Tumor hypoxia induces nuclear paraspeckle formation through HIF-2α dependent transcriptional activation of NEAT1 leading to cancer cell survival

Single-cell analysis reveals that GFAP+ dedifferentiated Schwann cells promote tumor progress in PNI-positive distal cholangiocarcinoma via lactate/HMGB1 axis

Distal cholangiocarcinoma (dCCA) is a highly lethal malignancy that accounts for approximately 40% of patients with primary cholangiocarcinoma. Remarkable cellular heterogeneity and perineural invasion (PNI) are two typical features of dCCA. Deciphering the complex interplay between neoplastic and neural cells is crucial for understanding the mechanisms propelling PNI-positive dCCA progression. Herein, we conduct single-cell RNA sequencing on 24,715 cells from two pairs of PNI-positive dCCA tumors and adjacent tissues, identifying eight unique cell types. Malignant cells exhibit significant inter- and intra-tumor heterogeneity. We delineate the compositional and functional phenotypes of five Schwann cell (SC) subsets in PNI-positive dCCA. Moreover, our analyses reveal two potential cell subtypes critical to forming PNI: NEAT1+ malignant cells characterized by hypoxic propensity and GFAP+ dedifferentiated SCs featuring hypermetabolism. Further bioinformatics uncover extensive cellular interactions between these two subpopulations. Functional experiments confirm that lactate in the hypoxic tumor microenvironment can induce GFAP-dedifferentiation in SCs, which promotes cancer cell invasion and progression through upregulating HMGB1. Taken together, our findings offer a thorough characterization of the transcriptional profile in PNI-positive dCCA and unveil potential therapeutic targets for dCCA PNI.

[Long non-coding RNAs, new therapeutic targets for the treatment of non-small cell lung cancers?]

A better understanding of the molecular mechanisms associated with the aggressiveness and high recurrence rate of non-small cell lung cancers is needed to identify new biomarkers and therapeutic targets to improve patient management. In this context, this review provides a non-exhaustive update on the emerging family of long non-coding RNAs, important regulators of gene expression, frequently deregulated in cancers and in response to hypoxia - an environmental factor that plays an important role in the development, aggressiveness and treatment resistance of these tumors.

Macrophage-Derived Exosomes Promoted the Development and Stemness of Inflammatory Bowel Disease-Related Colorectal Cancer via nuclear paraspeckle assembly transcript 1-Mediated miRNA-34a-5p/phosphoprotein enriched in astrocytes 15 Axis

BACKGROUND

Inflammatory bowel disease (IBD) is closely associated with the development of colorectal cancer (CRC) due to the chronic inflammatory response. Macrophages play critical roles in regulating the microenvironment to facilitate tumor progression. Exosomes are key modulators for the communication between macrophages and tumor cells. The mechanism of macrophage-derived exosomes in IBD-related CRC development remains unclear.

METHODS

The macrophages were isolated using fluorescence activating cell sorter (FACS). The RNA and protein expressions in exosomes and CRC cells were examined by quantitative real-time polymerase chain reaction and western blot assays, respectively. CRC cell development was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, BrdU staining, Transwell assay, and spheroid formation assay. The level of stemness was determined by detecting the proportion of leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5)-positive CRC cells and the expression of LGR5, CD133, and CD44. Molecular interaction experiments were done using luciferase reporter assay and RNA immunoprecipitation assay. Xenograft tumor model in vivo and immunohistochemistry were used to observe the pathological changes.

RESULTS

Macrophage-derived exosomes from IBD-related CRC tissues were enriched with nuclear paraspeckle assembly transcript 1 (NEAT1) and able to promote the progression and stemness of CRC both in vitro and in vivo. The exosomal NEAT1 could sponge miR-34a-5p, leading to the restoration of PEA15 expression in CRC cells and promoting the development of CRC. Inhibition of NEAT1 in exosomes could effectivity inhibit the tumor growth in the CRC xenograft model.

CONCLUSIONS

These findings provide novel insights into how macrophages affect CRC development and highlight exosomal NEAT1 as a therapeutic target for CRC treatment.

Role of Hypoxia-Associated Long Noncoding RNAs in Cancer Chemo-Therapy Resistance

Hypoxia is a well-known characteristic of the tumor microenvironment which significantly influences cancer development and is closely linked to unfavorable outcomes. Long noncoding RNAs (lncRNAs), which are part of the noncoding genome, have garnered increasing attention because of their varied functions in tumor metastasis. Long noncoding RNAs (lncRNAs) are defined as noncoding RNAs which are longer than 200 nucleotides, and they regulate diverse cellular processes by modulating gene expression at the transcriptional, post-transcriptional and epigenetic levels. Hypoxia is a well-established environmental factor which enhances the metastasis of solid tumors. Epithelial-mesenchymal transition (EMT) represents one of the key mechanisms triggered by hypoxia which contributes to metastasis. Numerous lncRNAs have been identified as being upregulated by hypoxia. These lncRNAs significantly contribute toward cancer cell migration, invasion and metastasis. Recent studies have identified a crucial role for these hypoxia-induced lncRNAs in chemotherapy resistance. These hypoxia-related lncRNAs can be plausible therapeutic targets for devising effective cancer therapies.

An overview of lncRNA NEAT1 contribution in the pathogenesis of female cancers; from diagnosis to therapy resistance

Despite the ongoing progress in detecting and treating cancer, there is still a need for extensive research into the molecular mechanisms involved in the emergence, progression, and resistance to recurrence of female reproductive tissue-specific cancers such as ovarian, breast, cervical, and endometrial cancers. The nuclear paraspeckle assembly transcript 1 (NEAT1) is a long non-coding RNA (lncRNA) that exhibits increased expression in female tumors. Moreover, elevated levels of NEAT1 have been associated with poorer survival outcomes in cancer patients. NEAT1 plays a pivotal role in driving tumor initiation through modulating the expression of genes involved in various aspects of tumor cell proliferation, epithelial-to-mesenchymal transition (EMT), metastasis, chemoresistance, and radio-resistance. Mechanistically, NEAT1 acts as a scaffold RNA molecule via interacting with EZH2 (Enhancer of Zeste 2 Polycomb Repressive Complex 2 Subunit), thereby influencing the expression of downstream effectors of EZH2. Additionally, NEAT1 functions as a competing endogenous RNA (ceRNA) by microRNAs (miRNAs) sponging, consequently altering the expression levels of their target genes during the development of female cancers. This comprehensive review aims to shed light on the latest insights regarding the expression pattern, biological functions, and underlying mechanisms governing the function and regulation of NEAT1 in tumors. Furthermore, particular emphasis is placed on its clinical significance as a novel diagnostic biomarker and a promising therapeutic target for female cancers.

Regulation of physiological and pathological condensates by molecular chaperones

Biomolecular condensates are dynamic membraneless compartments that regulate a myriad of cellular functions. A particular type of physiological condensate called stress granules (SGs) has gained increasing interest due to its role in the cellular stress response and various diseases. SGs, composed of several hundred RNA-binding proteins, form transiently in response to stress to protect mRNAs from translation and disassemble when the stress subsides. Interestingly, SGs contain several aggregation-prone proteins, such as TDP-43, FUS, hnRNPA1, and others, which are typically found in pathological inclusions seen in autopsy tissues from amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) patients. Moreover, mutations in these genes lead to the familial form of ALS and FTD. This has led researchers to propose that pathological aggregation is seeded by aberrant SGs: SGs that fail to properly disassemble, lose their dynamic properties, and become pathological condensates which finally 'mature' into aggregates. Here, we discuss the evidence supporting this model for various ALS/FTD-associated proteins. We further continue to focus on molecular chaperone-mediated regulation of ALS/FTD-associated physiological condensates on one hand, and pathological condensates on the other. In addition to SGs, we review ALS/FTD-relevant nuclear condensates, namely paraspeckles, anisosomes, and nucleolar amyloid bodies, and discuss their emerging regulation by chaperones. As the majority of chaperoning mechanisms regulate physiological condensate disassembly, we highlight parallel themes of physiological and pathological condensation regulation across different chaperone families, underscoring the potential for early disease intervention.

MALAT1 and NEAT1 are Neuroprotective During Hypoxic Preconditioning in the Mouse Hippocampus Possibly by Regulation of NR2B

Wang, Liping, Gang Fu, Ruijuan Han, Peijia Fan, Jing Yang, Kerui Gong, Zhijun Zhao, Chunyang Zhang, Kai Sun, and Guo Shao. MALAT1 and NEAT1 are neuroprotective during hypoxic preconditioning in the mouse hippocampus possibly by regulation of NR2B. High Alt Med Biol. 25:285-294, 2024. Background: The regulation of noncoding ribonucleic acid (ncRNA) has been shown to be involved in cellular and molecular responses to hypoxic preconditioning (HPC), a situation created by the induction of sublethal hypoxia in the brain. The ncRNAs metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) and nuclear paraspeckle assembly transcript 1 (NEAT1) are abundantly expressed in the brain, where they regulate the expression of various genes in nerve cells. However, the exact roles of MALAT1 and NEAT1 in HPC are not fully understood. Methods: A mouse model of acute repeated hypoxia was used as a model of HPC, and MALAT1 and NEAT1 levels in the hippocampus were measured using real-time polymerase chain reaction (PCR). The mRNA and protein levels of N-methyl-d-aspartate receptor subunit 2 B (NR2B) in the mouse hippocampus were measured using real-time PCR and western blotting, respectively. HT22 cells knocked-down for MALAT1 and NEAT1 were used for in vitro testing. Expression of NR2B, which is involved in nerve cell injury under ischemic and hypoxic conditions, was also evaluated. The levels of spectrin and cleaved caspase-3 in MALAT1 and NEAT1 knockdown HT22 cells under oxygen glucose deprivation/reperfusion (OGD/R) were determined by western blotting. Results: HPC increased the expression of MALAT1 and NEAT1 and decreased the expression of NR2B mRNA in the mouse hippocampus (p < 0.05). Knockdown of MALAT1 and NEAT1 increased both NR2B mRNA and protein levels nearly twofold and caused damage under OGD/R conditions in HT22 cells (p < 0.05). Conclusion: MALAT1 and NEAT1 exert neuroprotective effects by influencing the expression of NR2B.

Virus-modified paraspeckle-like condensates are hubs for viral RNA processing and their formation drives genomic instability

The nucleus is a highly organised yet dynamic environment containing distinct membraneless nuclear bodies. This spatial separation enables a subset of components to be concentrated within biomolecular condensates, allowing efficient and discrete processes to occur which regulate cellular function. One such nuclear body, paraspeckles, are comprised of multiple paraspeckle proteins (PSPs) built around the architectural RNA, NEAT1_2. Paraspeckle function is yet to be fully elucidated but has been implicated in a variety of developmental and disease scenarios. We demonstrate that Kaposi's sarcoma-associated herpesvirus (KSHV) drives formation of structurally distinct paraspeckles with a dramatically increased size and altered protein composition that are required for productive lytic replication. We highlight these virus-modified paraspeckles form adjacent to virus replication centres, potentially functioning as RNA processing hubs for viral transcripts during infection. Notably, we reveal that PSP sequestration into virus-modified paraspeckles result in increased genome instability during both KSHV and Epstein Barr virus (EBV) infection, implicating their formation in virus-mediated tumourigenesis.

The landscape of lncRNAs in cell granules: Insights into their significance in cancer

Cellular compartmentalization, achieved through membrane-based compartments, is a fundamental aspect of cell biology that contributes to the evolutionary success of cells. While organelles have traditionally been the focus of research, membrane-less organelles (MLOs) are emerging as critical players, exhibiting distinct morphological features and unique molecular compositions. Recent research highlights the pivotal role of long noncoding RNAs (lncRNAs) in MLOs and their involvement in various cellular processes across different organisms. In the context of cancer, dysregulation of MLO formation, influenced by altered lncRNA expression, impacts chromatin organization, oncogenic transcription, signaling pathways, and telomere lengthening. This review synthesizes the current understanding of lncRNA composition within MLOs, delineating their functions and exploring how their dysregulation contributes to human cancers. Environmental challenges in tumorigenesis, such as nutrient deprivation and hypoxia, induce stress granules, promoting cancer cell survival and progression. Advancements in biochemical techniques, particularly single RNA imaging methods, offer valuable tools for studying RNA functions within live cells. However, detecting low-abundance lncRNAs remains challenging due to their limited expression levels. The correlation between lncRNA expression and pathological conditions, particularly cancer, should be explored, emphasizing the importance of single-cell studies for precise biomarker identification and the development of personalized therapeutic strategies. This article is categorized under: RNA Export and Localization > RNA Localization RNA in Disease and Development > RNA in Disease RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexes.

Targeting and engineering long non-coding RNAs for cancer therapy

RNA therapeutics (RNATx) aim to treat diseases, including cancer, by targeting or employing RNA molecules for therapeutic purposes. Amongst the most promising targets are long non-coding RNAs (lncRNAs), which regulate oncogenic molecular networks in a cell type-restricted manner. lncRNAs are distinct from protein-coding genes in important ways that increase their therapeutic potential yet also present hurdles to conventional clinical development. Advances in genome editing, oligonucleotide chemistry, multi-omics and RNA engineering are paving the way for efficient and cost-effective lncRNA-focused drug discovery pipelines. In this Review, we present the emerging field of lncRNA therapeutics for oncology, with emphasis on the unique strengths and challenges of lncRNAs within the broader RNATx framework. We outline the necessary steps for lncRNA therapeutics to deliver effective, durable, tolerable and personalized treatments for cancer.

Long noncoding RNAs as versatile molecular regulators of cellular stress response and homeostasis

Normal cell and body functions need to be maintained and protected against endogenous and exogenous stress conditions. Different cellular stress response pathways have evolved that are utilized by mammalian cells to recognize, process and overcome numerous stress stimuli in order to maintain homeostasis and to prevent pathophysiological processes. Although these stress response pathways appear to be quite different on a molecular level, they all have in common that they integrate various stress inputs, translate them into an appropriate stress response and eventually resolve the stress by either restoring homeostasis or inducing cell death. It has become increasingly appreciated that non-protein-coding RNA species, such as long noncoding RNAs (lncRNAs), can play critical roles in the mammalian stress response. However, the precise molecular functions and underlying modes of action for many of the stress-related lncRNAs remain poorly understood. In this review, we aim to provide a framework for the categorization of mammalian lncRNAs in stress response and homeostasis based on their experimentally validated modes of action. We describe the molecular functions and physiological roles of selected lncRNAs and develop a concept of how lncRNAs can contribute as versatile players in mammalian stress response and homeostasis. These concepts may be used as a starting point for the identification of novel lncRNAs and lncRNA functions not only in the context of stress, but also in normal physiology and disease.

Molecular Mechanisms of Tumorgenesis and Metastasis of Long Non-coding RNA (lncRNA) NEAT1 in Human Solid Tumors; An Update

The expression of the nuclear paraspeckle assembly transcript 1 (NEAT1), as a well-known long non-coding RNA (lncRNA), is often upregulated in varied types of cancers and associated with poor survival outcomes in patients suffering from tumors. NEAT1 promotes the tumors growth by influencing the various genes' expression profile that regulate various aspects of tumor cell behavior, in particular tumor growth, metastasis and drug resistance. This suggests that NEAT1 are capable of serving as a new diagnostic biomarker and target for therapeutic intervention. Through interrelation with enhancer of zeste homolog 2 (EZH2), NEAT1 acts as a scaffold RNA molecule, and thus regulating the expression EZH2-associated genes. Additionally, by perform as miRNA sponge, it constrains suppressing the interactions between miRNAs-mediated degradation of target mRNAs. In light of this, NEAT1 inhibition by small interfering RNA (siRNA) hampers tumorgenesis. We summarize recent findings about the expression, biological functions, and regulatory process of NEAT1 in human tumors. It specifically emphasizes the clinical significance of NEAT1 as a novel diagnostic biomarker and a promising therapeutic mark for many types of cancers.

Dynamic Localization of Paraspeckle Components under Osmotic Stress

Paraspeckles are nuclear condensates formed by NEAT1_2 lncRNA and different RNA-binding proteins. In general, these membraneless organelles function in the regulation of gene expression and translation and in miRNA processing, and in doing this, they regulate cellular homeostasis and mediate pro-survival in the cell. Despite evidence showing the importance of paraspeckles in the stress response, the dynamics of paraspeckles and their components under conditions of osmotic stress remain unknown. We exposed HEK293T cells to sorbitol and examined NEAT1_2 expression using real-time PCR. Localization and quantification of the main paraspeckle components, NEAT1_2, PSPC1, NONO, and SFPQ, in different cellular compartments was performed using smFISH and immunofluorescence. Our findings showed a significant decrease in total NEAT1_2 expression in cells after osmotic stress. Sorbitol shifted the subcellular localization of NEAT1_2, PSPC1, NONO, and SFPQ from the nucleus to the cytoplasm and decreased the number and size of NEAT1_2 foci in the nucleus. PSPC1 formed immunoreactive cytoplasmic fibrils under conditions of osmotic stress, which slowly disassembled under recovery. Our study deepens the paraspeckle dynamics in response to stress, suggesting a novel role for NEAT1_2 in the cytoplasm in osmotic stress and physiological conditions.

Translational control by long non-coding RNAs

Long non-coding (lnc) RNAs, once considered as junk and useless, are now broadly recognized to have major functions in the cell. LncRNAs are defined as non-coding RNAs of more than 200 nucleotides, regulate all steps of gene expression. Their origin is diverse, they can arise from intronic, intergenic or overlapping region, in sense or antisense direction. LncRNAs are mainly described for their action on transcription, while their action at the translational level is more rarely cited. However, the bibliography in the field is more and more abundant. The present synopsis of lncRNAs involved in the control of translation reveals a wide field of regulation of gene expression, with at least nine distinct molecular mechanisms. Furthermore, it appears that all these lncRNAs are involved in various pathologies including cancer, cardiovascular and neurodegenerative diseases.

LncRNA NEAT1 suppresses cellular senescence in hepatocellular carcinoma via KIF11-dependent repression of CDKN2A

BACKGROUND

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related deaths worldwide. Therapeutic options for advanced HCC are limited, which is due to a lack of full understanding of pathogenesis. Cellular senescence is a state of cell cycle arrest, which plays important roles in the pathogenesis of HCC. Mechanisms underlying hepatocellular senescence are not fully understood. LncRNA NEAT1 acts as an oncogene and contributes to the development of HCC. Whether NEAT1 modulates hepatocellular senescence in HCC is unknown.

METHODS

The role of NEAT1 and KIF11 in cellular senescence and tumor growth in HCC was assessed both in vitro and in vivo. RNA pulldown, mass spectrometry, Chromatin immunoprecipitation (ChIP), luciferase reporter assays, RNA FISH and immunofluorescence (IF) staining were used to explore the detailed molecular mechanism of NEAT1 and KIF11 in cellular senescence of HCC.

RESULTS

We found that NEAT1 was upregulated in tumor tissues and hepatoma cells, which negatively correlated with a senescence biomarker CDKN2A encoding p16INK4a and p14ARF proteins. NEAT1 was reduced in senescent hepatoma cells induced by doxorubicin (DOXO) or serum starvation. Furthermore, NEAT1 deficiency caused senescence in cultured hepatoma cells, and protected against the progression of HCC in a mouse model. During senescence, NEAT1 translocated into cytosol and interacted with a motor protein KIF11, resulting in KIF11 protein degradation and subsequent increased expression of CDKN2A in cultured hepatoma cells. Furthermore, KIF11 knockdown caused senescence in cultured hepatoma cells. Genetic deletion of Kif11 in hepatocytes inhibited the development of HCC in a mouse model.

CONCLUSIONS

Conclusively, NEAT1 overexpression reduces senescence and promotes tumor progression in HCC tissues and hepatoma cells, whereas NEAT1 deficiency causes senescence and inhibits tumor progression in HCC. This is associated with KIF11-dependent repression of CDKN2A. These findings lay the foundation to develop potential therapies for HCC by inhibiting NEAT1 and KIF11 or inducing senescence.

The disordered C terminus of ALKBH5 promotes phase separation and paraspeckles assembly

Paraspeckles (PS) are nuclear structures scaffolded by the long noncoding RNA NEAT1 and protein components such as NONO and SFPQ. We previously found that the upregulation of RNA N6-methyl-adenosine (m6A) demethylase ALKBH5 facilitates hypoxia-induced paraspeckle assembly through erasing m6A marks on NEAT1, thus stabilizing it. However, it remains unclear how these processes are spatiotemporally coordinated. Here we discover that ALKBH5 specifically binds to proteins in PS and forms phase-separated droplets that are incorporated into PS through its C-terminal intrinsically disordered region (cIDR). Upon exposure to hypoxia, rapid ALKBH5 condensation in PS induces m6A demethylation of NEAT1, which further facilitates PS formation before the upregulation of ALKBH5 expression. In cells expressing ALKBH5 lacking cIDR, PS fail to be formed in response to hypoxia, accompanied with insufficient m6A demethylation of NEAT1 and its destabilization. We also demonstrate that ALKBH5-cIDR is indispensable for hypoxia-induced effects such as cancer cell invasion. Therefore, our study has identified the role of ALKBH5 in phase separation as the molecular basis of the positive feedback loop for PS formation between ALKBH5 incorporation into PS and NEAT1 stabilization.

Hypoxia-driven ncRNAs in breast cancer

Low oxygen tension, or hypoxia is the driving force behind tumor aggressiveness, leading to therapy resistance, metastasis, and stemness in solid cancers including breast cancer, which now stands as the leading cause of cancer-related mortality in women. With the great advancements in exploring the regulatory roles of the non-coding genome in recent years, the wide spectrum of hypoxia-responsive genome is not limited to just protein-coding genes but also includes multiple types of non-coding RNAs, such as micro RNAs, long non-coding RNAs, and circular RNAs. Over the years, these hypoxia-responsive non-coding molecules have been greatly implicated in breast cancer. Hypoxia drives the expression of these non-coding RNAs as upstream modulators and downstream effectors of hypoxia inducible factor signaling in the favor of breast cancer through a myriad of molecular mechanisms. These non-coding RNAs then contribute in orchestrating aggressive hypoxic tumor environment and regulate cancer associated cellular processes such as proliferation, evasion of apoptotic death, extracellular matrix remodeling, angiogenesis, migration, invasion, epithelial-to-mesenchymal transition, metastasis, therapy resistance, stemness, and evasion of the immune system in breast cancer. In addition, the interplay between hypoxia-driven non-coding RNAs as well as feedback and feedforward loops between these ncRNAs and HIFs further contribute to breast cancer progression. Although the current clinical implications of hypoxia-driven non-coding RNAs are limited to prognostics and diagnostics in breast cancer, extensive explorations have established some of these hypoxia-driven non-coding RNAs as promising targets to treat aggressive breast cancers, and future scientific endeavors hold great promise in targeting hypoxia-driven ncRNAs at clinics to treat breast cancer and limit global cancer burden.

Long Non-Coding RNAs, Cell Cycle, and Human Breast Cancer

The long non-coding RNAs (lncRNAs) constitute an important class of the human transcriptome. The discovery of lncRNAs provided one of many unexpected results of the post-genomic era and uncovered a huge number of previously ignored transcriptional events. In recent years, lncRNAs are known to be linked with human diseases, with particular focus on cancer. Growing evidence has indicated that dysregulation of lncRNAs in breast cancer (BC) is strongly associated with the occurrence, development, and progress. Increasing numbers of lncRNAs have been found to interact with cell cycle progression and tumorigenesis in BC. The lncRNAs can exert their effect as a tumor suppressor or oncogene and regulate tumor development through direct or indirect regulation of cancer-related modulators and signaling pathways. What is more, lncRNAs are excellent candidates for promising therapeutic targets in BC due to the features of high tissue and cell-type specific expression. However, the underlying mechanisms of lncRNAs in BC still remain largely undefined. Here, we concisely summarize and sort out the current understanding of research progress in relationships of the roles for lncRNA in regulating the cell cycle. We also summarize the evidence for aberrant lncRNA expression in BC, and the potential for lncRNA to improve BC therapy is also discussed. Together, lncRNAs can be considered as exciting therapeutic candidates whose expression can be altered to impede BC progression.

Revisiting the hallmarks of cancer: A new look at long noncoding RNAs in breast cancer

Breast cancer is one of the leading causes of death in women worldwide. The increasing understanding of the molecular mechanisms underlying its heterogeneity favors a better understanding of tumor biology and consequently the development of better diagnostic and treatment techniques. The advent of tumor genome sequencing techniques has highlighted more participants in the process, in addition to protein-coding genes. Thus, it is now known that long noncoding RNAs, previously described as transcriptional noise with no biological function, are intimately associated with tumor development. In breast cancer, they are abnormally expressed and closely associated with tumor progression, which makes them attractive diagnostic biomarkers and prognostic and specific therapeutic targets. Therefore, a thorough understanding of the regulatory mechanisms of long noncoding RNAs in breast cancer is essential for the search for new treatment strategies. In this review, we summarize the major long noncoding RNAs and their association with the cancer characteristics of the ability to sustain proliferative signaling, evasion of growth suppressors, replicative immortality, activation of invasion and metastasis, induction of angiogenesis, resistance to cell death, reprogramming of energy metabolism, genomic instability and sustained mutations, promotion of tumor inflammation, and evasion of the immune system. In addition, we report and suggest how they can be used as prognostic biomarkers and possible therapeutic targets.

Molecular regulation of hypoxia through the lenses of noncoding RNAs and epitranscriptome

Cells maintain homeostasis in response to environmental stress through specific cell stress responses. Hypoxic stress, well known to be associated with diverse solid tumors, is one of the main reasons for cancer-related mortality. Although cells can balance themselves well during hypoxic stress, the underlying molecular mechanisms are not well understood. The enhanced appreciation of diverse roles played by noncoding transcriptome and epigenome in recent years has brought to light the involvement of noncoding RNAs and epigenetic modifiers in hypoxic regulation. The emergence of techniques like deep sequencing has facilitated the identification of large numbers of long noncoding RNAs (lncRNAs) that are differentially regulated in various cancers. Similarly, proteomic studies have identified diverse epigenetic modifiers such as HATs, HDACs, DNMTs, polycomb groups of proteins, and their possible roles in the regulation of hypoxia. The crosstalk between lncRNAs and epigenetic modifiers play a pivotal role in hypoxia-induced cancer initiation and progression. Besides the lncRNAs, several other noncoding RNAs like circular RNAs, miRNAs, and so forth are also expressed during hypoxic conditions. Hypoxia has a profound effect on the expression of noncoding RNAs and epigenetic modifiers. Conversely, noncoding RNAs/epigenetic modifies can regulate the hypoxia signaling axis by modulating the stability of the hypoxia-inducible factors (HIFs). The focus of this review is to illustrate the molecular orchestration underlying hypoxia biology, especially in cancers, which can help in identifying promising therapeutic targets in hypoxia-induced cancers. This article is categorized under: RNA Turnover and Surveillance > Regulation of RNA Stability RNA in Disease and Development > RNA in Disease RNA Structure and Dynamics > RNA Structure, Dynamics and Chemistry.

MicroRNA-Based Markers of Oral Tongue Squamous Cell Carcinoma and Buccal Squamous Cell Carcinoma: A Systems Biology Approach

Objective

Oral tongue squamous cell carcinoma (OTSCC) and buccal squamous cell carcinoma (BSCC) are the first and second leading causes of oral cancer, respectively. OTSCC and BSCC are associated with poor prognosis in patients with oral cancer. Thus, we aimed to indicate signaling pathways, Gene Ontology terms, and prognostic markers mediating the malignant transformation of the normal oral tissue to OTSCC and BSCC.

Methods

The dataset GSE168227 was downloaded and reanalyzed from the GEO database. Orthogonal partial least square (OPLS) analysis identified common differentially expressed miRNAs (DEMs) in OTSCC and BSCC compared to their adjacent normal mucosa. Next, validated targets of DEMs were identified using the TarBase web server. With the use of the STRING database, a protein interaction map (PIM) was created. Using the Cytoscape program, hub genes and clusters within the PIM were shown. Next, gene-set enrichment analysis was carried out using the g:Profiler tool. Using the GEPIA2 web tool, analyses of gene expression and survival analysis were also performed.

Results

Two DEMs, including has-miR-136 and has-miR-377, were common in OTSCC and BSCC (p value <0.01; |Log2 FC| > 1). A total of 976 targets were indicated for common DEMs. PIM included 96 hubs, and the upregulation of EIF2S1, CAV1, RAN, ANXA5, CYCS, CFL1, MYC, HSP90AA1, PKM, and HSPA5 was significantly associated with a poor prognosis in the head and neck squamous cell carcinoma (HNSCC), while NTRK2, HNRNPH1, DDX17, and WDR82 overexpression was significantly linked to favorable prognosis in the patients with HNSCC. "Clathrin-mediated endocytosis" was considerably dysregulated in OTSCC and BSCC.

Conclusion

The present study suggests that has-miR-136 and has-miR-377 are underexpressed in OTSCC and BSCC than in normal oral mucosa. Moreover, EIF2S1, CAV1, RAN, ANXA5, CYCS, CFL1, MYC, HSP90AA1, PKM, HSPA5, NTRK2, HNRNPH1, DDX17, and WDR82 demonstrated prognostic markers in HNSCC. These findings may benefit the prognosis and management of individuals with OTSCC/BSCC. However, additional experimental verification is required.

Regulation of LncRNAs and microRNAs in neuronal development and disease

Non-coding RNAs (ncRNAs) are RNAs that do not encode proteins but play important roles in regulating cellular processes. Multiple studies over the past decade have demonstrated the role of microRNAs (miRNAs) in cancer, in which some miRNAs can act as biomarkers or provide therapy target. Accumulating evidence also points to the importance of long non-coding RNAs (lncRNAs) in regulating miRNA-mRNA networks. An increasing number of ncRNAs have been shown to be involved in the regulation of cellular processes, and dysregulation of ncRNAs often heralds disease. As the population ages, the incidence of neurodegenerative diseases is increasing, placing enormous pressure on global health systems. Given the excellent performance of ncRNAs in early cancer screening and treatment, here we attempted to aggregate and analyze the regulatory functions of ncRNAs in neuronal development and disease. In this review, we summarize current knowledge on ncRNA taxonomy, biogenesis, and function, and discuss current research progress on ncRNAs in relation to neuronal development, differentiation, and neurodegenerative diseases.

Hypoxia-inducible factor-2α and its missense mutations: potential role in HCC diagnosis, progression, and prognosis and underlying mechanism

Objective

This study aims to gain further the potential mechanisms of HIF-2α in tumor progression and tumorigenesis.

Methods

Mined The Cancer Genome Atlas (TCGA) dataset. In total, 421 participants were enrolled in the TCGAHepatocellular Carcinoma (HCC) study, comprising 371 patients with cancer and 50 healthy controls. From the 371 tumor samples, three samples containing the missense mutation of the HIF-2α gene were compared with 368 wild-type samples to identify differentially expressed genes (DEGs).

Results

After filtering, univariate Cox regression and multivariate Cox regression analyses showed that the differentially expressed genes (DEGs) progestagen-associated endometrial protein (PAEP) PNLIPRP2, MIR147B, and pregnancy zone protein (PZP) were significantly correlated with the survival times of patients with HCC. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed using the Database for Annotation, Visualization, and Integrated Discovery (DAVID) v6.8 database to detect the functional annotation of these four DEGs as well as hub genes obtained from protein-protein interaction (PPI) network analysis using the STRING v10 database. Our analysis focused on the PAEP and PZP genes, whose protein expressions were downregulated in samples with HIF-2α missense mutation. The hub genes of PAEP and PZP were identified using PPI network analysis. Subsequent Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that PAEP and its hub genes were highly enriched in the TGF-β pathway, which is consistent with the analysis of PZP.

Conclusion

Our study proved that the missense mutation of HIF-2α induces the upregulation of PAEP, which is positively related to the poor prognosis of patients with HCC, as it may upregulate the TGF-β pathway. In contrast, PZP downregulation showed the opposite phenomenon, as it may downregulate the TGF-β pathway.

LncRNA NEAT1 regulates HCV-induced Hepatocellular carcinoma by modulating the miR-9-BGH3 axis

Chronic hepatitis C virus (HCV) infection is a leading cause of end-stage liver diseases, such as fibrosis, cirrhosis and hepatocellular carcinoma (HCC). Several cellular entities, including paraspeckles and their related components, are involved in viral pathogenesis and cancer progression. NEAT1 lncRNA is a major component of paraspeckles that has been linked to several malignancies. In this study, analysis of the Cancer Genome Atlas (TCGA) database and validation in HCV-induced HCC tissue and serum samples showed significantly high expression of NEAT1 in patients with liver cancer. Moreover, we found that NEAT1 levels increased upon HCV infection. To further understand the mechanism of NEAT1-induced HCC progression, we selected one of its targets, miR-9-5 p, which regulates BGH3 mRNA levels. Interestingly, miR-9-5 p levels were downregulated upon HCV infection, whereas BGH3 levels were upregulated. Additionally, partial NEAT1 knockdown increased miR-9-5 p levels and decreased BGH3 levels, corroborating our initial results. BGH3 levels were also upregulated in HCV-induced HCC and TCGA tissue samples, which could be directly correlated with NEAT1 levels. As a known oncogene, BGH3 is directly linked to HCC progression mediated by NEAT1. We also found that NEAT1 levels remained upregulated in serum samples from patients treated with direct-acting antivirals (DAA), indicating that NEAT1 might be a molecular trigger that promotes HCC development. Collectively, these findings provide molecular insights into HCV-induced HCC progression via the NEAT1-miR-9-BGH3 axis.

Reorganization of Cell Compartmentalization Induced by Stress

The discovery of intrinsically disordered proteins (IDPs) that do not have an ordered structure and nevertheless perform essential functions has opened a new era in the understanding of cellular compartmentalization. It threw the bridge from the mostly mechanistic model of the organization of the living matter to the idea of highly dynamic and functional "soft matter". This paradigm is based on the notion of the major role of liquid-liquid phase separation (LLPS) of biopolymers in the spatial-temporal organization of intracellular space. The LLPS leads to the formation of self-assembled membrane-less organelles (MLOs). MLOs are multicomponent and multifunctional biological condensates, highly dynamic in structure and composition, that allow them to fine-tune the regulation of various intracellular processes. IDPs play a central role in the assembly and functioning of MLOs. The LLPS importance for the regulation of chemical reactions inside the cell is clearly illustrated by the reorganization of the intracellular space during stress response. As a reaction to various types of stresses, stress-induced MLOs appear in the cell, enabling the preservation of the genetic and protein material during unfavourable conditions. In addition, stress causes structural, functional, and compositional changes in the MLOs permanently present inside the cells. In this review, we describe the assembly of stress-induced MLOs and the stress-induced modification of existing MLOs in eukaryotes, yeasts, and prokaryotes in response to various stress factors.

Conducive target range of breast cancer: Hypoxic tumor microenvironment

Breast cancer is a kind of malignant tumor disease that poses a serious threat to human health. Its biological characteristics of rapid proliferation and delayed angiogenesis, lead to intratumoral hypoxia as a common finding in breast cancer. HIF as a transcription factor, mediate a series of reactions in the hypoxic microenvironment, including metabolic reprogramming, tumor angiogenesis, tumor cell proliferation and metastasis and other important physiological and pathological processes, as well as gene instability under hypoxia. In addition, in the immune microenvironment of hypoxia, both innate and acquired immunity of tumor cells undergo subtle changes to support tumor and inhibit immune activity. Thus, the elucidation of tumor microenvironment hypoxia provides a promising target for the resistance and limited efficacy of current breast cancer therapies. We also summarize the hypoxic mechanisms of breast cancer treatment related drug resistance, as well as the current status and prospects of latest related drugs targeted HIF inhibitors.

Regulatory mechanisms and function of hypoxia-induced long noncoding RNA NDRG1-OT1 in breast cancer cells

Hypoxia is a classic feature of the tumor microenvironment that has profound effects on cancer progression and is tightly associated with poor prognosis. Long noncoding RNAs (lncRNAs), a component of the noncoding genome, have been increasingly investigated due to their diverse roles in tumorigenesis. Previously, a hypoxia-induced lncRNA, NDRG1-OT1, was identified in MCF-7 breast cancer cells using next-generation sequencing. However, the regulatory mechanisms of NDRG1-OT1 remain elusive. Therefore, the purpose of this study was to investigate the regulatory mechanisms and functional roles of NDRG1-OT1 in breast cancer cells. Expression profiling of NDRG1-OT1 revealed that it was upregulated under hypoxia in different breast cancer cells. Overexpression and knockdown of HIF-1α up- and downregulated NDRG1-OT1, respectively. Luciferase reporter assays and chromatin immunoprecipitation assays validated that HIF-1α transcriptionally activated NDRG1-OT1 by binding to its promoter (-1773 to -1769 and -647 to -643 bp). Next, to investigate whether NDRG1-OT1 could function as a miRNA sponge, results of in silico analysis, expression profiling of predicted miRNAs, and RNA immunoprecipitation assays indicated that NDRG1-OT1 could act as a miRNA sponge of miR-875-3p. In vitro and in vivo functional assays showed that NDRG1-OT1 could promote tumor growth and migration. Lastly, a small peptide (66 a.a.) translated from NDRG1-OT1 was identified. In summary, our findings revealed novel regulatory mechanisms of NDRG1-OT1 by HIF-1α and upon miR-875-3p. Also, NDRG1-OT1 promoted the malignancy of breast cancer cells and encoded a small peptide.

The Long and the Short of It: NEAT1 and Cancer Cell Metabolism

Simple Summary

Altered metabolism is a hallmark of most cancers. The way that cancer cells regulate their energy production to fuel constant proliferation has been of interest with the hope that it may be exploited therapeutically. The long noncoding RNA, NEAT1, is often dysregulated in tumours. NEAT1 RNA can be transcribed as two isoforms with different lengths, with each variant responsible for different functions. This review explores how the isoforms contribute to cancer metabolism.

Abstract

The long noncoding RNA NEAT1 is known to be heavily dysregulated in many cancers. A single exon gene produces two isoforms, NEAT1_1 and NEAT1_2, through alternative 3′-end processing. As the longer isoform, NEAT1_2 is an essential scaffold for nuclear paraspeckle formation. It was previously thought that the short NEAT1_1 isoform only exists to keep the NEAT1 locus active for rapid paraspeckle formation. However, a recent glycolysis-enhancing function for NEAT1_1, contributing to cancer cell proliferation and the Warburg effect, has been demonstrated. Previous studies have mainly focused on quantifying total NEAT1 and NEAT1_2 expression levels. However, in light of the NEAT1_1 role in cancer cell metabolism, the contribution from specific NEAT1 isoforms is no longer clear. Here, the roles of NEAT1_1 and NEAT1_2 in metabolism and cancer progression are discussed.

Molecular Interactions of the Long Noncoding RNA NEAT1 in Cancer

As one of the best-studied long noncoding RNAs, nuclear paraspeckle assembly transcript 1 (NEAT1) plays a pivotal role in the progression of cancers. NEAT1, especially its isoform NEAT1-1, facilitates the growth and metastasis of various cancers, excluding acute promyelocytic leukemia. NEAT1 can be elevated via transcriptional activation or stability alteration in cancers changing the aggressive phenotype of cancer cells. NEAT1 can also be secreted from other cells and be delivered to cancer cells through exosomes. Hence, elucidating the molecular interaction of NEAT1 may shed light on the future treatment of cancer. Herein, we review the molecular function of NEAT1 in cancer progression, and explain how NEAT1 interacts with RNAs, proteins, and DNA promoter regions to upregulate tumorigenic factors.

Liquid-liquid phase separation in tumor biology

Liquid-liquid phase separation (LLPS) is a novel principle for explaining the precise spatial and temporal regulation in living cells. LLPS compartmentalizes proteins and nucleic acids into micron-scale, liquid-like, membraneless bodies with specific functions, which were recently termed biomolecular condensates. Biomolecular condensates are executors underlying the intracellular spatiotemporal coordination of various biological activities, including chromatin organization, genomic stability, DNA damage response and repair, transcription, and signal transduction. Dysregulation of these cellular processes is a key event in the initiation and/or evolution of cancer, and emerging evidence has linked the formation and regulation of LLPS to malignant transformations in tumor biology. In this review, we comprehensively summarize the detailed mechanisms of biomolecular condensate formation and biophysical function and review the recent major advances toward elucidating the multiple mechanisms involved in cancer cell pathology driven by aberrant LLPS. In addition, we discuss the therapeutic perspectives of LLPS in cancer research and the most recently developed drug candidates targeting LLPS modulation that can be used to combat tumorigenesis.

Identification and characterization of a special type of subnuclear structure: AGGF1-coated paraspeckles

AGGF1 is an angiogenic factor with G-Patch and FHA domains 1 described by our group. Gain-of-function mutations in AGGF1 cause Klippel-Trenaunay syndrome, whereas somatic loss-of-function mutations cause cancer. Paraspeckles are small membraneless subnuclear structures with a diameter of 0.5-1 μm, and composed of lncRNA NEAT1 as the scaffold and three core RNA-binding proteins NONO, PSPC1, and PSF. Here, we show that AGGF1 is a key regulatory and structural component of paraspeckles that induces paraspeckle formation, forms an outside rim of paraspeckles, wraps around the NONO/PSF/PSPC1/NEAT1 core, and regulates the size and number of paraspeckles. AGGF1-paraspeckles are larger (>1 μm) than conventional paraspeckles. RNA-FISH in combination with immunostaining shows that AGGF1, NONO, and NEAT1_2 co-localize in 20.58% of NEAT1_2-positive paraspeckles. Mechanistically, AGGF1 interacts with NONO, PSF, and HNRNPK, and upregulates NEAT1_2, a longer, 23 kb NEAT1 transcript with a key role in regulation of paraspeckle size and number. RNA-immunoprecipitation shows that AGGF1 interacts with NEAT1, which may be another possible mechanism underlying the formation of AGGF1-paraspeckles. NEAT1_2 knockdown reduces the number and size of AGGF1-paraspeckles. Functionally, AGGF1 regulates alternative RNA splicing as it decreases the exon skipping/inclusion ratio in a CD44 model. AGGF1 is also localized in some nuclear foci without NEAT1 or NONO, suggesting that AGGF1 is an important liquid-liquid phase separation (LLPS) driver for other types of AGGF1-positive nuclear condensates (referred to as AGGF1-bodies). Our results identify a special type of AGGF1-coated paraspeckles and provide important insights into the formation, structure, and function of paraspeckles.

Stressing the Regulatory Role of Long Non-Coding RNA in the Cellular Stress Response during Cancer Progression and Therapy

Cellular stress response is an important adaptive mechanism for regulating cell fate decision when cells confront with stress. During tumorigenesis, tumor progression and the course of treatment, cellular stress signaling can activate subsequent response to deal with stress. Therefore, cellular stress response has impacts on the fate of tumor cells and tumor responsiveness relative to therapeutic agents. In recent years, attention has been drawn to long non-coding RNAs (lncRNAs), a novel class of RNA molecules with more than 200 nucleotides in length, which has little protein-coding potential and possesses various functions in multiple biological processes. Accumulating evidence has shown that lncRNAs are also engaged in the regulation of cellular stress response, particularly in cancers. Here, we summarize lncRNAs that have been reported in the adaptive response to major types of cellular stress including genotoxic, hypoxic, oxidative, metabolic and endoplasmic reticulum stress, all of which are often encountered by cancer cells. Specifically, the molecular mechanisms of how lncRNAs regulate cellular stress response during tumor progression or the development of therapy resistance are emphasized. The potential clinical applications of stress-responsive lncRNAs as biomarkers will also be discussed.

The Role of Hypoxia-Associated Long Non-Coding RNAs in Breast Cancer

Breast cancer is the leading cause of cancer-related deaths in women worldwide. In the United States, even with earlier diagnosis and treatment improvements, the decline in mortality has stagnated in recent years. More research is needed to provide better diagnostic, prognostic, and therapeutic tools for these patients. Long non-coding RNAs are newly described molecules that have extensive roles in breast cancer. Emerging reports have shown that there is a strong link between these RNAs and the hypoxic response of breast cancer cells, which may be an important factor for enhanced tumoral progression. In this review, we summarize the role of hypoxia-associated lncRNAs in the classic cancer hallmarks, describing their effects on the upstream and downstream hypoxia signaling pathway and the use of them as diagnostic and prognostic tools.

Long non-coding RNA DEPDC1-AS1 promotes proliferation and migration of human gastric cancer cells HGC-27 via the human antigen R-F11R pathway

Objective

Long non-coding (lnc) RNAs are critical regulators in carcinogenesis. The novel lncRNA DEPDC1 antisense RNA 1 (DEPDC1-AS1) was recently associated with poor prognosis in triple-negative breast cancer and lung adenocarcinoma. However, its role in regulating the malignant progression of gastric cancer (GC) and its molecular mechanism are unclear. We herein explored the functions of DEPDC1-AS1 in GC progression.

Methods

DEPDC1-AS1 expression and prognosis in GC tissues were examined by bioinformatics analysis and quantitative reverse transcription polymerase chain reaction. The DEPDC1-AS1 function in GC cells was explored by the cell counting kit-8 assay, colony formation assay, Transwell assay, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling, 5-ethynyl-2′-deoxyuridine-incorporation, and the xenograft tumor model. The DEPDC1-AS1 and human antigen (Hu)R interaction was determined by RNA pull-down and RNA immunoprecipitation.

Results

DEPDC1-AS1 was overexpressed in GC tissues and cell lines, and associated with a worse prognosis in GC patients. In vitro and in vivo assays showed that DEPDC1-AS1 promoted HGC-27 cell proliferation and migration. Mechanistically, DEPDC1-AS1 served as a scaffold by combining with HuR to target the specific mRNA F11R.

Conclusion

DEPDC1-AS1 plays a crucial role in GC development and progression and is a potential biomarker for the early detection or prognosis of GC.

An oxygen-adaptive interaction between SNHG12 and occludin maintains blood-brain barrier integrity

Tight junctions (TJs) of brain microvascular endothelial cells (BMECs) play a pivotal role in maintaining the blood-brain barrier (BBB) integrity; however, precise regulation of TJs stability in response to physiological and pathological stimuli remains elusive. Here, using RNA immunoprecipitation with next-generation sequencing (RIP-seq) and functional characterization, we identify SNHG12, a long non-coding RNA (lncRNA), as being critical for maintaining the BBB integrity by directly interacting with TJ protein occludin. The interaction between SNHG12 and occludin is oxygen adaptive and could block Itch (an E3 ubiquitin ligase)-mediated ubiquitination and degradation of occludin in human BMECs. Genetic ablation of endothelial Snhg12 in mice results in occludin reduction and BBB leakage and significantly aggravates hypoxia-induced BBB disruption. The detrimental effects of hypoxia on BBB could be alleviated by exogenous SNHG12 overexpression in brain endothelium. Together, we identify a direct TJ modulator lncRNA SNHG12 that is critical for the BBB integrity maintenance and oxygen adaption.

Expression and functions of long non-coding RNA NEAT1 and isoforms in breast cancer

NEAT1 is a highly abundant nuclear architectural long non-coding RNA. There are two overlapping NEAT1 isoforms, NEAT1_1 and NEAT1_2, of which the latter is an essential scaffold for the assembly of a class of nuclear ribonucleoprotein bodies called paraspeckles. Paraspeckle formation is elevated by a wide variety of cellular stressors and in certain developmental processes, either through transcriptional upregulation of the NEAT1 gene or through a switch from NEAT1_1 to NEAT1_2 isoform production. In such conditions, paraspeckles modulate cellular processes by sequestering proteins or RNA molecules. NEAT1 is abnormally expressed in many cancers and a growing body of evidence suggests that, in many cases, high NEAT1 levels are associated with therapy resistance and poor clinical outcome. Here we review the current knowledge of NEAT1 expression and functions in breast cancer, highlighting its established role in postnatal mammary gland development. We will discuss possible isoform-specific roles of NEAT1_1 and NEAT1_2 in different breast cancer subtypes, which critically needs to be considered when studying NEAT1 and breast cancer.

Heterogeneity of human corneal endothelium implicates lncRNA NEAT1 in Fuchs endothelial corneal dystrophy

The corneal endothelium is critical for maintaining corneal clarity by mediating hydration through barrier and pump functions. Progressive loss of corneal endothelial cells during aging has been associated with the development of Fuchs endothelial corneal dystrophy (FECD), one of the main causes of cornea-related vision loss. The mechanisms underlying FECD development remain elusive. Single-cell RNA sequencing of isolated healthy human corneas discovered 4 subpopulations of corneal endothelial cells with distinctive signatures. Unsupervised clustering analysis uncovered nuclear enriched abundant transcript 1 (NEAT1), a long non-coding RNA (lncRNA), as the top expressed gene in the C0-endothelial subpopulation, but markedly downregulated in FECD. Consistent with human corneas, a UVA-induced mouse FECD model validated the loss of NEAT1 expression. Loss of NEAT1 function by an in vivo genetic approach reproduced the exacerbated phenotype of FECD by ablating corneal endothelial cells. Conversely, gain of function by a CRISPR-activated adenoviral delivery system protected corneas from UVA-induced FECD. Our findings provide novel mechanistic insights into the development of FECD, and targeting NEAT1 offers an attractive approach for treating FECD.

Molecular and cellular functions of long non-coding RNAs in prostate and breast cancer

Long noncoding RNAs (lncRNAs) are defined as noncoding RNA transcripts with a length greater than 200 nucleotides. Research over the last decade has made great strides in our understanding of lncRNAs, especially in the biology of their role in cancer. In this article, we will briefly discuss the biogenesis and characteristics of lncRNAs, then review their molecular and cellular functions in cancer by using prostate and breast cancer as examples. LncRNAs are abundant, diverse, and evolutionarily, less conserved than protein-coding genes. They are often expressed in a tumor and cell-specific manner. As a key epigenetic factor, lncRNAs can use a wide variety of molecular mechanisms to regulate gene expression at each step of the genetic information flow pathway. LncRNAs display widespread effects on cell behavior, tumor growth, and metastasis. They act intracellularly and extracellularly in an autocrine, paracrine and endocrine fashion. Increased understanding of lncRNA's role in cancer has facilitated the development of novel biomarkers for cancer diagnosis, led to greater understanding of cancer prognosis, enabled better prediction of therapeutic responses, and promoted identification of potential targets for cancer therapy.

Long non-coding RNA Neat1 and paraspeckle components are translational regulators in hypoxia

Internal ribosome entry sites (IRESs) drive translation initiation during stress. In response to hypoxia, (lymph)angiogenic factors responsible for tissue revascularization in ischemic diseases are induced by the IRES-dependent mechanism. Here, we searched for IRES trans-acting factors (ITAFs) active in early hypoxia in mouse cardiomyocytes. Using knock-down and proteomics approaches, we show a link between a stressed-induced nuclear body, the paraspeckle, and IRES-dependent translation. Furthermore, smiFISH experiments demonstrate the recruitment of IRES-containing mRNA into paraspeckle during hypoxia. Our data reveal that the long non-coding RNA Neat1, an essential paraspeckle component, is a key translational regulator, active on IRESs of (lymph)angiogenic and cardioprotective factor mRNAs. In addition, paraspeckle proteins p54^nrb and PSPC1 as well as nucleolin and RPS2, two p54^nrb-interacting proteins identified by mass spectrometry, are ITAFs for IRES subgroups. Paraspeckle thus appears as a platform to recruit IRES-containing mRNAs and possibly host IRESome assembly. Polysome PCR array shows that Neat1 isoforms regulate IRES-dependent translation and, more widely, translation of mRNAs involved in stress response.

The Roles and Mechanisms of lncRNAs in Liver Fibrosis

Long non-coding RNAs (lncRNAs) can potentially regulate all aspects of cellular activity including differentiation and development, metabolism, proliferation, apoptosis, and activation, and benefited from advances in transcriptomic and genomic research techniques and database management technologies, its functions and mechanisms in physiological and pathological states have been widely reported. Liver fibrosis is typically characterized by a reversible wound healing response, often accompanied by an excessive accumulation of extracellular matrix. In recent years, a range of lncRNAs have been investigated and found to be involved in several cellular-level regulatory processes as competing endogenous RNAs (ceRNAs) that play an important role in the development of liver fibrosis. A variety of lncRNAs have also been shown to contribute to the altered cell cycle, proliferation profile associated with the accelerated development of liver fibrosis. This review aims to discuss the functions and mechanisms of lncRNAs in the development and regression of liver fibrosis, to explore the major lncRNAs involved in the signaling pathways regulating liver fibrosis, to elucidate the mechanisms mediated by lncRNA dysregulation and to provide new diagnostic and therapeutic strategies for liver fibrosis.

Tumor immune microenvironment lncRNAs

Long non-coding ribonucleic acids (RNAs) (lncRNAs) are key players in tumorigenesis and immune responses. The nature of their cell type-specific gene expression and other functional evidence support the idea that lncRNAs have distinct cellular functions in the tumor immune microenvironment (TIME). To date, the majority of lncRNA studies have heavily relied on bulk RNA-sequencing data in which various cell types contribute to an averaged signal, limiting the discovery of cell type-specific lncRNA functions. Single-cell RNA-sequencing (scRNA-seq) is a potential solution for tackling this limitation despite the lack of annotations for low abundance yet cell type-specific lncRNAs. Hence, updated annotations and further understanding of the cellular expression of lncRNAs will be necessary for characterizing cell type-specific functions of lncRNA genes in the TIME. In this review, we discuss lncRNAs that are specifically expressed in tumor and immune cells, summarize the regulatory functions of the lncRNAs at the cell type level and highlight how a scRNA-seq approach can help to study the cell type-specific functions of TIME lncRNAs.

ALKBH5 Facilitates Hypoxia-Induced Paraspeckle Assembly and IL8 Secretion to Generate an Immunosuppressive Tumor Microenvironment

The dynamic changes of RNA N6-methyl-adenosine (m⁶A) during cancer progression contribute to quick adaption to microenvironmental changes. Here, we profiled the cancer cell m⁶A dynamics in the hypoxic tumor niche and its pathological consequences in glioblastoma multiforme (GBM). The m⁶A demethylase ALKBH5 was induced in GBM models under hypoxic conditions and was associated with a hypoxic gene signature in GBM patient samples. Depletion or inactivation of ALKBH5 in GBM cells significantly suppressed hypoxia-induced tumor-associated macrophage (TAM) recruitment and immunosuppression in allograft tumors. Expression and secretion of CXCL8/IL8 were significantly suppressed in ALKBH5-deficient tumors. However, ALKBH5 did not regulate CXCL8 m⁶A directly. Instead, hypoxia-induced ALKBH5 erased m⁶A deposition from the lncRNA NEAT1, stabilizing the transcript and facilitating NEAT1-mediated paraspeckle assembly, which led to relocation of the transcriptional repressor SFPQ from the CXCL8 promoter to paraspeckles and, ultimately, upregulation of CXCL8/IL8 expression. Accordingly, ectopic expression of CXCL8 in ALKBH5-deficient GBM cells partially restored TAM recruitment and tumor progression. Together, this study links hypoxia-induced epitranscriptomic changes to the emergence of an immunosuppressive microenvironment facilitating tumor evasion. SIGNIFICANCE: Hypoxia induces tumor immune microenvironment remodeling through an ALKBH5-mediated epigenetic and epitranscriptomic mechanism, providing potential immunotherapeutic strategies for treating glioblastoma.

Substrate Stiffness Drives Epithelial to Mesenchymal Transition and Proliferation through the NEAT1-Wnt/β-Catenin Pathway in Liver Cancer

Background: Extracellular matrix (ECM)-derived mechanical stimuli regulate many cellular processes and phenotypes through mechanotransduction signaling pathways. Substrate stiffness changes cell phenotypes and promotes angiogenesis, epithelial to mesenchymal transition (EMT), and metastasis in tumors. Enhanced liver tissue matrix stiffness plays a crucial role in the tumorigenesis and malignant development of liver cancer and is associated with unfavorable survival outcomes. However, how liver cancer cells sense changes in ECM stiffness and the underlying molecular mechanisms are largely unknown. Methods: Seeding HepG2 cells on the micropillar gels, HepG2 cells were assessed for responsiveness to mechanotransduction using Western blot and immunofluorescence. Conclusions: We found that higher substrate stiffness dramatically enhanced malignant cell phenotypes and promoted G1/S transition in HepG2 cells. Furthermore, nuclear paraspeckle assembly transcript 1 (NEAT1) was identified as a matrix stiffness-responsive long non-coding RNA (lncRNA) regulating proliferation and EMT in response to increasing matrix stiffness during the progression of HepG2 cells towards liver cancer phenotypes. Higher matrix stiffness contributed to enhancing NEAT1 expression, which activated the WNT/β-catenin pathway. β-catenin translocates and enters the nucleus and the EMT transcription factor zinc finger E-box binding homeobox 1 (ZEB1) was upregulated to trigger EMT. Additionally, the proteins required for matrix stiffness-induced proliferation and resistance were strikingly upregulated in HepG2 cells. Therefore, our findings provide evidence that ECM-derived mechanical signals regulate cell proliferation and drive EMT through a NEAT1/WNT/β-catenin mechanotransduction pathway in the tumor microenvironment of liver cancer.

Implication of long non-coding RNA NEAT1 in the pathogenesis of bacterial meningitis-induced blood-brain barrier damage

PURPOSE

Blood-brain barrier (BBB) damage is closely related to various neurological disorders, including bacterial meningitis (BM). Determining a reliable strategy to prevent BBB damage in the context of infection would be highly desirable. In the present study, we investigated the implications of the long non-coding RNA (lncRNA) nuclear paraspeckle assembly transcript 1 (NEAT1) in moderating BBB damage.

METHODS

In vitro BBB models were developed by co-culturing hCMEC/D3 cells with glioma cells, whereupon the glioma-exposed endothelial cells (GECs) were treated with a series of mimics, inhibitors, overexpression plasmids, and shRNAs for evaluating whether NEAT1, microRNA-135a (miR-135a) and hypoxia-inducible factor 1α (HIF1α) mediated BBB integrity and permeability. Furthermore, the in vivo biological function of NEAT1 was validated in a mouse model of BBB damage.

RESULTS

NEAT1 and HIF1α were determined to be up-regulated, while miR-135a was under-expressed in GECs. As demonstrated by chromatin immunoprecipitation and dual-luciferase reporter assays, NEAT1 could bind to miR-135a, and HIF1α was confirmed as a target of miR-135a. Either overexpression of NEAT1 or depletion of miR-135a impaired the integrity and augmented the permeability of BBB. However, HIF1α silencing could reverse the BBB damage induced by NEAT1 overexpression or by inhibition of miR-135a. In vivo experiments substantiated that knockdown of NEAT1 could alleviate BBB damage in living mice.

CONCLUSIONS

Hence, NEAT1 knockdown prevents BBB disruption and exerts promise as a potential target for BM treatment.

The role of hypoxia-induced long noncoding RNAs (lncRNAs) in tumorigenesis and metastasis

Long noncoding RNAs (lncRNAs) are noncoding RNAs with length greater than 200 nt. The biological roles and mechanisms mediated by lncRNAs have been extensively investigated. Hypoxia is a proven microenvironmental factor that promotes solid tumor metastasis. Epithelial-mesenchymal transition (EMT) is one of the major mechanisms induced by hypoxia to contribute to metastasis. Many lncRNAs have been shown to be induced by hypoxia and their roles have been delineated. In this review, we focus on the hypoxia-inducible lncRNAs that interact with protein/protein complex and chromatin/epigenetic factors, and the mechanisms that contribute to metastasis. The role of a recently discovered lncRNA RP11-390F4.3 in hypoxia-induced EMT is discussed. Whole genome approaches to delineating the association between lncRNAs and histone modifications are discussed. Other topics related to hypoxia-induced tumor progression but require further investigation are also mentioned. The clinical significance and treatment strategy targeted against lncRNAs are discussed. The review aims to identify suitable lncRNA targets that may provide feasible therapeutic venues for hypoxia-involved cancers.

Heterogeneous graph attention network based on meta-paths for lncRNA-disease association prediction

MOTIVATION

Discovering long noncoding RNA (lncRNA)-disease associations is a fundamental and critical part in understanding disease etiology and pathogenesis. However, only a few lncRNA-disease associations have been identified because of the time-consuming and expensive biological experiments. As a result, an efficient computational method is of great importance and urgently needed for identifying potential lncRNA-disease associations. With the ability of exploiting node features and relationships in network, graph-based learning models have been commonly utilized by these biomolecular association predictions. However, the capability of these methods in comprehensively fusing node features, heterogeneous topological structures and semantic information is distant from optimal or even satisfactory. Moreover, there are still limitations in modeling complex associations between lncRNAs and diseases.

RESULTS

In this paper, we develop a novel heterogeneous graph attention network framework based on meta-paths for predicting lncRNA-disease associations, denoted as HGATLDA. At first, we conduct a heterogeneous network by incorporating lncRNA and disease feature structural graphs, and lncRNA-disease topological structural graph. Then, for the heterogeneous graph, we conduct multiple metapath-based subgraphs and then utilize graph attention network to learn node embeddings from neighbors of these homogeneous and heterogeneous subgraphs. Next, we implement attention mechanism to adaptively assign weights to multiple metapath-based subgraphs and get more semantic information. In addition, we combine neural inductive matrix completion to reconstruct lncRNA-disease associations, which is applied for capturing complicated associations between lncRNAs and diseases. Moreover, we incorporate cost-sensitive neural network into the loss function to tackle the commonly imbalance problem in lncRNA-disease association prediction. Finally, extensive experimental results demonstrate the effectiveness of our proposed framework.

The emerging landscape of long non-coding RNAs in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common and aggressive cancers. HCC shows high prevalence and lethality caused by a variety of etiologic factors. However, the underlying mechanisms and the diagnostic markers identifying patients at risk in advance has not been entirely elucidated. Long non-coding RNAs (lncRNAs) are a subgroup of non-coding RNAs greater than 200 nucleotides in length with no protein-coding capability. With the progress in sequencing technologies and bioinformatic tools, the landscape of lncRNAs is being revealed. Numerous discoveries point out that lncRNAs participate in HCC carcinogenesis and metastasis through altering cell proliferation and invasion ability, apoptosis, and chemo- or radio-sensitivity. Moreover, lncRNA is easy to detect compared to the traditional diagnostic methods. This review summarizes the mechanisms of major lncRNAs in HCC discovered in recent years and lncRNAs as early diagnostic markers for HCC.

Hepatitis B Virus DNA Integration, Chronic Infections and Hepatocellular Carcinoma

Hepatitis B Virus (HBV) is an Old World virus with a high mutation rate, which puts its origins in Africa alongside the origins of Homo sapiens, and is a member of the Hepadnaviridae family that is characterized by a unique viral replication cycle. It targets human hepatocytes and can lead to chronic HBV infection either after acute infection via horizontal transmission usually during infancy or childhood or via maternal-fetal transmission. HBV has been found in ~85% of HBV-related Hepatocellular Carcinomas (HCC), and it can integrate the whole or part of its genome into the host genomic DNA. The molecular mechanisms involved in the HBV DNA integration is not yet clear; thus, multiple models have been described with respect to either the relaxed-circular DNA (rcDNA) or the double-stranded linear DNA (dslDNA) of HBV. Various genes have been found to be affected by HBV DNA integration, including cell-proliferation-related genes, oncogenes and long non-coding RNA genes (lincRNAs). The present review summarizes the advances in the research of HBV DNA integration, focusing on the evolutionary and molecular side of the integration events along with the arising clinical aspects in the light of WHO's commitment to eliminate HBV and viral hepatitis by 2030.

The role of G-Quadruplex DNA in Paraspeckle formation in cancer

Paraspeckles are RNA-protein structures within the nucleus of mammalian cells, capable of orchestrating various biochemical processes. An overexpression of the architectural component of paraspeckles, a long non-coding RNA called NEAT1 (Nuclear Enriched Abundant Transcript 1), has been linked to a variety of cancers and is often associated with poor patient prognosis. Thus, there is an accumulating interest in the role of paraspeckles in carcinogenesis, however there is a limited understanding of how NEAT1 expression is regulated. Here, we demonstrate that both nuclear G-quadruplex (G4) and paraspeckle formation are significantly increased in a human breast cancer cell line compared to non-tumorigenic breast cells. Moreover, we identified and characterized G4-forming sequences within the NEAT1 promoter and demonstrate stabilization of G4 DNA with a G4-stabilizing small molecule results in a significant alteration in both paraspeckle formation and NEAT1 expression. This G4-mediated alteration of NEAT1 at both the transcriptional and post-transcriptional levels was evident in U2OS osteosarcoma cells, MCF-7 breast adenocarcinoma and MDA-MB-231 triple negative breast cancer cells.

From Junk to Function: LncRNAs in CNS Health and Disease

Recent advances in RNA sequencing technologies helped to uncover the existence of tens of thousands of long non-coding RNAs (lncRNAs) that arise from the dark matter of the genome. These lncRNAs were originally thought to be transcriptional noise but an increasing number of studies demonstrate that these transcripts can modulate protein-coding gene expression by a wide variety of transcriptional and post-transcriptional mechanisms. The spatiotemporal regulation of lncRNA expression is particularly evident in the central nervous system, suggesting that they may directly contribute to specific brain processes, including neurogenesis and cellular homeostasis. Not surprisingly, lncRNAs are therefore gaining attention as putative novel therapeutic targets for disorders of the brain. In this review, we summarize the recent insights into the functions of lncRNAs in the brain, their role in neuronal maintenance, and their potential contribution to disease. We conclude this review by postulating how these RNA molecules can be targeted for the treatment of yet incurable neurological disorders.