Long Non‐Coding RNAs and Their Roles in Cancer

The complex universe of RNA transcribed by mammalian cells includes many thousands of large RNA molecules that do not encode for proteins. However, only a few dozen of these long non-coding RNAs (lncRNAs) have been characterized. They therefore represent the largest and least explored class of RNA molecules. Despite this, emerging evidence points toward regulatory roles for lncRNAs in tumor suppressor and oncogenic pathways by different mechanisms are still not fully understood. lncRNAs have been shown to regulate gene expression at multiple genomic locations, associating with chromatin complexes and interfacing with epigenetic machinery. Additionally, some lncRNAs act in cis, enhancing the transcription of neighbor genes, while others function at the posttranscriptional level, suggesting that large non-coding RNAs act through multiple mechanisms, providing an additional layer of cellular regulation. The improved annotation of the human genome combined with high-throughput sequencing technology is being applied to identify alterations to the sequences and expression levels of ncRNAs associated with different types of tumor. The identification of lncRNAs altered in cancer is the first step toward the understanding of their function in the disease. Predictably, in the next years, our knowledge of the roles of lncRNAs in cancer will increase exponentially and will open up the possibility to their use as prognostic markers and even targets for therapy.