LncRNA HOTAIR promotes human liver cancer stem cell malignant growth through downregulation of SETD2

Targeting LncRNA HOTAIR suppresses cancer stemness and metastasis in oral carcinomas stem cells through modulation of EMT

Increasing evidence indicates that long non-coding RNAs (lncRNAs) regulate diverse cellular processes, such as cell growth, apoptosis and tumorigenesis. However, the functional roles of lncRNAs and mechanistic analysis of their interplays with oncogenic pathways in oral cancer remain largely unknown. In the current study, we examined the significance of lncRNA HOTAIR (HOX transcript antisense RNA) in tumor progression of oral squamous cell carcinomas (OSCC). We found the expression of HOTAIR was upregulated in tumor tissues, especially in the metastatic samples. And it was also observed in metastatic OSCC cell lines. Silence of HOTAIR in oral carcinomas stem cells (OCSC) significantly inhibited their cancer stemness, invasiveness and tumourigenicity in xenotransplantation models. By contrast, overexpression of HOTAIR in OSCC enhanced their metastatic potential and epithelial-mesenchymal transition (EMT) characteristics. And we showed that the expression of HOTAIR was positively related to mesenchymal markers and inversely correlated with epithelial marker in clinical samples. Moreover, Kaplan-Meier survival analysis suggested that high level of HOTAIR was a strong predictor of poor survival in OSCC patients. Collectively, our data demonstrated that HOTAIR-mediated cancer stemness and metastasis are associated with the regulation of EMT and HOTAIR may serve as a therapeutic target in OSCC.

Knockdown of Hotair suppresses proliferation and cell cycle progression in hepatocellular carcinoma cell by downregulating CCND1 expression

The long noncoding RNA, homeobox transcript antisense RNA (Hotair), has been demonstrated to have an important role in regulating various biological processes in various cancers, including hepatocellular carcinoma (HCC). However, the importance of Hotair in HCC proliferation and cell cycle progression remains to be elucidated. In the present study, knockdown of HOTAIR expression by RNA interference inhibited cell proliferation and induced G0/G1 cell cycle arrest in Huh7 hepatocellular carcinoma cells. In addition, the expression levels of CCND1 mRNA and its cyclin D1 protein product were reduced in Huh7 cells following knockdown of HOTAIR. Knockdown of HOTAIR reduced the expression of phosphorylated signal transducer and activator of transcription 3 (STAT3) and HOTAIR knockdown combined with STAT3 inhibition led to an additional decrease in cyclin D1 expression. The present study suggested that Hotair may have a critical role in the proliferation of HCC by regulating cell cycle, STAT3 activity and cyclin D1 expression. Therefore, Hotair may be a novel potential therapeutic target for HCC treatment.

Quantitative assessment of lncRNA HOTAIR polymorphisms and cancer risk in Chinese population: a meta-analysis based on 26,810 subjects

As a well-known long non-coding RNA, HOTAIR has been demonstrated to be involved in carcinogenesis and progression of various human cancers. Previous studies have investigated the potential association between HOTAIR polymorphisms and cancer risk in Chinese population. However, the results remain conflicting. Therefore, for the first time, we conducted a meta-analysis to derive a more precise estimation of these associations for Chinese. PubMed, Embase, CNKI and Wanfang databases were systematically searched. Odds ratios with 95% confidence intervals were applied to assess the association between rs920778, rs4759314, rs7958904, rs874945 and rs1899663 polymorphisms of HOTAIR and cancer susceptibility. Heterogeneity, sensitivity analysis and publication bias were conducted to measure the robustness of our findings. A total of 21 eligible studies comprising 12,278 cases and 14,532 controls were analyzed. The pooled data showed that rs920778 polymorphism was significantly associated with an increased cancer risk in all five genetic models in Chinese population. As for rs4759314 and rs874945 polymorphisms, similarly increased risks were found in specific genetic models and stratified groups. However, significant decreases in cancer risk were observed for rs7958904 in the total population, as well as in subgroup analyses. In addition, lack of association was detected between rs1899663 polymorphism and cancer susceptibility. In summary, our meta-analysis implicates possible relationship between HOTAIR polymorphisms and cancer risk in Chinese population.

Role of the long non-coding RNA HOTAIR in hepatocellular carcinoma

A number of recent studies have focused on the association between long non-coding RNAs (lncRNAs) and cancer. HOX transcript antisense RNA (HOTAIR), an lncRNA that functions as a transcriptional modulator, has been implicated in various fundamental biological activities. HOTAIR mediates the trimethylation of histone H3 at lysine 27 and the demethylation of histone H3 dimethyl Lys4 by recruiting the polycomb repressive complex 2 and the lysine-specific demethylase 1/co-repressor of RE1-silencing transcription factor (coREST)/REST complex to the target gene promoters, which leads to gene silencing. Overexpression of HOTAIR in hepatocellular carcinoma (HCC) is strongly associated with an unfavorable prognosis for patients with HCC. HOTAIR promotes the carcinogenic activity of HCC cells through the suppression of RNA binding motif protein 38, triggering the epithelial-mesenchymal transition, and by interacting with microRNAs that act as tumor suppressors. In the present review, the role of the lncRNA HOTAIR in HCC is examined. The potential use of HOTAIR as a biomarker to achieve more accurate prognostic predictions and as an effective therapeutic target for HCC is then discussed.

The long noncoding RNA HOTAIR activates the Hippo pathway by directly binding to SAV1 in renal cell carcinoma

The long noncoding RNA HOTAIR promotes the development and progression of several tumors. Here, the clinical significance and role of HOTAIR in renal cell carcinoma (RCC) tumorigenesis were explored. The results showed that increased expression of HOTAIR predicted a poor prognosis of RCC after surgery. HOTAIR promoted RCC cell proliferation and growth in vitro and in vivo. The expressions of HOTAIR and Salvador homolog 1 (SAV1) were inversely correlated in clinical RCC samples. HOTAIR downregulated SAV1 by directly binding to the SAV1 protein and enhanced histone H3K27 methylation. Loss of function of SAV1 activated the Hippo pathway. HOTAIR could be a potential therapeutic target in RCC.

Long Non-Coding RNAs: Key Regulators of Epithelial-Mesenchymal Transition, Tumour Drug Resistance and Cancer Stem Cells

Epithelial mesenchymal transition (EMT), the adoption by epithelial cells of a mesenchymal-like phenotype, is a process co-opted by carcinoma cells in order to initiate invasion and metastasis. In addition, it is becoming clear that is instrumental to both the development of drug resistance by tumour cells and in the generation and maintenance of cancer stem cells. EMT is thus a pivotal process during tumour progression and poses a major barrier to the successful treatment of cancer. Non-coding RNAs (ncRNA) often utilize epigenetic programs to regulate both gene expression and chromatin structure. One type of ncRNA, called long non-coding RNAs (lncRNAs), has become increasingly recognized as being both highly dysregulated in cancer and to play a variety of different roles in tumourigenesis. Indeed, over the last few years, lncRNAs have rapidly emerged as key regulators of EMT in cancer. In this review, we discuss the lncRNAs that have been associated with the EMT process in cancer and the variety of molecular mechanisms and signalling pathways through which they regulate EMT, and finally discuss how these EMT-regulating lncRNAs impact on both anti-cancer drug resistance and the cancer stem cell phenotype.

Emerging role of mutations in epigenetic regulators including MLL2 derived from The Cancer Genome Atlas for cervical cancer

BACKGROUND

Cervical cancer is the second most common cause of cancer deaths in women worldwide. The aim of this study is to exploit novel pathogenic genes in cervical carcinogenesis.

METHOD

The somatic mutations from 194 patients with cervical cancer were obtained from the Cancer Genome Atlas (TCGA) publically accessible exome-sequencing database. We investigated mutated gene enrichment in the 12 cancer core pathways and predicted possible post-translational modifications. Additionally, we predicted the impact of mutations by scores quantifying the deleterious effects of the mutations. We also examined the immunogenicity of the mutations based on the mutant peptides' strong binding with major histocompatibility complex class I molecules (MHC-I). The Kaplan-Meier method was used for the survival analysis.

RESULTS

We observed that the chromatin modification pathway was significantly mutated across all clinical stages. Among the mutated genes involved in this pathway, we observed that the histone modification regulators were primarily mutated. Interestingly, of the 197 mutations in the 26 epigenetic regulators in this pathway, 25 missense mutations in 13 genes were predicted in or around the phosphorylation sites. Only mutations in the histone methyltransferase MLL2 exhibited poor survival. Compared to other mutations in MLL2 mutant patients, we noticed that the mutational scores prioritized mutations in MLL2, which indicates that it is more likely to have deleterious effects to the human genome. Around half of all of the mutations were found to bind strongly to MHC-I, suggesting that patients are likely to benefit from immunotherapy.

CONCLUSIONS

Our results highlight the emerging role of mutations in epigenetic regulators, particularly MLL2, in cervical carcinogenesis, which suggests a potential disruption of histone modifications. These data have implications for further investigation of the mechanism of epigenetic dysregulation and for treatment of cervical cancer.

Shaping the cellular landscape with Set2/SETD2 methylation

Chromatin structure is a major barrier to gene transcription that must be disrupted and re-set during each round of transcription. Central to this process is the Set2/SETD2 methyltransferase that mediates co-transcriptional methylation to histone H3 at lysine 36 (H3K36me). Studies reveal that H3K36me not only prevents inappropriate transcriptional initiation from arising within gene bodies, but that it has other conserved functions that include the repair of damaged DNA and regulation of pre-mRNA splicing. Consistent with the importance of Set2/SETD2 in chromatin biology, mutations of SETD2, or mutations at or near H3K36 in H3.3, have recently been found to underlie cancer development. This review will summarize the latest insights into the functions of Set2/SETD2 in genome regulation and cancer development.

Long non-coding RNA HOTAIR regulates proliferation and invasion via activating Notch signalling pathway in retinoblastoma

Retinoblastoma is the most frequently occurring tumour in the eyes in early childhood. Novel targets that are important for the diagnosis or treatment of retinoblastoma could be valuable in increasing the survival rate of patients affected by this disease. Long non-coding RNAs (lncRNAs) are a recently discovered type of RNAs with no proteincoding function; yet it has become increasingly clear that lncRNAs are responsible for important gene regulatory functions in various diseases. In this study, the expression of lncRNA HOTAIR was measured by qRT-PCR, and HOTAIR expression was found to be significantly upregulated in human retinoblastomas tissues as compared with that in paracancerous tissues. Knockdown of HOTAIR restricted the proliferation and invasion of the more invasive retinoblastoma Y79 cells, and led to G0/G1 arrest, possibly through inhibiting phospho-RB1, RB1 and CCNE. Furthermore, we found that the Notch signalling pathway was activated abnormally in retinoblastoma cell lines, while knockdown of HOTAIR attenuated the endogenous Notch signalling pathway in vitro and in vivo. In addition, knockdown of HOTAIR could inhibit the tumour progression in a xenograft model of retinoblastoma. In summary, our findings indicate that HOTAIR may play important roles in retinoblastoma progression via Notch pathway. HOTAIR has the potential to enhance the development of novel targeted diagnostic and therapeutic approaches for retinoblastoma.

Uncovering the roles of long non-coding RNAs in cancer stem cells

Cancer has been a major public health problem that has threatened human life worldwide throughout history. The main causes that contribute to the poor prognosis of cancer are metastasis and recurrence. Cancer stem cells are a group of tumor cells that possess self-renewal and differentiation ability, which is a vital cause of cancer metastasis and recurrence. Long non-coding RNAs refer to a class of RNAs that are longer than 200 nt and have no potential to code proteins, some of which can be specifically expressed in different tissues and different tumors. Long non-coding RNAs have great biological significance in the occurrence and progression of cancers. However, how long non-coding RNAs interact with cancer stem cells and then affect cancer metastasis and recurrence is not yet clear. Therefore, this review aims to summarize recent studies that focus on how long non-coding RNAs impact tumor occurrence and progression by affecting cancer stem cell self-renewal and differentiation in liver cancer, prostate cancer, breast cancer, and glioma.

Identification of the long non‑coding RNA LET as a novel tumor suppressor in gastric cancer

Long non-coding RNAs (lncRNAs) have emerged recently as important factors in regulating fundamental biological processes. Alterations in the expression and function of lncRNAs have been observed to promote tumor formation, progression and metastasis. Although downregulation of the expression levels of LET lncRNA in several tumors has been reported, its role in gastric cancer remains unknown. The aim of the present study was to investigate the expression and function of LET in gastric cancer development. The expression levels of LET in 37 pairs of gastric cancer and adjacent non‑tumor tissues were detected by reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR). In addition, LET expression in gastric cancer cell lines was analyzed by RT‑qPCR assay analysis. Furthermore, the impact of LET on cell proliferation, migration and apoptosis were detected using the cell counting kit‑8, wound scratch and ELISA assays, respectively. The results demonstrated that the expression level of LET was downregulated in gastric cancer tissues and cell lines (SGC‑7901 and MGC‑803) compared with normal tissues and a normal human gastric epithelial cell line (GES‑1). Restoration of LET expression using a synthesized recombinant overexpression vector transfected into SGC‑7901 and MGC‑803 cells, significantly inhibited cell proliferation and migration, and promoted cell apoptosis in vitro. The present study is the first to demonstrate that LET may function as a tumor suppressor in gastric cancer. The results indicate that LET may be a promising biomarker and/or a therapeutic target for gastric cancer.

Analysis of cancer-related lncRNAs using gene ontology and KEGG pathways

BACKGROUND

Cancer is a disease that involves abnormal cell growth and can invade or metastasize to other tissues. It is known that several factors are related to its initiation, proliferation, and invasiveness. Recently, it has been reported that long non-coding RNAs (lncRNAs) can participate in specific functional pathways and further regulate the biological function of cancer cells. Studies on lncRNAs are therefore helpful for uncovering the underlying mechanisms of cancer biological processes.

METHODS

We investigated cancer-related lncRNAs using gene ontology (GO) terms and KEGG pathway enrichment scores of neighboring genes that are co-expressed with the lncRNAs by extracting important GO terms and KEGG pathways that can help us identify cancer-related lncRNAs. The enrichment theory of GO terms and KEGG pathways was adopted to encode each lncRNA. Then, feature selection methods were employed to analyze these features and obtain the key GO terms and KEGG pathways.

RESULTS

The analysis indicated that the extracted GO terms and KEGG pathways are closely related to several cancer associated processes, such as hormone associated pathways, energy associated pathways, and ribosome associated pathways. And they can accurately predict cancer-related lncRNAs.

CONCLUSIONS

This study provided novel insight of how lncRNAs may affect tumorigenesis and which pathways may play important roles during it. These results could help understanding the biological mechanisms of lncRNAs and treating cancer.

LncRNA GAS5 contributes to lymphatic metastasis in colorectal cancer

Colorectal cancer (CRC) ranks the third most common type of cancer worldwide. However, the detailed molecular mechanisms underlying these processes are poorly understood. Recent studies have shown that lncRNAs play important roles in carcinogenesis and progression of CRC. The lncRNA growth arrest special 5 (GAS5), was previously identified to be down-regulated and functions as a tumor suppressor gene in many kinds of cancers. In current two-stage, case-control study, we systematically evaluated the potential role of lncRNA GAS5 and its genetic variation rs145204276 in the development and metastasis process of CRC in a Chinese population. We found the allele del of rs145204276 was significantly associated with 21% decreased risk of CRC (OR=0.79; 95% CI=0.70-0.89; P value = 5.21×10-5). Compared with the genotype ins/ins, both the genotype ins/del (OR=0.78; 95% CI=0.68-0.91) and del/del (OR=0.64; 95% CI=0.49-0.84) showed decreased susceptibility. For both in colon and rectum cancers, the associations kept statistically significant (OR=O.78 and 0.80, while P value = 4.56×10-4, and 3.80×10-3, respectively). The results also showed that the carriers of allele del are less likely to get lymph node metastasis (OR=0.80; 95% CI=0.68-0.95; P value = 0.010). Taken together, our findings provided strong evidence for the hypothesis that GAS5 rs145204276 were significantly associated with the susceptibility and progression of CRC.

Inflammatory cytokine IL6 cooperates with CUDR to aggravate hepatocyte-like stem cells malignant transformation through NF-κB signaling

Inflammatory cytokines and lncRNAs are closely associated with tumorigenesis. Herein, we reveal inflammatory cytokines IL6 cooperates with long noncoding RNA CUDR to trigger the malignant transformation of human embryonic stem cells-derived hepatocyte-like stem cells. Mechanistically, IL6 cooperates with CUDR to cause MELLT3 to interact with SUV39h1 mRNA3′UTR and promote SUV39h1 expression. Moreover, the excessive SUV39h1 also increases tri-methylation of histone H3 on nineth lysine (H3K9me3). Intriguingly, under inflammatory conditions, H3K9me3 promotes the excessive expression and phosphorylation of NF-κB, and in turn, phorsphorylated NF-κB promotes the expression and phosphorylation of Stat3. Furthermore, that the phosphorylated Stat3 loads onto the promoter region of miRs and lncRNAs. Ultimately, the abnormal expression of miRs and lncRNAs increased telomerase activity, telomere length and microsatellite instability (MSI), leading to malignant transformation of hepatocyte-like stem cells.

Elevated HOTAIR expression associated with cisplatin resistance in non-small cell lung cancer patients

BACKGROUND

This study investigated the mechanism of drug resistance in non-small cell lung cancer (NSCLC) patients. We specifically studied whether long noncoding RNAs influence drug resistance in NSCLC to discover new therapeutic targets to increase the survival rate of drug-resistant NSCLC patients.

METHODS

Tissue samples were collected from NSCLC patients, and total RNA was isolated for assessment of HOTAIR expression and drug resistance status. MTT assays, tumor sphere formation assays, and western blot were performed to cytologically determine the relationship between HOTAIR expression and cisplatin resistance, as well as to elucidate the potential molecular mechanism involved.

RESULTS

HOTAIR expression in tissues of drug-resistant NSCLC patients was higher than that of non-drug-resistant patients. HOTAIR expression was elevated in cisplatin-resistant cell strains (A549/CDDP), and reducing HOTAIR expression increased the sensitivity of A549/CDDP cells to cisplatin. In addition, overexpression of HOTAIR in A549 cells increased resistance to cisplatin. Tumor sphere formation assays showed that the volume of spheres formed by cell strains expressing elevated levels of HOTAIR was greater than that of cell strains with low expression. Western blot experiments showed that elevated expression of HOTAIR upregulated tumor stem cell-related biomarkers and HOTAIR expression was directly related to Klf4 expression.

CONCLUSIONS

Elevated HOTAIR expression is associated with drug resistance in NSCLC patients and is related to Klf4 upregulation, providing a new therapeutic target for drug-resistant NSCLC patients.

HULC cooperates with MALAT1 to aggravate liver cancer stem cells growth through telomere repeat-binding factor 2

The dysregulation of lncRNAs has increasingly been linked to many human diseases, especially in cancers. Our results demonstrate HULC, MALAT1 and TRF2 are highly expressed in human hepatocellular carcinoma tissues, and HULC plus MALAT1 overexpression drastically promotes the growth of liver cancer stem cells. Mechanistically, both HULC and MALAT1 overexpression enhanced RNA polII, P300, CREPT to load on the promoter region of telomere repeat-binding factor 2(TRF2), triggering the overexpression, phosphorylation and SUMOylation of TRF2. Strikingly, the excessive TRF2 interacts with HULC or MALAT1 to form the complex that loads on the telomeric region, replacing the CST/AAF and recruiting POT1, pPOT1, ExoI, SNM1B, HP1 α. Accordingly, the telomere is greatly protected and enlonged. Furthermore, the excessive HULC plus MALAT1 reduced the methylation of the TERC promoter dependent on TRF2, increasing the TERC expression that causes the increase of interplay between TRET and TERC. Ultimately, the interaction between RFC and PCNA or between CDK2 and CyclinE, the telomerase activity and the microsatellite instability (MSI) are significantly increased in the liver cancer stem cells. Our demonstrations suggest that haploinsufficiency of HULC/MALAT1 plays an important role in malignant growth of liver cancer stem cell.

Double mutant P53 (N340Q/L344R) promotes hepatocarcinogenesis through upregulation of Pim1 mediated by PKM2 and LncRNA CUDR

P53 is frequently mutated in human tumors as a novel gain-of-function to promote tumor development. Although dimeric (M340Q/L344R) influences on tetramerisation on site-specific post-translational modifications of p53, it is not clear how dimeric (M340Q/L344R) plays a role during hepatocarcinogenesis. Herein, we reveal that P53 (N340Q/L344R) promotes hepatocarcinogenesis through upregulation of PKM2. Mechanistically, P53 (N340Q/L344R) forms complex with CUDR and the complex binds to the promoter regions of PKM2 which enhances the expression, phosphorylation of PKM2 and its polymer formation. Thereby, the polymer PKM2 (tetramer) binds to the eleventh threonine on histone H3 that increases the phosphorylation of the eleventh threonine on histone H3 (pH3T11). Furthermore, pH3T11 blocks HDAC3 binding to H3K9Ac that prevents H3K9Ac from deacetylation and stabilizes the H3K9Ac modification. On the other hand, it also decreased tri-methylation of histone H3 on the ninth lysine (H3K9me3) and increases one methylation of histone H3 on the ninth lysine (H3K9me1). Moreover, the combination of H3K9me1 and HP1 α forms more H3K9me3-HP1α complex which binds to the promoter region of Pim1, enhancing the expression of Pim1 that enhances the expression of TERT, oncogenic lncRNA HOTAIR and reduces the TERRA expression. Ultimately, P53 (N340Q/L344R) accerlerates the growth of liver cancer cells Hep3B by activating telomerase and prolonging telomere through the cascade of P53 (N340Q/L344R)-CUDR-PKM2-pH3T11- (H3K9me1-HP1α)-Pim1- (TERT-HOTAIR-TERRA). Understanding the novel functions of P53 (N340Q/L344R) will help in the development of new liver cancer therapeutic approaches that may be useful in a broad range of cancer types.

Long Noncoding RNA ROR Regulates Proliferation, Invasion, and Stemness of Gastric Cancer Stem Cell

Gastric cancer remains an incurable malignance and the second leading cause of cancer death globally. Recent progress in gastric cancer research has demonstrated the crucial roles of cancer stem cells (CSCs) in the development, metastasis, and drug resistance of this disease. Various studies have highlighted the role of long noncoding RNAs (lncRNAs) in the pathogenesis of gastric cancer. In this study, through fluorescence-activated cell sorting, we isolated gastric CSCs (GCSCs) from MKN-45 cells and demonstrated for the first time that lncRNA ROR was highly expressed in CD133⁺ GCSCs. Overexpression of lncRNA ROR significantly increased, but knockdown of lncRNA ROR inhibited the proliferation and invasion of GCSCs. Most importantly, lncRNA ROR led to upregulation of several key stemness transcriptional factors, such as OCT4, SOX2, and NANOG, as well as CD133 GCSC. Our data demonstrated that lncRNA ROR was associated with core stemness transcriptional factors and the pluripotent state of GCSCs. These results further improved our understanding of the functional cross talking network during development of GCSCs and may provide novel target for the diagnostics and therapeutics of gastric cancer.

Interplay of genetic and epigenetic alterations in hepatocellular carcinoma

Genetic and epigenetic alterations play prominent roles in hepatocarcinogenesis and their appearance varies depending on etiological factors, race and tumor progression. Intriguingly, distinct patterns of these genetic and epigenetic mutations are coupled not only to affect each other, but to trigger different types of tumorigenesis. The patterns and frequencies of somatic variations vary depending on the nature of the surrounding chromatin. On the other hand, epigenetic alterations often induce genomic instability prone to mutation. Therefore, genetic mutations and epigenetic alterations in hepatocellular carcinoma appear to be inseparable factors that accelerate tumorigenesis synergistically. We have summarized recent findings on genetic and epigenetic modifications, their influences on each other's alterations and putative roles in liver tumorigenesis.

Long noncoding RNAs in digestive system cancers: Functional roles, molecular mechanisms, and clinical implications (Review)

Long noncoding RNAs (lncRNAs) are emerging as new players in various diseases including cancer. LncRNAs have been shown to play multifaceted roles in the development, progression, and metastasis of cancer. In this review, we highlight the lncRNAs that are critically involved in the pathogenesis of digestive system cancers (DSCs). We summarize the roles of the lncRNAs in DSCs and the underlying mechanisms responsible for their functions. The DSC-associated lncRNAs interact with a wide spectrum of molecules to regulate gene expression at transcriptional, post-transcriptional, and translational levels. We also provide new insights into the clinical significance of these lncRNAs, which are found to be closely associated with the aggressiveness of DSCs and could predict the prognosis of DSC patients. Moreover, lncRNAs have been suggested as promising therapeutic targets in DSCs. Therefore, better understanding of the functional roles of lncRNAs will provide new biomarkers for DSC diagnosis, prognosis, and therapy.

HuR-regulated lncRNA NEAT1 stability in tumorigenesis and progression of ovarian cancer

Long noncoding RNAs (lncRNAs) have recently emerged as pivotal regulators in governing fundamental biological processes, as well as in tumorigenesis. The nuclear paraspeckle assembly transcript 1 (NEAT1) is one of the most highly regulated lncRNAs in recent genomic datasets, however, its biological role and regulatory mechanism in ovarian cancer (OC) development and progression are poorly defined. In this study, we identified that NEAT1 was up-regulated in OC patients and cell lines, and its expression was associated with the FIGO stage and lymph node metastasis. Furthermore, the ectopic expression of NEAT1_1 in OVCAR-3 cell lines promoted cell proliferation and invasion, whereas knockdown of NEAT1_1 did the opposite. Furthermore, NEAT1_1 was stabilized by an RNA-binding protein HuR, but suppressed by miR-124-3p in OC cells. Accordingly, the increased HuR mRNA and decreased miR-124-3p levels were observed in OC patients. These results suggested that lncRNA NEAT1, whose expression was collaboratively controlled by HuR and miR-124-3p, could regulate ovarian carcinogenesis and may serve as a potential target for antineoplastic therapies.

Genetic variants of lncRNA HOTAIR contribute to the risk of osteosarcoma

Osteosarcoma (OS) is the most common primary malignant bone tumor in adolescents and young adults. However, the essential mechanisms underlying osteosarcomagenesis remain obscure. The HOTAIR, a well-known long noncoding RNA (lncRNA), is involved in pathogenesis and progress of multiple tumors. To reveal the potential role of lncRNA HOTAIR in OS carcinogenesis, we conducted a two-stage, case-control study among Chinese population with 900 OS cases and 900 controls to evaluated associations of its genetic variants with OS risk. We found that C allele of rs7958904 was associated with a significantly decreased OS risk when compared with G allele (OR: 0.77; 95% CI: 0.67-0.90; P = 6.77×10-4). Functional analyses on HOTAIR Expression showed that the expression level of HOTAIR in OS tissues was significantly higher than that in corresponding normal tissues, and subjects with the rs7958904 CC genotype had significantly lower HOTAIR RNA levels than those of other genotypes. This should be the first study to examine the association between HOTAIR variants and OS risk.

Long non-coding RNA regulation of liver cancer stem cell self-renewal offers new therapeutic targeting opportunities

Long non-coding RNAs (lncRNA) are critical regulators of gene expression, and can reprogram the transcriptome to modulate cellular processes involved in cellular growth and differentiation, and thereby contribute to tumorigenesis. In addition to effects on tumor cell growth, survival and cell signaling, lncRNA can modulate cancer stem cell (CSC) behavior, including the expression of pluripotency factors. The identification of lncRNA that are mechanistically linked to cancer stem cell self-renewal and differentiation, or aberrant signaling pathways associated with tumor growth or progression, offer new opportunities for therapeutic intervention.

Regulation of mismatch repair by histone code and posttranslational modifications in eukaryotic cells

DNA mismatch repair (MMR) protects genome integrity by correcting DNA replication-associated mispairs, modulating DNA damage-induced cell cycle checkpoints and regulating homeologous recombination. Loss of MMR function leads to cancer development. This review describes progress in understanding how MMR is carried out in the context of chromatin and how chromatin organization/compaction, epigenetic mechanisms and posttranslational modifications of MMR proteins influence and regulate MMR in eukaryotic cells.

Long noncoding RNAs as potential biomarkers in gastric cancer: Opportunities and challenges

Gastric cancer (GC) is a major threat to human health, and its prognosis is poor due to the lack of appropriate biomarkers. LncRNAs are a group of non-protein-coding RNAs that regulate gene expression at the transcriptional or posttranscriptional level. LncRNAs play essential roles in GC initiation and development in the same way as oncogenes or tumour suppressor genes. Recent investigations have revealed that lncRNAs are often aberrantly expressed in GC; are involved in cell proliferation, apoptosis, migration and invasion; and correlate with the malignant phenotype of GC. LncRNAs, especially the lncRNAs present in the blood and gastric juice, show potential value as biomarkers for the diagnosis of GC or for determining disease prognosis. However, there are still many challenges to be faced before lncRNAs can be used in clinical applications. In this review, we summarise lncRNAs as the potential biomarkers for GC and the current challenges associated with the clinical application.