Gene expression comparison of colorectal cancer samples from patients diagnosed at a young and elderly age

Colorectal cancer (CRC) incidence increases with age and early onset of the disease is an indication of genetic predisposition, estimated to cause up to 30 % of all CRC cases. To identify genes associated with an increased risk for CRC, genome-wide gene expression levels of CRCs from patients diagnosed at an early age and CRCs from patients diagnosed at higher age were investigated. Patients with known hereditary predisposition syndromes were excluded from the study. Twenty four patients were diagnosed at a young age (mean, 43 years; range, 28-53 years), referred to as the early onset group. They were excluded from the HNPCC and FAP syndromes by clinical criteria and no other cancer syndromes were recorded for these patients. The second group consisted of 17 patients with primary diagnosis at old age (mean, 79 years; range, 69-87 years), referred to as the late onset group. The samples from the late onset group were selected to reflect the composition of the early onset group with respect to gender, tumor localization and tumor stage according to The International Union Against Cancer (UICC)/American Joint Committee on Cancer (AJCC). Microsatellite instability (MSI) status was previously analyzed in all samples to eliminate the potential risk of including patients with inherited DNA repair deficiencies.