MicroRNA expression profiling: A molecular tool for defining the phenotype of hepatocellular tumors

Two recent conceptual advances have led to an exciting renaissance in genetic regulation of biological processes involved in cell growth, development, and function. The first was the recognition that many portions of the human genome that do not encode conventional protein‐coding genes can encode biologically active RNA species. The second was the identification of mechanisms by which small RNA molecules could regulate gene and protein expression. Consequently, there has been an increasing recognition of the role of genetically encoded regulatory RNA molecules in biological processes. These advances have resulted in several new hypotheses on the mechanistic role of noncoding RNA in physiological processes, and their deregulation in disease. In turn, these hypotheses are beginning to provide new insights into disease classifications and pathogenesis.