AUTHOR=Döring Claudia , Peer Katharina , Bankov Katrin , Bollmann Carmen , Ramaswamy Annette , Di Fazio Pietro , Wild Peter Johannes , Bartsch Detlef Klaus 

TITLE=Whole-exome sequencing of calcitonin-producing pancreatic neuroendocrine neoplasms indicates a unique molecular signature

JOURNAL=Frontiers in Oncology

VOLUME=13

YEAR=2023

URL=https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2023.1160921

DOI=10.3389/fonc.2023.1160921

ISSN=2234-943X

ABSTRACT=<sec><title>Introduction</title><p>Calcitonin-producing pancreatic neuroendocrine neoplasms (CT-pNENs) are an extremely rare clinical entity, with approximately 60 cases reported worldwide. While CT-pNENs can mimic the clinical and diagnostic features of medullary thyroid carcinoma, their molecular profile is poorly understood.</p></sec><sec><title>Methods</title><p>Whole-exome sequencing (WES) was performed on tumor and corresponding serum samples of five patients with increased calcitonin serum levels and histologically validated calcitonin-positive CT-pNENs. cBioPortal analysis and DAVID gene enrichment analysis were performed to identify dysregulated candidate genes compared to control databases. Immunohistochemistry was used to detect the protein expression of <italic>MUC4</italic> and <italic>MUC16</italic> in CT-pNEN specimens.</p></sec><sec><title>Results</title><p>Mutated genes known in the literature in pNENs like <italic>MEN1</italic> (35% of cases), <italic>ATRX</italic> (18-20% of cases) and <italic>PIK3CA</italic> (1.4% of cases) were identified in cases of CT-pNENs. New somatic SNVs in <italic>ATP4A, HES4</italic>, and <italic>CAV3</italic> have not been described in CT- pNENs, yet. Pathogenic germline mutations in <italic>FGFR4</italic> and <italic>DPYD</italic> were found in three of five cases. Mutations of <italic>CALCA</italic> (calcitonin) and the corresponding receptor <italic>CALCAR</italic> were found in all five tumor samples, but none of them resulted in protein sequelae or clinical relevance. All five tumor cases showed single nucleotide variations (SNVs) in <italic>MUC4</italic>, and four cases showed SNVs in <italic>MUC16</italic>, both of which were membrane-bound mucins. Immunohistochemistry showed protein expression of <italic>MUC4</italic> in two cases and <italic>MUC16</italic> in one case, and the liver metastasis of a third case was double positive for <italic>MUC4</italic> and <italic>MUC16</italic>. The homologous recombination deficiency (HRD) score of all tumors was low.</p></sec><sec><title>Discussion</title><p>CT-pNENs have a unique molecular signature compared to other pNEN subtypes, specifically involving the <italic>FGFR4, DPYD, MUC4, MUC16</italic> and the <italic>KRT</italic> family genes. However, a major limitation of our study was the relative small number of only five cases. Therefore, our WES data should be interpreted with caution and the mutation landscape in CT-pNENs needs to be verified by a larger number of patients. Further research is needed to explain differences in pathogenesis compared with other pNENs. In particular, multi-omics data such as RNASeq, methylation and whole genome sequencing could be informative.</p></sec>