Circulating MicroRNAs as Tumor Biomarkers in Hepatocellular Carcinoma

Abstract MicroRNAs (miRNAs) are a group of small noncoding RNAs that post-transcriptionally regulate gene expression by targeting their corresponding messenger RNAs. Tumors such as hepatocellular carcinoma (HCC) contain a dysregulated miRNA pattern, which contributes to virtually to all aspects of cancer biology. The detection of extracellularly circulating stable miRNAs in the blood, the pattern of which shows alterations in liver diseases, stimulated the hunt for HCC-specific miRNAs from this convenient source of patient-derived material. This resulted in an increasing number of potential miRNA biomarkers for diagnosis, patient stratification, prognosis, and response to therapy. Although a number of studies indicate that extracellular miRNAs can provide information that clearly exceeds that obtained with other laboratory parameters, the transition of extracellular miRNAs into clinical biomarkers still turned out to be challenging. This chapter discusses the potential of extracellularly circulating miRNAs as biomarkers for different aspects in HCC.