PMID- 37492626 OWN - NLM STAT- MEDLINE DCOM- 20230727 LR - 20230729 IS - 2767-9764 (Electronic) IS - 2767-9764 (Linking) VI - 3 IP - 7 DP - 2023 Jul TI - Clinically Defined Mutations in MEN1 Alter Its Tumor-suppressive Function Through Increased Menin Turnover. PG - 1318-1334 LID - 10.1158/2767-9764.CRC-22-0522 [doi] AB - Loss of the tumor suppressor protein menin is a critical event underlying the formation of neuroendocrine tumors (NET) in hormone-expressing tissues including gastrinomas. While aberrant expression of menin impairs its tumor suppression, few studies explore the structure-function relationship of clinical multiple endocrine neoplasia, type 1 (MEN1) mutations in the absence of a complete LOH at both loci. Here, we determined whether clinical MEN1 mutations render nuclear menin unstable and lead to its functional inactivation. We studied the structural and functional implications of two clinical MEN1 mutations (R516fs, E235K) and a third variant (A541T) recently identified in 10 patients with gastroenteropancreatic (GEP)-NETs. We evaluated the subcellular localization and half-lives of the mutants and variant in Men1-null mouse embryo fibroblast cells and in hormone-expressing human gastric adenocarcinoma and NET cell lines. Loss of menin function was assessed by cell proliferation and gastrin gene expression assays. Finally, we evaluated the effect of the small-molecule compound MI-503 on stabilizing nuclear menin expression and function in vitro and in a previously reported mouse model of gastric NET development. Both the R516fs and E235K mutants exhibited severe defects in total and subcellular expression of menin, and this was consistent with reduced half-lives of these mutants. Mutated menin proteins exhibited loss of function in suppressing tumor cell proliferation and gastrin expression. Treatment with MI-503 rescued nuclear menin expression and attenuated hypergastrinemia and gastric hyperplasia in NET-bearing mice. Clinically defined MEN1 mutations and a germline variant confer pathogenicity by destabilizing nuclear menin expression. SIGNIFICANCE: We examined the function of somatic and germline mutations and a variant of MEN1 sequenced from gastroenteropancreatic NETs. We report that these mutations and variant promote tumor cell growth and gastrin expression by rendering menin protein unstable and prone to increased degradation. We demonstrate that the menin-MLL (mixed lineage leukemia) inhibitor MI-503 restores menin protein expression and function in vitro and in vivo, suggesting a potential novel therapeutic approach to target MEN1 GEP-NETs. CI - (c) 2023 The Authors; Published by the American Association for Cancer Research. FAU - Duan, Suzann AU - Duan S AUID- ORCID: 0000-0002-5129-0736 AD - Division of Gastroenterology and Hepatology, Department of Medicine, University of Arizona College of Medicine, Tucson, Arizona. FAU - Sheriff, Sulaiman AU - Sheriff S AUID- ORCID: 0009-0007-2491-2273 AD - Division of Gastroenterology and Hepatology, Department of Medicine, University of Arizona College of Medicine, Tucson, Arizona. FAU - Elvis-Offiah, Uloma B AU - Elvis-Offiah UB AUID- ORCID: 0000-0003-2135-170X AD - Division of Gastroenterology and Hepatology, Department of Medicine, University of Arizona College of Medicine, Tucson, Arizona. AD - Department of Physiology, University of Arizona College of Medicine, Tucson, Arizona. FAU - Witten, Brandon L AU - Witten BL AUID- ORCID: 0009-0005-1033-6485 AD - Division of Gastroenterology and Hepatology, Department of Medicine, University of Arizona College of Medicine, Tucson, Arizona. FAU - Sawyer, Travis W AU - Sawyer TW AUID- ORCID: 0000-0002-6911-0289 AD - Department of Optical Sciences, University of Arizona Wyant College of Optical Sciences, Tucson, Arizona. FAU - Sundaresan, Sinju AU - Sundaresan S AUID- ORCID: 0000-0003-1504-8413 AD - Department of Physiology, Midwestern University, Downers Grove, Illinois. FAU - Cierpicki, Tomasz AU - Cierpicki T AUID- ORCID: 0000-0003-2058-0658 AD - Department of Pathology, University of Michigan, Ann Arbor, Michigan. FAU - Grembecka, Jolanta AU - Grembecka J AUID- ORCID: 0000-0002-6180-9095 AD - Department of Pathology, University of Michigan, Ann Arbor, Michigan. FAU - Merchant, Juanita L AU - Merchant JL AUID- ORCID: 0000-0002-6559-8184 AD - Division of Gastroenterology and Hepatology, Department of Medicine, University of Arizona College of Medicine, Tucson, Arizona. AD - Department of Physiology, University of Arizona College of Medicine, Tucson, Arizona. LA - eng GR - R01 CA160467/CA/NCI NIH HHS/United States GR - R01 DK045729/DK/NIDDK NIH HHS/United States PT - Journal Article PT - Research Support, N.I.H., Extramural DEP - 20230724 PL - United States TA - Cancer Res Commun JT - Cancer research communications JID - 9918281580506676 RN - 0 (Gastrins) RN - 0 (Hormones) RN - 0 (Men1 protein, mouse) RN - 0 (Proto-Oncogene Proteins) RN - 0 (Transcription Factors) RN - 0 (MEN1 protein, human) RN - Gastro-enteropancreatic neuroendocrine tumor SB - IM MH - Animals MH - Humans MH - Mice MH - Gastrins/genetics MH - Hormones MH - *Multiple Endocrine Neoplasia Type 1/genetics MH - Mutation MH - *Pancreatic Neoplasms/genetics MH - Proto-Oncogene Proteins/genetics MH - Transcription Factors/genetics PMC - PMC10364643 EDAT- 2023/07/26 06:43 MHDA- 2023/07/27 06:42 PMCR- 2023/07/24 CRDT- 2023/07/26 03:55 PHST- 2022/12/29 00:00 [received] PHST- 2023/05/02 00:00 [revised] PHST- 2023/06/26 00:00 [accepted] PHST- 2023/07/27 06:42 [medline] PHST- 2023/07/26 06:43 [pubmed] PHST- 2023/07/26 03:55 [entrez] PHST- 2023/07/24 00:00 [pmc-release] AID - CRC-22-0522 [pii] AID - 10.1158/2767-9764.CRC-22-0522 [doi] PST - epublish SO - Cancer Res Commun. 2023 Jul 24;3(7):1318-1334. doi: 10.1158/2767-9764.CRC-22-0522. eCollection 2023 Jul.