Mutation and Expression of DNA2 Gene in Gastric and Colorectal Carcinomas

Background : Deregulation of DNA repair and replication are involved in cancer development. DNA2 is a nuclease/helicase that plays roles in DNA repair and replication. The aim of this study was to explore DNA2 mutation and DNA2 protein expression in gastric cancers (GCs) and colorectal cancers (CRCs). Methods : We analyzed two mononucleotide repeats in DNA2 in 27 GCs with high microsatellite instability (MSI-H), 34 GCs with stable MSI (MSS), 29 CRCs with MSI-H and 35 CRCs with MSS by single-strand conformation polymorphism. We also analyzed DNA2 expression in GCs and CRCs either with MSI-H or MSS. Results : We found DNA2 mutations in two GCs (7.1%) and two CRCs with MSI-H (6.9%), but not in cancers with MSS. The mutations consisted of three cases of a c.2593delT and one of a c.2592_2593delTT, which would result in premature stopping of amino acid synthesis (p.Ser-865Hisfsx6 and p.Ser865Thrfsx20, respectively). DNA2 expression was observed in 16 (80%) of the GCs and 15 (75%) of the CRCs with MSI-H, but all of the cancers with DNA2 frameshift mutations were weak or negative for DNA2. Conclusions : Our data indicate that DNA2 mutation and loss of DNA2 expression occur in GCs and CRCs, and suggest that these alterations may contribute to cancer pathogenesis by deregulating DNA repair and replication.