Lynch Syndrome Improving Diagnostics and Surveillance

Lynch syndrome is the most common hereditary predisposition for colorectal cancer and accounts for 2-3% of all colorectal cancer cases. In addition, these patients are also at increased risk of developing extracolonic cancers, especially endometrial cancer in women. Since surveillance programs can significantly reduce morbidity and mortality in individuals with Lynch syndrome, identification of these individuals is of great importance. In chapter 3, two prediction models for Lynch syndrome were evaluated and one of those models, the PREMM5 model, was improved by adding the location of colorectal cancer as a new variable. In chapter 4 and 5 we showed that routine molecular screening for Lynch syndrome in colorectal cancer patients and endometrial cancer patients up to 70 years of age is cost-effective. In chapter 6, no Lynch syndrome patients were identified by screening for Lynch syndrome among all advanced adenomas in the population based CRC screening program. Therefore, routine screening of all adenomas is probably not effective. In chapter 7 and 8 a functional assay to classify variants of unknown significance in the mismatch repair genes was evaluated and 26 variants in MLH1, MSH2 and MSH6 were analyzed. In most cases the classification was in line with clinical data, prediction programs and results of other functional assays. Although the cancer risk in Lynch syndrome patients is highly dependent on the gene involved, all patients are currently offered the same surveillance. Therefore, chapter 9 evaluates the yield of colonoscopy surveillance in MLH1, MSH2, MSH6 and PMS2 mutation carriers. Finally, chapter 10 discusses the results of this thesis in perspective of the current guidelines and clinical practice

Suspected Lynch syndrome associated MSH6 variants: A functional assay to determine their pathogenicity

Lynch syndrome (LS) is a hereditary cancer predisposition caused by inactivating mutations in DNA mismatch repair (MMR) genes. Mutations in the MSH6 DNA MMR gene account for approximately 18% of LS cases. Many LS-associated sequence variants are nonsense and frameshift mutations that clearly abrogate MMR activity. However, missense mutations whose functional implications are unclear are also frequently seen in suspected-LS patients. To conclusively diagnose LS and enroll patients in appropriate surveillance programs to reduce morbidity as well as mortality, the functional consequences of these variants of uncertain clinical significance (VUS) must be defined. We present an oligonucleotide-directed mutagenesis screen for the identification of pathogenic MSH6 VUS. In the screen, the MSH6 variant of interest is introduced into mouse embryonic stem cells by site-directed mutagenesis. Subsequent selection for MMR-deficient cells using the DNA damaging agent 6-thioguanine (6TG) allows the identification of MMR abrogating VUS because solely MMR-deficient cells survive 6TG exposure. We demonstrate the efficacy of the genetic screen, investigate the phenotype of 26 MSH6 VUS and compare our screening results to clinical data from suspected-LS patients carrying these variant alleles

Evaluation of current prediction models for Lynch syndrome: updating the PREMM5 model to identify PMS2 mutation carriers

Until recently, no prediction models for Lynch syndrome (LS) had been validated for PMS2 mutation carriers. We aimed to evaluate MMRpredict and PREMM5 in a clinical cohort and for PMS2 mutation carriers specifically. In a retrospective, clinic-based cohort we calculated predictions for LS according to MMRpredict and PREMM5. The area under the operator receiving characteristic curve (AU

Gynecological surveillance and surgery outcomes in dutch lynch syndrome carriers

Female Lynch syndrome (LS) carriers have an increased risk to develop endometrial and ovarian cancer. In the Netherlands, carriers are therefore advised annual gynecological surveillance and eventually, risk-reducing surgery. Global gynecological LS surveillance guidelines are scarce and based on limited evidence. These are, however, warranted to offer accurate surveillance. To provide more insight into surveillance outcomes, this study assessed outcomes of gynecological surveillance and risk-reducing surgery in 164 LS carriers diagnosed in our center, with a median follow-up of 5.6 years per carrier. Although most surveillance visits happened within an advised timeframe, we observed large variability in how gynecological surveillance visits were performed. This finding stresses the need for development of clear and evidence-based guidelines. Endometrial cancers identified at surveillance were all found in early stage, mostly symptomatic, questioning surveillance benefit. Large, prospective studies should assess to what extent current LS surveillance programs contribute to early detection of gynecological tumors. Lynch syndrome (LS) is caused by pathogenic germline variants in DNA mismatch repair (MMR) genes, predisposing female carriers for endometrial cancer (EC) and ovarian cancer (OC). Since gynecological LS surveillance guidelines are based on little evidence, we assessed its outcomes. Data regarding gynecological tumors, surveillance, and (risk-reducing) surgery were collected from female LS carriers diagnosed in our center since 1993. Of 505 female carriers, 104 had a gynecological malignancy prior to genetic LS diagnosis. Of 264 carriers eligible for gynecological management, 164 carriers gave informed consent and had available surveillance data: 38 MLH1, 25 MSH2, 82 MSH6, and 19 PMS2 carriers (median follow-up 5.6 years). Surveillance intervals were within advised time in >80%. Transvaginal ultrasound, endometrial sampling, and CA125 measurements were performed in 76.8%, 35.9%, and 40.6%, respectively. Four symptomatic ECs, one symptomatic OC, and one asymptomatic EC were diagnosed. Endometrial hyperplasia was found in eight carriers, of whomthree were symptomatic. Risk-reducing surgery was performed in 73 (45.5%) carriers (median age 51 years), revealing two asymptomatic ECs. All ECs were diagnosed in FIGO I. Gynecological management in LS carriers varied largely, stressing the need for uniform, evidence-based guidelines. Most ECs presented early and symptomatically, questioning the surveillance benefit in its current form

Optimal Diagnostic and Treatment Practices for Facial Dysostosis Syndromes:A Clinical Consensus Statement Among European Experts

Facial dysostosis syndromes (FDS) are rare congenital conditions impacting facial development, often leading to diverse craniofacial abnormalities. This study addresses the scarcity of evidence on these syndromes about optimal diagnostic and treatment practices. To overcome this scarcity, European experts from ERN CRANIO collaborated to develop a clinical consensus statement through the Delphi consensus method. A systematic search of Embase, MEDLINE/PubMed, Cochrane, and Web of Science databases was conducted until February 2023. The quality of evidence was evaluated using various tools depending on the study design. Statements were subsequently formed based on literature and expert opinion, followed by a Delphi process with expert health care providers and patient representatives. In total, 92 experts from various specialties and three patient representatives were involved in the Delphi process. Over 3 voting rounds, consensus was achieved on 92 (46.9%), 58 (59.2%), and 19 (70.4%) statements, respectively. These statements cover the topics of general care; craniofacial reconstruction; the eyes and lacrimal system; upper airway management; genetics; hearing; speech; growth, feeding, and swallowing; dental treatment and orthodontics; extracranial anomalies; and psychology and cognition. The current clinical consensus statement provides valuable insights into optimal diagnostic and treatment practices and identifies key research opportunities for FDS. This consensus statement represents a significant advancement in FDS care, underlining the commitment of health care professionals to improve the understanding and management of these rare syndromes in Europe.</p

Deficient histone H3 propionylation by BRPF1-KAT6 complexes in neurodevelopmental disorders and cancer

Lysine acetyltransferase 6A (KAT6A) and its paralog KAT6B form stoichiometric complexes with bromodomain- and PHD finger-containing protein 1 (BRPF1) for acetylation of histone H3 at lysine 23 (H3K23). We report that these complexes also catalyze H3K23 propionylation in vitro and in vivo. Immunofluorescence microscopy and ATAC-See revealed the association of this modification with active chromatin. Brpf1 deletion obliterates the acylation in mouse embryos and fibroblasts. Moreover, we identify BRPF1 variants in 12 previously unidentified cases of syndromic intellectual disability and demonstrate that these cases and known BRPF1 variants impair H3K23 propionylation. Cardiac anomalies are present in a subset of the cases. H3K23 acylation is also impaired by cancer-derived somatic BRPF1 mutations. Valproate, vorinostat, propionate and butyrate promote H3K23 acylation. These results reveal the dual functionality of BRPF1-KAT6 complexes, shed light on mechanisms underlying related developmental disorders and various cancers, and suggest mutation-based therapy for medical conditions with deficient histone acylation

Deficient histone H3 propionylation by BRPF1-KAT6 complexes in neurodevelopmental disorders and cancer

Lysine acetyltransferase 6A (KAT6A) and its paralog KAT6B form stoichiometric complexes with bromodomain- and PHD finger-containing protein 1 (BRPF1) for acetylation of histone H3 at lysine 23 (H3K23). We report that these complexes also catalyze H3K23 propionylati