The function and mechanisms of action of circular RNAs in Urologic Cancer

The novel circ_0004674/miR-139-5p/ZBTB2 regulatory cascade inhibits the development of oral squamous cell carcinoma

BACKGROUND

Circular RNAs (circRNAs) are an intriguing family of RNA molecules due to their crucial roles in the pathogenesis of oral squamous cell carcinoma (OSCC). Here, we sought to define the action of human circ_0004674 in OSCC progression.

METHODS

The functional role of circ_0004674 was validated by determining its effect on cell growth, apoptosis, and tube formation ability of OSCC cells. For protein quantification, a western blot or immunohistochemistry method was applied. The interaction between miR-139-5p and circ_0004674 or zinc finger and BTB domain containing 2 (ZBTB2) was predicted by online algorithms, and their relationships were confirmed by dual-luciferase reporter and RIP assays. Xenograft models were established to uncover circ_0004674's role in tumor growth.

RESULTS

Circ_0004674 expression was upregulated in OSCC. Functionally, knocking down circ_0004674 led to suppressed OSCC cell progression in vitro and delayed tumor growth in vivo. Mechanistically, circ_0004674 post-transcriptionally controlled ZBTB2 expression by competitively pairing to miR-139-5p. Furthermore, the deficiency of miR-139-5p abated circ_0004674 silencing-mediated OSCC cell progression repression, and augmentation of ZBTB2 reversed the anticancer effect of miR-139-5p on OSCC.

CONCLUSION

Our findings uncover a novel regulatory cascade, the circ_0004674/miR-139-5p/ZBTB2 axis, with the ability to affect OSCC development in vitro and in vivo, providing a potential opportunity for development of OSCC therapy.

Targeting LRP6: A new strategy for cancer therapy

Targeting specific molecular drivers of tumor growth is a key approach in cancer therapy. Among these targets, the low-density lipoprotein receptor-related protein 6 (LRP6), a vital component of the Wnt signaling pathway, has emerged as an intriguing candidate. As a cell-surface receptor and vital co-receptor, LRP6 is frequently overexpressed in various cancer types, implicating its pivotal role in driving tumor progression. The pursuit of LRP6 as a target for cancer treatment has gained substantial traction, offering a promising avenue for therapeutic intervention. Here, this comprehensive review explores recent breakthroughs in our understanding of LRP6's functions and underlying molecular mechanisms, providing a profound discussion of its involvement in cancer pathogenesis and drug resistance. Importantly, we go beyond discussing LRP6's role in cancer by discussing diverse potential therapeutic approaches targeting this enigmatic protein. These approaches encompass a wide spectrum, including pharmacological agents, natural compounds, non-coding RNAs, epigenetic factors, proteins, and peptides that modulate LRP6 expression or disrupt its interactions. In addition, also discussed the challenges associated with developing LRP6 inhibitors and their advantages over Wnt inhibitors, as well as the drugs that have entered phase II clinical trials. By shedding light on these innovative strategies, we aim to underscore LRP6's significance as a valuable and multifaceted target for cancer treatment, igniting enthusiasm for further research and facilitating translation into clinical applications.

CircNSD1 promotes cardiac fibrosis through targeting the miR-429-3p/SULF1/Wnt/β-catenin signaling pathway

Cardiac fibrosis is a detrimental pathological process, which constitutes the key factor for adverse cardiac structural remodeling leading to heart failure and other critical conditions. Circular RNAs (circRNAs) have emerged as important regulators of various cardiovascular diseases. It is known that several circRNAs regulate gene expression and pathological processes by binding miRNAs. In this study we investigated whether a novel circRNA, named circNSD1, and miR-429-3p formed an axis that controls cardiac fibrosis. We established a mouse model of myocardial infarction (MI) for in vivo studies and a cellular model of cardiac fibrogenesis in primary cultured mouse cardiac fibroblasts treated with TGF-β1. We showed that miR-429-3p was markedly downregulated in the cardiac fibrosis models. Through gain- and loss-of-function studies we confirmed miR-429-3p as a negative regulator of cardiac fibrosis. In searching for the upstream regulator of miR-429-3p, we identified circNSD1 that we subsequently demonstrated as an endogenous sponge of miR-429-3p. In MI mice, knockdown of circNSD1 alleviated cardiac fibrosis. Moreover, silence of human circNSD1 suppressed the proliferation and collagen production in human cardiac fibroblasts in vitro. We revealed that circNSD1 directly bound miR-429-3p, thereby upregulating SULF1 expression and activating the Wnt/β-catenin pathway. Collectively, circNSD1 may be a novel target for the treatment of cardiac fibrosis and associated cardiac disease.

Expression of circRNA-0036474 in esophageal cancer and its clinical significance

Circular RNAs are considered to play important roles in the progression of different cancers such as esophageal squamous cell carcinoma. However, the functions of circular RNAs in esophageal squamous cell carcinoma are still not clear. This study aimed to investigate the role and mechanism of circRNA-0036474 in the progression of esophageal squamous cell carcinoma. The hsa_circ_0036474 expression levels were found to be elevated in both EC109 cells and esophageal squamous cell carcinoma tissue samples. Moreover, knockdown of circRNA-0036474 expression in the EC109 cells induced migration and invasion, characterized by the down-regulation of E-cadherin, and up-regulation of N-cadherin and vimentin. In addition, the over-expressed hsa_circ_0036474 significantly decreased the activity of EC109 cells, elevated E-cadherin expression but declined N-cadherin and vimentin expression. Moreover, over-expressed mir-223-3p levels and interfered RERG expression verified the role of hsa_circ_0036474 in inhibiting the invasion and migration of EC109 cells, reducing the expression of N-cadherin and vimentin, and promoting the expression of E-cadherin. In conclusion, circRNA-0036474 mitigated the progression of esophageal squamous cell carcinoma through regulating mir-223-3p/RERG axis, presenting a potential therapeutic target for the treatment.

Riddle of the Sphinx: Emerging role of circular RNAs in cervical cancer

Cervical cancer is a prominent cause of cancer-related mortality among women, with recent attention directed toward exploring the involvement of circular RNAs (circRNAs) in this particular cancer. CircRNAs, characterized by a covalently closed loop structure, belong to a class of single-stranded non-coding RNA (ncRNA) molecules that play crucial roles in cancer development and progression through diverse mechanisms. The abnormal expression of circRNAs in vivo is significantly associated with the development of cervical cancer. Notably, circRNAs actively interact with miRNAs in cervical cancer, leading to the regulation of diverse signaling pathways, and they can contribute to cancer hallmarks such as self-sufficiency in growth signals, insensitivity to antigrowth signals, limitless proliferation, evading apoptosis, tissue invasion and metastasis, and sustained angiogenesis. Moreover, the distinctive biomedical attributes exhibited by circRNAs, including their abundance, conservation, and stability in body fluids, position them as promising biomarkers for various cancers. In this review, we elucidate the tremendous potential of circRNAs as diagnostic markers or therapeutic targets in cervical cancer by expounding upon their biogenesis, characteristics, functions, and databases, highlighting the novel advances in the signaling pathways associated with circRNAs in cervical cancer.

Circular STAG2 RNA Modulates Bladder Cancer Progression via miR-145-5p/TAGLN2 and Is Considered as a Biomarker for Recurrence

The current study aimed to elucidate the regulatory mechanisms of the circRNA hsa_circ_0139697 (circSTAG2(16-25)) in BCa and to consider the opportunity of using circSTAG2(16-25) isolated from BCa patient urine as a marker for disease development prediction. The selection of this circRNA was determined by the special role of its parental gene STAG2 in BCa biology. The circRNA hsa_circ_0139697 was chosen from 25 STAG2 circRNAs due to its differential expression in the urine of BCa patients and healthy volunteers. Higher levels of circSTAG2(16-25) were detected in urine samples obtained from patients with recurrent tumors. A higher expression of circSTAG2(16-25) was also detected in more tumorigenic BCa cell lines. The overexpression of circSTAG2(16-25) in BCa cells induced the elevation of proliferation, motility, and invasion. To study the mechanisms of circSTAG2(16-25) activity, we confirmed that circSTAG2(16-25) can bind miR-145-5p in vitro as was predicted by bioinformatic search. miR-145-5p was shown to suppress some genes that promoted BCa progression. One of these genes, TAGLN2, encodes the protein Transgelin 2, which plays a role in BCa cell motility and invasion. Therefore, the possible mechanism of action of circSTAG2(16-25) could be sponging the tumor suppressor miR-145-5p, which results in activation of TAGLN2. In addition, circSTAG2(16-25) might be considered as a potential biomarker for recurrence prediction.

Therapeutic importance and diagnostic function of circRNAs in urological cancers: from metastasis to drug resistance

Circular RNAs (circRNAs) are a member of non-coding RNAs with no ability in encoding proteins and their aberrant dysregulation is observed in cancers. Their closed-loop structure has increased their stability, and they are reliable biomarkers for cancer diagnosis. Urological cancers have been responsible for high mortality and morbidity worldwide, and developing new strategies in their treatment, especially based on gene therapy, is of importance since these malignant diseases do not respond to conventional therapies. In the current review, three important aims are followed. At the first step, the role of circRNAs in increasing or decreasing the progression of urological cancers is discussed, and the double-edged sword function of them is also highlighted. At the second step, the interaction of circRNAs with molecular targets responsible for urological cancer progression is discussed, and their impact on molecular processes such as apoptosis, autophagy, EMT, and MMPs is highlighted. Finally, the use of circRNAs as biomarkers in the diagnosis and prognosis of urological cancer patients is discussed to translate current findings in the clinic for better treatment of patients. Furthermore, since circRNAs can be transferred to tumor via exosomes and the interactions in tumor microenvironment provided by exosomes such as between macrophages and cancer cells is of importance in cancer progression, a separate section has been devoted to the role of exosomal circRNAs in urological tumors.

CircPPAP2B controls metastasis of clear cell renal cell carcinoma via HNRNPC-dependent alternative splicing and targeting the miR-182-5p/CYP1B1 axis

BACKGROUND

Renal cell carcinoma (RCC) is one of the most common malignant tumor worldwide. Metastasis is a leading case of cancer-related deaths of RCC. Circular RNAs (circRNAs), a class of noncoding RNAs, have emerged as important regulators in cancer metastasis. However, the functional effects and regulatory mechanisms of circRNAs on RCC metastasis remain largely unknown.

METHODS

High-throughput RNA sequencing techniques were performed to analyze the expression profiles of circRNAs and mRNAs in highly and poorly invasive clear cell renal cell carcinoma (ccRCC) cell lines. Functional experiments were performed to unveil the regulatory role of circPPAP2B in the proliferation and metastatic capabilities of ccRCC cells. RNA pulldown, Mass spectrometry analysis, RNA methylation immunoprecipitation (MeRIP), RNA immunoprecipitation (RIP), co-immunoprecipitation (CoIP), next-generation RNA-sequencing and double luciferase experiments were employed to clarify the molecular mechanisms by which circPPAP2B promotes ccRCC metastasis.

RESULTS

In this study, we describe a newly identified circular RNA called circPPAP2B, which is overexpressed in highly invasive ccRCC cells, as determined through advanced high-throughput RNA sequencing techniques. Furthermore, we observed elevated circPPAP2B in ccRCC tissues, particularly in metastatic ccRCC tissues, and found it to be associated with poor prognosis. Functional experiments unveiled that circPPAP2B actively stimulates the proliferation and metastatic capabilities of ccRCC cells. Mechanistically, circPPAP2B interacts with HNRNPC in a m6A-dependent manner to facilitate HNRNPC nuclear translocation. Subcellular relocalization was dependent upon nondegradable ubiquitination of HNRNPC and stabilization of an HNRNPC/Vimentin/Importin α7 ternary complex. Moreover, we found that circPPAP2B modulates the interaction between HNRNPC and splicing factors, PTBP1 and HNPNPK, and regulates pre-mRNA alternative splicing. Finally, our studies demonstrate that circPPAP2B functions as a miRNA sponge to directly bind to miR-182-5p and increase CYP1B1 expression in ccRCC.

CONCLUSIONS

Collectively, our study provides comprehensive evidence that circPPAP2B promotes proliferation and metastasis of ccRCC via HNRNPC-dependent alternative splicing and miR-182-5p/CYP1B1 axis and highlights circPPAP2B as a potential therapeutic target for ccRCC intervention.

CircTENM3 inhibites tumor progression via the miR-558/RUNX3 axis in prostate cancer

BACKGROUND

Prostate cancer (PCa) is currently acknowledged as the second most widespread cancer among men worldwide. Yet, the lack of dependable diagnostic biomarkers and therapeutic targets has presented considerable hurdles to the progression of prostate cancer treatment. Circular RNAs are implicated in the pathogenesis of numerous diseases, positioning them as promising biomarkers for diverse medical conditions. This study aims to uncover a specific circRNA that could serve as a diagnostic and therapeutic target for detecting and treating PCa.

METHODS

The change of circTENM3 expression levels in PCa was detected by qPCR. CCK8 assays, EdU assays, Scratch assay and Transwell migration assay conducted to detect the role of circTENM3 in PCa cells in vitro. RIP assay, RNA-pull down and luciferase reporter assay were performed to explore the mechanism of circTENM3. Gain-of-function analysis was performed to reveal the function of circTENM3 in PCa in vivo.

RESULTS

The results revealed that the expression level of circTENM3 was significantly down-regulated in PCa. CircTENM3 overexpression alleviated the progression of PCa in vitro. Mechanistically, circTENM3 enhanced RUNX3 levels via miR-558 sponge. Gain-of-function analysis determined that circTENM3 overexpression could inhibit PCa progression in vitro.

CONCLUSIONS

Our research offers profound insights into the protective role played by circTENM3 in PCa. CircTENM3 operates as a sponge for miR-558, thereby triggering the elevation of RUNX3 expression, which subsequently curbs the progression of PCa.

Circular RNAs in renal cell carcinoma: from mechanistic to clinical perspective

CircRNAs, a special type of noncoding RNAs characterized by their stable structure and unique abilities to form backsplicing loops, have recently attracted the interest of scientists. These RNAs are abundant throughout the body and play important roles such as microRNA sponges, templates for transcription, and regulation of protein translation and RNA-binding proteins. Renal cancer development is highly correlated with abnormal circRNA expression in vivo. CircRNAs are currently considered promising targets for novel therapeutic approaches as well as possible biomarkers for prognosis and diagnosis of various malignancies. Despite our growing understanding of circRNA, numerous questions remain unanswered. Here, we address the characteristics of circRNAs and their function, focusing in particular on their impact on drug resistance, metabolic processes, metastasis, cell growth, and programmed cell death in renal cancer. In addition, the application of circRNAs as prognostic and diagnostic biomarkers will be discussed.

Role of The circ-HIPK3, circ-PVT1, miR-25, and miR-149 in Response of Breast Cancer Cells to Ionizing Radiation

OBJECTIVE

Determining cellular radiosensitivity of breast cancer (BC) patients through molecular markers before radiation therapy (RT) allows accurate prediction of individual's response to radiation. The aim of this study was therefore to investigate the potential role of epigenetic biomarkers in breast cancer cellular radiosensitivity.

MATERIALS AND METHODS

In this experimental study, we treated two BC cell lines, MDA-MB 231 and MCF-7, with doses of 2, 4, and 8Gy of irradiation for 24 and 48 hours. Expression levels of circ-HIPK3, circ-PVT1, miR-25, and miR- 149 were quantified using quantitative reverse-transcription polymerase chain reaction (qRT-PCR). Significance of the observations was statistically verified using one-way ANOVA with a significance level of P<0.05. Annexin V-FITC/PI binding assay was utilized to measure cellular apoptosis.

RESULTS

The rate of cell apoptosis was significantly higher in MCF-7 cells compared to MDA-MB-231 cells at doses of 4Gy and 8Gy (P=0.013 and P=0.004, respectively). RNA expression analysis showed that circ-HIPK3 was increased in the MDA-MB-231 cell line compared to the MCF-7 cell line after exposure to 8Gy for 48 hours. Expression of circ-PVT1 was found to be higher in MDA-MB-231 cells compared to MCF-7 cells after exposure to 8Gy for 24 hours, likewise after exposure to 4Gy and 8Gy for 48 hours. After exposing 8Gy, expression of miR-25 was increased in MDA-MB-231 cells compared to MCF-7 cells at 24 and 48 hours. After exposing 8Gy dose, expression of miR-149 was increased in MCF-7 cells compared to MDA-MB-231 cells at 24 and 48 hours.

CONCLUSION

circ-HIPK3, circ-PVT1, and miR-25 played crucial roles in the mechanisms of radioresistance in breast cancer. Additionally, miR-149 was involved in regulating cellular radiosensitivity. Therefore, these factors provided predictive information about a tumor's radiosensitivity or its response to treatment, which could be valuable in personalizing radiation dosage.

Non-coding RNAs in renal cell carcinoma: Implications for drug resistance

Renal cell carcinoma (RCC) represents a malignant tumor of the urinary system. Individuals with early-stage RCC could be cured by surgical treatment, but a considerable number of cases of advanced RCC progress to drug resistance. Recently, numerous reports have demonstrated that a variety of non-coding RNAs (ncRNAs) contribute to tumor occurrence and development. ncRNAs can act as oncogenic or tumor suppressor genes to regulate proliferation, migration, drug resistance and other processes in RCC cells through a variety of signaling pathways. Considering the lack of treatment options for advanced RCC after drug resistance, ncRNAs may be a good choice as biomarkers of drug resistance in RCC and targets to overcome drug resistance. In this review, we discussed the effects of ncRNAs on drug resistance in RCC and the great potential of ncRNAs as a biomarker of or a new therapeutic method in RCC.

The role of E3 ubiquitin ligases and deubiquitinases in bladder cancer development and immunotherapy

Bladder cancer is one of the common malignant urothelial tumors. Post-translational modification (PTMs), including ubiquitination, acetylation, methylation, and phosphorylation, have been revealed to participate in bladder cancer initiation and progression. Ubiquitination is the common PTM, which is conducted by E1 ubiquitin-activating enzyme, E2 ubiquitin-conjugating enzyme and E3 ubiquitin-protein ligase. E3 ubiquitin ligases play a key role in bladder oncogenesis and progression and drug resistance in bladder cancer. Therefore, in this review, we summarize current knowledge regarding the functions of E3 ubiquitin ligases in bladder cancer development. Moreover, we provide the evidence of E3 ubiquitin ligases in regulation of immunotherapy in bladder cancer. Furthermore, we mention the multiple compounds that target E3 ubiquitin ligases to improve the therapy efficacy of bladder cancer. We hope our review can stimulate researchers and clinicians to investigate whether and how targeting E3 ubiquitin ligases acts a novel strategy for bladder cancer therapy.

Epigenetic programing of cancer stemness by transcription factors-non-coding RNAs interactions

Cancer 'stemness' is fundamental to cancer existence. It defines the ability of cancer cells to indefinitely perpetuate as well as differentiate. Cancer stem cell populations within a growing tumor also help evade the inhibitory effects of chemo- as well as radiation-therapies, in addition to playing an important role in cancer metastases. NF-κB and STAT-3 are representative transcription factors (TFs) that have long been associated with cancer stemness, thus presenting as attractive targets for cancer therapy. The growing interest in non-coding RNAs (ncRNAs) in the recent years has provided further insight into the mechanisms by which TFs influence cancer stem cell characteristics. There is evidence for a direct regulation of TFs by ncRNAs, such as, microRNAs (miRNAs), long non-coding RNAs (lncRNAs) as well as circular RNAs (circRNAs), and vice versa. Additionally, the TF-ncRNAs regulations are often indirect, involving ncRNA-target genes or the sponging of other ncRNA species by individual ncRNAs. The information is rapidly evolving and this review provides a comprehensive review of TF-ncRNAs interactions with implications on cancer stemness and in response to therapies. Such knowledge will help uncover the many levels of tight regulations that control cancer stemness, providing novel opportunities and targets for therapy in the process.