Up-Regulation of circEIF6 Contributes to Pancreatic Cancer Development Through Targeting miR-557/SLC7A11/PI3K/AKT Signaling

Circular RNA in Pancreatic Cancer: Biogenesis, Mechanism, Function and Clinical Application

Circular RNAs (circRNAs) are a class of novel RNA molecules featured by single-strand covalently closed circular structure, which not only are extensively found in eukaryotes and are highly conserved, but also conduct paramount roles in the occurrence and progression of pancreatic cancer (PC) through diverse mechanisms. As recent studies have demonstrated, circRNAs typically exhibit tissue-specific and cell specific expression patterns, with strong potential as biomarkers for disease diagnosis and prognosis. On the basis of their localization and specific interactions with DNA, RNA, and proteins, circRNAs are considered to possess specific biological functions by acting as microRNA (miRNA) sponges, RNA binding protein (RBP) sponges, transcriptional regulators, molecular scaffolds and translation templates. On that account, further addressing the technical difficulties in the detection and research of circRNAs and filling gaps in their biological knowledge will definitely push ahead this comparatively young research field and bring circRNAs to the forefront of clinical practice. Thus, this review systematically summarizes the biogenesis, function, molecular mechanisms, biomarkers and therapeutic targets of circRNAs in PC.

The functional roles of competitive endogenous RNA (ceRNA) networks in apoptosis in human cancers: The circRNA/miRNA/mRNA regulatory axis and cell signaling pathways

Circular RNAs are noncoding RNAs with circular conformation mainly due to backsplicing event. CircRNAs can potentially impact cell biological processes by interacting with cell signaling pathways. Numerous circRNAs have been found to be aberrantly expressed in a variety of cancers. These RNAs can act as ceRNA (competitive endogenous RNA) by sponging certain miRNAs to form circRNA/miRNA/mRNA networks. Dysregulation of ceRNA networks may lead to dysfunctions in various cell pathways, which modulate apoptosis-associated genes and ultimately result in cancer progression. Since disruption of apoptosis is one of the leading causes of cancer development, one approach for cancer treatment is to drive cells toward apoptosis. In this review, we present a summary of studies on the role of ceRNA networks in cellular signaling pathways that regulate apoptosis; these networks are suggested to be potential biomarkers for cancer treatment.

eIF6 Promotes Gastric Cancer Proliferation and Invasion by Regulating Cell Cycle

OBJECTIVE

To investigate the role and function of eIF6 in gastric cancer (GC).

METHODS

The expression level of eIF6 in GC tissues and normal tissues was detected in different high-throughput sequencing cohorts. Survival analysis, gene differential analysis, and enrichment analysis were performed in the TCGA cohort. Biological networks centered on eIF6 were constructed through two different databases. Immunohistochemistry (IHC) and Western blot were used to detect protein expression of eIF6, and qRT-PCR was used to detect eIF6 mRNA expression. The correlation between the expression of eIF6 in GC tissues and clinicopathological parameters of GC was analyzed. siRNA knockout of eIF6 was used to study the proliferation, migration, and invasion. The effects of eIF6 on cell cycle and Cyclin B1 were detected by flow cytometry and Western blot.

RESULTS

eIF6 was significantly overexpressed in GC tissues and predicted poor prognosis. In addition, 113 differentially expressed genes were detected in cancer-related biological pathways and functions by differential analysis. Biological networks revealed interactions of genes and proteins with eIF6. The expression intensity of eIF6 in cancer tissues was higher than that in adjacent tissues (P = 0.0001), confirming the up-regulation of eIF6 expression in GC tissues. The expression level of eIF6 was statistically significant with pTNM stage (P = 0.006). siRNA knockout of eIF6 significantly reduced the proliferation, colony formation, migration, and invasion ability of GC cells. Silencing of eIF6 also inhibited the cell cycle of GC cells in G2/M phase and decreased the expression level of CyclinB1.

CONCLUSION

Our study suggests that eIF6 is up-regulated in GC and may promote the proliferation, migration, and invasion of GC by regulating cell cycle.

CircRNAs in Pancreatic Cancer: New Tools for Target Identification and Therapeutic Intervention

We have reviewed the literature for circular RNAs (circRNAs) with efficacy in preclinical pancreatic-cancer related in vivo models. The identified circRNAs target chemoresistance mechanisms (n=5), secreted proteins and transmembrane receptors (n=15), transcription factors (n=9), components of the signaling- (n=11), ubiquitination- (n=2), autophagy-system (n=2), and others (n=9). In addition to identifying targets for therapeutic intervention, circRNAs are potential new entities for treatment of pancreatic cancer. Up-regulated circRNAs can be inhibited by antisense oligonucleotides (ASO), small interfering RNAs (siRNAs), short hairpin RNAs (shRNAs) or clustered regularly interspaced short-palindromic repeats-CRISPR associated protein (CRISPR-CAS)-based intervention. The function of down-regulated circRNAs can be reconstituted by replacement therapy using plasmids or virus-based vector systems. Target validation experiments and the development of improved delivery systems for corresponding agents were examined.

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.

Mechanisms of immune checkpoint inhibitors: insights into the regulation of circular RNAS involved in cancer hallmarks

Current treatment strategies for cancer, especially advanced cancer, are limited and unsatisfactory. One of the most substantial advances in cancer therapy, in the last decades, was the discovery of a new layer of immunotherapy approach, immune checkpoint inhibitors (ICIs), which can specifically activate immune cells by targeting immune checkpoints. Immune checkpoints are a type of immunosuppressive molecules expressed on immune cells, which can regulate the degree of immune activation and avoid autoimmune responses. ICIs, such as anti-PD-1/PD-L1 drugs, has shown inspiring efficacy and broad applicability across various cancers. Unfortunately, not all cancer patients benefit remarkably from ICIs, and the overall response rates to ICIs remain relatively low for most cancer types. Moreover, the primary and acquired resistance to ICIs pose serious challenges to the clinical application of cancer immunotherapy. Thus, a deeper understanding of the molecular biological properties and regulatory mechanisms of immune checkpoints is urgently needed to improve clinical options for current therapies. Recently, circular RNAs (circRNAs) have attracted increasing attention, not only due to their involvement in various aspects of cancer hallmarks, but also for their impact on immune checkpoints in shaping the tumor immune microenvironment. In this review, we systematically summarize the current status of immune checkpoints in cancer and the existing regulatory roles of circRNAs on immune checkpoints. Meanwhile, we also aim to settle the issue in an evidence-oriented manner that circRNAs involved in cancer hallmarks regulate the effects and resistance of ICIs by targeting immune checkpoints.

circ_0058063 promotes breast cancer progression by upregulating DLGAP5 via sponging miR-557

OBJECTIVE

Accumulating evidence indicates that circular RNAs (circRNAs) contribute to breast cancer (BC) development and progression. However, the role of circ_0058063 in BC and its underlying molecular processes remain unclear.

METHODS

The expression of circ_0058063, miR-557, and DLGAP5 in BC tissues and cells was determined using real time quantitative PCR or western blotting. The functions of circ_0058063 in BC cells were detected using CCK-8, Transwell, caspase-3 activity, and xenograft tumor assays. The specific binding of circ_0058063/miR-557 and DLGAP5/miR-557 was verified using RNA immunoprecipitation (RIP) and dual-luciferase reporter assays.

RESULTS

circ_0058063 expression was upregulated in BC tissues and cells. circ_0058063 knockdown inhibited proliferation and migration but promoted apoptosis in MCF-7 and MDA-MB-231 cells in vitro. In vivo studies further validated that the knockdown of circ_0058063 repressed tumor growth. Mechanistically, circ_0058063 directly sponged miR-557 and negatively regulated its expression. Additionally, miR-557 inhibition reversed the tumor-suppressive effects of the circ_0058063 knockdown on the survival of MDA-MB-231 and MCF-7 cells. Moreover, miR-557 directly targeted DLGAP5. DLGAP5 knockdown suppressed MCF-7 and MDA-MB-231 cell growth, and these effects were reversed by miR-557 downregulation.

CONCLUSION

Our findings verify that circ_0058063 acts as a sponge for miR-557 to upregulate DLGAP5 expression. These findings suggest that the circ_0058063/miR-557/DLGAP5 axis is an important regulator of oncogenic function and may be a promising therapeutic target for BC.

Circular RNAs in pancreatic cancer progression

Pancreatic cancer (PC), typically diagnosed at relatively advanced stages with poor prognosis, is a dominant cause of cancer-related deaths worldwide. Accumulating evidence demonstrates that circular RNAs (circRNAs) are abnormally expressed in diverse tumors and affect tumorigenesis and progression. In this article, we examine the roles of circRNAs in regulation of PC progression. Additionally, circRNAs enriched in exosomes could be transferred among PC cells to modulate malignancy. Characterization of regulatory mechanisms involving circRNAs in general and PC specifically will enable earlier detection and potential development of therapeutic strategies.

Exploring the dual role of circRNA and PI3K/AKT pathway in tumors of the digestive system

The interactions among circRNAs, the PI3K/AKT pathway, and their downstream effectors are intricately linked to their functional roles in tumorigenesis. Furthermore, the circRNAs/PI3K/AKT axis has been significantly implicated in the context of digestive system tumors. This axis is frequently abnormally activated in digestive cancers, including gastric cancer, colorectal cancer, pancreatic cancer, and others. Moreover, the overactivation of the circRNAs/PI3K/AKT axis promotes tumor cell proliferation, suppresses apoptosis, enhances invasive and metastatic capabilities, and contributes to drug resistance. In this regard, gaining crucial insights into the complex interaction between circRNAs and the PI3K/AKT pathway holds great potential for elucidating disease mechanisms, identifying diagnostic biomarkers, and designing targeted therapeutic interventions.

Circular RNA eukaryotic translation initiation factor 6 facilitates TPC-1 cell proliferation and invasion through the microRNA-138-5p/lipase H axis

Both circular RNA eukaryotic translation initiation factor 6 (circEIF6) and microRNA (miR)-138-5p participate in thyroid cancer (TC) progression. Nevertheless, the relationship between them remains under-explored. Hence, this research ascertained the mechanism of circEIF6 in TC via miR-138-5p. After TC tissues and cells were harvested, circEIF6, miR-138-5p, and lipase H (LIPH) levels were assessed. The binding relationships among circEIF6, miR-138-5p, and LIPH were analyzed. The impacts of circEIF6, miR-138-5p, and LIPH on the invasive and proliferative abilities of TPC-1 cells were examined by Transwell and EdU assays. Tumor xenograft in nude mice was established for in vivo validation of the impact of circEIF6. CircEIF6 expression was high in TC cells and tissues. Additionally, miR-138-5p was poor and LIPH level was high in TC tissues. Mechanistically, circEIF6 competitively bound to miR-138-5p to elevate LIPH via a competitive endogenous RNA mechanism. Silencing of circEIF6 reduced TPC-1 cell proliferative and invasive properties, which was annulled by further inhibiting miR-138-5p or overexpressing LIPH. Likewise, circEIF6 silencing repressed the growth of transplanted tumors, augmented miR-138-5p expression, and diminished LIPH expression in nude mice. Conclusively, circEIF6 silencing reduced LIPH level by competitive binding to miR-138-5p, thus subduing the proliferation and invasion of TPC-1 cells.

Crosstalk between circRNAs and the PI3K/AKT and/or MEK/ERK signaling pathways in digestive tract malignancy progression

Evidence indicates that circular RNAs (circRNAs) may play an important role in regulating gene expression by binding to miRNAs through miRNA response elements. circRNAs are formed by back-splicing and have a covalently closed structure. The biogenesis of circRNAs also appears to be regulated by certain cell-specific and/or gene-specific mechanisms, and thus some circRNAs are tissue specific and tumor-expression specific. Furthermore, the high stability and tissue specificity of circRNAs may be of value for early diagnosis, survival prediction and precision medicine. This review summarizes current knowledge regarding the classification and functions of circRNAs and the role of circRNAs in regulating the PI3K/AKT and/or MEK/ERK signaling pathways in digestive tract malignancy tumors.

Prognostic, Diagnostic, and Clinicopathological Significance of Circular RNAs in Pancreatic Cancer: A Systematic Review and Meta-Analysis

Pancreatic cancer (PC) is a highly aggressive malignant tumor with a high mortality rate. It is urgent to find optimal molecular targets for the early diagnosis and treatment of PC. Here, we aimed to systematically analyze the prognostic, diagnostic, and clinicopathological significance of circular RNAs (circRNAs) in PC. Relevant studies were screened through PubMed, Web of Science, and other databases. The prognostic value of PC-associated circRNAs was assessed using the composite hazard ratio (HR), the diagnostic performance was assessed using the area under the summary receiver operator characteristic (SROC) curve (AUC), and the correlation with clinicopathological characteristics using the composite odds ratio (OR) was explored. In our study, 48 studies were included: 34 for prognosis, 11 for diagnosis, and 30 for correlation with clinicopathological characteristics. For prognosis, upregulated circRNAs were associated with poorer overall survival (OS) (HR = 2.02) and disease-free survival/progression-free survival (HR = 1.84) while downregulated circRNAs were associated with longer OS (HR = 0.55). Notably, the combination of circRNAs, including hsa_circ_0064288, hsa_circ_0000234, hsa_circ_0004680, hsa_circ_0071036, hsa_circ_0000677, and hsa_circ_0001460, was associated with worse OS (HR = 2.35). For diagnosis, the AUC was 0.83, and the pooled sensitivity and specificity were 0.79 and 0.73, respectively. For clinicopathologic characteristics, upregulated circRNAs were associated with poorer tumor differentiation, more nerve and vascular invasion, higher T stage, lymphatic metastasis, distant metastasis, advanced TNM stage, and higher preoperative CA19-9 level. In contrast, downregulated circRNAs were negatively associated with PC differentiation and lymphatic metastasis. Overall, our results showed that circRNAs are closely related to the prognosis and clinicopathological characteristics of PC patients and could be utilized for early diagnosis; thus, they are promising biomarkers for clinical application in PC.

Roles of circular RNAs in the pathogenesis and treatment of pancreatic cancer

Circular RNAs are single-stranded RNAs with a covalently closed structure formed by the process of back-splicing. Aberrant expression of circular RNAs contributes to the pathogenesis of a wide range of cancers. Pancreatic cancer is one of the most lethal cancers due to diagnostic difficulties and limited therapeutic options. Circular RNAs are emerging as novel diagnostic biomarkers and therapeutic targets for pancreatic cancer. Moreover, recent advances in the therapeutic application of engineered circular RNAs have provided a promising approach to overcoming pancreatic cancer. This review discusses the roles of circular RNAs in the pathogenesis of pancreatic cancer and in potential treatment applications and their usefulness as diagnostic biomarkers.

Circ_0058058 Drives the Malignant Phenotypes and Immune Evasion of Pancreatic Cancer by the MicroRNA-557-Dependent Regulation of PDL1

OBJECTIVES

Pancreatic cancer (PC) is one of the most deadly malignancies in the world. Recently, circular RNAs play crucial roles in PC progression. However, the functions of circ_0058058 in PC are barely known.

METHODS

The expression of circ_0058058, microRNA-557-5p (miR-557), and programmed cell death receptor ligand 1 (PDL1) was detected by quantitative real-time polymerase chain reaction. Functional experiments were implemented to disclose the effect of circ_0058058 deficiency on PC cell proliferation, apoptosis, invasion, angiogenesis, and immune escape. The binding relationship between miR-557 and circ_0058058 or PDL1 was identified by dual-luciferase reporter assay and RNA immunoprecipitation assay. In vivo assay was used to disclose the impact of circ_0058058 silencing on tumor formation in vivo.

RESULTS

Circ_0058058 was highly expressed in PC tissues and cell lines. Knockdown of circ_0058058 repressed cell proliferation, invasion, angiogenesis, and immune escape while contributed to apoptosis in PC cells. Mechanically, circ_0058058 worked as a molecular sponge of miR-557 to regulate PDL1 expression. Moreover, circ_0058058 showed a promotional effect on tumor growth in vivo.

CONCLUSIONS

Our findings suggested that circ_0058058 served as miR-557 sponge to upregulate PDL1, thereby triggering PC proliferation, invasion, angiogenesis, and immune escape.

Circular RNAs Involved in the Regulation of the Age-Related Pathways

Circular RNAs (circRNAs) are a class of covalently circular noncoding RNAs that have been extensively studied in recent years. Aging is a process related to functional decline that is regulated by signal transduction. An increasing number of studies suggest that circRNAs can regulate aging and multiple age-related diseases through their involvement in age-related signaling pathways. CircRNAs perform several biological functions, such as acting as miRNA sponges, directly interacting with proteins, and regulating transcription and translation to proteins or peptides. Herein, we summarize research progress on the biological functions of circRNAs in seven main age-related signaling pathways, namely, the insulin-insulin-like, PI3K-AKT, mTOR, AMPK, FOXO, p53, and NF-κB signaling pathways. In these pathways, circRNAs mainly function as miRNA sponges. In this review, we suggest that circRNAs are widely involved in the regulation of the main age-related pathways and are potential biomarkers for aging and age-related diseases.

Circ_0060055 Promotes the Growth, Invasion, and Radioresistance of Glioblastoma by Targeting MiR-197-3p/API5 Axis

Circular RNA (circRNA) has been shown to be involved in the regulation of human disease progression. Our study aims to reveal the role of circ_0060055 in the progression of glioblastoma (GBM) and its potential molecular mechanism. The expression of circ_0060055, microRNA (miR)-197-3p, and apoptosis inhibitor 5 (API5) was determined by quantitative real-time PCR. GBM cell proliferation, apoptosis, and invasion were assessed using cell counting kit 8 assay, colony formation assay, EdU assay, flow cytometry, and transwell assay. Besides, the radiosensitivity of cells also was assessed using colony formation assay. The interaction between miR-197-3p and circ_0060055 or API5 was analyzed by dual-luciferase reporter assay and RNA pull-down assay. Animal experiments were conducted to measure the effect of circ_0060055 on GBM tumor growth and radiosensitivity in vivo. Circ_0060055 was overexpressed in GBM tumor tissues and cells, and its silencing suppressed GBM cell proliferation and invasion, while promoted apoptosis and radiosensitivity. In terms of mechanism, circ_0060055 could interact with miR-197-3p, and miR-197-3p could target API5. API5 expression also could be positively regulated by circ_0060055. Function experiments suggested that miR-197-3p inhibitor abolished the effect of circ_0060055 knockdown on GBM cell growth, invasion, and radiosensitivity. MiR-197-3p repressed GBM cell progression and improved radiosensitivity, and this effect was eliminated by API5 upregulation. In vivo experiments confirmed that circ_0060055 knockdown reduced GBM tumor growth and enhanced the radiosensitivity of tumors. This study revealed that circ_0060055 contributed to GBM progression and radioresistance through miR-197-3p/API5 pathway, providing a potential target for GBM treatment.

MicroRNAs in the Regulation of Solute Carrier Proteins Behind Xenobiotic and Nutrient Transport in Cells

Altered metabolism, such as aerobic glycolysis or the Warburg effect, has been recognized as characteristics of tumor cells for almost a century. Since then, there is accumulating evidence to demonstrate the metabolic reprogramming of tumor cells, addiction to excessive uptake and metabolism of key nutrients, to support rapid proliferation and invasion under tumor microenvironment. The solute carrier (SLC) superfamily transporters are responsible for influx or efflux of a wide variety of xenobiotic and metabolites that are needed for the cells to function, as well as some medications. To meet the increased demand for nutrients and energy, SLC transporters are frequently dysregulated in cancer cells. The SLCs responsible for the transport of key nutrients for cancer metabolism and energetics, such as glucose and amino acids, are of particular interest for their roles in tumor progression and metastasis. Meanwhile, rewired metabolism is accompanied by the dysregulation of microRNAs (miRNAs or miRs) that are small, noncoding RNAs governing posttranscriptional gene regulation. Studies have shown that many miRNAs directly regulate the expression of specific SLC transporters in normal or diseased cells. Changes of SLC transporter expression and function can subsequently alter the uptake of nutrients or therapeutics. Given the important role for miRNAs in regulating disease progression, there is growing interest in developing miRNA-based therapies, beyond serving as potential diagnostic or prognostic biomarkers. In this article, we discuss how miRNAs regulate the expression of SLC transporters and highlight potential influence on the supply of essential nutrients for cell metabolism and drug exposure toward desired efficacy.

The Role of SLC7A11 in Cancer: Friend or Foe?

SLC7A11 controls the uptake of extracellular cystine in exchange for glutamate at a ratio of 1:1, and it is overexpressed in a variety of tumours. Accumulating evidence has shown that the expression of SLC7A11 is fine-tuned at multiple levels, and plays diverse functional and pharmacological roles in tumours, such as cellular redox homeostasis, cell growth and death, and cell metabolism. Many reports have suggested that the inhibition of SLC7A11 expression and activity is favourable for tumour therapy; thus, SLC7A11 is regarded as a potential therapeutic target. However, emerging evidence also suggests that on some occasions, the inhibition of SLC7A11 is beneficial to the survival of cancer cells, and confers the development of drug resistance. In this review, we first briefly introduce the biological properties of SLC7A11, including its structure and physiological functions, and further summarise its regulatory network and potential regulators. Then, focusing on its role in cancer, we describe the relationships of SLC7A11 with tumourigenesis, survival, proliferation, metastasis, and therapeutic resistance in more detail. Finally, since SLC7A11 has been linked to cancer through multiple approaches, we propose that its contribution and regulatory mechanism require further elucidation. Thus, more personalised therapeutic strategies should be adapted when targeting SLC7A11.

Biological functions, mechanisms, and clinical significance of circular RNA in pancreatic cancer: a promising rising star

Pancreatic cancer (PC) is a highly malignant solid tumor with insidious onset and easy early metastasis. Despite tremendous efforts devoted to research in this field, the mechanisms underlying PC tumorigenesis and progression remain unclear. Additionally, robust biomarkers and satisfactory therapeutic strategies for clinical use in PC patients are still lacking. Circular RNAs (circRNAs) are a new type of non-coding RNA originating from precursor messenger RNAs, with a covalent continuous closed-loop structure, strong stability and high specificity. Accumulating evidence suggests that circRNAs may participate in PC development and progression. Abnormal expression of circRNAs in PC is considered a vital factor that affects tumor cell proliferation, migration, invasion, apoptosis, angiogenesis and drug resistance. In this review of relevant articles published in recent years, we describe the basic knowledge concerning circRNAs, including their classification, biogenesis, functions and research approaches. Moreover, the biological roles and clinical significance of circRNAs related to PC are discussed. Finally, we note the questions remaining from recent studies and anticipate that further investigations will address these gaps in knowledge in this field. In conclusion, we expect to provide insights into circRNAs as potential targets for specific PC diagnosis and treatment in the future.

Long noncoding RNA regulatory factor X3- antisense RNA 1 promotes non-small cell lung cancer via the microRNA-577/signal transducer and activator of transcription 3 axis

Lung cancer is the most frequent malignancy, and non-small cell lung cancer (NSCLC) is its most common pathological type. Molecular targeted therapy has been testified to be effective in intervening in the occurrence and development of malignancies. This study investigates the effect of lncRNA Regulatory Factor X3- antisense RNA 1 (RFX3-AS1) in NSCLC progression. The RFX3-AS1 profile in NSCLC tissues and cells was measured by quantitative reverse transcription PCR (qRT-PCR). The RFX3-AS1 overexpression model was constructed. The cell counting kit-8 (CCK-8) experiment and cell colony formation assay were adopted to test cell viability. The cell apoptosis was determined by flow cytometry (FCM). Cell migration and invasion were monitored by the Transwell assay, and Western blot was implemented to verify the protein profiles of signal transducer and activator of transcription 3 (STAT3), E-cadherin, Vimentin and N-cadherin. In vivo, we validated the impact of RFX3-AS1 overexpression on the NSCLC xenograft mouse model. The targeting relationships between RFX3-AS1 and miR-577, miR-577 and STAT3 were confirmed by the dual-luciferase reporter assay. The results manifested that overexpressing RFX3-AS1 markedly facilitated NSCLC cell proliferation, migration, invasion and epithelial-mesenchymal transition (EMT), and suppressed cell apoptosis. In contrast, miR-577, which was a downstream target of RFX3-AS1, dramatically impeded the malignant biological behaviors of NSCLC cells. STAT3 was a direct target of miR-577, and it was negatively regulated by the latter. STAT3 activation reversed miR-577-mediated anti-tumor roles. In brief, RFX3-AS1 aggravated NSCLC progression by regulating the miR-577/STAT3 axis.

Hsa-miR-557 Inhibits Osteosarcoma Growth Through Targeting KRAS

Objective: Osteosarcoma is the most common malignancy in the skeletal system; studies showed an important role of miRNAs in tumorigenesis, indicating miRNAs as possible therapeutic molecules. This study found abnormal hsa-miR-557 expression levels in osteosarcoma and tried to explore the potential function and the mechanism.

Methods: Differential expression genes of osteosarcoma were analyzed using GSE28423 from the GEO database. Survival analysis of miRNAs was conducted with data obtained from the TARGET-OS database. STRING and miRDIP were used to predict target genes of hsa-miR-557; KRAS was then verified using dual-luciferase reporter assay. Expression of genes was detected by qPCR, and levels of proteins were detected by Western blot. The proliferation ability of cells was detected by CCK-8 and cell cycle analysis. Tumor formation assay in nude mice was used to detect the influence of osteosarcoma by hsa-miR-557 in vivo.

Results: Analysis from the GEO and TARGET databases found 12 miRNAs that are significantly related to the osteosarcoma prognosis, 7 downregulated (hsa-miR-140-3p, hsa-miR-564, hsa-miR-765, hsa-miR-1224-5p, hsa-miR-95, hsa-miR-940, and hsa-miR-557) and 5 upregulated (hsa-miR-362-3p, hsa-miR-149, hsa-miR-96, hsa-miR-744, and hsa-miR-769-5p). CCK-8 analysis and cell cycle analysis found that hsa-miR-557 could significantly inhibit the proliferation of osteosarcoma cells. The tumor formation assay in nude mice showed that tumor sizes and weights were inhibited by hsa-miR-557 transfection. Further studies also proved that hsa-miR-557 could target the 3′UTR of KRAS and modulate phosphorylation of downstream proteins.

Conclusion: This study showed that hsa-miR-557 could inhibit osteosarcoma growth both in vivo and in vitro, by modulating KRAS expression.

Crosstalk between circRNAs and the PI3K/AKT signaling pathway in cancer progression

Circular RNAs (circRNAs), covalently closed noncoding RNAs, are widely expressed in eukaryotes and viruses. They can function by regulating target gene expression, linear RNA transcription and protein generation. The phosphoinositide 3-kinase (PI3K)/AKT signaling pathway plays key roles in many biological and cellular processes, such as cell proliferation, growth, invasion, migration, and angiogenesis. It also plays a pivotal role in cancer progression. Emerging data suggest that the circRNA/PI3K/AKT axis modulates the expression of cancer-associated genes and thus regulates tumor progression. Aberrant regulation of the expression of circRNAs in the circRNA/PI3K/AKT axis is significantly associated with clinicopathological characteristics and plays an important role in the regulation of biological functions. In this review, we summarized the expression and biological functions of PI3K-AKT-related circRNAs in vitro and in vivo and assessed their associations with clinicopathological characteristics. We also further discussed the important role of circRNAs in the diagnosis, prognostication, and treatment of cancers.

Solute carrier family 16 member 5 downregulation and its methylation might serve as a prognostic indicator of prostate cancer

Prostate cancer (PCa), characterized by high invasion, metastasis, and recurrence, is the most prevalent malignant tumor in men worldwide. A clear understanding of the underlying molecular mechanisms and their role during PCa tumorigenesis can help develop prognostic and targeted therapies. We analyzed datasets from public databases, including the Cancer Genome Atlas (TCGA) and Oncomine and Gene Expression Profiling Interactive Analysis for differential expression of solute carrier family 16 member 5 (SLC16A5). We further investigated its relationship with clinical stage, pathological grade, and prognosis of PCa. The promoter methylation level of SLC16A5 in PCa was also investigated by UALCAN. We also utilized datasets from UCSC Xena to explore the prognostic role of SLC16A5 methylation levels and CpG site. Correlations between SLC16A5 and immune infiltration were discovered through TIMER. We observed significantly lower levels of SLC16A5 mRNA in PCa relative to normal tissues across six datasets from Oncomine database (p < .001) and 498 cases from TCGA database (p < .0001). SLC16A5 is strongly negatively regulated by its DNA methylation, with a Spearman of -0.81 and Pearson of -0.80 (p < .001). The aberrant SLC16A5 expression resulted in a significant relationship with clinical stage, pathological grade, and lower SLC16A5 mRNA expression, and its hypermethylation was related to a poorer PCa prognosis. SLC16A5 acted as an important factor for PCa diagnosis, with an AUC of 0.9038 (95% CI: 0.8597-0.9479; p < .0001). Besides, the aberrant SLC16A5 expression revealed close correlations with multiple immune cells. Overall, these results indicate that decreased SLC16A5 expression might be a potential biomarker for determining prognosis and immune infiltration in PCa. The positive SLC16A5 modulation might be a promising therapeutic target for PCa.

A novel circ_0099999/miR-330-5p/FSCN1 ceRNA crosstalk in pancreatic cancer

BACKGROUND

Pancreatic cancer is a lethal malignancy in both sexes throughout the world. Circular RNAs (circRNAs) have been implicated in the development of pancreatic cancer by operating as competing endogenous RNAs (ceRNAs). Here, we explored circ_0099999-mediated ceRNA activity in regulating pancreatic tumorigenesis.

METHODS

Ribonuclease R (RNase R) and subcellular localization assays were utilized to characterize circ_0099999. The levels of circ_0099999, microRNA (miR)-330-5p, and fascin actin-bundling protein 1 (FSCN1) were gauged by quantitative real-time PCR (qRT-PCR) and western blot. Cell proliferation, colony formation, apoptosis, migration, and invasion were evaluated by the Cell Counting Kit-8 (CCK-8), colony formation, flow cytometry, and transwell assays, respectively. The levels of glucose consumption and lactate production were determined using the assay kits. A direct relationship between miR-330-5p and circ_0099999 or FSCN1 was validated by dual-luciferase reporter assay. Tumour xenograft assays were used to analyse the role of circ_0099999 in vivo.

RESULTS

Circ_0099999 was highly up-regulated in pancreatic cancer tissues and cells. Knockdown of circ_0099999 impeded cell proliferation, migration, invasion, glycolysis, and promoted apoptosis in vitro, as well as diminished tumour growth in vivo. Circ_0099999 targeted miR-330-5p, and miR-330-5p was a downstream mediator of circ_0099999 function. FSCN1 was a direct and functional target of miR-330-5p. Furthermore, circ_0099999 operated as a ceRNA for miR-330-5p to modulate FSCN1 expression.

CONCLUSIONS

Our findings established a novel causal mechanism, circ_0099999/miR-330-5p/FSCN1 ceRNA crosstalk, in regulating pancreatic carcinogenesis and provided that inhibition of circ_0099999 might have therapeutic benefits in pancreatic cancer.

Non-Coding RNAs in Pancreatic Cancer Diagnostics and Therapy: Focus on lncRNAs, circRNAs, and piRNAs

Simple Summary

Pancreatic cancer is the seventh leading cause of cancer related death worldwide. In the United States, pancreatic cancer remains the fourth leading cause of cancer related death. The lack of early diagnosis and effective therapy contributes to the high mortality of pancreatic cancer. Therefore, there is an urgent need to find novel and effective biomarkers for the diagnosis and treatment of pancreatic cancer. Long noncoding RNA, circular RNAs and piwi-interacting RNA are non-coding RNAs and could become new biomarkers for the diagnosis, prognosis, and treatment of pancreatic cancer. We summarize the new findings on the roles of these non-coding RNAs in pancreatic cancer diagnosis, prognosis and targeted therapy.

Abstract

Pancreatic cancer is an aggressive malignance with high mortality. The lack of early diagnosis and effective therapy contributes to the high mortality of this deadly disease. For a long time being, the alterations in coding RNAs have been considered as major targets for diagnosis and treatment of pancreatic cancer. However, with the advances in high-throughput next generation of sequencing more alterations in non-coding RNAs (ncRNAs) have been discovered in different cancers. Further mechanistic studies have demonstrated that ncRNAs such as long noncoding RNAs (lncRNA), circular RNAs (circRNA) and piwi-interacting RNA (piRNA) play vital roles in the regulation of tumorigenesis, tumor progression and prognosis. In recent years, increasing studies have focused on the roles of ncRNAs in the development and progression of pancreatic cancer. Novel findings have demonstrated that lncRNA, circRNA, and piRNA are critically involved in the regulation of gene expression and cellular signal transduction in pancreatic cancer. In this review, we summarize the current knowledge of roles of lncRNA, circRNA, and piRNA in the diagnosis and prognosis of pancreatic cancer, and molecular mechanisms underlying the regulation of these ncRNAs and related signaling in pancreatic cancer therapy. The information provided here will help to find new strategies for better treatment of pancreatic cancer.

Circular RNAs as novel potential biomarkers for pancreatic cancer

Pancreatic cancer (PaCa) is the fourth leading cause of cancer-related deaths in the United States, and the vast majority of these malignancies are pancreatic ductal adenocarcinomas (PDAC), but there is still a lack of early detection biomarkers for PaCa. Unlike linear RNAs, circRNAs form covalently closed continuous loops and can act as mammalian gene regulators. They may be diagnostic or predictive biomarkers for some tumors, also be novel potential therapeutic targets in different diseases. This review focuses on (1) the biogenesis of circRNAs, RNA binding proteins (RBPs) and complementary sequences of circRNAs; (2) the characteristics of circRNAs which allow them to interact with miRNAs; (3) the roles of circRNAs playing in the regulation of gene expression, cell behavior and cancer, and their potential role as novel biomarkers and therapeutic targets in pancreatic cancer.

Recent Advances in the Potential Use of Circular RNA for the Diagnosis and Treatment of Pancreatic Cancer

There are few biomarkers available for the early diagnosis and prognostic evaluation of pancreatic cancer. In addition, the development of targeted therapy for pancreatic cancer is an unmet need due to the lack of molecular targets. With the continuous progress in circular RNA (circRNA)-related research, its role in the occurrence and development of pancreatic cancer has been discovered and gradually recognized. Therefore, circRNA may represent a novel marker for early diagnosis of this disease and a focus of targeted clinical therapy. CircRNA is a type of non-coding RNA with a closed circular structure formed by covalent bonds. Some circRNAs can act as "sponges" to adsorb microRNAs (miRNAs) and play the role of competitive endogenous RNA (ceRNA) to remove their inhibitory effects on the target genes of miRNA. Thus, they can indirectly restore the expression of target genes. The circRNA-miRNA-mRNA network plays a regulatory role in the proliferation, invasion, metastasis, and other biological behaviors of pancreatic cancer. Given the recent advances in circRNA, this review seeks to provide an overview of the biological function of circRNA and highlights the recent research progress regarding the molecular mechanism of circRNA for the clinical diagnosis and treatment of pancreatic cancer.