Frequency and application of the hot spot BRAF gene mutation (p.V600E) in the diagnostic strategy for Hereditary Nonpolyposis Colorectal Cancer

Background: BRAF somatic mutations were reported with high frequency in sporadic colorectal cancers (CRCs) with microsatellite instability (MSI). The hot spot c. 1799 T>A, p.V600E gene mutation is very rarely involved in the tumorigenesis of CRC linked to Hereditary Nonpolyposis Colorectal Cancer (HNPCC). These data suggested that the screening of mismatch repair (MMR) genes could be avoided in cases positive for p.V600E. The aim of our study was to analyze the frequency of this hotspot mutation in a group of 140 CRC patients and the applicability of BRAF 15 exon mutation screening in the diagnosis of HNPCC. Methods: Exon 15 of the BRAF gene was PCR amplified and subjected to single-strand conformation polymorphism (SSCP) analysis. Samples showing an altered mobility pattern were then subjected to direct sequencing. Associations between BRAF mutation and clinical, pathological or molecular features were evaluated using Fisherʹs exact chi-squared tests as appropriate. Results: The mutation was detected in eight of 140 (5.7%) CRC samples with common characteristic features such as MSI, proximal tumor location, moderate differentiation, mucinous production and early Dukes’ stage. Conclusions: We conclude that screening for this mutation is an efficient tool in the diagnostic strategy for HNPCC.