Circ_ASPH promotes cholangiocarcinoma growth and metastasis through the miR-581/ATP-binding cassette transporter G1 signaling pathway

The role of ATP-binding cassette subfamily G member 1 in tumor progression

BACKGROUND

ATP-binding cassette subfamily G member 1 is mostly known as a transporter for intracellular cholesterol efflux, and a number of studies indicate that ABCG1 also functions actively in tumor initiation and progression. This review aimed to provide an overall review of how ABCG1 acts in tumor progression.

METHOD

A comprehensive searching about ABCG1 and tumor was conducted up to November 2023 using proper keywords through databases including PubMed and Web of Science.

RESULT

Overall, ABCG1 plays a crucial role in the development of multiple tumorigenesis. ABCG1 enhances tumor-promoting ability through conferring stem-like properties to cancer cells and mediates chemoresistance in multiple cancers. Additionally, ABCG1 may act as a kinase to phosphorylate downstream molecules and induces tumor growth. In tumor microenvironment, ABCG1 plays a substantial role in immunity response through macrophages to create a tumor-favoring circumstance.

CONCLUSION

High expression of ABCG1 is usually associated with poor prognosis, which means ABCG1 may be a potential biomarker for early diagnosis and prognosis of various cancers. ABCG1-targeted therapy may provide a novel treatment for cancer patients.

ZEB1-mediated biogenesis of circNIPBL sustains the metastasis of bladder cancer via Wnt/β-catenin pathway

BACKGROUND

Circular RNAs (circRNAs) circularized by back-splicing of pre-mRNA are widely expressed and affected the proliferation, invasion and metastasis of bladder cancer (BCa). However, the mechanism underlying circRNA biogenesis in mediating the distant metastasis of BCa still unexplored.

METHODS

RNA sequencing data between BCa and normal adjacent tissues was applied to identify the differentially expressed circRNAs. The functions of circNIPBL in BCa were investigated via a series of biochemical experiments. The Clinical significance of circNIPBL was examined in a cohort of larger BCa tissues.

RESULTS

In the present study, we identified a novel circRNA (hsa_circ_0001472), circNIPBL, which was significantly upregulated and had great influence on the poor prognosis of patients with BCa. Functionally, circNIPBL promotes BCa metastasis in vitro and in vivo. Mechanistically, circNIPBL upregulate the expression of Wnt5a and activated the Wnt/β-catenin signaling pathway via directly sponged miR-16-2-3p, leading to the upregulation of ZEB1, which triggers the EMT of BCa. Moreover, we revealed that ZEB1 interacted with the flanking introns of exons 2-9 on NIPBL pre-mRNA to trigger circNIPBL biogenesis, thus forming a positive feedback loop. Importantly, circNIPBL overexpression significantly facilitated the distant metastasis of BCa in the orthotopic bladder cancer model, while silencing ZEB1 remarkably blocked the effects of metastasis induced by circNIPBL overexpression.

CONCLUSIONS

Our study highlights that circNIPBL-induced Wnt signaling pathway activation triggers ZEB1-mediated circNIPBL biogenesis, which forms a positive feedback loop via the circNIPBL/miR-16-2-3p/Wnt5a/ZEB1 axis, supporting circNIPBL as a novel therapeutic target and potential biomarker for BCa patients.

The potential role and mechanism of circRNA/miRNA axis in cholesterol synthesis

Cholesterol levels are an initiating risk factor for atherosclerosis. Many genes play a central role in cholesterol synthesis, including HMGCR, SQLE, HMGCS1, FDFT1, LSS, MVK, PMK, MVD, FDPS, CYP51, TM7SF2, LBR, MSMO1, NSDHL, HSD17B7, DHCR24, EBP, SC5D, DHCR7, IDI1/2. Especially, HMGCR, SQLE, FDFT1, LSS, FDPS, CYP51, and EBP are promising therapeutic targets for drug development due to many drugs have been approved and entered into clinical research by targeting these genes. However, new targets and drugs still need to be discovered. Interestingly, many small nucleic acid drugs and vaccines were approved for the market, including Inclisiran, Patisiran, Inotersen, Givosiran, Lumasiran, Nusinersen, Volanesorsen, Eteplirsen, Golodirsen, Viltolarsen, Casimersen, Elasomeran, Tozinameran. However, these agents are all linear RNA agents. Circular RNAs (circRNAs) may have longer half-lives, higher stability, lower immunogenicity, lower production costs, and higher delivery efficiency than these agents due to their covalently closed structures. CircRNA agents are developed by several companies, including Orna Therapeutics, Laronde, and CirCode, Therorna. Many studies have shown that circRNAs regulate cholesterol synthesis by regulating HMGCR, SQLE, HMGCS1, ACS, YWHAG, PTEN, DHCR24, SREBP-2, and PMK expression. MiRNAs are essential for circRNA-mediated cholesterol biosynthesis. Notable, the phase II trial for inhibiting miR-122 with nucleic acid drugs has been completed. Suppressing HMGCR, SQLE, and miR-122 with circRNA_ABCA1, circ-PRKCH, circEZH2, circRNA-SCAP, and circFOXO3 are the promising therapeutic target for drug development, specifically the circFOXO3. This review focuses on the role and mechanism of the circRNA/miRNA axis in cholesterol synthesis in the hope of providing knowledge to identify new targets.

Inhibition of circular RNA ASPH reduces the proliferation and promotes the apoptosis of hepatic stellate cells in hepatic fibrosis

Circular RNAs (circRNAs) are a newly identified form of non-coding RNA that play a crucial role in various pathological processes. However, the expression profile and function of circRNAs in hepatic fibrosis (HF) remain largely unknown. In this study, we showed that a novel circRNA ASPH (circASPH) mediates HF by targeting the miR-139-5p/Notch1 axis. We investigated the expression profile of circRNAs in hepatocyte exosomes of mice with HF using circRNA-sequencing and found significant upregulation of circASPH. Loss- and gain-of-function analysis of circASPH was performed to assess its role in HF. Furthermore, we performed luciferase reporter assay, RNA pull-down, and fluorescence in situ hybridization analyses and confirmed that circASPH directly binds to miR-139-5p. We also found that circASPH was upregulated in liver fibrogenesis. Downregulation of circASPH expression inhibited hepatic stellate cell (HSC) activation and proliferation, induced apoptosis, and attenuated mouse liver fibrogenic injury. Mechanistically, circASPH directly targeted miR-139-5p to regulate the expression of Notch1 in HF. Thus, downregulation of circASPH may suppress the activation of HSCs and HF through the circASPH/miR-139-5p/Notch1 axis. Our findings indicated that circASPH may be a potential biomarker for HF diagnosis and therapy.

circPHF16 suppresses prostate cancer metastasis via modulating miR-581/RNF128/Wnt/β-catenin pathway

Circular RNAs (circRNAs) have been recognized as important regulators in tumorigenesis. However, the specific role of circRNAs in prostate cancer is still largely unknown. Here, we identified that circPHF16 was downregulated in prostate cancer (PCa) tissues compared with normal tissues. Functionally, circPHF16 restrained prostate cancer metastasis both in vivo and in vitro. Mechanistically, circPHF16 directly interacted with miR-581, leading to the downregulation of ring finger protein 128 (RNF128) and inhibiting the metastatic ability of PCa. Furthermore, circPHF16-dependent upregulation of RNF128 inactivated Wnt/β-catenin signaling. In total, our findings revealed that circPHF16 suppressed prostate cancer metastasis through the circPHF16/miR-581/Wnt/β-catenin pathways.

Long non-coding RNA COX7C-5 promotes hepatocellular carcinoma progression via miR-581/ZEB2 axis

Long non-coding RNAs (lncRNA) play crucial roles in hepatocellular carcinoma (HCC) progression. However, the functional roles of lncRNAs in HCC still remain largely unknown. Our study aimed to investigate the biological function and potential molecular mechanism of lnc-COX7C-5 in HCC. Here, we show that Lnc-COX7C-5 was significantly upregulated in HCC tissues, which was correlated with poor prognosis in HCC patients. Lnc-COX7C-5 positively regulated proliferation, migration, and invasion of HCC cells. Mechanistically, lnc-COX7C-5 function as a competing endogenous RNA (ceRNA) for miR-581 in HCC cells. Over-expression or knockdown of miR-581 could alter cell phenotypes caused by Lnc-COX7C-5 in HCC. Further investigations indicated that ZEB2 was demonstrated as a downstream target of miR-581. In mouse model, over-expression of Lnc-COX7C-5 facilitate lung metastasis of HCC. Collectively, Lnc-COX7C-5 promote HCC tumorigenesis and progression by targeting the miR-581/ZEB2 axis. Lnc-COX7C-5 may be a potential therapeutic target for HCC.

CircSETD3 (hsa_circ_0000567) inhibits proliferation and induces apoptosis in cholangiocarcinoma cells via downregulation of microRNA-421 expression

Cholangiocarcinoma (CCA) is a fatal tumor associated with chronic inflammation. Circular RNAs (circRNAs) have been evidenced to be involved in tumorigenesis and tumor progression. This study aimed to explore the effects and potential molecular mechanism of circSETD3 in CCA progression. Levels of CircSETD3 and microRNA (miR)-421 in CCA tissue and cell lines were measured using quantitative real-time polymerase-chain reaction (qRT-PCR). A direct target of miR-421 was predicted using TargetScan and further confirmed by a dual-luciferase reporter assay. Cell proliferation and apoptosis were measured using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and flow cytometry, respectively. The activity of caspase-3 was also examined using caspase-3 activity detection kits. Moreover, the levels of B-cell lymphoma-2 modifying factor (BMF), B-cell lymphoma 2 (BCL2), and Bcl-2-associated X protein (BAX) in TFK1 cells were assessed using qRT-PCR and western blot analysis. We found that circSETD3 was downregulated, while miR-421 was upregulated in CCA tissues and cell lines. CircSETD3 negatively regulated miR-421 levels in TFK1 cells. Functional assays revealed that circSETD3-plasmid inhibited cell proliferation, induced apoptosis, promoted caspase-3 activity, enhanced Bax and cleaved-Caspase 3 expression, and reduced Bcl-2 levels, and these effects were reversed by miR-421 mimic. Meanwhile, similar results were observed in miR-421 inhibitor-transfected TFK1 cells, and these results were abolished by BMF-siRNA. BMF, a direct target of miR-421, was downregulated in CCA tissues and cell lines. These findings demonstrate that circSETD3 inhibits proliferation and induces apoptosis in CCA cells by regulating the miR-421/BMF axis, indicating its potential as a promising candidate for CCA therapy.

CircRTN4IP1 regulates the malignant progression of intrahepatic cholangiocarcinoma by sponging miR-541-5p to induce HIF1A production

BACKGROUND

Recent studies indicate that circular RNA (circRNA) serves important roles in the development of intrahepatic cholangiocarcinoma (ICC). However, the role of circRNA reticulon 4 interacting protein 1 (circRTN4IP1) in ICC progression remains unknown.

METHODS

Expression of circRTN4IP1, microRNA-541-5p (miR-541-5p), hypoxia inducible factor 1 subunit alpha (HIF1A) and other indicated protein markers was detected by quantitative real-time polymerase chain reaction or Western blot. The functional effects of circRTN4IP1 knockdown in ICC cells were analyzed by cell counting kit-8, cell colony formation, flow cytometry analysis, Western blot, glucose and lactate kit assays. The positive expression rate of HIF1A was detected by immunohistochemistry assay. The interaction between miR-541-5p and circRTN4IP1 or HIF1A was identified by dual-luciferase reporter, RNA immunoprecipitation or RNA pull-down assays. Xenograft mouse model assay was performed to determine the effect of circRTN4IP1 depletion on tumor formation.

RESULTS

In contrast, ICC tissues and cells showed high expression of circRTN4IP1 and HIF1A, but low expression of miR-541-5p. Knockdown of circRTN4IP1 led to repression of cell proliferation and glucose metabolism, but promotion of cell apoptosis; however, circRTN4IP1 overexpression had opposite effects. In mechanism, circRTN4IP1 acted as a sponge for miR-541-5p, which was found to target HIF1A. MiR-541-5p inhibitors could remit circRTN4IP1 knockdown-mediated action. Also, HIF1A participated in the regulation of miR-541-5p in ICC progression. In support, circRTN4IP1 depletion impeded tumor formation in vivo.

CONCLUSION

CircRTN4IP1 knockdown inhibited ICC cell malignancy by miR-541-5p/HIF1A axis, providing us with a reliable target for the therapy of ICC.

Circ-ELF2 Acts as a Competing Endogenous RNA to Facilitate Glioma Cell Proliferation and Aggressiveness by Targeting MiR-510-5p/MUC15 Signaling

Objective

Glioma (GM) is a common type of malignant and aggressive tumor in brain with poor prognosis. Circular RNAs (circRNAs) are well-known regulators in cancer progression. However, its molecular basis in GM remains to be investigated.

Materials and Methods

CircRNA microarray was used to detect differentially expressed circRNAs in GM and matched noncancerous tissues. qRT-PCR was applied to detect the expression profile of circ-ELF2 in GM tissue specimens and cell lines. CCK-8, clone formation, AO/EB staining, flow cytometry, wound healing, and transwell assays were performed to identify the functions of circ-ELF2 in GM cells. The distribution of circ-ELF2 was analyzed by RNA-FISH and subcellular fractionation assay. Dual-luciferase reporter assay was applied to verify the predicted binding sites between miR-510-5p and circ-ELF2/MUC15 3ʹ-UTR. Rescue assay was finally conducted to explore whether the oncogenic role of circ-ELF2 was partially attributed to miR-510-5p/MUC15 signaling.

Results

We observed that circ-ELF2 was significantly upregulated in GM tissues, which was analyzed by circRNA microarray and qRT-PCR. Upregulation of circ-ELF2 was associated with poor prognosis and high recurrence rate for GM patients after surgery. The collapse of circ-ELF2 caused growth arrest and downregulation of cell migratory and invasive potential of GM cells and promoted cell apoptosis. In contrast, elevated expression of circ-ELF2 led to the opposite effect. Mechanistically, circ-ELF2 acted as a competing endogenous RNA (ceRNA) for miR-510-5p to positive modulate MUC15 expression at posttranscriptional level. Circ-ELF2 upregulated MUC15 by sponging miR-510-5p, thus promoting GM growth and aggressiveness.

Conclusion

This study indicates that circ-ELF2/miR-510-5p/MUC15 signaling plays a key role in promoting the occurrence and development of GM.