Next Generation Sequencing Reveals Novel Mutations in Mismatch Repair Genes and Other Cancer Predisposition Genes in Asian Patients with Suspected Lynch Syndrome.

BACKGROUND

Although at least 5 genes are implicated in Lynch Syndrome (LS), up to 50% of suspected cases are owing to undefined genes. We utilized next generation sequencing (NGS) to characterize the mutation profile of patients with cancer (CA) suspected to have LS.

PATIENTS AND METHODS

We enrolled 174 Asian patients with CA from our CA Genetics Clinic from 2000 to 2014 suspected to have LS, and obtained germline DNA for NGS using TruSight Cancer. Frameshift, nonsense, and known deleterious mutations were considered pathogenic. Polymorphisms ≤ 1% frequency in 1000 Genomes (Asian) were classified using established databases.

RESULTS

Of the 174 probands, 80.5% were Chinese, the median age at CA diagnosis was 45 years (range, 18-82 years), and 84.5% and 8.6% had colon and LS-like CA, respectively. Forty-seven of 100 evaluable colon CA probands had LS-like histopathologic features. Nineteen of 174 had family history fulfilling Amsterdam I/II Criteria, whereas the rest fulfilled Bethesda Guidelines. Thirty-one of 174 harbored pathogenic mutations with 10 in LS genes only, 20 in non-LS genes only, and 1 in both. Of the 11 with LS gene mutations, MLH1 was most commonly involved (n = 7), followed by MSH2, MSH6, and PMS2. Nine of 174 had pathogenic mutations diagnostic of alternative hereditary syndromes including 2 each in CDH1, APC, and BRCA1, and 1 each in BRCA2, SMAD4, and MUTYH. Ten unique mutations were detected in low-to-moderate penetrance genes: 6 individuals had a recurring novel KIT:c.2836C>T nonsense mutation (n = 3) or ERCC4:c.2169C>A nonsense mutation (n = 3) without LS gene mutation, which is of clinical interest.

CONCLUSIONS

In this Asian study, NGS proved to be feasible in screening for causative mutations in patients with CA suspected to have LS.