Functional repair assay for the diagnosis of constitutional mismatch repair deficiency from non-neoplastic tissue

Andrew Y. Shuen, Stella Lanni, Gagan B. Panigrahi, Melissa Edwards, Lisa Yu, Brittany B. Campbell, Ariane Mandel, Cindy Zhang, Nataliya Zhukova, Musa Alharbi, Mark Bernstein, Daniel C. Bowers, Sara Carroll, Kristina A. Cole, Shlomi Constantini, Bruce Crooks, Rina Dvir, Roula Farah, Nobuko Hijiya, Ben GeorgeTheodore W. Laetsch, Valerie Larouche, Scott Lindhorst, Rebecca C. Luiten, Vanan Magimairajan, Gary Mason, Warren Mason, Oz Mordechai, Naureen Mushtaq, Garth Nicholas, Michael Oren, Laura Palma, Luis Alberto Pedroza, Jagadeesh Ramdas, David Samuel, Kami Wolfe Schneider, Andrea Seeley, Kara Semotiuk, Ashraf Shamvil, David Sumerauer, Helen Toledano, Patrick Tomboc, Margaret Wierman, An Van Damme, Yi Yen Lee, Michal Zapotocky, Eric Bouffet, Carol Durno, Melyssa Aronson, Steve Gallinger, William D. Foulkes, David Malkin, Uri Tabori, Christopher E. Pearson

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)


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 39-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 6 1.56%) relative to controls (n = 6; mean, 44.00 6 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.

Original languageEnglish
Pages (from-to)461-470
Number of pages10
JournalJournal of Clinical Oncology
Issue number6
Publication statusPublished - 2019


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