Nuclear long non-coding RNAs as epigenetic regulators in cancer.

BACKGROUND Transcriptome analyses have revealed the presence of numerous long non-coding RNAs (lncRNAs) in mammalian cells. Many lncRNAs are expressed in development-, differentiation-, and disease-specific manners, suggesting their importance as cell regulators. Some nuclear lncRNAs are bound to specific genomic loci, either near or distant from their own transcription sites, and regulate gene expression in cis or trans. These lncRNAs recruit epigenetic factors, including the DNA methyl transferase and histone modification complex, and mediate both the 3D genome structure and nuclear domains. LncRNAs are now considered as an emerging member of epigenetic regulators. LncRNAs are dysregulated in various types of cancer, and act as either oncogenic or tumor-suppressing factors. They are involved in virtually all of the cancer hallmarks, and are potential diagnostic markers and therapeutic targets. OBJECTIVE In this review, we describe several representative lncRNAs and provide a current overview of the mechanisms by which lncRNAs participate in epigenetic regulation and contribute to cancer development.