The Biogenesis, Functions, and Roles of circRNAs in Bladder Cancer

CircHGS enhances the progression of bladder cancer by regulating the miR-513a-5p/VEGFC axis and activating the AKT/mTOR signaling pathway

Bladder cancer (BCa) is a malignant tumor that occurs in the bladder mucosa with high mortality. Circular RNAs (circRNAs), as newly discovered noncoding RNAs, are associated with the occurrence and development of BCa. However, the effects of circRNAs in BCa have not been fully elucidated. Through the GEO (Gene Expression Omnibus) database, an abnormally expressed circular RNA, circHGS (hsa_circ_0004721), was first identified in BCa. qRT - PCR was performed to measure the expression of circHGS in BCa tissues and cells. The intracellular localization of circHGS was detected by nucleocytoplasmic separation experiment and fluorescence in situ hybridization assay. In vitro experiments were conducted to detect the effects of circHGS on cell cycle, proliferation, migration and invasion. The correlations between miR-513a-5p and circHGS or VEGFC were confirmed by dual-luciferase reporter assay, qRT - PCR and western blot. The role of circHGS in vivo was verified by xenograft tumor mice model. In this study, we clarified the roles and potential mechanism of circHGS in BCa. CircHGS, originating from the HGS gene, is upregulated in BCa tissues compared to normal tissues. Moreover, the expression of circHGS in BCa was positively associated with tumor grade and pathological T stage. Functionally, silencing of circHGS apparently suppressed cell cycle, proliferation, migration and invasion, but circHGS overexpression showed the opposite result. In vivo experiments also suggested that knockdown of circHGS suppressed tumor growth. Mechanistically, circHGS functions as a sponge of miR-513a-5p to elevate VEGFC expression and activate the AKT/mTOR signaling pathway, ultimately promoting BCa progression. Our findings indicated that circHGS promotes BCa progression via the miR-513a-5p/VEGFC/AKT/mTOR pathway and can be a promising therapeutic target of BCa.

Biogenesis, functions, and clinical implications of circular RNAs in non-small cell lung cancer

Lung cancer (LC) is the leading cause of cancer-related deaths worldwide, with high morbidity and mortality. Non-small cell lung cancer (NSCLC) is a major pathological type of LC and accounts for more than 80% of all cases. Circular RNAs (circRNAs) are a large class of non-coding RNAs (ncRNAs) with covalently closed-loop structures, a high abundance, and tissue-specific expression patterns. They participate in various pathophysiological processes by regulating complex gene networks involved in proliferation, apoptosis, migration, and epithelial-to-mesenchymal transition (EMT), as well as metastasis. A growing number of studies have revealed that the dysregulation of circRNAs contributes to many aspects of cancer progression, such as its occurrence, metastasis, and recurrence, suggesting their great potential as efficient and specific biomarkers in the diagnosis, prognosis, and therapeutic targeting of NSCLC. In this review, we systematically elucidate the characteristics, biogenesis, and functions of circRNAs and focus on their molecular mechanisms in NSCLC progression. Moreover, we highlight their clinical implications in NSCLC treatment.

Identification of the circRNA-miRNA-mRNA Regulatory Network in Bladder Cancer by Bioinformatics Analysis

In recent years, increasing evidence shows that circular RNA (circRNA) disorder is closely related to tumorigenesis and cancer progression. However, the regulatory functions of most circRNAs in bladder cancer (BCa) remain unclear. This study was aimed at exploring the molecular regulatory mechanism of circRNAs in BCa. We obtained four datasets of circRNA, microRNA (miRNA), and messenger (mRNA) expression profiles from the Gene Expression Omnibus and The Cancer Genome Atlas microarray databases and identified 434, 367, and 4799/4841 differentially expressed circRNAs, miRNAs, and mRNAs, respectively. With these differentially expressed RNAs, we established a circRNA-miRNA-mRNA targeted interaction network. A total of 18, 24, and 51 central circRNAs, miRNAs, and mRNAs were identified, respectively. Among them, the top 10 mRNAs that had high connectivity with other circRNAs and miRNAs were regarded as hub genes. We detected the expression levels of these 10 mRNAs in 16 pairs of BCa tissues and adjacent normal tissues through quantitative real-time polymerase chain reaction. The differentially expressed mRNAs and central mRNAs were enriched in the processes and pathways that are associated with the growth, differentiation, proliferation, and apoptosis of tumor cells. The outstanding genes (CDCA4, GATA6, LATS2, RHOB, ZBTB4, and ZFPM2) also interacted with numerous drugs, indicating their potency as biomarkers and drug targets. The findings of this study provide a deep understanding of the circRNA-related competitive endogenous RNA regulatory mechanism in BCa pathogenesis.

Emerging Roles of Circular RNAs in Thyroid Cancer

Thyroid cancer (TC) has the highest incidence among endocrine malignancies. Thus, it is essential to achieve a deep understanding of various mechanisms of development and progression of TC. circRNAs are recognized by multiple studies as being dysregulated in TC. Accumulating evidences have revealed that circRNAs serve as regulatory molecules involved in various biological processes in TC, including cell proliferation, apoptosis, invasion/migration, metabolism, and chemoresistance. Furthermore, circRNA can also serve as an effective tool in TC researches of diagnosis, prognosis, and treatments. Thus, this review is to outline the characteristics of circRNAs, generalize their categories and functions, and highlight the expression of circRNAs in TC. Meanwhile, we are expecting to achieve a comprehensive understanding of new therapies based on circRNAs in treating or preventing TC.

circCEP128 Knockdown Suppresses Bladder Cancer Progression via Regulating microRNA-515-5p/SDC1 Axis

Background

Dysregulation of circular RNAs (circRNAs) is associated with bladder cancer progression. Nevertheless, the mechanisms of circRNA centrosomal protein 128 (circCEP128) underlying bladder cancer progression remain poorly understood.

Methods

The levels of circCEP128, microRNA-515-5p (miR-515-5p) and syndecan-1 (SDC1) were determined via reverse transcription-quantitative polymerase chain reaction or Western blot. The effects of circCEP128, miR-515-5p and SDC1 on bladder cancer progression were investigated via MTT and colony formation assays, flow cytometry and transwell analysis and subcutaneous xenograft experiments. The interactions between miR-515-5p and circCEP128 or SDC1 were examined through bioinformatics prediction and luciferase reporter assay.

Results

circCEP128 and SDC1 were highly expressed and miR-515-5p was low expressed in bladder cancer tissues and cells. circCEP128 knockdown hindered cell proliferation, migration and invasion and promoted cell apoptosis in bladder cancer. circCEP128 loss increased miR-515-5p expression through direct interaction in bladder cancer cells. MiR-515-5p depletion mitigated the influences of circCEP128 knockdown on bladder cancer cell phenotypes. SDC1 was a direct target of miR-515-5p. circCEP128 positively regulated SDC1 expression via miR-515-5p. MiR-515-5p restrained the malignant progression of bladder cancer cells by decreasing SDC1 expression. circCEP128 knockdown hindered the growth of bladder cancer xenograft tumors by up-regulating miR-515-5p and down-regulating SDC1.

Conclusion

circCEP128 knockdown hampered the tumorigenesis and progression of bladder cancer by regulating miR-515-5p/SDC1 axis in vitro and in vivo, deepening our understanding on the molecular mechanisms of circCEP128 in bladder cancer.

Circular RNA_0000629 Suppresses Bladder Cancer Progression Mediating MicroRNA-1290/CDC73

Background

Recent studies showed circular RNAs (circRNAs) played regulatory roles in bladder cancer (BC). However, the relevance of circ_0000629, a newly identified circRNA, has not been determined yet. We aimed to characterize the function of circ_0000629 in BC and the relevant mechanism.

Methods

First, we downloaded circRNA-related microarrays GSE147985 and GSE92675 from the GEO database, followed by a validation in our clinically obtained samples. We then overexpressed circ_0000629 in T24 and SW780 cells and evaluated the effects of circ_0000629 on BC cell proliferatory, apoptotic, and metastatic abilities. We further detected the subcellular localization of circ_0000629 in T24 and SW780 cells by the fractionation and export assay and FISH experiments. Integrated microarray analyses and bioinformatics website prediction were utilized to screen out the downstream microRNA (miRNA)/mRNA. The effects of miR-1290 and CDC73 on BC cell growth and metastasis was verified by functional rescue experiments. In addition, mice xenografts were built to measure the effect of circ_0000629 on tumor growth in vivo.

Results

Circ_0000629 and CDC73 were reduced, and miR-1290 was significantly overexpressed in BC tissues and cells. Moreover, circ_0000629 significantly inhibited the development and metastasis of BC cells, but further overexpression of miR-1290 or knockdown of CDC73 attenuated the inhibitory effect of circ_0000629 on BC cells. Circ_0000629 localized in the cytoplasm and regulated CDC73 expression by sponging miR-1290. Further, overexpressed circ_0000629 reduced the BC tumor growth in vivo.

Conclusion

Circ_0000629 promotes the expression of CDC73 by competitively binding to miR-1290, thereby inhibiting the growth and metastasis of BC cells.