[MicroRNAs and cancer-associated signal transduction pathways]

Signal transduction pathways play extremely important roles in various processes of cell life including metabolism, growth, proliferation, stress, development and apoptosis. Disruption of these pathways may affect normal cell growth and development, and even gives rise to tumors. MicroRNAs (miRNAs) are a newly discovered class of non-coding small RNAs (approximately 22 nucleotides in length) in eukaryotes that negatively regulate gene expression at the post-transcriptional level. With a wide range of target genes, they play essential and pervasive roles in diverse biological processes. Aberrant miRNA expression has recently been discovered in tumor development, indicating that miRNAs may be connected with tumorigenesis, possibly through regulating the expression of oncogenes and tumor-suppressing genes. It has also been noticed that many target genes of miRNA can influence tumor associated signal transduction pathways. The significant roles of miRNAs in tumorigenesis indicate that they may become a powerful tool for diagnosis and treatment of human cancers in the future.