Hsa_circ_001680 affects the proliferation and migration of CRC and mediates its chemoresistance by regulating BMI1 through miR-340

Examining the evidence for mutual modulation between m6A modification and circular RNAs: current knowledge and future prospects

The resistance of cancer cells to treatment significantly impedes the success of therapy, leading to the recurrence of various types of cancers. Understanding the specific mechanisms of therapy resistance may offer novel approaches for alleviating drug resistance in cancer. Recent research has shown a reciprocal relationship between circular RNAs (circRNAs) and N6-methyladenosine (m6A) modification, and their interaction can affect the resistance and sensitivity of cancer therapy. This review aims to summarize the latest developments in the m6A modification of circRNAs and their importance in regulating therapy resistance in cancer. Furthermore, we explore their mutual interaction and exact mechanisms and provide insights into potential future approaches for reversing cancer resistance.

Regulatory feedback loop between circ-EIF4A3 and EIF4A3 Enhances autophagy and growth in colorectal cancer cells

Recent studies indicate that circular RNAs (circRNAs) are crucial in the progression of colorectal cancer (CRC). Eukaryotic translation initiation factor 4A3 (EIF4A3) has been identified as a promoter of circRNA production. The biological roles and mechanisms of EIF4A3-derived circRNA (circEIF4A3) in CRC cell autophagy remain poorly understood. This study explores the effects of circEIF4A3 on CRC cell growth and autophagy, aiming to elucidate the underlying molecular mechanisms. We discovered that EIF4A3 and circEIF4A3 synergistically enhance CRC cell growth. CircEIF4A3 sequesters miR-3126-5p, consequently upregulating EIF4A3. Further, circEIF4A3 increases EIF4A3 expression, which promotes autophagy by stabilizing ATG5 mRNA and enhances ATG7 protein stability through the stabilization of USP14 mRNA, a deubiquitinating enzyme. Upregulation of ATG5 and ATG7 counteracts the growth-inhibitory effects of EIF4A3 knockdown on CRC cells. Moreover, our findings demonstrate that EIF4A3 induces the formation of circEIF4A3 in CRC cells. In conclusion, a positive feedback loop between circEIF4A3 and EIF4A3 supports CRC cell growth by facilitating autophagy.

Advanced strategies of targeting circular RNAs as therapeutic approaches in colorectal cancer drug resistance

Colorectal cancer (CRC) stands second in terms of mortality and third among the highest prevalent kinds of cancer globally. CRC prevalence is rising in moderately and poorly developed regions and is greater in economically advanced regions. Despite breakthroughs in targeted therapy, resistance to chemotherapeutics remains a significant challenge in the long-term management of CRC. Circular RNAs (circRNAs) have been involved in growing cancer therapy resistance, particularly in CRC, according to an increasing number of studies in recent years. CircRNAs are one of the novel subclasses of non-coding RNAs, previously thought of as viroid. According to studies, circRNAs have been recommended as biological markers for therapeutic targets and diagnostic and prognostic purposes. That is particularly notable given that the expression of circRNAs has been linked to the hallmarks of CRC since they are responsible for drug resistance in CRC patients; thereby, circRNAs are significant for chemotherapy failure. Moreover, knowledge concerning circRNAs remains relatively unclear despite using all these advanced techniques. Here, in this study, we will go over the most recent published work to highlight the critical roles of circRNAs in CRC development and drug resistance and highlight the main strategies to overcome drug resistance to improve clinical outcomes.

New insights into the potential of exosomal circular RNAs in mediating cancer chemotherapy resistance and their clinical applications

Chemotherapy resistance typically leads to tumour recurrence and is a major obstacle to cancer treatment. Increasing numbers of circular RNAs (circRNAs) have been confirmed to be abnormally expressed in various tumours, where they participate in the malignant progression of tumours, and play important roles in regulating the sensitivity of tumours to chemotherapy drugs. As exosomes mediate intercellular communication, they are rich in circRNAs and exhibit a specific RNA cargo sorting mechanism. By carrying and delivering circRNAs, exosomes can promote the efflux of chemotherapeutic drugs and reduce intracellular drug concentrations in recipient cells, thus affecting the cell cycle, apoptosis, autophagy, angiogenesis, invasion and migration. The mechanisms that affect the phenotype of tumour stem cells, epithelial-mesenchymal transformation and DNA damage repair also mediate chemotherapy resistance in many tumours. Exosomal circRNAs are diagnostic biomarkers and potential therapeutic targets for reversing chemotherapy resistance in tumours. Currently, the rise of new fields, such as machine learning and artificial intelligence, and new technologies such as biosensors, multimolecular diagnostic systems and platforms based on circRNAs, as well as the application of exosome-based vaccines, has provided novel ideas for precision cancer treatment. In this review, the recent progress in understanding how exosomal circRNAs mediate tumour chemotherapy resistance is reviewed, and the potential of exosomal circRNAs in tumour diagnosis, treatment and immune regulation is discussed, providing new ideas for inhibiting tumour chemotherapy resistance.

Targeting Hepatic Cancer Stem Cells (CSCs) and Related Drug Resistance by Small Interfering RNA (siRNA)

Tumor recurrence after curative therapy and hepatocellular carcinoma (HCC) cells' resistance to conventional therapies is the reasons for the worse clinical results of HCC patients. A tiny population of cancer cells with a strong potential for self-renewal, differentiation, and tumorigenesis has been identified as cancer stem cells (CSCs). The discovery of CSC surface markers and the separation of CSC subpopulations from HCC cells have been made possible by recent developments in the study of hepatic (liver) CSCs. Hepatic CSC surface markers include epithelial cell adhesion molecules (EpCAM), CD133, CD90, CD13, CD44, OV-6, ALDH, and K19. CSCs have a significant influence on the development of cancer, invasiveness, self-renewal, metastasis, and drug resistance in HCC, and thus provide a therapeutic chance to treat HCC and avoid its recurrence. Therefore, it is essential to develop treatment approaches that specifically and effectively target hepatic stem cells. Given this, one potential treatment approach is to use particular small interfering RNA (siRNA) to target CSC, disrupting their behavior and microenvironment as well as changing their epigenetic state. The characteristics of CSCs in HCC are outlined in this study, along with new treatment approaches based on siRNA that may be used to target hepatic CSCs and overcome HCC resistance to traditional therapies.

Role of Non-coding RNAs in the Response of Glioblastoma to Temozolomide

Chemotherapy and radiotherapy are widely used in clinical practice across the globe as cancer treatments. Intrinsic or acquired chemoresistance poses a significant problem for medical practitioners and researchers, causing tumor recurrence and metastasis. The most dangerous kind of malignant brain tumor is called glioblastoma multiforme (GBM) that often recurs following surgery. The most often used medication for treating GBM is temozolomide chemotherapy; however, most patients eventually become resistant. Researchers are studying preclinical models that accurately reflect human disease and can be used to speed up drug development to overcome chemoresistance in GBM. Non-coding RNAs (ncRNAs) have been shown to be substantial in regulating tumor development and facilitating treatment resistance in several cancers, such as GBM. In this work, we mentioned the mechanisms of how different ncRNAs (microRNAs, long non-coding RNAs, circular RNAs) can regulate temozolomide chemosensitivity in GBM. We also address the role of these ncRNAs encapsulated inside secreted exosomes.

Circular RNA circ_0058123 Targets the miR-939-5p/RAC1 Pathway to Promote the Development of Colorectal Cancer

Circular RNA (circRNA) can be used as a potential target for cancer treatment. However, the biological function and potential molecular mechanism of circ_0058123 in the development of colorectal cancer (CRC) are still unclear. The expression levels of circ_0058123, microRNA-939-5p (miR-939-5p) and Rac family small GTPase 1 (RAC1) were measured by quantitative real-time polymerase chain reaction or western blot assay. 5-Ethynyl-2'-deoxyuridine (EdU) incorporation assay, transwell assay, tube formation assay and flow cytometry apoptosis assay were conducted to assess CRC cell functions. In addition, protein expression was measured with western blot assay. Dual-luciferase reporter assays and RNA immunoprecipitation assay were conducted to confirm the relationships between miR-939-5p and circ_0058123, and miR-939-5p and RAC1. In vivo CRC tumor growth experiment also were carried out to determine circ_0058123-mediatede effects on tumor formation. Our data showed that circ_0058123 and RAC1 expression were increased, but miR-939-5p was decreased in both of CRC tissues and cell lines. Circ_0058123 depletion repressed CRC cell proliferation, migration, invasion and tube formation but promoted cell apoptosis. Down-regulation of circ_0058123 could significantly suppress the CRC progression, while the addition of miR-939-5p inhibitor could reverse this effect. Circ_0058123 directly targeted miR-939-5p, and RAC1 was a target of miR-939-5p. Furthermore, RAC1 overexpression could rescue the effect of miR-939-5p on CRC development. Lastly, silence of circ_0058123 inhibited CRC tumor growth in vivo. In conclusion, circ_0058123 could promote CRC progression through regulating the miR-939-5p/RAC1 axis and may be a valuable biomarker for early diagnosis and prognosis of CRC.

MicroR-380-3p Reduces Sepsis-Induced Acute Kidney Injury via Regulating RAB1P to Restrain NF-κB Pathway

Septic acute kidney injury (AKI) is a common complication in critically ill patients with high morbidity and mortality. This study intends to clarify the clinical value and molecular mechanism of microR-380-3p in septic AKI by recruiting patients with septic AKI and establishing septic AKI cell models. Patients with septic AKI were included and human kidney-2 (HK-2) cells were induced by lipopolysaccharide (LPS) to construct the AKI cell model of sepsis. The expression of microR-380-3p was detected by quantitative real-time RT-PCR (qRT-PCR). The expression of Bax, cleaved caspase 3, Bcl-2, p65, and p-p65 was detected by Western blot. The contents of inflammation and oxidation were determined by commercial kits. Bioinformatics predicted the binding target of microR-380-3p and a dual luciferase reporting system was used to verify the regulatory relationship between microR-380-3p and RAP1B. The concentration of microR-380-3p was elevated in patients with septic AKI and appeared to be a biomarker for these patients. Silenced microR-380-3p reversed the damage of LPS on HK-2 cells via promoting viability, inhibiting apoptosis, inflammation, and oxidation. RAP1B was a target of microR-380-3p and microR-380-3p exerted targeted inhibition of RAP1B expression level. Down-regulation of RAP1B reversed the influence of silenced microR-380-3p on HK-2 cells. MicroR-380-3p/RAP1B participated in activating the NF-κB pathway. MicroR-380-3p down-regulated RAP1B to exacerbate septic AKI, providing a potential therapeutic biomarker for septic AKI.

Circ-0075305 hinders gastric cancer stem cells by indirectly disrupting TCF4-β-catenin complex and downregulation of SOX9

CircRNAs are covalently closed, single-stranded RNA that form continuous loops and play a crucial role in the initiation and progression of tumors. Cancer stem cells (CSCs) are indispensable for cancer development; however, the regulation of cancer stem cell-like properties in gastric cancer (GC) and its specific mechanism remain poorly understood. We elucidate the specific role of Circ-0075305 in GC stem cell properties. Circ-0075305 associated with chemotherapy resistance was identified by sequencing GC cells. Subsequent confirmation in both GC tissues and cell lines revealed that patients with high expression of Circ-0075305 had significantly better overall survival (OS) rates than those with low expression, particularly when treated with postoperative adjuvant chemotherapy for GC. In vitro and in vivo experiments confirmed that overexpression of Circ-0075305 can effectively reduce stem cell-like properties and enhance the sensitivity of GC cells to Oxaliplatin compared with the control group. Circ-0075305 promotes RPRD1A expression by acting as a sponge for corresponding miRNAs. The addition of LF3 (a β-catenin/TCF4 interaction antagonist) confirmed that RPRD1A inhibited the formation of the TCF4-β-catenin transcription complex through competitive to β-catenin and suppressed the transcriptional activity of stem cell markers such as SOX9 via the Wnt/β-catenin signaling pathway. This leads to the downregulation of stem cell-like property-related markers in GC. This study revealed the underlying mechanisms that regulate Circ-0075305 in GCSCs and suggests that its role in reducing β-catenin signaling may serve as a potential therapeutic candidate.

CircAGFG1 absence decreases PKM2 expression to enhance oxaliplatin sensitivity in colorectal cancer in a miR-7-5p-dependent manner

Circular RNA (circRNA) ArfGAP with FG repeats 1 (circAGFG1) contributes to colorectal cancer (CRC) development. However, whether circAGFG1 regulates the resistance of CRC to oxaliplatin (L-OHP) remains unknown. CircAGFG1, microRNA-7-5p (miR-7-5p) and pyruvate kinase M2 (PKM2) RNA expression were quantified by quantitative real-time polymerase chain reaction. Protein expression was detected by western blot assay and immunohistochemistry assay. Glycolysis was analyzed through glucose uptake, lactate production and adenosine triphosphate (ATP) concentration assays. 50% inhibitory concentration of L-OHP was determined by cell counting kit-8 assay. Cell proliferation and apoptotic rate were analyzed by cell colony formation and flow cytometry analysis, respectively. Dual-luciferase reporter assay was used to identify the relationship among circAGFG1, miR-7- 5p and PKM2. The effect of circAGFG1 on L-OHP sensitivity in vivo was further evaluated by a xenograft model assay. CircAGFG1 and PKM2 expression were significantly increased, while miR-7-5p was decreased in L-OHP-resistant CRC tissues and cells. High circAGFG1 expression predicted a poor prognosis of CRC. CircAGFG1 knockdown or PKM2 depletion decreased glycolysis and cell proliferation and increased L-OHP sensitivity and cell apoptosis. PKM2 introduction rescued circAGFG1 silencing-induced effects in CRC cells. In terms of mechanism, circAGFG1 bound to miR-7-5p, which was identified to target PKM2. Also, circAGFG1 regulated PKM2 expression by interacting with miR-7-5p. Further, circAGFG1 knockdown improved the sensitivity of tumors to L-OHP in vivo. CircAGFG1 depletion inhibited L-OHP resistance by regulating the miR-7-5p/PKM2 pathway.

Deciphering the impact of circRNA-mediated autophagy on tumor therapeutic resistance: a novel perspective

Cancer therapeutic resistance remains a significant challenge in the pursuit of effective treatment strategies. Circular RNAs (circRNAs), a class of non-coding RNAs, have recently emerged as key regulators of various biological processes, including cancer progression and drug resistance. This review highlights the emerging role of circRNAs-mediated autophagy in cancer therapeutic resistance, a cellular process that plays a dual role in cancer by promoting both cell survival and death. Increasing evidence suggests that circRNAs can modulate autophagy pathways, thereby influencing the response of cancer cells to therapeutic agents. In this context, the intricate interplay between circRNAs, autophagy, and therapeutic resistance is explored. Various mechanisms are discussed through which circRNAs can impact autophagy, including direct interactions with autophagy-related genes, modulation of signaling pathways, and cross-talk with other non-coding RNAs. Furthermore, the review delves into specific examples of how circRNA-mediated autophagy regulation can contribute to resistance against chemotherapy and radiotherapy. Understanding these intricate molecular interactions provides valuable insights into potential strategies for overcoming therapeutic resistance in cancer. Exploiting circRNAs as therapeutic targets or utilizing them as diagnostic and predictive biomarkers opens new avenues for developing personalized treatment approaches. In summary, this review underscores the importance of circRNA-mediated autophagy in cancer therapeutic resistance and proposes future directions for research in this exciting and rapidly evolving field.

Transcriptional regulation of cancer stem cell: regulatory factors elucidation and cancer treatment strategies

Cancer stem cells (CSCs) were first discovered in the 1990s, revealing the mysteries of cancer origin, migration, recurrence and drug-resistance from a new perspective. The expression of pluripotent genes and complex signal regulatory networks are significant features of CSC, also act as core factors to affect the characteristics of CSC. Transcription is a necessary link to regulate the phenotype and potential of CSC, involving chromatin environment, nucleosome occupancy, histone modification, transcription factor (TF) availability and cis-regulatory elements, which suffer from ambient pressure. Especially, the expression and activity of pluripotent TFs are deeply affected by both internal and external factors, which is the foundation of CSC transcriptional regulation in the current research framework. Growing evidence indicates that regulating epigenetic modifications to alter cancer stemness is effective, and some special promoters and enhancers can serve as targets to influence the properties of CSC. Clarifying the factors that regulate CSC transcription will assist us directly target key stem genes and TFs, or hinder CSC transcription through environmental and other related factors, in order to achieve the goal of inhibiting CSC and tumors. This paper comprehensively reviews the traditional aspects of transcriptional regulation, and explores the progress and insights of the impact on CSC transcription and status through tumor microenvironment (TME), hypoxia, metabolism and new meaningful regulatory factors in conjunction with the latest research. Finally, we present opinions on omnidirectional targeting CSCs transcription to eliminate CSCs and address tumor resistance.

Competitive endogenous RNA networks: Decoding the role of long non-coding RNAs and circular RNAs in colorectal cancer chemoresistance

Colorectal cancer (CRC) is recognized as one of the most common gastrointestinal malignancies across the globe. Despite significant progress in designing novel treatments for CRC, there is a pressing need for more effective therapeutic approaches. Unfortunately, many patients undergoing chemotherapy develop drug resistance, posing a significant challenge for cancer treatment. Non-coding RNAs (ncRNAs) have been found to play crucial roles in CRC development and its response to chemotherapy. However, there are still gaps in our understanding of interactions among various ncRNAs, such as long non-coding RNAs (lncRNAs), circular RNAs (circRNAs) and microRNAs (miRNAs). These ncRNAs can act as either oncogenes or tumour suppressors, affecting numerous biological functions in different cancers including CRC. A class of ncRNA molecules known as competitive endogenous RNAs (ceRNAs) has emerged as a key player in various cellular processes. These molecules form networks through lncRNA/miRNA/mRNA and circRNA/miRNA/mRNA interactions. In CRC, dysregulation of ceRNA networks has been observed across various cellular processes, including proliferation, apoptosis and angiogenesis. These dysregulations are believed to play a significant role in the progression of CRC and, in certain instances, may contribute to the development of chemoresistance. Enriching our knowledge of these dysregulations holds promise for advancing the field of diagnostic and therapeutic modalities for CRC. In this review, we discuss lncRNA- and circRNA-associated ceRNA networks implicated in the emergence and advancement of drug resistance in colorectal carcinogenesis.

Circ_0007422 Knockdown Inhibits Tumor Property and Immune Escape of Colorectal Cancer by Decreasing PDL1 Expression in a miR-1256-Dependent Manner

Circular RNAs (circRNAs) are a group of important molecules involved in the progression of various cancers, including colorectal cancer (CRC). Here, we aim to investigate the role and molecular mechanism of circ_0007422 in regulating CRC malignant progression. The expression levels of circ_0007422, miR-1256, and PDL1 were detected by qRT-PCR. Cell viability, proliferation, apoptosis, invasion, and self-replication ability were analyzed by CCK-8, EdU, flow cytometry, transwell, and spheroid formation experiments, respectively. Protein levels were determined by western blotting assay. CRC cells were co-cultured with CD8 + T cells, phytohemagglutinin-stimulated peripheral blood mononuclear cells (PBMCs), or cytokine-induced killer (CIK) cells in vitro, and CD8 + T-cell apoptosis, IFN-γ and TNF-α levels, and survival rate of CRC cells were analyzed to reveal the role of circ_0007422 in antitumor immunity. The relationship between miR-1256 and circ_0007422 or PDL1 was identified by a dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay. A xenograft tumor model was established to verify the function of circ_0007422 in tumor growth in vivo. Immunohistochemistry (IHC) assay was used to detect positive expression rates of Ki67, E-cadherin, N-cadherin, and PDL1 expression in primary tumors from CRC cells. Circ_0007422 was upregulated in CRC tissues and cells and its knockdown inhibited proliferation, invasion, self-replication ability, and immune escape and promoted apoptosis of CRC cells. Additionally, circ_0007422 bound to miR-1256, which was identified to target PDL1. MiR-1256 inhibition reversed the effects of circ_0007422 knockdown on the tumor properties and immune escape of CRC cells. Moreover, miR-1256 introduction interacted with PDL1 to suppress proliferation, invasion, self-replication ability, and immune escape and promote apoptosis of CRC cells. Further, circ_0007422 knockdown hampered tumorigenesis of CRC cells in vivo. Circ_0007422 knockdown inhibited tumor property and immune escape of colorectal cancer through the miR-1256/PDL1 pathway, providing a potential novel therapeutic target for CRC.

CircPOFUT1 fosters colorectal cancer metastasis and chemoresistance via decoying miR-653-5p/E2F7/WDR66 axis and stabilizing BMI1

CircRNAs are implicated in colorectal cancer (CRC) development and progression. Protein O-fucosyltransferase 1 (POFUT1) plays an oncogenic role via activating Notch1 signaling in CRC. However, the roles of circPOFUT1, which is originated from POFUT1, have not been investigated. Our study showed circPOFUT1 was highly expressed in CRC tissues and cells. CircPOFUT1 enhanced the proliferation, migration and invasion of CRC cells, and promoted tumor growth and liver metastasis in vivo. It also reinforced stemness and chemoresistance of CRC cells. Mechanistically, circPOFUT1 regulated the function of E2F7 via sponging miR-653-5p, thereby transcriptionally inducing WDR66 expression and further promoting metastasis in CRC. On the other hand, circPOFUT1 promoted stemness and chemoresistance of CRC cells via stabilizing BMI1 in an IGF2BP1-dependent manner. In conclusion, circPOFUT1 fosters CRC metastasis and chemoresistance via decoying miR-653-5p/E2F7/WDR66 axis and stabilizing BMI1.

circPPP2R4 promotes colorectal cancer progression and reduces ROS production through the miR-646/FOXK1 axis

Circular RNAs (circRNAs) play important roles in colorectal cancer (CRC) development and progression. This study aimed to investigate the function and molecular mechanism of circPPP2R4 in CRC. Based on bioinformatic analyses and validation by qRT-PCR, we identified a novel circRNA, circPPP2R4, which was upregulated in CRC tissues. Receiver operating characteristic curve analysis implied a high diagnostic value of circPPP2R4 for CRC. Additionally, high circPPP2R4 levels were positively correlated with advanced clinical stage and lymph node metastasis. Functionally, circPPP2R4 overexpression facilitated CRC cells proliferation, migration and invasion, whereas circPPP2R4 knockdown attenuated the malignant behaviors. In mouse models, circPPP2R4 overexpression remarkably promoted tumor growth and lung metastasis. Mechanistically, a series of experiments containing RIP, RNA pull-down, and dual-luciferase reporter assays revealed the circPPP2R4/miR-646/FOXK1 axis in CRC. Further experiments were conducted to verify that circPPP2R4 reduced reactive oxygen species generation to exert its oncogenic function by sponging miR-646 to upregulate FOXK1 expression. For the first time, we identified the regulatory role of circPPP2R4 in CRC pathogenesis, providing a potential diagnostic biomarker and therapeutic strategy for CRC.

Exosomal non-coding RNAs: Blueprint in colorectal cancer metastasis and therapeutic targets

Colorectal cancer (CRC) is ranked as the world's third-most prevalent cancer, and metastatic CRC considerably increases cancer-related fatalities globally. A number of complex mechanisms that are strictly controlled at the molecular level are involved in metastasis, which is the primary reason for death in people with CRC. Recently, it has become clear that exosomes, which are small extracellular vesicles released by non-tumorous and tumorigenic cells, play a critical role as communication mediators among tumor microenvironment (TME). To facilitate communication between the TME and cancer cells, non-coding RNAs (ncRNAs) play a crucial role and are recognized as potent regulators of gene expression and cellular processes, such as metastasis and drug resistance. NcRNAs are now recognized as potent regulators of gene expression and many hallmarks of cancer, including metastasis. Exosomal ncRNAs, like miRNAs, circRNAs, and lncRNAs, have been demonstrated to influence a number of cellular mechanisms that contribute to CRC metastasis. However, the molecular mechanisms that link exosomal ncRNAs with CRC metastasis are not well understood. This review highlights the essential roles that exosomal ncRNAs play in the progression of CRC metastatic disease and explores the therapeutic choices that are open to patients who have CRC metastases. However, exosomal ncRNA treatment strategy development is still in its early phases; consequently, additional investigation is required to improve delivery methods and find novel therapeutic targets as well as confirm the effectiveness and safety of these therapies in preclinical and clinical contexts.

Has_circ_0071803 promotes colorectal cancer progression by regulating miR-330-5p/MAPK signaling pathway

Colorectal cancer (CRC) is the third most commonly diagnosed cancer worldwide. A lack of effective targeted therapies against CRC makes the treatment challenging. Here, we report a circular RNA (circRNA), has_circ_0071803, functioning as an oncogene in CRC. Circ_0071803 was upregulated in CRC tissues and cell lines, and its expression levels were inversely correlated with the prognosis and survival rate of patients with CRC. Circ_0071803 knockdown suppressed cell proliferation, migration, and invasion in CRC. Moreover, we found that circ_0071803 sponged miR-330-5p, thereby upregulating mitogen-activated protein kinase 1 (MAPK1) in CRC cells. The suppression of cell activities by circ_0071803 knockdown were rescued by miR-330-5p inhibition or MAPK1 overexpression. Collectively, our findings elucidate that circ_0071803 promotes CRC progression by regulating the miR-330-5p/MAPK1 pathway, providing potential therapeutic targets for designing effective targeted treatments.

Association between insulin resistance related indicators with the prognosis of patients with colorectal cancer

BACKGROUND

The progression of colorectal cancer (CRC) has been linked to metabolism alteration. Because insulin resistance (IR) is the basic mechanism of metabolism alteration, IR related indicators are considered to be associated with prognostic of CRC. In this study, we compared the prognostic values of common IR related indicators for CRC and selected the best one. Moreover, we explored the association between that indicator and CRC prognosis and possible interactive covariates.

METHODS

Medical records of patients with CRC (n = 1765) were retrieved from the Investigation on Nutrition Status and Clinical Outcome of Common Cancers (INSCOC) study. We compared the prognostic values of IR related indicators and select the best one using concordance index (C-index) and area under curve (AUC). Using Cox proportional hazard regression models, we evaluated the association between that indicator and CRC prognosis. Interaction tests were performed to evaluate possible interactions among covariates and the IR related indicator.

RESULTS

Results of C-index and AUC indicated that the ratio of low-density lipoprotein-to-high-density lipoprotein (LHR) showed the highest ability to predict the prognosis of patients with CRC. LHR independently predicted CRC prognosis [hazard ratio (HR) = 1.14; 95 % confidence interval (CI) = 1.05-1.22; P = 0.001]. The interactions between LHR, and age (<65 vs. ≥65; P for interaction = 0.001) or neutrocyte-to-lymphocyte ratio (NLR) (<3 vs. ≥3; P for interaction = 0.055) were also observed.

CONCLUSION

LHR was found to be the best IR related indicators to predict prognosis of CRC, and it was negatively correlated with the prognosis of patients with CRC. NLR and aging might interact with LHR.

Effects of hsa_circ_0074854 on colorectal cancer progression, construction of a circRNA-miRNA-mRNA network, and analysis of immune infiltration

PURPOSE

Circular RNAs have been demonstrated to be closely associated with the onset and metastasis of colorectal cancer. However, the roles and clinical diagnostic value of most circRNAs in colorectal cancer remain unclear.

METHODS

We detected the differential expression of circRNAs in CRC tissues and cells and investigated their relationship in conjunction with clinical pathological features. Additionally, we performed cellular functional experiments in CRC cell lines to explore the functions of circRNAs. To further validate the potential ceRNA network, qPCR was performed to assess the expression of miRNA and mRNA in CRC cells after differential expression of circRNAs knockdown. Furthermore, database analysis was utilized to explore the relationship between the predicted mRNAs and immune infiltration in CRC.

RESULTS

Our research findings indicate a positive correlation between hsa_circ_0074854 expression and advanced clinical pathological features, as well as an unfavorable prognosis. Knockdown of hsa_circ_0074854 was observed to inhibit proliferation and migration capabilities of colorectal cancer cells, affecting the cell cycle progression, and simultaneously promoting apoptosis. A competing endogenous RNA mechanism may exist among circRNAs, miRNAs, and mRNAs. Furthermore, the expression of target genes displayed correlations with the abundance of certain immune cells.

CONCLUSION

We propose a novel ceRNA network and evaluate the interplay between target genes and immune cells, providing novel insights for the diagnosis and targeted therapy of CRC.

Serum circRNA_100199 is a Prognostic Biomarker in Acute Myeloid Leukemia

Background

An aberrant level of serum microRNA expression has been demonstrated to be a prognostic marker for acute myeloid leukemia (AML). The therapeutic relevance of serum circRNA 100199 remained unknown, however. This research aimed to investigate the probable prognostic significance of serum circRNA_100199 for AML.

Methods

This study included a total of 200 participants consisting of 114 AML-diagnosed patients and 86 healthy people. Blood samples were taken, and the level of circRNA_100199 in the serum was measured using quantitative reverse transcription polymerase chain reaction (qRT-PCR) to explore its potential clinical significance.

Results

Our study demonstrated that circRNA_100199 expression in the serum was substantially higher in AML subjects than in healthy persons. This increase in serum circRNA_100199 levels was particularly noticeable in M4/M5 subtype AML patients, and those with poor cytogenetic risk or higher white blood cell counts. Using receiver operating characteristic (ROC) analysis, AML cases were effectively differentiated from healthy persons based on the level of serum circRNA_100199. Furthermore, it was found that high serum circRNA_100199 expression was strongly linked with shorter survival times and more severe clinical features. Our study also confirmed that high serum circRNA_100199 expression was an independent predictor of relapse-free survival (RFS) and overall survival (OS) in AML patients. Interestingly, the serum expression level of circRNA_100199 was significantly reduced following treatment, and its levels were substantially lower in AML patients who achieved complete remission (CR) than those who did not.

Conclusion

Overall, these findings suggest that serum circRNA_100199 has the potential to be a favorable prognostic biomarker for AML.

Circ_0005615 Regulates the Progression of Colorectal Cancer Through the miR-873-5p/FOSL2 Signaling Pathway

To determine the effects of circ_0005615 in CRC development and underneath mechanism. The expression levels of circ_0005615, microRNA-873-5p (miR-873-5p) and FOS-like antigen 2 (FOSL2) mRNA were determined by quantitative real-time polymerase chain reaction (qRT-PCR). The protein levels of exosome makers, proliferation-related makers and FOSL2 were detected by western blot or immunohistochemistry assay. Cell proliferation was evaluated by cell counting kit-8 (CCK-8) and cell colony formation assays. Cell migration and invasion were demonstrated by a transwell assay. Cell apoptosis was investigated by flow cytometry analysis. The binding relationship between miR-873-5p and circ_0005615 or FOSL2 was predicted by circular RNA interactome and targetscan online databases, respectively, and identified by dual-luciferase reporter assay. The impacts of circ_0005615 silencing on tumor formation were determined by in vivo tumor formation assay. Circ_0005615 expression was dramatically upregulated in serum exosomes of CRC patients compared with the control group. The CRC patients with a high circ_0005615 expression had a poor survival rate. Circ_0005615 and FOSL2 expressions were apparently increased, while miR-873-5p was decreased in CRC tissues or cells relative to control groups. Circ_0005615 knockdown inhibited cell proliferation, migration, and invasion, whereas promoted cell apoptosis in CRC; however, miR-873-5p inhibitor attenuated these impacts. Additionally, circ_0005615 acted as a sponge of miR-873-5p and miR-873-5p bound to FOSL2. FOSL2 overexpression restrained the effects of miR-873-5p mimic on CRC progression. Furthermore, circ_0005615 knockdown suppressed tumor growth in vivo. Circ_0005615 modulated CRC malignant progression by controlling FOSL2 expression through sponging miR-873-5p. This finding lays a foundation for the study on circRNA-mediated CRC therapy.

CircUSP10 promotes liver cancer progression by regulating miR-211-5p/TCF12/EMT signaling pathway

There is no precise diagnosis or prognosis for liver cancer (LC) using a single biomarker. Circular RNAs (circRNAs) contribute to the pathogenesis of different cancers, but their role in LC is not entirely understood. In this study, circUSP10, an aberrantly expressed circRNA in LC, was screened using the Gene Expression Omnibus database, and its tissue-specific expression was verified using qRT-PCR. In vitro, functional assays and nude mouse tumorigenesis models were used to investigate circUSP10 role in LC. RNA immunoprecipitation and dual-luciferase reporter assays were performed to study the mechanistic relationship between circUSP10, miR-211-5p, and transcription factor 12 (TCF12). We found that circUSP10 expression was upregulated in LC tissues and cells. CircUSP10 expression was linked to tumor size and tumor node metastasis stage and negatively correlated with LC prognosis. In vitro assays confirmed circUSP10-mediated proliferation, migration, and invasion of LC cells and their association with the epithelial-mesenchymal transition (EMT) pathway. Mechanistically, circUSP10 adsorbed miR-211-5p, which regulated TCF12 and promoted tumorigenesis via the EMT signaling pathway. Therefore, our results suggest that circUSP10 may promote LC progression by modulating the miR-211-5p/TCF12/EMT signaling cascade and may serve as a potential biomarker for LC diagnosis and prognosis.

Phytochemicals targeting glycolysis in colorectal cancer therapy: effects and mechanisms of action

Colorectal cancer (CRC) is the third most common malignant tumor in the world, and it is prone to recurrence and metastasis during treatment. Aerobic glycolysis is one of the main characteristics of tumor cell metabolism in CRC. Tumor cells rely on glycolysis to rapidly consume glucose and to obtain more lactate and intermediate macromolecular products so as to maintain growth and proliferation. The regulation of the CRC glycolysis pathway is closely associated with several signal transduction pathways and transcription factors including phosphatidylinositol 3-kinases/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR), adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK), hypoxia-inducible factor-1 (HIF-1), myc, and p53. Targeting the glycolytic pathway has become one of the key research aspects in CRC therapy. Many phytochemicals were shown to exert anti-CRC activity by targeting the glycolytic pathway. Here, we review the effects and mechanisms of phytochemicals on CRC glycolytic pathways, providing a new method of drug development.

METTL9 derived circular RNA circ-METTL9 sponges miR-551b-5p to accelerate colorectal cancer progression by upregulating CDK6

Circular RNAs (circRNAs) have been accepted to play key roles in the development and progression of mutiple cancers including colorectal cancer (CRC). Here, we identified circ-METTL9, derived from 2 to 4 exons of METTL9 gene, may promote CRC progression by accelerating cell cycle progression. However, the role and mechanism of circ-METTL9 in CRC remains unclear. Based on our data, the expression of circ-METTL9 was significantly upregulated in CRC tissues and markedly increased in advanced tumors in CRC patients. Functional experiments demonstrated that circ-METTL9 overexpression promoted CRC cells proliferation and migration in vitro, and simultaneously enhanced CRC tumor growth and metastasis in vivo. Mechanistically, RNA immunoprecipitation (RIP) assays proved that circ-METTL9 might be a miRNA sponge, and RNA pulldown assays showed the interaction between circ-METTL9 and miR-551b-5p. Notably, cyclin-dependent kinase 6 (CDK6), a key regulator in cell cycle, is a conserved downstream target of miR-551b-5p. Taken together, our findings highlight a novel oncogenic function of circ-METTL9 in CRC progression via circ-METTL9/miR-551b-5p/CDK6 axis, which may serve as a prognostic biomarker and therapeutic target for CRC patients.

Cancer chemoresistance and its mechanisms: Associated molecular factors and its regulatory role

Cancer therapy has advanced from tradition chemotherapy methods to targeted therapy, novel drug delivery mechanisms, combination therapies etc. Although several novel chemotherapy strategies have been introduced, chemoresistance still remains as one of the major barriers in cancer treatments. Chemoresistance can lead to relapse and hinder the development of improved clinical results for cancer patients, and this continues to be the major hurdle in cancer therapy. Anticancer drugs acquire chemoresistance through different mechanisms. Understanding these mechanisms is crucial to overcome and increase the efficiency of the cancer therapies that are employed. The potential molecular pathways behind chemoresistance include tumor heterogeneity, elevated drug efflux, multidrug resistance, interconnected signaling pathways, and other factors. To surpass this limitation, new clinical tactics are to be introduced. This review aims to compile the most recent information on the molecular pathways that regulate chemoresistance in cancers, which will aid in development of new therapeutic targets and strategies.

Circular RNA circSEMA5A facilitates colorectal cancer development by regulating microRNA-195-5p to target CCNE1 axis

Colorectal cancer (CRC) is one of the most prevalent malignancies with a high mortality rate worldwide. Circular RNAs (circRNAs) have lately emerged as key molecules involved in cancer development and metastasis. CircSEMA5 is reported to be oncogenic in some cancers, yet its role in the pathogenesis of CRC remains unknown. Herein, we attempted to investigate the functional role and molecular mechanism of circSEMA5A underlying CRC progression. RT-qPCR and RNase R digestion assays were used to evaluate circSEMA5A expression characteristics in CRC cells. Loss-of-function assays were performed to clarify circSEMA5A role in CRC biological processes. Bioinformatics and mechanism experiments were conducted to assess the association of circSEMA5A or CCNE1 with miR-195-5p in CRC cells. Rescue assays were conducted to explore the regulatory function of circSEMA5A-miR-195-5p-CCNE1 in CRC cellular processes. Through bioinformatics and functional screening, we found that circSEMA5A was highly expressed in CRC cells and was mainly localized in the nucleus. CircSEMA5A promoted CRC proliferative, migratory, and invasive capabilities in cultured cells and facilitated the tumorigenic process in xenografts; however, circSEMA5A silencing repressed tumor metastasis in CRC cells. Mechanistically, circSEMA5A was competitively bound with miR-195-5p to upregulate CCNE1 expression. Moreover, the impact of circSEMA5A knockdown on CRC cell proliferative, migratory, and invasive capabilities was countervailed by miR-195-5p inhibitor or CCNE1 overexpression. To summarize, circSEMA5A is a novel circRNA that serves as an oncogene in CRC progression. CircSEMA5A facilitates CRC cell malignancy and tumor growth through sponging miR-195-5p to upregulate CCNE1, thus providing a new direction for CRC diagnosis and targeted therapy.

CircRNAs in colorectal cancer: potential biomarkers and therapeutic targets

Globally, colorectal cancer (CRC) is the third most prevalent cancer and the second leading cause of cancer-related deaths. Circular RNAs (circRNAs) are single-stranded RNA with covalently closed-loop structures and are highly stable, conserved, and abundantly expressed in various organs and tissues. Recent research found abnormal circRNA expression in CRC patients' blood/serum, cells, CRC tissues, and exosomes. Furthermore, mounting data demonstrated that circRNAs are crucial to the development of CRC. CircRNAs have been shown to exert biological functions by acting as microRNA sponges, RNA-binding protein sponges, regulators of gene splicing and transcription, and protein/peptide translators. These characteristics make circRNAs potential markers for CRC diagnosis and prognosis, potential therapeutic targets, and circRNA-based therapies. However, further studies are still necessary to improve the understanding of the roles and biological mechanisms of circRNAs in the development of CRC. In this review, up-to-date research on the role of circRNAs in CRC was examined, focusing on their potential application in CRC diagnosis and targeted therapy, which would advance the knowledge of the functions of circRNAs in the development and progression of CRC.

Circular RNA hsa_circ_0064559 affects tumor cell growth and progression of colorectal cancer

BACKGROUND

Colorectal cancer (CRC) is the second leading cause of cancer-related deaths globally. It is essential to identify new CRC-associated therapeutic targets and diagnostic biomarkers. Previous studies have demonstrated that a series of circular RNAs (circRNAs) play a crucial role in CRC pathogenesis. This study assessed the potential of hsa_circ_0064559 in tumor cell growth and progression of CRC.

METHODS

Six pairs of matched CRC and normal colorectal tissue samples were sequenced using the Affymetrix Clariom D array. Using RNA interference, the expression of thirteen circRNAs was knocked down in CRC cells. The proliferation of CRC cell lines (RKO and SW620 cells) was detected using 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay. Apoptosis and cell cycle were determined by flow-cytometric analysis. An in vivo study uses nude mice to establish a CRC mouse model. The differentially expressed genes were analyzed using Affymetrix primeview human GeneChip array and verified by polymerase chain reaction.

RESULTS

Affymetrix Clariom D array analysis revealed that thirteen circRNAs were upregulated in CRC. The proliferation of CRC cell lines was decreased, while the proportion of apoptotic and G1 phase cells was higher after hsa_circ_0064559 knockdown. In vivo xenograft nude mice model revealed that the volume and weight of the tumor were reduced by hsa_circ_0064559 knockdown. In Affymetrix primeview human GeneChip array, we found six upregulated genes (STAT1, ATF2, TNFRSF10B, TGFBR2, BAX, and SQSTM1) and two downregulated genes (SLC4A7 and CD274) related to apoptosis and proliferation of colorectal cancer cells after hsa_circ_0064559 knockdown.

CONCLUSIONS

The hsa_circ_0064559 knockdown could inhibit the proliferation, promote apoptosis in CRC cell lines in vitro, and inhibit the development of CRC tumors in vivo. The mechanism may be related to activating a wide range of signaling pathways. The hsa_circ_0064559 may be a potential biomarker for early diagnosis or prognosis of CRC and a novel drug target for CRC therapy.

Extracellular Vesicles Derived circSH3PXD2A Inhibits Chemoresistance of Small Cell Lung Cancer by miR-375-3p/YAP1

Introduction

Small cell lung cancer (SCLC) is a subtype of lung cancer with high malignancy and poor prognosis. Rapid acquisition of chemoresistance is one of the main reasons leading to clinical treatment failure of SCLC. Studies have indicated that circRNAs participate in multiple processes of tumor progression, including chemoresistance. However, the molecular mechanisms of circRNAs driving the chemoresistance of SCLC are not well specified.

Methods

The differentially expressed circRNAs were screened by transcriptome sequencing of chemoresistant and chemosensitive SCLC cells. The EVs of SCLC cells were isolated and identified by ultracentrifugation, Western blotting, transmission electron microscopy, nanoparticle tracking analysis and EVs uptake assays. The expression levels of circSH3PXD2A in serum and EVs of SCLC patients and healthy individuals were detected by qRT‒PCR. The characteristics of circSH3PXD2A were detected by Sanger sequencing, RNase R assay, nuclear-cytoplasmic fraction assay, and fluorescence in situ hybridization assay. The mechanisms of circSH3PXD2A inhibiting SCLC progression were studied by bioinformatics analysis, chemoresistance assay, proliferation assay, apoptosis assay, transwell assay, pull-down assay, luciferase reporting assay, and mouse xenograft assay.

Results

It was identified that the circSH3PXD2A was a prominently downregulated circRNA in chemoresistant SCLC cells. The expression level of circSH3PXD2A in EVs of SCLC patients was negatively associated with chemoresistance, and the combination of EVs-derived circSH3PXD2A and serum ProGRP (Progastrin-releasing peptide) levels had better indications for DDP-resistant SCLC patients. CircSH3PXD2A inhibited the chemoresistance, proliferation, migration, and invasion of SCLC cells through miR-375-3p/YAP1 axis in vivo and in vitro. SCLC cells cocultured with EVs secreted by circSH3PXD2A-overexpressing cells exhibited decreased chemoresistance and cell proliferation.

Conclusion

Our results manifest that EVs-derived circSH3PXD2A inhibits the chemoresistance of SCLC through miR-375-3p/YAP1 axis. Moreover, EVs-derived circSH3PXD2A may serve as a predictive biomarker for DDP-resistant SCLC patients.

MKX-AS1 Gene Expression Associated with Variation in Drug Response to Oxaliplatin and Clinical Outcomes in Colorectal Cancer Patients

Oxaliplatin (OXAL) is a commonly used chemotherapy for treating colorectal cancer (CRC). A recent genome wide association study (GWAS) showed that a genetic variant (rs11006706) in the lncRNA gene MKX-AS1 and partnered sense gene MKX could impact the response of genetically varied cell lines to OXAL treatment. This study found that the expression levels of MKX-AS1 and MKX in lymphocytes (LCLs) and CRC cell lines differed between the rs11006706 genotypes, indicating that this gene pair could play a role in OXAL response. Further analysis of patient survival data from the Cancer Genome Atlas (TCGA) and other sources showed that patients with high MKX-AS1 expression status had significantly worse overall survival (HR = 3.2; 95%CI = (1.17-9); p = 0.024) compared to cases with low MKX-AS1 expression status. Alternatively, high MKX expression status had significantly better overall survival (HR = 0.22; 95%CI = (0.07-0.7); p = 0.01) compared to cases with low MKX expression status. These results suggest an association between MKX-AS1 and MKX expression status that could be useful as a prognostic marker of response to OXAL and potential patient outcomes in CRC.

Tumor suppressor circPDE4D inhibits the progression of colorectal cancer and regulates oxaliplatin chemoresistance

Colorectal cancer (CRC) is one of the most common cancers worldwide, and it frequently develops resistance to chemotherapy. It was discovered that circular RNAs, which function as microRNA sponges, are involved in the pathogenesis of many cancers. This study aimed to investigate the biological functions of a circRNA derived from phosphodiesterase 4D (circPDE4D, hsa_circ_0072568) and its potential mechanism in oxaliplatin-resistant CRC. CircPDE4D expression were validated in human CRC cell lines and tissues. CircPDE4D siRNAs (si-circPDE4D) and LV003-circPDE4D plasmid were applied to investigate the function of circPDE4D. A quantitative real-time polymerase chain reaction was used to detect the levels of circPDE4D, its predicted sponge miRNAs, and their target genes. Cell proliferation was assessed by MTS（3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium） assay. Cell migration and invasion capacity were evaluated by transwell assay. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling was used to stain apoptotic cells. The results showed that circPDE4D expression was downregulated in CRC cells and tissues. Transfection with si-circPDE4D promoted cell proliferation, migration, and invasion, and inhibited apoptosis in DLD1 cells. Transfection with LV003-circPDE4D showed the opposite effect. Besides, circPDE4D presented higher expression in HCT116/L cells than that in HCT116 cells. Si-circPDE4D or lv003-circPDE4D transfection increased or decreased cell proliferationin in both two cells. Moreover, si-circPDE4D transfection inhibited cell apoptosis, while LV003-circPDE4D induced apoptosis in HCT116/L cells. LV003-CircPDE4D reduced hsa-miR-569 expression while increasing SPI1 expression in HCT116/L. CircPDE4D could inhibit tumorigenesis and progression of both CRC and oxaliplatin-resistant CRC, providing insight for the development of therapeutic strategies.

CircAGO2 promotes colorectal cancer progression by inhibiting heat shock protein family B (small) member 8 via miR-1-3p/retinoblastoma binding protein 4 axis

This paper was to uncover the mechanism of circular RNA Argonaute 2 (circAGO2) in colorectal cancer (CRC) progression. The expression of circAGO2 was detected in CRC cells and tissues, and the relationship between clinicopathological features of CRC and circAGO2 level was evaluated. The growth and invasion of CRC cells and subcutaneous xenograft of nude mice were measured to evaluate the effect of circAGO2 on CRC development. Bioinformatics databases were applied to analyze levels of retinoblastoma binding protein 4 (RBBP4) and heat shock protein family B 8 (HSPB8) in cancer tissues. The relevance of circAGO2 and RBBP4 expression and the relationship between RBBP4 and HSPB8 during histone acetylation were assessed. The targeting relationship between miR-1-3p and circAGO2 or RBBP4 was predicted and confirmed. The effects of miR-1-3p and RBBP4 on biological functions of CRC cells were also verified. CircAGO2 was upregulated in CRC. CircAGO2 promoted the growth and invasion of CRC cells. CircAGO2 competitively bound to miR-1-3p and regulated RBBP4 expression, thus inhibiting HSPB8 transcription by promoting histone deacetylation. Silencing circAGO2 enhanced miR-1-3p expression and reduced RBBP4 expression, while suppression of miR-1-3p downgraded levels of miR-1-3p, up-regulated RBBP4, and facilitated cell proliferation and invasion in the presence of silencing circAGO2. RBBP4 silencing decreased RBBP4 expression and reduced proliferation and invasion of cells where circAGO2 and miR-1-3p were silenced. CircAGO2 overexpression decoyed miR-1-3p to increase RBBP4 expression, which inhibited HSPB8 transcription via histone deacetylation in HSPB8 promoter region, promoting proliferation and invasion of CRC cells.

Up-regulated Circular RNAs in Colorectal Cancer: New Entities for Therapy and Tools for Identification of Therapeutic Targets

Patients with disseminated colorectal cancer have a dismal prognosis with a 5-year survival rate of only 13%. In order to identify new treatment modalities and new targets, we searched the literature for up-regulated circular RNAs in colorectal cancer which induce tumor growth in corresponding preclinical in vivo models. We identified nine circular RNAs that mediate resistance against chemotherapeutic agents, seven that up-regulate transmembrane receptors, five that induce secreted factors, nine that activate signaling components, five which up-regulate enzymes, six which activate actin-related proteins, six which induce transcription factors and two which up-regulate the MUSASHI family of RNA binding proteins. All of the circular RNAs discussed in this paper induce the corresponding targets by sponging microRNAs (miRs) and can be inhibited by RNAi or shRNA in vitro and in xenograft models. We have focused on circular RNAs with demonstrated activity in preclinical in vivo models because the latter is an important milestone in drug development. All circular RNAs with in vitro activity only data are not referenced in this review. The translational impact of inhibition of these circular RNAs and of the identified targets for treatment of colorectal cancer (CRC) are discussed.

LncRNA CASC19 Enhances the Radioresistance of Nasopharyngeal Carcinoma by Regulating the miR-340-3p/FKBP5 Axis

Radioresistance remains a serious obstacle encountered in the radiotherapy of nasopharyngeal carcinoma (NPC). Both mRNAs and non-coding RNAs (ncRNAs), including long ncRNA (lncRNA) and microRNA (miRNA), play essential roles in radiosensitivity. However, the comprehensive expression profiles and competing endogenous RNA (ceRNA) regulatory networks among lncRNAs, miRNAs, and mRNAs in NPC radioresistance are still bewildering. In this study, we performed an RNA-sequencing (RNA-seq) assay in the radioresistant NPC cells CNE2R and its parental cells CNE2 to identify the differentially expressed lncRNAs, miRNAs, and mRNAs. The ceRNA networks containing lncRNAs, miRNAs, and mRNAs were predicted on the basis of the Pearson correlation coefficients and authoritative miRanda databases. In accordance with bioinformatic analysis of the data of the tandem mass tag (TMT) assay of CNE2R and CNE2 cells and the gene chip assay of radioresistant NPC samples in pre- and post-radiotherapy, the radioresistance-related signaling network of lncRNA CASC19, miR-340-3p, and FKBP5 was screened and further verified using an RT-qPCR assay. CASC19 was positively associated with FKBP5 expression while negatively correlated with miR-340-3p, and the target binding sites of CASC19/miR-340-3p and miR-340-3p/FKBP5 were confirmed using a dual-luciferase reporter assay. Moreover, using an mRFP-GFP-LC3 maker, it was found that autophagy contributed to the radioresistance of NPC. MiR-340-3p inhibition or FKBP5 overexpression could rescue the suppression of autophagy and radioresistance induced by CASC19 knockdown in CNE2R cells. In conclusion, the CASC19/miR-340-3p/FKBP5 network may be instrumental in regulating NPC radioresistance by enhancing autophagy, which provides potential new therapeutic targets for NPC.

Circ_0000395 Promoted CRC Progression via Elevating MYH9 Expression by Sequestering miR-432-5p

Colorectal cancer (CRC) has been listed as the fourth deadly cancer. Circular RNA hsa_circRNA_001046, also termed as hsa_circ_0000395 (circ_0000395), has been shown to be upregulated in CRC. Nevertheless, the function of circ_0000395 in CRC progression is unclear. 42 CRC patients were enrolled in the study. Detection of circ_0000395 expression in tissues and cells was executed using real-time quantitative polymerase chain reaction (RT-qPCR). Evaluation of circ_0000395 function was performed using loss-of-function experiments in vitro and in vivo. The regulatory mechanism of circ_0000395 was predicted by bioinformatics analysis and validated by dual-luciferase reporter and RIP assays. Exosomes were isolated by ultracentrifugation and validated by western blotting, TEM, and NTA. Circ_0000395 was strongly expressed in CRC samples and cell lines. Also, circ_0000395 repressed CRC growth in mouse models in vivo and induced CRC cell apoptosis, restrained CRC cell proliferation, migration, invasion, and EMT in vitro. Mechanistically, circ_0000395 sequestered miR-432-5p to regulate MYH9 expression. Furthermore, miR-432-5p knockdown reversed circ_0000395 silencing-mediated effects on CRC cell malignant phenotypes. MYH9 overexpression counteracted the inhibiting effects of miR-432-5p upregulation on CRC cell malignant phenotypes. Additionally, CRC cells derived from exosomal circ_0000395 promoted cancer cell malignant phenotypes. Our findings demonstrated that circ_0000395 sequestered miR-432-5p to elevate MYH9 expression, resulting in facilitating CRC progression, manifesting a potential therapeutic target for CRC.

HDAC Inhibitor SAHA Alleviates Pyroptosis by up-regulating miR-340 to Inhibit NEK7 Signaling in Subarachnoid Hemorrhage

BACKGROUND

Subarachnoid hemorrhage (SAH) is a cerebral hemorrhagic disease with a high disability and fatality rate. Cell pyroptosis is involved in the brain injury following SAH. Here, we explored the effect of HDAC inhibitor SAHA against cell pyroptosis after SAH.

METHODS

The rat SAH model was established by endovascular perforation and the rat microglia were treated with 25 μm oxyhemoglobin (OxyHb) for 24 h to mimic SAH model in vitro. Neurological score and brain edema were assessed in rat SAH model. TUNEL staining detected apoptosis. qRT-PCR and western blotting were employed to detect expression levels of miR-340, NEK7 and inflammatory cytokines. ELISA assay determined the secretion of IL-1β and IL-18 in rat serum and cell supernatant. A lactate dehydrogenase (LDH) kit measured the LDH activity in rat primary microglia. Microglia pyroptosis was detected by flow cytometry. RIP and dual luciferase reporter assays confirmed the binding relationship between miR-340 and NEK7.

RESULTS

SAHA alleviated neurological dysfunction, inflammatory injury and microglia pyroptosis in SAH rats. SAHA suppressed LDH release, inflammatory factor expression and pyroptosis in microglia treated with OxyHb. Meanwhile, SAHA increased miR-340 expression and inhibited NEK7 level in vivo and in vitro SAH models. Further, miR-340 directly targeted NEK7 to inhibit the NLRP3 signaling pathway. Knockdown of miR-340 or overexpression of NEK7 reversed the suppressive effects of SAHA on microglia inflammation and pyroptosis. Additionally, knockdown of NEK7 impaired microglia inflammation and pyroptosis induced by miR-340 inhibitor.

CONCLUSION

HDAC inhibitor SAHA ameliorates microglia pyroptosis in SAH through triggering miR-340 expression to suppress NEK7 signaling. This novel mechanism provides promise for SAHA in SAH treatment.

Hsa_circ_0001658 accelerates the progression of colorectal cancer through miR-590-5p/METTL3 regulatory axis

BACKGROUND

As reported, multiple circular RNAs (circRNAs) interfere with colorectal cancer (CRC) progression. Here, circRNA_0001658 (circ_0001658) is focused on studying how it works in CRC.

AIM

Clarify the expression pattern, biological function, and underlying mechanism of circ_0001658 of CRC tumorigenesis.

METHODS

In CRC-related chip data retrieved using the database named Gene Expression Omnibus, different expressions of circRNAs between CRC and normal tissue samples were identified. Quantitative Real-time PCR and Western blot ensured the analysis on circ_0001658, microRNA-590-5P (miR-590-5p), and methyltransferase-like 3 (METTL3) mRNA expressions in tissues and cells. Cell counting kit-8 and flow cytometry were used to detect cell proliferation, apoptosis and migration. The targeting relations between circ_0001658, miR-590-5p, and METTL3 mRNA 3'-untranslated region were under the verification of bioinformatics prediction and dual luciferase-based reporter gene assays. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis were employed on the downstream targets of miR-590-5p using the Database for Annotation, Visualization and Integrated Discovery database.

RESULTS

Circ_0001658 and METTL3 mRNA was elevated in CRC tissues and cells, whereas miR-590-5p was decreased. Circ_0001658 overexpression promoted the proliferation of HT29 cells, inhibited apoptosis, and accelerated the cell cycle. In SW480 cells, knocking down circ_0001658 had the opposite effect. Circ_0001658 could specifically bind to miR-590-5p and negatively modulate its expressions; METTL3 is a miR-590-5p target that can be positively regulated by circ 0001658. Circ 0001658 was inversely associated with miR-590-5p expression while positively with METTL3 expressions.

CONCLUSION

Circ_0001658 regulates the miR-590-5p/METTL 3-axis to increase CRC cell growth and decrease apoptosis.

Novel hypoxia-induced HIF1α-circTDRD3-positive feedback loop promotes the growth and metastasis of colorectal cancer

Tumor hypoxia and circular RNAs (circRNAs) are considered to play key roles in tumor progression and malignancy, respectively. Nevertheless, the biological functions and underlying mechanisms of specific circRNAs exposed to hypoxic microenvironments in colorectal cancer (CRC) remain largely elusive. Herein, a novel circRNA, circTDRD3, which is upregulated under hypoxic conditions, was identified. The expression of circTDRD3 was highly expressed in CRC tissues and positively correlated with overall survival, tumor size, lymph node invasion and clinical stage. CircTDRD3 facilitated CRC cell proliferation, migration and metastasis in vitro and in vivo. Mechanistically, circTDRD3 promoted HIF1α expression by sponging miR-1231, which facilitated CRC progression. Meanwhile, HIF1α directly combined with TDRD3 promoter to increase the expression of TDRD3 pre-mRNA. Then HIF1a-induced PTBP1 accelerated the formation of circTDRD3. Our findings reveal that circTDRD3 facilitates the proliferation and metastasis of CRC through a positive feedback loop mediated by the HIF1α/PTBP1/circTDRD3/miR-1231/HIF1α axis. Therefore, circTDRD3 may serve as a prognostic biomarker and therapeutic target for patients with CRC.

Knockdown of circ_0004585 enhances the chemosensitivity of colorectal cancer cells to 5-fluorouracil via the miR-874-3p/CCND1 axis

BACKGROUND

Colorectal cancer (CRC) is a serious threat to human health and is drug-resistant. Circular RNA _0004585 (circ_0004585) has been shown to be expressed in CRC, but whether it plays a role in CRC with chemoresistance remains unknown. Therefore, this study aimed to investigate the potential role of circ_0004585 in CRC with 5-fluorouracil (5-FU) resistance.

METHODS

The expression of related genes was detected by quantitative real-time polymerase chain reaction (qRT-PCR), and the protein expressions of cleaved caspase-3, cleaved caspase-9, and cyclin D1 (CCND1) were detected by western blot. Cell functions were identified using CCK-8, colony formation, flow cytometry, tube formation and transwell assays. The putative relationships between miR-874-3p and circ_0004585 or CCND1 were validated by dual-luciferase reporter assays. Animal experiments were conducted to verify the effect of circ_0004585 on 5-FU resistance in vivo.

RESULTS

Circ_0004585 was highly expressed in CRC tissues and cells, particularly in 5-FU-resistant CRC tissues and cells. Circ_0004585 knockdown enhanced 5-FU sensitivity to further inhibit CRC cell viability, colony formation, cell migration and invasion, and accelerate cell apoptosis. MiR-874-3p was the target of circ_0004585, and miR-874-3p depletion partially recovered the malignant behaviors of 5-FU-resistant CRC cells that were blocked by silencing of circ_0004585. In addition, CCND1 was the target of miR-874-3p, and overexpression of CCND1 was able to restore the malignant effects of 5-FU-resistant CRC cells that were repressed by miR-874-3p enrichment. Animal experiments confirmed that circ_0004585 knockdown inhibited the growth of CRC tumors and enhanced 5-FU sensitivity in vivo.

CONCLUSION

Circ_0004585 promotes the development of CRC and increases 5-FU resistance in CRC through the miR-874-3p/CCND1 axis. These results suggest that circ_0004585 may be a therapeutic target for 5-FU-ressitant CRC.

CircRNA expression profiles and functional analysis in a mouse model of chronic intermittent hypoxia-induced renal injury: new insight into pathogenesis

Increasing evidence has demonstrated that circular RNAs (circRNAs) play crucial roles in the pathogenesis of multiple diseases. However, the functions of circRNAs in renal injury induced by obstructive sleep apnea (OSA) are poorly understood. The aim of this current study is to identify the global changes of circRNAs expression in OSA-induced renal damage. The mouse model of OSA treated by chronic intermittent hypoxia (CIH) was established. We assessed the expression profiles of circRNAs in CIH caused renal injury by microarray analysis. Bioinformatic analyses were further performed by us to assess those differentially expressed circRNAs. Quantitative realtime PCR (qRT-PCR) were then conducted to assure the data of microarray. Finally, a circRNA-miRNA -mRNA competing endogenous RNA (ceRNA) regulatory network was constructed. We found 11 upregulated and 13 downregulated circRNAs in CIH-induced renal injury. The qRT-PCR validated that the six selected circRNAs were identical to the results of microarray. Both Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were further employed to annotate the potential functions of dysregulated circRNAs. Finally, we established a ceRNA network to predict the target genes of circRNAs. In general, our results first illustrate that circRNAs are aberrantly expressed in OSA-induced renal injury, which might aid in offering novel genetic insights into this disease and potential therapeutic targets for OSA-associated chronic kidney disease.

Current evidence on circRNAs as potential theranostic markers for detecting chemoresistance in breast cancer: a systematic review and meta‑analysis

This study assessed the value of circRNAs (circular RNAs) as prognostic markers in BC (breast cancer). We searched pertinent studies on the PubMed, Embase, and Web of Science online databases published according to PRISMA guidelines. A random-effects model for meta-analysis was used to assess the combined effect size of the HRs (hazard ratios) of the included studies. The heterogeneity test used Cochran's Q-test and I² statistics. Thirty of the 520 trials retrieved were included in the systematic review. A total of 11 chemotherapeutic agents were used in the included studies. A total of 30 studies on 30 circRNAs were included in the systematic review. Of the 30 relevant circRNAs, 28 were upregulated and two were downregulated in breast cancer versus normal samples, and both were associated with increased drug resistance. Nine of 30 studies were used for the meta-analysis. The results of the meta-analysis showed that the groups with circRNA upregulation and circRNA downregulation showed the same prognostic risk (HR = 1.37, 95% Cl: 0.80-2.36, I² = 63.7%). The results of subgroup analysis showed that both upregulated circRNAs (HR = 2.24, 95% Cl: 1.34-3.75, I² = 0%) and downregulated circRNAs (HR = 0.61, 95% Cl: 0.45-0.83, I² = 0%) were associated with poor BC prognosis. Collectively, the results of all relevant articles collected indicated that circRNAs showed good potential as possible clinical biomarkers of chemoresistance in BC patients.

Cancer stem cell-like cells-derived exosomal lncRNA CDKN2B-AS1 promotes biological characteristics in thyroid cancer via miR-122-5p/P4HA1 axis

Introduction

Here, the discussion focused on the function and possible mechanism of cancer stem cell-like cells (CSCs)-derived exosomal CDKN2B-AS1 in thyroid cancer.

Methods

Specifically, the bioinformatics analysis, dual-luciferase reporter assay and RT-qPCR were conducted to obtain the expression and regulation of CDKN2B-AS1, and the downstream miR-122-5p/P4HA1 axis. Exosomes were identified by transmission electron microscopy. The uptake of exosome by recipient cells was observed by PKH67 labeling. Functional experiments and western blot were adopted to detect the effects of exosomal CDKN2B-AS1/miR-122-5p/P4HA1 axis on thyroid cancer cells. Tumor xenograft and in vivo metastasis model combined with RT-qPCR, western blot and hematoxylin-eosin staining verified the role of CDKN2B-AS1.

Results

Exosomal CDKN2B-AS1 up-regulated P4HA1 expression through miR-122-5p. CDKN2B-AS1 and P4HA1 expressions were up-regulated, and miR-122-5p expression was down-regulated in thyroid cancer. Silent CDKN2B-AS1 reduced cell viability and stemness. CDKN2B-AS1 was found to be abundant in CSCs and CSCs-derived exosomes. Exosomal CDKN2B-AS1 silencing could transfer to thyroid cancer cells to elevate E-cadherin level, and diminish P4HA1, N-cadherin and Vimentin levels, thus impeding cell migration and invasion. MiR-122-5p inhibitor reversed the function of exosomal CDKN2B-AS1, while P4HA1 silencing attenuated the effect of miR-122-5p inhibitor. Exosomal CDKN2B-AS1 affected the growth and metastasis of thyroid cancer through the miR-122-5p/P4HA1 axis.

Conclusion

CSCs-derived exosomal CDKN2B-AS1 acts as an oncogene in thyroid cancer through miR-122-5p/P4HA1 axis.

Cancer Stem Cells-The Insight into Non-Coding RNAs

Since their initial identification three decades ago, there has been extensive research regarding cancer stem cells (CSCs). It is important to consider the biology of cancer stem cells with a particular focus on their phenotypic and metabolic plasticity, the most important signaling pathways, and non-coding RNAs (ncRNAs) regulating these cellular entities. Furthermore, the current status of therapeutic approaches against CSCs is an important consideration regarding employing the technology to improve human health. Cancer stem cells have claimed to be one of the most important group of cells for the development of several common cancers as they dictate features, such as resistance to radio- and chemotherapy, metastasis, and secondary tumor formation. Therapies which could target these cells may develop into an effective strategy for tumor eradication and a hope for patients for whom this disease remains uncurable.

FMR1 promotes the progression of colorectal cancer cell by stabilizing EGFR mRNA in an m6A-dependent manner

FMR1, a new m⁶A reader, is known to be involved in the regulation of cancer progression. However, its role, regulatory mechanism, and clinical significance in colorectal cancer (CRC) are elusive. Here, we showed that FMR1 was upregulated in CRC, and it promoted proliferation and metastasis of CRC cells in vitro and in vivo. Mechanically, FMR1 recognized the m⁶A-modification site in EGFR mRNA, a key molecule in cancer occurrence and targeted therapy, sustained its stability and maintained its expression in an m⁶A-dependent manner, thereby promoting the tumorigenesis and metastasis of CRC. And the effect of FMR1 knockdown in CRC cells could be abolished by METTL3. Furthermore, FMR1 shRNA plasmid carried by attenuated Salmonella has an effective anti-tumor effect in vivo. Collectively, we identified the METTL3/FMR1/EGFR axis in the progression of CRC. This novel mechanism indicated that the METTL3/FMR1/EGFR axis is a potential target for early therapeutic intervention in CRC progression.

Circ_0008285 knockdown represses tumor development by miR-384/RRM2 axis in hepatocellular carcinoma

INTRODUCTION AND OBJECTIVES

Circular RNA (circRNA) has attracted extensive attention in studies related to the malignant progression of cancer, including hepatocellular carcinoma (HCC). Therefore, its molecular mechanism in HCC needs to be further explored.

MATERIALS AND METHODS

The expression levels of circ_0008285, microRNA (miR)-384 and ribonucleotide reductase subunit M2 (RRM2) mRNA were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Cell proliferation was analyzed using cell counting kit-8 assay and 5-ethynyl-2'-deoxyuridine assay, cell apoptosis was analyzed by flow cytometry, and cell migration and invasion were detected by transwell assay. Protein level was detected by western blot. The relationships between miR-384 and circ_0008285 or RRM2 were predicted by bioinformatics software and validated by dual luciferase reporter assay and RNA immunoprecipitation (RIP) assay.

RESULTS

Circ_0008285 expression is elevated to HCC tissues and cell lines. Silencing of circ_0008285 inhibited the proliferation, migration and invasion of HCC cells but accelerated cell apoptosis in vitro and impeded HCC tumorigenesis in vivo. Mechanistically, circ_0008285 directly interacted with miR-384, and miR-384 silencing attenuated the effects of circ_0008285 interference on cell proliferation, migration, invasion, and apoptosis. RRM2 was a direct target of miR-384, and RRM2 overexpression reversed the effects of miR-384 overexpression on cell proliferation, migration, invasion, and apoptosis. In addition, circ_0008285 regulated RRM2 expression by sponging miR-384.

CONCLUSION

In this study, circ_0008285 could promote the malignant biological behaviors of HCC cells through miR-384/RRM2 axis and has the potential to become a therapeutic target for HCC, providing a new idea for targeted therapy of HCC.

Circ_0082182 upregulates the NFIB level via sponging miR-326 to promote oxaliplatin resistance and malignant progression of colorectal cancer cells

Circular RNAs (circRNAs) are key regulators in tumor metastasis and drug resistance. This study was designed to investigate circ_0082182 function and mechanism in oxaliplatin (OXA) resistance and cancer progression of colorectal cancer (CRC). The circ_0082182, microRNA-326 (miR-326), and nuclear factor I B (NFIB) levels were quantified by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Cell sensitization was analyzed by Cell Counting Kit-8 assay. The proliferation ability was determined via EdU assay, and apoptosis was measured by flow cytometry. Transwell assay and wound healing assay were performed to assess cell invasion and migration. The protein level was examined through Western blot. The binding interaction was conducted via dual-luciferase reporter assay. Xenograft tumor assay was used to explore the circ_0082182 function in vivo. The circ_0082182 level was upregulated in OXA-resistant CRC samples and cells. Downregulation of circ_0082182 suppressed OXA resistance, proliferation, invasion, and migration but promoted apoptosis of OXA-resistant CRC cells. Circ_0082182 acted as a sponge for miR-326. The regulatory role of circ_0082182 was ascribed to the miR-326 sponging function. MiR-326 directly targeted NFIB to impede OXA resistance and cancer progression in CRC cells. NFIB level was regulated by circ_0082182 via sponging miR-326. Circ_0082182 promoted tumor growth in OXA-resistant xenograft tumor model through mediating the miR-326/NFIB axis. These data suggested that circ_0082182 elevated the NFIB expression to regulate OXA resistance and CRC progression by absorbing miR-326.

Use of Personalized Biomarkers in Metastatic Colorectal Cancer and the Impact of AI

Colorectal cancer is a major cause of cancer-related death worldwide and is correlated with genetic and epigenetic alterations in the colonic epithelium. Genetic changes play a major role in the pathophysiology of colorectal cancer through the development of gene mutations, but recent research has shown an important role for epigenetic alterations. In this review, we try to describe the current knowledge about epigenetic alterations, including DNA methylation and histone modifications, as well as the role of non-coding RNAs as epigenetic regulators and the prognostic and predictive biomarkers in metastatic colorectal disease that can allow increases in the effectiveness of treatments. Additionally, the intestinal microbiota’s composition can be an important biomarker for the response to strategies based on the immunotherapy of CRC. The identification of biomarkers in mCRC can be enhanced by developing artificial intelligence programs. We present the actual models that implement AI technology as a bridge connecting ncRNAs with tumors and conducted some experiments to improve the quality of the model used as well as the speed of the model that provides answers to users. In order to carry out this task, we implemented six algorithms: the naive Bayes classifier, the random forest classifier, the decision tree classifier, gradient boosted trees, logistic regression and SVM.