Cluster mir-17–92 is differentially expressed in colon cancer patients and embryonic colon tissue and may contribute to carcinogenesis through E2F1 expression

Abstract

10525 Background: Mature microRNAs (miRNA) are small RNA molecules that act as negative regulators of gene expression, either inhibiting mRNA by blocking its translation into protein or destroying it by RNA interference. Many miRNAs participate in essential processes, including normal embryonic development and carcinogenesis. Methods: We have assessed 156 mature miRNAs in colon tissue from eleven 7–12-week human embryos and 44 colorectal human samples. Data were analyzed using TIGR Multiexperiment viewer. Two multivariate permutation test were performed. Potential target genes of differentially expressed miRNAs are evaluated by western blot. Results: 28 miRNAs were expressed in stage I tumor tissue but not in the corresponding normal tissue, and 13 of these 28 miRNAs (46%) were also expressed in embryonic tissue. Sixty-four miRNAs were differentially expressed in stage II tumor tissue, and 29 of these 64 miRNAs (45%) were also expressed in embryonic tissue. Some miRNAs that are active during embryogenesis, such as mir-17–92, miR-181a, miR-181b and miR-181c (linked to HOXA11), and miR-10a (linked to HOXB8)23, are also expressed during tumor growth. The analysis of 156 miRNAs by K-means support revealed two well-differentiated groups: the embryos of 7–8 weeks and those of 9–12 weeks. Lower miRNA expression was also observed in tumor tissue from stage I in comparison with stage II disease (P=0.014). Analysis of potential target genes revealed that cluster mir-17–92 is differentially expressed in colon cancer and embryonic tissue and may contribute to carcinogenesis through E2F1 expression. Conclusions: Our findings indicate that miRNAs expressed during the embryonic development of the human colon are also expressed in colon tumor tissue. During colon organogenesis, miRNA expression is at first high, while cells are still undifferentiated, but expression levels decrease as cells become more differentiated. In contrast, during the development of colorectal cancer, this process is reversed. No significant financial relationships to disclose.