Proposition of adjustments to the ACMG-AMP framework for the interpretation of MEN1 missense variants.

In 2015, the ACMG-AMP guidelines provided a general procedure for the objective and reproducible classification of genomic variants. While the benefits of this framework are of major importance, its adaptation for locus-specific use is needed. Multiple Endocrine Neoplasia type 1 (MEN1) occurs due to inactivating mutations in the tumour suppressor gene MEN1, including 20% of missense variants. The classification of these variants may be extremely challenging. Here, we compared the interpretation of the 122 MEN1 missense variants, identified in the French population over the past 15 years by the TENGEN network (French oncogenetics network of neuroendocrine tumors) versus by using the ACMG-AMP guidelines, and analyzed the causes of discordance. A total of 59.8% of missense variants were termed as (likely)-pathogenic variants by TENGEN versus only 28.7% using ACMG-AMP guidelines. Actually, 53.4% (39/73) of TENGEN (likely)-pathogenic variants were declassified in variant of uncertain significance (VUS) by using ACMG-AMP guidelines, thereby affecting the clinical management of patients and their families. Twenty of these ACMG-AMP VUS were found in patients with a clinically authentic MEN1 disease. Here, TENGEN proposes adjustments to the ACMG-AMP framework for the interpretation of MEN1 missense variants. These propositions merge both the classification systems, and are particularly interesting, as MEN1 is included in the ACMG secondary findings list for reporting in clinical genomic sequencing.

Messenger RNA Life-Cycle in Cancer Cells: Emerging Role of Conventional and Non-Conventional RNA-Binding Proteins?

Functional specialization of cells and tissues in metazoans require specific gene expression patterns. Biological processes, thus, need precise temporal and spatial coordination of gene activity. Regulation of the fate of messenger RNA plays a crucial role in this context. In the present review, the current knowledge related to the role of RNA-binding proteins in the whole mRNA life-cycle is summarized. This field opens up a new angle for understanding the importance of the post-transcriptional control of gene expression in cancer cells. The emerging role of non-classic RNA-binding proteins is highlighted. The goal of this review is to encourage readers to view, through the mRNA life-cycle, novel aspects of the molecular basis of cancer and the potential to develop RNA-based therapies.

The serrated neoplasia pathway of colorectal tumors: Identification of MUC5AC hypomethylation as an early marker of polyps with malignant potential.

The serrated neoplasia pathway accounts for 20-30% of colorectal cancers (CRC), which are characterized by extensive methylation (CpG island methylation phenotype, CIMP), frequent BRAF mutation and high microsatellite instability (MSI). We recently identified MUC5AC mucin gene hypomethylation as a specific marker of MSI CRC. The early identification of preneoplastic lesions among serrated polyps is currently challenging. Here, we performed a detailed pathological and molecular analysis of a large series of colorectal serrated polyps and evaluated the usefulness of mucin genes MUC2 and MUC5AC to differentiate serrated polyps and to identify lesions with malignant potential. A series of 330 colorectal polyps including 218 serrated polyps [42 goblet cell-rich hyperplastic polyps (GCHP), 68 microvesicular hyperplastic polyps (MVHP), 100 sessile serrated adenoma (SSA) and eight traditional serrated adenoma (TSA)] and 112 conventional adenomas was analyzed for BRAF/KRAS mutations, MSI, CIMP, MLH1 and MGMT methylation, and MUC2 and MUC5AC expression and methylation. We show that MUC5AC hypomethylation is an early event in the serrated neoplasia pathway, and specifically detects MVHP and SSA, arguing for a filiation between MVHP, SSA and CIMP-H/MSI CRC, whereas GCHP and TSA arise from a distinct pathway. Moreover, MUC5AC hypomethylation specifically identified serrated lesions with BRAF mutation, CIMP-H or MSI, suggesting that it may be useful to identify serrated neoplasia pathway-related precursor lesions. Our data suggest that MVHP should be recognized among HP and require particular attention.

CA-125, but not galectin-3, complements CA 19-9 for discriminating ductal adenocarcinoma versus non-malignant pancreatic diseases.

BACKGROUND/OBJECTIVES: CA 19-9 is the gold standard biomarker of pancreatic adenocarcinoma despite several weaknesses in particular a high rate of false positives or negatives. CA-125 corresponding to MUC16 and galectin-3, a lectin able to interact with mucin-associated carbohydrates, are tumor-associated proteins. We investigated whether combined measurement of CA 19-9, galectin-3 and CA-125 may help to better discriminate pancreatic adenocarcinoma versus non-malignant pancreatic diseases. METHODS: We evaluated by immunohistochemistry the expression of MUC4, MUC16 (CA-125) and galectin-3 in 31 pancreatic adenocarcinomas. We measured CA 19-9, CA-125 and Gal-3 in the serum from patients with pancreatic benign diseases (n = 58) or adenocarcinoma (n = 44). Clinical performance of the 3 biomarkers for cancer diagnosis and prognosis was analyzed. RESULTS: By immunohistochemistry, MUC16 and Gal-3 were expressed in 74% and 84% of adenocarcinomas versus 0% and 3.2% in peri-tumoral regions, respectively. At the serum level, CA 19-9 and CA125 were significantly higher in patients with pancreatic adenocarcinoma whereas Gal-3 levels did not differ. The performance of CA 19-9 for cancer detection was higher than those of CA-125 or Gal-3 by ROC analysis. However, CA-125 offers the highest specificity for malignancy (81%) because of an absence of false positives among type 2 diabetic patients. Cancer deaths assessed 6 or 12 months after diagnosis varied according to the initial CA-125 level (p < 0.006). CONCLUSION: Gal-3 is not an interesting biomarker for pancreatic adenocarcinoma detection. CA 19-9 alone exhibits the best performance but measuring CA-125 provides complementary information in terms of diagnosis and prognosis.

Genetic predisposition to pheochromocytoma and paraganglioma: 21 years' experience in the field.

CONTEXT: Pheochromocytoma and paraganglioma (PPGL) are rare neuroendocrine tumors with high heritability, justifying systematic genetic screening for a germline variant in one of the twenty predisposing genes described to date. PURPOSE: To describe the experience of one endocrine oncogenetic laboratory over a period of 21 years (2001-2022), from the beginning of PPGL genotyping with Sanger sequencing in 2001 to the implementation of next-generation sequencing (NGS). METHOD: The activity database of an academic oncogenetic laboratory was searched to extract patients/relatives identified with a pathogenic variant/likely pathogenic variant (PV/LPV) over a period of 21 years. Clinical and genetic data were compared. RESULTS: In total, 606 index cases with PPGL and 444 relatives were genotyped. Genotyping of index cases was performed by Sanger sequencing and gene deletion analysis in 327 cases and by NGS in 279. Germline PV/LPV spanning 10 genes was identified in 165 index cases (27.2%). Several recurrent PV/LPVs in SDHx were observed in non-related index cases, the most frequent being SDHD, c.170-1G>T (n=28). This subgroup showed great phenotypic variability both between and within families in terms of both tumor location and number. Four patients (1.1%) with PV/LPV in SDHx had 3PA (Pituitary Adenoma and pheochromocytoma/paraganglioma) syndrome. 258 relatives (58.1%) had inherited a PV/LPV in one driver gene. The rate of PV/LPV carriers who were symptomatic at first imaging evaluation was 32%, but varied between<20% in SDHB and SDHC and >50% in SDHD, VHL and MAX. CONCLUSION: Our experience confirmed previously established genotype-phenotype correlations, but also highlights atypical clinical presentations, even for the same genetic variant. These data must be taken into account for optimal patient follow-up and management.

Beyond MEN1, When to Think About MEN4? Retrospective Study on 5600 Patients in the French Population and Literature Review.

CONTEXT: Germline CDKN1B variants predispose patients to multiple endocrine neoplasia type 4 (MEN4), a rare MEN1-like syndrome, with <100 reported cases since its discovery in 2006. Although CDKN1B mutations are frequently suggested to explain cases of genetically negative MEN1, the prevalence and phenotype of MEN4 patients is poorly known, and genetic counseling is unclear. OBJECTIVE: To evaluate the prevalence of MEN4 in MEN1-suspected patients and characterize the phenotype of MEN4 patients. DESIGN: Retrospective observational nationwide study. Narrative review of literature and variant class reassessment. PATIENTS: We included all adult patients with class 3/4/5 CDKN1B variants identified by the laboratories from the French Oncogenetic Network on Neuroendocrine Tumors network between 2015 and 2022 through germline genetic testing for MEN1 suspicion. After class reassessment, we compared the phenotype of symptomatic patients with class 4/5 CDKN1B variants (ie, with genetically confirmed MEN4 diagnosis) in our series and in literature with 66 matched MEN1 patients from the UMD-MEN1 database. RESULTS: From 5600 MEN1-suspected patients analyzed, 4 with class 4/5 CDKN1B variant were found (0.07%). They presented with multiple duodenal NET, primary hyperparathyroidism (PHPT) and adrenal nodule, isolated PHPT, PHPT, and pancreatic neuroendocrine tumor. We listed 29 patients with CDKN1B class 4/5 variants from the literature. Compared with matched MEN1 patients, MEN4 patients presented lower NET incidence and older age at PHPT diagnosis. CONCLUSION: The prevalence of MEN4 is low. PHPT and pituitary adenoma represent the main associated lesions, NETs are rare. Our results suggest a milder and later phenotype than in MEN1. Our observations will help to improve genetic counseling and management of MEN4 families.

Metabolism of pancreatic neuroendocrine tumors: what can omics tell us?

Introduction: Reprogramming of cellular metabolism is now a hallmark of tumorigenesis. In recent years, research on pancreatic neuroendocrine tumors (pNETs) has focused on genetic and epigenetic modifications and related signaling pathways, but few studies have been devoted to characterizing the metabolic profile of these tumors. In this review, we thoroughly investigate the metabolic pathways in pNETs by analyzing the transcriptomic and metabolomic data available in the literature. Methodology: We retrieved and downloaded gene expression profiles from all publicly available gene set enrichments (GSE43797, GSE73338, and GSE117851) to compare the differences in expressed genes based on both the stage and MEN1 mutational status. In addition, we conducted a systematic review of metabolomic data in NETs. Results: By combining transcriptomic and metabolomic approaches, we have identified a distinctive metabolism in pNETs compared with controls without pNETs. Our analysis showed dysregulations in the one-carbon, glutathione, and polyamine metabolisms, fatty acid biosynthesis, and branched-chain amino acid catabolism, which supply the tricarboxylic acid cycle. These targets are implicated in pNET cell proliferation and metastasis and could also have a prognostic impact. When analyzing the profiles of patients with or without metastasis, or with or without MEN1 mutation, we observed only a few differences due to the scarcity of published clinical data in the existing research. Consequently, further studies are now necessary to validate our data and investigate these potential targets as biomarkers or therapeutic solutions, with a specific focus on pNETs.

Serum Succinate/Fumarate Ratio in Patients With Paraganglioma/Pheochromocytoma Attending an Endocrine Oncogenetic Unit.

CONTEXT: Pheochromocytomas and paragangliomas (PPGLs) with SDHx pathogenic variants (PVs) are characterized by a higher intratissular succinate/fumarate ratio (RS/F) than non-SDHx-mutated ones. Also, an increase in serum succinate levels has been reported in patients with germline SDHB or SDHD PV. OBJECTIVE: To assess whether measurement of serum succinate, fumarate levels, and RS/F might aid identification of an SDHx germline PV/likely pathogenic variant (LPV) in patients with PPGL or in asymptomatic relatives; and to guide identification of a PV/LPV among the variants of unknown significance (VUS) identified in SDHx by next-generation sequencing. METHODS: This prospective monocentric study included 93 patients attending an endocrine oncogenetic unit for genetic testing. Succinate and fumarate were measured in serum by gas chromatography coupled to mass spectrometry. The RS/F was calculated to assess SDH enzymatic function. Diagnostic performance was assessed by receiver operating characteristic analysis. RESULTS: RS/F had a higher discriminant power than succinate alone to identify an SDHx PV/LPV in patients with PPGL. However, SDHD PVs/LPVs are frequently missed. Only RS/F differed between asymptomatic SDHB/SDHD PV/LPV carriers and SDHB/SDHD-linked patients with PPGL. Finally RS/F could be helpful to easily evaluate the functional impact of VUS in SDHx. CONCLUSION: Measurement of serum RS/F in patients with PPGL and in asymptomatic relatives is a valuable initial workup tool to detect those carrying a germline PV/LPV in SDHx. Its discriminative power is equal or superior to those of succinate measured alone. SDHD PVs/LPVs are less frequently identified by these biochemical tools. Use of RS/F for SDHx VUS reclassification needs to be evaluated further.

Systematic detection of mosaicism by using digital NGS reveals three new MEN1 mosaicisms.

Purpose: Mosaicism is a feature of several inherited tumor syndromes. Only a few cases of mosaicism have been described in multiple endocrine neoplasia type 1 (MEN1). Next-generation sequencing (NGS) offers new possibilities for detecting mosaicism. Here, we report the first study to systematically look for MEN1 mosaicism, using blood DNA, in MEN1-suspected patients but without MEN1 pathogenic variants (PV) in a heterozygous state. Methods: Digital targeted NGS, including unique molecular identifiers (UMIs), was performed in routine practice, and the analytic performance of this method was verified. Results: Among a cohort of 119 patients harboring from 2 to 5 MEN1 lesions, we identified 3 patients with MEN1 mosaic PVs. The allele frequencies ranged from 2.3 to 9.5%. The detection rate of MEN1 mosaicism in patients bearing at least 3 MEN1 lesions was 17% (3/18). No cases were detected in patients with two lesions. Conclusion: We report here three new cases with MEN1 mosaicism. This study examined the performance of UMI in the diagnosis of MEN1 mosaicism in routine practice, and our results underline that the frequency of mosaicism is probably underestimated in patients with suspected MEN1.

Multiple endocrine neoplasia type 1 caused by mosaic mutation: clinical follow-up and genetic counseling?

MEN1 is an autosomal dominant hereditary syndrome characterized by several endocrine tumors, in most cases affecting the parathyroid glands, pancreas, and anterior pituitary. It is the result of inactivating mutations in the tumor suppressor gene MEN1. More than 1300 different mutations have been identified in this gene. Mosaic MEN1 mutations have been previously described in only a few patients in the literature. In this paper, we provide a review of six cases of MEN1 mosaicism reported in the literature supplemented with six additional cases described by the French TENgen network of laboratories. This review highlights that (i) MEN1 mosaicism is not associated with a mild phenotype and results in the same natural history as heterozygous MEN1 mutation and (ii) that more systematic detection of MEN1 mosaic mutation enables improvements in both patient monitoring and genetic counseling.

Antagonistic Roles of the Tumor Suppressor miR-210-3p and Oncomucin MUC4 Forming a Negative Feedback Loop in Pancreatic Adenocarcinoma.

BACKGROUND: Pancreatic adenocarcinoma (PDAC) is a deadly cancer with an extremely poor prognosis. MUC4 membrane-bound mucin is neoexpressed in early pancreatic neoplastic lesions and is associated with PDAC progression and chemoresistance. In cancers, microRNAs (miRNAs, small noncoding RNAs) are crucial regulators of carcinogenesis, chemotherapy response and even metastatic processes. In this study, we aimed at identifying and characterizing miRNAs activated downstream of MUC4-associated signaling in pancreatic adenocarcinoma. MiRnome analysis comparing MUC4-KD versus Mock cancer cells showed that MUC4 inhibition impaired miR-210-3p expression. Therefore, we aimed to better understand the miR-210-3p biological roles. METHODS: miR-210-3p expression level was analyzed by RT-qPCR in PDAC-derived cell lines (PANC89 Mock and MUC4-KD, PANC-1 and MiaPACA-2), as well as in mice and patients tissues. The MUC4-miR-210-3p regulation was investigated using luciferase reporter construct and chromatin immunoprecipitation experiments. Stable cell lines expressing miR-210-3p or anti-miR-210-3p were established using CRISPR/Cas9 technology or lentiviral transduction. We evaluated the biological activity of miR-210-3p in vitro by measuring cell proliferation and migration and in vivo using a model of subcutaneous xenograft. RESULTS: miR-210-3p expression is correlated with MUC4 expression in PDAC-derived cells and human samples, and in pancreatic PanIN lesions of Pdx1-Cre; LstopL-KrasG12D mice. MUC4 enhances miR-210-3p expression levels via alteration of the NF-κB signaling pathway. Chromatin immunoprecipitation experiments showed p50 NF-κB subunit binding on miR-210-3p promoter regions. We established a reciprocal regulation since miR-210-3p repressed MUC4 expression via its 3'-UTR. MiR-210-3p transient transfection of PANC89, PANC-1 and MiaPACA-2 cells led to a decrease in cell proliferation and migration. These biological effects were validated in cells overexpressing or knocked-down for miR-210-3p. Finally, we showed that miR-210-3p inhibits pancreatic tumor growth and proliferation in vivo. CONCLUSION: We identified a MUC4-miR-210-3p negative feedback loop in early-onset PDAC, but also revealed new functions of miR-210-3p in both in vitro and in vivo proliferation and migration of pancreatic cancer cells, suggesting a complex balance between MUC4 pro-oncogenic roles and miR-210-3p anti-tumoral effects.

A large extended family with hyperparathyroidism-jaw tumor syndrome due to deletion of the third exon of CDC73: clinical and molecular features.

PURPOSE: We described the phenotype of a large 4-generation family with Hyperparathyrodism-Jaw Tumor syndrome (HPT-JT) associated with a rare deletion of exon 3 of the CDC73 gene. METHODS: We collected medical, genetic data on 24 family members descended from a common ancestor carrying a heterozygous deletion of exon 3. RESULTS: Thirteen carried the deletion, the penetrance was estimated at 50% at 40 years. Seven patients (39 ± 14.5 years) presented with HPT which could start at 13. Median plasmatic calcium and PTH levels were 3.13 ± 0.7 mmol/L and 115 ± 406 pg/ml, respectively. Kidney disease related to hypercalcemia were present in 57.1% of patients. All seven patients underwent surgery to remove a single parathyroid adenoma. One recurrence occurred 7 years post-surgery. No parathyroid carcinoma has been found to date. We found two atypical parathyroid adenomas. We described an additional somatic variant in exon 1 of gene CDC73 in two tumors. Jaw tumors were not necessarily associated with hyperparathyroidism, as shown in one case. Two kidney cysts were also reported. Variable phenotype expressivity was emphasized by clinical presentations in 2 monozygotic twins: acute hypercalcemia, kidney failure and ossifying fibroma in one twin, versus normocalcemic parathyroid adenoma in the other one. CONCLUSION: We report a family carrier of a deletion of exon 3 of the CDC73 gene. This is characterized by a high level of hypercalcemia, deleterious kidney effects and atypical parathyroid adenomas without carcinomas. Onset and intensity of HPT remain unpredictable. The additional somatic mutation found in the parathyroid tumor could lead to these phenotypical variations.

Unsupervised Hierarchical Clustering of Pancreatic Adenocarcinoma Dataset from TCGA Defines a Mucin Expression Profile that Impacts Overall Survival.

Mucins are commonly associated with pancreatic ductal adenocarcinoma (PDAC) that is a deadly disease because of the lack of early diagnosis and efficient therapies. There are 22 mucin genes encoding large O-glycoproteins divided into two major subgroups: membrane-bound and secreted mucins. We investigated mucin expression and their impact on patient survival in the PDAC dataset from The Cancer Genome Atlas (PAAD-TCGA). We observed a statistically significant increased messenger RNA (mRNA) relative level of most of the membrane-bound mucins (MUC1/3A/4/12/13/16/17/20), secreted mucins (MUC5AC/5B), and atypical mucins (MUC14/18) compared to normal pancreas. We show that MUC1/4/5B/14/17/20/21 mRNA levels are associated with poorer survival in the high-expression group compared to the low-expression group. Using unsupervised clustering analysis of mucin gene expression patterns, we identified two major clusters of patients. Cluster #1 harbors a higher expression of MUC15 and atypical MUC14/MUC18, whereas cluster #2 is characterized by a global overexpression of membrane-bound mucins (MUC1/4/16/17/20/21). Cluster #2 is associated with shorter overall survival. The patient stratification appears to be independent of usual clinical features (tumor stage, differentiation grade, lymph node invasion) suggesting that the pattern of membrane-bound mucin expression could be a new prognostic marker for PDAC patients.

Should the GCM2 gene be tested when screening for familial primary hyperparathyroidism?

OBJECTIVE: Primary hyperparathyroism (PHPT) is a disease with either sporadic or inherited presentation. Germline mutations responsible for this disease can be found in different genes, the most frequently involved being MEN1, CDC73 = HRPT2 and CASR. During the last few years, new genes have been described as responsible for the development of PHPT such as GCM2. These genes are not systematically included in PHPT genetic screening yet. The aim of this work was to assess the importance of GCM2 genetic analysis in PHPT to determine if this gene should be included in gene panel investigated for this disease. DESIGN AND METHODS: The TENGEN network (French Oncogenetic Network of Neuroendocrine Tumors) collected and interpreted allelic variants according to the clinical characteristics of the GCM2-positive patients identified through genetic testing performed in French laboratories (713 patients with PHPT). RESULTS: From 713 patients with PHPT included in this study, 85 (6.6%) carried at least one GCM2 variant. A total of 12 variants classified as uncertain significance or likely pathogenic were reported in 47 patients. Their mean age at PHPT diagnosis was 49 years. Additionally, the investigation of a large family showed that GCM2 variants could be associated with low penetrance. CONCLUSION: We provide a description and interpretation for GCM2 variants identified in a French population. We suggest that this gene should be included in genetic screening of patients with PHPT and propose the follow-up of asymptomatic patients carrying such variants for calcemia.

Galectin-3 modulates epithelial cell adaptation to stress at the ER-mitochondria interface.

Cellular stress response contributes to epithelial defense in adaptation to environment changes. Galectins play a pivotal role in the regulation of this response in malignant cells. However, precise underlying mechanisms are largely unknown. Here we demonstrate that Galectin-3, a pro and anti-apoptotic lectin, is required for setting up a correct cellular response to stress by orchestrating several effects. First, Galectin-3 constitutes a key post-transcriptional regulator of stress-related mRNA regulons coordinating the cell metabolism, the mTORC1 complex or the unfolded protein response (UPR). Moreover, we demonstrated the presence of Galectin-3 with mitochondria-associated membranes (MAM), and its interaction with proteins located at the ER or mitochondrial membranes. There Galectin-3 prevents the activation and recruitment at the mitochondria of the regulator of mitochondria fission DRP-1. Accordingly, loss of Galectin-3 impairs mitochondrial morphology, with more fragmented and round mitochondria, and dynamics both in normal and cancer epithelial cells in basal conditions. Importantly, Galectin-3 deficient cells also display changes of the activity of the mitochondrial respiratory chain complexes, of the mTORC1/S6RP/4EBP1 translation pathway and reactive oxygen species levels. Regarding the ER, Galectin-3 did not modify the activities of the 3 branches of the UPR in basal conditions. However, Galectin-3 favours an adaptative UPR following ER stress induction by Thapsigargin treatment. Altogether, at the ER-mitochondria interface, Galectin-3 coordinates the functioning of the ER and mitochondria, preserves the integrity of mitochondrial network and modulates the ER stress response.

UMD-MEN1 Database: An Overview of the 370 MEN1 Variants Present in 1676 Patients From the French Population.

Context: Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disease caused by mutations in the MEN1 gene characterized by a broad spectrum of clinical manifestations, of which the most frequent are primary hyperparathyroidism, pituitary adenomas, and neuroendocrine tumors. Objective: The aim of this work was to facilitate interpretation of variants and improve the genetic counseling and medical care of families of patients with MEN1. Design, Setting, and Patients: The TENGEN network (Oncogenetics Network of Neuroendocrine Tumors) has interpreted and collected all allelic variants and clinical characteristics of the MEN1-positive patients identified through genetic testing performed in the French population from 1997 to 2015. Patients and their variants were registered in the locus-specific UMD-MEN1 database (www.umd.be/MEN1/). Main Outcomes: Variant classification, age-related penetrance, and odds ratios. Results: A total of 370 distinct variants reported in 1676 patients, including 181 unpublished variants, have been registered. This database analysis revealed a low frequency (6.6%) of benign or likely benign missense variants in MEN1. Eight families (1.9%) had members with familial isolated hyperparathyroidism and harbored the same mutations as that found in families with authentic MEN1. An association existed between large rearrangements and an earlier onset of the disease, whereas no difference was observed between truncating and nontruncating variants. Conclusion: The UMD-MEN1 database provides an exhaustive overview of the MEN1 variants present in the French population. For each variant, a classification is publicly available. Clinical data collections allow the determination of genotype-phenotype correlation and age-related penetrance of lesions in the cohort.

Optimization of Next-Generation Sequencing Technologies for von Hippel Lindau (VHL) Mosaic Mutation Detection and Development of Confirmation Methods.

Von Hippel-Lindau disease (VHL) is a monogenic disorder characterized by the development of tumors affecting the central nervous system, kidney, pancreas, or adrenal glands, and due to germline mutations in the VHL tumor suppressor gene. About 5% of patients with a typical VHL phenotype have no mutation detected by conventional techniques, so a postzygotic VHL mosaicism can be suspected. The aim of this study was therefore to implement a next-generation sequencing (NGS) strategy for VHL mosaic mutation detection, including an optimization of the original Personal Genome Machine design by enrichment with oligonucleotides corresponding to amplicons with insufficient depth of coverage. Two complementary strategies were developed for the confirmation of mosaic mutations identified by NGS, SNaPshot for variants present at an allelic ratio greater than 5%, and droplet digital PCR for allelic ratio above 1%. VHL mutant plasmids were generated to assess VHL mosaic mutation detection in different exons and to set up an internal quality control that could be included in each run or regularly to validate the assay. This strategy was applied to 47 patients with a suggestive or clinical VHL disease, and mosaic mutations were identified in 8.5% of patients. In conclusion, NGS technologies combined with SNaPshot or droplet digital PCR allow the detection and confirmation of mosaic mutations in a clinical laboratory setting.

TGF-ßRII Knock-down in Pancreatic Cancer Cells Promotes Tumor Growth and Gemcitabine Resistance. Importance of STAT3 Phosphorylation on S727.

Pancreatic adenocarcinoma (PDAC) is one of the most deadly cancers in the Western world because of a lack of early diagnostic markers and efficient therapeutics. At the time of diagnosis, more than 80% of patients have metastasis or locally advanced cancer and are therefore not eligible for surgical resection. Pancreatic cancer cells also harbour a high resistance to chemotherapeutic drugs such as gemcitabine that is one of the main palliative treatments for PDAC. Proteins involved in TGF-ß signaling pathway (SMAD4 or TGF-ßRII) are frequently mutated in PDAC (50⁻80%). TGF-ß signalling pathway plays antagonistic roles during carcinogenesis by initially inhibiting epithelial growth and later promoting the progression of advanced tumors and thus emerged as both tumor suppressor and oncogenic pathways. In order to decipher the role of TGF-ß in pancreatic carcinogenesis and chemoresistance, we generated CAPAN-1 and CAPAN-2 cell lines knocked down for TGF-ßRII (first actor of TGF-ß signaling). The impact on biological properties of these TGF-ßRII-KD cells was studied both in vitro and in vivo. We show that TGF-ßRII silencing alters tumor growth and migration as well as resistance to gemcitabine. TGF-ßRII silencing also leads to S727 STAT3 and S63 c-Jun phosphorylation, decrease of MRP3 and increase of MRP4 ABC transporter expression and induction of a partial EMT phenotype. These markers associated with TGF-ß signaling pathways may thus appear as potent therapeutic tools to better treat/manage pancreatic cancer.

Galectin-3 is a non-classic RNA binding protein that stabilizes the mucin MUC4 mRNA in the cytoplasm of cancer cells.

Pancreatic cancer cells express high levels of MUC1, MUC4 and MUC16 mRNAs that encode membrane-bound mucins. These mRNAs share unusual features such as a long half-life. However, it remains unknown how mucin mRNA stability is regulated. Galectin-3 (Gal-3) is an endogenous lectin playing important biological functions in epithelial cells. Gal-3 is encoded by LGALS3 which is up-regulated in pancreatic cancer. Despite the absence of a RNA-recognition motif, Gal-3 interacts indirectly with pre-mRNAs in the nucleus and promotes constitutive splicing. However a broader role of Gal-3 in mRNA fate is unexplored. We report herein that Gal-3 increases MUC4 mRNA stability through an intermediate, hnRNP-L which binds to a conserved CA repeat element in the 3'UTR in a Gal-3 dependent manner and also controls Muc4 mRNA levels in epithelial tissues of Gal3-/- mice. Gal-3 interacts with hnRNP-L in the cytoplasm, especially during cell mitosis, but only partly associates with protein markers of P-Bodies or Stress Granules. By RNA-IP plus RNA-seq analysis and imaging, we demonstrate that Gal-3 binds to mature spliced MUC4 mRNA in the perinuclear region, probably in hnRNP-L-containing RNA granules. Our findings highlight a new role for Gal-3 as a non-classic RNA-binding protein that regulates MUC4 mRNA post-transcriptionally.