Overview of long non-coding RNA and its role in breast cancer.

The mammary glands are made of different cell populations that have great cellular plasticity, which is mainly regulated by epigenetic changes that allow the expression of specific transcripts needed depending on the stage of development (embryonic, puberty, pregnancy, lactation, involution, and postmenopause). Therefore, it is important to maintain strict regulation at each stage because aberrations in epigenetic regulation can lead to breast cancer. Among the epigenetic regulators are long non-coding RNAs (lncRNAs), which play important roles during the development of the breasts. Further, they can be used as biomarkers in breast cancer since their expression and emergence correlate with the patient's survival, as well as the aggressiveness of the tumor; the lncRNAs lead to epigenetic changes and the activation of signaling pathways, causing an accelerated rate of proliferation, metastasis, and evasion of the action of chemotherapeutic agents. Therefore, lncRNAs may be potential therapeutic targets. In this review, we show examples of lncRNAs that exert resistance on the different subtypes of breast cancer, through the activation of signaling pathways protein kinase b (AKT), the extracellular signal-regulated kinases (ERK), the mammalian target of rapamycin (mTOR), and (wingless/integrated [Wnt])/(beta-catenin). Some of these pathways are shared among the different subtypes, allowing cancer cells to activate the same pathways through different mechanisms, promoting tumor growth and resistance to various therapeutic agents. Furthermore, the mechanisms by which lncRNAs help acquire resistance and strategies to determine their function are presented in this review. [ABSTRACT FROM AUTHOR]