Microsatellite stable colorectal cancers stratified by the BRAF V600E mutation show distinct patterns of chromosomal instability

The BRAF (V600E) mutation in colorectal cancers that are microsatellite stable (MSS) confers a poor patient prognosis, whereas BRAF mutant microsatellite-unstable (MSI) colorectal cancers have an excellent prognosis. BRAF wild type cancers are typically MSS and display chromosomal instability (CIN). CIN has not been extensively studied on a genome-wide basis in relation to BRAF mutational status in colorectal cancer. BRAF mutant/MSS ( BRAFmut/MSS) cancers (n = 33) and BRAF mutant/MSI (BRAFmut/MSI) cancers (n = 30) were compared for presence of copy number aberrations (CNAs) indicative of CIN, with BRAF wild type/MSS (BRAFwt/MSS) cancers (n = 18) using Illumina CytoSNP-12 arrays. BRAFmut/MSS and BRAFwt/ MSS cancers showed comparable numbers of CNAs/cancer at 32.8 and 29.8 respectively. However, there were differences in patterns of CNA length between MSS cohorts, with BRAFmut/MSS cancers having significantly greater proportions of focal CNAs compared to BRAFwt/MSS cancers (