In the recent years the importance of the role played by non-coding RNA on the regulation of
gene expression was increased by numerous studies. The research mainly focused on small ncRNAs,
such as miRNAs, while the functions of long non-coding RNA (lncRNA) have been much less studied.
lncRNAs can be transcribed from intergenic, intragenic or specific chromosomal regions. Compared to
miRNAs, lncRNAs have a complex secondary and tertiary structure which allows to bind proteins,
RNA, DNA and to carry out their regulatory functions. Several studies showed that extracellular
ncRNAs can circulate in the blood of both healthy and diseased patients. Most of the circulating
ncRNAs are included in lipid or lipoprotein vesicles, such as apoptotic bodies, macrovesicles or
exosomes, in which they are highly stable. The presence of circulating ncRNAs in the blood of cancer
patients versus normal subjects suggested the possibility that these molecules may represent new diagnostic
markers. HOTAIR is a HOX transcript antisense RNA, located in the HOXC locus, able to
repress transcription in the posterior region of the HOXD locus. HOTAIR has been <involved in the
evolution of several primary tumors, wherein increase of HOTAIR expression has endorsed invasion
and metastasis. In this review, we describe the experimental evidences on the potential role as circulating
marker of lncRNA HOTAIR.