Posttranscriptional Regulation Of Long Non-coding RNA HOTAIR By MiR-221in Hepatocellular Carcinoma

Background:HOX transcript antisense RNA (HOTAIR) is a long non-coding RNA (lnc RNA), which is expressed from the HOXC locus, can simultaneously bind the Polycomb Repressive Complex2(PRC2) and affect its target genes. HOTAIR has been demonstrated to reprogram chromatin organization and promote cancer cell invasion metastasis. MicroRNAs (miRNAs) are about22nt-long noncoding RNAs acting as posttranscriptional regulators of gene expression in animals and plants. Aberrant expression of several miRNAs was found to be involved in numerous human cancers. Hepatocellular carcinoma (HCC) is known as the third cause of cancer-related death worldwide. miR-221and miR-222are two highly homologous miRNAs that always act as a cluster (miR-221/222), which are upregulated in HCC as well as in other malignancies such as bladder carcinomas and glioblastomas. The expression of miR-221is correlated with tumorigenicity and invasiveness in several human cancers.Purpose:This study aims to investigate the role of miR-221in the posttranscriptional reguation of HOTAIR, and to characterize miR-221contribution to hepatocarcinogenesis through modulation of invasion and metastasis.Experimental Design:Transfection of several miRNAs including miR-221in HCC-derived cell lines and then RT-qPCR assay were used to assess HOTAIR expression. Moreover, siRNAs of HOTAIR were used to investigate the level of miR-221expression after knockdown HOTAIR. Dual luciferase reporter assay were used to assess HOTAIR as a direct target of miR-221. HOTAIR downstream genes were measured. HCC tissues were analyzed to assess the clinical relevance of in vitro findings. Finally, wound healing and transwell assays contributed to characterize their role in invasion and metastasis.Results&Conclusions:Enforced miR-221expression caused HOTAIR down-regulation, meanwhile the downstream genes of HOTAIR associated were down-regulated. Dual luciferase reporter assay confirmed HOTAIR as a target of miR-221in posttranscriptional level. Finally, in HCC, wound healing and transwell assays demonstrated that miR-221suppresses HOTAIR expression and functions including metastasis and invasion.