lncRNA Growth Arrest-specific 5 Research Articles

Decreased expression of long non-coding RNA GAS5 indicates a poor prognosis and promotes cell proliferation and invasion in hepatocellular carcinoma by regulating vimentin.

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related mortality worldwide. Recent studies have demonstrated that long non-coding RNAs (lncRNAs) are key in carcinogenesis. The aim of the present study was to investigate the role of lncRNA GAS5 in HCC tissues and to define the role of growth arrest-specific 5 (GAS5) in the regulation of hepatoma cell proliferation, invasion and apoptosis. Quantitative polymerase chain reaction and in situ hybridization were performed to investigate the expression of GAS5 in tumor tissues and corresponding adjacent tissues from 50 patients with HCC. Low expression of GAS5 was significantly correlated with differentiation (P<0.010) and portal vein tumor thrombosis (P=0.001). Multivariate analysis indicated that GAS5 expression was an independent predictor for overall survival (P=0.017). Further experiments demonstrated that overexpression of GAS5 significantly suppressed the proliferation and invasion of hepatoma cells in vitro. Overexpression of GAS5 significantly promoted the apoptosis of hepatoma cells. In addition, it was demonstrated that GAS5 negatively regulates vimentin expression in vitro and in vivo. Notably, vimentin knockdown promoted GAS5-pcDNA3.1-inhibition of hepatoma cell proliferation. In conclusion, the present study suggests an important role of GAS5 in the molecular etiology of HCC and suggests the potential application of GAS5 in HCC therapy.

Negative regulation of lncRNA GAS5 by miR-21

In addition to protein-coding genes, the human genome makes a large amount of noncoding RNAs, including microRNAs and long noncoding RNAs (lncRNAs). Both microRNAs and lncRNAs have been shown to have a critical role in the regulation of cellular processes such as cell growth and apoptosis, as well as cancer progression and metastasis. Although it is well known that microRNAs can target a large number of protein-coding genes, little is known whether microRNAs can also target lncRNAs. In the present study, we determine whether miR-21 can regulate lncRNA expression. Using the lncRNA RT-PCR (reverse transcription-polymerase chain reaction) array carrying 83 human disease-related lncRNAs, we show that miR-21 is capable of suppressing the lncRNA growth arrest-specific 5 (GAS5). This negative correlation between miR-21 and GAS5 is also seen in breast tumor specimens. Of interest, GAS5 can also repress miR-21 expression. Whereas ectopic expression of GAS5 suppresses, GAS5-siRNA increases miR-21 expression. Importantly, there is a putative miR-21-binding site in exon 4 of GAS5; deletion of the miR-21-binding site abolishes this activity. Experiments with in vitro cell culture and xenograft mouse model suggest that GAS5 functions as a tumor suppressor. We further show that the biotin-labeled GAS5-RNA probe is able to pull down the key component (AGO2) of the RNA-induced silencing complex (RISC) and we subsequently identify miR-21 in this GAS5-RISC complex, implying that miR-21 and GAS5 may regulate each other in a way similar to the microRNA-mediated silencing of target mRNAs. Together, these results suggest that miR-21 targets not only tumor-suppressive protein-coding genes but also lncRNA GAS5.

Abstract 1829: Negative regulation of lncRNA GAS5 by miR-21.

Abstract Protein-coding genes account for only a small part of the human genome whereas the vast majority of transcripts make up the non-coding RNAs including microRNAs and long non-coding RNAs (lncRNAs). Both microRNAs and lncRNAs have been shown to play a critical role in regulation of cellular processes such as cell growth and apoptosis as well as cancer progression and metastasis. As master gene regulators, microRNAs can target a large number of protein-coding genes. However, it remains to be determined whether microRNAs can also target lncRNAs. In the present study, we determined whether miR-21 impacts lncRNA expression. Using lncRNA RT-PCR array carrying 83 human disease related lncRNAs, we showed that miR-21 was capable of repressing the growth arrest specific 5 (GAS5) lncRNA which was previously shown to be involved in growth arrest. This negative regulation between miR-21 and GAS5 was confirmed in breast tumor specimens. Of interest, GAS5 can also repress miR-21 expression. While ectopic expression of GAS5 suppressed, GAS5 siRNAs increased miR-21 expression. Importantly, there was a putative miR-21 binding site in exon 5 of GAS5; deletion of the miR-21 binding site abolished this activity. We further showed that biotin labeled GAS5 RNA probe was able to pull down the RNA-induced silencing complex (RISC) and subsequently identified miR-21 in this GAS5-RISC complex, implying that miR-21 and GAS5 may regulate each other in a way similar to the microRNA-mediated silencing of target mRNAs. Together, these results support the “endogenous competitive RNA” concept that microRNAs may regulate not only protein-coding genes, but also non-coding genes such as GAS5. Citation Format: Ziqiang Zhang, Yin-yuan Mo. Negative regulation of lncRNA GAS5 by miR-21. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1829. doi:10.1158/1538-7445.AM2013-1829