PURPOSE: Constitutional mismatch repair deficiency (CMMRD) is a highly penetrant cancer predisposition syndrome caused by biallelic mutations in mismatch repair (MMR) genes. As several cancer syndromes are clinically similar, accurate diagnosis is critical to cancer screening and treatment. As genetic diagnosis is confounded by 15 or more pseudogenes and variants of uncertain significance, a robust diagnostic assay is urgently needed. We sought to determine whether an assay that directly measures MMR activity could accurately diagnose CMMRD. PATIENTS AND METHODS: In vitro MMR activity was quantified using a 3'-nicked G-T mismatched DNA substrate, which requires MSH2-MSH6 and MLH1-PMS2 for repair. We quantified MMR activity from 20 Epstein-Barr virus-transformed lymphoblastoid cell lines from patients with confirmed CMMRD. We also tested 20 lymphoblastoid cell lines from patients who were suspected for CMMRD. We also characterized MMR activity from patients with neurofibromatosis type 1, Li-Fraumeni syndrome, polymerase proofreading-associated cancer syndrome, and Lynch syndrome. RESULTS: All CMMRD cell lines had low MMR activity (n = 20; mean, 4.14 ± 1.56%) relative to controls (n = 6; mean, 44.00 ± 8.65%; P < .001). Repair was restored by complementation with the missing protein, which confirmed MMR deficiency. All cases of patients with suspected CMMRD were accurately diagnosed. Individuals with Lynch syndrome (n = 28), neurofibromatosis type 1 (n = 5), Li-Fraumeni syndrome (n = 5), and polymerase proofreading-associated cancer syndrome (n = 3) had MMR activity that was comparable to controls. To accelerate testing, we measured MMR activity directly from fresh lymphocytes, which yielded results in 8 days. CONCLUSION: On the basis of the current data set, the in vitro G-T repair assay was able to diagnose CMMRD with 100% specificity and sensitivity. Rapid diagnosis before surgery in non-neoplastic tissues could speed proper therapeutic management.

• MeSH
• dědičné nádorové syndromy diagnóza   genetika   metabolismus   MeSH
• DNA vazebné proteiny genetika   metabolismus   MeSH
• enzymy opravy DNA genetika   metabolismus   MeSH
• fenotyp MeSH
• genetická predispozice k nemoci MeSH
• genetické testování * MeSH
• homolog 2 proteinu MutS genetika   metabolismus   MeSH
• kolorektální nádory diagnóza   genetika   metabolismus   MeSH
• lidé MeSH
• mismatch repair endonukleáza PMS2 genetika   metabolismus   MeSH
• mutace * MeSH
• MutL homolog 1 genetika   metabolismus   MeSH
• nádorové biomarkery genetika   metabolismus   MeSH
• nádorové buněčné linie MeSH
• nádory mozku diagnóza   genetika   metabolismus   MeSH
• oprava chybného párování bází DNA * MeSH
• prediktivní hodnota testů MeSH
• studie případů a kontrol MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• DNA vazebné proteiny MeSH
• enzymy opravy DNA MeSH
• G-T mismatch-binding protein MeSH Prohlížeč
• homolog 2 proteinu MutS MeSH
• mismatch repair endonukleáza PMS2 MeSH
• MLH1 protein, human MeSH Prohlížeč
• MSH2 protein, human MeSH Prohlížeč
• MutL homolog 1 MeSH
• nádorové biomarkery MeSH
• PMS2 protein, human MeSH Prohlížeč