Knockdown of SP1/Syncytin1 axis inhibits the proliferation and metastasis through the AKT and ERK1/2 signaling pathways in non-small cell lung cancer

Dual roles of human endogenous retroviruses in cancer progression and antitumor immune response

Human endogenous retroviruses (HERVs) are a class of transposable elements formed by the integration of ancient retroviruses into the germline genome. They are inherited in a Mendelian manner and approximately constitute 8 % of the human genome. HERVs were considered as "junk DNA" for decades, but increasing evidence suggests that they play significant roles in pathological inflammation, neural differentiation, and oncogenesis. Specifically, HERVs expression has been implicated in several oncogenic processes and the formation of the tumor microenvironment. Indeed, the dual roles of HERVs in cancer, serving as both promoters of oncogenesis and forerunners of the innate antitumor immune response, remain a subject of debate. In this review, we will discuss how HERVs participate in cancer progression and how they are regulated. Our aim is to provide a comprehensive understanding of the fundamental properties and potential function of HERVs in propagating oncogenesis and activating the antitumor immune response. We hope that updated knowledge will reshape our understanding of the critical roles played by HERVs in human evolution and cancer progression.

How Much Do You Fuse? A Comparison of Cell Fusion Assays in a Breast Cancer Model

Cell fusion is a biological process that is crucial for the development and homeostasis of different tissues, but it is also pathophysiologically associated with tumor progression and malignancy. The investigation of cell fusion processes is difficult because there is no standardized marker. Many studies therefore use different systems to observe and quantify cell fusion in vitro and in vivo. The comparability of the results must be critically questioned, because both the experimental procedure and the assays differ between studies. The comparability of the fluorescence-based fluorescence double reporter (FDR) and dual split protein (DSP) assay was investigated as part of this study, in which general conditions were kept largely constant. In order to be able to induce both a high and a low cell fusion rate, M13SV1 breast epithelial cells were modified with regard to the expression level of the fusogenic protein Syncytin-1 and its receptor ASCT2 and were co-cultivated for 72 h with different breast cancer cell lines. A high number of fused cells was found in co-cultures with Syncytin-1-overexpressing M13SV1 cells, but differences between the assays were also observed. This shows that the quantification of cell fusion events in particular is highly dependent on the assay selected, but the influence of fusogenic proteins can be visualized very well.

Cell Fusion and Syncytia Formation in Cancer

The natural phenomenon of cell-cell fusion does not only take place in physiological processes, such as placentation, myogenesis, or osteoclastogenesis, but also in pathophysiological processes, such as cancer. More than a century ago postulated, today the hypothesis that the fusion of cancer cells with normal cells leads to the formation of cancer hybrid cells with altered properties is in scientific consensus. Some studies that have investigated the mechanisms and conditions for the fusion of cancer cells with other cells, as well as studies that have characterized the resulting cancer hybrid cells, are presented in this review. Hypoxia and the cytokine TNFα, for example, have been found to promote cell fusion. In addition, it has been found that both the protein Syncytin-1, which normally plays a role in placentation, and phosphatidylserine signaling on the cell membrane are involved in the fusion of cancer cells with other cells. In human cancer, cancer hybrid cells were detected not only in the primary tumor, but also in the circulation of patients as so-called circulating hybrid cells, where they often correlated with a worse outcome. Although some data are available, the questions of how and especially why cancer cells fuse with other cells are still not fully answered.

SP1-activated USP27X-AS1 promotes hepatocellular carcinoma progression via USP7-mediated AKT stabilisation

BACKGROUND

Hepatocellular carcinoma (HCC) continues to pose a significant threat to patient survival. Emerging evidence underscores the pivotal involvement of long non-coding RNAs (lncRNAs) in the cancer process. Nevertheless, our understanding of the roles and processes of lncRNAs in HCC remains limited.

METHODS

The expression level of USP27X-AS1 was assessed in an HCC patient cohort through a combination of bioinformatics analysis and qRT-PCR. Subsequent biological experiments were conducted to delve into the functional aspects of USP27X-AS1. Additional molecular biology techniques, including RNA pulldown and RNA immunoprecipitation (RIP), were employed to elucidate the potential mechanisms involving USP27X-AS1 in HCC. Finally, CUT-RUN assay and other investigations were carried out to determine the factors contributing to the heightened expression of USP27X-AS1 in HCC.

RESULTS

High expression of the novel oncogene USP27X-AS1 predicted poor prognosis in HCC patients. Further investigation confirmed that USP27X-AS1 promoted the proliferation and metastasis of HCC by enabling USP7 to interact with AKT, which reduced level of AKT poly-ubiquitylation and enhanced AKT protein stability, which improves protein stabilisation of AKT and promotes the progression of HCC. Moreover, we also revealed that SP1 binds to USP27X-AS1 promoter to activate its transcription.

CONCLUSIONS

Novel oncogenic lncRNA USP27X-AS1 promoted HCC progression via recruiting USP7 to deubiquitinate AKT. SP1 transcriptionally activated USP27X-AS1 expression. These findings shed light on HCC and pointed to USP27X-AS1 as a potential predictive biomarker and treatment target for the malignancy.

Knockdown of HDAC10 inhibits POLE2-mediated DNA damage repair in NSCLC cells by increasing SP1 acetylation levels

HDAC10 has been reported to be associated with poor prognosis in patients with non-small cell lung cancer (NSCLC), however, the regulatory role and mechanisms of HDAC10 in NSCLC have not been investigated. In this study, we found that HDAC10 was increased in NSCLC patients and cell lines. And high expression of HDAC10 is linked to poor survival in NSCLC patients. The results showed that knockdown of HDAC10 triggered DNA damage, S-phase arrest, and proliferation inhibition in A549 and H1299 cells. In addition, knockdown of HDAC10 promoted cell ferroptosis by enhancing ROS, MDA and Fe2+ levels. Mechanistically, HDAC10 knockdown reduced SP1 expression and elevated the acetylation level of SP1, which inhibited the binding of SP1 to the promoter of POLE2, resulting in reduced POLE2 expression. Overexpression of SP1 or POLE2 partially reversed the effects of HDAC10 deletion on NSCLC cell proliferation and ferroptosis. In conclusion, knockdown of HDAC10 inhibited the proliferation of NSCLC cells and promoted their ferroptosis by regulating the SP1/POLE2 axis. HDAC10 might be a promising target for the treatment of NSCLC.

Molecular mechanisms of syncytin-1 in tumors and placental development related diseases

Human endogenous retroviruses (HERVs) have evolved from exogenous retroviruses and account for approximately 8% of the human genome. A growing number of findings suggest that the abnormal expression of HERV genes is associated with schizophrenia, multiple sclerosis, endometriosis, breast cancer, bladder cancer and other diseases. HERV-W env (syncytin-1) is a membrane glycoprotein which plays an important role in placental development. It includes embryo implantation, fusion of syncytiotrophoblasts and of fertilized eggs, and immune response. The abnormal expression of syncytin-1 is related to placental development-related diseases such as preeclampsia, infertility, and intrauterine growth restriction, as well as tumors such as neuroblastoma, endometrial cancer, and endometriosis. This review mainly focused on the molecular interactions of syncytin-1 in placental development-related diseases and tumors, to explore whether syncytin-1 can be an emerging biological marker and potential therapeutic target.

NUSAP1 Binds ILF2 to Modulate R-Loop Accumulation and DNA Damage in Prostate Cancer

Increased expression of NUSAP1 has been identified as a robust prognostic biomarker in prostate cancer and other malignancies. We have previously shown that NUSAP1 is positively regulated by E2F1 and promotes cancer invasion and metastasis. To further understand the biological function of NUSAP1, we used affinity purification and mass spectrometry proteomic analysis to identify NUSAP1 interactors. We identified 85 unique proteins in the NUSAP1 interactome, including ILF2, DHX9, and other RNA-binding proteins. Using proteomic approaches, we uncovered a function for NUSAP1 in maintaining R-loops and in DNA damage response through its interaction with ILF2. Co-immunoprecipitation and colocalization using confocal microscopy verified the interactions of NUSAP1 with ILF2 and DHX9, and RNA/DNA hybrids. We showed that the microtubule and charged helical domains of NUSAP1 were necessary for the protein-protein interactions. Depletion of ILF2 alone further increased camptothecin-induced R-loop accumulation and DNA damage, and NUSAP1 depletion abolished this effect. In human prostate adenocarcinoma, NUSAP1 and ILF2 mRNA expression levels are positively correlated, elevated, and associated with poor clinical outcomes. Our study identifies a novel role for NUSAP1 in regulating R-loop formation and accumulation in response to DNA damage through its interactions with ILF2 and hence provides a potential therapeutic target.

Decreased expression and DNA hypermethylation of syncytin-1 in human villus tissues with unexplained recurrent spontaneous abortion

Recurrent spontaneous abortion (RSA) affects approximately 5 % of women of reproductive age worldwide. The etiology and pathogenesis of approximately 50 % of RSA cases currently remain unclear, which known as unexplained RSA (URSA). Syncytin-1, an envelope protein encoded by HERV-W gene, is essential for human embryonic development. The purpose of this study was to explore the correlation between syncytin-1 expression and URSA occurrence. The villi tissues of URSA patients and patients with voluntary termination of pregnancy for non-medical reasons in early pregnancy (Control group) were collected. Compared with the Control group, syncytin-1 was abnormally low expressed in URSA villus tissues, and the HERV-W gene promoter was hypermethylated. Compared with the control group, the global DNA methylation level and the expression level of DNA methylases in the villus tissues of the URSA group had no significant difference. In addition, compared with the Control group, URSA villus tissue showed obviously abnormal apoptosis. Overexpression of syncytin-1 promoted the proliferation of HTR-8 cells and inhibited their apoptosis; while knockdown of syncytin-1 inhibited cell proliferation and promoted cell apoptosis. URSA villus tissue exhibited hypermethylation of the HERV-W gene and down-regulation of syncytin-1 expression. Syncytin-1 has the potential to be a predictive and diagnostic biomarker for URSA.

Serum circulating free DNA of syncytin-1 as a novel molecular marker for early diagnosis of non-small-cell lung cancer

Background: Liquid biopsy has been receiving attention as an emerging detection technology in the clinical application of non-small-cell lung cancer (NSCLC). Methods: We quantified serum circulating free DNA (cfDNA) of syncytin-1 in 126 patients and 106 controls, analyzed the correlation of level with pathological parameters and explored diagnostic utility. Results: The cfDNA of syncytin-1 levels in NSCLC patients were higher than healthy controls (p < 0.0001). These levels were associated with smoking history (p = 0.0393). The area under the curve of cfDNA of syncytin-1 was 0.802, and combination of cfDNA of syncytin-1/cytokeratin 19 fragment antigen 21-1/carcinoembryonic antigen markers improved diagnostic efficiency. Conclusion: The cfDNA of syncytin-1 was detected in NSCLC patients and can be used as a novel molecular marker for early diagnosis.

Transcriptional and reverse transcriptional regulation of host genes by human endogenous retroviruses in cancers

Human endogenous retroviruses (HERVs) originated from ancient retroviral infections of germline cells millions of years ago and have evolved as part of the host genome. HERVs not only retain the capacity as retroelements but also regulate host genes. The expansion of HERVs involves transcription by RNA polymerase II, reverse transcription, and re-integration into the host genome. Fast progress in deep sequencing and functional analysis has revealed the importance of domesticated copies of HERVs, including their regulatory sequences, transcripts, and proteins in normal cells. However, evidence also suggests the involvement of HERVs in the development and progression of many types of cancer. Here we summarize the current state of knowledge about the expression of HERVs, transcriptional regulation of host genes by HERVs, and the functions of HERVs in reverse transcription and gene editing with their reverse transcriptase.

eEF-2K knockdown synergizes with STS treatment to inhibit cell proliferation, migration, and invasion via the TG2/ERK pathway in A549 cells

Emerging research has suggested the anticancer potential of tanshinone IIA, the bioactive ingredient isolated from the traditional Chinese herb Salvia miltiorrhiza. However, the molecular mechanism of sodium tanshinone IIA sulfonate (STS) antilung cancer effect is not very clear. In this study, our purpose is to investigate the roles of STS and elongation factor-2 kinase (eEF-2K) in regulating the proliferation, migration, and invasion of A549 cells and explore the implicated pathways. We found that STS suppressed A549 cell survival and proliferation in a time- and xdose-dependent manner. Knockdown of eEF-2K and treatment with STS synergistically exerted antiproliferative, -migratory, and -invasive effects on A549 cells. These effects were caused by attenuation of the extracellular signal-regulated kinase (ERK) pathway via inhibition of tissue transglutaminase (TG2). In summary, the inhibition of eEF-2K synergizes with STS treatment, exerting anticancer effects on lung adenocarcinoma cells through the TG2/ERK signaling pathway, which provides a potential therapeutic target for treating lung adenocarcinoma.

Prognostic Significance and Therapeutic Target of CXC Chemokines in the Microenvironment of Lung Adenocarcinoma

Background

Lung adenocarcinoma (LUAD) is one of the most important subtypes of lung cancer and has a high morbidity and mortality. Inflammatory CXC chemokines in tumor microenvironment can stimulate tumor growth, invasion, and metastasis, affecting the prognosis of patients. However, the differential expression profiles, prognostic values, and specific mechanisms of the CXC chemokine family in LUAD have not been clarified.

Methods

Transcriptome expression profile data were extracted from TIMER and TCGA. GEPIA was used to compare the relationship between CXC chemokines and clinicopathologic parameters. The prognostic analysis was performed using a Kaplan–Meier curve in GEPIA. LinkedOmics and TRRUST were applied to conduct the enrichment analysis of the regulatory networks containing the kinase targets, miRNA targets, and transcriptional factor targets. The characteristics of immune infiltration and immune-related clinical outcomes were evaluated with TIMER algorithms. Single-cell RNA sequencing localization analysis of genes as prognostic biomarkers were performed by PanglaoDB.

Results

Nine differentially expressed genes were identified in LUAD compared to normal tissues. Aberrant expression of CXCL2 (P =0.0017), CXCL13 (P= 0.0271), CXCL16 (P= 0.016), and CXCL17 (P= 2.14e-5) was significantly correlated with clinical cancer stage. Furthermore, patients with low gene transcription of CXCL 7 (P = 0.017) and high expression of CXCL 17 (P = 0.00045) had a better prognosis in LUAD. We also found that immune cell infiltration was significantly correlated with LUAD microenvironment mediated by CXC chemokines. Cox proportional hazard model test was conducted and indicated that B cell infiltration could prolong the survival of the LUAD patients. CXCL17 exerted anti-tumors effect through pulmonary alveolar type II cells according to single-cell analysis.

Conclusion

Our research identified the aberrant expression profiles and prognostic biomarkers of CXC chemokines in LUAD. This detailed analysis of the regulatory factor networks for CXC chemokine gene expression may provide novel insights for selecting potential immunotherapeutic targets.

Sp1 Plays a Key Role in Vasculogenic Mimicry of Human Prostate Cancer Cells

Sp1 transcription factor regulates genes involved in various phenomena of tumor progression. Vasculogenic mimicry (VM) is the alternative neovascularization by aggressive tumor cells. However, there is no evidence of the relationship between Sp1 and VM. This study investigated whether and how Sp1 plays a crucial role in the process of VM in human prostate cancer (PCa) cell lines, PC-3 and DU145. A cell viability assay and three-dimensional culture VM tube formation assay were performed. Protein and mRNA expression levels were detected by Western blot and reverse transcriptase-polymerase chain reaction, respectively. The nuclear twist expression was observed by immunofluorescence assay. A co-immunoprecipitation assay was performed. Mithramycin A (MiA) and Sp1 siRNA significantly decreased serum-induced VM, whereas Sp1 overexpression caused a significant induction of VM. Serum-upregulated vascular endothelial cadherin (VE-cadherin) protein and mRNA expression levels were decreased after MiA treatment or Sp1 silencing. The protein expression and the nuclear localization of twist were increased by serum, which was effectively inhibited after MiA treatment or Sp1 silencing. The interaction between Sp1 and twist was reduced by MiA. On the contrary, Sp1 overexpression enhanced VE-cadherin and twist expressions. Serum phosphorylated AKT and raised matrix metalloproteinase-2 (MMP-2) and laminin subunit 5 gamma-2 (LAMC2) expressions. MiA or Sp1 silencing impaired these effects. However, Sp1 overexpression upregulated phosphor-AKT, MMP-2 and LAMC2 expressions. Serum-upregulated Sp1 was significantly reduced by an AKT inhibitor, wortmannin. These results demonstrate that Sp1 mediates VM formation through interacting with the twist/VE-cadherin/AKT pathway in human PCa cells.

Propofol mediates pancreatic cancer cell activity through the repression of ADAM8 via SP1

Propofol is a commonly used anesthetic with controversial effects on cancer cells. A growing number of studies have demonstrated that low concentrations of propofol are associated with tumor suppression and when used as an intravenous anesthesia improved recurrence‑free survival rates for many cancers, but deeper insights into its underlying mechanism are needed. The study detailed herein focused upon the effect of propofol on pancreatic cancer cells and the mechanism by which propofol reduces A disintegrin and metalloproteinase 8 (ADAM8) expression. The ability of propofol to impact the proliferation, migration and cell cycle of pancreatic cancer cell lines was assessed in vitro. This was mechanistically explored following the identification of SP1 binding sites within ADAM8, which enabled the regulatory effects of specificity protein 1 (SP1) on ADAM8 following propofol treatment to be further explored. Ultimately, this study was able to show that propofol significantly inhibited the proliferation, migration and invasion of pancreatic cancer cells and decreased the percentage of cells in S‑phase. Propofol treatment was also shown to repress ADAM8 and SP1 expression, but was unable to affect ADAM8 expression following knockdown of SP1. Moreover, a direct physical interaction between SP1 and ADAM8 was verified using co‑immunoprecipitation and dual‑luciferase reporter assays. Cumulatively, these results suggest that propofol represses pathological biological behaviors associated with pancreatic cancer cells through the suppression of SP1, which in turn results in lower ADAM8 mRNA expression and protein levels.

Radiosensitizing effect of gold nanoparticle loaded with small interfering RNA-SP1 on lung cancer: AuNPs-si-SP1 regulates GZMB for radiosensitivity

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siRNA-SP1-loaded AuNPs (AuNPs-si-SP1) inhibits SP1 expression in lung cancer cells.

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GZMB expression is elevated by silencing SP1 in lung cancer cells.

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AuNPs-si-SP1 combined with radiotherapy inhibits lung cancer growth effectively.

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AuNPs-si-SP1 enhances radiosensitivity of lung cancer via SP1/GZMB axis.

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AuNPs-si-SP1 provides a novel target for radiotherapy of lung cancer.

Radioresistance is a major challenge that largely limits the efficacy of radiotherapy in lung cancer. Gold nanoparticles (AuNPs) are emerging as novel radiosensitizers for cancer patients. Therefore, this study was designed to explore the radiosensitizing effect and mechanism of AuNPs loaded with small interfering RNA (siRNA)-SP1 (AuNPs-si-SP1) on lung cancer. AuNPs-si-SP1 was prepared by the noncovalent binding between AuNPs and siRNA-SP1. The adsorption capacity of AuNPs to siRNA-SP1 was analyzed by gel electrophoresis. The cell uptake of AuNPs-si-SP1 was observed under a laser confocal microscopy. Silencing efficacy of AuNPs-si-SP1 was validated by RT-qPCR and Western blot analysis. Cell viability was determined by CCK-8 assay, radiosensitization by plate colony formation assay, cell apoptosis and cell cycle by flow cytometry, and DNA double strand breaks by immunofluorescence in the presence or absence of AuNPs-si-SP1 or GZMB. The downstream mechanism of SP1 was predicted by bioinformatics analysis, followed by verification by Western blot analysis. Subcutaneous tumorigenesis in nude mice was established to verify the radiosensitization of AuNPs-si-SP1 and GZMB in vivo. AuNPs-si-SP1 effectively absorbed SP1 siRNA and was highly internalized by A549 cells to reduce SP1 protein expression. AuNPs-si-SP1 or GZMB overexpression promoted cells to G2/M phase, DNA double strand breaks, and enhanced radiosensitivity. SP1 could repress GZMB expression in lung cancer cells. In vivo experiments manifested that AuNPs-si-SP1 could inhibit the growth of solid tumor in nude mice to achieve radiosensitization by inhibiting SP1 to upregulate GZMB. AuNPs-si-SP1 might increase the radiosensitivity of lung cancer by inhibiting SP1 to upregulate GZMB.

An Ancestral Retrovirus Envelope Protein Regulates Persistent Gammaherpesvirus Lifecycles

Human gammaherpesviruses Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV) persist as life-long infections alternating between latency and lytic replication. Human endogenous retroviruses (HERVs), via integration into the host genome, represent genetic remnants of ancient retroviral infections. Both show similar epigenetic silencing while dormant, but can reactivate in response to cell signaling cues or triggers that, for gammaherpesviruses, result in productive lytic replication. Given their co-existence with humans and shared epigenetic silencing, we asked if HERV expression might be linked to lytic activation of human gammaherpesviruses. We found ERVW-1 mRNA, encoding the functional HERV-W envelope protein Syncytin-1, along with other repeat class elements, to be elevated upon lytic activation of EBV. Knockdown/knockout of ERVW-1 reduced lytic activation of EBV and KSHV in response to various lytic cycle triggers. In this regard, reduced expression of immediate early proteins ZEBRA and RTA for EBV and KSHV, respectively, places Syncytin-1's influence on lytic activation mechanistically upstream of the latent-to-lytic switch. Conversely, overexpression of Syncytin-1 enhanced lytic activation of EBV and KSHV in response to lytic triggers, though this was not sufficient to induce lytic activation in the absence of such triggers. Syncytin-1 is expressed in replicating B cell blasts and lymphoma-derived B cell lines where it appears to contribute to cell cycle progression. Together, human gammaherpesviruses and B cells appear to have adapted a dependency on Syncytin-1 that facilitates the ability of EBV and KSHV to activate lytic replication from latency, while promoting viral persistence during latency by contributing to B cell proliferation.

Advanced bioinformatic analysis and pathway prediction of NSCLC cells upon cisplatin resistance

This study aims to identify pathway involvement in the development of cisplatin (cis-diamminedichloroplatinum (II); CDDP) resistance in A549 lung cancer (LC) cells by utilizing advanced bioinformatics software. We developed CDDP-resistant A549 (A549/DDP) cells through prolonged incubation with the drug and performed RNA-seq on RNA extracts to determine differential mRNA and miRNA expression between A549/DDP and A549 cells. We analyzed the gene dysregulation with Ingenuity Pathway Analysis (IPA; QIAGEN) software. In contrast to prior research, which relied on the clustering of dysregulated genes to pathways as an indication of pathway activity, we utilized the IPA software for the dynamic evaluation of pathway activity depending on the gene dysregulation levels. We predicted 15 pathways significantly contributing to the chemoresistance, with several of them to have not been previously reported or analyzed in detail. Among them, the PKR signaling, cholesterol biosynthesis, and TEC signaling pathways are included, as well as genes, such as PIK3R3, miR-34c-5p, and MDM2, among others. We also provide a preliminary analysis of SNPs and indels, present exclusively in A549/DDP cells. This study's results provide novel potential mechanisms and molecular targets that can be explored in future studies and assist in improving the understanding of the chemoresistance phenotype.

Long Non-Coding RNA LINC00491 Contributes to the Malignancy of Non-Small-Cell Lung Cancer via Competitively Binding to microRNA-324-5p and Thereby Increasing Specificity Protein 1 Expression

Background

A long non-coding RNA termed as long intergenic non-protein coding RNA 491 (LINC00491) has been validated as an oncogene to promote cancer progression in colon adenocarcinoma. The goal of this study was to determine the expression and carcinogenic functions of LINC00491 in non-small-cell lung cancer (NSCLC). Besides, it was aimed to understand how LINC00491 affects the malignant processes of NSCLC cells.

Methods

The expression of LINC00491 in NSCLC was investigated by bioinformatic analysis and reverse transcription-quantitative PCR. After LINC00491 knockdown, cell counting kit-8 assay, flow cytometry, migration and invasion detection assays as well as nude mice xenograft assay were conducted to test the roles of LINC00491 in NSCLC cells. Two online databases, StarBase 3.0 and miRDB, were utilized to determine the putative target miRNA of LINC00491, and the prediction was subsequently confirmed by luciferase reporter assay, RNA immunoprecipitation assay, reverse transcription-quantitative PCR, Western blotting, and rescue assays.

Results

LINC00491 was overexpressed in both NSCLC tissues and cell lines. Functional investigation revealed that depleted LINC00491 facilitated cell apoptosis and decreased cell proliferation, migration, and invasion in vitro. Additionally, the downregulation of LINC00491 impaired NSCLC cell tumor growth in vivo. Mechanistically, LINC00491 functioned as a competing endogenous RNA by sponging microRNA-324-5p (miR-324-5p) in NSCLC cells. miR-324-5p was weakly expressed in NSCLC and exerted tumor-suppressing actions during cancer progression. Furthermore, specificity protein 1 (SP1) was validated as the direct target of miR-324-5p in NSCLC and was under the regulation of LINC00491 via sponging miR-324-5p. Rescue experiments reconfirmed that miR-324-5p inhibition and SP1 overexpression both abrogated the suppressive roles of LINC00491 deficiency in NSCLC cells.

Conclusion

LINC00491 promoted the oncogenicity of NSCLC via serving as a miR-324-5p sponge, which further upregulated the expression of SP1. The LINC00491/miR-324-5p/SP1 pathway disclosed a new mechanism of NSCLC pathogenesis and may provide effective targets for better NSCLC treatment.

circ_ARF3 regulates the pathogenesis of osteosarcoma by sponging miR-1299 to maintain CDK6 expression

Increasing evidence suggests that circular RNAs are emerging biomarkers or targets for early cancer diagnosis and treatment. However, the studies of circular RNA in osteosarcoma (OS) are limited. In this study we found that circ_ARF3 were highly expressed in osteosarcoma cell lines and tumor tissues. Knocking down circ_ARF3 greatly ceased OS cell growth, impaired cell colony formation and halted cell cycle transition from G1 to S phase. Bioinformatic analysis suggested that miR-1299 is the target of circ_ARF3. Luciferase assay and biotin labeled circ_ARF3 pull down assay confirmed their interactions in OS cells. The regulatory roles of circ_ARF3 on miR-1299 was also investigated. Further bioinformatic analysis showed that CDK6 is the target of miR-1299. Overexpressing miR-1299 in OS cells decreased CDK6 expression and arrested OS cell growth and cell cycle progression. However, the roles of miR-1299 in regulating CDK6 expression, OS cell growth and cell cycle progression were greatly impaired in the presence of circ_ARF3. In general, our study demonstrated that in the OS, highly expressed circ_ARF3 acts as a sponge of miR-1299 to inhibit miR-1299 mediated CDK6 downregulation which further promoted OS pathogenesis. circ_ARF3 could be a potential target for OS treatment in the future.

RNA binding proteins involved in regulation of protein synthesis to initiate biogenesis of secondary tumor in hepatocellular carcinoma in mice

Background

The tumor microenvironment (TM) in close contact with cancer cells is highly related to tumor growth and cancer metastasis. This study is to explore the biogenesis mechanism of a secondary hepatocellular carcinoma (HCC) based on the function of RNA binding proteins (RBPs)-encoding genes in the physiological microenvironment (PM).

Methods

The healthy and HCC mice were used to isolate the PM, pre-tumor microenvironment (PTM), and TM. The samples were analyzed using the technology of RNA-seq and bioinformatics. The differentially expressed RBPs-encoding genes (DERs) and differentially expressed DERs-associated genes (DEDs) were screened to undergo GO and KEGG analysis.

Results

18 DERs and DEDs were identified in the PTM vs. PM, 87 in the TM vs. PTM, and 87 in the TM vs. PM. Those DERs and DEDs participated in the regulation of gene expression at the levels of chromatin conformation, gene activation and silencing, splicing and degradation of mRNA, biogenesis of piRNA and miRNA, ribosome assemble, and translation of proteins.

Conclusion

The genes encoding RBPs and the relevant genes are involved in the transformation from PM to PTM, then constructing the TM by regulating protein synthesis. This regulation included whole process of biological genetic information transmission from chromatin conformation to gene activation and silencing to mRNA splicing to ribosome assemble to translation of proteins and degradation of mRNA. The abnormality of those functions in the organic microenvironments promoted the metastasis of HCC and initiated the biogenesis of a secondary HCC in a PM when the PM encountered the invasion of cancer cells.

Knockdown of SP1/Syncytin1 axis inhibits the proliferation and metastasis through the AKT and ERK1/2 signaling pathways in non-small cell lung cancer

Syncytin 1 is considered as an oncogene in various malignant tumors, but its effect on non-small cell lung cancer (NSCLC) has not been reported. We investigated the specific role of Syncytin 1 on NSCLC through the transfection of Syncytin 1 knockdown or overexpression plamids in A549 cells. Our results proved that knockdown of Syncytin 1 inhibited the proliferation, and blocked the cell cycle on G1 phase by inhibiting the expression of Nusap1, Cyclin D1, CDK6, and CDK4. Cell cycle arrest also leaded to increased apoptosis in Syncytin 1 knockdown cells. Suppression of Syncytin 1 inhibited the migration and invasion, as well as the expressions of epithelial-mesenchymal transition (EMT) makers, N-cadherin, β-catenin, and Vimentin, indicating that Syncytin 1 knockdown inhibited the metastasis via reversing the EMT process in A549 cells. The phosphorylation levels of Akt, mTOR, and Erk1/2 were all decreased in Syncytin 1 knockdown cells, suggesting the signaling pathways by which Syncytin 1 operated as an oncogene in NSCLC. Moreover, the underexpression of transcription factor SP1 downregulated the Syncytin 1 expression in A549 cells. The rescue experiment of Syncytin 1 in SP1 knockdown cells further proved that Syncytin 1 could block the inhibition of cell growth induced by SP1 knockdown. In conclusion, knockdown of SP1/Syncytin1 axis inhibited the progression of NSCLC by the reversion of tumor epithelial-mesenchymal transition process and suppression of Akt and Erk signaling pathways, suggesting that they are potential targets for targeted therapy of NSCLC.