Identification of chromosome aberrations in sporadic microsatellite stable and unstable colorectal cancers using array comparative genomic hybridization

Colorectal cancer (CRC) is one of the most common cancers in Denmark and in the western world in general, and the prognosis is generally poor. According to the traditional molecular classification of sporadic colorectal cancer, microsatellite stable (MSS)/chromosome unstable (CIN) colorectal cancers constitute approximately 85% of sporadic cases, whereas microsatellite unstable (MSI) cases constitute the remaining 15%. In this study, we used array comparative genomic hybridization (aCGH) to identify genomic hotspot regions that harbor recurrent copy number changes. The study material comprised fresh samples from 40 MSS tumors and 20 MSI tumors obtained from 60 Danish CRC patients. We identified five small genomic regions (<15 megabases) exhibiting recurrent copy number loss, which, to our knowledge, have not been reported in previously published aCGH studies of CRC: 3p25.3, 3p21.2-p21.31, 5q13.2, 12q24.23-q24.31, and 12q24.23-q24.31. These regions contain several potentially important tumor suppressor genes that may play a role in a significant proportion of both sporadic MSS CRC and MSI CRC. Furthermore, the generated aCGH data are in support of the recently proposed classification of sporadic CRC into MSS CIN+, MSI CIN-, MSI CIN+, and MSS CIN- cancers.