MicroRNAs as biomarkers for the diagnosis and prognosis of human cancer

miRNAs are small-noncoding RNA molecules that regulate gene expression on a posttranscriptional level. A number of oncogenes and tumor suppressors were found to be targets of miRNAs and global miRNA expression signatures were able to distinguish between cancerous and non-cancerous tissues. Therefore it was not surprising that some miRNAs could be linked to the pathogenesis of cancer. In this review we provide an overview of the use of microRNAs as diagnostic and prognostic tools in cancer and focus on the use of miRNA expression as biomarker for disease activity.