Circular RNA Myosin Light Chain Kinase (MYLK) Promotes Prostate Cancer Progression through Modulating Mir-29a Expression

Circular RNAs add diversity to androgen receptor isoform repertoire in castration-resistant prostate cancer

Deregulated expression of circular RNAs (circRNAs) is associated with various human diseases, including many types of cancer. Despite their growing links to cancer, there has been limited characterization of circRNAs in metastatic castration-resistant prostate cancer, the major cause of prostate cancer mortality. Here, through the analysis of an exome-capture RNA-seq dataset from 47 metastatic castration-resistant prostate cancer samples and ribodepletion and RNase R RNA-sequencing of patient-derived xenografts (PDXs) and cell models, we identified 13 circRNAs generated from the key prostate cancer driver gene-androgen receptor (AR). We validated and characterized the top four most abundant, clinically relevant AR circRNAs. Expression of these AR circRNAs was upregulated during castration-resistant progression of PDXs. The upregulation was not due to global increase of circRNA formation in these tumors. Instead, the levels of AR circRNAs correlated strongly with that of the linear AR transcripts (both AR and AR-variants) in clinical samples and PDXs, indicating a transcriptional mechanism of regulation. In cultured cells, androgen suppressed the expression of these AR circRNAs and the linear AR transcripts, and the suppression was attenuated by an antiandrogen. Using nuclear/cytoplasmic fractionation and RNA in-situ hybridization assays, we demonstrated predominant cytoplasmic localization of these AR circRNAs, indicating likely cytoplasmic functions. Overall, this is the first comprehensive characterization of circRNAs arising from the AR gene. With greater resistance to exoribonuclease compared to the linear AR transcripts and detectability of AR circRNAs in patient plasma, these AR circRNAs may serve as surrogate circulating markers for AR/AR-variant expression and castration-resistant prostate cancer progression.

Circular RNA MYLK promotes hepatocellular carcinoma progression by increasing Rab23 expression by sponging miR-362-3p

Background

CircRNA myosin light chain kinase (circRNA MYLK) has been shown to promote the progression of various tumor diseases. The purpose of this study was to explore the potential molecular mechanism of circMYLK in hepatocellular carcinoma (HCC).

Methods

The quantitative Real-Time PCR (qRT-PCR) was used to measure the expressions of circMYLK, miR-362-3p and Rab23 in HCC tissues and cell lines. Huh7 and Hep3B cells were selected to explore the role of circMYLK in proliferation, invasion and migration of HCC cells in vitro. The interaction among circMYLK, miR-362-3p and Rab23 was investigated by biological information and dual luciferase gene reporter assay. The effect of circMYLK on HCC tumor growth in vivo was studied in a tumor xenograft model in mice.

Results

CircMYLK was highly expressed in HCC tissues and cell lines, which was associated with poor prognosis in HCC patients. In addition, knockdown of circMYLK remarkably inhibited the proliferation, invasion, and migration of Huh7 and Hep3B cells. MiR-362-3p was a direct target of circMYLK, and Rab23 was a direct target gene of miR-362-3p. Meanwhile, circMYLK was negatively correlated with the expression of miR-362-3p and positively correlated with Rab23 expression. Moreover, either overexpressed miR-362-3p or silencing Rab23 could observably suppress the enhanced proliferation, invasion, and migration induced by circMYLK in Huh7 and Hep3B cells. Finally, knockdown of circMYLK and overexpressed miR-362-3p could suppress the expression of Rab23, thus inhibiting the growth and proliferation of Hep3B cells in vivo.

Conclusion

circMYLK promotes the occurrence and development of HCC by regulating the miR-362-3p/Rab23 axis, which provides a novel direction and theoretical basis for the early diagnosis and treatment of HCC.

Circular RNA ABCB10 promotes tumor progression and correlates with pejorative prognosis in clear cell renal cell carcinoma

OBJECTIVE

Our study aimed to evaluate the effect of circular RNA ABCB10 (circ-ABCB10) on proliferation and apoptosis of clear cell renal cell carcinoma (ccRCC) cells, and its prognostic value in patients with ccRCC.

METHODS

Circ-ABCB10 expression in five ccRCC cell lines and normal kidney epithelial cell line was measured by quantitative polymerase chain reaction (qPCR). Empty overexpression, circ-ABCB10 overexpression, empty shRNA, and circ-ABCB10 shRNA plasmids were transfected into A498 cells as negative control for circ-ABCB10 over expression {NC (+)}, Circ-ABCB10(+), negative control (-){NC(-)}, and Circ-ABCB10(-) groups, then cell proliferation and apoptosis were evaluated by Cell Counting Kit-8 and annexin V/propidium iodide. Meanwhile, apoptotic markers were measured by western blot. Subsequently, circ-ABCB10 expression in tumor tissues and paired adjacent tissues from 120 ccRCC patients was measured by qPCR.

RESULTS

Circ-ABCB10 expression was elevated in all the ccRCC cell lines compared with the normal kidney cells line. A498 cell proliferation was enhanced in the Circ-ABCB10(+) group compared with the NC(+) group, while it was inhibited in the Circ-ABCB10(-) group compared with the NC (-) group; and A498 cell apoptosis was repressed in the Circ-ABCB10(+) group than the NC(+) group, but was promoted in the Circ-ABCB10(-) group compared with the NC(-) group. In addition, circ-ABCB10 was up-regulated in tumor tissues compared with paired adjacent tissues, and its high expression correlated with the advanced pathological grade and the tumor node metastasis stage as well as independently predicting worse overall survival in ccRCC patients.

CONCLUSION

Circ-ABCB10 promotes tumor progression and correlates with pejorative prognosis in ccRCC.

The emerging roles and functions of circular RNAs and their generation

Circular RNAs (circRNAs) are closed long non-coding RNAs, in which the 5’ and 3’ termini are covalently linked by back-splicing of exons from a single pre-mRNA. Emerging evidence indicates that circRNAs are broadly expressed in mammalian cells and show cell type- or tissue-specific expression patterns. Importantly, circRNAs have been shown to participate in regulating various biological processes. Functionally, circRNAs can influence cellular physiology through various molecular mechanisms, such as serving as a decoy for microRNAs or RNA-binding proteins to modulate gene expression or translation of regulatory proteins. The biogenesis of circRNAs is known to be tightly regulated by cis- (intronic complementary sequences) and/or trans-factors (splicing factors) that constitute a cell- and context-dependent regulatory layer in the control of gene expression. However, our understanding of the regulation and function of circRNAs is still limited. In this review, we summarize the current progress in elucidating the functional roles, mechanisms and biogenesis of circRNAs. We also discuss the relationship between regulation and formation of circRNAs.

Circular RNA DOCK1 promotes bladder carcinoma progression via modulating circDOCK1/hsa-miR-132-3p/Sox5 signalling pathway

Objectives

To reveal the role of circular RNA (circRNA) DOCK1 (circDOCK1) as a potential biomarker and therapeutic target and its competing endogenous RNA mechanism in bladder carcinoma (BC).

Methods

The next‐generation sequencing (NGS) technology was introduced to screen the circRNA expression profiles of BC using microarray. qPCR and Western blots assay were employed to measure the gene expression in different groups. Cell counting kit‐8, EdU and transwell assays were applied to detect the cell viability, proliferation and migration potential, respectively. Luciferase reporter assay was used to test the binds between hsa‐miR‐132‐3p/Sox5. Xenografted tumour growth of nude mice was performed to test the role of circDOCK1 in vivo.

Results

CircDOCK1 was upregulated in BC tissues and cell lines. Repression of circDOCK1 reduced cell viability, inhibited cell proliferation and curbed the cell migration potential of BC cell. CircDOCK1 played its role via regulation of circDOCK1/hsa‐miR‐132‐3p/Sox5 pathway in BC cells. Suppression circDOCK1 inhibited the tumour growth in vivo.

Conclusion

In this study, we revealed that circDOCK1 affected the progression of BC via modulation of circDOCK1/hsa‐miR‐132‐3p/Sox5 pathway both in vitro and in vivo and providing a potential biomarker and therapeutic targets for BC.

Circular RNA circHIPK3 promotes cell proliferation and invasion of prostate cancer by sponging miR-193a-3p and regulating MCL1 expression

BACKGROUND

While emerging evidence indicates that circHIPK3 is critically involved in tumorigenesis and the development of several cancers, its role in prostate cancer (PCa) is not clearly understood.

MATERIALS AND METHODS

Human PCa samples and their matched normal adjacent tissues were obtained from 26 patients to assess the expression of circHIPK3 and its relationship with PCa prognosis. A series of in vitro and in vivo functional experiments were carried out to elucidate the role of circHIPK3 in PCa progression and its underlying molecular mechanisms.

RESULTS

In this study, we found that circHIPK3 was overexpressed in PCa tissues and that higher circHIPK3 expression was associated with tumor stage. Moreover, circHIPK3 knockdown markedly inhibited the proliferation, migration, and invasion of PCa cells in vitro and impaired tumor growth in vivo. Bioinformatics analysis and luciferase reporter assays demonstrated that circHIPK3 could promote MCL1 expression by interacting with miR-193a-3p in PCa. Finally, rescue assays illustrated that circHIPK3 knockdown could partially reverse the effects of MCL1 overexpression.

CONCLUSION

In summary, our study illustrated, for the first time, that circHIPK3-mediated miR-193a-3p-MCL1 signaling promotes PCa development and progression, providing a novel therapeutic target for PCa.

microRNA-205 and microRNA-338-3p Reduces Cell Apoptosis in Prostate Carcinoma Tissue and LNCaP Prostate Carcinoma Cells by Directly Targeting the B-Cell Lymphoma 2 (Bcl-2) Gene

Background

The inhibitor of apoptosis, B-cell lymphoma 2 (Bcl-2), is encoded by the BCL2 gene. Previous studies have shown that microRNAs are downregulated in prostate cancer. This study aimed to investigate the role of microRNA-205 and microRNA-338-3p and cell apoptosis in prostate carcinoma tissue and the LNCaP human prostate adenocarcinoma cell line by directly targeting the BCL2 gene and Bcl-2 protein expression.

Material/Methods

Bioinformatics methods predicted the target genes of miR-205 and miR-338-3p, which were validated by a luciferase assay. Immunohistochemistry was used to detect Bcl-2 protein expression in 30 samples of prostate carcinoma tissue and 30 matched samples of normal prostate. The normal prostate epithelial cell line, RWPE-1, and LNCaP human prostate adenocarcinoma cells studied in vitro. BCL2 mRNA expression and Bcl-2 protein expression were determined by quantitative polymerase chain reaction (q-PCR) and Western blot, respectively. Cell apoptosis was measured by flow cytometry using annexin V, fluorescein isothiocyanate, and phycoerythrin (annexin V-FITC/PE).

Results

TargetScan Human 7.2 predicted that the structures of miR-205 and miR-338-3p had a binding site on the proto-oncogene, BCL2, which was verified by a luciferase assay. The expression of miR-205 and miR-338-3p were significantly downregulated in prostate carcinoma tissues and LNCaP cells when compared with normal controls. BCL2 expression was significantly inhibited by overexpression of miR-205 and miR-338-3p in LNCaP cells.

Conclusions

The results of this study showed that miR-205 and miR-338-3p downregulated the expression of the BCL2 gene and decreased apoptosis in prostate carcinoma.

Deregulation of Circular RNAs in Cancer From the Perspectives of Aberrant Biogenesis, Transport and Removal

CircRNAs (circular RNAs) are a class of RNAs generated from circularization with multiple novel functions. Recent studies have revealed the aberrant expression and aberrant functions of circRNAs in various tumors; thus, circRNAs have been recognized as promising cancer biomarkers. However, the underlying mechanisms behind their aberrant expression and functions remain unclear. In this review, we discuss at length the cancer-specific deregulation of circRNAs and the potential underlying aberrant events in circRNA biogenesis, localization and removal in cancer cells.

CircPCNXL2 sponges miR-153 to promote the proliferation and invasion of renal cancer cells through upregulating ZEB2

Increasing evidence showed that circular RNAs (circRNAs) play critical roles in tumorigenesis. However, the roles and underlying mechanisms of circRNAs in clear cell renal cell carcinoma (ccRCC) remain unclear. In the present study, we identified a novel circRNA circPCNXL2, which was significantly upregulated in ccRCC by circular RNA microarray. Further analysis revealed that circPCNXL2 was significantly increased and correlated with poor overall survival of ccRCC patients. Function assays revealed that circPCNXL2 knockdown reduced RCC cells proliferation, invasion in vitro, and decreased tumor growth in vivo. In mechanism study, we showed that circPCNXL2 could be bind to miR-153 as a miRNA sponge to regulate ZEB2 expression in RCC progression. In addition, our data reported that the effects of circPCNXL2 inhibition on RCC cells proliferation and invasion could be abolished by miR-153 inhibitors. Altogether, we demonstrated that circPCNXL2 could regulate RCC cells proliferation and invasion by miR-153/ZEB2 axis, suggesting circPCNXL2 might serve as a potential therapeutic target for ccRCC treatment.

RNAs as Candidate Diagnostic and Prognostic Markers of Prostate Cancer-From Cell Line Models to Liquid Biopsies

The treatment landscape of prostate cancer has evolved rapidly over the past five years. The explosion in treatment advances has been witnessed in parallel with significant progress in the field of molecular biomarkers. The advent of next-generation sequencing has enabled the molecular profiling of the genomic and transcriptomic architecture of prostate and other cancers. Coupled with this, is a renewed interest in the role of non-coding RNA (ncRNA) in prostate cancer biology. ncRNA consists of several different classes including small non-coding RNA (sncRNA), long non-coding RNA (lncRNA), and circular RNA (circRNA). These families are under active investigation, given their essential roles in cancer initiation, development and progression. This review focuses on the evidence for the role of RNAs in prostate cancer, and their use as diagnostic and prognostic markers, and targets for treatment in this disease.