Functional roles of pseudogenes in cancers.

Pseudogene is a DNA fragment with high sequence similarity to the corresponding functional gene. Because of accumulation of multiple mutations, pseudogenes have lost their original functions. Previous studies indicated that pseudogenes are dysfunctional relatives of the corresponding functional genes, and are noises in the process of genome evolution. However, with the development of molecular biotechnologies, more and more studies have demonstrated that pseudogenes possess important biologic functions. For example, some pseudogene could regulate the expression of functional genes by competitively binding to the miRNAs, some could produce endogenous small interference RNAs to negatively regulate the expression of functional genes, and some even could encode functional proteins. In this review, we summarize the recent research progresses of pseudogenes through four aspects: the classification, identification, function, and particularly the roles in cancers.