A founder MLH1 mutation in Lynch syndrome families from Piedmont, Italy, is associated with an increased risk of pancreatic tumours and diverse immunohistochemical patterns

Precursor lesions in familial and hereditary pancreatic cancer

Infiltrating ductal adenocarcinoma of the pancreas, referred to here as "pancreatic cancer," is one of the deadliest of all of the solid malignancies. The five-year survival rate in the United States for individuals diagnosed today with pancreatic cancer is a dismal 12%. Many invasive cancers, including pancreatic cancer, however, arise from histologically and genetically well-characterized precursor lesions, and these precancers are curable. Precursor lesions therefore are an attractive target for early detection and treatment. This is particularly true for individuals with an increased risk of developing invasive cancer, such as individuals with a strong family history of pancreatic cancer, and individuals with a germline variant known to increase the risk of developing pancreatic cancer. There is therefore a need to understand the precursor lesions that can give rise to invasive pancreatic cancer in these individuals.

Clinical characteristics of pancreatic and biliary tract cancers in Lynch syndrome: A retrospective analysis from the Finnish National Lynch Syndrome Research Registry

Introduction

Patients with Lynch syndrome (LS) have an increased lifetime risk of pancreatic cancer (PC) and biliary tract cancer (BTC). These cancers have a notoriously pessimistic prognosis due to late diagnosis and limited therapeutic options. There are limited data based on small cohorts reviewing PC and BTC in LS patients.

Methods

In this retrospective study of the Lynch Syndrome Registry of Finland (LSRFi), records of genetically verified LS patients diagnosed with PC or BTC between 1982 and 2020 were analyzed.

Results

Thirty-nine patients were included: tumor(s) were in the pancreas in 26 patients, in the biliary tract in 10, and in the ampulla of Vater in three. A pathogenic germline variant was found in MLH1 in 33 of 39 patients. Twenty-six patients with 28 tumors located in the pancreas were identified: 23 pancreatic ductal adenocarcinomas (PDACs) and five neuroendocrine tumors (NETs). The median age at diagnosis of PC was 64 years (range of 38-81). In PC, the 5-year overall survival (OS) rate was 20%, and in PDAC, it was 13.6%. Ten patients with BTC were diagnosed: two intrahepatic, five perihilar, two distal extrahepatic cholangiocarcinomas, and one gallbladder carcinoma. Eight patients were male, and the median age at diagnosis was 54 years (range of 34-82). The 5-year OS rate for BTC was 30%. Metachronous tumors were diagnosed in 28 patients (70%). Colorectal cancer was the most common metachronous tumor, diagnosed in 20 patients (51%), and diagnosed prior to PC or BTC in all cases. Curative surgery was attempted on 17 of 39 patients. For 30 patients (91%), the cause of death was PC or BTC; two patients died from another LS-associated cancer, and one died from a stroke.

Conclusion

Although the survival of LS patients with PC or BTC is better than in sporadic cancers, it is still poor and may be reflected by the relatively higher surgical resectability accounted for by the earlier age of onset. More studies on analyses of the molecular and immune profile, screening, and management of LS-associated pancreaticobiliary cancers are warranted.

The genetics of ductal adenocarcinoma of the pancreas in the year 2020: dramatic progress, but far to go

The publication of the "Pan-Cancer Atlas" by the Pan-Cancer Analysis of Whole Genomes Consortium, a partnership formed by The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC), provides a wonderful opportunity to reflect on where we stand in our understanding of the genetics of pancreatic cancer, as well as on the opportunities to translate this understanding to patient care. From germline variants that predispose to the development of pancreatic cancer, to somatic mutations that are therapeutically targetable, genetics is now providing hope, where there once was no hope, for those diagnosed with pancreatic cancer.

A Novel Germline MLH1 In-Frame Deletion in a Slovenian Lynch Syndrome Family Associated with Uncommon Isolated PMS2 Loss in Tumor Tissue

The diagnostics of Lynch syndrome (LS) is focused on the detection of DNA mismatch repair (MMR) system deficiency. MMR deficiency can be detected on tumor tissue by microsatellite instability (MSI) using molecular genetic test or by loss of expression of one of the four proteins (MLH1, MSH2, MSH6, and PMS2) involved in the MMR system using immunohistochemistry (IHC) staining. According to the National Comprehensive Cancer Network (NCCN) guidelines, definitive diagnosis of LS requires the identification of the germline pathogenic variant in one of the MMR genes. In the report, we are presenting interesting novel MLH1 in-frame deletion LRG_216t1:c.2236_2247delCTGCCTGATCTA p.(Leu746_Leu749del) associated with LS. The variant appears to be associated with uncommon isolated loss of PMS2 immunohistochemistry protein staining (expression) in tumor tissue instead of MLH1 and PMS2 protein loss, which is commonly seen with pathogenic variants in MLH1. The variant was classified as likely pathogenic, based on segregation analysis and molecular characterization of blood and tumor samples. According to the American College of Medical Genetics (ACMG) guidelines, the following evidence categories of PM1, PM2, PM4, and PP1 moderate have been used for classification of the novel variant. By detecting and classifying the novel MLH1 variant as likely pathogenic, we confirmed the LS in this family.

Pancreatic Cancer in Lynch Syndrome Patients

Although colorectal cancer (CRC) is the most common cancer type in Lynch syndrome (LS) families, patients have also increased lifetime risk of other types of tumors. The accumulated risk of pancreatic cancer (PC) in LS patients is around 3.7% and developed tumors often present a characteristically medullary appearance with prominent lymphocytic infiltration. LS patients are considered in high risk for PC development as they present 8.6-fold increase compared with the general population.

Here we review PC cases reported in LS patients and current management guidelines. Literature data show that LS is clearly associated with PC and recent publications also demonstrated a connection with pancreatic neoplasic precursor lesions such as intraductal papillary mucinous neoplasms (IPMN) in these patients.

While screening techniques are well established for CRC detection, clear strategies are not yet uniform for PC. Magnetic resonance imaging (MRI) and/or endoscopic ultrasound every 1-2 years in MMR mutation carriers with PC in a first or second-degree relative is recommended.

Better pancreatic cancer detection strategies should be urgently defined due to the importance of early diagnosis in this disease.

MIA PaCa-2 and PANC-1 - pancreas ductal adenocarcinoma cell lines with neuroendocrine differentiation and somatostatin receptors

Studies using cell lines should always characterize these cells to ensure that the results are not distorted by unexpected morphological or genetic changes possibly due to culture time or passage number. Thus, the aim of this study was to describe those MIA PaCa-2 and PANC-1 cell line phenotype and genotype characteristics that may play a crucial role in pancreatic cancer therapeutic assays, namely neuroendocrine chemotherapy and peptide receptor radionuclide therapy. Epithelial, mesenchymal, endocrine and stem cell marker characterization was performed by immunohistochemistry and flow cytometry, and genotyping by PCR, gene sequencing and capillary electrophoresis. MIA PaCa-2 (polymorphism) expresses CK5.6, AE1/AE3, E-cadherin, vimentin, chromogranin A, synaptophysin, SSTR2 and NTR1 but not CD56. PANC-1 (pleomorphism) expresses CK5.6, MNF-116, vimentin, chromogranin A, CD56 and SSTR2 but not E-cadherin, synaptophysin or NTR1. MIA PaCA-1 is CD24⁻, CD44^+/++, CD326^−/+ and CD133/1⁻, while PANC-1 is CD24^−/+, CD44⁺, CD326^−/+ and CD133/1⁻. Both cell lines have KRAS and TP53 mutations and homozygous deletions including the first 3 exons of CDKN2A/p16^INK4A, but no SMAD4/DPC4 mutations or microsatellite instability. Both have neuroendocrine differentiation and SSTR2 receptors, precisely the features making them suitable for the therapies we propose to assay in future studies.

Mismatch repair genes founder mutations and cancer susceptibility in Lynch syndrome

Founder mutations in specific populations are common in several Mendelian disorders. They are shared by apparently unrelated families that inherited them from a common ancestor that existed hundreds to thousands of years ago. They have been proven to impact in molecular diagnostics strategies in specific populations, where they can be assessed as the first screening step and, if positive, avoid further expensive gene scanning. In Lynch syndrome (LS), a dominantly inherited colorectal cancer disease, more than 50 founder pathogenic mutations have been described so far in the mismatch repair (MMR) genes (MLH1, MSH2, MSH6 and PMS2). We here provide a comprehensive summary of the founder mutations found in the MMR genes and an overview of their main characteristics. At a time when high-throughput strategies are being introduced in the molecular diagnostics of cancer, genetic testing for founder mutations can complement next generation sequencing (NGS) technologies to most efficiently identify MMR gene mutations in any given population. Additionally, special attention is paid to MMR founder mutations with interesting anthropological significance.