Circular RNA expression profile in peripheral whole blood of lung adenocarcinoma by high: Throughput sequencing

Serum Exosomes-Based Biomarker circ_0008928 Regulates Cisplatin Sensitivity, Tumor Progression, and Glycolysis Metabolism by miR-488/HK2 Axis in Cisplatin-Resistant Nonsmall Cell Lung Carcinoma

Background: Nonsmall cell lung carcinoma (NSCLC) is a major cause of cancer-related death worldwide. The resistance of NSCLC to chemical drugs, such as cisplatin (CDDP), poses a heavy burden for NSCLC therapy. Herein, the effects of circular_0008928 (circ_0008928) on the CDDP sensitivity and biological behavior of CDDP-resistant NSCLC cells and underlying mechanism are revealed. Materials and Methods: The expression of circ_0008928 and microRNA-488 (miR-488) was detected by quantitative real-time polymerase chain reaction. The expression of hexokinase 2 (HK2) protein and exosome-specific proteins was determined by Western blot. The half-maximal inhibitory concentration (IC50) value of CDDP was detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cell proliferation and migratory and invasive abilities were illustrated by cell counting kit-8 and transwell assays. Cell glycolysis metabolism was illustrated by extracellular acidification rate assay, glucose kit and lactate kit assays and Western blot analysis. The binding sites between miR-488 and circ_0008928 or HK2 were predicted by starbase or microT-CDS online database, and identified by dual-luciferase reporter and RNA immunoprecipitation assays. Results: Circ_0008928 expression and HK2 protein expression were significantly upregulated, while miR-488 expression was obviously downregulated in NSCLC cells and CDDP-resistant NSCLC cells. Circ_0008928 expression was increased in serum exosomes of CDDP-resistant NSCLC patients compared with CDDP-sensitive NSCLC patients. In addition, circ_0008928 silencing improved CDDP sensitivity and attenuated CDDP-induced cell proliferation, migration, invasion, and glycolysis metabolism. Circ_0008928 was a sponge of miR-488, and miR-488 bound to HK2 in CDDP-resistant NSCLC cells. Furthermore, both miR-488 inhibitor and HK2 overexpression attenuated circ_0008928 absence-mediated impacts on CDDP sensitivity and tumor process in CDDP-resistant NSCLC. Conclusions: Circ_0008928 knockdown improved CDDP sensitivity and hindered cell proliferation, migration, invasion, and glycolysis metabolism by miR-488/HK2 axis in CDDP-resistant NSCLC. This finding provides a new mechanism for studying CDDP-resistant therapy in NSCLC.

CircRNA6783 Inhibits Cell Proliferation and Promotes Apoptosis in Lung Adenocarcinoma

Purpose

Circular RNA (circRNA) serves an important role in tumour genesis and development. But, little is known about its role in lung adenocarcinoma (LA). This study aimed to investigate circRNA6783 expression in peripheral whole blood (PWB) of LA and controls and explore its effect on proliferation and apoptosis in human lung adenocarcinoma cells (LAC).

Patients and Methods

The levels of circRNA6783 in LA cell lines and peripheral whole blood (PWB) of 40 patients and 30 controls were detected by real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR). In order to explore the effect of circRNA6783 on LA behavior, we overexpressed circRNA6783 in NCI-H1975 cells. The impact on the proliferation of tumor cells was then examined by Cell Counting Kit 8 (CCK8) assay, and the effects on apoptosis in the cell line were detected using flow cytometry.

Results

The expression levels of circRNA6783 were significantly higher in LA cell lines and PWB (P < 0.05). The diagnostic value of the area under the receiver operating characteristic curve (AUC) was 0.830, with a sensitivity of 60% and specificity of 96.7%. In addition, functional experiments showed that overexpression of circRNA6783 restrained cell proliferation, significantly increased spontaneous apoptosis.

Conclusion

CircRNA6783 was upregulated in LA PWB. In vitro assessment demonstrated that circRNA6783 could act as a potential biomarker for LA diagnosis.

Emerging roles of circular RNAs in non‑small cell lung cancer (Review)

Circular RNAs (circRNAs) are a class of novel endogenous transcripts with limited protein‑coding abilities. CircRNAs have been demonstrated to function as critical regulators of tumor development and distant metastasis through binding to microRNAs (miRNAs) and interacting with RNA‑binding proteins, thereby regulating transcription and translation. Emerging evidence has illustrated that certain circRNAs can serve as biomarkers for diagnosis and prognosis of cancer, and/or serve as potential therapeutic targets. Expression of functional circRNAs is commonly dysregulated in cancer and this is correlated with advanced Tumor‑Node‑Metastasis stage, lymph node status, distant metastasis, poor differentiation and shorter overall survival of cancer patients. Recently, an increasing number of studies have shown that circRNAs are closely associated with NSCLC. Functional experiments have revealed that circRNAs are intricately associated with the pathological progression of NSCLC. The present review provides an overview of the regulatory effect of circRNAs in the development and progression of NSCLC, taking into consideration various physiological and pathological processes, such as proliferation, apoptosis, invasion and migration, and their potential value as biomarkers and therapeutic targets.

Plasma circular RNA panel acts as a novel diagnostic biomarker for colorectal cancer detection

Circular RNAs (circRNAs) can function as key regulators of oncogenic processes, making them ideal diagnostic biomarkers of many cancers. However, few studies to date have reported on plasma circRNA profiles associated with colorectal cancer (CRC). To that end, we herein employed microarray- and qRT-PCR-based approaches to evaluate circulating plasma circRNAs in CRC patients. Area under the receiver operating characteristic curve (AUC) values were then used to assess the diagnostic utility of these circRNAs. We ultimately determined that hsa_circ_0001900, hsa_circ_0001178, and hsa_circ_0005927 were upregulated in the plasma of CRC patients relative to healthy controls and were correlated with clinicopathological findings in these patients. We further established that a panel composed of these three circRNAs (CircPanel) was able to differentiate between patients with and without CRC more reliably than CEA (carcinoembryonic antigen) (AUC, 0.859 [95% confidence interval, CI: 0.805-0.903] vs. 0.698 [0.631-0.759], P=0.0003), enabling us to detect patients with CEA-negative CRC. In conclusion, our study reveals that CircPanel could serve as a promising potential biomarker for CRC diagnosis.

Knockdown of circPRKCA Restrained Cell Growth, Migration, and Invasion of NSCLC Cells Both in vitro and in vivo via Regulating miR-330-5p/PDK1/AKT Pathway

Background

Protein kinase Cα (PRKCA) is an oncogene in multiple cancers including non-small-cell lung cancer (NSCLC) and can be transcribed into a number of circular PRKCAs (circPRKCAs). Here, we aimed to elaborate the role and mechanism of circPRKCA_024 (circPRKCA) in malignant progression of NSCLC.

Methods

Expression of circPRKCA, miRNA (miR)-330-5p and 3-phosphoinositide-dependent protein kinase-1 (PDK1) was measured by real-time quantitative PCR and Western blotting, and their relationship was testified by dual-luciferase reporter assay, RNA immunoprecipitation, and RNA pull-down assay. Cell behaviors were evaluated by cell counting kit (CCK)-8, flow cytometry, and transwell assays. AKT activity was confirmed by Western blotting. Xenograft experiment assessed tumor growth.

Results

Expression of circPRKCA and PDK1 was upregulated, and miR-330-5p was downregulated in NSCLC tissues and cell lines. High circPRKCA was correlated with TNM stage and lymph node metastasis of NSCLC patients. Silencing circPRKCA could suppress cell viability, migration, and invasion in A549 and H1299 cells, accompanied with apoptosis rate promotion. Moreover, circPRKCA knockdown retarded tumor growth of A549 cells in vivo. Molecularly, miR-330-5p was sponged by circPRKCA, and PDK1 was a target of miR-330-5p. Inhibiting miR-330-5p could attenuate the suppression of circPRKCA knockdown on cell growth, migration, and invasion; contrarily, promoting miR-330-5p caused inhibition on those cell behaviors by downregulating PDK1. Analogously, AKT activity was suppressed by circPRKCA downregulation and miR-330-5p upregulation in NSCLC cells both in vitro and in vivo.

Conclusion

Depleting circPRKCA inhibited PDK1 to suppress NSCLC cell malignant behaviors through miR-330-5p/PDK1/AKT pathway.

A Regulatory Axis of circ_0008193/miR-1180-3p/TRIM62 Suppresses Proliferation, Migration, Invasion, and Warburg Effect in Lung Adenocarcinoma Cells Under Hypoxia

BACKGROUND Expression profiles of circular ribonucleic acids (circRNAs) have been recently reported in lung cancers including lung adenocarcinoma (LUAD). Hypoxia is a hallmark of lung cancers. However, the role of hsa_circ_0008193 (circ_0008193) in LUAD under hypoxia remains to be illuminated. MATERIAL AND METHODS Gene expression levels were detected using real-time quantitative polymerase chain reaction and western blotting. Cell proliferation, migration, invasion, and Warburg effect were detected using 3-(4, 5-dimethylthiazol-2-yl)-2, 5 diphenyltetrazolium bromide assay, transwell assays, special kits, and xenograft experiments. The relationship among circ_0008193, micro (mi)RNA (miR)-1180-3p, and tripartite motif containing 62 (TRIM62) was confirmed by dual-luciferase reporter assay and RNA immunoprecipitation. RESULTS Expression of circ_0008193 was downregulated in human LUAD tumor tissues and cell lines (A549 and H1975), accompanied by miR-1180-3p upregulation and TRIM62 downregulation. Moreover, circ_0008193 downregulation was correlated with tumor size and lymph node metastasis. Functionally, circ_0008193 overexpression inhibited cell viability, glucose uptake, lactate production, migration, and invasion, as well as expression of hexokinase II, lactate dehydrogenase A, matrix metalloproteinase 2 (MMP2), and MMP9 in hypoxic LUAD cells in vitro. Furthermore, tumor growth of A549 cells in vivo was also hindered by circ_0008193 overexpression. Mechanically, circ_0008193 regulated TRIM62 expression via sponging miR-1180-3p, and TRIM62 was targeted by miR-1180-3p. Both miR-1180-3p upregulation and TRIM62 downregulation could abolish the suppressive role of circ_0008193 in LUAD cells. CONCLUSIONS Upregulating circ_0008193 inhibited LUAD cell proliferation, migration, invasion, and Warburg effect under hypoxia in vitro and in vivo through regulation of the miR-1180-3p/TRIM62 axis.

Instability of circular RNAs in clinical tissue samples impairs their reliable expression analysis using RT-qPCR: from the myth of their advantage as biomarkers to reality

Background: Circular RNAs (circRNAs) are a new class of RNAs with medical significance. Compared to that of linear mRNA transcripts, the stability of circRNAs against degradation owing to their circular structure is considered advantageous for their use as biomarkers. As systematic studies on the stability of circRNAs depending on the RNA integrity, determined as RNA integrity number (RIN), in clinical tissue samples are lacking, we have investigated this aspect in the present study under model and clinical conditions.

Methods: Total RNA isolated from kidney cancer tissue and cell lines (A-498 and HEK-293) with different RIN after thermal degradation was used in model experiments. Further, RNA isolated from kidney cancer and prostate cancer tissue collected under routine surgical conditions, representing clinical samples with RIN ranging from 2 to 9, were examined. Quantitative real-time reverse-transcription polymerase chain reaction (RT-qPCR) analysis of several circRNAs (circEGLN3, circRHOBTB3, circCSNK1G3, circRNA4, and circRNA9), their corresponding linear counterparts, tissue-specific reference genes, and three microRNAs (as controls) was performed. The quantification cycles were converted into relative quantities and normalized to the expression of specific reference genes for the corresponding tissue. The effect of RIN on the expression of different RNA entities was determined using linear regression analysis, and clinical samples were classified into two groups based on RIN greater or lesser than 6.

Results: The results of model experiments and clinical sample analyses showed that all relative circRNA expression gradually decreased with reduction in RIN values. The adverse effect of RIN was partially compensated after normalizing the data and limiting the samples to only those with RIN values > 6.

Conclusions: Our results suggested that circRNAs are not stable in clinical tissue samples, but are subjected to degradative processes similar to mRNAs. This has not been investigated extensively in circRNA expression studies, and hence must be considered in future for obtaining reliable circRNA expression data. This can be achieved by applying the principles commonly used in mRNA expression studies.

circ_0007385 served as competing endogenous RNA for miR-519d-3p to suppress malignant behaviors and cisplatin resistance of non-small cell lung cancer cells

Background

Circular RNAs (circRNAs) have been closely implicated in competing endogenous RNA (ceRNA) network among human cancers including non‐small cell lung cancer (NSCLC). However, the role of most circRNAs in NSCLC remains to be determined. Here, we aimed to investigate the role of hsa_circ_0007385 (circ_0007385) in NSCLC cells.

Methods

Expression of hsa_circ_0007385 (circ_0007385), miRNA (miR)‐519d‐5p and high‐mobility group box 1 (HMGB1) was measured by real‐time quantitative PCR and western blotting. Functional experiments were evaluated by cell counting kit (CCK)‐8, flow cytometry, fluorescein active caspase‐3 staining kit, transwell assays, western blotting, and xenograft experiment. The relationship among circ_0007385,miR‐519d‐5p and HMGB1 was testified by dual‐luciferase reporter assay. Kaplan‐Meiersurvival curve identified overall survival in NSCLC patients.

Results

circ_0007385 expression was higher in NSCLC tissues and cell lines, and was associated with poor overall survival. Silencing circ_0007385 could suppress cell proliferation, migration and invasion in A549 and H1975 cells, as well as cisplatin (DDP) resistance. Moreover, circ_0007385 silence retarded tumor growth of A549 cells in vivo. Molecularly, there was a direct interaction between miR‐519d‐3p and either circ_0007385 or HMGB1; expression of miR‐519d‐3p was downregulated in NSCLC tumors in a circ_0007385‐correlated manner, and circ_0007385 could indirectly regulate HMGB1 via miR‐519d‐3p. Functionally, both inhibiting miR‐519d‐3p and restoring HMGB1 could overturn the suppressive effect of circ_0007385 knockdown on cell proliferation, migration, invasion, and DDP resistance.

Conclusions

Collectively, circ_0007385 deletion could function anti‐tumor role in NSCLC by suppressing malignant behaviors and DDP resistance in vitro and in vivo via circ_0007385/miR‐519d‐3p/HMGB1 axis. These outcomes might enhance our understanding of the molecular mechanisms underlying the malignant progression of NSCLC.

Key points

Significant findings of the study

circ_0007385 was upregulated in NSCLC tissues and cells, and was associated with poor overall survival.

Silenced circ_0007385 suppressed NSCLC cell proliferation, migration, invasion, and DDP resistance in vitro, and tumor growth in vivo.

circ_0007385 was upregulated in NSCLC tissues and cells, and was associated with poor overall survival.

What this study adds

miR‐519d‐3p could directly interact with circ_0007385 and HMGB1 in NSCLC cells.

A promising circ_0007385/miR‐519d‐3p/HMGB1 regulatory pathway was determined in NSCLC cells.