Long non‑coding RNAs in lung cancer: Regulation patterns, biologic function and diagnosis implications (Review)

Evaluating the expression pattern of ATXN1 and CDC42EP1 genes and related long noncoding RNAs in oral squamous cell carcinoma

BACKGROUND

Oral squamous cell carcinoma (OSCC) is a significant health issue worldwide, and the expression of long non-coding RNAs (lncRNAs) are altered in these malignancies. The present study evaluated the expression level of ATXN1 CDC42EP1 genes and the lncRNAs related to these genes (lnc-ATXN1L, lnc-ATXN1, lnc-ATXN10, and lnc-CDC42EP1) in paraffin blocks of oral and pharyngeal squamous cell carcinoma (SCC) samples from patients referred to Amir Alam Hospital in Tehran, Iran.

METHODS AND RESULTS

This cross-sectional study was conducted on 76 paraffin blocks of oral and pharyngeal squamous cell carcinoma (SCC) samples from patients referred to Amir Alam Hospital in Tehran. The expression levels of ATXN1, CDC42EP1, lnc-ATXN1L, lnc-ATXN1, lnc-ATXN10, and lnc-CDC42EP1 were measured in all samples using a qPCR Master Mix kit. Real-time PCR was used to perform the reactions, and GAPDH was considered the housekeeping gene. Statistical analyses were conducted utilizing the Statistical Package for the Social Sciences (SPSS) version 22.0. The expression of lnc-ATXN1, lnc-ATXN10, and lnc-CDC42EP1 significantly differed between the two groups. All of them were downregulated (p < 0.05), and no significant difference was observed between the SCC samples and the adjacent tissue in other genes (p > 0.05). The expression of genes was not related to age, sex, size, and tumor location (p > 0.05).

CONCLUSIONS

Dysexpression of lnc-ATXN1, lnc-ATXN10, and lnc-CDC42EP1 can be used for diagnosing OSCC.

The roles of long non-coding RNAs in lung cancer

Lung cancer is the most common malignancy, being a serious threat of human lives. The incidence and mortality of lung cancer has been increasing rapidly in the past decades. Although the development of new therapeutic modes, such as target therapy, the overall survival rate of lung cancer remains low. It is urgent to advance the understanding of molecular oncology and find novel biomarkers and targets for the early diagnosis, treatment, and prognostic prediction of lung cancer. Long non-coding RNAs (lncRNAs) are non-protein coding RNA transcripts that are more than 200 nucleotides in length. LncRNAs exert diverse biological functions by regulating gene expressions at transcriptional, translational, and post-translational levels. In the past decade, it has been shown that lncRNAs are extensively involved in the pathogenesis of various diseases, including lung cancer. In this review, we highlighted the lncRNAs characterized in lung cancer and discussed their translational potential in lung cancer clinics.

Circular RNA FLNA acts as a sponge of miR-486-3p in promoting lung cancer progression via regulating XRCC1 and CYP1A1

Significantly high-expressed circFLNA has been found in various cancer cell lines, but not in lung cancer. Therefore, this study aimed to explore the role of circFLNA in the progression of lung cancer. The target gene of circFLNA was determined by bioinformatics and luciferase reporter assay. Viability, proliferation, migration, and invasion of the transfected cells were detected by CCK-8, colony formation, wound-healing, and transwell assays, respectively. A mouse subcutaneous xenotransplanted tumor model was established, and the expressions of circFLNA, miR-486-3p, XRCC1, CYP1A1, and related genes in the cancer cells and tissues were detected by RT-qPCR, Western blot, or immunohistochemistry. The current study found that miR-486-3p was low-expressed in lung cancer. MiR-486-3p, which has been found to target XRCC1 and CYP1A1, was regulated by circFLNA. CircFLNA was located in the cytoplasm and had a high expression in lung cancer cells. Cancer cell viability, proliferation, migration, and invasion were promoted by overexpressed circFLNA, XRCC1, and CYP1A1 but inhibited by miR-486-3p mimic and circFLNA knockdown. The weight of the xenotransplanted tumor was increased by circFLNA overexpression yet reduced by miR-486-3p mimic. Furthermore, miR-486-3p mimic reversed the effect of circFLNA overexpression on promoting lung cancer cells and tumors and regulating the expressions of miR-486-3p, XRCC1, CYP1A1, and metastasis/apoptosis/proliferation-related factors. However, overexpressed XRCC1 and CYP1A1 reversed the inhibitory effect of miR-486-3p mimic on cancer cells and tumors. In conclusion, circFLNA acted as a sponge of miR-486-3p to promote the proliferation, migration, and invasion of lung cancer cells in vitro and in vivo by regulating XRCC1 and CYP1A1.

ETV5-mediated upregulation of lncRNA CTBP1-DT as a ceRNA facilitates HGSOC progression by regulating miR-188-5p/MAP3K3 axis

High-grade serous ovarian cancer (HGSOC) is a common and lethal cancer of the female reproductive system. Long non-coding RNAs (lncRNAs) are aberrantly expressed in various cancers and play crucial roles in tumour progression. However, their function and molecular mechanism in HGSOC remain largely unknown. Based on public databases and bioinformatics analyses, the overexpression of lncRNA CTBP1-DT in HGSOC tissues was detected and validated in a cohort of HGSOC tissues. High expression of lncRNA CTBP1-DT was associated with poor prognosis and was an independent risk factor for survival. Overexpression of lncRNA CTBP1-DT promoted malignant biological behaviour of HGSOC cells, whereas its depletion induced growth arrest of HGSOC cells by vitro and in vivo assays. Mechanistically, lncRNA CTBP1-DT could competitively bind to miR-188-5p to protect MAP3K3 from degradation. Moreover, our results revealed that ETV5 could specifically interact with the promoter of lncRNA CTBP1-DT and activate its transcription. Collectively, these results reveal a novel ETV5/lncRNA CTBP1-DT/miR-188-5p/MAP3K3 pathway for HGSOC progression and suggest that lncRNA CTBP1-DT might be a potential biomarker and therapeutic target for HGSOC.

DLX6-AS1 activated by H3K4me1 enhanced secondary cisplatin resistance of lung squamous cell carcinoma through modulating miR-181a-5p/miR-382-5p/CELF1 axis

Cisplatin (CDDP) based chemotherapy is widely used as the first-line strategy in treating non-small cell lung cancer (NSCLC), especially lung squamous cell carcinoma (LUSC). However, secondary cisplatin resistance majorly undermines the cisplatin efficacy leading to a worse prognosis. In this respect, we have identified the role of the DLX6-AS1/miR-181a-5p/miR-382-5p/CELF1 axis in regulating cisplatin resistance of LUSC. qRT-PCR and Western blot analysis were applied to detect gene expression. Transwell assay was used to evaluate the migration and invasion ability of LUSC cells. CCK-8 assay was used to investigate the IC50 of LUSC cells. Flow cytometry was used to test cell apoptosis rate. RNA pull-down and Dual luciferase reporter gene assay were performed to evaluate the crosstalk. DLX6-AS1 was aberrantly high expressed in LUSC tissues and cell lines, and negatively correlated with miR-181a-5p and miR-382-5p expression. DLX6-AS1 expression was enhanced by H3K4me1 in cisplatin resistant LUSC cells. Besides, DLX6-AS1 knockdown led to impaired IC50 of cisplatin resistant LUSC cells. Furthermore, DLX6-AS1 interacted with miR-181a-5p and miR-382-5p to regulate CELF1 expression and thereby mediated the cisplatin sensitivity of cisplatin resistant LUSC cells. DLX6-AS1 induced by H3K4me1 played an important role in promoting secondary cisplatin resistance of LUSC through regulating the miR-181a-5p/miR-382-5p/CELF1 axis. Therefore, targeting DLX6-AS1 might be a novel way of reversing secondary cisplatin resistance in LUSC.

GAS6-AS1 Overexpression Increases GIMAP6 Expression and Inhibits Lung Adenocarcinoma Progression by Sponging miR-24-3p

GAS6 antisense RNA 1 (GAS6-AS1) is a long non-coding RNA involved in hepatocellular carcinoma and gastric cancer. However, the functional role of GAS6-AS1 in lung adenocarcinoma (LUAD) remains unclear. In the present study, qRT-PCR was used to measure the levels of GAS6-AS1, GIMAP6 and miR-24-3p expression in LUAD samples and cell lines. CCK-8 and colony formation assays were used to determine cell proliferation. Cell migration and invasion were evaluated using wound healing and transwell assays, respectively. The potential interactions between molecules were assessed using RNA immunoprecipitation and luciferase reporter assays. Western blot analysis was used to quantify protein expression. The anti-tumor effect of over-expressed GAS6-AS1 on LUAD was also examined in vivo in xenograft tumor experiments. The expression of GAS6-AS1 was notably downregulated in LUAD samples and cell lines and associated with a poor prognosis. GAS6-AS1 overexpression inhibited the migration and invasion of A549 and H1650 cells. Down-expressed GAS6-AS1 acted as a sponge for miR-24-3p and down-regulated the expression of its target, GTPase IMAP Family Member 6. These findings suggested that GAS6-AS1 might represent a potential diagnostic biomarker for LUAD.

Four long noncoding RNAs act as biomarkers in lung adenocarcinoma

Introduction

Lung adenocarcinoma (LUAD) is currently one of the most common malignant tumors worldwide. However, there is a lack of long noncoding RNA (lncRNA)-based effective markers for predicting the prognosis of LUAD patients. We identified four lncRNAs that can effectively predict the prognosis of LUAD patients.

Methods

We used data gene expression profile for 446 patients from The Cancer Genome Atlas database. The patients were randomly divided into a training set and a test set. Significant lncRNAs were identified by univariate regression. Then, multivariate regression was used to identify lncRNAs significantly associated with the survival rate. We constructed four-lncRNA risk formulas for LUAD patients and divided patients into high-risk and low-risk groups. Identified lncRNAs subsequently verified in the test set, and the clinical independence of the lncRNA model was evaluated by stratified analysis. Then mutated genes were identified in the high-risk and low-risk groups. Enrichment analysis was used to determine the relationships between lncRNAs and co-expressed genes. Finally, the accuracy of the model was verified using external database.

Results

A four-lncRNA signature (AC018629.1, AC122134.1, AC119424.1, and AL138789.1) has been verified in the training and test sets to be significantly associated with the overall survival of LUAD patients.

Conclusions

The present study demonstrated that identified four-lncRNA signature can be used as an independent prognostic biomarker for the prediction of survival of LUAD patients.

LncRNA SNHG6 promotes breast cancer progression and epithelial-mesenchymal transition via miR-543/LAMC1 axis

PURPOSE

Breast cancer (BC) is the most prevalent cancer in women with an estimated incidence of 10% and the leading cause of mortality due to its heterogenous property and high metastasis rate. Development of novel therapy is very necessary and requires an understanding of molecular mechanisms. We investigated the function of SNHG6/miR-543/LAMC1 axis in BC.

METHODS

Human BC tissues were obtained from diagnosed patients. BC cell lines and normal breast cells were used. QRT-PCR and Western blotting were employed to measure expression levels of SNHG6, miR-543, LAMC1, EMT-related proteins, and PI3K/AKT pathway. Dual-luciferase assay was performed to validate interactions of SNHG6/miR-543 and miR-543/LAMC1. Colony formation assay, flow cytometry, scratch wound healing assay, and transwell assay were utilized to assess the proliferation, apoptosis, migration, and invasion of BC cells. Nude mouse xenograft model was used the evaluate the function of SNHG6/miR-543 in tumor growth in vivo.

RESULTS

SNHG6 and LAMC1 were elevated, but miR-543 was reduced in BC tissues and cells. SNHG6 interacted directly with miR-543, while miR-543 targeted LAMC1. Knockdown of SNHG6 suppressed BC cell proliferation, migration, invasion, EMT, and PI3K/AKT pathway, but promoted cell apoptosis, while miR-543 inhibitor or overexpression of LAMC1 reversed those effects. Overexpression of LAMC1 also blocked the effects of miR-543 on BC cell proliferation, migration, invasion, and EMT. Knockdown of SNHG6 restrained BC growth in vivo, while miR-543 inhibitor inhibited that suppression.

CONCLUSION

SNHG6 promoted EMT and BC cell proliferation and migration by acting as a miR-543 sponge and disinhibiting LAMC1/PI3K/AKT pathway. SNHG6/miR-543/LAMC1 axis could serve as candidates for the development of therapeutic strategies for BC.

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

Background

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

Materials and Methods

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

Results

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

Conclusion

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

The diagnostic role of microRNA 21 in patients with nonsmall cell lung cancer: An exploratory study

Background:

Although histopathological examination of the biopsy specimen is the gold standard for the diagnosis of non small cell lung cancer (NSCLC), a blood-based noninvasive test (liquid biopsy) may prove to be helpful in patients with repeatedly negative biopsy or for response assessment following neoadjuvant therapy. The present study was conducted to explore the diagnostic value of circulating serum microRNA (miRNA) 21 in patients with NSCLC.

Methods:

This case–control analytical study was carried out in a tertiary care teaching hospital in Northern India. The study consisted of 30 cases of biopsy-proven NSCLC and 30 controls. Serum miRNA-21 expression levels were estimated by extracting total RNA from the serum sample, reverse transcribing it to cDNA and quantified in relation to U6 reference miRNA.

Results:

A total of 30 patients with NSCLC and 30 controls were included in the study. The subjects were comparable in two groups with reference to age, gender, and smoking. Pathological types were adenocarcinoma in 19 (63.3%) and squamous cell carcinoma in 11 (36.6%) patients. Majority of the patients had advanced disease-AJCC stage III in 15 patients and AJCC Stage IV in 13 patients; two patients had stage II disease. There was a significant upregulation of serum miRNA 21 gene expression in the patients with lung cancer compared to controls (median fold change, 3.39 vs. −2.81, P = 0.00). A fourfold change in serum miRNA 21 is significantly associated with the diagnosis of NSCLC with a high specificity of 97% and area under curve of 0.84 (95% confidence interval of 0.74–0.94).

Conclusion:

Estimation of serum miRNA 21 expression has potential to be used as liquid biopsy for the diagnosis of NSCLC. Further studies with large sample sizes are warranted to confirm the diagnostic accuracy of serum miRNA 21 expression.

Construction and investigation of a combined hypoxia and stemness index lncRNA-associated ceRNA regulatory network in lung adenocarcinoma

Hypoxia and stemness are important factors in tumor progression. We aimed to explore the ncRNA classifier associated with hypoxia and stemness in lung adenocarcinoma (LUAD). We found that the prognosis of LUAD patients with high hypoxia and stemness index was worse than that of patients with low hypoxia and stemness index. RNA expression profiles of these two clusters were analyzed, and 6867 differentially expressed (DE) mRNAs were screened. Functional analysis showed that DE mRNAs were associated with cell cycle and DNA replication. Protein–protein interaction network analysis revealed 20 hub genes, among which CENPF, BUB1, BUB1B, KIF23 and TTK had significant influence on prognosis. In addition, 807 DE lncRNAs and 243 DE miRNAs were identified. CeRNA network analysis indicated that AC079160.1-miR-539-5p-CENPF may be an important regulatory axis that potentially regulates the progression of LUAD. The expression of AC079160.1 and CENPF were positively correlated with hypoxia and stemness index, while miR-539-5p expression level was negatively correlated with hypoxia and stemness index. Overall, we identified CENPF, BUB1, BUB1B, KIF23 and TTK as potentially key genes involved in regulating hypoxia-induced tumor cell stemness, and found that AC079160.1-miR-539-5p-CENPF axis may be involved in regulating hypoxia induced tumor cell stemness in LUAD.

Long noncoding RNA MAFG-AS1 facilitates bladder cancer tumorigenesis via regulation of miR-143-3p/SERPINE1 axis

Background

Numerous studies have shown that long noncoding RNAs (lncRNAs) act as key regulators of bladder cancer progression. While lncRNA MAFG-AS1 has been confirmed as an oncogenic molecule in various cancers and tumorigenesis, in present study, we investigated its function and role in the tumorigenesis of bladder cancer.

Methods

The expression of MAFG-AS1, miR-143-3p and SERPINE1 in bladder cancer tissues was detected by qRT-PCR methods. The relationship between MAFG-AS1 expression and clinicopathologic characteristics of bladder cancer was analyzed. The effects of MAFG-AS1 depletion on cell proliferation, migration, invasion and apoptosis were investigated. The binding relationship of MAFG-AS1, miR-143-3p and SERPINE1 was examined by luciferase reporter analysis and RNA immunoprecipitation (RIP) assay.

Results

MAFG-AS1 was upregulated in bladder cancer tissues and cell lines. High MAFG-AS1 expression was associated with bladder cancer histological grade, TNM stage and lymph node metastasis, and patients with high expression showed poor overall survival. Cell function experiments showed that MAFG-AS1 silencing markedly suppressed bladder cancer cell proliferation, migration, invasion and increased cell apoptosis. Moreover, our results demonstrated that MAFG-AS1 functioned as a competing endogenous RNA for miR-143-3p to modulate SERPINE1 levels. Further analysis showed that miR-143-3p inhibition or SERPINE1 overexpression alleviated the suppressive effects of MAFG-AS1 silencing on malignant features.

Conclusions

Our findings indicated that MAFG-AS1 facilitates tumorigenesis via regulation of the miR-143-3p/SERPINE1 axis and also provides a novel insight into tumorigenesis and identify a promising therapeutic target for bladder cancer.

Long non-coding RNA CTBP1-AS2 enhances cervical cancer progression via up-regulation of ZNF217 through sponging miR-3163

Background

Long non-coding RNAs (lncRNAs) play significant roles in tumorigenesis and can contribute to identification of novel therapeutic targets for cancers. This paper was aimed at exploring the role of CTBP1 divergent transcript (CTBP1-AS2) in cervical cancer (CC) progression.

Methods

qRT-PCR and western blot assays were used to detect relevant RNA and protein expressions. In vitro functional assays, including CCK8, EdU, TUNEL and transwell assays were applied to explore the functions of CTBP1-AS2 in CC cell proliferation, apoptosis and migration. In vivo animal study was utilized to investigate the role of CTBP1-AS2 in tumor growth. Luciferase reporter, RNA pull down and RIP assays were performed to determine the specific mechanical relationship between CTBP1-AS2, miR-3163 and ZNF217.

Results

CTBP1-AS2 was significantly overexpressed in CC cell lines. Knockdown of CTBP1-AS2 curbed cell proliferation, migration and invasion, while stimulated cell apoptosis in vitro. CTBP1-AS2 facilitated xenograft tumor growth in vivo. Cytoplasmic CTBP1-AS2 was found to be a miR-3163 sponge in CC cells. MiR-3163 inhibition abolished the anti-tumor effects of CTBP1-AS2 knockdown. Additionally, Zinc finger protein 217 (ZNF217) was identified as a direct target of miR-3163. CTBP1-AS2 acted as a miR-3163 sponge to elevate ZNF217 expression. ZNF217 up-regulation abrogated the tumor suppressing effects of CTBP1-AS2 knockdown.

Conclusion

CTBP1-AS2 regulates CC progression via sponging miR-3163 to up-regulate ZNF217.

Long noncoding RNA PSMA3‑AS1 functions as a microRNA‑409‑3p sponge to promote the progression of non‑small cell lung carcinoma by targeting spindlin 1

PSMA3 antisense RNA 1 (PSMA3‑AS1), a long noncoding RNA, promotes the progression of esophageal squamous cell carcinoma. However, no study to date has explored the expression or roles of PSMA3‑AS1 in non‑small cell lung carcinoma (NSCLC). The present study examined the expression profile and role of PSMA3‑AS1 in NSCLC. It also aimed to identify how PSMA3‑AS1 promotes the malignant phenotype of NSCLC cells. PSMA3‑AS1 expression in NSCLC tissues and cell lines was measured by reverse transcription‑quantitative polymerase chain reaction. Cell Counting Kit‑8, cell apoptosis, Transwell migration and invasion, and xenograft tumor assays were conducted to study the effects of PSMA3‑AS1 on the aggressive phenotype of NSCLC cells. Furthermore, bioinformatics analysis, RNA immunoprecipitation, luciferase reporter assay, western blotting, and rescue experiments were used to elucidate the interaction among PSMA3‑AS1, microRNA‑409‑3p (miR‑409‑3p), and spindlin 1 (SPIN1) in NSCLC cells. In the present study, high levels of PSMA3‑AS1 were confirmed in both NSCLC tissues and cell lines. An increased PSMA3‑AS1 level was correlated with advanced tumor‑node‑metastasis stage and increased lymph node metastasis. Patients with NSCLC with high PSMA3‑AS1 levels had shorter overall survival than those with low PSMA3‑AS1 levels. PSMA3‑AS1 depletion significantly decreased NSCLC cell proliferation, migration, and invasion, as well as substantially increased cell apoptosis in vitro. Furthermore, PSMA3‑AS1 deficiency decreased NSCLC tumor growth in vivo. Through molecular mechanism assays, it was revealed that PSMA3‑AS1 acted as a molecular sponge for miR‑409‑3p and consequently increased SPIN1 expression. Notably, rescue experiments revealed that the inhibition of miR‑409‑3p or restoration of SPIN1 expression abrogated the effects of PSMA3‑AS1 knockdown in NSCLC cells. Collectively, PSMA3‑AS1 functioned as an oncogenic long noncoding RNA in NSCLC. PSMA3‑AS1 sponged miR‑409‑3p and thus increased SPIN1 expression, promoting the aggressive phenotype of NSCLC cells.

Exosomal long non-coding RNA DLX6-AS1 as a potential diagnostic biomarker for non-small cell lung cancer

Distal-less homeobox 6 antisense RNA 1 (DLX6-AS1) is upregulated in various solid tumors and serves a critical role in the tumorigenesis of cancer. However, to the best of our knowledge, the expression of circulating DLX6-AS1 and its role in the diagnosis of non-small cell lung cancer (NSCLC) have not been previously clarified. The aim of the present study was to investigate the expression and clinical significance of circulating DLX6-AS1 using reverse transcription-quantitative PCR in serum and exosomes derived from patients with NSCLC and healthy donors. The diagnostic value of circulating DLX6-AS1 was identified by receiver operating characteristic curve (ROC) analysis. First, it was revealed that the expression levels of DLX6-AS1 were significantly increased in tumor tissues compared with in adjacent normal tissues. In addition, DLX6-AS1 was highly expressed in NSCLC cell lines compared with in BEAS-2B cells. DLX6-AS1-knockdown inhibited cell proliferation and migration in vitro. It was subsequently demonstrated that the serum DLX6-AS1 level was significantly higher in patients with NSCLC compared with in healthy controls. Additionally, the higher DLX6-AS1 expression was associated with advanced disease stage, positive lymph node metastasis and poor tumor differentiation of NSCLC. ROC analysis demonstrated that the sensitivity and specificity of DLX6-AS1 were higher than those of CYFRA21-1, which is a serum marker for NSCLC. Finally, exosomal DLX6-AS1 expression was increased in patients with NSCLC compared with in healthy controls. The present data implied that circulating DLX6-AS1 was mainly incorporated into exosomes, providing a novel potential diagnostic marker for NSCLC.