LINC00665 promotes glycolysis in lung adenocarcinoma cells via the let-7c-5p/HMMR axis

Lung adenocarcinoma (LUAD) is one of the most lethal and common malignancies. The energy metabolism of LUAD is a critical factor affecting its malignant progression, and research on this topic can aid in the development of novel cancer treatment targets. Bioinformatics analysis of the expression of long non-coding RNA (lncRNA) LINC00665 in LUAD was performed. Downstream regulatory molecules of LINC00665 were predicted using the StarBase database. We used quantitative reverse transcription polymerase chain reaction and western blot to measure the expression at mRNA and protein levels, respectively. The effects of the LINC00665/let-7c-5p/HMMR axis on cell viability in vitro were tested by CCK-8 assay. The regulatory effects on glycolysis were analyzed by extracellular acidification rate, oxygen consumption rate, glucose uptake, adenosine triphosphate production, and lactate production. The predicted competitive endogenous RNA mechanism between LINC00665 and let-7c-5p/HMMR was verified by a dual-luciferase reporter gene assay. LINC00665 was upregulated in LUAD. Silencing LINC00665 inhibited tumor proliferation and reduced the glycolytic activity of tumor cells. Additionally, the expression of LINC00665 had a negative correlation with that of let-7c-5p, while the expression of HMMR was remarkably inhibited by let-7c-5p. HMMR could affect the development of LUAD by influencing glycolytic capacity. Mechanistically, LINC00665 acted as a molecular sponge to absorb let-7c-5p and targeted HMMR. Transfection of let-7c-5p inhibitor or overexpression of HMMR plasmid could reverse the inhibition in proliferation and glycolysis of LUAD cells induced by silencing of LINC00665. In summary, this study demonstrated that the LINC00665/let-7c-5p/HMMR regulatory axis promoted the tumorigenesis of LUAD by enhancing aerobic glycolysis, suggesting that this regulatory axis was an effective target for inhibiting LUAD progression and providing theoretical support for the development of new drugs for LUAD.

LINC00665 target let-7i/HMGA1 promotes the proliferation and invasion of hepatoma cells

OBJECTIVES

Our group previously found that LINC00665 was upregulated in hepatocellular carcinoma (HCC) tissues through database analysis; however, the potential molecular mechanism of LINC00665 in HCC progression still needs further study.

METHODS

qRTPCR was performed to determine the differential expression of LINC00665 and let-7i in HCC cells. Dual-luciferase reporter assays were performed to analyze the interaction of LINC00665 and let-7i. CCK-8 assays, scratch assays, Transwell invasion assays, qRTPCR and western blotting were performed to determine the regulatory mechanism of LINC00665/let-7i/HMGA1 in HCC cells.

RESULTS

LINC00665 was upregulated in HCC cells compared with normal hepatocytes. A potential binding site between LINC00665 and let-7i was confirmed by dual-luciferase reporter assay. In HCC cells, inhibition of LINC00665 significantly reduced cell proliferation, migration and invasion ability via the let-7i/HMGA1 signaling axis.

CONCLUSION

LINC00665 promotes the proliferation and invasion of HCC cells via the let-7i/HMGA1 signaling axis.

LINC00665: A Promising Biomarker in Gastrointestinal Tumors

An increasing volume of studies has reported that long non-codingRNAs (lncRNAs) are involved in the carcinogenesis of many different cancers. Especially in gastrointestinal tumors, lncRNAs are found to participate in various physiological and pathological processes. LncRNAs can regulate gene expression at multiple levels, including transcriptional, post-transcription, translational, and post-translational levels. Long intergenic non-protein coding RNA 665(LINC00665), a novel cancer-related lncRNA, is frequently dysregulated in multiple gastrointestinal tumors, including gastric and colorectal cancers, hepatocellular carcinoma, and so on. In this review, we analyzed the expression and prognostic value of LINC00665 in human gastrointestinal tumors, systematically summarized the current literature about the clinical significance of this lncRNA, and explored the regulatory mechanisms of LINC00665 as a competing endogenous RNA (ceRNA) in tumor progression. Consequently, we concluded that LINC00665 might act as a prognostic biomarker and a potential target for gastrointestinal tumor diagnosis and treatment.

Long noncoding RNA LINC00665 is a diagnostic biomarker that enhances cell proliferation and migration in hepatocellular carcinoma

BACKGROUND

This study aimed to evaluate the relationship between LINC00665 expression levels and the risk of hepatocellular carcinoma (HCC) in Chinese Han nationality patients and to explore the influence of LINC00665 dysregulation on the proliferation and migration potential of HCC cells.

PATIENTS AND METHODS

We investigated the expression of LINC00665 in The Cancer Genome Atlas (TCGA) database. Then, we confirmed the expression of LINC00665 in 54 pairs of surgical tissues from HCC patients and in liver cancer cell lines by quantitative real-time polymerase chain reaction. Furthermore, we manipulated the expression level of LINC00665 and examined the cell proliferation and migration abilities of HCC cells.

RESULTS

In the TCGA cohort, a high level of LINC00665 in patients with HCC was significantly associated with tumor stage, tumor differentiation grade, and overall survival. In our HCC patient cohort, overexpression of LINC00665 in patients showed positive correlations with alpha-fetoprotein level, Barcelona Clinic Liver Cancer stage, and tumor differentiation grade. In addition, LINC00665 was upregulated in HCC cells, especially in cells with rapid growth rates and high migration abilities. A new LINC00665 isoform with a length of 1,371 nucleotides was identified in MHCC-97H cells. Interfering with LINC00665 expression weakened the proliferation and migration abilities of HCC cells. In contrast, LINC00665 overexpression enhanced proliferation and migration abilities.

CONCLUSION

LINC00665 was upregulated in HCC tissues and cells and might be used to predict a poor prognosis of HCC patients. In addition, LINC00665 may promote the malignant progression of HCC by enhancing proliferation and migration capacities.

Thymidine kinase 1 as a target is regulated by the hsa-let-7b-5p/LINC00665 axis and affects NSCLC prognosis

Background

In the past, multiple studies have offered incremental evidence that indicates that competitive endogenous RNA (ceRNA) regulatory networks are involved in tumor growth and present novel therapeutic targets. Herein, we investigated the impact of thymidine kinase 1 (TK1)-related ceRNA networks on the prognosis of non-small cell lung cancer (NSCLC).

Methods

TK1 expression data in NSCLC and normal tissue samples were retrieved from the Cancer Genome Atlas (TCGA) database and were then compared. Thereafter, the findings of the immunohistochemical staining experiments and clinical follow-up data derived from patients with NSCLC were used for conducting prognostic analysis. The starBase database was searched to determine TK1-targeted microRNAs and long non-coding RNAs, and clinical data from TCGA were used for survival analysis to construct a ceRNA network associated with TK1 expression and prognosis. Finally, the roles played by methylation and immunity in the prognosis and treatment of NSCLC were analyzed.

Results

Our findings revealed that the cancer tissues expressed significantly higher TK1 levels than normal tissues, and the follow-up clinical data revealed that the prognosis was generally worse in the high-expression patients than in the low-expression patients. In addition, clinical data collected from the starBase and TCGA databases showed that the LINC00665/has-let-7b-5p/TK1 network could influence the growth and prognosis of NSCLC. It was also noted that the TK1 methylation site was correlated with the prognosis of NSCLC, and immunoprognostic analysis further indicated that patients with higher TK1 expression levels displayed a worse prognosis.

Conclusion

When the regulatory network of LINC00665/has-let-7b-5p/TK1 was assessed, it was observed that elevated TK1 levels may affect the prognosis of NSCLC. Therefore, it could be considered a prognostic biomarker and a probable therapeutic target for predicting NSCLC prognosis.

Prognostic and clinicopathological values of LINC00665 in cancers: a systematic review and China population-based meta-analysis

BACKGROUND

Recent studies have uncovered that the aberrant expression of LINC00665 contributes to the malignant pathological process of various cancers and is closely related to the unfavorable prognosis of patients with cancer. However, a systematic analysis of the prognostic and clinicopathologic values of LINC00665 in cancers has not been conducted.

OBJECTIVE

We aim to clarify the association of LINC00665 expression with patient survival and clinicopathologic phenotypes in cancers.

METHODS

An electronic search of PubMed, Embase and Web of Science was performed to select eligible literature. Pooled hazard ratio (HR) and odds ratio (OR) were calculated to assess the clinical importance of LINC00665. The fixed-effects model was used to analyze the combined HR values and 95% CI when the studies had no significant heterogeneity (P > 0.1 for the Chi-square test or I2 < 50%). Begg's test and sensitivity analysis were also conducted. This study was registered in The International Prospective Register of Systematic Reviews (PROSPERO registration number: CRD42021290123).

RESULTS

A total of 710 patients from 10 eligible studies were enrolled in this meta-analysis, which was based on China population. The pooled results of this analysis revealed that high-level expression of LINC00665 was notably correlated with poor overall survival (HR = 2.08, 95% CI = 1.57-2.75) and recurrence-free survival (HR = 2.49, 95% CI = 1.63-3.80) in human cancers. Elevated LINC00665 expression was also correlated with more advanced clinical stage, earlier lymph node metastasis, lower tumor differentiation, earlier distant metastasis and larger tumor size.

CONCLUSION

LINC00665 expression was critically related to the cancer prognosis, which has important prognostic implications for clinical prediction.

Blockage of MDM2-mediated p53 ubiquitination by yuanhuacine restrains the carcinogenesis of prostate carcinoma cells by suppressing LncRNA LINC00665

Prostate cancer (PCa) is a challenging issue for men's health worldwide due to its uncontrolled proliferation and high metastatic potential. Increasing evidence has supported plant extracts and natural plant derivatives as promising antitumor therapy with less toxic side effects. Yuanhuacine is an active component isolated from Daphne genkwa and can effectively suppress the tumorigenesis of several cancers. However, its role in PCa remains unclear. In this study, yuanhuacine dose-dependently inhibited the proliferation and induced apoptosis of PCa cells. Moreover, yuanhuacine also restrained the invasion and migration of PCa cells. Mechanically, yuanhuacine decreased the ubiquitination and degradation of p53 protein, and ultimately increased p53 levels, which was regulated by inhibiting the phosphorylation and total protein levels of mouse double minute 2 (MDM2). Moreover, elevation of MDM2 reversed the suppressive efficacy of yuanhuacine in PCa cell viability, invasion, and migration. The network pharmacologic and bioinformatics analysis confirmed that MDM2 might be a common target of D. genkwa and LINC00665. Furthermore, yuanhuacine inhibited LINC00665 expression. Upregulation of LINC00665 reversed yuanhuacine-mediated inhibition in MDM2 protein expression and suppressed p53 levels by enhancing its ubiquitination in yuanhuacine-treated cells. Importantly, the inhibitory effects of yuanhuacine on cell viability and metastatic potential were offset after LINC00665 elevation. Together, the current findings highlight that yuanhuacine may possess tumor-suppressive efficacy by inhibiting LINC00665-mediated MDM2/p53 ubiquitination signaling. Therefore, this study indicates that yuanhuacine may be a promising candidate for the treatment of PCa.

ncRNA-mediated low expression of P2RY14 correlates with poor prognosis and tumor immune infiltration in ovarian carcinoma

Background

Ovarian cancer (OV) has been puzzling clinicians because of its poor prognosis. More and more evidence show that the G protein coupled receptor P2RY14 plays a key role in the initiation and progression of various types of human cancer. The purpose of our study is to explore the correlation between P2RY14 and the prognosis of ovarian cancer patients and the relevant mechanism.

Methods

First, the differentially expressed gene P2RY14 was screened from The Cancer Genome Atlas (TCGA) database. Explored possible P2RY14 related miRNAs and lncRNAs through multiple public databases, predicted and analyzed the expression level of candidate miRNAs and candidate lncRNAs that can bind to candidate miRNAs in OV through StarBase database. The TIMER database was used to comprehensively analyze the expression of tumor infiltrating immune cells, and to analyze the correlation between the expression level of P2RY14 and the level of immune cell infiltration in OV or the expression level of immune checkpoints.

Results

Patients with P2RY14 overexpression had better overall survival (OS) and progression-free interval (PFI). In the Targetscan database, 22 upstream miRNAs that may bind to P2RY14 were predicted. According to the regulatory network constructed by the Cytoscape software, correlation analysis and the role of miRNAs in the prognosis of OV, we first determined that the candidate miRNAs were miR-34c-5p. Then, we predicted the upstream lncRNAs of miR-34c-5p in the StarBase database, the expression level of these lncRNAs in OV in the Gene Expression Profiling Interactive Analysis (GEPIA) database, and the role in prognosis. We determined that LINC00665 is the most potential lncRNA upstream of ovarian cancer miRNA (hsa-miR-34c-5p)-P2RY14. Then, we analyzed the results in the Timer database, suggesting that P2RY14 expression was positively correlated with CD8⁺T Cell, CD4⁺T Cell, Macrophage, Neutral and Dendritic cells, and negatively correlated with B cells. Meanwhile, P2RY14 was positively correlated with CD274 and PDCD1.

Conclusions

P2RY14 can be used as a new predictive biomarker of ovarian cancer. Intervention of P2RY14 can affect the prognosis of ovarian cancer by affecting LINC00665-miR-34c-5p-P2RY14 axis. These findings provide a potential target for the development of anti-cancer strategies for ovarian cancer.

A Feedback Loop of LINC00665 and the Wnt Signaling Pathway Expedites Osteosarcoma Cell Proliferation, Invasion, and Epithelial-Mesenchymal Transition

OBJECTIVES

Osteosarcoma (OS) is a malignant tumor with frequent occurrence among teenagers. Long non-coding RNAs (lncRNAs) play pro-cancer roles in many tumors. The purpose of this study was to figure out the functional role of a novel lncRNA long intergenic non-protein coding RNA 665 (LINC00665) in OS by observing the OS cell behaviors.

METHODS

Quantitative reverse transcription polymerase chain reaction (RT-qPCR) was used to analyze LINC00665 expression in OS cells. Cell function assays assessed the impacts of LINC00665 on OS cell phenotype. Immunofluorescence and western blot analyzed the function of LINC00665 on epithelial-mesenchymal transition (EMT) in OS. Moreover, mechanistic assays analyzed the downstream mechanism of LINC00665 in OS cells.

RESULTS

LINC00665 was significantly up-regulated in OS cells. LINC00665 silence facilitated OS cell proliferation, migration, invasion, and EMT while inhibiting cell apoptosis. Mechanically, LINC00665 acted as a competing endogenous RNA (ceRNA) to sponge miR-1249-5p and thereby modulated Wnt family member 2B (WNT2B) to activate Wnt pathway. Wnt pathway activated LINC00665 expression transcriptionally.

CONCLUSIONS

Our study uncovered the cancer-promoting role of LINC00665 in OS, and the feedback loop of LINC00665/miR-1249-5p/WNT2B/Wnt might be a potential target for OS treatment.

A Concise Review on Dysregulation of LINC00665 in Cancers

Long Intergenic Non-Protein Coding RNA 665 (LINC00665) is an RNA gene located on the minus strand of chromosome 19. This lncRNA acts as a competing endogenous RNA for miR-4458, miR-379-5p, miR-551b-5p, miR-3619-5p, miR-424-5p, miR-9-5p, miR-214-3p, miR-126-5p, miR-149-3p, miR-379-5p, miR-665, miR-34a-5p, miR-186-5p, miR-138-5p, miR-181c-5p, miR-98, miR-195-5p, miR-224-5p, miR-3619, miR-708, miR-101, miR-1224-5p, miR-34a-5p, and miR-142-5p. Via influencing expression of these miRNAs, it can enhance expression of a number of oncogenes. Moreover, LINC00665 can influence activity of Wnt/β-Catenin, TGF-β, MAPK1, NF-κB, ERK, and PI3K/AKT signaling. Function of this lncRNA has been assessed through gain-of-function tests and/or loss-of-function studies. Furthermore, diverse research groups have evaluated its expression levels in tissue samples using microarray and RT-qPCR techniques. In this manuscript, we have summarized the results of these studies and categorized them in three sections, i.e., cell line studies, animal studies, and investigations in clinical samples.

Hepatitis B Virus-Encoded HBsAg Contributes to Hepatocarcinogenesis by Inducing the Oncogenic Long Noncoding RNA LINC00665 through the NF-κB Pathway

Clinical and in vivo studies have demonstrated a role for hepatitis B virus (HBV)-encoded HBsAg (hepatitis B surface antigen) in HBV-related hepatocellular carcinoma (HCC); however, the underlying mechanisms remain largely unknown. Here, we investigated the role of HBsAg in regulating long noncoding RNAs (lncRNAs) involved in HCC progression. Our analysis of microarray data sets identified LINC00665 as an HBsAg-regulated lncRNA. Furthermore, LINC00665 is upregulated in liver samples from HBV-infected patients as well as in HCC, specifically in HBV-related HCC liver samples. These findings were supported by our in vitro data demonstrating that HBsAg, as well as HBV, positively regulates LINC00665 in multiple HBV cell culture models. Next, we evaluated the oncogenic potential of LINC00665 by its overexpression and CRISPR interference (CRISPRi)-based knockdown in various cell-based assays. LINC00665 promoted cell proliferation, migration, and colony formation but inhibited cell apoptosis in vitro. We then identified the underlying mechanism of HBsAg-mediated regulation of LINC00665. We used immunofluorescence assays to show that HBsAg enhanced the nuclear translocation of NF-κB factors in HepG2 cells, confirming that HBsAg activates NF-κB. Inhibition of NF-κB signaling nullified HBsAg-mediated LINC00665 upregulation, suggesting that HBsAg acts through NF-κB to regulate LINC00665. Furthermore, the LINC00665 promoter contains NF-κB binding sites, and their disruption abrogated HBsAg-induced LINC00665 upregulation. Finally, HBsAg facilitated the enrichment of the NF-κB factors NF-κB1, RelA, and c-Rel in the LINC00665 promoter. Taken together, this work shows that HBsAg can drive hepatocarcinogenesis by upregulating oncogenic LINC000665 through the NF-κB pathway, thereby identifying a novel mechanism in HBV-related HCC. IMPORTANCE Hepatitis B virus (HBV) is a major risk factor for hepatocellular carcinoma (HCC). Numerous reports indicate an oncogenic role for HBV-encoded HBsAg; however, the underlying mechanisms are not well understood. Here, we studied the role of HBsAg in regulating lncRNAs involved in hepatocarcinogenesis. We demonstrate that HBsAg, as well as HBV, positively regulates oncogenic lncRNA LINC00665. The clinical significance of this lncRNA is highlighted by our observation that LINC00665 is upregulated in liver samples during HBV infection and HBV-related HCC. Furthermore, we show LINC00665 can drive hepatocarcinogenesis by promoting cell proliferation, colony formation, and cell migration and inhibiting apoptosis. Taken together, this work identified LINC00665 as a novel gene through which HBsAg can drive hepatocarcinogenesis. Finally, we show that HBsAg enhances LINC00665 levels in hepatocytes by activating the NF-κB pathway, thereby identifying a novel mechanism by which HBV may contribute to HCC.

LncRNA LINC00665 Promotes Ovarian Cancer Cell Proliferation and Inhibits Apoptosis via Targeting miR-181a-5p/FHDC

Previous reports indicate that long intergenic non-coding RNA LINC00665 naturally occurred vital effects in various cancers. Herein, the role of LINC00665 in ovarian cancer progress was explored. We found that LINC00665 was upregulated in ovarian cancer cell lines. Besides, a series of assays including flow cytometry, wound-healing, transwell, cell counting Kit-8 (CCK-8), and EdU assay confirmed that the knockdown of LINC00665 could reduce the viability, proliferation, and migration of SKOV-3 and OVCAR-3 cells. Accumulating evidence indicates that many lncRNAs can function as endogenous miRNA sponges by competitively binding common miRNAs. In this study, the bioinformatics analysis suggests that LNC00665 specifically binds to miR-181a-5p. LINC00665 downregulated the miR-181a-5p in SKOV-3 and OVCAR-3 cells. The knockdown of miR-181a-5p evidently reverses the inhibitory effect of sh-LINC00662. Besides, FH2 domain containing 1 (FHDC1) has been proved to deed as an effective target of miR-181a-5p. The results reveal the knockdown of LINC00665 facilitates ovarian cancer via development by sponging miR-181a-5p and up-regulating FHDC1 expression. These may contribute to ovarian cancer therapy.

LINC00665 affects the malignant biological behavior of ovarian cancer via the miR-148b-3p/KLF5

This study investigated the expression and clinical significance of long intergenic noncoding RNA 00665 (LINC00665) in ovarian cancer (OC), as well as its effect on the malignant biological behavior of OC cells. The expression of LINC00665, miR-148b-3p, and Krüppel-like factor 5 (KLF5) in OC tissues and cells were determined by RT-qPCR. Western blot was used to detect the protein expression of KLF5. The expression patterns of LINC00665 in nuclear and cytoplasm fractions were undertaken using RT-qPCR. In addition, CCK-8 assay, clone formation assay, transwell, scratch test, and flow cytometry were respectively used to detect the cell activity, proliferation, invasiveness, healing of cells, and apoptosis rate of OC cells. Furthermore, the interactions between LINC00665 and miR-148b-3p and between miR-148b-3p and KLF5 were verified by the luciferase reporter assay, and the correlations among these three genes were analyzed. LINC00665 expression was upregulated both in OC cell lines and tissues. Si-LINC00665 inhibited cell proliferation, invasion, and migration and induced apoptosis to a certain extent. The subcellular fraction assay revealed LINC00665 to be located mainly in the cytoplasm. miR-148b-3p was a target of LINC00665, and KLF5 was directly targeted by miR-148b-3p. Si-LINC00665 inhibited KLF5 expression, miR-148b-3p inhibitor promoted KLF5 expression, and si-KLF5 inhibited LINC00665 expression. Interestingly, the expression of LINC00665 was reversely associated with miR-148b-3p expression but positively correlated with KLF5. Furthermore, miR-148b-3p expression was negatively correlated with KLF5. In addition, si-KLF5 inhibited the malignant biological behavior of OC cells, whereas miR-148b-3p inhibitor had the opposite effect. Most importantly, the si-LINC00665 could reverse the promotion effect of the miR-148b-3p inhibitor on the malignant biological behavior of OC cells. LINC00665 can be used as an effective prognostic indicator of OC, which has the potential to be a new therapeutic target.

Silencing LINC00665 inhibits cutaneous melanoma in vitro progression and induces apoptosis via the miR-339-3p/TUBB

Background

LncRNAs are closely related to cutaneous melanoma (CM) tumorigenesis and metastasis, and it can affect the progression of CM by regulating cell proliferation, migration, invasion, apoptosis, and other cellular mechanisms. This study investigated the role of LINC00665 in CM.

Methods

Expressions of LINC00665, miR‐339‐3p, and tubulin beta chain (TUBB) in CM cells were analyzed by qRT‐PCR and/or Western blot. The LINC00665/miR‐339‐3p/TUBB targeting network was predicted by bioinformatics tools, screened out by Venn diagrams and analyzed by Pearson's correlation coefficients, followed by validation via dual‐luciferase reporter assay and/or pull‐down assay. Transfection of siLINC00665 or miR‐339‐3p inhibitor/mimic was conducted with CM cells whose viability, proliferation, migration, invasion, cell cycle progression, and apoptosis were measured by CCK‐8 assay, colony formation assay, wound healing assay, Transwell assay, and flow cytometry. The associations of TUBB with tumor biological characteristics and other proteins were analyzed by CanserSEA and String, respectively.

Results

High‐expressed LINC00665 was detected in CM cells. Silencing LINC00665 decreased CM cell viability; inhibited colony formation, cell cycle progression, migration and invasion; enhanced apoptosis; and upregulated miR‐339‐3p. LINC00665 targeted miR‐339‐3p which targeted TUBB. MiR‐339‐3p upregulation induced effects similar to the LINC00665‐silencing‐induced effects and could downregulate TUBB, which was associated with malignant behaviors and related to other five proteins. MiR‐339‐3p downregulation induced the opposite effects of what miR‐339‐3p upregulation induced, and the miR‐339‐3p downregulation‐induced effects could be reversed by LINC00665 silencing.

Conclusion

Silencing LINC00665 inhibits in vitro CM progression and induces apoptosis via the miR‐339‐3p/TUBB axis.

LINC00665 knockdown confers sensitivity in irradiated non-small cell lung cancer cells through the miR-582-5p/UCHL3/AhR axis

Background

The resistance to radiotherapy remains a major obstacle that limits the efficacy of radiotherapy in non-small cell lung cancer (NSCLC). This study aims to illustrate the molecular mechanism underlying the role of LINC00665 in the radiosensitivity of NSCLC, which involves ubiquitin C-terminal hydrolase L3 (UCHL3).

Methods and results

The expression of UCHL3 was determined in clinical tissue samples collected from NSCLC patients and NSCLC cell lines. We found that UCHL3 overexpression occurred in both NSCLC tissues and cells, associated with poor prognosis in NSCLC patients. Mechanistically, UCHL3 stabilized aryl hydrocarbon receptor (AhR) protein through deubiquitination, thereby promoting PD-L1 expression. UCHL3 reduced the radiosensitivity of NSCLC cells by stabilizing AhR protein. Upstream microRNAs (miRNAs) and lncRNAs of UCHL3 were predicted by microarray profiling and validated by functional experiments. LINC00665 functioned as a sponge of miR-582-5p and thus up-regulated the expression of the miR-582-5p target UCHL3. Gain- and loss- of function assays were performed to assess the effects of LINC00665, UCHL3 and miR-582-5p on the in vitro cell malignant behaviors and immune escape as well as on the in vivo tumor growth. Silencing LINC00665 or overexpressing miR-582-5p enhanced the sensitivity of NSCLC cells to radiotherapy. LINC00665 augmented the immune escape of NSCLC cells in vitro and in vivo through stabilizing AhR protein via the miR-582-5p/UCHL3 axis.

Conclusions

Overall, LINC00665 reduced the radiosensitivity of NSCLC cells via stabilization of AhR through the miR-582-5p/UCHL3 axis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03516-2.

The Biological and Molecular Function of LINC00665 in Human Cancers

Long non-coding RNAs (lncRNAs) are more than 200 nucleotides in length and are implicated in the development of human cancers, without protein-coding function. Mounting evidence indicates that cancer initiation and progression are triggered by lncRNA dysregulation. Recently, a growing number of studies have found that LINC00665, a long intergenic non-protein coding RNA, may be associated with various cancers, including gastrointestinal tumors, gynecological tumors, and respiratory neoplasms. LINC00665 was reported to be significantly dysregulated in cancers and has an important clinical association. It participates in cell proliferation, migration, invasion, and apoptosis through different biological pathways. In this review, we summarize the current findings on LINC00665, including its biological roles and molecular mechanisms in various cancers. LINC00665 may be a potential prognostic biomarker and novel therapeutic target for cancers.

LINC00665 interacts with BACH1 to activate Wnt1 and mediates the M2 polarization of tumor-associated macrophages in GC

Gastric cancer (GC) remains one of the prevalent causes of cancer-related deaths globally. Long non-coding RNAs (lncRNAs) have been associated with different cancers. The polarization of macrophages towards the M2 (alternatively activated) phenotype promotes immunologic tolerance and can induce gastric tumorigenesis. Thus far, lncRNAs have been shown to modulate the differentiation of immune cells. Here, we investigated the biological effects of LINC00665 on the progression of GC and explored the mechanisms underlying its ability to mediate the polarization of macrophages towards the M2 phenotype. We report that the levels of LINC00665 were increased in GC tissues. Furthermore, this increase in LINC00665 expression could be associated with decreased overall survival (OS), progression-free survival (PFS), and post-progression survival (PPS). Using cell-based macrophage polarization models, we demonstrated that LINC00665 upregulation in GC cells facilitated the polarization of macrophages towards the M2 but not M1 (classically activated) phenotype. Furthermore, the loss of LINC00665 prevented the M2 polarization of macrophages. Mechanically, we identified that Wnt1 was the downstream target of LINC00665. Additionally, LINC00665 could directly interact with the transcription factor BTB domain and CNC homology 1 (BACH1). The interaction between LINC00665 and BACH1 resulted in the activation and binding of BACH1 to the Wnt1 promoters. Furthermore, BACH1 silencing could inhibit GC progression, which highlighted a crucial role for BACH1 in LINC00665-mediated Wnt1 activation. In addition, genetic Wnt1 overexpression effectively abolished the repression of Wnt signaling after BACH1 depletion and mediated GC development by supporting M2 macrophage polarization. In conclusion, we report that LINC00665 modulates M2 macrophage polarization and suggest that it may facilitate macrophage-dependent GC progression.

Up-regulation of LINC00665 contributes to the progression of glioma and correlates with its MRI characteristics

BACKGROUND

LncRNA LINC00665 partakes in controlling the malignant phenotype of cancer cells, but its role in glioma and the related regulatory mechanism remain uncertain.

METHODS

RT-PCR was exploited to examine LINC00665 expression. The relationships among the LINC00665 expression, the clinicopathologic values and magnetic resonance imaging (MRI) characteristics of glioma were analyzed. The multiplication, movement, and aggressiveness of glioma cell lines were evaluated by CCK-8, EdU, and Transwell experiments after constructing LINC00665 overexpression and LINC00665 knockdown cell models. A dual-luciferase reporter gene experiment and RIP experiment were executed to validate the interactions between LINC00665 and miR-129-5p, and between miR-129-5p and HMGB1. Western blot and RT-PCR were conducted to find the impact of LINC00665 and miR-129-5p on HMGB1 expression. Nude mouse model was also constructed to examine the impact of LINC00665 on multiplication and aggressiveness of glioma cells in vivo.

RESULTS

LINC00665 expression was markedly increased in glioma. High LINC00665 expression in glioma was closely linked to larger tumor diameter, higher pathologic grade, heterogeneous MRI signal of the tumor, increased peritumoral edema, and stronger MRI enhancement characteristics. LINC00665 overexpression facilitated the malignant behavior of glioma cells, while LINC00665 knockdown played the reverse role. Mechanistically, LINC00665 could decoy miR-129-5p, and indirectly increased HMGB1 expression.

CONCLUSION

LINC00665 functions as an oncogenic lncRNA in glioma, to accelerate glioma progression by modulating miR-129-5p and increasing HMGB1 expression.

Mechanism Analysis of LINC00665 and Its Peptides CIP2A-BP in Hepatocellular Carcinoma

Background: More and more studies show that long non-coding RNAs (lncRNAs) have miniature open reading frames that can be translated into short peptides. Here, we identify the long non-coding gene LINC00665 and its short peptides (CIP2A-BP) in hepatocellular carcinoma (HCC) and explore how they contribute to HCC progression. Materials and methods: First, GSE101728 data were acquired through the Gene Expression Omnibus for identification of differentially expressed genes (DEGs), and gene set enrichment analysis (GSEA) was conducted to find enriched biological pathways. Then, further bioinformatics analysis was carried out on the screened long non-coding genes, and LINC00665 expression was detected in HCC and normal liver samples. The relations between LINC00665 expression, HCC prognosis, and clinical characteristics were studied. Receiver operating characteristic (ROC) analysis was also applied to verify the LINC00665 prediction in HCC prognosis. In addition, pertinent experiments on LINC00665 and CIP2A-BP were also carried out to explore their roles in the progression of HCC. Results: As a result, we screened out 332 DEGs in total, including 130 upregulated and 202 downregulated DEGs. These DEGs were mainly enriched in posttranscriptional regulation of gene expression, RNA processing, nucleolus, and gene silencing biological pathways. In addition, we found that LINC00665 was increased in HCC samples, which substantially indicated its poor prognosis. Compared with normal tissues, LINC00665 had higher expression in the pathological stages III and IV, tumor-free groups, people no more than 60 years old, and stages T3, T4, N0, N1, and M1. ROC curve indicated that the variable INC00665 had certain accuracy in predicting overall survival (OS). Moreover, in functional experiments, LINC00665 knockdown could significantly decrease HCC cell proliferation, migration, and invasion, while overexpressed CIP2A-BP could markedly increase HCC cell proliferation, invasion, and migration. Conclusion: Our findings not only disclose a unique mechanism by which CIP2A-BP encoded by LINC00665 promotes HCC carcinogenesis but suggest that these long non-coding genes and short peptides could be used as biomarkers for HCC diagnosis and prognosis and new targets for HCC therapy.

Paeonol inhibits the malignancy of Apatinib-resistant gastric cancer cells via LINC00665/miR-665/MAPK1 axis

BACKGROUND

Paeonol is the extractive of Paeonia suffruticosa Andr and is reported to reverse the chemotherapy resistance of cancer cells. The present study explores the role of paeonol in inhibiting the malignant biological behaviors of Apatinib-resistant gastric cancer (GC) cells.

METHODS

The Traditional Chinese Medicine Systems Pharmacology (TCMSP) database was adopted to screen the target genes of paeonol, and the STRING database was employed to construct a protein-protein interaction (PPI) network. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of the target genes was performed employing DAVID online database. The expressions of these target genes in GC tissues and para-cancerous tissues were analyzed with GEPIA database, and GEO datasets (GSE109476 and GSE93415) were utilized to analyze differentially expressed lncRNAs and miRNAs in GC tissues and para-cancerous tissues. The expressions of LINC00665, miR-665 and MAPK1 mRNA in Apatinib-resistant GC cells were detected through quantitative real-time polymerase chain reaction (qRT-PCR). Cell counting kit-8 (CCK-8) assay was conducted to detect cell proliferation; Transwell assays were employed to detect cell migration and invasion, and TdT-mediated dUTP nick end labeling (TUNEL) assay was utilized to detect cell apoptosis. Dual-luciferase reporter gene assay was performed to detect the binding relationships between miR-665 and LINC00665, as well as between miR-665 and MAPK1 mRNA. The expressions of MAPK1 protein and glycolysis-associated proteins (GLUT1, LDHB and HK2) were detected by Western blot. Additionally, a tumor xenograft mice model was constructed to evaluate the effects of paeonol on lung metastasis.

RESULTS

Paeonol could inhibit the proliferation, migration, invasion and glycolysis, and promote the apoptosis of Apatinib-resistant GC cells. TCMSP database suggested that Paeonol had 17 target genes, and 17 target genes were mainly enriched in signaling pathways related to apoptosis, glucose and lipid metabolism, etc.; GEPIA database suggests that MAPK1, among the 17 target genes, was markedly elevated in GC tissues. Paeonol could decrease LINC00665 and MAPK1 expressions in GC cells but increase the expression of miR-665. LINC00665 overexpression, MAPK1 overexpression or inhibition of miR-665 could abolish the inhibitive effects of paeonol on the malignant phenotypes of Apatinib-resistant GC cells. miR-665 is verified as an upstream regulator of MAPK1 and a target of LINC00665. Additionally, paeonol could significantly inhibit the lung metastasis in the tumor xenograft mice model.

CONCLUSIONS

Paeonol can inhibit the malignancy of Apatinib-resistant GC cells through LINC00665/miR-665/MAPK1 axis. For the first time, our study imply that paeonol may be a potential drug to reverse Apatinib-resistant of GC cells.

LINC00665 up-regulates SIN3A expression to modulate the progression of colorectal cancer via sponging miR-138-5p

Background

Colorectal cancer (CRC) is a malignant tumor affecting people worldwide. Long noncoding RNAs (lncRNAs) is a crucial factor modulating various cancer progression, including CRC. Long intergenic non-protein coding RNA 665 (LINC00665) has been proven as an oncogene in several cancers, but its function in CRC is still unclear.

Methods

QRT-PCR was performed for RNA quantification. Functional assays were designed and carried to test cell phenotype while mechanism experiments were adopted for detecting the interaction of LINC00665, microRNA-138-5p (miR-138-5p) and SIN3 transcription regulator family member A (SIN3A). In vivo experiments were conducted to test LINC00665 function on modulating CRC tumor progression.

Results

LINC00665 displayed high expression in CRC tissues and cells, and promoted tumor progression in vivo. MiR-138-5p displayed abnormally low expression in CRC, and was verified to be sponged by LINC00665. Furthermore, SIN3A, as the downstream mRNA of miR-138-5p, exerted promoting impacts on CRC cells. Rescue experiments certified that overexpressed SIN3A or silenced miR-138-5p could offset the repressed function of LINC00665 knockdown on CRC progression.

Conclusions

LINC00665 could sponge miR-138-5p to up-regulate SIN3A expression, thus accelerating CRC progression.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02176-4.

LINC00665 knockdown protects against cerebral ischemia-reperfusion injury

LINC00665 has been reported to participate in several human diseases. However, the role of LINC00665 in cerebral ischemia-reperfusion (CI/R) is still unknown. This study is designed to investigate the role of LINC00665 in rats with CI/R injury. We established middle cerebral artery occlusion/ reperfusion (MCAO/R) rats model in vivo. PC12 cells treated with oxygen-glucose deprivation/reperfusion (OGD/R) were used to establish in vitro I/R model. RT-qPCR assay was adopted to assess the mRNA expression of LINC00665 and miR-744-5p. MTT assay was used to determine cell viability. The protein expression of Bax and Bcl-2 were detected by Western blot assay. The relationship between LINC00665 and miR-744-5p was confirmed by dual luciferase reporter assay and RNA immunoprecipitation (RIP). In this study, we found that LINC00665 was sharply up regulated in MCAO/R rats and PC12 cells treated with I/R. Functionally, LINC00665 knockdown attenuated oxidative damage in PC12 cells treated with I/R. Moreover, LINC00665 knockdown promoted cell viability, while inhibited cell apoptosis in PC12 cells treated with I/R. In addition, miR-744-5p was confirmed to be a target of LINC00665. LINC00665 knockdown was validated to project CI/R injury by sponging miR-744-5p expression.

Downregulation of LINC00665 suppresses the progression of lung adenocarcinoma via regulating miR-181c-5p/ZIC2 axis

Long non-coding RNA (lncRNA) LINC00665 was demonstrated to be upregulated in lung adenocarcinoma (LUAD) and target miR-181c-5p. ZIC2, which is upregulated in LUAD, serves as a putative target of miR-181c-5p. In this study, we aimed to reveal whether LINC00665 regulates miR-181c-5p/ZIC2 axis to promote LUAD progression. The results showed that LINC00665, HOXA1, ZIC2, and HOXA11 levels were increased in LUAD tissues, while miR-181c-5p level was decreased when compared to the adjacent normal tissues. High expression levels of LINC00665, ZIC2, HOXA1 and HOXA11, and low expression of miR-181c-5p were closely linked to poor prognosis of LUAD patients. Knockdown of LINC00665 induced obvious inhibitions in cell viability, clone formation, invasion and tumorigenesis in LUAD cells, whereas miR-181c-5p downregulation significantly neutralized these effects. In addition, downregulation of ZIC2 obviously reversed the enhancements of cell viability, clone formation, invasion and tumorigenesis induced by miR-181c-5p knockdown. In summary, the present study reveals that silencing of LINC00665 suppresses LUAD progression through targeting miR-181c-5p/ZIC2 axis.

The Long Noncoding RNA LINC00665 Facilitates c-Myc Transcriptional Activity via the miR-195-5p MYCBP Axis to Promote Progression of Lung Adenocarcinoma

Long noncoding RNAs (lncRNAs) have recently received growing substantial attention in cancer research due to their important roles in various cancer types. However, the underlying mechanisms and functions of lncRNAs, especially in lung adenocarcinoma (LUAD), remain elusive. Based on pan-cancer screening analyses, we identified that the noncoding RNA LINC00665 was up-regulated in lung adenocarcinoma, which was subsequently confirmed in clinical samples and cell lines. Higher expression of LINC00665 was positively associated with poor prognosis and advanced T stage. Next, using gain- and loss- of function approaches, we revealed that LINC00665 promotes cell proliferation, cell migration, invasion, and suppresses cell apoptosis in LUAD through in vitro and in vivo experiments. Additionally, our findings showed that LINC00665 was predominately localized in the cytoplasm so as to interact with Ago2 protein, which could function as miRNA sponges. The results of bioinformatics prediction and RNA pull-down assay indicated that LINC00665 directly interacted with miR-195-5p. This was also confirmed by fluorescence colocalization. Furthermore, luciferase reporter assay demonstrated that Myc binding protein (MYCBP, also called AMY-1), which enhanced c-Myc transcriptional activity, was the target gene of LINC00665 dependent on miR-195-5p. Finally, rescue functional assay results uncovered that the oncogenic capability of LINC00665 was dependent on miR-195-5p and c-Myc transcriptional activity. In summary, this work elucidates that LINC00665 accelerates LUAD progression via the miR-195-5p/MYCBP axis by acting as a competing endogenous RNA (ceRNA), suggesting that LINC00665 may represent a potential therapeutic target for clinical intervention of LUAD.

LINC00665 promotes cell proliferation, invasion, and metastasis by activating the TGF-β pathway in gastric cancer

BACKGROUND AND AIMS

Accumulating studies have demonstrated that long noncoding RNA plays a vital role in cancer progression. A previous study reported that LINC00665 was overexpressed and acted as a key tumor promoter in lung cancer, but the role of LINC00665 in gastric cancer (GC) remained uncharacterized. Thus, this study aimed to explore the mechanism of LINC00665 in GC.

METHODS

LINC00665 expression was explored using the Cancer Genome Atlas (TCGA), and a meta-analysis was conducted to assess the expression and prognostic value of LINC00665 in GC from Gene Expression Omnibus databases and the TCGA dataset. Real-time polymerase chain reaction (RT-PCR) was then conducted to verify the LINC00665 expression in GC tissues and cell lines. The effects of LINC00665 on cell proliferation, invasion, metastasis, and cell cycle in GC were evaluated using the CCK-8, wound healing, Transwell, and flow cytometry assays. In vitro validation was also performed.

RESULTS

LINC00665 overexpression was found in GC, and LINC00665 upregulation was significantly related to poor overall survival and disease-free survival. LINC00665 expression was associated with tumor depth, lymph node metastasis, and TNM stage. Univariate and multivariate analyses proved that LINC00665 could be an independent prognostic biomarker in GC. LINC00665 knockdown subsequently inhibited cell proliferation, invasion, and metastasis in GC cell lines; promoted cell apoptosis; and arrested GC cell lines in the G0/G1 phase. Western blot analysis indicated that LINC00665 silencing inhibited epithelial-mesenchymal transition and decreased the expression levels of TGF-β1, Smad2, and α-SMA.

CONCLUSION

LINC00665 can be a potential diagnostic and prognostic biomarker for GC patients, and LINC00665 promotes GC cell proliferation, invasion, and metastasis by activating the TGF-β signal pathway.

Up-Regulation of LINC00665 Facilitates the Malignant Progression of Prostate Cancer by Epigenetically Silencing KLF2 Through EZH2 and LSD1

This study aimed to explore the function of LINC00665 on the proliferation and metastasis of prostate cancer (PCa), and the potential regulatory mechanisms were also investigated. The expression level of LINC00665 in 50 pairs of PCa tissues and adjacent ones was studied by qRT-PCR, and the associations between LINC00665 and clinicopathological characteristics of PCa patients were analyzed. Control group (sh-NC) and LINC00665 knock-down group (sh-LINC00665) were set in 22RV1 and DU145 cells, respectively. The biological functions of LINC00665 in PCa cell lines were assessed by CCK-8, EdU, Transwell assays, and the nude mouse xenograft model was used to evaluate the tumorigenicity in vivo. In addition, qRT-PCR, Western Blot, RIP and ChIP assays were also used to determine the regulation mechanism of LINC00665 in PCa cell lines. In this study, our results showed that LINC00665 expression level in PCa cancer tissues was significantly up-regulated, compared with that in adjacent ones. Besides, similar results were found in PCa cell lines. Knock-down of LINC00665 significantly attenuated the proliferation and migration ability in 22RV1 and DU145 cells, compared to sh-NC. Mechanically, LINC00665 could interact with EZH2 and LSD1, recruiting them to KLF2 promoter region to inhibit its transcription. Moreover, the tumor-suppressive effects mediated by sh-LINC00665 were significantly reversed through the down-regulation of KLF2. Also, the suppression of LINC00665 impaired tumor growth of PCa in vivo. In summary, LINC00665 exerted the oncogenic functions in PCa cell lines by epigenetically silencing KLF2 expression by binding to EZH2 and LSD1, illuminating a novel mechanism of LINC00665 in the malignant progression of PCa and furnishing a prospective therapeutic biomarker to combat PCa.

LINC00665/miR-379-5p/GRP78 regulates cisplatin sensitivity in gastric cancer by modulating endoplasmic reticulum stress

Acquired resistance to cisplatin (DDP)-based chemotherapy greatly hinders the treatment of gastric cancer (GC). LINC00665 serves as an oncogene in GC. Hence, the current study was designed to investigate the regulatory effects of LINC00665 on DDP-resistance of GC. LINC00665 and miR-379-5p expression levels were detected by real-time quantitative polymerase chain reaction (RT-qPCR) and Glucose regulated protein 78 (GRP78) protein level was measured by western blot assay. Interactions between LINC00665 and miR-379-5p or between miR-379-5p and GRP78 were verified by dual luciferase reporter assay. Cell counting kit 8 (CCK-8) assay and flow cytometry assay respectively determine the proliferative ability and apoptosis of GC cells. Western blot analysis was also performed to detect the protein levels of C/EBP-homologous protein (CHOP), X box binding protein (XBP1) and apoptosis-related proteins. In addition, GRP78 expression was evaluated by immunofluorescence. It was observed that the expression levels of LINC00665 and GRP78 were upregulated, and the expression level of miR-379-5p was downregulated in DDP-sensitive and DDP-resistant GC cell lines. What's more, GRP78 expression and the cell growth inhibition rates of DDP-sensitive and DDP-resistant GC cells had a negative correlation. Additionally, miR-379-5p was a target miRNA of LINC00665, and GRP78 was a target mRNA of miR-379-5p. Functional studies revealed that knockdown of LINC00665 inhibited DDP-resistant GC cell proliferation, induced apoptosis as well as suppressed Endoplasmic reticulum (ER) stress. Mechanistically, knockdown of LINC00665 downregulated GRP78 expression by strengthening miR-379-5p. LINC00665 silencing could overcome DPP-resistance of GC cells by downregulating GRP78 via sponging miR-379-5p, indicating that LINC00665 might be a potential therapeutic target for DDP- resistant GC patients.

Long intergenic noncoding RNA 00665 promotes proliferation and inhibits apoptosis in colorectal cancer by regulating miR-126-5p

Long intergenic noncoding RNAs (lincRNAs) regulate a series of biological processes, and their anomalous expression plays critical roles in the progression of multiple malignancies, including colorectal cancer (CRC). Although many studies have reported the oncogenic function of LINC00665 in multiple cancers, few studies have explored its role in CRC. The aim of this study was to assess the effect of LINC00665 on the malignant behaviors of CRC and explore the underlying regulatory mechanism of LINC00665. LINC00665 was significantly upregulated in CRC. A loss-of-function assay revealed that LINC00665 downregulation inhibited the proliferation and promoted the apoptosis of CRC cells, which was mediated by cyclin D1, CDK4, caspase-9 and caspase-3. Through mechanistic exploration, we found that miR-126-5p directly bound to LINC00665. Moreover, LINC00665 and miR-126-5p both regulated PAK2 and FZD3 expression. Mechanistically, miR-126-5p was predicted and further verified as a target of both PAK2 and FZD3. These findings demonstrate that LINC00665 might play an important pro-proliferative and antiapoptotic role in CRC and might be a potential biomarker and a new therapeutic target for CRC.

LINC00665 activates Wnt/β-catenin signaling pathway to facilitate tumor progression of colorectal cancer via upregulating CTNNB1

Background LINC00665 is a newly identified oncogene, which has been reported to be oncogene in various cancers. Nevertheless, its role in the progression of colorectal cancer (CRC) remains obscure to the extent. This study aimed at exploring the role and mechanism of LINC00665 in CRC progression. Materials and methods RNA and protein expression were detected via qRT-PCR and western blot. Functional assays were conducted to investigate the role of LINC00665 in the CRC cellular processes. TOP/FOP assay was performed to detect the activity of Wnt/β-catenin signaling pathway. Mechanism investigations were carried out to explore the regulatory relationship among genes. Results LINC00665 was overtly expressed in CRC cell lines at high levels. Functionally, silencing of LINC00665 could curb in vitro CRC cell growth, migration and invasion, while stimulating cell apoptosis. Mechanically, LINC00665 sponged miR-214-3p to up-regulate CTNNB1 expression, consequently activating Wnt/β-catenin signaling pathway. Furthermore, LINC00665 could bind to U2AF2 and enhance the association between U2AF2 and CTNNB1, increasing the stability of CTNNB1. CTNNB1 overexpression could reverse the suppressive effects of LINC00665 downregulation. Conclusion LINC00665 stimulates CRC progression through the activation of Wnt/β-catenin signaling pathway, which hopefully might be a therapeutic target for CRC.

LINC00665 Stimulates Breast Cancer Progression via Regulating miR-551b-5p

Introduction

Long intergenic non-protein coding RNA 665 (LINC00665) has been revealed to contribute cancer progression in many cancer types including liver and gastric cancer. However, the roles of LINC00665 in breast cancer (BC) remain to be explored.

Methods

We explored LINC00665 expression in BC tissues and normal tissues at GEPIA. Then, its expression in BC cells (HCC-1937, MDA-MB-231, and MCF-7) and normal cells (MCF10A) was analyzed with qRT-PCR. In addition, the mechanisms of LINC00665 in BC were explored using bioinformatic analyses, luciferase activity reporter assay, RNA pull-down assay, and rescue experiments.

Results

We showed LINC00665 expression was significantly increased in both BC tissues and cells. The knockdown of LINC00625 significantly inhibits BC cell growth and promotes cell apoptosis in vitro, while the overexpression of LINC00625 has the opposite effects on BC progression. LINC00665 could affect BC progression via regulating miR-551b-5p.

Discussion

Taken together, our study showed that the LINC00665/miR-551b-5p axis was involved in the progression of BC.

LINC00665 functions as a competitive endogenous RNA to regulate AGTR1 expression by sponging miR‑34a‑5p in glioma

Glioma is the most aggressive tumor of the central nervous system. Long non-coding RNAs (lncRNAs) may be involved in modulating tumor generation. The present study analyzed an lncRNA microarray of glioma and selected long intergenic non-protein coding RNA 665 (LINC00665) as the research object. The mode of expression and biological function of LINC00665 in glioma were assessed using lncRNA microarray and RT-qPCR analyses. Gain-of-function assays and/or loss-of-function assays were implemented to explore the role of LINC00665 in the progression of glioma. Dual-luciferase reporter and RNA immunoprecipitation assays explored the downstream molecular mechanism of LINC00665. The function of the molecular pathway in progression of glioma was analyzed using rescue assays. High expression of LINC00665 was marked in glioma tissues and cells, which correlated with an unsatisfactory prognosis. Upregulation of LINC00665 significantly promoted the proliferation and invasion of glioma cells. LINC00665 acted as a competing endogenous RNA by sponging miR-34a-5p to upregulate angiotensin II receptor type 1 (AGTR1). LINC00665 promoted the progression of glioma by acting as a competitive endogenous RNA to competitively bind to miR-34a-5p and mediate AGTR1 expression.

LINC00665 promotes Ovarian Cancer progression through regulating the miRNA-34a-5p/E2F3 axis

Objective: To clarify the role of LINC00665 in ovarian cancer (OC) progression and the possible mechanism. Methods: LINC00665 levels in OC tissues and cell lines were detected by qRT-PCR. The correlation between LINC00665 and clinicopathologic characteristics of OC patients was assessed. Biological functions of OC cell phenotypes influenced by LINC00665 were examined by CCK-8, colony formation and Transwell assay. Dual-luciferase reporter assay and RIP assay were conducted to verify the interaction between LINC00665 and its downstream target. Results: LINC00665 was upregulated in OC and linked to poor prognosis. Knockdown of LINC00665 blocked malignant proliferative, migratory and invasive functions of OC cells. By competitively binding miRNA-34a-5p, LINC00665 abolished the inhibitory effect of miR-34a-3p on its downstream gene E2F3, thus promoting OC progression. Conclusion: LINC00665/miRNA-34a-5p/E2F3 axis is involved in OC progression, providing novel insights into the clinical treatment of OC.

NF-κB 1-induced LINC00665 regulates inflammation and apoptosis of neurons caused by spinal cord injury by targeting miR-34a-5p

Background: Spinal cord injury (SCI) has high disability rate and low cure rate, which frustrates the patients and brings a heavy burden to their families. This study aimed to explore whether NF-κB1 could induce the expression of LINC00665 and form a feedback loop with miR-34a-5p to regulate inflammation and apoptosis of neurons. Results: Basso, Beattie, and Bresnahan (BBB) scoring was decreased, damage for spinal cord tissue was aggravated and neuron number was decreased in SCI rats. The levels of TNF-α, IL-1β and IL-6 in serum and the expression of LINC00665 and NF-κB1 in spinal cord tissues were all increased in SCI rats. After LPS induction, PC12 cell viability was decreased. The expression of LINC00665 and NF-κB1 in LPS-induced PC12 cells was increased, which was partially reversed by BAY11-7082 (NF-κB inhibitor). Inhibition of LINC00665 improved cell viability, suppressed apoptosis and inflammation and down-regulated the NF-κB1 expression in LPS-induced PC12 cells. Furthermore, miR-34a-5p expression was decreased in LPS-induced PC12 cells, which could be promoted by inhibition of LINC00665. miR-34a-5p inhibitor restrained the effect of inhibition of LINC00665 on NF-κB1 expression in LPS-induced PC12 cells. Conclusion: inhibition of LINC00665 improved cell viability, suppressed apoptosis and inflammation in LPS-induced PC12 cells, and the NF-κB1/LINC00665/miR-34a-5ploop might be a useful therapeutic target in SCI treatment.

LINC00665 enhances tumorigenicity of endometrial carcinoma by interacting with high mobility group AT-hook 1

Background

Endometrial carcinoma is a frequently diagnosed cancer among females. LncRNAs are reported to be associated with various cancers. Their biological roles in endometrial carcinoma progression is an emerging scientific area. LINC00665 can exert a significant role in many cancers. However, its potential function in endometrial carcinoma is still poorly known.

Method

qRT-PCR was carried out to test expression of LINC00665 and HMGA1. Western blot analysis was carried out to detect protein expression of HMGA1. Cell proliferation was evaluated using Cell Counting Kit-8 (CCK-8) and EdU assay. Flow cytometry assay was used to determine cell apoptosis and cell cycle. Wound healing and transwell invasion assay was carried out to test cell migration and invasion. Immunohistochemical staining and HE staining were conducted to assess Ki-67 and tumor growth respectively.

Results

Expression of LINC00665 in clinical endometrial carcinoma tissues and cells was obviously up-regulated. Loss of LINC00665 could repress endometrial carcinoma cell viability, induce cell apoptosis and block cell cycle in G1 phase. KLE and HHUA cell migration and invasion ability were depressed by LINC00665 shRNA. Decrease of LINC00665 suppressed endometrial carcinoma tumorigenicity in vivo. RIP assay proved that LINC00665 directly bound with HMGA1 protein. shRNA of HMGA1 obviously restrained endometrial carcinoma cell growth and cell invasion.

Conclusions

LINC00665 might promote endometrial carcinoma progression by positively modulating HMGA1.

Long non-coding RNA LINC00665 promotes melanoma cell growth and migration via regulating the miR-224-5p/VMA21 axis

Melanoma is an aggressive malignant skin tumor endangering the health of patients. Long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) have been increasingly reported to be implicated in the carcinogenesis of melanoma. Long intergenic non-coding RNA 00665 (LINC00665) has been found to exert important regulatory roles in some cancers, yet its function in melanoma remains to be investigated. QRT-PCR analysis was conducted to evaluate the relative expression of RNAs. Functional experiments in vitro including colony formation, EdU, wound-healing and transwell assays, as well as in vivo xenograft assays, were utilized to study the role of LINC00665 in melanoma. Mechanical experiments were implemented to probe into the molecular linkage of LINC00665, miR-224-5p and VMA21. LINC00665 was abnormally highly expressed in melanoma cells. Silencing LINC00665 could inhibit the proliferation and migration of melanoma cells. LINC00665 sponged miR-224-5p to upregulate VMA21. VMA21 knockdown exerted similarly interfering effects on above biological processes in melanoma cells. However, VMA21 overexpression abolished the in vitro and in vivo outcomes of LINC00665 silencing. LINC00665 promotes proliferative and migrating abilities of melanoma cells via targeting miR-224-5p/VMA21 axis.

Knockdown of LINC00665 inhibits proliferation and invasion of breast cancer via competitive binding of miR-3619-5p and inhibition of catenin beta 1

Background

Long intergenic non-protein coding RNA00665 (LINC00665) plays a crucial tumorigenic role in many cancers, such as gastric cancer and lung adenocarcinoma. However, its role and mechanism of action in the progression of breast cancer (BC) are unknown.

Methods

LINC00665 expression levels were determined using quantitative polymerase chain reaction analysis with BC tissues and cell lines. BC cell proliferation was tested by performing 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays, whereas BC cell migration and invasion capabilities were analyzed by performing transwell migration assays. Percentages of apoptotic cells were measured by flow cytometry. Interactions between LINC00665 and miR-3169-5p were examined by performing luciferase reporter assays, and the expression levels of proteins, such as β-catenin, were examined by western blot analysis.

Results

LINC00665 was expressed at high levels in BC tissues and cells. Upregulated LINC00665 expression correlated with tumor size and tumor, node, and metastasis stages, but not with the age of patients. LINC00665 knockdown inhibited BC cell proliferation, migration, and invasion, whereas it promoted apoptosis. Moreover, bioinformatics analysis and the luciferase reporter assay revealed that LINC00665 bound the microRNA (miR) miR-3619-5p. miR-3619-5p expression correlated negatively with LINC00665 expression in BC tissues. miR-3619-5p overexpression inhibited BC cell proliferation, migration, and invasion, but promoted apoptosis. Simultaneous knockdown of LINC00665 and miR-3619-5p led to increased cell proliferation, migration, and invasion, and inhibited apoptosis. Additionally, catenin beta 1, which encodes the β-catenin protein, was the target gene of miR-3619-5p. β-catenin expression clearly decreased after LINC00665 knockdown and miR-3619-5p overexpression, but increased after simultaneous knockdown of LINC00665 and miR-3619-5p.

Conclusion

LINC00665 knockdown inhibited BC cell proliferation and invasion by binding miR-3619-5p and inhibiting β-catenin expression.

LINC00665/miR-9-5p/ATF1 is a novel axis involved in the progression of colorectal cancer

Long noncoding RNAs (lncRNAs) are abnormally expressed in many malignant tumors and involved in regulating the malignant phenotypes of cancer cells. However, the role of LINC00665 in colorectal cancer (CRC) and its regulatory mechanism remain unclear. In this study, real-time polymerase chain reaction (RT-PCR) was used to detect the expressions of LINC00665, miR-9-5p and activating transcription factor 1 (ATF1) mRNA in CRC tissues. The expression of ATF1 in CRC tissues was also detected by immunohistochemistry and Western blot. CCK-8 and colony formation assays were employed to detect cell proliferation. Cell cycle and apoptosis were detected by flow cytometry analysis. Scratch healing assay and Transwell test were exploited to detect cell migration and invasion. The targeting relationships between LINC00665 and miR-9-5p, and miR-9-5p and ATF1 were validated by dual luciferase reporter assay. We found that LINC00665 was significantly overexpressed in CRC tissues, and it was also negatively correlated with the expression of miR-9-5p and positively associated with the expression of ATF1. Besides, LINC00665 promoted the proliferation, migration and invasion of CRC cells, and inhibited cell apoptosis by sponging miR-9-5p. ATF1 was proved to be the downstream target of miR-9-5p and was indirectly regulated by LINC00665. Collectively, it is concluded that LINC00665 contributes to the progression of CRC by regulating miR-9-5p/ATF1 axis.

LINC00665 Promotes the Progression of Multiple Myeloma by Adsorbing miR-214-3p and Positively Regulating the Expression of PSMD10 and ASF1B

Background

Although assertion that long non-coding RNA (lncRNA) exerts crucial functions in the progression of multiple myeloma (MM) is well documented, few studies investigate function and underlying mechanism of long intergenic non-protein coding RNA 665 (LINC00665) in MM.

Patients and Methods

A total of 25 MM patient samples and 15 healthy volunteer samples were collected, and quantitative real-time polymerase chain reaction (qRT-PCR) was employed to detect the expressions of LINC00665. PSMD10 and ASF1B expressions were determined by qRT-PCR and Western blot assays. U266 cell and H929 cell were used in functional experiments. Besides, CCK-8 assay and flow cytometry analysis were utilized to determine cell proliferation and apoptosis. Bioinformatics analysis and dual-luciferase reporter assays were used to predict and verify the targeting relationships between LINC00665 and miR-214-3p, PSMD10 and miR-214-3p, as well as ASF1B and miR-214-3p. Moreover, the regulatory function of LINC00665 on the expression of PSMD10 and ASF1B was detected by Western blot.

Results

The expression of LINC00665 was up-regulated in MM samples and cell lines. In vitro functional assays indicated that LINC00665 enhanced MM cell proliferation and inhibited its apoptosis. PSMD10 and ASF1B were identified as target genes of miR-214-3p. Additionally, LINC00665 negatively regulated miR-214-3p expression through sponging miR-214-3p and positively regulated PSMD10 and ASF1B.

Conclusion

LINC00665 can promote the expression of PSMD10 and ASF1B by inhibiting the expression of miR-214-3p, thus facilitating the proliferation and inhibiting apoptosis of MM cells.

Downregulation of LINC00665 confers decreased cell proliferation and invasion via the miR-138-5p/E2F3 signaling pathway in NSCLC

Non-small cell lung cancer (NSCLC) is a type of malignant tumor which threatens human health and life. Recently, some researches on long non-coding RNAs (lncRNAs) in NSCLC has elucidated critical regulatory roles in cell proliferation, migration, and invasion, the relative clinical significance and mechanisms of action are still unclear. This study focuses on the important role of a novel lncRNA LINC00665 in the development of NSCLC. Long intergenic non-protein coding RNA 665 gene (LINC00665) was found through microarray analysis and was measured by real-time quantitative PCR (RT-qPCR). The interactions between LINC00665 and miR-138-5p as well as the interactions between miR-138-5p and E2F3 (E2F transcription factor 3) were explored by bioinformatics analysis and dual-luciferase assays. CCK-8, transwell and mouse xenograft assays were performed to investigate the effects of LINC00665 and miR-138-5p on NSCLC proliferation and invasion. As a result, LINC00665 expression was upregulated in NSCLC lung tissues and cells. Downregulated LINC00665 could arrest A549 and H1299 cell proliferation and invasion in vitro, and this finding was recapitulated in vivo. LINC00665 directly regulated the expression of miR-138-5p. Additionally, E2F3 was one of the targets of miR-138-5p; E2F3 without 3'UTR could reverse the inhibitory effects of downregulated LINC00665 on proliferation and invasion in A549 and H1299 cells. In conclusion, dysregulation of LINC00665 plays a vital role in NSCLC progression, indicating that its downregulation may confer decreased cell proliferation and invasion via the miR-138-5p/E2F3 signaling pathway.

lncRNA LINC00665 Stabilized by TAF15 Impeded the Malignant Biological Behaviors of Glioma Cells via STAU1-Mediated mRNA Degradation

Glioma is a brain cancer characterized by strong invasiveness with limited treatment options and poor prognosis. Recently, dysregulation of long non-coding RNAs (lncRNAs) has emerged as an important component in cellular processes and tumorigenesis. In this study, we demonstrated that TATA-box binding protein associated factor 15 (TAF15) and long intergenic non-protein coding RNA 665 (LINC00665) were both downregulated in glioma tissues and cells. TAF15 overexpression enhanced the stability of LINC00665, inhibiting malignant biological behaviors of glioma cells. Both metal regulatory transcription factor 1 (MTF1) and YY2 transcription factor (YY2) showed high expression levels in glioma tissues and cells, and their knockdown inhibited malignant progression. Mechanistically, overexpression of LINC00665 was confirmed to destabilize MTF1 and YY2 mRNA by interacting with STAU1, and knockdown of STAU1 could rescue the MTF1 and YY2 mRNA degradation caused by LINC00665 overexpression. G₂ and S-phase expressed 1 (GTSE1) was identified as an oncogene in glioma, and knockdown of MTF1 or YY2 decreased the mRNA and protein expression levels of GTSE1 through direct binding to the GTSE1 promoter region. Our study highlights a key role of the TAF15/LINC00665/MTF1(YY2)/GTSE1 axis in modulating the malignant biological behaviors of glioma cells, suggesting novel mechanisms by which lncRNAs affect STAU1-mediated mRNA stability, which can inform new molecular therapies for glioma.

LncRNA LINC00665 Promotes Prostate Cancer Progression via miR-1224-5p/SND1 Axis

Background

Increasing researches have revealed a critical role of long noncoding RNAs (lncRNAs) in tumor progression. LINC00665 is a poorly investigated lncRNA. In this research, we sought to determine the potential role of LINC00665 in prostate cancer (PC) progression.

Methods

LINC00665 expression was analyzed by bioinformatics method and qRT-PCR. Proliferation was determined via CCK8 and colony formation assays. Transwell assay was conducted to analyze migration and invasion. Xenograft assay was used to test the roles of LINC00665 in vivo. Luciferase reporter assay, pulldown assay and RIP assay were utilized to confirm the interaction between LINC00665 and miR-1224-5p.

Results

LINC00665 expression was increased in PC samples in contrast to control tissues, according to bioinformatics analysis and qRT-PCR validation. LINC00665 high expression was related to a poor prognosis. LINC00665 knockdown markedly attenuated growth and metastasis of PC cells and impaired tumor propagation in vivo. Mechanistic investigation revealed that LINC00665 was the sponge for miR-1224-5p. By inhibiting miR-1224-5p level, LINC00665 dramatically promoted the expression of SND1 in PC cells. Ectopic expression of SND1 significantly rescued the effects of LINC00665 silencing.

Conclusion

LINC00665 is a novel oncogenic gene in PC by targeting miR-1224-5p/SND1 pathway and may be a therapeutic target.

Long Intergenic Non-Protein Coding RNA 665 Regulates Viability, Apoptosis, and Autophagy via the MiR-186-5p/MAP4K3 Axis in Hepatocellular Carcinoma

PURPOSE

Long intergenic non-protein coding RNA 665 (LINC00665) plays a vital role in the development of cancer. Its function in hepatocellular carcinoma (HCC), however, remains largely unknown.

MATERIALS AND METHODS

The expressions of LINC00665, miR-186-5p, and MAP4K3 were determined by qRT-PCR. Cell viability and apoptosis were evaluated by MTT and flow cytometry, respectively. Autophagic puncta formation was observed by fluorescence microscopy. Bioinformatics analysis, luciferase reporter assay, RNA immunoprecipitation, and RNA pulldown were performed to identify associations among LINC00665, miR-186-5p, and MAP4K3. Western blot was utilized to examine the expressions of MAP4K3, Beclin-1, and LC3. Tumor growth was evaluated in a xenograft model.

RESULTS

Elevations in LINC00665 were observed in HCC tissues and cells. The overall survival of HCC patients with high levels of LINC00665 was shorter than those with low levels. In vitro, LINC00665 depletion inhibited viability and induced apoptosis and autophagy. miR-186-5p interacted with LINC00665 and was downregulated in HCC tissues and cells. Upregulation of miR-186-5p inhibited viability and induced apoptosis and autophagy, which were attenuated by upregulation of LINC00665. MAP4K3 was found to possess binding sites with miR-186-5p and was upregulated in HCC tissues and cells. MAP4K3 depletion inhibited viability and induced apoptosis and autophagy, which were attenuated by miR-186-5p inhibitor. In vivo, miR-186-5p expression was negatively correlated with LINC00665 or MAP4K3 in HCC tissues, while LINC00665 was positively correlated with MAP4K3. LINC00665 knockdown suppressed tumor growth.

CONCLUSION

LINC00665 was involved in cell viability, apoptosis, and autophagy in HCC via miR-186-5p/MAP4K3 axis, which may provide a new approach for HCC treatment.

Long non-coding RNA LINC00665 gastric cancer tumorigenesis by regulation miR-149-3p/RNF2 axis

Background

Recently, LINC00665 has been reported to be a pivotal regulator in kinds of malignancy, such as lung cancer and liver cancer. However, the functions and underlying mechanisms of LINC00665 in gastric cancer (GC) remain unclear.

Materials and methods

We recruited 49 paired GC tissue to explore LINC00665 expression by qRT-PCR. In vitro function assays were used to explore the roles of LINC00665 in GC progression. Moreover, the interaction among LINC00665, miR-149-3p and RNF2 was explored by bioinformatics analysis and luciferase reporter assay.

Results

In the present study, we found that LINC00665 expression was significantly elevated in GC tissues and cell lines. High LINC00665 expression was associated with TNM stage, histological grade, and poor prognosis of GC patients. Function assays showed that LINC00665 suppression significantly reduced GC cells viability and invasion ability in vitro. Mechanistic analysis showed that LINC00665 might serve as a ceRNA for miR-149-3p to regulate the expression of RNF2.

Conclusion

Our current study revealed the LINC00665/miR-149-3p/RNF2 axis was involved in GC progression, providing novel insights into the treatment for GC.

LINC00665 Induces Acquired Resistance to Gefitinib through Recruiting EZH2 and Activating PI3K/AKT Pathway in NSCLC

Gefitinib, a tyrosine kinase inhibitor of epidermal growth factor receptor, has been used as the first choice of treatment for advanced non-small-cell lung cancer. However, during the course of treatment, cancer cells often develop resistance to gefitinib without fully understood mechanisms. In this study, we aimed to elucidate an important role of long intergenic non-coding RNA 00665 in developing resistance to gefitinib in non-small-cell lung cancer. We showed that long intergenic non-coding RNA 00665 expression was significantly upregulated in lung cancer tissues and cells with acquired gefitinib resistance. Long intergenic non-coding RNA 00665 knockdown restored gefitinib sensitivity both in vitro and in vivo by suppressing cell proliferation and inducing apoptosis. Moreover, knockdown of long intergenic non-coding RNA 00665 markedly reduced activation of EGFR and its downstream event protein kinase B (AKT). Moreover, LINC00665 could interact with EZH2 and regulate the phosphatidylinositol 3-kinase (PI3K)/AKT pathway. Thus, our study suggests that long intergenic non-coding RNA 00665 is important for non-small-cell lung cancer to develop drug resistance and might be a potential biomarker for drug resistance and a therapeutic target for non-small-cell lung cancer.