The long noncoding RNA SNHG1 promotes tumor growth through regulating transcription of both local and distal genes

microRNA 21 and long non-coding RNAs interplays underlie cancer pathophysiology: A narrative review

Non-coding RNAs (ncRNAs) are a diverse group of functional RNA molecules that lack the ability to code for proteins. Despite missing this traditional role, ncRNAs have emerged as crucial regulators of various biological processes and have been implicated in the development and progression of many diseases, including cancer. MicroRNAs (miRNAs) and long non-coding RNAs (lncRNAs) are two prominent classes of ncRNAs that have emerged as key players in cancer pathophysiology. In particular, miR-21 has been reported to exhibit oncogenic roles in various forms of human cancer, including prostate, breast, lung, and colorectal cancer. In this context, miR-21 overexpression is closely associated with tumor proliferation, growth, invasion, angiogenesis, and chemoresistance, whereas miR-21 inactivation is linked to the regression of most tumor-related processes. Accordingly, miR-21 is a crucial modulator of various canonical oncogenic pathways such as PTEN/PI3K/Akt, Wnt/β-catenin, STAT, p53, MMP2, and MMP9. Moreover, interplays between lncRNA and miRNA further complicate the regulatory mechanisms underlying tumor development and progression. In this regard, several lncRNAs have been found to interact with miR-21 and, by functioning as competitive endogenous RNAs (ceRNAs) or miRNA sponges, can modulate cancer tumorigenesis. This work presents and discusses recent findings highlighting the roles and pathophysiological implications of the miR-21-lncRNA regulatory axis in cancer occurrence, development, and progression. The data collected indicate that specific lncRNAs, such as MEG3, CASC2, and GAS5, are strongly associated with miR-21 in various types of cancer, including gastric, cervical, lung, and glioma. Indeed, these lncRNAs are well-known tumor suppressors and are commonly downregulated in different types of tumors. Conversely, by modulating various mechanisms and oncogenic signaling pathways, their overexpression has been linked with preventing tumor formation and development. This review highlights the significance of these regulatory pathways in cancer and their potential for use in cancer therapy as diagnostic and prognostic markers.

Critical role of miR-21/exosomal miR-21 in autophagy pathway

Activation of autophagy, a process of cellular stress response, leads to the breakdown of proteins, organelles, and other parts of the cell in lysosomes, and can be linked to several ailments, such as cancer, neurological diseases, and rare hereditary syndromes. Thus, its regulation is very carefully monitored. Transcriptional and post-translational mechanisms domestically or in whole organisms utilized to control the autophagic activity, have been heavily researched. In modern times, microRNAs (miRNAs) are being considered to have a part in post-translational orchestration of the autophagic activity, with miR-21 as one of the best studied miRNAs, it is often more than expressed in cancer cells. This regulatory RNA is thought to play a major role in a plethora of processes and illnesses including growth, cancer, cardiovascular disease, and inflammation. Different studies have suggested that a few autophagy-oriented genes, such as PTEN, Rab11a, Atg12, SIPA1L2, and ATG5, are all targeted by miR-21, indicating its essential role in the regulation.

LncRNA SNHG26 promotes gastric cancer progression and metastasis by inducing c-Myc protein translation and an energy metabolism positive feedback loop

Metastasis is a bottleneck in cancer treatment. Studies have shown the pivotal roles of long noncoding RNAs (lncRNAs) in regulating cancer metastasis; however, our understanding of lncRNAs in gastric cancer (GC) remains limited. RNA-seq was performed on metastasis-inclined GC tissues to uncover metastasis-associated lncRNAs, revealing upregulated small nucleolar RNA host gene 26 (SNHG26) expression, which predicted poor GC patient prognosis. Functional experiments revealed that SNHG26 promoted cellular epithelial-mesenchymal transition and proliferation in vitro and in vivo. Mechanistically, SNHG26 was found to interact with nucleolin (NCL), thereby modulating c-Myc expression by increasing its translation, and in turn promoting energy metabolism via hexokinase 2 (HK2), which facilitates GC malignancy. The increase in energy metabolism supplies sufficient energy to promote c-Myc translation and expression, forming a positive feedback loop. In addition, metabolic and translation inhibitors can block this loop, thus inhibiting cell proliferation and mobility, indicating potential therapeutic prospects in GC.

The Link of mRNA and rRNA Transcription by PUF60/FIR through TFIIH/P62 as a Novel Therapeutic Target for Cancer

The interaction between mRNA and ribosomal RNA (rRNA) transcription in cancer remains unclear. RNAP I and II possess a common N-terminal tail (NTT), RNA polymerase subunit RPB6, which interacts with P62 of transcription factor (TF) IIH, and is a common target for the link between mRNA and rRNA transcription. The mRNAs and rRNAs affected by FUBP1-interacting repressor (FIR) were assessed via RNA sequencing and qRT-PCR analysis. An FIR, a c-myc transcriptional repressor, and its splicing form FIRΔexon2 were examined to interact with P62. Protein interaction was investigated via isothermal titration calorimetry measurements. FIR was found to contain a highly conserved region homologous to RPB6 that interacts with P62. FIRΔexon2 competed with FIR for P62 binding and coactivated transcription of mRNAs and rRNAs. Low-molecular-weight chemical compounds that bind to FIR and FIRΔexon2 were screened for cancer treatment. A low-molecular-weight chemical, BK697, which interacts with FIRΔexon2, inhibited tumor cell growth with rRNA suppression. In this study, a novel coactivation pathway for cancer-related mRNA and rRNA transcription through TFIIH/P62 by FIRΔexon2 was proposed. Direct evidence in X-ray crystallography is required in further studies to show the conformational difference between FIR and FIRΔexon2 that affects the P62-RBP6 interaction.

Amino acid metabolism regulated by lncRNAs: the propellant behind cancer metabolic reprogramming

Metabolic reprogramming is one of the main characteristics of cancer cells and plays pivotal role in the proliferation and survival of cancer cells. Amino acid is one of the key nutrients for cancer cells and many studies have focused on the regulation of amino acid metabolism, including the genetic alteration, epigenetic modification, transcription, translation and post-translational modification of key enzymes in amino acid metabolism. Long non-coding RNAs (lncRNAs) are composed of a heterogeneous group of RNAs with transcripts of more than 200 nucleotides in length. LncRNAs can bind to biological molecules such as DNA, RNA and protein, regulating the transcription, translation and post-translational modification of target genes. Now, the functions of lncRNAs in cancer metabolism have aroused great research interest and significant progress has been made. This review focuses on how lncRNAs participate in the reprogramming of amino acid metabolism in cancer cells, especially glutamine, serine, arginine, aspartate, cysteine metabolism. This will help us to better understand the regulatory mechanism of cancer metabolic reprogramming and provide new ideas for the development of anti-cancer drugs. Video Abstract.

circMMD reduction following tumor treating fields inhibits glioblastoma progression through FUBP1/FIR/DVL1 and miR-15b-5p/FZD6 signaling

BACKGROUND

Tumor treating fields (TTF) is the latest treatment for GBM. Circular RNA (circRNA) has been demonstrated to play critical roles in tumorigenesis. However, the molecular mechanism of TTF remained largely unknown and the role of circRNA in TTF was not reported. The aim of this study was to elucidate the role and mechanism of circMMD in TTF treatment of GBM.

METHODS

Divergent primer was designed to verify the existence of circMMD in GBM cells. The prognostic role of circMMD was explored in glioma specimens. The knockdown and overexpressed plasmids were used to evaluate the effect of circMMD on GBM cell proliferation and TTF efficacy. RNA pull-down and RNA immunoprecipitation were performed to identify binding proteins of circMMD. Subcutaneous and intracranial tumor models were established to validate findings in vivo.

RESULTS

The expression of circMMD was elevated in GBM and its high expression indicated poor prognoses. TTF intervention could reduce circMMD synthesis, which suppressed GBM proliferation and increased TTF-mediated apoptosis. The reduction of circMMD promoted the interaction between FUBP1 and FIR, which decreased DVL1 transcription. Meanwhile, decreased circMMD would promote the activity of miR-15b-5p to degrade FZD6. Finally, the diminished expression of DVL1 and FZD6 expression suppressed the activation of Wnt/β-catenin pathway.

CONCLUSIONS

Our study revealed a novel mechanism of TTF that TTF-mediated reduction of circMMD could inhibit Wnt/β-catenin pathway to suppress GBM proliferation.

LncRNA SNHG1 Facilitates Tumor Proliferation and Represses Apoptosis by Regulating PPARγ Ubiquitination in Bladder Cancer

Simple Summary

Our study elucidated that SNHG1 promotes MDM2 expression by binding to miR-9-3p to promote PPARγ ubiquitination and downregulate PPARγ expression and that SNHG1 plays an important role in bladder cancer and provides a potential therapeutic target for bladder cancer.

Abstract

Background: Long noncoding RNAs regulate various biological effects in the progression of cancers. We found that the expression of SNHG1 was significantly up-regulated in bladder cancer after analyzing data obtained from TCGA and GEO. However, the potential role of SNHG1 remains to be investigated in bladder cancer. It was validated that SNHG1 was overexpressed in bladder cancer tissues detected by qRT-PCR and FISH, which was also associated with poor clinical outcome. Additionally, SNHG1 was verified to facilitate tumor proliferation and repress apoptosis in vitro and in vivo. Results: SNHG1 could act as a competitive endogenous RNA and decrease the expression of murine double minute 2 (MDM2) by sponging microRNA-9-3p. Furthermore, MDM2 induced ubiquitination and degradation of PPARγ that contributed to the development of bladder cancer. Conclusions: the study elucidated that SNHG1 played an important role in bladder cancer and provided a potential therapeutic target for bladder cancer.

LncRNA SNHG25 Promotes Glioma Progression Through Activating MAPK Signaling

Numerous studies indicated that long non-coding RNAs (lncRNAs) play critical roles in glioma initiation and progression. SNHG25 is a newly identified lncRNA. And the functional role and molecular mechanism of SNHG25 in glioma cells have not been investigated. In this study, we found that SNHG25 was upregulated in glioma cells and tissues. CCK-8, EDU, and colony formation assays demonstrated that SNHG25 knockdown markedly inhibited glioma cell proliferation. In vivo studies showed that SNHG25 knockdown significantly inhibited tumor growth. Further studies indicated that SNHG25 positively regulated MAP2K2 through sponging miR-579-5p. High expression of SNHG25 activated MAPK signaling through MAP2K2. These data suggest that SNHG25 is a potential target and biomarker for glioma.

Integrative Analysis and Experimental Validation Indicated That SNHG17 Is a Prognostic Marker in Prostate Cancer and a Modulator of the Tumor Microenvironment via a Competitive Endogenous RNA Regulatory Network

The incidence of prostate cancer (PC) is growing rapidly worldwide, and studies uncovering the molecular mechanisms driving the progression and modulating the immune infiltration and antitumor immunity of PC are urgently needed. The long noncoding RNA SNHG family has been recognized as a prognostic marker in cancers and contributes to the progression of multiple cancers, including PC. In this study, we aimed to clarify the prognostic values and underlying mechanisms of SNHGs in promoting the progression and modulating the tumor microenvironment of PC through data mining based on The Cancer Genome Atlas (TCGA) database. We identified that within the SNHG family, SNHG17 was most correlated with the overall survival of PC patients and could act as an independent predictor. Moreover, we constructed a competitive endogenous RNA (ceRNA) network by which SNHG17 promotes progression and potentially inhibits the immune infiltration and immune response of prostate cancer. By interacting with miR-23a-3p/23b-3p/23c, SNHG17 upregulates the expression of UBE2M and OTUB1, which have been demonstrated to play critical roles in the tumorigenesis of human cancers, more importantly promoting cancer cell immunosuppression and resistance to cytotoxic stimulation. Finally, we examined the correlation between SNHG17 expression and the clinical progression of PC patients based on our cohort of 52 PC patients. We also verified the SNHG17/miR-23a/OTUB1 axis in RV-1 and PC-3 cells by dual luciferase and RIP assays, and we further identified that SNHG17 promoted cellular invasive capacity by modulating OTUB1. In summary, the current study conducted a ceRNA-based SNHG17-UBE2M/OTUB1 axis and indicated that SNHG17 might be a novel prognostic factor associated with the progression, immunosuppression, and cytotoxic resistance of PC.

Major Role for Cellular MicroRNAs, Long Noncoding RNAs (lncRNAs), and the Epstein-Barr Virus-Encoded BART lncRNA during Tumor Growth In Vivo

This study assessed the effects of Epstein-Barr virus (EBV) and one form of virally encoded BART long noncoding RNAs (lncRNAs) on cellular expression in epithelial cells grown in vitro and as tumors in vivo determined by high-throughput RNA sequencing of mRNA and small RNAs. Hierarchical clustering based on gene expression distinguished the cell lines from the tumors and distinguished the EBV-positive tumors and the BART tumors from the EBV-negative tumors. EBV and BART expression also induced specific expression changes in cellular microRNAs (miRs) and lncRNAs. Multiple known and predicted targets of the viral miRs, the induced cellular miRs, and lncRNAs were identified in the altered gene set. The changes in expression in vivo indicated that the suppression of growth pathways in vivo reflects increased expression of cellular miRs in all tumors. In the EBV and BART tumors, many of the targets of the induced miRs were not changed and the seed sequences of the nonfunctional miRs were found to have homologous regions within the BART lncRNA. The inhibition of these miR effects on known targets suggests that these induced miRs have reduced function due to sponging by the BART lncRNA. This composite analysis identified the effects of EBV on cellular miRs and lncRNAs with a functional readout through identification of the simultaneous effects on gene expression. Major shifts in gene expression in vivo are likely mediated by effects on cellular noncoding RNAs. Additionally, a predicted property of the BART lncRNA is to functionally inhibit the induced cellular miRs.

lncRNA SNHG26 promoted the growth, metastasis, and cisplatin resistance of tongue squamous cell carcinoma through PGK1/Akt/mTOR signal pathway

Tongue squamous cell carcinoma (TSCC) is closely linked to head and neck cancers. Here, we sought to explore the role and mechanism of lncRNAs in the occurrence and progression of TSCC and cisplatin resistance. The results of next-generation transcriptomic sequencing revealed that lncRNA-SNHG26 was differentially expressed and was associated with TSCC cisplatin resistance. The Cancer Genome Atlas dataset and tumor tissue analysis revealed that high SHNG26 expression was associated with the occurrence, progression, and poor prognosis of TSCC. Evidence from cell and animal experiments showed that SNHG26 expression was positively correlated with TSCC proliferation, epithelial-mesenchymal transformation, migration, invasion, and cisplatin resistance. Furthermore, in TSCC cells, SNHG26 was found to bind directly to the PGK1 protein, inhibiting its ubiquitination and activating the Akt/mTOR signaling pathway. These findings suggest that lncRNA-SNHG26 may be a promising target for inhibiting TSCC progression and improving sensitivity to cisplatin chemotherapy in TSCC.

Regulation of Ferroptosis by Non-Coding RNAs in Head and Neck Cancers

Ferroptosis is a newly identified mode of programmed cell death characterized by iron-associated accumulation of lipid peroxides. Emerging research on ferroptosis has suggested its implication in tumorigenesis and stemness of cancer. On the other hand, non-coding RNAs have been shown to play a pivotal role in the modulation of various genes that affect the progression of cancer cells and ferroptosis. In this review, we summarize recent advances in the theoretical modeling of ferroptosis and its relationship between non-coding RNAs and head and neck cancers. Aside from the significance of ferroptosis-related non-coding RNAs in prognostic relevance, we also review how these non-coding RNAs participate in the regulation of iron, lipid metabolism, and reactive oxygen species accumulation. We aim to provide a thorough grounding in the function of ferroptosis-related non-coding RNAs based on current knowledge in an effort to develop effective therapeutic strategies for head and neck cancers.

Long non-coding RNA SNHG1 promotes bladder cancer progression by upregulating EZH2 and repressing KLF2 transcription

OBJECTIVE

Long Non-Coding RNAs (LncRNAs) act as an indispensable role in cancer development. The study aimed to investigate the role and mechanism of lncRNA Small Nucleolar RNA Host Gene 1 (SNHG1) in Bladder Cancer (BC) progression.

METHOD

The expression, prognostic value, diagnostic value, and correlation of SNHG1, Enhancer of Zeste 2 polycomb repressive complex 2 subunit (EZH2), and Kruppel Like Factor 2 (KLF2) were analyzed through bioinformatics analysis. The expression was also validated in BC tissues and cell lines. Besides, their regulation and binding were tested via qPCR, Western blot, Dual-Luciferase Reporter Assay (DLRA), Argonaute RISC catalytic component 2-RNA Immunoprecipitation (AGO2-RIP), and Chromatin Immunoprecipitation (ChIP). A xenograft model in nude mice was also established.

RESULTS

SNHG1 was significantly overexpressed in BC tissues and cells. Importantly, SNHG1 was associated with poor survival, and ROC curves revealed high diagnostic values. Moreover, by CCK8, wound healing, transwell, and Western blot analysis, SNHG1 knockdown significantly inhibited the proliferation, migration, invasion, and epithelial-mesenchymal transition of BC cells. Additionally, in vivo experiments showed that silencing SNHG1 hindered tumorigenesis and tumor growth. Regarding mechanism, the results of AGO2-RIP, ChIP or DLRA showed that SNHG1 played different roles at diverse subcellular sites. In the cytoplasm, SNHG1 acted as a competing endogenous RNA for miR-137-3p to promote EZH2 expression. In the nucleus, SNHG1 could interact with EZH2 to inhibit KLF2 transcription.

CONCLUSION

Our study elucidated that SNHG1 formed a regulatory network and played an oncogenic role in BC, which provided a novel therapeutic target for BC treatment.

Long non-coding RNA SNHG1 promotes fibroblast-to-myofibroblast transition during the development of pulmonary fibrosis induced by silica particles exposure

Inhaling silica dust in the environment can cause progressive pulmonary fibrosis, then silicosis. Silicosis is the most harmful occupational disease in the world, so the study of the mechanism is of great significance for the prevention and treatment of silicosis. Long non-coding RNAs (lncRNAs) are important players in the pathological process of fibrotic diseases. However, the function of specific lncRNA in regulating pulmonary fibrosis remains elusive. In this study, a mouse model of pulmonary fibrosis via intratracheal instillation of silica particles was established, and the differential expression of lnc-SNHG1 and miR-326 in lung tissues and TGF-β1-treated fibroblasts was detected by the qRT-PCR method. Short interfering RNA (siRNA) and plasmid were designed for knockdown or overexpression of lnc-SNHG1 in fibroblasts. MiRNA simulant was designed for overexpression of miR-326 in vivo and in vitro. Dual-luciferase reporter system, immunofluorescence, western blot, wound healing and transwell assay were performed to investigate the function and the underlying mechanisms of lnc-SNHG1. As a result, we found that lnc-SNHG1 was highly expressed in fibrotic lung tissues of mice and TGF-β1-treated fibroblasts. Moreover, the high expression of lnc-SNHG1 facilitated the migration and invasion of fibroblasts and the secretion of fibrotic molecules, while the low expression of lnc-SNHG1 exerted the opposite effects. Further mechanism studies showed that miR-326 was the potential target of lnc-SNHG1, and there is a negative correlation between the expression levels of lnc-SNHG1 and miR-326. Combined with mitigating fibrotic effects of miR-326 in a mouse model of silica particles exposure, we revealed that lnc-SNHG1 significantly sponged miR-326 and facilitated the expression of SP1, thus accelerating fibroblast-to-myofibroblast transition and synergistically promoting the development of pulmonary fibrosis. Our study uncovered a key mechanism by which lnc-SNHG1 regulated pulmonary fibrosis through miR-326/SP1 axis, and lnc-SNHG1 is a potential target for the prevention and treatment of silicosis.

LncRNA Snhg1-driven self-reinforcing regulatory network promoted cardiac regeneration and repair after myocardial infarction

Rationale: Most current cardiac regeneration approaches result in very limited cell division and little new cardiomyocyte (CM) mass. Positive feedback loops are vital for cell division, but their role in CM regeneration remains unclear. We aimed to determine whether the lncRNA small nucleolar RNA host gene 1 Snhg1 (Snhg1) could form a positive feedback loop with c-Myc to induce cardiac regeneration.

Methods: Quantitative PCR and in situ hybridization experiments were performed to determine the Snhg1 expression patterns in fetal and myocardial infarction (MI) hearts. Gain- and Loss-of-function assays were conducted to explore the effect of Snhg1 on cardiomyocyte (CM) proliferation and cardiac repair following MI. We further constructed CM-specific Snhg1 knockout mice to confirm the proliferative effect exerted by Snhg1 using CRISPR/Cas9 technology. RNA sequencing and RNA pulldown were performed to explore how Snhg1 mediated cardiac regeneration. Chromatin immunoprecipitation and luciferase reporter assays were used to demonstrate the positive feedback loop between Snhg1 and c-Myc.

Results: Snhg1 expression was increased in human and mouse fetal and myocardial infarction (MI) hearts, particularly in CMs. Overexpression of Snhg1 promoted CM proliferation, angiogenesis, and inhibited CM apoptosis after myocardial infarction, which further improved post-MI cardiac function. Antagonism of Snhg1 in early postnatal mice inhibited CM proliferation and impaired cardiac repair after MI. Mechanistically, Snhg1 directly bound to phosphatase and tensin homolog (PTEN) and induced PTEN degradation, activating the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) pathway to promote CM proliferation. The c-Myc protein, one of downstream targets of PI3K/AKT signaling, functioned as a transcription factor by binding to the promoter regions of Snhg1. Perturbation of the positive feedback between Snhg1 and c-Myc by mutation of the binding sequence significantly affected Snhg1-induced CM proliferation.

Conclusions: Snhg1 effectively elicited CM proliferation and improved cardiac function post-MI by forming a positive feedback loop with c-Myc to sustain PI3K/Akt signaling activation, and thus may be a promising cardiac regeneration strategy in treating heart failure post-MI.

Long noncoding RNA SNHG1 promotes TERT expression by sponging miR-18b-5p in breast cancer

BACKGROUND

Long noncoding RNA (lncRNA) small nucleolar RNA host gene 1 (SNHG1) plays a positive role in the progression of human malignant tumors. However, the molecular mechanism of SNHG1 remains elusive in breast cancer.

RESULTS

LncRNA SNHG1 was upregulated and had a positive relationship with poor prognosis according to bioinformatics analysis in pan-cancer including breast cancer. Silencing SNHG1 inhibited tumorigenesis in breast cancer both in vitro and in vivo. Mechanistically, SNHG1 functioned as a competing endogenous RNA (ceRNA) to promote TERT expression by sponging miR-18b-5p in breast cancer. miR-18b-5p acted as a tumor repressor in breast cancer. Moreover, the combination of SNHG1 knockdown and TERT inhibitor administration showed a synergistic inhibitory effect on breast cancer growth in vivo. Finally, E2F1 as a transcription factor, binding to SNHG1 promoter and enhanced SNHG1 transcription in breast cancer.

CONCLUSIONS

Our results provide a comprehensive understanding of the oncogenic mechanism of lncRNA SNHG1 in breast cancer. Importantly, we identified a novel E2F1-SNHG1-miR-18b-5p-TERT axis, which may be a potential therapeutic target for breast cancer. Our results also provided a potential treatment for breast cancer when knockdown SNHG1 and TERT inhibitor administration simultaneously.

Long non-coding RNA SNHG1 suppresses cell migration and invasion and upregulates SOCS2 in human gastric carcinoma

Gastric carcinoma (GC) is one of the most common malignancies and the third leading cause of cancer-related deaths worldwide. Long noncoding RNAs (lncRNAs) may be an important class of functional regulators involved in human gastric cancers development. In this study, we investigated the clinical significance and function of lncRNA SNHG1 in GC. SNHG1 was significantly downregulated in GC tumor tissues compared with adjacent noncancerous tissues. Overexpression of SNHG1 in BGC-823 cells remarkably inhibited not only cell proliferation, migration, invasion in vitro, but also tumorigenesis and lung metastasis in the chick embryo chorioallantoic membrane (CAM) assay in vivo. Conversely, inhibition of SNHG1 by transfection of siRNA in AGS cells resulted in opposite phenotype changes. Mechanically, SNHG1 was found interacted with ILF3, NONO and SFPQ. RNA-seq combined with bioinformatic analysis identified a serial of downstream genes of SNHG1, including SOCS2, LOXL2, LTBP3, LTBP4. Overexpression of SNHG1 induced SOCS2 expression whereas knockdown of SNHG1 decreased SOCS2 expression. In addition, knockdown of SNHG1 promoted the activation of JAK2/STAT signaling pathway. Taken together, our data suggested that SNHG1 suppressed aggressive phenotype of GC cells and regulated SOCS2/JAK2/STAT pathway.

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SNHG1 was significantly downregulated in GC tumor tissues.

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SNHG1 suppressed proliferation and migration of GC cells.

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SNHG1 localized in nucleus of GC cells and interacted with ILF3, NONO and SFPQ.

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SNHG1 regulate SOCS2 expression in GC cell lines and JAK2/STAT signaling pathway in AGS cells.

The circACTN4 interacts with FUBP1 to promote tumorigenesis and progression of breast cancer by regulating the expression of proto-oncogene MYC

Background

Recent studies have revealed that circular RNAs (circRNAs) play significant roles in the occurrence and development of many kinds of cancers including breast cancer (BC). However, the potential functions of most circRNAs and the molecular mechanisms underlying progression of BC remain elusive.

Method

Here, Circular RNA microarray was executed in 4 pairs of breast cancer tissues and para-cancer tissues. The expression and prognostic significance of circACTN4 in BC cells and tissues were determined by qRT-PCR and in situ hybridization. Gain-and loss-of-function experiments were implemented to observe the impacts of circACTN4 on the growth, invasion, and metastasis of BC cells in vitro and in vivo. Mechanistically, chromatin immunoprecipitation, luciferase reporter, RNA pulldown, mass spectrum, RNA immunoprecipitation, fluorescence in situ hybridization and co-immunoprecipitation assays were executed.

Results

CircACTN4 was significantly upregulated in breast cancer tissues and cells, its expression was correlated with clinical stage and poor prognosis of patients with BC. Ectopic expression of circACTN4 strikingly facilitated the growth, invasion, and metastasis of breast cancer cells in vitro and in vivo. Whereas knockdown of circACTN4 revealed opposite roles. CircACTN4 was mainly distributed in the nucleus. Further mechanistic research proved that circACTN4 could competitively bind to far upstream element binding protein 1 (FUBP1) to prevent the combination between FUBP1 and FIR, thereby activating MYC transcription and facilitating tumor progression of breast cancer. Furthermore, we found that upstream transcription factor 2 (USF2) might promote the biogenesis of circACTN4.

Conclusion

Our findings uncover a pivotal mechanism that circACTN4 mediated by USF2 might interact with FUBP1 to promote the occurrence and development of breast cancer via enhancing the expression of MYC. CircACTN4 could be a novel potential target for diagnosis and treatment of breast cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-021-01383-x.

Small nucleolar RNA host gene 8: A rising star in the targets for cancer therapy

Long non-coding RNAs (lncRNAs) are a group of transcripts that have been considered essential participants in cancer pathogenesis and progression over the past few decades. Small nucleolar RNA host gene 8 (SNHG8) is a newly discovered lncRNA that belongs to the SNHG family, a group of transcripts that can be processed into small nucleolar RNAs and exert important biological functions. As an oncogenic factor, SNHG8 is upregulated in multiple cancer types. Herein, we summarize the biological role of SNHG8 in different cancer types and the underlying mechanisms related to the interaction between SNHG8 and microRNAs, mRNAs, and proteins. In addition, this study emphasizes the clinical value of SNHG8 in cancer, hoping to provide new insights into cancer diagnosis, prognosis, and treatment.

Differentially Expressed Long Noncoding RNAs Involved in FUBP1 Promoting Hepatocellular Carcinoma Cells Proliferation

Background

Far upstream element-binding protein 1 (FUBP1) is reported to be involved in cancer development by regulating the transcription of c-myc gene through binding to far upstream element. Highly expressed FUBP1 was negatively correlated with survival rate of patients with hepatocellular carcinoma (HCC) and could promote the proliferation of HCC cells. However, the downstream mechanism of FUBP1 has not yet been clearly explained. This study is aimed at identifying the expression profiles of long noncoding RNA (lncRNA) in HCC cells in response to FUBP1 overexpression and at investigating the possible lncRNAs that participated in cell proliferation process regulated by FUBP1.

Methods

The overexpression of FUBP1 was mediated by lentiviral infection on 3 different types of HCC cell lines (MHCC97-H, MHCC97-L, and Huh-7). The expression of target genes was detected by quantitative reverse transcription-PCR (RT-PCR) and western blotting assays. Microarray and quantitative RT-PCR were applied to screen the differentially expressed lncRNAs in HCC cells after FUBP1 overexpression. The Cell Counting Kit-8 assay was used to confirm the growth vitality of HCC cells.

Results

The growth vitality of HCC cells was significantly increased after lentivirus infection. A total of 12 lncRNAs had the same expression trend in the 3 HCC cell lines in response to FUBP1 overexpression, including 3 upregulated lncRNAs and 9 downregulated lncRNAs. Coexpression analysis of dysregulated lncRNAs-mRNAs network showed that lnc-LYZ-2 was the lncRNA most relevant to FUBP1. Inhibition of lnc-LYZ-2 could significantly relieve the proproliferation effect of FUBP1 on HCC cells, suggesting that lnc-LYZ-2 was partially involved in proproliferation regulation of FUBP1.

Conclusions

Our results indicated that FUBP1 induced the abnormal expression of lncRNAs and the FUBP1-lncRNAs coexpression network in HCC cells, which could provide theoretical and experimental basis for FUBP1-lncRNAs network involved in HCC development.

Knockdown of Long Non-coding RNA SNGH3 by CRISPR-dCas9 Inhibits the Progression of Bladder Cancer

Recent research evidence documents that lncRNAs (long non-coding RNAs lncRNAs) play a pivotal role in the tumorigenesis and development of tumors. LncRNA SNGH3 (small nucleolar RNA host gene 3) is highly expressed in numerous forms of cancer, serving as an oncogene in cancer progression. Nonetheless, the clinical relationship, along with the mechanism of SNGH3 in bladder cancer, have not been studied. Herein, the findings exhibited upregulation of SNGH3 in bladder cancer tissues, along with the cell lines. Furthermore, overexpressed SNGH3 was positively linked to the TNM stage, as well as the histological grade of bladder cancer. Moreover, the silencing of SNGH3, using CRISPR-dCas9, suppressed cell growth along with migration, but elevated bladder cancer cell apoptosis. In summary, we established that SNGH3 serves as a bladder cancer oncogene and could be employed as a prospective diagnostic marker for clinical use, and is also a therapeutic target for CRISPR-mediated gene therapy.

Roles of Non-Coding RNAs in Cervical Cancer Metastasis

Metastasis remains to be a huge challenge in cancer therapy. The mechanism underlying cervical cancer metastasis is not well understood and needs to be elucidated. Recent studies have highlighted the diverse roles of non-coding RNAs in cancer progression and metastasis. Increasing numbers of miRNAs, lncRNAs and circRNAs are found to be dysregulated in cervical cancer, associated with metastasis. They have been shown to regulate metastasis through regulating metastasis-related genes, epithelial-mesenchymal transition, signaling pathways and interactions with tumor microenvironment. Moreover, miRNAs can interact with lncRNAs and circRNAs respectively during this complex process. Herein, we review literatures up to date involving non-coding RNAs in cervical cancer metastasis, mainly focus on the underlying mechanisms and highlight the interaction network between miRNAs and lncRNAs, as well as circRNAs. Finally, we discuss the therapeutic prospects.

Downregulation of lncRNA MIR181A2HG by high glucose impairs vascular endothelial cell proliferation and migration through the dysregulation of the miRNAs/AKT2 axis

Endothelial dysfunction and diabetic vascular disease induced by chronic hyperglycemia involve complex interactions among high glucose, long non-coding RNAs (lncRNAs), microRNAs (miRNAs or miRs) and the Ser/Thr kinase AKT. However, the molecular mechanisms under-lying the regulatory crosstalk between these have not yet been completely elucidated. Thus, the present study aimed to explore the molecular mechanisms whereby high glucose (HG)-induced lncRNA MIR181A2HG modulates human umbilical vein endothelial cell (HUVEC) proliferation and migration by regulating AKT2 expression. The persistent exposure of HUVECs to HG resulted in MIR181A2HG down-regulation and thus reduced its ability to sponge miR-6832-5p, miR-6842-5p and miR-8056, subsequently leading to an increase in miR-6832-5p, miR-6842-5p and miR-8056 levels. Mechanistically, miR-6832-5p, miR-6842-5p and miR-8056 were found to target the 3′UTR of AKT2 mRNA in HUVECs, and the increase in their levels led to a decreased expression of AKT2. Thus, this also led to the suppression of HUVEC proliferation and migration, and the formation of capillary-like structures. Moreover, the suppression of HUVEC proliferation and migration induced by MIR181A2HG downregulation was accompanied by changes in glucose metabolism. On the whole, the present study demonstrates that the downregulation of lncRNA MIR181A2HG by HG impairs HUVEC proliferation and migration by dysregulating the miRNA/AKT2 axis. The MIR181A2HG/miRNA/AKT2 regulatory axis may thus be a potential therapeutic target for HG-induced endothelial dysfunction.

Lung cancer cells and their sensitivity/resistance to cisplatin chemotherapy: Role of microRNAs and upstream mediators

Cisplatin (CP) is a well-known chemotherapeutic agent with excellent clinical effects. The anti-tumor activity of CP has been demonstrated in different cancers such as breast, cervical, reproductive, lung, brain, and prostate cancers. However, resistance of cancer cells to CP chemotherapy has led to its failure in eradication of cancer cells, and subsequent death of patients with cancer. Fortunately, much effort has been put to identify molecular pathways and mechanisms involved in CP resistance/sensitivity. It seems that microRNAs (miRs) are promising candidates in mediating CP resistance/sensitivity, since they participate in different biological aspects of cells such as proliferation, migration, angiogenesis, and differentiation. In this review, we focus on miRs and their regulation in CP chemotherapy of lung cancer, as the most malignant tumor worldwide. Oncogenic miRs trigger CP resistance in lung cancer cells via targeting various pathways such as Wnt/β-catenin, Rab6, CASP2, PTEN, and Apaf-1. In contrast, onco-suppressor miRs inhibit oncogene pathways such as STAT3 to suppress CP resistance. These topics are discussed to determine the role of miRs in CP resistance/sensitivity. We also describe the upstream modulators of miRs such as lncRNAs, circRNAs, NF-κB, SOX2 and TRIM65 and their association with CP resistance/sensitivity in lung cancer cells. Finally, the effect of anti-tumor plant-derived natural compounds on miR expression during CP sensitivity of lung cancer cells is discussed.

Long Non-Coding RNAs: Potential Biomarkers and Targets for Hepatocellular Carcinoma Therapy and Diagnosis

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death worldwide. Increasing studies showed that long non-coding RNAs (lncRNAs), a novel class of RNAs that are greater than 200 nucleotides in length but lack the ability to encode proteins, exert crucial roles in the occurrence and progression of HCC. LncRNAs promote the proliferation, migration, invasion, autophagy, and apoptosis of tumor cells by regulating downstream target gene expression and cancer-related signaling pathways. Meanwhile, lncRNA can be used as biomarkers to predict the efficacy of HCC treatment strategies, such as surgery, radiotherapy, chemotherapy, and immunotherapy, and as a potential individualized tool for HCC diagnosis and treatment. In this review, we overview up-to-date findings on lncRNAs as potential biomarkers for HCC surgery, radiotherapy, chemotherapy resistance, target therapy, and immunotherapy, and discuss the potential clinical application of lncRNA as tools for HCC diagnosis and treatment.

Long non-coding RNA SNHG1 regulates rheumatoid synovial invasion and proliferation by interaction with PTBP1

Fibroblast-like synoviocytes (FLSs) in rheumatoid arthritis (RA) present proliferative and aggressive cell phenotype. RA-FLSs are the essential effector cells that lead to symptoms like synovial inflammation and joint destruction. Currently, the cause of RA-FLSs involving in the pathological process of RA remains unknown. Accumulate researches have demonstrated that lncRNAs may play a critical role in regulating the biological behaviors of RA-FLSs, but the mechanism is still unclear. Here, we found that lncRNA small nucleolar RNA host gene 1 (SNHG1) is up-regulated in RA-FLSs compared with FLSs from trauma arthritis and osteoarthritis patients. The results suggest that SNHG1 in RA-FLSs helps to sustain the cellular functions of proliferation, migration and invasion. Furthermore, the regulation mechanism depends on the interaction between SNHG1 and polypyridine tract-binding protein 1 (PTBP1). This interaction influences PTBP1 expression that participates in the regulation of RA-FLSs biological behaviors. Our results suggest that up-regulated SNHG1 of RA-FLSs may contribute to synovial aggression and disease progression in RA and be favourable for RA treatment target RA-FLSs.

Downregulation of the long noncoding RNA SNHG1 inhibits tumor cell migration and invasion by sponging miR-195 through targeting Cdc42 in oesophageal cancer

Despite the poor prognosis of oesophageal cancer (EC), the molecular mechanisms of EC are still unclear. In recent years, role of lncRNA in cancer development attracted much attention. The present study aimed to investigate the effects of the long noncoding RNA SNHG1 on the migration and invasion of EC cells and the possible mechanisms involved. The effects of SNHG1 on cell proliferation, migration, and invasion were determined and its relationship with miR-195/Cdc42 axis was investigated. It was found SNHG1 and Cdc42 were significantly upregulated, and miR-195 was significantly downregulated in both EC tissues and cell lines. In addition, the inhibition of either SNHG1 or Cdc42 resulted in suppression of cell proliferation, migration, and invasion, while inhibition of miR-195 led to opposite results and reversed the effects of si-SNHG1. We also observed that higher SNHG1 predicted poorer prognosis of EC patients. In summary, inhibition of SNHG1 can suppress the cell migration and invasion of EC cells by sponging miR-195 through targeting Cdc42. This study might provide deeper insights into the SNHG1/miR-195/Cdc42 axis in EC.

lncRNA SNHG1 attenuates osteogenic differentiation via the miR‑101/DKK1 axis in bone marrow mesenchymal stem cells

The imbalance induced by inhibition of bone mesenchymal stem cell (BMSC) osteogenic differentiation results in osteoporosis (OP); however, the underlying regulatory mechanism is not completely understood. Long non-coding RNAs (lncRNAs) serve crucial roles in osteogenic differentiation; therefore, investigating their regulatory role in the process of osteogenic differentiation may identify a promising therapeutic target for OP. The expression of small nucleolar RNA host gene 1 (SNHG1), Dickkopf 1 (DKK1), microRNA (miR)-101, RUNX family transcription factor 2 (RUNX2), osteopontin (OPN) and osteocalin (OCN) were detected via reverse transcription-quantitative PCR. The protein expression levels of DKK1, β-catenin, RUNX2, OPN, OCN, osterix and collagen type I α1 chain were analyzed by performing western blotting. The osteoblastic phenotype was assessed by conducting alkaline phosphatase activity detection and Alizarin Red staining. The interaction between SNHG1 and miR-101 was validated by bioinformatics and luciferase assays. The regulatory role of SNHG1 in BMSC osteogenic differentiation was assessed. SNHG1 expression was downregulated in a time-dependent manner during the process of osteogenic differentiation. SNHG1 overexpression inhibited osteogenic differentiation compared with the pcDNA group. The results indicated that SNHG1 and DKK1 directly interacted with miR-101. Moreover, SNHG1 regulated the Wnt/β-catenin signaling pathway to inhibit osteogenic differentiation via the miR-101/DKK1 axis. The present study indicated that lncRNA SNHG1 could attenuate BMSC osteogenic differentiation via the miR-101/DKK1 axis as a competitive endogenous RNA. Therefore, the present study furthered the current understanding of the potential mechanism underlying lncRNAs in in osteogenic differentiation.

Characterization of super-enhancer-associated functional lncRNAs acting as ceRNAs in ESCC

Long noncoding RNAs (lncRNAs) have important regulatory roles in cancer biology. Although some lncRNAs have well-characterized functions, the vast majority of this class of molecules remains functionally uncharacterized. To systematically pinpoint functional lncRNAs, a computational approach was proposed for identification of lncRNA-mediated competing endogenous RNAs (ceRNAs) through combining global and local regulatory direction consistency of expression. Using esophageal squamous cell carcinoma (ESCC) as model, we further identified many known and novel functional lncRNAs acting as ceRNAs (ce-lncRNAs). We found that most of them significantly regulated the expression of cancer-related hallmark genes. These ce-lncRNAs were significantly regulated by enhancers, especially super-enhancers (SEs). Landscape analyses for lncRNAs further identified SE-associated functional ce-lncRNAs in ESCC, such as HOTAIR, XIST, SNHG5, and LINC00094. THZ1, a specific CDK7 inhibitor, can result in global transcriptional downregulation of SE-associated ce-lncRNAs. We further demonstrate that a SE-associated ce-lncRNA, LINC00094 can be activated by transcription factors TCF3 and KLF5 through binding to SE regions and promoted ESCC cancer cell growth. THZ1 downregulated expression of LINC00094 through inhibiting TCF3 and KLF5. Our data demonstrated the important roles of SE-associated ce-lncRNAs in ESCC oncogenesis and might serve as targets for ESCC diagnosis and therapy.

Long non-coding RNAs in gastric cancer: New emerging biological functions and therapeutic implications

Gastric cancer (GC) is currently the fourth most common malignancy and the third leading cause of cancer-related deaths worldwide. Long non-coding RNAs (lncRNAs), transcriptional products with more than 200 nucleotides, are not as well-characterized as protein-coding RNAs. Accumulating evidence has recently revealed that maladjustments of diverse lncRNAs may play key roles in multiple genetic and epigenetic phenomena in GC, affecting all aspects of cellular homeostasis, such as proliferation, migration, and stemness. However, the full extent of their functionality remains to be clarified. Considering the lack of viable biomarkers and therapeutic targets, future research should be focused on unravelling the intricate relationships between lncRNAs and GC that can be translated from bench to clinic. Here, we summarized the state-of-the-art advances in lncRNAs and their biological functions in GC, and we further discuss their potential diagnostic and therapeutic roles. We aim to shed light on the interrelationships between lncRNAs and GC with respect to their potential therapeutic applications. With better understanding of these relationships, the biological functions of lncRNAs in GC development will be exploitable, and promising new strategies developed for the prevention and treatment of GC.

NORAD orchestrates endometrial cancer progression by sequestering FUBP1 nuclear localization to promote cell apoptosis

Long noncoding RNAs (lncRNAs) are emerging as critical regulators in tumor initiation and progression. However, the biological mechanisms and potential clinical application of lncRNA NORAD in endometrial cancer (EC) remain unknown. Herein, we identified NORAD underwent promoter hypermethylation-associated downregulation in EC. Epigenetic inactivation of NORAD was correlated with EC progression (FIGO stage) and poor outcome. Overexpression of NORAD significantly inhibited cell growth and promoted apoptosis in EC cells. Mechanistic studies revealed that multiple regions of NORAD served as a platform for binding with the central domain of anti-apoptotic factor FUBP1. Our findings further indicated that the NORAD/FUBP1 interaction attenuated FUBP1 nuclear localization and thus impaired the occupancies of FUBP1 on its target pro-apoptotic gene promoters, resulting in apoptosis induction in EC. Moreover, knockdown of NORAD promoted tumor growth in the xenograft mice model. While, introduction of NORAD-4 fragment, which bound with FUBP1, successfully reversed tumor growth and apoptosis inhibition mediated by NORAD knockdown in vivo. Our findings provide mechanistic insight into the critical roles of NORAD as a tumor suppressor in EC progression. NORAD could possibly serve as a novel prognostic biomarker and provide the rationale for EC therapy.

Long noncoding RNA lnc-LOC645166 promotes adriamycin resistance via NF-κB/GATA3 axis in breast cancer

Chemoresistance remains a significant obstacle for effective adriamycin (ADR) treatment in breast cancer. Recent efforts have revealed that long noncoding RNAs (lncRNAs) play a crucial role in cancer biology, including chemoresistance. We identified the lncRNA LOC645166 was upregulated in adriamycin resistant-breast cancer cells by Microarray analysis, which was further confirmed in the tissues of nonresponsive patients by reverse transcription-quantitative polymerase chain reaction (RT–qPCR), western blotting, and immunohistochemical assays. Downregulation of lncRNA LOC645166 increased cell sensitivity to adriamycin both in vitro and in vivo. In contrast, upregulation of lncRNA LOC645166 strengthened the tolerance of breast cancer cells to adriamycin. Chromatin immunoprecipitation (ChIP) and RNA binding protein immunoprecipitation (RIP) demonstrated that lncRNA LOC645166 could increase the expression of GATA binding protein 3 (GATA3) via binding with nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), leading to the activation of STAT3 and promoting chemoresistance in breast cancer. Together, the present study suggested that lncRNA LOC645166 mediated adriamycin chemoresistance in breast cancer by regulating GATA3 via NF-κB.

Long non-coding RNA small nucleolar RNA host gene 6 aggravates pancreatic cancer through upregulation of far upstream element binding protein 1 by sponging microRNA-26a-5p

BACKGROUND

Pancreatic cancer (PC) is a highly deadly malignancy with few effective therapies. We aimed to unmask the role that long non-coding RNA small nucleolar RNA host gene 6 (SNHG6) plays in PC cells by targeting far upstream element binding protein 1 (FUBP1) via microRNA-26a-5p (miR-26a-5p).

METHODS

SNHG6 expression was predicted by bioinformatics, followed by verification via reverse transcription quantitative polymerase chain reaction. Then, the interactions among SNHG6, miR-26a-5p, and FUBP1 were detected through online software analysis, dual luciferase reporter assay and RNA pull-down. After that, cells were treated with different small interfering RNAs and/or mimic to determine the interactions among SNHG6, miR-26a-5p, and FUBP1 and their roles in PC cells. Finally, the role of SNHG6 in tumor growth in vivo was evaluated by measuring the growth and weight of transplanted tumors in nude mice. A t-test, one-way and two-way analysis of variance were used for data analysis.

RESULTS

Compared with that in normal tissues, SNHG6 was highly expressed in PC tissues (1.00 ± 0.05 vs. 1.56 ± 0.06, t = 16.03, P < 0.001). Compared with that in human pancreatic duct epithelial cells (HPDE6-C7), SNHG6 showed the highest expression in PANC-1 cells (1.00 ± 0.06 vs. 3.87 ± 0.13, t = 34.72, P < 0.001) and the lowest expression in human pancreatic cancer cells (MIAPaCa-2) (1.00 ± 0.06 vs. 1.41 ± 0.07, t = 7.70, P = 0.0015). Compared with the levels in the si-negative control group, SNHG6 (0.97 ± 0.05 vs. 0.21 ± 0.06, t = 16.85, P < 0.001), N-cadherin (0.74 ± 0.05 vs. 0.41 ± 0.04, t = 8.93, P < 0.001), Vimentin (0.55 ± 0.04 vs. 0.25 ± 0.03, t = 10.39, P < 0.001), and β-catenin (0.62 ± 0.05 vs. 0.32 ± 0.03, t = 8.91, P < 0.001) were decreased, while E-cadherin (0.65 ± 0.06 vs. 1.36 ± 0.07, t = 13.34, P < 0.001) was increased after SNHG6 knockdown or miR-26a-5p overexpression, accompanied by inhibited cell proliferation, migration, and invasion. SNHG6 overexpression exerted the opposite effects. SNHG6 upregulated FUBP1 expression by sponging miR-26a-5p. Silencing SNHG6 blocked the growth of PC in vivo.

CONCLUSION

Silencing SNHG6 might ameliorate PC through inhibition of FUBP1 by sponging miR-26a-5p, thus providing further supporting evidence for its use in PC treatment.

An Emerging Class of Long Non-coding RNA With Oncogenic Role Arises From the snoRNA Host Genes

The small nucleolar RNA host genes (SNHGs) are a group of long non-coding RNAs, which are reported in many studies as being overexpressed in various cancers. With very few exceptions, the SNHGs (SNHG1, SNHG3, SNHG5, SNHG6, SNHG7, SNHG12, SNHG15, SNHG16, SNHG20) are recognized as inducing increased proliferation, cell cycle progression, invasion, and metastasis of cancer cells, which makes this class of transcripts a viable biomarker for cancer development and aggressiveness. Through our literature research, we also found that silencing of SNHGs through small interfering RNAs or short hairpin RNAs is very effective in both in vitro and in vivo experiments by lowering the aggressiveness of solid cancers. The knockdown of SNHG as a new cancer therapeutic option should be investigated more in the future.

LncRNA DLEU2 promotes tumour growth by sponging miR-337-3p in human osteosarcoma

According to statistics, abnormal regulation of lncRNAs pivotally influences multiple malignant tumours. DLEU2, as one of these lncRNAs, is detected to be related to growth and development of tumours. The molecular mechanisms of DLEU2 in osteosarcoma, however, are still unknown. QRT-PCR was adopted to analyse the correlations of clinicopathological features and prognosis of osteosarcoma cases with DLEU2. The influences of DLEU2 on cell migration and viability were evaluated independently by experiments in vitro and in vivo. Bioinformatics analysis, RNA immunoprecipitation (RIP) assay, and dual luciferase reporter gene assay confirmed the specific binding of DLEU2 to miR-337-3p. Moreover, rescue experiments were carried out to further evaluate the regulatory association between miR-337-3p expression and DLEU2. In osteosarcoma tissues and cells, DLEU2 expression level was raised remarkably in comparison with that in para-carcinoma normal tissues, and DLEU2 high expression had associations with poor prognosis, tumour stages, and TS of osteosarcoma cases. Cell migration ability and viability were blocked by DLEU2 knockdown but enhanced by ectopic DLEU2 expression in vitro and in vivo. Additionally, DLEU2 was found to sponge miR-337-3p and trigger the stimulating effect in osteosarcoma cells, which would be suppressed by miR-337-3p mimics. Furthermore, a negative correlation existed between miR-337-3p expression and DLEU2 in osteosarcoma tissues. This study manifests that DLEU2 sponges miR-337-3p to accelerate tumour growth and is confirmed to be a factor for poor prognosis of osteosarcoma cases. SIGNIFICANCE OF THE STUDY: LncRNA DLEU2 has been reported to be dysregulated in many tumours; however, the functions and underlying mechanism of DLEU2 in osteosarcoma pathogenesis are still unknown. This study is the first to demonstrate the roles of DLEU2 in osteosarcoma and revealed that DLEU2 may serve as a ceRNA to sponge miR-337-3p and then promote the progression of osteosarcoma, providing a potential therapeutic target for osteosarcoma.

Long non‑coding RNA SNHG1 promotes breast cancer progression by regulation of LMO4

Long non-coding RNA (lncRNA) small nucleolar RNA host gene 1 (SNHG1) was reported to be a critical regulator of tumorigenesis and is frequently deregulated in several cancer types. However, the exact mechanism by which SNHG1 contributes to breast cancer progression has not been fully elucidated. The identification of the molecular mechanism of SNHG1 is important for understanding the development of breast cancer and for improving the prognosis of the patients with this disease. In the present study, increased expression levels of SNHG1 were noted in breast cancer tumors following analysis of differentially expressed lncRNAs between 1,063 tumor and 102 normal tissues derived from The Cancer Genome Atlas Breast Invasive Carcinoma (TCGA-BRCA) dataset. This finding was further validated using 50 pairs of normal and tumor tissues that were collected from patients with breast cancer. Notably, SNHG1 expression was significantly correlated with estrogen receptor (ER)/progesterone receptor (PR) negative status (ER⁻/PR⁻) and advanced clinical stage in breast cancer tissues. Knockdown of SNHG1 led to cell growth arrest, cell cycle redistribution and cell migration inhibition of breast cancer cells. The miRDB database predicted that miR-573 interacts with SNHG1. RT-PCR confirmed the negative regulation of miR-573 levels by SNHG1 in breast cancer cells and the Dual-luciferase reporter assay confirmed their complementary binding. The repression of miR-573 by SNGH1 decreased LIM domain only 4 (LMO4) mRNA and protein expression levels in the breast cancer cell lines tested and induced the expression of cyclin D1 and cyclin E. In vitro experiments indicated that LMO4 overexpression could reverse siSNHG1-induced cell growth arrest, cell cycle redistribution and inhibition of cell migration in breast cancer cells. Moreover, the tumor xenograft model indicated that SNHG1 knockdown inhibited MDA-MB-231 growth in vivo and LMO4 overexpression reversed the tumor growth inhibition induced by SNHG1 knockdown. The present study demonstrated that SNHG1 acts as a novel oncogene in breast cancer via the SNHG/miR-573/LMO4 axis and that it could be a promising therapeutic target for patients with breast cancer.

Recounting the FANTOM CAGE-Associated Transcriptome

Long noncoding RNAs (lncRNAs) have emerged as key coordinators of biological and cellular processes. Characterizing lncRNA expression across cells and tissues is key to understanding their role in determining phenotypes, including human diseases. We present here FC-R2, a comprehensive expression atlas across a broadly defined human transcriptome, inclusive of over 109,000 coding and noncoding genes, as described in the FANTOM CAGE-Associated Transcriptome (FANTOM-CAT) study. This atlas greatly extends the gene annotation used in the original recount2 resource. We demonstrate the utility of the FC-R2 atlas by reproducing key findings from published large studies and by generating new results across normal and diseased human samples. In particular, we (a) identify tissue-specific transcription profiles for distinct classes of coding and noncoding genes, (b) perform differential expression analysis across thirteen cancer types, identifying novel noncoding genes potentially involved in tumor pathogenesis and progression, and (c) confirm the prognostic value for several enhancer lncRNAs expression in cancer. Our resource is instrumental for the systematic molecular characterization of lncRNA by the FANTOM6 Consortium. In conclusion, comprised of over 70,000 samples, the FC-R2 atlas will empower other researchers to investigate functions and biological roles of both known coding genes and novel lncRNAs.

Mechanism of long noncoding RNAs as transcriptional regulators in cancer

Dysregulation of gene expression, often interpreted by gene transcription as an endpoint response, is tightly associated with human cancer. Long noncoding RNAs (lncRNAs), derived from the noncoding elements in the genome and appeared no less than 200nt in length, have emerged as a novel class of pivotal regulatory component. Recently, great attention has been paid to the cancer-related lncRNAs and growing evidence have shown that lncRNAs act as key transcriptional regulators in cancer cells through diverse mechanisms. Here, we focus on the nucleus-expressed lncRNAs and summarize their molecular mechanisms in transcriptional control during tumorigenesis and cancer metastasis. Six major mechanisms will be discussed in this review: association with transcriptional factor, modulating DNA methylation or histone modification enzyme, influencing on chromatin remodelling complex, facilitating chromosomal looping, interaction with RNA polymerase and direct association with promoter.

LncRNA HRCEG, regulated by HDAC1, inhibits cells proliferation and epithelial-mesenchymal-transition in gastric cancer

Recently, a number of long noncoding RNAs (lncRNAs) have been reported to play significant roles in human tumorigenesis. However, only few gastric cancer related lncRNAs have been well characterized. Here, we identified one lncRNA HRCEG, whose expression was decreased in the gastric cancer tissues compared with adjacent normal tissues. Overexpression of HRCEG significantly promoted cell apoptosis and inhibited cell proliferation. Importantly, we demonstrated that HRCEG levels inversely correlated with EMT process and HRCEG was regulated by the histone deacetylase 1 (HDAC1) in gastric cancer. These findings suggest that HRCEG might be regulated by HDAC1 to inhibit gastric cancer progress and metastatic capability via EMT pathway.

LncRNA SNHG1 alleviates hypoxia-reoxygenation-induced vascular endothelial cell injury as a competing endogenous RNA through the HIF-1α/VEGF signal pathway

Long noncoding ribonucleic acids (lncRNAs) are critical regulators in various biological processes. In the present study, we aimed to explore whether miR140-3p was involved in the underlying molecular mechanisms of small nucleolar RNA host gene 1 (SNHG1) in myocardial ischemia/reperfusion (I/R) injury. A mouse model of I/R injury and hypoxia-reoxygenation (H/R)-stimulated human umbilical vein endothelial cells (HUVECs) was used in this study. Cell proliferation was detected by MTT. The mRNA and protein levels of vascular endothelial growth factor (VEGF), VE-cadherin, and MMP2 were detected by RT-PCR and western blot, respectively. The angiogenesis was assessed by tube formation assay. Cell migration was assessed using wound-healing assay. Results showed that SNHG1 expression was increased in the cardiac microvasculature of a mouse model of I/R injury and in H/R-stimulated HUVECs. H/R stimulation significantly reduced cell proliferation, tube formation, and cell migration, but increased expression of VEGF, VE-cadherin, and MMP2. SNHG1 upregulation under H/R increased HUVECs proliferation, tube formation, and cell migration, and upregulated expression of VEGF, VE-cadherin, and MMP2, compared with the H/R group. SNHG1 knockdown exhibited the opposite effect. SNHG1 functioned as a competing endogenous RNA (ceRNA) of miR-140-3p. HIF-1α was identified as a target of miR-140-3p. SNHG1 upregulation enhanced cell proliferation, tube formation, and expression of VEGF, VE-cadherin, and MMP2 through HIF-1α/VEGF signaling. This process could be offset by miR-140-3p mimic or VEGF inhibitor. Our results reveal a novel protective function of SNHG1 that furthers understanding of cardiac I/R injury and provides experimental evidence for future therapy.

Long non-coding RNA SNHG3 promotes progression of gastric cancer by regulating neighboring MED18 gene methylation

To understand the mechanistic involvement of long non-coding RNA (lncRNA) SNHG3 in gastric cancer (GC), the relative abundance of SNHG3 was determined by real-time PCR. Overall and metastasis-free survival was analyzed by Kaplan–Meier’s plot. The potential impact of SNHG3 on tumor progression was evaluated both in vitro and in vivo. The in vivo metastasis was monitored in the tail vein-injected mice. Our data suggested that high SNHG3 associated with unfavorable prognosis in respect to overall and metastasis-free survival. SNHG3-deficiency significantly suppressed cell proliferation and cell viability in vitro and xenograft progression in vivo. In addition, ectopic overexpression of SNHG3 promoted cell migration and invasion in vitro and lung metastasis in vivo. Mechanistically, we uncovered SNHG3 associated with EZH2 and negatively regulated MED18 expression through methylation modulation. Transient knockdown of MED18 in SNHG3-deficient cells completely rescued the tumor suppressive phenotypes in GC cells. Our data unraveled the oncogenic properties of high SNHG3 in GC, which predominantly depended on epigenetically regulated MED18.

FUBP1 promotes neuroblastoma proliferation via enhancing glycolysis-a new possible marker of malignancy for neuroblastoma

Background

Neuroblastoma (NB) is one of the deadliest paediatric solid tumours due to its rapid proliferative characteristics. Amplified copies of MYCN are considered the most important marker for the prediction of tumour relapse and progression in NB, but they were only detected in 20–30% of NB patients, indicating there might be other oncogenes in the development of NB. The far upstream element binding protein 1 (FUBP1) was first identified as a transcriptional regulator of the proto-oncogene MYC. However, the expression and role of FUBP1 in NB have not been documented.

Methods

FUBP1 expression was analysed from GEO database and verified by immunohistochemistry (IHC) and western blotting (WB) in NB tissues and cell lines. Cell proliferation and apoptosis were detected by Cell Counting Kit-8, Colony formation assay, EDU, TUNEL staining and flow cytometric analysis. Several glycolytic metabolites production was confirmed by ELISA and oxygen consuming rate (OCR). Luciferase assay, WB, chromatin immunoprecipitation (CHIP) were used to explore the mechanisms of the effect of FUBP1 on NB.

Results

FUBP1 mRNA levels were increased along with the increase in International Neuroblastoma Staging System (INSS) stages. High expression of FUBP1 with low N-Myc expression accounted for 44.6% of NB patient samples (n = 65). In addition, FUBP1 protein levels were remarkably increased with NB malignancy in the NB tissue microarray (NB: n = 65; ganglioneuroblastoma: n = 31; ganglioneuroma: n = 27). Furthermore, FUBP1 expression was negatively correlated with patient survival rate but positively correlated with ki67 content. In vitro experiments showed that FUBP1 promotes NB cell proliferation and inhibits cell apoptosis via enhancing glycolysis and ATP production. Mechanistically, FUBP1 inhibited the degradation of HIF1α via downregulation of Von Hippel-Lindau (VHL), the E3 ligase for HIF1α, resulting in upregulation of lactate dehydrogenase isoform B (LDHB) expression to enhance glycolysis. Overexpressed or silenced N-Myc could not regulate FUBP1 or LDHB levels.

Conclusions

Taken together, our findings demonstrate for the first time that elevated FUBP1 promotes NB glycolysis and growth by targeting HIF1α rather than N-Myc, suggesting that FUBP1 is a novel and powerful oncogene in the development of NB independent of N-Myc and may have potential in the diagnosis and treatment of NB.

Long non-coding RNA MYOSLID functions as a competing endogenous RNA to regulate MCL-1 expression by sponging miR-29c-3p in gastric cancer

Objective

Long non‐coding RNA (lncRNA) has become an important regulator of many human malignancies. However, the biological role and clinical significance of most lncRNA in gastric cancer (GC) remain unclear.

Methods

We investigate the biological function, mechanism of action and clinical expression of lncRNA MYOSLID in GC. First, we analysed the differential expression of lncRNA MYOSLID in GC tissues and non‐cancerous tissues by analysing the sequencing data obtained from The Cancer Genome Atlas. Subsequently, we verified that lncRNA MYOSLID regulates the proliferation and apoptosis of GC cells by acting as a ceRNA against miR‐29c‐3p. The nude mouse xenograft was used to further confirm the functional significance of lncRNA MYOSLID in vivo.

Results

We found for the first time that the expression of lncRNA MYOSLID was significantly up‐regulated in GC tissues, and the up‐regulation of lncRNA MYOSLID in GC was correlated with tumour size, AJCC stage, depth of invasion and survival time. In addition, apoptosis and growth arrest can be induced in vitro after knockdown of lncRNA MYOSLID, which inhibits tumorigenesis in mouse xenografts in vivo. Further in‐depth studies revealed that lncRNA MYOSLID acts as a ceRNA of miR‐29c‐3p, resulting in de‐repression of its downstream target gene MCL‐1.

Conclusion

The lncRNA MYOSLID‐miR‐29c‐3p‐MCL‐1 axis plays a key role in the development of GC. Our findings may provide potential new targets for the diagnosis and treatment of human GC.

Long noncoding RNA THAP9-AS1 is induced by Helicobacter pylori and promotes cell growth and migration of gastric cancer

Background

Long noncoding RNAs (LncRNAs) have been confirmed to play crucial roles in cancer biology. Gastric cancer (GC) is the third leading cause of cancer related death, and Helicobacter pylori (H. pylori) is the major risk factor for GC. In this study, we focused on the roles of H. pylori-related lncRNAs in the progression of GC.

Method

Differentially expressed lncRNAs were identified through RNA-seq analysis of H. pylori-infected GC cells.

Results

We found that the expression of the lncRNA THAP9-AS1 was up-regulated after infection of GC cells with H. pylori and was higher in GC tissues than in gastritis tissues. Colony formation, CCK8 and transwell assays were executed to show that THAP9-AS1 can promote GC cell proliferation and migration in vitro. Our study identified the pro-oncogenic lncRNA THAP9-AS1, which has a higher expression level in GC tissues than in gastritis tissues and which promoted the proliferation and migration of GC cells in vitro.

Conclusion

These findings may provide a potential therapeutic target for H. pylori-associated GC.

Analysis of Survival-Related lncRNA Landscape Identifies A Role for LINC01537 in Energy Metabolism and Lung Cancer Progression

Many long non-coding RNAs (lncRNAs) have emerged as good biomarkers and potential therapeutic targets for various cancers. We aimed to get a detailed understanding of the lncRNA landscape that is associated with lung cancer survival. A comparative analysis between our RNA sequencing (RNA-seq) data and TCGA datasets was conducted to reveal lncRNAs with significant correlations with lung cancer survival and then the association of the most promising lncRNA was validated in a cohort of 243 lung cancer patients. Comparing RNA-seq data with TCGA ones, 84 dysregulated lncRNAs were identified in lung cancer tissues, among which 10 lncRNAs were significantly associated with lung cancer survival. LINC01537 was the most significant one (p = 2.95 × 10⁻⁶). Validation analysis confirmed the downregulation of LINC01537 in lung cancer. LINC01537 was observed to inhibit tumor growth and metastasis. It also increased cellular sensitivity to nilotinib. PDE2A (phosphodiesterase 2A) was further identified to be a target of LINC01537 and it was seen that LINC01537 promoted PDE2A expression via RNA–RNA interaction to stabilize PDE2A mRNA and thus echoed effects of PDE2A on energy metabolism including both Warburg effect and mitochondrial respiration. Other regulators of tumor energy metabolism were also affected by LINC01537. These results elucidate a suppressed role of LINC01537 in lung cancer development involving tumor metabolic reprogramming, and we believe that it might be a biomarker for cancer survival prediction and therapy.

SNHG5 Promotes Breast Cancer Proliferation by Sponging the miR-154-5p/PCNA Axis

Breast cancer is the most common malignant tumor and the main cause of cancer-associated mortality in females worldwide. Long non-coding RNAs (lncRNAs) have been reported to play vital roles in breast cancer development and progression; however, our understanding of most lncRNAs in breast cancer is still limited. In this study, we demonstrated that small nucleolar RNA host gene 5 (SNHG5) promotes breast cancer cell proliferation both in vitro and in vivo, and depletion of SNHG5 significantly led to cell-cycle arrest at G1 phase. Accumulating evidence has shown that many lncRNA transcripts could function as competing endogenous RNAs (ceRNAs) by competitively binding common microRNAs (miRNAs). We found that SNHG5 acts as a sponge for miR-154-5p, reducing its ability to repress proliferating cell nuclear antigen (PCNA). SNHG5 promoted breast cancer proliferation and cell-cycle progression by upregulation of PCNA expression. Clinically, we observed an increased SNHG5 expression in breast cancer, whereas miR-154-5p was decreased in breast cancer tissues compared with the adjacent normal breast tissues. Furthermore, the SNHG5 expression was significantly negatively correlated with miR-154-5p expression. Taken together, our data uncover the SNHG5-miR-154-5p-PCNA axis and provide a novel mechanism to explain breast cancer proliferation.

LncRNA SNHG1 contributes to sorafenib resistance by activating the Akt pathway and is positively regulated by miR-21 in hepatocellular carcinoma cells

Background

Acquired resistance to sorafenib greatly limits its therapeutic efficiency in the treatment of hepatocellular carcinoma (HCC). Increasing evidence indicates that long noncoding RNAs (lncRNAs) play important roles in the resistance to anti-cancer drugs. The present study aims to explore the involvement of lncRNA SNHG1 (small nucleolar RNA host gene 1) in sorafenib resistance and how SNHG1 is associated with overexpressed microRNA-21 (miR-21) and the activated Akt pathway, which have been demonstrated to mediate this resistance in HCC cells.

Methods

Sorafenib-resistant HCC (SR-HCC) cells were generated and their sorafenib-resistant properties were confirmed by cell viability and apoptosis assays. Potential lncRNAs were screened by using multiple bioinformatics analyses and databases. The expression of genes and proteins was detected by qRT-PCR, Western blot and in situ hybridization. Gene silencing was achieved by specific siRNA or lncRNA Smart Silencer. The effects of anti-SNHG1 were evaluated in vitro and in experimental animals by using quantitative measures of cell proliferation, apoptosis and autophagy. The binding sites of miR-21 and SNHG1 were predicted by using the RNAhybrid algorithm and their interaction was verified by luciferase assays.

Results

The Akt pathway was highly activated by overexpressed miR-21 in SR-HCC cells compared with parental HCC cells. Among ten screened candidates, SNHG1 showed the largest folds of alteration between SR-HCC and parental cells and between vehicle- and sorafenib-treated cells. Overexpressed SNHG1 contributes to sorafenib resistance by activating the Akt pathway via regulating SLC3A2. Depletion of SNHG1 enhanced the efficacy of sorafenib to induce apoptosis and autophagy of SR-HCC cells by inhibiting the activation of Akt pathway. Sorafenib induced translocation of miR-21 to the nucleus, where it promoted the expression of SNHG1, resulting in upregulation of SLC3A2, leading to the activation of Akt pathway. In contrast, SNHG1 was shown to have little effect on the expression of miR-21, which downregulated the expression of PTEN, leading to the activation of the Akt pathway independently of SNHG1.

Conclusions

The present study has demonstrated that lncRNA SNHG1 contributes to sorafenib resistance by activating the Akt pathway and its nuclear expression is promoted by miR-21, whose nuclear translocation is induced by sorafenib. These results indicate that SNHG1 may represent a potentially valuable target for overcoming sorafenib resistance for HCC.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1177-0) contains supplementary material, which is available to authorized users.

Long Noncoding RNA: Function and Mechanism on Differentiation of Mesenchymal Stem Cells and Embryonic Stem Cells

Background:

Long suspected as transcriptional noise, recently recognized, long non-coding RNAs (lncRNAs) are emerging as an indicator, biomarker and therapy target in the physiologic and pathologic process. Mesenchymal stem cells and embryonic stem cells are important source for normal and therapeutic tissue repair. However, the mechanism of stem cell differentiation is not completely understood. Research on lncRNAs may provide novel insights into the mechanism of differentiation process of the stem cell which is important for the application of stem cell therapy. The lncRNAs field is still very young, new insights into lncRNAs function are emerging to a greater understanding of biological processes.

Objective:

In this review, we summarize the recent researches studying lncRNAs and illustrate how they act in the differentiation of the mesenchymal stem cells and embryonic stem cells, and discuss some future directions in this field.

Results:

Numerous lncRNAs were differentially expressed during differentiation of mesenchymal stem cells and embryonic stem cells. LncRNAs were able to regulate the differentiation processes through epigenetic regulation, transcription regulation and post-transcription regulation.

Conclusion:

LncRNAs are involved in the differentiation process of mesenchymal stem cells and embryonic stem cells, and they could become promising indicator, biomarker and therapeutic targets in the physiologic and pathologic process. However, the mechanisms of the role of lncRNAs still require further investigation.

LncRNA SNHG1 correlates with higher T stage and worse overall survival, and promotes cell proliferation while reduces cell apoptosis in breast cancer

Background

The aim of this study was to investigate the correlation of long non-coding RNA (lncRNA) small nucleolar RNA host gene 1 (SNHG1) with the prognosis in breast cancer patients, and its effect on breast cancer cell proliferation and apoptosis.

Methods

A total of 178 breast cancer patients were consecutively recruited, then tumor tissue and the paired adjacent tissue were obtained during surgery for lncRNA SNHG1 determination by quantitative polymerase chain reaction (qPCR). LncRNA SNHG1 expression was also measured in breast cancer cell lines and normal breast epithelial cell line. Subsequently, negative control (NC) overexpression plasmids, lncRNA SNHG1 overexpression plasmids, NC short hairpin RNA (shRNA) plasmids and lncRNA SNHG1 shRNA plasmids were transfected into MDA-MB-453 cells as well as MCF7 cells, and cell proliferation and apoptosis were measured afterward.

Results

LncRNA SNHG1 expression in tumor tissue was increased compared with paired adjacent tissue, and it correlated with higher T stage and worse overall survival (OS) in breast cancer patients. LncRNA SNHG1 expression was also elevated in breast cancer cell lines compared with normal breast epithelial cell line. Cell Counting Kit-8 (CCK8) assay revealed that lncRNA SNHG1 overexpression promoted while lncRNA SNHG1 shRNA reduced cell proliferation, and Annexin V-fluorescein isothiocyanate/propidium iodide staining (AV/PI) assay illustrated that lncRNA SNHG1 overexpression decreased while lncRNA SNHG1 shRNA increased cell apoptosis rate. In addition, Western Blot assay disclosed that lncRNA SNHG1 overexpression downregulated while lncRNA SNHG1 shRNA upregulated pro-apoptotic marker (C-Caspase3) expression, and lncRNA SNHG1 overexpression increased while lncRNA SNHG1 shRNA decreased anti-apoptotic marker (p-P38) expression.

Conclusions

LncRNA SNHG1 is upregulated in tumor tissue and correlates with higher T stage and worse OS, and it promotes cell proliferation but inhibits cell apoptosis in breast cancer.