Mechanism of long noncoding RNAs as transcriptional regulators in cancer

LINC00540 promotes sorafenib resistance and functions as a ceRNA for miR-4677-3p to regulate AKR1C2 in hepatocellular carcinoma

Sorafenib resistance is one of the main causes of poor prognosis in patients with advanced hepatocellular carcinoma (HCC). Long noncoding RNAs (lncRNAs) function as suppressors or oncogenic factors during tumor progression and drug resistance. Here, to identify therapeutic targets for HCC, the biological mechanisms of abnormally expressed lncRNAs were examined in sorafenib-resistant HCC cells. Specifically, we established sorafenib-resistant HCC cell lines (Huh7-S and SMMC7721-S), which displayed an epithelial-mesenchymal transition (EMT) phenotype. Transcriptome sequencing (RNA-Seq) was performed to established differential lncRNA expression profiles for sorafenib-resistant cells. Through this analysis, we identified LINC00540 as significantly up-regulated in sorafenib-resistant cells and a candidate lncRNA for further mechanistic investigation. Functionally, LINC00540 knockdown promoted sorafenib sensitivity and suppressed migration, invasion, EMT and the activation of PI3K/AKT signaling pathway in sorafenib-resistant HCC cells, whereas overexpression of LINC00540 resulted in the opposite effects in parental cells. LINC00540 functions as a competing endogenous RNA (ceRNA) by competitively binding to miR-4677-3p , thereby promoting AKR1C2 expression. This is the first study that demonstrates a role for LINC00540 in enhancing sorafenib resistance, migration and invasion of HCC cells through the LINC00540/miR-4677-3p/AKR1C2 axis, suggesting that LINC00540 may represent a potential therapeutic target and prognosis biomarker for HCC.

Epigenetic biomarkers for disease susceptibility and preventative medicine

The development of molecular biomarkers for disease makes it possible for preventative medicine approaches to be considered. Therefore, therapeutics, treatments, or clinical management can be used to delay or prevent disease development. The problem with genetic mutations as biomarkers is the low frequency with genome-wide association studies (GWASs), generally at best a 1% association of the patients with the disease. In contrast, epigenetic alterations have a high-frequency association of greater than 90%-95% of individuals with pathology in epigenome-wide association studies (EWASs). A wide variety of human diseases have been shown to have epigenetic biomarkers that are disease specific and that detect pathology susceptibility. This review is focused on the epigenetic biomarkers for disease susceptibility, and it distinct from the large literature on epigenetics of disease etiology or progression. The development of efficient epigenetic biomarkers for disease susceptibility will facilitate a paradigm shift from reactionary medicine to preventative medicine.

Role of LncRNAs in the Pathogenesis of Sepsis and their Clinical Significance

Sepsis is a fatal organ dysfunction caused by the host's uncontrolled response to infection, with high morbidity and mortality. Early diagnosis and intervention are the most effective methods to reduce the mortality due to sepsis. However, there is still a lack of definite biomarkers or intervention targets for the diagnosis, evaluation, prognosis, and treatment of sepsis. Long non-coding RNAs (lncRNAs) are a type of noncoding transcript with a length ranging from 200 to 100,000 nucleotides. LncRNAs mainly locate in the cytoplasm and nucleus and participate in various signaling pathways related to inflammatory reactions and organ dysfunction. Recent studies have reported that lncRNAs are involved in regulating the pathophysiological process of sepsis. Some classical lncRNAs have been confirmed as promising biomarkers to evaluate the severity and prognosis of sepsis. This review summarizes the mechanical studies on lncRNAs in sepsis-induced acute lung, kidney, myocardial, and liver injuries, analyzes the role of lncRNAs in the pathogenesis of sepsis, and explores the possibility of lncRNAs as potential biomarkers and intervention targets for sepsis-induced multiple organ dysfunction.

KIF26B-AS1 Regulates TLR4 and Activates the TLR4 Signaling Pathway to Promote Malignant Progression of Laryngeal Cancer

Laryngeal cancer is one of the highest incidence, most prevalently diagnosed head and neck cancers, making it critically necessary to probe effective targets for laryngeal cancer treatment. Here, real-time quantitative reverse transcription PCR (qRT-PCR) and western blot analysis were used to detect gene expression levels in laryngeal cancer cell lines. Fluorescence in situ hybridization (FISH) and subcellular fractionation assays were used to detect the subcellular location. Functional assays encompassing Cell Counting Kit-8 (CCK-8), 5-ethynyl-2'-deoxyuridine (EdU), transwell and wound healing assays were performed to examine the effects of target genes on cell proliferation and migration in laryngeal cancer. The in vivo effects were proved by animal experiments. RNA-binding protein immunoprecipitation (RIP), RNA pulldown and luciferase reporter assays were used to investigate the underlying regulatory mechanisms. The results showed that KIF26B antisense RNA 1 (KIF26B-AS1) propels cell proliferation and migration in laryngeal cancer and regulates the toll-like receptor 4 (TLR4) signaling pathway. KIF26B-AS1 also recruits FUS to stabilize TLR4 mRNA, consequently activating the TLR4 signaling pathway. Furthermore, KIF26B-AS1 plays an oncogenic role in laryngeal cancer via upregulating TLR4 expression as well as the FUS/TLR4 pathway axis, findings which offer novel insight for targeted therapies in the treatment of laryngeal cancer patients.

MIR31HG polymorphisms are related to steroid-induced osteonecrosis of femoral head among Chinese Han population

Backgrounds

MIR31 host gene (MIR31HG) polymorphisms play important roles in the occurrence of osteonecrosis. However, the association of MIR31HG polymorphisms with the risk of steroid-induced osteonecrosis of the femoral head (SONFH) remains unclear. In this study, we aimed to investigate the correlation between MIR31HG polymorphisms and SONFH susceptibility in the Chinese Han population.

Methods

A total of 708 volunteers were recruited to detect the effect of seven single nucleotide polymorphisms (SNPs) in the MIR31HG gene on SONFH risk in the Chinese Han population. Genotyping of MIR31HG polymorphisms was performed using the Agena MassARRAY platform. The odds ratio (OR) and 95% confidence interval (95% CI) were used to evaluate the correlation between MIR31HG polymorphisms and SONFH risk using logistic regression model.

Results

According to the results of genetic model, rs10965059 in MIR31HG was significantly correlated with the susceptibility to SONFH (OR = 0.56, p = 0.002). Interestingly, the stratified analysis showed that rs10965059 was associated with the reduced risk of SONFH in subjects aged > 40 years (OR = 0.30, p < 0.001) and male populations (OR = 0.35, p < 0 .001). Moreover, rs10965059 was associated with the reduced risk of bilateral SONFH (OR = 0.50, p = 0.002). Finally, multi-factor dimension reduction (MDR) results showed that the combination of rs1332184, rs72703442, rs2025327, rs55683539, rs2181559, rs10965059 and rs10965064 was the best model for predicting SONFH occurrence (p < 0.0001).

Conclusion

The study indicated that rs10965059 could be involved in SONFH occurrence in the Chinese Han population, which might provide clues for investigating the role of MIR31HG in the pathogenesis of SONFH.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05785-w.

Circular RNAs and Their Role in Exosomes

As a novel class of endogenous non-coding RNAs discovered in recent years, circular RNAs (circRNAs) are highly conserved and stable covalently closed ring structures with no 5'-end cap or 3'-end poly(A) tail. CircRNAs are formed by reverse splicing, mainly by means of a noose structure or intron complementary pairing. Exosomes are tiny discoid vesicles with a diameter of 40-100 nm that are secreted by cells under physiological and pathological conditions. Exosomes play an important role in cell-cell communication by carrying DNA, microRNAs, mRNAs, proteins and circRNAs. In this review, we summarize the biological functions of circRNAs and exosomes, and further reveal the potential roles of exosomal circRNAs in different diseases, providing a scientific basis for the diagnosis, treatment, and prognosis of a wide variety of diseases.

Long non-coding RNA MAFG-AS1 promotes proliferation and metastasis of breast cancer by modulating STC2 pathway

Breast cancer is the most common cancer worldwide. A number of studies proposed that long non-coding RNA plays an essential role in the regulation of invasion and metastasis of various forms of malignancy, including lung cancer, gastric cancer, and bladder cancer. In this study, a long non-coding RNA(LncRNA) MAFG-AS1 was explored in detail to understand the significance in the etiology of breast cancer. The results indicated that expression of LncRNA MAFG-AS1 in the breast cancer tissues was significantly higher than the adjacent normal breast tissues and elevated expression level of LncRNA MAFG-AS1 was correlated to the larger tumor size, negative expression of ER, PR and lymph node metastasis. The potency of breast cancer proliferation, invasion, and metastasis was inhibited in the absence of LncRNA MAFG-AS1. Mechanically, LncRNA MAFG-AS1 was mainly located in the cytoplasm. The downstream target gene of LncRNA MAFG-AS1 was STC2 which might promote cell proliferation and metastasis in breast cancer and this study provides a new potential therapeutic target for breast cancer.

Comprehensive Analysis of Subtypes and Identification of Key lncRNAs Based on Glutamine Metabolism-Related Long Noncoding RNAs

Background

Long noncoding RNAs (lncRNAs) are becoming a critical class of metabolic regulate molecule in cancer. Glutamine is a regulator that contributes to each of the core metabolic tasks in proliferating tumor cells. Thus, we aimed to evaluate the association of lncRNAs with glutamine metabolism in lung adenocarcinoma (LUAD).

Methods

Using single-sample gene set enrichment analysis (ssGSEA), LUAD specimens were assigned scores based on glutamine metabolism-related genes, and the shared common glutamine metabolism-related lncRNAs in three different LUAD data cohorts were identified. ConsensusClusterPlus was used to perform unsupervised clustering analysis in patients with LUAD. Key glutamine metabolism-related lncRNAs were identified by first-order partial correlation analysis.

Results

A total of 11 shared glutamine metabolism-associated lncRNAs were identified in three LUAD data cohorts, and LUAD patients were classified into three glutamine metabolism subtypes based on the expressions of the related genes. C1 exhibited shorter overall survival (OS), poor genomic instability, and inadequate infiltration of immune cell types in the tumor microenvironment (TME) and was representative of the immunodeficiency phenotype. C2 represented the immunosuppressive phenotype while C3 represented the immune activation phenotype, exhibiting the highest sensitivity to immunotherapy. Nine of the 11 lncRNAs were localized to the nucleus. Finally, three key lncRNAs, significantly enriched in multiple metabolic pathways, were screened and found to be remarkably related to the OS of LUAD.

Conclusion

We identified three glutamine metabolism subtypes of LUAD, which reflected different OS, genomic, and TME features, and identified three key glutamine metabolism-associated lncRNAs may contribute to further study of lncRNAs in cancer metabolism.

LncRNA cancer susceptibility 20 regulates the metastasis of human gastric cancer cells via the miR-143-5p/MEMO1 molecular axis

BACKGROUND

Gastric cancer (GC) is considered as one of the most widespread malignancies. Emerging evidence has shown that lncRNAs can function as important oncogenes or tumor suppressors during GC progression.

AIM

To investigate the effect and mechanism of lncRNA cancer susceptibility 20 (CASC20) in the proliferation and metastasis of GC cells.

METHODS

Data mining and clinical samples were used to evaluate the expression of CASC20 in GC and adjacent tissues. CASC20 was down-regulated in GC cells by short-interfering RNA. Cell proliferation was evaluated by CCK-8 assay, and cell migration and invasion were detected by wound healing and Transwell assays. The expressions of proteins related to epithelial-mesenchymal transition were detected by western blot assay.

RESULTS

The expression of CASC20 was increased in GC tumor tissues and various GC cell lines. High CASC20 expression was correlated with a high risk of lymphatic metastasis and poor prognosis in GC patients. In vitro assays showed that silencing CASC20 reduced cell proliferation, migration, and invasion in GC cells. Mechanistic studies revealed that CASC20 exhibits oncogenic functions by regulating MEMO1 expression through competitive endogenous binding to miR-143-5p, leading to induction of epithelial-mesenchymal transition.

CONCLUSION

Our findings indicate that CASC20 serves as a tumor promoter by regulating metastasis in GC via the miR-143-5p/MEMO1 axis. CASC20 may be a potential therapeutic target for GC.

Identification of glycolysis-associated long non-coding RNA regulatory subtypes and construction of prognostic signatures by transcriptomics for bladder cancer

Glycolysis-targeted cancer therapy based on long non-coding RNAs (lncRNAs), owing to its high specificity and less toxicity, is at the preclinical stages. Our study aimed to examine the roles of the core glycolysis-associated lncRNAs in bladder cancer (BC). Glycolysis scores of BC were computed by single-sample gene set enrichment analysis (ssGSEA). Glycolysis-associated lncRNAs were screened by Pearson's correlation analysis. Unsupervised consensus clustering using ConsensusClusterPlus assessed the glycolysis-associated lncRNAs for the identification of molecular subtypes of BC. The Kaplan-Meier survival analysis, genomic mutations, and tumor microenvironment (TME) analysis were used to compare the characteristics of different subtypes. Key glycolysis-associated lncRNAs were screened by first-order partial correlation and univariate Cox proportional-hazards model analyses; finally, the lncRNA signature was constructed. Four glycolysis-associated lncRNA-regulated subtypes having differential overall survival (OS), clinical features, genomic mutation profiles, and TME profiles along with nuclear immunotherapeutic responses were identified. Nine lncRNAs localized in the nucleus were identified and transcription factors (TFs) significantly negatively associated with these were found to be enriched in multiple oncogenic signaling pathways. Among them, three lncRNAs (AC093673.5, AC034220.3, and RP11-250B2.3) exerted the most profound effects on glycolysis and constituted the lncRNA signature, which could substantially distinguish the risk levels among different BC patients. Four glycolysis-associated lncRNA-regulated subtypes were identified in this study, reflective of the biological characteristics and heterogeneity of BC. Three key glycolysis-associated lncRNA constituting a signature could predict the risk levels in BC, provide a reference for stratification, and be used as prognostic markers for BC diagnosis and treatment.

A pair of long intergenic non-coding RNA LINC00887 variants act antagonistically to control Carbonic Anhydrase IX transcription upon hypoxia in tongue squamous carcinoma progression

Background

Long noncoding RNAs (lncRNAs) are important regulators in tumor progression. However, their biological functions and underlying mechanisms in hypoxia adaptation remain largely unclear.

Results

Here, we established a correlation between a Chr3q29-derived lncRNA gene and tongue squamous carcinoma (TSCC) by genome-wide analyses. Using RACE, we determined that two novel variants of this lncRNA gene are generated in TSCC, namely LINC00887_TSCC_short (887S) and LINC00887_TSCC_long (887L). RNA-sequencing in 887S or 887L loss-of-function cells identified their common downstream target as Carbonic Anhydrase IX (CA9), a gene known to be upregulated by hypoxia during tumor progression. Mechanistically, our results showed that the hypoxia-augmented 887S and constitutively expressed 887L functioned in opposite directions on tumor progression through the common target CA9. Upon normoxia, 887S and 887L interacted. Upon hypoxia, the two variants were separated. Each RNA recognized and bound to their responsive DNA cis-acting elements on CA9 promoter: 887L activated CA9’s transcription through recruiting HIF1α, while 887S suppressed CA9 through DNMT1-mediated DNA methylation.

Conclusions

We provided hypoxia-permitted functions of two antagonistic lncRNA variants to fine control the hypoxia adaptation through CA9.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-021-01112-2.

Identification of Autophagy- and Ferroptosis-Related lncRNAs Functioned through Immune-Related Pathways in Head and Neck Squamous Carcinoma

The interplay between autophagy and ferroptosis has been highlighted as an important event to decide cancer cell fate. However, the underlying mechanisms remain largely unclear. In this study, we systematically explored the expression, prognostic value and functional roles of lncRNA in autophagy and ferroptosis. By a set of bioinformatics analyses, we identified 363 autophagy- and ferroptosis-related lncRNAs (AF-lncRNAs) and found 17 of them are dramatically related to the prognosis of head and neck squamous cell carcinoma (HNSC) patients, named as prognosis-related AF-lncRNAs (PAF-lncRNAs). Based on six key PAF-lncRNAs, a risk score model was developed and used to categorize the TCGA-retrieved HNSC patients into two groups (high-risk vs. low-risk). Functional analysis showed the differentially expressed genes (DEGs) between the two groups were mainly enriched in immune-related pathways and regulated by a PAF-lncRNA-directed ceRNA (competitive endogenous RNA) network. Combined with a variety of immune infiltration analyses, we also found a decreased landscape of immune cell infiltration in high-risk groups. Together, by revealing PAF-lncRNAs with tumor prognostic features functioned through immune-related pathways, our work would contribute to show the pathogenesis of a lncRNA-directed interplay among autophagy, ferroptosis and tumor immunity in HNSC and to develop potential prognostic biomarkers and targets for tumor immunotherapy.

Identification and validation of a novel eight mutant-derived long non-coding RNAs signature as a prognostic biomarker for genome instability in low-grade glioma

Long non-coding RNAs (lncRNAs) comprise an integral part of the eukaryotic transcriptome. Alongside proteins, lncRNAs modulate lncRNA-based gene signatures of unstable transcripts, play a crucial role as antisense lncRNAs to control intracellular homeostasis and are implicated in tumorigenesis. However, the role of genomic instability-associated lncRNAs in low-grade gliomas (LGG) has not been fully explored. In this study, lncRNAs expression and somatic mutation profiles in low-grade glioma genome were used to identify eight novel mutant-derived genomic instability-associated lncRNAs including H19, FLG-AS1, AC091932.1, AC064875.1, AL138767.3, AC010273.2, AC131097.4 and ISX-AS1. Patients from the LGG gene mutagenome atlas were grouped into training and validation sets to test the performance of the signature. The genomic instability-associated lncRNAs signature (GILncSig) was then validated using multiple external cohorts. A total of 59 novel genomic instability-associated lncRNAs in LGG were used for least absolute shrinkage and selection operator (Lasso), single and multifactor Cox regression analysis using the training set. Furthermore, the independent predictive role of risk features in the training and validation sets were evaluated through survival analysis, receiver operating feature analysis and construction of a nomogram. Patients with IDH1 mutation status were grouped into two different risk groups based on the GILncSig score. The low-risk group showed a relatively higher rate of IDH1 mutations compared with patients in the high-risk group. Furthermore, patients in the low-risk group had better prognosis compared with patients in the high-risk group. In summary, this study reports a reliable prognostic prediction signature and provides a basis for further investigation of the role of lncRNAs on genomic instability. In addition, lncRNAs in the signature can be used as new targets for treatment of LGG.

RNA and liquid-liquid phase separation

Liquid-Liquid Phase Separation (LLPS) is a biological phenomenon that refers to the components of similar properties form droplets condensate in cells. These droplets play an important role in maintaining the stability of order in cells. In the studies of phase separation, weak multivalent interactions between proteins have always been the focus of attentions. With the deepening research of phase separation, more and more evidences show that RNA, especially long noncoding RNA (lncRNA), also plays an important regulatory role in the phase separation. We summarized recent researches between phase separation and RNA, and focused on the function of non-coding RNA (ncRNA) in the process of phase separation. In fact, phase separation and RNA have a two-way regulation relationship. Noncoding RNA usually recruits proteins as molecular scaffolds to drive phase separation. On the other hand, phase separation is also involved in RNA transcription, transport, metabolism and other processes.

7SK Acts as an Anti-tumor Factor in Tongue Squamous Cell Carcinoma

Increasing evidence has shown the mechanistic insights about non-coding RNA 7SK in controlling the transcription. However, the biological function and mechanism of 7SK in cancer are largely unclear. Here, we show that 7SK is down-regulated in human tongue squamous carcinoma (TSCC) and acts as a TSCC suppressor through multiple cell-based assays including a migration assay and a xenograft mouse model. The expression level of 7SK was negatively correlated with the size of tumors in the 73 in-house collected TSCC patients. Through combined analysis of 7SK knockdown of RNA-Seq and available published 7SK ChIRP-seq data, we identified 27 of 7SK-regulated genes that were involved in tumor regulation and whose upstream regulatory regions were bound by 7SK. Motif analysis showed that the regulatory sequences of these genes were enriched for transcription factors FOXJ3 and THRA, suggesting a potential involvement of FOXJ3 and THRA in 7SK-regulated genes. Interestingly, the augmented level of FOXJ3 in TSCC patients and previous reports on THRA in other cancers have suggested that these two factors may promote TSCC progression. In support of this idea, we found that 21 out of 27 aforementioned 7SK-associated genes were regulated by FOXJ3 and THRA, and 12 of them were oppositely regulated by 7SK and FOXJ3/THRA. We also found that FOXJ3 and THRA dramatically promoted migration in SCC15 cells. Collectively, we identified 7SK as an antitumor factor and suggested a potential involvement of FOXJ3 and THRA in 7SK-mediated TSCC progression.

Web tools to perform long non-coding RNAs analysis in oncology research

Accumulated evidence suggests that the widely expressed long-non-coding RNAs (lncRNAs) are involved in biogenesis. Some aberrant lncRNAs are closely related to pathological changes, for instance, in cancer. Both in tumorigenesis and cancer progression, depending on the interplay with cellular molecules, lncRNAs can modulate transcriptional interference, chromatin remodeling, post-translational regulation and protein modification, and further interfere with signaling pathways. Aiming to the diagnosis/ prognosis markers or potential therapeutical targets, it is important to figure out the specific mechanism and the tissue-specific expressing patterns of lncRNAs. Generally, the bioinformatics analysis is the first step. More and more in silico databases are increasing. But the existing integrative online platforms’ functions are not only having their unique features but also share some common features, which may lead to a waste of time for researchers. Here, we reviewed these web tools according to the functions. For each database, we clarified the data source, analysis method and the evidence that the analysis result is derived from. This review also illustrated examples in practical use for a specific lncRNA by these web tools. It will provide convenience for researchers to quickly choose the appropriate bioinformatics web tools in oncology studies.

TMPO-AS1, a Novel E2F1-Regulated lncRNA, Contributes to the Proliferation of Lung Adenocarcinoma Cells via Modulating miR-326/SOX12 Axis

Background

TMPO-AS1, an antisense lncRNA located at human chromosome 12p23.1, has been identified as an oncogene involved in cell proliferation in various cancers, including LUAD. In this study, we aimed to explore the novel molecular mechanism of TMPO-AS1 underlying LUAD growth.

Materials and Methods

The transcription levels of TMPO-AS1, miR-326, and SOX12 in LUAD tissues and cell lines were detected by quantitative real-time PCR (qRT-PCR). The cell proliferation ability was evaluatect 3d by cell counting kit-8 (CCK-8) assay. Cell cycle and apoptosis analysis was assessed by flow cytometry. The target relationship among TMPO-AS1, miR-326, and SOX12 and promoter activity of TMPO-AS1 was measured using dual-luciferase reporter assay. The protein levels of SOX12 in LUAD cells were determined by Western blot. ChIP-qPCR assay was performed to validate the direct binding between E2F1 and TMPO-AS1 promoter.

Results

TMPO-AS1 was up-regulated in LUAD tissues as well as cell lines. Boosted TMPO-AS1 expression was positively correlated with poor prognosis and pathological stage in LUAD. Down-regulation of TMPO-AS1 could restrain the proliferation of LUAD cells through arresting the cell cycle at G0/G1 phase and inducing apoptosis in vitro. Mechanically, we demonstrated that TMPO-AS1 could modulate the proliferation of LUAD cells through increasing SOX12 expression level via sponging miR-326 in accordance with bioinformatics analysis and experimental validation. Furthermore, we identified that TMPO-AS1 could be activated by E2F transcription factor 1 (E2F1) as a novel target gene.

Conclusion

TMPO-AS1 can modulate LUAD cell proliferation through E2F1/miR-326/SOX12 pathway.

Upregulated Long Non-Coding RNA LL22NC03-N64E9.1 Promotes the Proliferation and Migration of Human Breast Cancer Cells by Silencing Kruppel-Like Factor 2 Expression

Introduction

Recently, the significant regulatory effects of lncRNAs on the oncogenesis and growth of tumor have been demonstrated by an increasing number of research projects. A previous study showed that LL22NC03-N64E9.1 could promote the development of colorectal cancer, especially via enhanced cell proliferation. Similarly, this lncRNA should have comparable functions in breast cancer (BC), which requires in-depth investigation. Therefore, this study was designed to explore the correlation of LL22NC03-N64E9.1 with BC.

Methods

qRT-PCR was used to assess the relative expression of LL22NC03-N64E9.1 in BC tissues. Cell viability examination and colony formation experiments were performed to investigate the role of LL22NC03-N64E9.1 in BC cell’s proliferation. Transwell assays were used to explore the effects of LL22NC03-N64E9.1 on BC cell’s migration. RNA immunoprecipitation, chromosome immunoprecipitation assay and rescue experiments were performed to analyze the association of LL22NC03-N64E9.1 with target proteins and genes in BC cells.

Results

We identified that LL22NC03-N64E9.1 is an oncogene, upregulated in BC, which was verified in a cohort of 48 pairs of BC tissues. Based on the loss-of-function experiments, silencing LL22NC03-N64E9.1 expression significantly inhibited malignancy progression. In terms of the mechanism, LL22NC03-N64E9.1 acted on the enhancer of zeste homolog 2 (EZH2) by direct binding, which promoted BC cell growth. Furthermore, in the promoters of KLF2, the trimethylation of H3K27 could be regulated by LL22NC03-N64E9.1 as the mediator.

Conclusion

Relying on the LL22NC03-N64E9.1/EZH2/KLF2 pathway, the lncRNA LL22NC03-N64E9.1 was significantly associated with BC development and could, therefore, be a potential therapeutic target to block BC growth.

MSC-AS1 knockdown inhibits cell growth and temozolomide resistance by regulating miR-373-3p/CPEB4 axis in glioma through PI3K/Akt pathway

Long non-coding RNAs (lncRNAs) have been widely reported to regulate the development and chemoresistance of a variety of tumors. Temozolomide (TMZ) is a first-line chemotherapy for treatment of glioma. However, the effect and the regulatory mechanism of lncRNA MSC-AS1 (MSC-AS1) in TMZ-resistant glioma remain unrevealed. Levels of MSC-AS1, microRNA-373-3p (miR-373-3p), and cytoplasmic polyadenylation element binding protein 4 (CPEB4) were determined by quantitative real-time polymerase chain reaction (qRT-PCR). All protein expression was detected by western blot. Cell viability and the half maximal inhibitory concentration (IC₅₀) value of TMZ was assessed by cell counting kit-8 (CCK-8) assay. Cell cloning ability and apoptosis were examined by colony formation and flow cytometry assays, respectively. Dual-luciferase reporter and RNA immunoprecipitation (RIP) assays were performed to verify the correlation between miR-373-3p and MSC-AS1 or CPEB4. The xenograft models were established to determine the effect of MSC-AS1 in vivo. MSC-AS1 was up-regulated in TMZ-resistant glioma tissues and cells, and glioma patients with high MSC-AS1 expression tend to have lower overall survival rate. MSC-AS1 suppression reduced the IC₅₀ value of TMZ and proliferation, promoted apoptosis and TMZ sensitivity, and affected PI3K/Akt pathway in TMZ-resistant glioma cells. MSC-AS1 acted as miR-373-3p sponge, and miR-373-3p directly targeted CPEB4. Silencing miR-373-3p reversed the promoting effect of MSC-AS1 or CPEB4 knockdown on TMZ sensitivity. Furthermore, MSC-AS1 knockdown inhibited TMZ-resistant glioma growth in vivo by regulating miR-373-3p/CPEB4 axis through PI3K/Akt pathway. Collectively, MSC-AS1 knockdown suppressed cell growth and the chemoresistance of glioma cells to TMZ by regulating miR-373-3p/CPEB4 axis in vitro and in vivo through activating PI3K/Akt pathway.