Non-coding RNA HOX Transcript Antisense RNA Research Articles

Abstract AP14: THERAPEUTIC TARGETING USING TUMOR SPECIFIC PEPTIDES INHIBITS LONG NON–CODING RNA HOTAIR ONCOGENIC ACTIVITY IN OVARIAN CANCER

Abstract PURPOSE: Most women diagnosed with advanced-stage ovarian cancer develop chemo-resistant tumor recurrence, which is uniformly fatal. Long non-coding RNAs (lncRNAs) play key roles in human diseases, including cancer. Functional studies of the lncRNA HOTAIR (HOX transcript antisense RNA) provide compelling evidence for therapeutic targeting of HOTAIR in ovarian cancer to impact chemoresistance, but targeting lncRNAs in vivo has proven to be difficult. EXPERIMENTAL DESIGN: In the current study, we describe a peptide nucleic acids (PNA)-based approach to effectively block the ability of HOTAIR to interact with EZH2 and subsequently inhibit oncogenic HOTAIR-EZH2 activity. In order to deliver the anti-lncRNA to the acidic (pH approximately 6) microenvironment of solid tumors in vivo, PNAs were conjugated to pH-low insertion peptide (pHLIP). RESULTS: Treatment of HOTAIR-overexpressing ovarian cancer cell lines with PNAs decreased cancer cell invasion and increased chemotherapy sensitivity. The mechanism of action of the anti-lncRNA agent correlated with reduced nuclear factor-kappaB (NF-κB) activation and decreased expression of key NF-κB target genes including matrix metalloprotease 9 and interleukin 6. PNA treatment of ALDH1A1 positive/ovarian tumor initiating cells overexpressing HOTAIR markedly decreased ALDH1A1 activity and reduced the ovarian cancer stem cell population. In mice harboring ovarian tumor xerographs and treated with pHLIP-PNA constructs, HOTAIR oncogenic activity was suppressed, ovarian tumors were resensitized to platinum, and a significant (64%) survival improvement was observed. CONCLUSIONS: Toward developing new therapeutic approaches against chemoresistant ovarian cancer, we designed a PNA-targeting strategy for HOTAIR that effectively blocks the ability of HOTAIR to interact with EZH2 and inhibits oncogenic HOTAIR-EZH2. This first report on pHLIP-PNA targeting HOTAIR in vivo offer pre-clinical proof-of-concept and represents a possible treatment alternative for chemotherapy-resistant ovarian cancer. Citation Format: Ali R. Özeş, Yinu Wang, Fang Fang, and Kenneth P. Nephew. THERAPEUTIC TARGETING USING TUMOR SPECIFIC PEPTIDES INHIBITS LONG NON–CODING RNA HOTAIR ONCOGENIC ACTIVITY IN OVARIAN CANCER [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr AP14.

Therapeutic targeting using tumor specific peptides inhibits long non-coding RNA HOTAIR activity in ovarian and breast cancer

Long non-coding RNAs (lncRNAs) play key roles in human diseases, including cancer. Functional studies of the lncRNA HOTAIR (HOX transcript antisense RNA) provide compelling evidence for therapeutic targeting of HOTAIR in cancer, but targeting lncRNAs in vivo has proven to be difficult. In the current study, we describe a peptide nucleic acids (PNA)-based approach to block the ability of HOTAIR to interact with EZH2 and subsequently inhibit HOTAIR-EZH2 activity and resensitize resistant ovarian tumors to platinum. Treatment of HOTAIR-overexpressing ovarian and breast cancer cell lines with PNAs decreased invasion and increased chemotherapy sensitivity. Furthermore, the mechanism of action correlated with reduced nuclear factor-kappaB (NF-κB) activation and decreased expression of NF-κB target genes matrix metalloprotease 9 and interleukin 6. To deliver the anti-lncRNA to the acidic (pH approximately 6) tumor microenvironment, PNAs were conjugated to pH-low insertion peptide (pHLIP). Treatment of mice harboring platinum-resistant ovarian tumor xenografts with pHLIP-PNA constructs suppressed HOTAIR activity, reduced tumor formation and improved survival. This first report on pHLIP-PNA lncRNA targeting solid tumors in vivo suggests a novel cancer therapeutic approach.

Epigenetic inhibition of miR-663b by long non-coding RNA HOTAIR promotes pancreatic cancer cell proliferation via up-regulation of insulin-like growth factor 2.

Pancreatic cancer is one of the most deadly cancers with a poor prognosis. Although microRNAs are involving in the carcinogenesis and development of pancreatic cancer, little information is known regarding the role of miR-663b in pancreatic cancer. In this study, the expression of miR-663b in pancreatic cancer cells was down-regulated by hypermethylation in its putative promoter region, and overexpression of miR-663b repressed cell proliferation, invasion and migration, and induced apoptosis in pancreatic cancer cells. Bioinformatics analysis, luciferase report assay and rescue experiments showed that insulin-like growth factor 2 (IGF2) was a direct target of miR-663b. Results from clinical samples showed that the expression level of miR-663b correlated with the pathological grading, and the expression of miR-663b was down-regulated and was inversely correlated with IGF2 expression level in pancreatic cancer tissues. More importantly, the long non-coding RNA, HOX transcript antisense RNA (HOTAIR), was up-regulated in both pancreatic cancer cells and tissues, and HOTAIR suppressed the expression of miR-663b in pancreatic cancer by histone modification on H3K4me3 and H3K27me3 on miR-663b promoter. Further in vivo studies demonstrated that the stable overexpression of miR-663b or knock-down of HOTAIR inhibited tumor growth and was associated with IGF2 expression. In summary, our studies demonstrated that miR-663b is epigenetically repressed by HOTAIR and exerts its tumor-suppressive function via targeting IGF2 in pancreatic cancer.

Long Noncoding RNA HOTAIR Controls Cell Cycle by Functioning as a Competing Endogenous RNA in Esophageal Squamous Cell Carcinoma

Recent studies have shown that long noncoding RNAs (lncRNAs) play pivotal roles in the initiation and progression of cancer, including esophageal squamous cell carcinoma (ESCC). The lncRNA HOX transcript antisense RNA (HOTAIR) was reported to be dysregulated and correlated with the progression of ESCC. However, the biological role and the underlying mechanism of HOTAIR in the development of ESCC remain unclear. Herein, we found that HOTAIR was aberrantly upregulated in ESCC cells and that HOTAIR depletion inhibited proliferation and led to G1 cell cycle arrest in ESCC cells. Besides, we found that HOTAIR acted as an endogenous sponge to downregulate miR-1 expression by directly binding to miR-1. Furthermore, HOTAIR overturned the effect of miR-1 on the proliferation and cell cycle profile in ESCC cells, which involved the derepression of cyclin D1 (CCND1) expression, a target of miR-1. Taken together, our study elucidated a novel HOTAIR /miR-1/CCND1 regulatory axis in which HOTAIR acted as a competing endogenous RNA by sponging miR-1 and upregulated CCND1 expression, thereby facilitating the tumorigenesis of ESCC. Investigation of this lncRNA/miRNA/mRNA pathway may contribute to a better understanding of ESCC pathogenesis and facilitate the development of lncRNA-directed therapy against this disease.

Suppression of PDCD4 mediated by the long non-coding RNA HOTAIR inhibits the proliferation and invasion of glioma cells.

Programmed cell death protein 4 (PDCD4) has recently been demonstrated to be implicated in translation and transcription, and the regulation of cell growth. However, the mechanisms underlying PDCD4 function in glioma cells remain to be elucidated. The current study investigated the function and regulation of PDCD4 and the results demonstrated that the expression of PDCD4 was significantly reduced in glioma cells compared with normal cells. When PDCD4 was overexpressed in glioma cells, the proliferation rate and invasive capability of the cells greatly decreased, suggesting that PDCD4 functions as a tumor suppressor in this cell type. In addition, the histone modification status of the PDCD4 gene was analyzed, and chromatin immunoprecipitation assay identified a high density of histone 3 lysine 27 trimethylation on the promoter of PDCD4, which was associated with the long non-coding RNA, homeobox transcript antisense RNA (HOTAIR). The expression of HOTAIR was significantly increased in glioma cells compared with normal cells, and it exerted its function in a polycomb repressive complex 2-dependent manner. These results may provide novel approaches to therapeutically target PDCD4 and HOTAIR in patients with gliomas.

Long non-coding RNA HOTAIR modulates HLA-G expression by absorbing miR-148a in human cervical cancer.

The long non-coding RNA HOX transcript antisense RNA (HOTAIR) has been found overexpressed in many human malignancies and involved in tumor progression and metastasis. However, little is known about the potential biological roles of HOTAIR in tumor escape. In the present study, the expression of HOTAIR was detected in 59 paired cervical cancer tissue samples by real-time PCR and then subjected to correlation analysis with clinical features. The effects of HOTAIR on cervical cancer cells as well as the expression of human leukocyte antigen (HLA)-G were studied by overexpression and RNA interference approaches. Insight into the mechanism of HOTAIR acting as competitive endogenous RNAs (ceRNAs) was gained from bioinformatic analysis and luciferase assays. HOTAIR expression was obviously increased in cervical cancer tissue. HOTAIR upregulation was associated with advanced pathological stage, histology, lymph node invasion and lymphatic metastasis, and also correlated with shorter overall survival of cervical cancer patients. Furthermore, HOTAIR overexpression promoted the proliferation, migration and invasion of cervical cancer cells, while HOTAIR knockdown inhibited cell invasion and cell viability, induced apoptosis and inhibited growth invitro and invivo. Moreover, HOTAIR modulated human leucocyte antigen-G (HLA-G) expression by competitively binding miR-148a. Our data suggest that HOTAIR plays an important oncogenic role in cervical cancer and might serve as a marker for cervical cancer prognosis and a potential target for therapeutic intervention.

NF-κB-HOTAIR axis links DNA damage response, chemoresistance and cellular senescence in ovarian cancer.

The transcription factor nuclear factor kappa B (NF-κB) and the long non-coding RNA (lncRNA) HOTAIR (HOX transcript antisense RNA) play diverse functional roles in cancer. In this study, we show that upregulation of HOTAIR induced platinum resistance in ovarian cancer, and increased HOTAIR levels were observed in recurrent platinum-resistant ovarian tumors vs. primary ovarian tumors. To investigate the role of HOTAIR during DNA damage induced by platinum, we monitored double-strand breaks and show that HOTAIR expression results in sustained activation of DNA damage response after platinum treatment. We demonstrate that ectopic expression of HOTAIR induces NF-κB activation during DNA damage response and MMP-9 and IL-6 expression, both key NF-κB target genes. We show that HOTAIR regulates activation of NF-κB by decreasing Iκ-Bα (NF-κB inhibitor) and establish that by inducing prolonged NF-κB activation and expression of NF-κB target genes during DNA damage, HOTAIR plays a critical role in cellular senescence and platinum sensitivity. Our findings suggest that a NF-κB-HOTAIR axis drives a positive-feedback loop cascade during DNA damage response and contributes to cellular senescence and chemotherapy resistance in ovarian and other cancers.

Long Non-coding RNA HOTAIR Promotes Parkinson's Disease Induced by MPTP Through up-regulating the Expression of LRRK2.

Homeobox (HOX) transcript antisense RNA (HOTAIR), as a long intergenic noncoding RNA (lincRNA), is known to be overexpressed in several cancers. However, the role of HOTAIR in Parkinson's disease (PD) remains unclear. A mouse model of PD was developed by intraperitoneal injection of MPTP (N-methyl-4-phenyl-1,2,3,6- tetrahydropyridine). The expression of HOTAIR and LRRK2 (leucine-rich repeat kinase 2) were detected in the PD mice and in Human neuroblastoma cell lines SH-SY5Y pretreated with MPP+ (N-methyl-4-phenylpyridinium). The effect of HOTAIR on the expression of LRRK2 was examined in SH-SY5Y cells through overexpressing HOTAIR. A MTT (3- (4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide) assay was performed to measure the cell viability of SH-SY5Y cells. si-HOTAIR (siRNA-HOTAIR) was utilized to investigate the effect of HOTAIR on the expression of LRRK2 in vivo. In this study, upregulation of HOTAIR and LRRK2 were found in the midbrain of PD mice induced by MPTP and in SH-SY5Y cells pretreated with MPP+. With the presence of HOTAIR overexpression in SH-SY5Y cells, the expression of LRRK2 was increased compared with that in the control. HOTAIR knockdown showed a protective effect on the cell viability of SH-SY5Y cells pretreated with MPP+, which was abrogated by overexpression of LRRK2. In mouse model of PD treated with si-HOTAIR, the expression of LRRK2 was decreased. In conclusion, high expression of HOTAIR promoted the onset of PD induced by MPTP. Moreover, the finding that HOTAIR promoted PD induced by MPTP through regulating LRRK2 expression could add our understanding of the molecular mechanisms in PD.

Expression of the Long Non-Coding RNA HOTAIR Correlates with Disease Progression in Bladder Cancer and Is Contained in Bladder Cancer Patient Urinary Exosomes.

Exosomes are 30-150nM membrane-bound secreted vesicles that are readily isolated from biological fluids such as urine (UEs). Exosomes contain proteins, micro RNA (miRNA), messenger RNA (mRNA), and long non-coding RNA (lncRNA) from their cells of origin. Although miRNA, protein and lncRNA have been isolated from serum as potential biomarkers for benign and malignant disease, it is unknown if lncRNAs in UEs from urothelial bladder cancer (UBC) patients can serve as biomarkers. lncRNAs are > 200 nucleotide long transcripts that do not encode protein and play critical roles in tumor biology. As the number of recognized tumor-associated lncRNAs continues to increase, there is a parallel need to include lncRNAs into biomarker discovery and therapeutic target algorithms. The lncRNA HOX transcript antisense RNA (HOTAIR) has been shown to facilitate tumor initiation and progression and is associated with poor prognosis in several cancers. The importance of HOTAIR in cancer biology has sparked interest in using HOTAIR as a biomarker and potential therapeutic target. Here we show HOTAIR and several tumor-associated lncRNAs are enriched in UEs from UBC patients with high-grade muscle-invasive disease (HGMI pT2-pT4). Knockdown of HOTAIR in UBC cell lines reduces in vitro migration and invasion. Importantly, loss of HOTAIR expression in UBC cell lines alters expression of epithelial-to-mesenchyme transition (EMT) genes including SNAI1, TWIST1, ZEB1, ZO1, MMP1 LAMB3, and LAMC2. Finally, we used RNA-sequencing to identify four additional lncRNAs enriched in UBC patient UEs. These data, suggest that UE-derived lncRNA may potentially serve as biomarkers and therapeutic targets.

Long non-coding RNA HOTAIR is a marker for hepatocellular carcinoma progression and tumor recurrence.

The present study aimed to investigate the expression level of HOX transcript antisense RNA (HOTAIR) in hepatocellular carcinoma (HCC) and its association with various clinicopathological characteristics, and to further explore the molecular mechanisms of HOTAIR function in HCC. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) was used to detect the expression level of HOTAIR in 60 paired fresh HCC samples and adjacent normal liver tissue samples. The association between HOTAIR expression and clinicopathological parameters was analyzed. Lentivirus-mediated HOTAIR-specific small hairpin RNA vectors were transfected into HepG2 cells. Cell proliferation and invasion in vitro were examined by MTT and Transwell assays, respectively. A xenograft model was used to analyze the tumorigenesis of liver cancer cells in vivo. In addition, semi-quantitative RT-PCR was used to detect the expression level of Wnt/β-catenin signaling molecules under the condition of HOTAIR inhibition. The results revealed that the expression level of HOTAIR in HCC tissues was higher than that in adjacent non-cancerous tissues. HOTAIR expression was significantly associated with poor tumor differentiation (P=0.002), metastasis (P=0.002) and early recurrence (P=0.001). In vitro, the inhibition of HOTAIR in liver cancer cells resulted in the suppression of cell proliferation and invasion. HOTAIR depletion significantly inhibited the rate of growth of liver cancer cells in vivo. Furthermore, the expression levels of Wnt and β-catenin were downregulated when HOTAIR expression was suppressed. In conclusion, HOTAIR is important in the progression and recurrence of HCC, partly through the regulation of the Wnt/β-catenin signaling pathway. Targeting HOTAIR may be a novel therapeutic strategy for HCC.

A Feed-Forward Regulatory Loop between HuR and the Long Noncoding RNA HOTAIR Promotes Head and Neck Squamous Cell Carcinoma Progression and Metastasis

Background/Aims: The lncRNA Homeobox (HOX) transcript antisense RNA (HOTAIR) is overexpressed in numerous cancers. HuR is also overexpressed during tumourigenesis and is abnormally present within the cytoplasm, where it binds to AU-rich elements in the 3′UTRs of target mRNA and post-transcriptionally regulates the expression of its target genes. However, whether HOTAIR is regulated and the mechanisms by which it affects head and neck squamous cell carcinoma (HNSCC) are not well understood. Methods: MTT, cell cycle arrest and apoptotic assays were used to examine the effects of HOTAIR and HuR on cell viability in SCC25 and FaDu cells. Wound healing and transwell invasion analysis were performed to detect the effects of HOTAIR and HuR on cell migration and invasion. The interaction between HuR and HOTAIR was confirmed via qRT-PCR, western blots, luciferase reporter and RIP assays. Finally, qRT-PCR analysis was used to detect the levels of HuR and HOTAIR in HNSCC tumours and adjacent normal tissues. Results: Knockdown of HOTAIR and HuR decreased cell viability, cellular migration and invasion. Moreover, HuR interacted and stabilized HOTAIR stability and thus promoted HOTAIR expression. Notably, HOTAIR acted as a miRNA sponge for HuR. HuR also reinforced HOTAIR sponge activity through miRNA recruitment, thus enhancing HuR expression in turn. Finally, HuR and HOTAIR levels were positively correlated and significantly up-regulated in tumours samples. Conclusion: We demonstrated the existence of a regulatory loop in which the expression of HOTAIR and HuR is reciprocally and temporally regulated during the metastasis and progression of HNSCC.

The long noncoding RNA HOTAIR activates autophagy by upregulating ATG3 and ATG7 in hepatocellular carcinoma.

The long noncoding RNA HOX transcript antisense RNA (HOTAIR) has been reported to be an oncogene that influences tumor cell development and that correlates with prognosis in hepatocellular carcinoma (HCC). Accumulating evidence indicates that autophagy plays a significant role in tumorigenesis and cancer cell survival, but whether HOTAIR modulates autophagy in HCC cells remains unknown. In this study, HOTAIR expression was measured in 54 matched paired HCC tissues and the adjacent non-tumor tissues. HOTAIR was overexpressed in the HCC tissues as compared with the adjacent non-tumor tissues and was associated with tumor size. In vitro assays revealed that the overexpression of HOTAIR promoted the activation of autophagy in HCC cell lines, whereas HOTAIR knockdown suppressed it. Further investigation revealed that overexpressed HOTAIR upregulated autophagy-related 3 (ATG3) and ATG7 expression in HCC cells. In conclusion, HOTAIR, overexpressed in HCC and associated with tumor size, could activate autophagy by increasing ATG3 and ATG7 expression, promoting HCC cell proliferation.

Long non-coding RNA HOTAIR regulates cyclin J via inhibition of microRNA-205 expression in bladder cancer.

The level of microRNA-205 (miR-205) is commonly deregulated in a number of cancers. Through the screening of the microRNA expression profile in bladder cancer tissue and cell lines, we found that expression of miR-205 was significantly suppressed. In addition, the levels of miR-205 expression had a negative correlation with the degree of bladder cancer malignancy. However, the biological functions of miR-205 remained unclear. In this study, we have demonstrated that miR-205 had a role in the inhibition of proliferation, migration and invasion of bladder cancer cells. Moreover, we have identified cyclin J (CCNJ) gene, which is involved in cell cycle regulation, as a novel target for miR-205. Furthermore, a long non-coding RNA HOTAIR (HOX transcript antisense RNA) was observed to participate in the silencing of miR-205 in bladder cancer cells by breaking the balance of histone modification between H3K4me3 (histone H3 at lysine 4 methylation) and H3K27me3 on miR-205 promoter. This study elucidates an important role that miR-205 had in the regulation of proliferation, migration and invasion of bladder cancer cells, suggesting a potential therapeutic target for combating bladder cancer.

Influence of long noncoding RNA HOTAIR on human glioma cell metabolism and growth

Objective To investigate the influence of long noncoding RNA HOX transcript antisense RNA (HOTAIR) on human glioma cell metabolism and growth. Methods The fluorescently labeled small interfering (si-HOTAIR) was used to transfect glioma U87 and U251 cell lines. The real-time polymerase chain reaction (RT-PCR) was used to detect the expression level of HOTAIR in glioma cells. CCK8 test and colony formation assay were used to detect the growth changes of the glioma cells. Seahorse BioScience XF glycilysis stress test kit and XF mitochondrial stress test kit were used to detect the cell aerobic glycolysis and mitochondrial function. Western blot was used to detect glycolysis related enzymes, including the expression levels of glucose-6-phosphate isomerase (GPI), Pyruvate kinase M2 (PKM2), and lactate dehydrogenase A (LDHA). Results The transfection efficiency of si-HOTAIR in U87and U251cells observed under a fluorescence microscope was more than 90%. The HOTAIR expression in the cells of the si-HOTAIR group was downregulated significantly compared with the negative control group (P<0.01). The proliferative ability and clonal formation ability of the U87and U251 glioma cells of the si-HOTAIR group were significantly lower that than those of the negative group (P<0.01). After downregulation of HOTAIR, the aerobic glycolysis capacity of glioma cells were diminished, showing reduced based glycolysis level (P<0.05), diminished maximum glycolytic capacity (P<0.01), and decreased remaining amount of glycolysis (P<0.01). The expression levels of GPI, PKM2 and LDHA of the si-HOTAIR group were lower than those of the negative control group (P<0.01). After downregulation of HOTAIR, the mitochondrial function in glioma cells was impaired, showing decreased basal respiration level (U87 cells P<0.01), decreased mitochondrial coupling efficiency, and diminished residual respiration ability (P<0.05). Conclusions Downregulation of HOTAIR expression may impair the glycolytic capacity and mitochondrial function of glioma cells, simultaneously influence the growing ability of glioma cells. Key words: Glioma; Mitochondria; Metabolism; Glycolysis; Proliferation; Long noncoding RNA; HOX transcript antisense RNA

Long non-coding RNA HOTAIR promotes tumor cell invasion and metastasis by recruiting EZH2 and repressing E-cadherin in oral squamous cell carcinoma.

HOX transcript antisense RNA (HOTAIR), a long intergenic non-coding RNA (lncRNA), functions as a molecular scaffold to link and target the histone modification complexes PRC2 and LSD1, then reprograms chromatin states by coupling histone H3K27 methylation and H3K4 demethylation for epigenetic gene silencing to promote cancer metastasis. It is associated with poor survival in several solid cancers. In this study, we show that HOTAIR expression increased in oral squamous cell carcinoma (OSCC) compared with non-tumor tissue and is associated with metastasis, the stage and histological differentiation. In addition, overexpression of HOTAIR indicated poor overall survival (OS) and disease-free survival (DFS) in OSCC patients. Knockdown of HOTAIR by siRNA in OSCC cells decreased cell proliferation and colony formation, increased cell invasion and migration, and induced apoptosis in vitro. Furthermore, significant negative correlation between HOTAIR levels and E-cadherin levels was found in OSCC tissues and cell lines, and HOTAIR contributed to the regulation of E-cadherin through binding to EZH2 and H3K27me3 with the E-cadherin promoter. Our findings suggest that HOTAIR expression is associated with OSCC and may be one of critical targets in progression and metastasis, and an indicator of poor survival in OSCC.

The long non-coding RNA HOTAIR promotes the proliferation of serous ovarian cancer cells through the regulation of cell cycle arrest and apoptosis

HOX transcript antisense RNA (HOTAIR) is a well-known long non-coding RNA (lncRNA) whose dysregulation correlates with poor prognosis and malignant progression in many forms of cancer. Here, we investigate the expression pattern, clinical significance, and biological function of HOTAIR in serous ovarian cancer (SOC). Clinically, we found that HOTAIR levels were overexpressed in SOC tissues compared with normal controls and that HOTAIR overexpression was correlated with an advanced FIGO stage and a high histological grade. Multivariate analysis revealed that HOTAIR is an independent prognostic factor for predicting overall survival in SOC patients. We demonstrated that HOTAIR silencing inhibited A2780 and OVCA429 SOC cell proliferation in vitro and that the anti-proliferative effects of HOTAIR silencing also occurred in vivo. Further investigation into the mechanisms responsible for the growth inhibitory effects by HOTAIR silencing revealed that its knockdown resulted in the induction of cell cycle arrest and apoptosis through certain cell cycle-related and apoptosis-related proteins. Together, these results highlight a critical role of HOTAIR in SOC cell proliferation and contribute to a better understanding of the importance of dysregulated lncRNAs in SOC progression.

Progress of Long Noncoding RNA HOTAIR in Human Cancer

Long noncoding RNA(lnc RNA) play important roles in cancer progression. HOX transcript antisense RNA(HOTAIR) was observed upregulated in a variety of tumors. Over-expression of HOTAIR is a poor prognostic factor. HOTAIR interacts with Polycomb Repressive complex 2(PRC2), resulting in histone H3tri-methylated atlysine27(H3K27me3), which silences the expression of some down-stream genes, such as WIF-1,PTEN and p21, then mediated Wnt, Akt and p53 signaling pathways transduction. As a result, the properties of tumor, including invasion and metastasis, evading growth suppressors, resisting apoptosis and inducing angiogenesis would be affected. Thoroughly elucidate mechanisms of HOTAIR in cancer development will have important theoretical significance in cancer etiology and pathogenesis. As an important biomarker and potential target, HOTAIR may also has important clinical application in cancer's early diagnosis, therapeutic evaluation,prognosis, and even potential gene therapy.

Genetic variants in lncRNA HOTAIR are associated with risk of colorectal cancer.

Long non-coding RNA HOX transcript antisenseRNA (HOTAIR) has been widely identified to participate in tumour pathogenesis, acting as a promoter in colorectal cancer carcinogenesis. However, the association between genetic variants in HOTAIR and cancer risk has not yet been reported. In the present study, we performed a two-stage case-control study to investigate the association between HOTAIR tagSNPs and the risk of colorectal cancer. We found that individuals with rs7958904 CC genotype had a significantly decreased risk of colorectal cancer in both Stage 1 and 2, compared with those carrying GG genotype [odds ratio (OR) = 0.70, 95% confidence interval (CI) = 0.51-0.97 in Stage 1; OR = 0.58, 95% CI = 0.37-0.91 in Stage 2; OR = 0.67, 95% CI = 0.51-0.87 in combined stage]. The subsequently stratified analyses showed that the protective effect of rs7958904 was more pronounced in several subgroups. In summary, our study showed that genetic variants in HOTAIR were associated with risk of colorectal cancer and rs7958904 may act as a potential biomarker for predicting the risk of colorectal cancer.

Long noncoding RNA HOTAIR involvement in cancer.

Evidences have been provided that long noncoding RNAs (lncRNAs) act as key molecules in epigenetic regulation and are involved in the development process of cancer in recent studies. HOX transcript antisense RNA (HOTAIR), a long intergenic noncoding RNA (lincRNA), functions as a molecular scaffold to link and target two histone modification complexes PRC2 and LSD1, then reprograms chromatin states by couples histone H3K27 methylation and H3K4 demethylation for epigenetic gene silencing to promote cancer metastasis. HOTAIR, regarded as an oncogene, is pervasively overexpressed in most solid cancers and correlated with tumor invasion, progression, metastasis, and poor prognosis, and HOTAIR has been proven to play a critical role in most biological process of cancer and would be a potential new target in cancer therapy.

Suppressed expression of long non-coding RNA HOTAIR inhibits proliferation and tumourigenicity of renal carcinoma cells.

Although long non-coding RNAs (lncRNAs) are known to play an important role in cell regulation in several cancers, the regulatory mechanisms in renal carcinoma cells remain unclear. HOX transcript antisense RNA (HOTAIR), an lncRNA, coordinates with chromatin-modifying enzymes to regulate gene silencing. HOTAIR is over-expressed in several types of carcinoma cells. Thus, we hypothesised that lncRNA HOTAIR is crucial for cell proliferation and invasion and that its knockdown induces apoptosis in renal carcinoma cells. lncRNA HOTAIR expression was found to be elevated in renal carcinoma cells. Additionally, lncRNA HOTAIR knockdown by RNA interference with siRNA was found to significantly affect the cell cycle in the G0/G1 phase and weaken the abilities of cell proliferation and invasion in vitro. Xenograft experiments confirmed that the growth of xenograft tumours formed by renal carcinoma cells was suppressed after silencing lncRNA HOTAIR expression. Moreover, chromatin immunoprecipitation (ChIP) and RNA-binding protein immunoprecipitation (RIP) assays revealed that knockdown of lncRNA HOTAIR led to the weakening of the recruitment and binding abilities of EZH2 and H3K27me3 locus with lncRNA HOTAIR. Furthermore, the cell cycle-related gene locus was in an active transcriptional state by the silencing of lncRNA HOTAIR expression and modulation of covalent histones.