PO-325 Novel recurrent high-level amplifications in microsatellite stable colorectal cancer

Introduction Colorectal cancer (CRC) is a molecularly diverse disease with few targeted treatment options. Focal and high-amplitude DNA copy number aberrations are potential tumour drivers, and their identification may contribute to improved therapeutic outcomes in small patient subgroups, as recently illustrated by targeting the over-expression of HER2 protein resulting from high-level ERBB2 amplification in KRAS wild-type metastatic CRC. However, few recurrent amplifications have been detected in CRC. Material and methods We analysed focal high-level amplifications in 203 microsatellite stable (MSS) primary colorectal tumours using genome-wide high-resolution Affymetrix SNP6.0 arrays. The ASCAT algorithm was used to derive discrete allele specific copy number estimates. Results and discussions The overall copy number profiles confirmed the frequent gains and losses previously described in MSS CRC studies. Extreme focal amplifications (defined as >15 copies and ERBB2 , which was amplified to 97, 27 and 22 additional copies in tumours from three individual patients (amplification frequency 1.5%). The transcription factor TOX3 (16q) was also recurrently amplified in 1.5% of the patients, while MYC (8q), CCND2 (12 p) and a region on 10q22.3-q23.1, where ANXA11 was nominated as a likely target by GISTIC analysis, were recurrent in 1% of the patients. Regions with extreme and focal amplifications were also investigated for lower-amplitude aberrations (5–15 additional DNA copies), revealing a 3% amplification frequency of TOX3 in our cohort. Conclusion We have identified several recurrent amplifications in cancer-critical genes in CRC MSS tumours, including the transcription factor TOX3 , suggesting novel drug targets for preclinical studies.