HOTAIR Transcription Research Articles

HOTAIR Promotes the Hyperactivation of PI3K/Akt and Wnt/β-Catenin Signaling Pathways via PTEN Hypermethylation in Cervical Cancer.

The mechanisms underlying the sustained activation of the PI3K/AKT and Wnt/β-catenin pathways mediated by HOTAIR in cervical cancer (CC) have not been extensively described. To address this knowledge gap in the literature, we explored the interactions between these pathways by driving HOTAIR expression levels in HeLa cells. Our findings reveal that HOTAIR is a key regulator in sustaining the activation of both signaling pathways. Specifically, altering HOTAIR expression-either by knockdown or overexpression-significantly influenced the transcriptional activity of the PI3K/AKT and Wnt/β-catenin pathways. Additionally, we discovered that HIF1α directly induces HOTAIR transcription, which in turn leads to the epigenetic silencing of the PTEN promoter via DNMT1. This process leads to the sustained activation of both pathways, highlighting a novel regulatory axis involving HOTAIR and HIF1α in cervical cancer. Our results suggest a new model in which HOTAIR sustains reciprocal activation of the PI3K/AKT and Wnt/β-catenin pathways through the HOTAIR/HIF1α axis, thereby contributing to the oncogenic phenotype of cervical cancer.

JMJD6–BRD4 complex stimulates lncRNA HOTAIR transcription by binding to the promoter region of HOTAIR and induces radioresistance in liver cancer stem cells

BackgroundLong non-coding RNA (lncRNA) HOTAIR acts importantly in liver cancer development, but its effect on radioresistance remains poorly understood. Here, our study probed into the possible impact of HOTAIR in radioresistance in liver cancer stem cells (LCSCs) and to elucidate its molecular basis.MethodsFollowing sorting of stem and non-stem liver cancer cells, LCSCs were identified and subjected to RNA-seq analysis for selecting differentially expressed genes. Expression of HOTAIR was determined in liver cancer tissues and CSCs. The stemness, proliferation, apoptosis and radioresistance of LCSCs were then detected in response to altered expression of HOTAIR-LSD1-JMJD6-BRD4.ResultsEctopic HOTAIR expression was found to promote radioresistance of LCSCs by maintaining its stemness. Mechanistic investigations indicated that HOTAIR recruited LSD1 to the MAPK1 promoter region and reduced the level of H3K9me2 in the promoter region, thus elevating ERK2 (MAPK1) expression. JMJD6–BRD4 complex promoted HOTAIR transcription by forming a complex and positively regulated ERK2 (MAPK1) expression, maintaining the stemness of LCSCs, and ultimately promoting their radioresistance in vitro and in vivo.ConclusionCollectively, our work highlights the promoting effect of the JMJD6–BRD4 complex on the radioresistance of LCSCs through a HOTAIR-dependent mechanism.

Ancestrally Duplicated Conserved Noncoding Element Suggests Dual Regulatory Roles of HOTAIR in cis and trans.

SummaryHOTAIR was proposed to regulate either HoxD cluster genes in trans or HoxC cluster genes in cis, a mechanism that remains unclear. We have identified a 32-nucleotide conserved noncoding element (CNE) as HOTAIR ancient sequence that likely originated at the root of vertebrate. The second round of whole-genome duplication resulted in one copy of the CNE within HOTAIR and another copy embedded in noncoding transcript of HOXD11. Paralogous CNEs underwent compensatory mutations, exhibit sequence complementarity with respect to transcripts directionality, and have high affinity in vitro. The HOTAIR CNE resembled a poised enhancer in stem cells and an active enhancer in HOTAIR-expressing cells. HOTAIR expression is positively correlated with HOXC11 in cis and negatively correlated with HOXD11 in trans. We propose a dual modality of HOTAIR regulation where transcription of HOTAIR and its embedded enhancer regulates HOXC11 in cis and sequence complementarity between paralogous CNEs suggests HOXD11 regulation in trans.

LncRNA HOTAIR promotes cell migration and invasion by regulating MKL1 via inhibition miR206 expression in HeLa cells

BackgroundLong non-coding RNAs (lncRNAs) have emerged as a new and crucial layer of gene regulation in recent years and regulate various biological processes such as carcinogenesis and metastasis. LncRNA HOTAIR, an oncogenic lncRNA, is involved in human tumorigenesis and dysregulated in cervical cancer. Megakaryoblastic leukemia 1 (MKL1), as a transcription coactivity factor, involved in cancer metastasis and cell differentiation. However, the precise mechanism of biological roles of HOTAIR and MKL1 in cancer cells remain unclear.MethodsThe expression levels of HOTAIR and MKL1 were measured by quantitative PCR (qPCR), immunoblotting, in situ hybridization (ISH) and immunohistochemistry (IHC). Wound-healing and transwell assays were used to examine the invasive abilities of HeLa cells. Luciferase reporter assays and CHIP were used to determine how MKL1 regulates HOTAIR. Tissue microarray and immunohistochemical staining were used to assess the correlation between HOTAIR and MKL1 in Cervical cancer tissues in vivo.ResultIn this study, we have identified that MKL1 had a role in the induction of migration and invasion in cervical cancer cells. Moreover, the expression level of MKL1, as the targeting gene of miR206, was decreased after HOTAIR inhibition in HeLa cells. Agreement with it, Highly level of MKL1 correlation with HOTAIR is validated in cervical cancer tissues. Importantly, HOTAIR is observed to participate in the silencing of miR206 expression. Interestingly, HOTAIR inhibition could also accelerate the expression of MKL1 in cytoplasm. What is more, MKL1 can activate the transcription of HOTAIR through binding the CArG box in the promoter of HOTAIR.ConclusionThese elucidates that the phenotypic effects of migration and invasion observed after HOTAIR inhibition, at least in part, through the regulation of MKL1 via inhibition of miR206 expression in HeLa cells. These data indicate the existence of a positive feedback loop between HOTAIR and MKL1. Together, these findings suggest that MKL1 is an important player in the functions of HOTAIR in the migration and invasion of cancer cells.

Paracrine and epigenetic control of CAF-induced metastasis: the role of HOTAIR stimulated by TGF-\xdf1 secretion

BackgroundThe communication between carcinoma associated fibroblasts (CAFs) and cancer cells facilitate tumor metastasis. In this study, we further underlying the epigenetic mechanisms of CAFs feed the cancer cells and the molecular mediators involved in these processes.MethodsMCF-7 and MDA-MB-231 cells were treated with CAFs culture conditioned medium, respectively. Cytokine antibody array, enzyme-linked immunosorbent assay, western blotting and immunofluorescence were used to identify the key chemokines. Chromatin immunoprecipitation and luciferase reporter assay were performed to explore the transactivation of target LncRNA by CAFs. A series of in vitro assays was performed with RNAi-mediated knockdown to elucidate the function of LncRNA. An orthotopic mouse model of MDA-MB-231 was conducted to confirm the mechanism in vivo.ResultsHere we reported that TGF-β1 was top one highest level of cytokine secreted by CAFs as revealed by cytokine antibody array. Paracrine TGF-β1 was essential for CAFs induced EMT and metastasis in breast cancer cells, which is a crucial mediator of the interaction between stromal and cancer cells. CAF-CM significantly enhanced the HOTAIR expression to promote EMT, whereas treatment with small-molecule inhibitors of TGF-β1 attenuated the activation of HOTAIR. Most importantly, SMAD2/3/4 directly bound the promoter site of HOTAIR, located between nucleotides -386 and -398, -440 and -452, suggesting that HOTAIR was a directly transcriptional target of SMAD2/3/4. Additionally, CAFs mediated EMT by targeting CDK5 signaling through H3K27 tri-methylation. Depletion of HOTAIR inhibited CAFs-induced tumor growth and lung metastasis in MDA-MB-231 orthotopic animal model.ConclusionsOur findings demonstrated that CAFs promoted the metastatic activity of breast cancer cells by activating the transcription of HOTAIR via TGF-β1 secretion, supporting the pursuit of the TGF-β1/HOTAIR axis as a target in breast cancer treatment.

Histone methylase MLL1 coordinates with HIF and regulate lncRNA HOTAIR expression under hypoxia

Hypoxia signaling plays a critical role in tumor growth, angiogenesis, metastasis cancer, and aging. Under hypoxia, hypoxia-inducible factors (HIFs) are stabilized and they coordinate the process of hypoxia-induced gene expression and cell signaling leading to increased tumor growth. Recent studies indicate that non-coding RNAs which are closely associated with cancer are abnormally expressed under hypoxia. Here, we have investigated the transcriptional regulation of a cancer associated long non-coding RNA (lncRNA), HOTAIR, under hypoxic conditions. Our studies demonstrate that HOTAIR expression is upregulated under hypoxia in colon cancer and several other types of cancer cells. HOTAIR transcription is regulated by HIF1α which binds to the hypoxia response elements (HRE) present in the HOTAIR promoter under hypoxia. HIF1α knockdown results in decreased HOTAIR expression under hypoxia. Along with HIF1α, histone methylases MLL1 and histone acetylase p300 are enriched at the HOTAIR promoter under hypoxia. The levels of H3K4-trimethylation and histone acetylation are also enriched at the HOTAIR promoter. Furthermore, knockdown of MLL1 downregulated the hypoxia-induced HOTAIR expression, indicating key roles of MLL1 in hypoxia-induced HOTAIR expression. Overall, our studies demonstrate that histone methyl-transferase MLL1 coordinates with HIF1α and histone acetyltransferase p300 and regulate hypoxia-induced HOTAIR expression. The hypoxia-induced upregulation of HOTAIR expression may contribute to its roles in tumorigenesis.

Thymic stromal lymphopoietin-induced HOTAIR activation promotes endothelial cell proliferation and migration in atherosclerosis.

Endothelial cells’ (EC) injury is a major step for the pathological progression of atherosclerosis. Recent study demonstrated that thymic stromal lymphopoietin (TSLP) exerts a protective role in atherosclerosis. However, the effect of TSLP and the exact molecular mechanism involved in EC remains unknown. In the present study, we found that long noncoding RNA (lncRNA) HOTAIR was much lower in EC from atherosclerotic plaque. Functional assays showed that HOTAIR facilitated cell proliferation and migration, and suppressed apoptosis in EC. Moreover, we demonstrated that TSLP functions upstream of HOTAIR. We found that serum level of TSLP was decreased in atherosclerosis patients and serum TSLP level positively correlated with HOTAIR expression in EC. Further investigation demonstrated that TSLP activated HOTAIR transcription through PI3K/AKT-IRF1 pathway and then regulates the EC proliferation and migration. TSLP-HOTAIR axis also plays a protective role in low-density lipoprotein (ox-LDL)-induced EC injury. Taken together, TSLP-HOTAIR may be a potential therapy for EC dysfunction in atherosclerosis.

Transcription of HOTAIR is regulated by RhoC-MRTF-A-SRF signaling pathway in human breast cancer cells

HOTAIR is a long non-coding RNA highly expressed in cancer tissues and is a negative prognostic factor, whereas the mechanism by which HOTAIR expression is upregulated in cancers remains elusive. In the present study, the regulation of HOTAIR transcription was investigated in breast cancer cells MCF7 and T47D. We found that, when the RhoC-ROCK signaling was disturbed by specific siRNAs or chemical inhibitors, the expression of HOTAIR would be down-regulated. Further, MRTF-A and SRF were found to affect HOTAIR expression. HOTAIR promoter activity was demonstrated to be regulated by the RhoC-MRTF-A-SRF signaling in a CArG-box-dependent manner. Moreover, MRTF-A was identified to physically interact with HOTAIR promoter, and RNA polymerase II association on HOTAIR promoter was enhanced by MRTF-A overexpression. Taken together, our results suggest that HOTAIR is regulated by the RhoC-MRTF-A-SRF signaling pathway in breast cancer cells.

Abstract 996: STAT3 modulates HOTAIR transcription to influence HNSCC growth in vitro and in vivo

Abstract Background Squamous cell carcinoma is the most common cancer type of head and neck (HNSCC) with poor prognosis. Signal transducer and activator of transcription 3 (STAT3) activation is involved in HNSCC carcinogenesis as a transcript factor. A new class of transcripts, long noncoding RNAs (lncRNAs), has been recently found to be pervasively transcribed in the genome. HOTAIR, lncRNA Hox transcript antisense intergenic RNA, has been characterized as a novel hall marker to predict poor prognosis in HNSCC. HOTAIR regulates downstream target gene transcription by recruiting polycomb repressive complex 2 (PRC2) to the cell nucleus and triggers triple methylation of H3K27. Methods RNA sequencing, qPCR and CHIP assay were used to determine HOTAIR is a down-stream gene of STAT3. MTT and western blot were employed to examine the regulatory mechanism between STAT3 and HOTAIR in HNSCC cancers in vitro. Additionally, a cell derived xenograft tumor model was used to further validate the anti tumor effect of targeting STAT3/HOTAIR axis in vivo. Results STAT3 depleted HNSCC cell showed decreased HOTAIR expression by qPCR assay. CHIP assay indicated STAT3 bind to the promoter region of HOTAIR encoding gene. Combined inhibition of STAT3 and HOTAIR significantly inhibited cell proliferation, sensitive to cisplatin in HNSCC. Up-regulating HOTAIR partially compensated anti-tumor effect of targeting STAT3 in HNSCC. Conclusion Our data suggested that HOTAIR overexpression is depended on constitutive STAT3 activation in HNSCC and targeting STAT3/HOTAIR axis showed significant therapeutic potential in vitro and in vivo. Citation Format: Xuan Zhou. STAT3 modulates HOTAIR transcription to influence HNSCC growth in vitro and in vivo. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 996.

Abstract 1980: Long-range regulation of HOTAIR identifies novel biomarkers of breast cancer outcome and suggests a role in genome instability

Abstract Long-range regulators of gene expression are emerging as promising new biomarkers and therapeutic targets for human diseases including cancer. As current breast cancer biomarkers have limited power for predicting disease progression and response to therapy, we have explored the potential of long-range regulators of non-coding RNAs to be useful in the prognostication of breast cancer. HOTAIR is a long non-coding RNA that is overexpressed, promotes metastasis, and is predictive of poor prognosis in breast cancer. Here we describe a long-range transcriptional enhancer of the HOTAIR gene that binds several hormone receptors and associated transcription factors, interacts with the HOTAIR promoter and augments HOTAIR transcription. This enhancer is dependent on FOXA1 and FOXM1 transcription factors and functionally interacts with a novel alternate HOTAIR promoter. Analysis of breast cancer gene expression data indicates that HOTAIR is co-expressed with FOXA1 and FOXM1 in HER2-enriched tumours, and these factors enhance the prognostic power of HOTAIR in this subtype of breast cancer. The combination of HOTAIR and FOXM1 also enables better predictions of response to endocrine therapy for ER+ breast cancer. FOXM1 is a member of the recently described chromosome instability module and consistent with this, the expression of HOTAIR and FOXM1 is associated with increased frequency of copy number alterations and somatic non-synonymous mutations. Our study corroborates the importance of enhancers in breast cancer, elucidates the transcriptional regulation of HOTAIR, suggests HOTAIR as a novel biomarker of patient response to endocrine therapy, and implicates HOTAIR in chromosome instability. Citation Format: Michael J. Milevskiy, Fares Al-Ejeh, Jodi M. Saunus, Korinne S. Northwood, Amy E. McCart-Reed, Eloise Dray, Kenneth Nephew, Peter J. Bailey, Joshua A. Betts, Andrew Stone, Julia M W Gee, Annette M. Shewan, Juliet D. French, Stacey L. Edwards, Susan J. Clark, Sunil R. Lakhani, Melissa A. Brown. Long-range regulation of HOTAIR identifies novel biomarkers of breast cancer outcome and suggests a role in genome instability. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1980.

Abstract 3551: Non-coding RNA HOTAIR connects DNA damage signaling to NF-κB activation in cisplatin resistant ovarian cancer

Abstract The Polycomb Repressive Complex 2 (PRC2) has been implicated in cancer and a role for PRC2 during DNA damage response (DDR) has recently been reported. To examine changes in gene expression with DDR in cisplatin (cddp)-resistant ovarian cancer (OC), we performed whole transcriptome RNA-seq analysis of isogenic cddp-sensitive and -resistant OC cell lines (A2780 and A2780-cp). Differential expression of PRC components (SUZ12, EZH1, SIRT1, PHC1 &2) (P<0.05), NF-κB pathway members (NCAM, ABCB9, RAGE, IL4R, IL6R, BCL2L11) (P<0.05), and long non-coding RNAs (lncRNAs) known to associate with PRC2 (P<0.05), including Hox transcript antisense intergenic RNA or HOTAIR, was observed. In tumors from patients with high grade serous OC at diagnosis, basal expression of HOTAIR was greater (P<0.01) compared to normal ovarian surface epithelium and marked overexpression of HOTAIR was observed in tumors obtained from patients who had developed platinum-resistant OC. Ablation of HOTAIR using dsiRNA resensitized A2780-cp to cddp, while ectopic over-expression of HOTAIR increased (P<0.05) A2780 cell survival after cddp treatment (3-fold vs. control). To further examine HOTAIR regulation, we conducted a promoter analysis using bioinformatics tools and luciferase assays. We identified a putative p65-NF-κB binding site (906-GGGACACCCC-915) 906 bp upstream of the HOTAIR transcription start site. Treatment of A2780 cells with the NF-κB activator TNF-α induced HOTAIR (16-fold vs. control) and NF-κB enrichment (3-fold assessed by ChIP assays) at the HOTAIR promoter. Furthermore, in A2780-cp compared to A2780, total Iκ-Bα levels were reduced (P<0.05) and nuclear p65 levels were increased, indicating that endogenous activation of NF-κB contributes to cddp resistance and DDR. Consistent with this observation, cddp treatment (20μM for 0-24hrs) of A2780 cells increased (P<0.05) HOTAIR expression by 5- and 16-fold at 8 and 24 hrs and decreased (P<0.05) Iκ-Bα protein levels at similar time points. Furthermore, inhibiting NF-κB by either gliotoxin (5μM) or Bay-11 (3μM) completely abolished cddp-induced HOTAIR expression in A2780 cells, demonstrating that NF-κB is a HOTAIR transcriptional activator during cddp-induced DDR. Importantly, EZH2 and histone H3 lysine-27 trimethylation (H3K27me3) levels were enriched (6- and 17-fold) in the Iκ-Bα promoter at 24 and 48 hours post cddp treatment, and HOTAIR depletion using dsiRNA reduced the observed EZH2-H3K27me3 enrichment at the Iκ-Bα promoter, demonstrating that HOTAIR recruits PRC2 complex to the Iκ-Bα promoter to prolong NF-κB activation during cddp-induced genotoxic stress. Mouse xenograft studies with A2780 cells overexpressing HOTAIR are ongoing. The results of this study support a role for HOTAIR as a positive regulator of the NF-κB pathway and PRC2 during cisplatin-induced DNA damage. We further suggest that HOTAIR may serve as a therapeutic target in cisplatin-resistant OC. Citation Format: Ali R. Ozes, Dave F. Miller, Yunlong Liu, Kenneth P. Nephew. Non-coding RNA HOTAIR connects DNA damage signaling to NF-κB activation in cisplatin resistant ovarian cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3551. doi:10.1158/1538-7445.AM2014-3551

Decoding Drug Abuse in Noncoding RNA?

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