Clinical significance of long noncoding RNAs in breast cancer patients

Breast cancer is one of the commonly diagnosed cancers in women globally. The long noncoding RNAs (lncRNAs) belong to the category of noncoding RNAs. The lncRNAs are equal to or more than 200 nucleotides in length. Accumulating evidence over the last 5 years has indicated that lncRNAs regulate crucial steps of tumorigenesis in multiple cancer types. Because of high dysregulation, specificity, and sensitivity in the detection, lncRNAs possess the potential of diagnostic and prognostic marker for breast cancer. The commonly identified lncRNAs in breast cancer include antisense ncRNA in the INK4 locus, breast cancer antiestrogen resistance 4, differentiation antagonizing nonprotein-coding RNA, H19-imprinted maternally expressed transcript, hypoxia-inducible factor 1A-antisense RNA 2, HOX transcript antisense RNA, metastasis-associated lung adenocarcinoma transcript 1, miR-503 host gene, terminal differentiation-induced ncRNA, TROJAN, and urothelial cancer-associated 1. The most common techniques used for elucidating the functions of lncRNAs in breast cancer patients include reverse transcription-quantitative polymerase chain reaction, next-generation sequencing, RNA-sequencing, microarray, TILING array, serial analysis of gene expression, cap analysis gene expression, and computational methods. The clinical specimens used to detect lncRNAs in patients include serum, plasma, tissues, urine, and saliva. The lncRNAs are reported to modulate multiple cell signaling pathways in breast cancer patients. The dysregulation in lncRNA expression is also one of the mechanisms by which breast cancer cells develop resistance to therapeutic agents. Thus breast cancer cells could also be sensitized to the therapeutic agents by targeting lncRNAs. The common strategies for targeting lncRNAs include the use of small molecules, antisense oligonucleotides, and RNA interference (RNAi) technology. The focus of this chapter is to review the potential of lncRNAs in breast cancer patients.