEN1 animal models have been created by introducing loss-of-function mutations in the mouse or rat equivalents of the human MEN1 gene. These animal models closely resemble the tumor spectrum and hormonal changes seen in human MEN1 disease, although individual tumor behavior can vary from animal to animal.\u003c\/p\u003e\n\n\u003cp\u003eIt is important to note that most research on MEN1-NENs to date has focused almost exclusively on pancreatic tumors from MEN1 mouse models. This is because pancreatic NENs are the most frequent tumors studied in MEN1-NENs models so far. The authors also briefly describe relevant data on MEN1-pituitary tumors, reflecting the recent nomenclature shift from \"pituitary adenomas\" to \"pituitary neuroendocrine neoplasms.\"\u003c\/p\u003e\n\n\u003cp\u003eThis increased understanding of menin's function has allowed researchers to begin preclinical development of menin-targeted therapies for NENs.\u003c\/p\u003e\n\n\u003ch2 id=\"epigenetic\"\u003eKey Findings: Epigenetic Modulators\u003c\/h2\u003e\n\n\u003cp\u003eEpigenetic mechanisms are changes that affect gene activity without changing the DNA sequence itself — like adding or removing chemical \"tags\" on DNA or its associated histone proteins. Menin plays a role in gene transcription through epigenetic regulation, including histone modifications. For example, menin interacts with histone-modifying proteins such as histone methyltransferases (MLL1 and PRMT5) and acetyltransferase complexes (HDACs) to regulate the expression of tumor suppressor genes, including \u003cem\u003eCDKN1B\u003c\/em\u003e and \u003cem\u003eGAS1\u003c\/em\u003e.\u003c\/p\u003e\n\n\u003cp\u003eSeveral classes of epigenetic-targeting drugs have shown promise in preclinical studies:\u003c\/p\u003e\n\n\u003ch3\u003eBET Inhibitors (JQ1 and CPI203)\u003c\/h3\u003e\n\n\u003cp\u003eThe bromo and extra terminal domain (BET) family of proteins bind to acetylated histone residues to promote gene transcription. \u003cstrong\u003eJQ1\u003c\/strong\u003e, a BET inhibitor, showed significant anti-tumor activity in laboratory studies:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eIn vitro (cell culture) studies:\u003c\/strong\u003e JQ1 decreased proliferation and increased apoptosis (programmed cell death) of pancreatic, pituitary, and bronchial NEN cell lines. It also reduced ACTH secretion from ACTH-secreting pituitary cell lines (AtT20 cells).\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eIn vivo (animal) studies:\u003c\/strong\u003e In a pancreatic β-cell-specific conditional Men1-knockout mouse model that develops pNENs, JQ1 decreased proliferation and increased apoptosis of pancreatic neuroendocrine tumors.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eAnother BET inhibitor, \u003cstrong\u003eCPI203\u003c\/strong\u003e, was also reported to reduce pancreatic NEN proliferation in a BON-1 xenograft model (human tumor cells implanted into mice).\u003c\/p\u003e\n\n\u003ch3\u003eHistone Deacetylase Inhibitors (HDACi)\u003c\/h3\u003e\n\n\u003cp\u003eThe potential utility of HDAC inhibitors has been demonstrated mainly in sporadic (non-hereditary) NENs, with limited studies in MEN1-NENs models. Notable findings include:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eLMK-235\u003c\/strong\u003e, an inhibitor of HDAC5, was reported as a potential therapeutic target in pancreatic NENs.\u003c\/li\u003e\n  \u003cli\u003eThe class I HDAC1\/3 inhibitor \u003cstrong\u003eetinostat\u003c\/strong\u003e inhibited \"master regulator\" proteins in \u003cstrong\u003e42%\u003c\/strong\u003e of cultured rodent islet tumor cells and reduced tumor growth in a small intestinal NEN xenograft mouse model.\u003c\/li\u003e\n  \u003cli\u003eThe HDAC inhibitor \u003cstrong\u003esuberoylanilide hydroxamic acid (SAHA)\u003c\/strong\u003e, also known as vorinostat, decreased proliferation and increased apoptosis in a GH3 rat pituitary NEN cell line.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eSome HDAC inhibitors — vorinostat (SAHA), romidepsin, and panobinostat — have already been approved by the U.S. Food and Drug Administration (FDA) for specific blood cancers (hematologic malignancies). However, limited efficacy has been shown in patients with sporadic pancreatic NENs.\u003c\/p\u003e\n\n\u003ch3\u003eRbp2 (H3K4 Demethylase) Ablation\u003c\/h3\u003e\n\n\u003cp\u003eMenin forms a complex with MLL and Ash2 proteins to promote \u003cstrong\u003ehistone 3, lysine 4 (H3K4) methylation\u003c\/strong\u003e, which increases the expression of anti-proliferative genes, including cyclin-dependent kinase (CDK) inhibitors that encode p27 and p18. Preclinical studies demonstrated that genetically removing \u003cstrong\u003eretinoblastoma binding protein 2 (Rbp2)\u003c\/strong\u003e — a H3K4 demethylase that reverses this effect — can reduce the proliferation of pancreatic NEN cells and reduce pancreatic tumor burden in a Men1 conditional knockout mouse model. Rbp2 expression has been found to be elevated in NENs, making it a potential therapeutic target.\u003c\/p\u003e\n\n\u003cp\u003eThe authors note that although epigenetic modulators seem attractive as potential therapies for NEN patients, further clinical studies using selective compounds — alone or in combination with other anti-cancer agents — are needed to understand their real therapeutic potential, especially for MEN1-NENs patients.\u003c\/p\u003e\n\n\u003ch2 id=\"wnt\"\u003eKey Findings: Wnt Pathway-Targeting β-Catenin Antagonists\u003c\/h2\u003e\n\n\u003cp\u003eMenin normally reduces cell proliferation through the Wnt\/β-catenin signaling pathway by promoting β-catenin phosphorylation and its transfer out of the nucleus. When menin is absent, β-catenin accumulates in the nucleus, leading to activation of target genes that promote cell growth.\u003c\/p\u003e\n\n\u003cp\u003eThe interaction between menin and Wnt signaling is complex, however. Research suggests menin may either promote or inhibit Wnt signaling depending on the stage of islet tumor development and the cell type involved. For example:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eMenin was shown to be essential for canonical Wnt\/β-catenin signaling in cultured rodent islet tumor cells, yet it may also inhibit Wnt signaling to prevent β cells from early-stage tumorigenesis.\u003c\/li\u003e\n  \u003cli\u003eIn Men1-null mouse embryonic fibroblasts (MEFs), menin promoted nuclear export of β-catenin, suppressing its transcriptional activity.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eDespite these complexities, several key experiments support the potential of Wnt pathway modulators:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eCao et al. (2009):\u003c\/strong\u003e Using Men1-null MEFs and insulinoma tissues from β-cell-specific Men1-knockout mice (which show nuclear accumulation of β-catenin), researchers demonstrated that overexpressing menin reduces β-catenin nuclear accumulation and its transcriptional activity. Menin directly binds to β-catenin and carries it out of the nucleus via nuclear-cytoplasmic shuttling.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eJiang et al. (2014):\u003c\/strong\u003e In a MEN1-deficient mouse model developing pancreatic NENs (RIP-Cre mice with pancreatic β-cell conditional knockout of menin), additionally knocking out β-catenin \u003cstrong\u003edecreased the number and size\u003c\/strong\u003e of pancreatic tumors and \u003cstrong\u003eincreased mouse survival\u003c\/strong\u003e.\u003c\/li\u003e\n  \u003cli\u003eThe β-catenin antagonist \u003cstrong\u003ePKF115-584\u003c\/strong\u003e decreased pancreatic NEN cell proliferation, suggesting that Wnt-signaling modulators may provide a novel treatment approach for MEN1-NENs patients.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eHowever, the authors emphasize that the interactions between menin and Wnt\/β-catenin remain largely unexplored and require further research.\u003c\/p\u003e\n\n\u003ch2 id=\"ras\"\u003eKey Findings: Ras\/Raf\/MEK\/ERK Pathway Modulators\u003c\/h2\u003e\n\n\u003cp\u003eThe RAS-RAF-MEK-ERK (MAPK) pathway is a chain of proteins that transmits growth signals from the cell surface to the nucleus. Aberrant activation of this pathway is implicated in numerous cancers.\u003c\/p\u003e\n\n\u003cp\u003eStudies have shown that NENs display activating mutations in the rat sarcoma (Ras) family of signal-transducing genes, over-activity of p21(Ras) signaling pathways, or constitutive activation of upstream or downstream effectors of Ras, including growth factor receptors, PI(3)-kinase, and Raf\/mitogen-activated protein kinases. Ras also depends on protein kinase C delta (PKCδ)-mediated survival pathways.\u003c\/p\u003e\n\n\u003cp\u003eKey preclinical findings include:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eKim et al. (1999):\u003c\/strong\u003e Menin overexpression in pro-oncogenic RAS-transformed murine NIH3T3 cells decreased cell proliferation and tumor growth in athymic mice, restraining RAS oncogenic effects.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eChamberlain et al. (2014):\u003c\/strong\u003e K-Ras, a member of the Ras family, paradoxically suppressed growth in pancreatic endocrine cells in a mouse model. This effect depended on the antiproliferative Ras effector \u003cstrong\u003eRASSF1A\u003c\/strong\u003e and on menin's blockade of the Raf\/MAPK pathway. Stimulation of ERK1\/2 phosphorylation combined with a menin inhibitor synergistically enhanced proliferation, while inhibition of MAPK signaling created a lethal effect when menin was lost. These insights suggest potential strategies for targeting menin-sensitive endocrine tumors.\u003c\/li\u003e\n  \u003cli\u003eA recent study using an ATII-specific Kras\u003csup\u003eG12D\/+\u003c\/sup\u003e\/Men1\u003csup\u003e−\/−\u003c\/sup\u003e genetically engineered mouse model demonstrated that menin deficiency affects tumor behavior — though the full details of this work are beyond the scope of the published review excerpt.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2 id=\"aktmTOR\"\u003eKey Findings: Akt\/mTOR Signaling Modulators\u003c\/h2\u003e\n\n\u003cp\u003eThe mTOR pathway is a major regulator of cell growth and metabolism. The mTORC1 inhibitor \u003cstrong\u003eRAD001 (everolimus)\u003c\/strong\u003e is already in clinical use for non-MEN1 NENs of various origins. However, data specifically on menin and Akt\/mTOR pathway signaling in MEN1 patients has been limited. Several recent studies have begun to fill this gap:\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eRazmara et al. (2018):\u003c\/strong\u003e Researchers assessed the impact of menin expression (alone or combined with rapamycin treatment) on cell proliferation using menin-silenced BON-1 cells. They found that lack of menin enhanced mTORC2-Akt activation, as well as rapamycin-induced pAkt (phosphorylated Akt). A direct negative regulation between menin and rapamycin-mediated mTORC2-Akt activation was observed. This suggests that \u003cstrong\u003emenin is essential in mTORC1\/C2 crosstalk\u003c\/strong\u003e and may influence the response to mTOR inhibitors in pancreatic NEN patients.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eWang et al. (2011):\u003c\/strong\u003e Using a Men1\u003csup\u003e+\/−\u003c\/sup\u003e mouse model bearing islet adenomas, researchers showed that menin is an important negative regulator of Akt kinase activity. Immunohistochemical staining for pAkt(S473) and menin in islet adenomas from 18-month-old Men1\u003csup\u003e+\/−\u003c\/sup\u003e mice (compared with wild-type mice) demonstrated that \u003cstrong\u003epAkt(S473) expression in islet adenomas correlates with loss of menin expression\u003c\/strong\u003e. This means menin normally downregulates AKT activity and inhibits both Akt-induced proliferation and Akt's anti-apoptosis (cell-survival) effects.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eWong et al.\u003c\/strong\u003e recently demonstrated that the co-existence of certain factors (the text excerpt cuts off here, but this line of research continues to explore menin's interactions with growth signaling pathways).\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2 id=\"implications\"\u003eClinical Implications: What This Means for Patients\u003c\/h2\u003e\n\n\u003cp\u003eThese preclinical findings, while early, have important implications for the future treatment of MEN1-related neuroendocrine tumors:\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNew targeted therapy options:\u003c\/strong\u003e The studies point to several classes of drugs — BET inhibitors (JQ1, CPI203), HDAC inhibitors (LMK-235, etinostat, SAHA), Wnt\/β-catenin antagonists (PKF115-584), and Akt\/mTOR modulators — that could one day be tested in clinical trials for MEN1-NENs patients.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eUnderstanding drug resistance:\u003c\/strong\u003e The finding that menin loss enhances mTORC2-Akt activation may help explain why some MEN1 patients respond differently to everolimus (an mTOR inhibitor already used for sporadic NENs). This knowledge could guide more personalized treatment decisions.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eCombination therapy potential:\u003c\/strong\u003e The research suggests that combining epigenetic modulators with other anti-cancer agents might be more effective than single drugs alone, and this is an important direction for future studies.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eGene replacement therapy:\u003c\/strong\u003e The authors list MEN1 gene replacement therapy as a potential future approach, though this remains in very early stages of investigation.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eThe authors emphasize that treatment decisions for MEN1-NENs patients require experienced multi-disciplinary teams at referral centers of excellence, given the complexity of these cases.\u003c\/p\u003e\n\n\u003ch2 id=\"limitations\"\u003eLimitations: What These Studies Couldn't Prove\u003c\/h2\u003e\n\n\u003cp\u003eIt is crucial for patients to understand the limitations of this research:\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePreclinical only:\u003c\/strong\u003e All of the therapies discussed in this review are at the preclinical (laboratory and animal) stage. None have yet been formally evaluated in clinical trials specifically for MEN1-NENs patients.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eExtrapolation from sporadic NENs:\u003c\/strong\u003e Current clinical treatments for MEN1 patients are extrapolated from studies of non-MEN1 NENs patients, and there is very little direct evidence for these therapies in MEN1-NENs.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eLimited tumor model types:\u003c\/strong\u003e Most research to date has focused on pancreatic NENs from MEN1 mouse models. Less is known about whether these findings apply to other MEN1-associated tumors, such as thymic, bronchial, gastric, or pituitary NENs.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eComplex biology:\u003c\/strong\u003e Menin's roles are tissue-specific and sometimes contradictory (it can act as a tumor suppressor in endocrine organs yet promote leukemia in blood cells). This complexity makes it difficult to predict how menin-targeted therapies will behave in different contexts.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eUndetected mutations:\u003c\/strong\u003e In 10–30% of MEN1 patients, standard genetic testing cannot identify a MEN1 mutation, which complicates both diagnosis and research into genotype-phenotype correlations.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eWnt signaling uncertainty:\u003c\/strong\u003e The interactions between menin and the Wnt\/β-catenin pathway are noted as \"yet to be explored,\" meaning conclusions about this pathway remain preliminary.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2 id=\"recommendations\"\u003eRecommendations for Patients and Researchers\u003c\/h2\u003e\n\n\u003cp\u003eFor patients living with MEN1, this review reinforces several important points:\u003c\/p\u003e\n\n\u003col\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSeek specialized care:\u003c\/strong\u003e MEN1 is a complex condition that requires management by experienced multi-disciplinary teams at referral centers of excellence (such as ENETS Centers of Excellence). These teams can coordinate surgery, medical therapy, and surveillance appropriately.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eUnderstand the current standard of care:\u003c\/strong\u003e Existing treatments — somatostatin analogues, everolimus, PRRT, chemotherapy, and liver-directed therapies — remain the mainstays of treatment. The new therapies discussed in this review are not yet available outside of clinical trials.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eConsider genetic counseling:\u003c\/strong\u003e Since 10–30% of MEN1 patients have no detectable mutation by standard testing, next-generation sequencing may offer improved diagnostic accuracy. Genetic counseling is recommended for families affected by MEN1.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eWatch for clinical trials:\u003c\/strong\u003e As epigenetic modulators, Wnt antagonists, and other targeted agents move from preclinical testing toward clinical trials, eligible patients may wish to discuss participation with their specialists.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eRecognize the seriousness of pancreatic and thymic tumors:\u003c\/strong\u003e Because pancreatic and thymic NENs account for roughly 50% and 24% of MEN1-related deaths respectively, proactive surveillance and timely intervention for these tumors is critical.\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003cp\u003eFor researchers, the authors recommend:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eFurther clinical studies using selective epigenetic compounds, alone or in combination with other anti-cancer agents, to understand their real therapeutic potential\u003c\/li\u003e\n  \u003cli\u003eMore research on MEN1-pituitary tumors, which have been less studied than pancreatic NENs\u003c\/li\u003e\n  \u003cli\u003eContinued exploration of the complex interplay between menin, Wnt\/β-catenin signaling, and other pathways\u003c\/li\u003e\n  \u003cli\u003eDevelopment of MEN1 gene replacement therapy as a potential future treatment strategy\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eThe road from preclinical discovery to approved therapy is long and uncertain. However, the progress described in this review represents an important step forward in understanding MEN1-related NENs and developing therapies designed specifically for the unique biology of these tumors.\u003c\/p\u003e\n\n\u003c!-- ddn:faq:start --\u003e\n\u003ch2 id=\"ddn-faq\"\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003ch3\u003eWhat is multiple endocrine neoplasia type 1 (MEN1)?\u003c\/h3\u003e\n\u003cp\u003eMEN1 is an inherited disorder caused by mutations in the MEN1 tumor suppressor gene. Patients typically develop tumors of the parathyroid glands, pancreas, and pituitary, along with other neuroendocrine tumors. It is autosomal dominant, meaning children of an affected parent have a 50% chance of inheriting the condition.\u003c\/p\u003e\n\u003ch3\u003eWhy are MEN1-related tumors harder to treat than sporadic tumors?\u003c\/h3\u003e\n\u003cp\u003eMEN1 tumors are often multiple and appear in several locations at once, have a higher risk of spreading, and are relatively insensitive to standard treatments. No existing therapy has been formally tested specifically in MEN1 patients, so current approaches are extrapolated from studies of patients with sporadic, non-hereditary neuroendocrine tumors.\u003c\/p\u003e\n\u003ch3\u003eAre there new targeted therapies being developed for MEN1-related neuroendocrine tumors?\u003c\/h3\u003e\n\u003cp\u003eYes, several classes of drugs are being studied in laboratory and animal research, including BET inhibitors, HDAC inhibitors, Wnt pathway antagonists, and Akt\/mTOR modulators. These are all at the preclinical stage and have not yet been tested in clinical trials for MEN1 patients.\u003c\/p\u003e\n\u003ch3\u003eWhat does it mean that a therapy is 'preclinical'?\u003c\/h3\u003e\n\u003cp\u003ePreclinical means the therapy has been tested in cell cultures and animal models, but not yet in human clinical trials. It is still early in development and not available for patients outside of a research study. Many promising preclinical treatments never become approved drugs, so results must be interpreted cautiously.\u003c\/p\u003e\n\u003ch3\u003eCan genetic testing always detect MEN1?\u003c\/h3\u003e\n\u003cp\u003eNo. Standard genetic testing fails to identify a MEN1 mutation in 10–30% of patients who have clinical features of MEN1. This may be because mutations are located in non-coding or regulatory regions, or because the condition is caused by another gene. Next-generation sequencing may improve detection.\u003c\/p\u003e\n\u003ch3\u003eShould I consider participating in clinical trials for MEN1 treatments?\u003c\/h3\u003e\n\u003cp\u003eIf you have MEN1, discuss participation in clinical trials with your specialist. The new therapies described in the research are not yet available outside of trials. Your healthcare team can help determine whether you meet eligibility criteria and whether trial participation is appropriate for your situation.\u003c\/p\u003e\n\u003ch3\u003eWhen should a patient with MEN1-related neuroendocrine tumors seek a second opinion?\u003c\/h3\u003e\n\u003cp\u003ePatients with MEN1-related neuroendocrine tumors should consider a second opinion because standard treatments are extrapolated from sporadic tumors and may not address the unique challenges of MEN1—multiple, multicentric tumors with higher metastatic potential and relative treatment resistance. Management by an experienced multi-disciplinary team at a referral center is recommended. Second opinions can also clarify genetic testing, since 10–30% of MEN1 patients have no detectable mutation by standard methods, and identify whether any clinical trials of new targeted therapies are appropriate. Diagnostic Detectives Network provides independent expert second opinions.\u003c\/p\u003e\n\u003c!-- ddn:faq:end --\u003e\n\n\u003ch2 id=\"source\"\u003eSource Information\u003c\/h2\u003e\n\n\u003cp\u003e\u003cstrong\u003eOriginal article title:\u003c\/strong\u003e Preclinical drug studies in MEN1-related neuroendocrine neoplasms\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors:\u003c\/strong\u003e Simona Grozinsky-Glasberg, Kate E Lines, Shani Avniel-Polak, Chas Bountra, and Rajesh V Thakker\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eJournal:\u003c\/strong\u003e Endocrine-Related Cancer (2020) 27, R345–R355\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eAffiliations:\u003c\/strong\u003e Neuroendocrine Tumor Unit, ENETS Center of Excellence, Department of Endocrinology and Metabolism, Hadassah-Hebrew University Medical Center, Jerusalem, Israel; Academic Endocrine Unit, Radcliffe Department of Medicine, University of Oxford, Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Churchill Hospital, Oxford, UK; Structural Genomics Consortium, University of Oxford, Oxford, UK\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDOI:\u003c\/strong\u003e https:\/\/doi.org\/10.1530\/ERC-20-0127\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eNote:\u003c\/strong\u003e This patient-friendly article is based on peer-reviewed research. It has been written to be accessible to a general audience while preserving the key data, findings, and conclusions of the original scientific publication. Patients should always consult their healthcare team for medical advice specific to their situation.\u003c\/p\u003e","brand":"DiagnosticDetectives.Com","offers":[{"title":"Default Title","offer_id":47461163729052,"sku":null,"price":0.0,"currency_code":"RUB","in_stock":true}],"url":"https:\/\/diagnosticdetectives.ru\/products\/men1-related-neuroendocrine-tumors-new-hope-from-preclinical-drug-research","provider":"DiagnosticDetectives.Com","version":"1.0","type":"link"}