Role of long non-coding ribonucleic acid in gastrointestinal cancer

With the improvement of high-throughput genomic technology such as microarray and next-generation sequencing over the last ten to twenty year, we have come to know that the portion of the genome responsible for protein coding constitutes just approximately 1.5%. The remaining 98.5% of the genome not responsible for protein coding have been regarded as 'junk DNA'. More recently, however, 'Encyclopedia of DNA elements project' revealed that most of the junk DNA were transcribed to RNA regardless of being translated into proteins. In addition, many reports support that a lot of these non-coding RNAs play a role in gene regulation. In fact, there are various functioning short non-coding RNAs including rRNA, tRNA, small interfering RNA, and micro RNA. Mechanisms of these RNAs are relatively well-known. Until recently, however, little is known about long non-coding RNAs which consist of 200 nucleotides or more. In this article, we will review the representative long non-coding RNAs which have been reported to be related to gastrointestinal cancers and to play a certain role in its pathogenesis.