Genetic differences based on miRNAs of colorectal adenocarcinoma according to age and the presence or absence of MMR defect.
495 Background: More than 1.2 million new cases of colon adenocarcinoma (CRC) are diagnosed annually. Specific germline mutations are responsible for hereditary CRC syndromes, while somatic mutations is thought to underlie most sporadic cases. Recently, miRNAs have been described as important regulators of malignant transformation. We aim to study the expression of miRNAs in CRC patients with Lynch syndrome and in patients with CRC without microsatellite instability (MSI-S) who have developed cancer at different ages. Methods: We included 60 cases of CRC patients: 20 with CRC associated with Lynch syndrome in carriers of germline MMR mutation (group 1), 20 with CRC MSI-S diagnosed before 45 years (group 2) and 20 with MSI-S diagnosed after age 50 (group 3). From all these cases we selected 7: 3 from group 1, 2 from group 2, another 2 from group 3, and a control with healthy colonic mucosa. Screening was carried out for expression of miRNAs (850 miRNAs) and hybridization arrays (Exiqon) using paraffin colic tissue. A comparative analysis was made of the expression obtained in the different groups. Results: Hybridization arrays analysis indicates that there are 248 miRNAs differentially expressed between healthy controls and patients with CRC. In addition, there are 165 miRNAs differentially expressed between different groups of patients with CRC according to age at diagnosis (≤ 45 years vs.> 50 years). Moreover, the pattern of miRNAs in patients with germline mutation in Lynch syndrome is very different to that of patients diagnosed with CRC> 50 years. There are 117 miRNAs differentially expressed between these cases. Just a group of 20 miRNAs have different expression among patients with CRC MSI-S ≤ 45 years for CRC patients with Lynch syndrome mutation in MLH1. Conclusions: Differences exist in the profile of CRC mRNAs expression according to the age, as well as between CRC MSI-S patients > 50 years and CRC in Lynch syndrome. Different patterns of miRNAs in CRC indicate different molecular signature in different groups of CRC could became new CRC diagnostic markers and most importantly could point out new targets for therapeutic interventions in CRC.