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J Clin Oncol. 2019 Feb 20;37(6):461-470. doi: 10.1200/JCO.18.00474. Epub 2019 Jan 4.

Functional Repair Assay for the Diagnosis of Constitutional Mismatch Repair Deficiency From Non-Neoplastic Tissue.

Author information

1
1 University of Toronto, Toronto, Ontario, Canada.
2
2 The Hospital for Sick Children, Toronto, Ontario, Canada.
3
3 King Fahad Medical City, Riyadh, Saudi Arabia.
4
4 Dalhousie University Faculty of Medicine, Halifax, Nova Scotia, Canada.
5
5 University of Texas Southwestern Medical Center, Dallas, TX.
6
6 Children's Health, Dallas, TX.
7
7 Cleveland Clinic, Weston FL.
8
8 Children's Hospital of Philadelphia and University of Pennsylvania, Philadelphia, PA.
9
9 Tel Aviv Sourasky Medical Center, Tel Aviv, Israel.
10
10 Tel Aviv University, Tel Aviv, Israel.
11
11 Schneider Children's Medical Center of Israel, Petach Tikva, Israel.
12
12 Saint George Hospital University Medical Center, Beirut, Lebanon.
13
13 Ann & Robert H. Lurie Children's Hospital/Northwestern University Feinberg School of Medicine, Chicago, IL.
14
14 Medical College of Wisconsin, Milwaukee, WI.
15
15 Université Laval, Quebec City, Quebec, Canada.
16
16 Medical University of South Carolina, Charleston, SC.
17
17 Banner MD Anderson Cancer Center, Gilbert, AZ.
18
18 University of Manitoba, Winnipeg, Manitoba, Canada.
19
19 Children's Hospital of Pittsburgh of University of Pittsburgh Medical Center, Pittsburgh, PA.
20
20 Princess Margaret Cancer Centre, Toronto, Ontario, Canada.
21
21 Rambam Health Care Campus, Haifa, Israel.
22
22 Aga Khan University Hospital, Karachi, Pakistan.
23
23 Ottawa Hospital Research Institute, Ottawa, Ontario, Canada.
24
24 Sheba Medical Center, Tel Hashomer, Israel.
25
25 McGill University Health Centre, Montréal, Quebec, Canada.
26
26 Baylor College of Medicine and Texas Children's Hospital, Houston, TX.
27
27 Universidad San Francisco de Quito, Quito, Ecuador.
28
28 Geisinger Medical Center, Danville, PA.
29
29 Valley Children's Hospital, Madera, CA.
30
30 Children's Hospital Colorado, Aurora, CO.
31
31 University of Colorado, Anschutz Medical Campus, Aurora, CO.
32
32 Mount Sinai Hospital, Toronto, Ontario, Canada.
33
33 Children Cancer Hospital, Karachi, Pakistan.
34
34 University Hospital Motol, Charles University, Prague, Czech Republic.
35
35 Ruby Memorial Hospital, Morgantown, WV.
36
36 Université Catholique de Louvain, Brussels, Belgium.
37
37 Taipei Veterans General Hospital, Taipei, Republic of China.
38
38 Toronto General Hospital, Toronto, Ontario, Canada.
39
39 McGill University, Montréal, Quebec, Canada.

Abstract

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.

PMID:
30608896
DOI:
10.1200/JCO.18.00474

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