Extrachromosomal Circular DNAs: Origin, formation and emerging function in Cancer

Characterization, biogenesis model, and current bioinformatics of human extrachromosomal circular DNA

Human extrachromosomal circular DNA, or eccDNA, has been the topic of extensive investigation in the last decade due to its prominent regulatory role in the development of disorders including cancer. With the rapid advancement of experimental, sequencing and computational technology, millions of eccDNA records are now accessible. Unfortunately, the literature and databases only provide snippets of this information, preventing us from fully understanding eccDNAs. Researchers frequently struggle with the process of selecting algorithms and tools to examine eccDNAs of interest. To explain the underlying formation mechanisms of the five basic classes of eccDNAs, we categorized their characteristics and functions and summarized eight biogenesis theories. Most significantly, we created a clear procedure to help in the selection of suitable techniques and tools and thoroughly examined the most recent experimental and bioinformatics methodologies and data resources for identifying, measuring and analyzing eccDNA sequences. In conclusion, we highlighted the current obstacles and prospective paths for eccDNA research, specifically discussing their probable uses in molecular diagnostics and clinical prediction, with an emphasis on the potential contribution of novel computational strategies.

Differential expression and analysis of extrachromosomal circular DNAs as serum biomarkers in pulmonary arterial hypertension

BACKGROUND

Extrachromosomal circular DNAs (eccDNAs) have been reported to play a key role in the occurrence and development of various diseases. However, the characterization and role of eccDNAs in pulmonary arterial hypertension (PAH) remain unclear.

METHODS

In the discovery cohort, we first explored eccDNA expression profiles by Circle-sequencing analysis. The candidate eccDNAs were validated by routine polymerase chain reaction (PCR), TOPO-TA cloning and Sanger sequencing. In the validation cohort, 30 patients with PAH and 10 healthy controls were recruited for qPCR amplification to detect the candidate eccDNAs. Datas at the baseline were collected, including clinical background, biochemical variables, echocardiography and hemodynamic factors. Receiver operating characteristic curve was used to investigate the diagnostic effect of the eccDNA.

RESULTS

We identified a total of 21,741 eccDNAs in plasma samples of 3 IPAH patients and 3 individuals in good health, and the expression frequency, GC content, length distribution, and genome distribution of the eccDNAs were thoroughly characterized and analyzed. In the validation cohort, 687 eccDNAs were differentially expressed in patients with IPAH compared with healthy controls (screening threshold: |FC|≥2 and P < 0.05). Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that the specific eccDNAs in IPAH were significantly enriched in calcium channel activity, the mitogen-activated protein kinase pathway, and the wnt signaling pathway. Verification queue found that the expression of eccDNA-chr2:131208878-131,424,362 in PAH was considerably higher than that in healthy controls and exhibited a high level of accuracy in predicting PAH with a sensitivity of 86.67% and a specificity of 90%. Furthermore, correlation analysis disclosed a significant association between serum eccDNA-chr2:131208878-131,424,362 and mean pulmonary artery pressure (mPAP) (r = 0.396, P = 0.03), 6 min walking distance (6MWD) (r = -0.399, P = 0.029), N-terminal pro-B-type natriuretic peptide (NT-proBNP) (r = 0.685, P < 0.001) and cardiac index (CI) (r = - 0.419, P = 0.021).

CONCLUSIONS

This is the first study to identify and characterize eccDNAs in patients with PAH. We revealed that serum eccDNA-chr2:131208878-131,424,362 is significantly overexpressed and can be used in the diagnosis of PAH, indicating its potential as a novel non-invasive biomarker.

Extrachromosomal circular DNA (eccDNA): from carcinogenesis to drug resistance

Extrachromosomal circular DNA (eccDNA) is a circular form of DNA that exists outside of the chromosome. Although it has only been a few decades since its discovery, in recent years, it has been found to have a close relationship with cancer, which has attracted widespread attention from researchers. Thus far, under the persistent research of researchers from all over the world, eccDNA has been found to play an important role in a variety of tumors, including breast cancer, lung cancer, ovarian cancer, etc. Herein, we review the sources of eccDNA, classifications, and the mechanisms responsible for their biogenesis. In addition, we introduce the relationship between eccDNA and various cancers and the role of eccDNA in the generation and evolution of cancer. Finally, we summarize the research significance and importance of eccDNA in cancer, and highlight new prospects for the application of eccDNA in the future detection and treatment of cancer.

Categorizing Extrachromosomal Circular DNA as Biomarkers in Serum of Cancer

Extrachromosomal circular DNA (eccDNA), a double-stranded circular DNA molecule found in multiple organisms, has garnered an increasing amount of attention in recent years due to its close association with the initiation, malignant progression, and heterogeneous evolution of cancer. The presence of eccDNA in serum assists in non-invasive tumor diagnosis as a biomarker that can be assessed via liquid biopsies. Furthermore, the specific expression patterns of eccDNA provide new insights into personalized cancer therapy. EccDNA plays a pivotal role in tumorigenesis, development, diagnosis, and treatment. In this review, we comprehensively outline the research trajectory of eccDNA, discuss its role as a diagnostic and prognostic biomarker, and elucidate its regulatory mechanisms in cancer. In particular, we emphasize the potential application value of eccDNA in cancer diagnosis and treatment and anticipate the development of novel tumor diagnosis strategies based on serum eccDNA in the future.

Extrachromosomal Circular DNA: An Emerging Potential Biomarker for Inflammatory Bowel Diseases?

Inflammatory bowel disease (IBD) comprising ulcerative colitis and Crohn's disease is a chronic immune-mediated disease which affects the gastrointestinal tract with a relapsing and remitting course, causing lifelong morbidity. IBD pathogenesis is determined by multiple factors including genetics, immune and microbial factors, and environmental factors. Although therapy options are expanding, remission rates are unsatisfiable, and together with the disease course, response to therapy remains unpredictable. Therefore, the identification of biomarkers that are predictive for the disease course and response to therapy is a significant challenge. Extrachromosomal circular DNA (eccDNA) fragments exist in all tissue tested so far. These fragments, ranging in length from a few hundreds of base pairs to mega base pairs, have recently gained more interest due to technological advances. Until now, eccDNA has mainly been studied in relation to cancer due to its ability to act as an amplification site for oncogenes and drug resistance genes. However, eccDNA could also play an important role in inflammation, expressed both locally in the- involved tissue and at distant sites. Here, we review the current evidence on the molecular mechanisms of eccDNA and its role in inflammation and IBD. Additionally, the potential of eccDNA as a tissue or plasma marker for disease severity and/or response to therapy is evaluated.

Molecular characterization and functional roles of circulating cell-free extrachromosomal circular DNA

Circular DNA segments isolated from chromosomes are known as extrachromosomal circular DNA (eccDNA). Its distinct structure and characteristics, along with the variations observed in different disease states, makes it a promising biomarker. Recent studies have revealed the presence of eccDNAs in body fluids, indicating their involvement in various biological functions. This finding opens up avenues for utilizing eccDNAs as convenient and real-time biomarkers for disease diagnosis, treatment monitoring, and prognosis assessment through noninvasive analysis of body fluids. In this comprehensive review, we focused on elucidating the size profiles, potential mechanisms of formation and clearance, detection methods, and potential clinical applications of eccDNAs. We aimed to provide a valuable reference resource for future research in this field.

Gene amplification in neoplasia: A cytogenetic survey of 80 131 cases

Gene amplification is a crucial process in cancer development, leading to the overexpression of oncogenes. It manifests cytogenetically as extrachromosomal double minutes (dmin), homogeneously staining regions (hsr), or ring chromosomes (r). This study investigates the prevalence and distribution of these amplification markers in a survey of 80 131 neoplasms spanning hematologic disorders, and benign and malignant solid tumors. The study reveals distinct variations in the frequency of dmin, hsr, and r among different tumor types. Rings were the most common (3.4%) sign of amplification, followed by dmin (1.3%), and hsr (0.8%). Rings were particularly frequent in malignant mesenchymal tumors, especially liposarcomas (47.5%) and osteosarcomas (23.4%), dmin were prevalent in neuroblastoma (30.9%) and pancreatic carcinoma (21.9%), and hsr frequencies were highest in head and neck carcinoma (14.0%) and neuroblastoma (9.0%). Combining all three amplification markers (dmin/hsr/r), malignant solid tumors consistently exhibited higher frequencies than hematologic disorders and benign solid tumors. The structural characteristics of these amplification markers and their potential role in tumorigenesis and tumor progression highlight the complex interplay between cancer-initiating gene-level alterations, for example, fusion genes, and subsequent amplification dynamics. Further research integrating cytogenetic and molecular approaches is warranted to better understand the underlying mechanisms of these amplifications, in particular, the enigmatic question of why certain malignancies display certain types of amplification. Comparing the present results with molecular genetic data proved challenging because of the diversity in definitions of amplification across studies. This study underscores the need for standardized definitions in future work.

SURE gel electrophoresis: A method for improved detection and purification of dilute nucleic acid samples

Agarose gel electrophoresis is performed routinely by molecular biologists as both an analytical and a preparative method for characterization of nucleic acids. Gel analysis of highly dilute DNA solutions is challenging because of the limited sensitivity of detection available with conventional methods. In this study a new approach is described for concentrating samples directly within gels called SURE (successive reloading) electrophoresis. The approach involves loading of dilute samples multiple times into a single well, with each loading followed by a brief pulse of electrical current before the next sample is loaded. The procedure generates single bands created by molecular stacking that exhibit strongly enhanced signal intensities and minimal band broadening. Using optimized voltages and time intervals as many as 20 successive loadings could be performed and up to 800 μL could be loaded into a single well. Gel extraction and fluorescent quantitation demonstrated that approximately 97 % of the DNA from each loading was incorporated into the resultant band. Highly dilute DNA samples (<0.0007 ng per microliter) could be readily detected after six loadings. The method produced good results with either TAE or TBE as electrophoresis buffers, using loading dyes with or without SDS, and in both minigels and large gels.

Sequence Characterization of Extra-Chromosomal Circular DNA Content in Multiple Blackgrass (Alopecurus myosuroides) Populations

Alopecurus myosuroides (blackgrass) is a problematic weed of Western European winter wheat, and its success is largely due to widespread multiple-herbicide resistance. Previous analysis of F2 seed families derived from two distinct blackgrass populations exhibiting equivalent non-target site resistance (NTSR) phenotypes shows resistance is polygenic and evolves from standing genetic variation. Using a CIDER-seq pipeline, we show that herbicide-resistant (HR) and herbicide-sensitive (HS) F3 plants from these F2 seed families as well as the parent populations they were derived from carry extra-chromosomal circular DNA (eccDNA). We identify the similarities and differences in the coding structures within and between resistant and sensitive populations. Although the numbers and size of detected eccDNAs varied between the populations, comparisons between the HR and HS blackgrass populations identified shared and unique coding content, predicted genes, and functional protein domains. These include genes related to herbicide detoxification such as Cytochrome P450s, ATP-binding cassette transporters, and glutathione transferases including AmGSTF1. eccDNA content was mapped to the A. myosuroides reference genome, revealing genomic regions at the distal end of chromosome 5 and the near center of chromosomes 1 and 7 as regions with a high number of mapped eccDNA gene density. Mapping to 15 known herbicide-resistant QTL regions showed that the eccDNA coding sequences matched twelve, with four QTL matching HS coding sequences; only one region contained HR coding sequences. These findings establish that, like other pernicious weeds, blackgrass has eccDNAs that contain homologs of chromosomal genes, and these may contribute genetic heterogeneity and evolutionary innovation to rapidly adapt to abiotic stresses, including herbicide treatment.

Gene amplifications and extrachromosomal circular DNAs: function and biogenesis

Gene amplification is an increase in the copy number of restricted chromosomal segments that contain gene(s) and frequently results in the over-expression of the corresponding gene(s). Amplification may be found in the form of extrachromosomal circular DNAs (eccDNAs) or as linear repetitive amplicon regions that are integrated into chromosomes, which may form cytogenetically observable homogeneously staining regions or may be scattered throughout the genome. eccDNAs are structurally circular and in terms of their function and content, they can be classified into various subtypes. They play pivotal roles in many physiological and pathological phenomena such as tumor pathogenesis, aging, maintenance of telomere length and ribosomal DNAs (rDNAs), and gain of resistance against chemotherapeutic agents. Amplification of oncogenes is consistently seen in various types of cancers and can be associated with prognostic factors. eccDNAs are known to be originated from chromosomes as a consequence of various cellular events such as repair processes of damaged DNA or DNA replication errors. In this review, we highlighted the role of gene amplification in cancer, the functional aspects of eccDNAs subtypes, the proposed biogenesis mechanisms, and their role in gene or segmental-DNA amplification.

Methods for the purification and detection of single nucleotide KRAS mutations on extrachromosomal circular DNA in human plasma

BACKGROUNDS

Despite recent advances, many cancers are still detected too late for curative treatment. There is, therefore, a need for the development of new diagnostic methods and biomarkers. One approach may arise from the detection of extrachromosomal circular DNA (eccDNA), which is part of cell-free DNA in human plasma.

AIMS

First, we assessed and compared two methods for the purification of eccDNA from plasma. Second, we tested for an easy diagnostic application of eccDNA liquid biopsy-based assays.

MATERIALS & METHODS

For the comparison we tested a solid-phase silica purification method and a phenol/chloroform method with salt precipitation. For the diagnostic application of eccDNA we developed and tested a qPCR primer-based SNP detection system, for the detection of two well-established cancer-causing KRAS mutations (G12V and G12R) on circular DNA. This investigation was supported by purifying, sequencing, and analysing clinical plasma samples for eccDNAs containing KRAS mutant alleles in 0.5 mL plasma from 16 pancreatic ductal adenocarcinoma patients and 19 healthy controls.

RESULTS

In our method comparison we observed, that following exonuclease treatment a lower eccDNA yield was found for the phenol/chloroform method (15.7%-26.7%) compared with the solid-phase purification approach (47.8%-65.9%). For the diagnostic application of eccDNA tests, the sensitivity of the tested qPCR assay only reached ~10-3 in a background of 105 wild type (wt) KRAS circular entities, which was not improved by general amplification or primer-based inhibition of wt KRAS amplification. Furthermore, we did not detect eccDNA containing KRAS in any of the clinical samples.

DISCUSSION

A potential explanation for our inability to detect any KRAS mutations in the clinical samples may be related to the general low abundance of eccDNA in plasma.

CONCLUSION

Taken together our results provide a benchmark for eccDNA purification methods while raising the question of what is required for the optimal fast and sensitive detection of SNP mutations on eccDNA with greater sensitivity than primer-based qPCR detection.

Dynamics of Amino Acid Metabolism, Gene Expression, and Circulomics in a Recombinant Chinese Hamster Ovary Cell Line Adapted to Moderate and High Levels of Extracellular Lactate

The accumulation of metabolic wastes in cell cultures can diminish product quality, reduce productivity, and trigger apoptosis. The limitation or removal of unintended waste products from Chinese hamster ovary (CHO) cell cultures has been attempted through multiple process and genetic engineering avenues with varied levels of success. One study demonstrated a simple method to reduce lactate and ammonia production in CHO cells with adaptation to extracellular lactate; however, the mechanism behind adaptation was not certain. To address this profound gap, this study characterizes the phenotype of a recombinant CHO K-1 cell line that was gradually adapted to moderate and high levels of extracellular lactate and examines the genomic content and role of extrachromosomal circular DNA (eccDNA) and gene expression on the adaptation process. More than 500 genes were observed on eccDNAs. Notably, more than 1000 genes were observed to be differentially expressed at different levels of lactate adaptation, while only 137 genes were found to be differentially expressed between unadapted cells and cells adapted to grow in high levels of lactate; this suggests stochastic switching as a potential stress adaptation mechanism in CHO cells. Further, these data suggest alanine biosynthesis as a potential stress-mitigation mechanism for excess lactate in CHO cells.

Diagnostic value of circular free DNA for colorectal cancer detection

BACKGROUND

Minimally invasive or noninvasive, sensitive and accurate detection of colorectal cancer (CRC) is urgently needed in clinical practice.

AIM

To identify a noninvasive, sensitive and accurate circular free DNA marker detected by digital polymerase chain reaction (dPCR) for the early diagnosis of clinical CRC.

METHODS

A total of 195 healthy control (HC) individuals and 101 CRC patients (38 in the early CRC group and 63 in the advanced CRC group) were enrolled to establish the diagnostic model. In addition, 100 HC individuals and 62 patients with CRC (30 early CRC and 32 advanced CRC groups) were included separately to validate the model. CAMK1D was dPCR. Binary logistic regression analysis was used to establish a diagnostic model including CAMK1D and CEA.

RESULTS

To differentiate between the 195 HCs and 101 CRC patients (38 early CRC and 63 advanced CRC patients), the common biomarkers CEA and CAMK1D were used alone or in combination to evaluate their diagnostic value. The area under the curves (AUCs) of CEA and CAMK1D were 0.773 (0.711, 0.834) and 0.935 (0.907, 0.964), respectively. When CEA and CAMK1D were analyzed together, the AUC was 0.964 (0.945, 0.982). In differentiating between the HC and early CRC groups, the AUC was 0.978 (0.960, 0.995), and the sensitivity and specificity were 88.90% and 90.80%, respectively. In differentiating between the HC and advanced CRC groups, the AUC was 0.956 (0.930, 0.981), and the sensitivity and specificity were 81.30% and 95.90%, respectively. After building the diagnostic model containing CEA and CAMK1D, the AUC of the CEA and CAMK1D joint model was 0.906 (0.858, 0.954) for the validation group. In differentiating between the HC and early CRC groups, the AUC was 0.909 (0.844, 0.973), and the sensitivity and specificity were 93.00% and 83.30%, respectively. In differentiating between the HC and advanced CRC groups, the AUC was 0.904 (0.849, 0.959), and the sensitivity and specificity were 93.00% and 75.00%, respectively.

CONCLUSION

We built a diagnostic model including CEA and CAMK1D for differentiating between HC individuals and CRC patients. Compared with the common biomarker CEA alone, the diagnostic model exhibited significant improvement.

CircRNA-miRNA-VEGFA: an important pathway to regulate cancer pathogenesis

Cancers, especially malignant tumors, contribute to high global mortality rates, resulting in great economic burden to society. Many factors are associated with cancer pathogenesis, including vascular endothelial growth factor-A (VEGFA) and circular RNAs (circRNA). VEGFA is a pivotal regulator of vascular development such as angiogenesis, which is an important process in cancer development. CircRNAs have covalently closed structures, making them highly stable. CircRNAs are widely distributed and participate in many physiological and pathological processes, including modulating cancer pathogenesis. CircRNAs act as transcriptional regulators of parental genes, microRNA (miRNA)/RNA binding protein (RBP) sponges, protein templates. CircRNAs mainly function via binding to miRNAs. CircRNAs have been shown to influence different diseases such as coronary artery diseases and cancers by regulating VEGFA levels via binding to miRNAs. In this paper, we explored the origin and functional pathways of VEGFA, reviewed the current understanding of circRNA properties and action mechanisms, and summarized the role of circRNAs in regulating VEGFA during cancer pathogenesis.

The characteristics of extrachromosomal circular DNA in patients with end-stage renal disease

BACKGROUND

End-stage renal disease (ESRD) is the final stage of chronic kidney disease (CKD). In addition to the structurally intact chromosome genomic DNA, there is a double-stranded circular DNA called extrachromosomal circular DNA (eccDNA), which is thought to be involved in the epigenetic regulation of human disease. However, the features of eccDNA in ESRD patients are barely known. In this study, we identified eccDNA from ESRD patients and healthy people, as well as revealed the characteristics of eccDNA in patients with ESRD.

METHODS

Using the high-throughput Circle-Sequencing technique, we examined the eccDNA in peripheral blood mononuclear cells (PBMCs) from healthy people (NC) (n = 12) and ESRD patients (n = 16). We analyzed the length distribution, genome elements, and motifs feature of eccDNA in ESRD patients. Then, after identifying the specific eccDNA in ESRD patients, we explored the potential functions of the target genes of the specific eccDNA. Finally, we investigated the probable hub eccDNA using algorithms.

RESULTS

In total, 14,431 and 11,324 eccDNAs were found in the ESRD and NC groups, respectively, with sizes ranging from 0.01 kb to 60 kb at most. Additionally, the ESRD group had a greater distribution of eccDNA on chromosomes 4, 11, 13, and 20. In two groups, we also discovered several motifs of specific eccDNAs. Furthermore, we identified 13,715 specific eccDNAs in the ESRD group and 10,585 specific eccDNAs in the NC group, both of which were largely annotated as mRNA catalog. Pathway studies using Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) showed that the specific eccDNA in ESRD was markedly enriched in cell junction and communication pathways. Furthermore, we identified potentially 20 hub eccDNA-targeting genes from all ESRD-specific eccDNA-targeting genes. Also, we found that 39 eccDNA-targeting genes were associated with ESRD, and some of these eccDNAs may be related to the pathogenesis of ESRD.

CONCLUSIONS

Our findings revealed the characteristics of eccDNA in ESRD patients and discovered potentially hub and ESRD-relevant eccDNA-targeting genes, suggesting a novel probable mechanism of ESRD.

TeCD: The eccDNA Collection Database for extrachromosomal circular DNA

BACKGROUND

Extrachromosomal circular DNA (eccDNA) is a kind of DNA that widely exists in eukaryotic cells. Studies in recent years have shown that eccDNA is often enriched during tumors and aging, and participates in the development of cell physiological activities in a special way, so people have paid more and more attention to the eccDNA, and it has also become a critical new topic in modern biological research.

DESCRIPTION

We built a database to collect eccDNA, including animals, plants and fungi, and provide researchers with an eccDNA retrieval platform. The collected eccDNAs were processed in a uniform format and classified according to the species to which it belongs and the chromosome of the source. Each eccDNA record contained sequence length, start and end sites on the corresponding chromosome, order of the bases, genomic elements such as genes and transposons, and other information in the respective sequencing experiment. All the data were stored into the TeCD (The eccDNA Collection Database) and the BLAST (Basic Local Alignment Search Tool) sequence alignment function was also added into the database for analyzing the potential eccDNA sequences.

CONCLUSION

We built TeCD, a platform for users to search and obtain eccDNA data, and analyzed the possible potential functions of eccDNA. These findings may provide a basis and direction for researchers to further explore the biological significance of eccDNA in the future.

EccDNA-oriented ITGB7 expression in breast cancer

Background

Extrachromosomal circular DNA (eccDNA) is omnipresent in cancers and related to the progression of tumors and oncogene amplification. However, its function in breast cancer (BC) is unclear.

Methods

After constructing the DNA library, CLeavage Effects by Circularization for In vitro Reporting of sequencing was performed for eccDNA detection using 1 BC tissue sample. Fastqc was used to evaluate the quality of the original data. Burrows-Wheeler-Alignment Tool was used to compare the original data to the reference genome. A Circle-MAP was subsequently performed to detect eccDNA, and Bedtools was used to annotate the eccDNA genes. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses were conducted by ClusterProfiler. The Genotype-Tissue Expression and the Cancer Genome Atlas databases were used to collect the ribonucleic acid-sequencing data of the BC and normal samples. A Gene Expression Profiling Interactive Analysis, the University of Alabama at Birmingham CANcer data analysis Portal, and Kaplan-Meier survival curves were used to analyze the Cancer Genome Atlas data.

Results

A total of 200 eccDNA genes, including IGTB7, were obtained. About the biological processes (BPs), these 200 genes were mainly enriched in actin cytoskeleton reorganization and axon guidance. Concerning the molecular functions (MFs), these 200 genes were mainly enriched in sodium ion transmembrane transporter activity and metal ion transmembrane transporter activity. As for cellular components (CCs), these 200 genes were mainly enriched in the transcription regulator complex and focal adhesion. ITGB7 was significantly enriched in cell-matrix adhesion and localization within the membrane in the BPs, integrin binding in the MFs, and cell-substrate junction and focal adhesion in the CCs. The 200 eccDNA genes were mainly enriched in the PI3K-Akt signaling pathway and focal adhesion. Notably, ITGB7 was enriched in focal adhesion, ECM-receptor interaction, the PI3K-Akt signaling pathway, and human papillomavirus infection. Besides, ITGB7 was significantly upregulated in BC patients and was associated with the menopause status of the BC patients.

Conclusions

ITGB7 might serve as a prognostic marker for BC patients. ITGB7 has important implications for the individualized clinical treatment of BC patients.

FADD as a key molecular player in cancer progression

Cancer is a leading disease-related cause of death worldwide. Despite advances in therapeutic interventions, cancer remains a major global public health problem. Cancer pathogenesis is extremely intricate and largely unknown. Fas-associated protein with death domain (FADD) was initially identified as an adaptor protein for death receptor-mediated extrinsic apoptosis. Recent evidence suggests that FADD plays a vital role in non-apoptotic cellular processes, such as proliferation, autophagy, and necroptosis. FADD expression and activity of are modulated by a complicated network of processes, such as DNA methylation, non-coding RNA, and post-translational modification. FADD dysregulation has been shown to be closely associated with the pathogenesis of numerous types of cancer. However, the detailed mechanisms of FADD dysregulation involved in cancer progression are still not fully understood. This review mainly summarizes recent findings on the structure, functions, and regulatory mechanisms of FADD and focuses on its role in cancer progression. The clinical implications of FADD as a biomarker and therapeutic target for cancer patients are also discussed. The information reviewed herein may expand researchers’ understanding of FADD and contribute to the development of FADD-based therapeutic strategies for cancer patients.

Underlying mechanisms of epithelial splicing regulatory proteins in cancer progression

Cancer is the second-leading disease-related cause of global mortality after cardiovascular disease. Despite significant advances in cancer therapeutic strategies, cancer remains one of the major obstacles to human life extension. Cancer pathogenesis is extremely complicated and not fully understood. Epithelial splicing regulatory proteins (ESRPs), including ESRP1 and ESRP2, belong to the heterogeneous nuclear ribonucleoprotein family of RNA-binding proteins and are crucial regulators of the alternative splicing of messenger RNAs (mRNAs). The expression and activity of ESRPs are modulated by various mechanisms, including post-translational modifications and non-coding RNAs. Although a growing body of evidence suggests that ESRP dysregulation is closely associated with cancer progression, the detailed mechanisms remain inconclusive. In this review, we summarize recent findings on the structures, functions, and regulatory mechanisms of ESRPs and focus on their underlying mechanisms in cancer progression. We also highlight the clinical implications of ESRPs as prognostic biomarkers and therapeutic targets in cancer treatment. The information reviewed herein could be extremely beneficial to the development of individualized therapeutic strategies for cancer patients.

Extrachromosomal circular DNA: biogenesis, structure, functions and diseases

Extrachromosomal circular DNA (eccDNA), ranging in size from tens to millions of base pairs, is independent of conventional chromosomes. Recently, eccDNAs have been considered an unanticipated major source of somatic rearrangements, contributing to genomic remodeling through chimeric circularization and reintegration of circular DNA into the linear genome. In addition, the origin of eccDNA is considered to be associated with essential chromatin-related events, including the formation of super-enhancers and DNA repair machineries. Moreover, our understanding of the properties and functions of eccDNA has continuously and greatly expanded. Emerging investigations demonstrate that eccDNAs serve as multifunctional molecules in various organisms during diversified biological processes, such as epigenetic remodeling, telomere trimming, and the regulation of canonical signaling pathways. Importantly, its special distribution potentiates eccDNA as a measurable biomarker in many diseases, especially cancers. The loss of eccDNA homeostasis facilitates tumor initiation, malignant progression, and heterogeneous evolution in many cancers. An in-depth understanding of eccDNA provides novel insights for precision cancer treatment. In this review, we summarized the discovery history of eccDNA, discussed the biogenesis, characteristics, and functions of eccDNA. Moreover, we emphasized the role of eccDNA during tumor pathogenesis and malignant evolution. Therapeutically, we summarized potential clinical applications that target aberrant eccDNA in multiple diseases.

Emerging Role of Non-Coding RNAs in Aortic Dissection

Aortic dissection (AD) is a fatal cardiovascular acute disease with high incidence and mortality, and it seriously threatens patients’ lives and health. The pathogenesis of AD mainly includes vascular inflammation, extracellular matrix degradation, and phenotypic conversion as well as apoptosis of vascular smooth muscle cells (VSMCs); however, its detailed mechanisms are still not fully elucidated. Non-coding RNAs (ncRNAs), including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), are an emerging class of RNA molecules without protein-coding ability, and they play crucial roles in the progression of many diseases, including AD. A growing number of studies have shown that the dysregulation of ncRNAs contributes to the occurrence and development of AD by modulating the expression of specific target genes or the activity of related proteins. In addition, some ncRNAs exhibit great potential as promising biomarkers and therapeutic targets in AD treatment. In this review, we systematically summarize the recent findings on the underlying mechanism of ncRNA involved in AD regulation and highlight their clinical application as biomarkers and therapeutic targets in AD treatment. The information reviewed here will be of great benefit to the development of ncRNA-based therapeutic strategies for AD patients.

Sequence characterization of eccDNA content in glyphosate sensitive and resistant Palmer amaranth from geographically distant populations

The discovery of non-chromosomal circular DNA offers new directions in linking genome structure with function in plant biology. Glyphosate resistance through EPSPS gene copy amplification in Palmer amaranth was due to an autonomously replicating extra-chromosomal circular DNA mechanism (eccDNA). CIDER-Seq analysis of geographically distant glyphosate sensitive (GS) and resistant (GR) Palmer Amaranth (Amaranthus palmeri) revealed the presence of numerous small extra-chromosomal circular DNAs varying in size and with degrees of repetitive content, coding sequence, and motifs associated with autonomous replication. In GS biotypes, only a small portion of these aligned to the 399 kb eccDNA replicon, the vehicle underlying gene amplification and genetic resistance to the herbicide glyphosate. The aligned eccDNAs from GS were separated from one another by large gaps in sequence. In GR biotypes, the eccDNAs were present in both abundance and diversity to assemble into a nearly complete eccDNA replicon. Mean sizes of eccDNAs were similar in both biotypes and were around 5kb with larger eccDNAs near 25kb. Gene content for eccDNAs ranged from 0 to 3 with functions that include ribosomal proteins, transport, metabolism, and general stress response genetic elements. Repeat content among smaller eccDNAs indicate a potential for recombination into larger structures. Genomic hotspots were also identified in the Palmer amaranth genome with a disposition for gene focal amplifications as eccDNA. The presence of eccDNA may serve as a reservoir of genetic heterogeneity in this species and may be functionally important for survival.

Non-coding RNA in cancer drug resistance: Underlying mechanisms and clinical applications

Cancer is one of the most frequently diagnosed malignant diseases worldwide, posing a serious, long-term threat to patients’ health and life. Systemic chemotherapy remains the first-line therapeutic approach for recurrent or metastatic cancer patients after surgery, with the potential to effectively extend patient survival. However, the development of drug resistance seriously limits the clinical efficiency of chemotherapy and ultimately results in treatment failure and patient death. A large number of studies have shown that non-coding RNAs (ncRNAs), particularly microRNAs, long non-coding RNAs, and circular RNAs, are widely involved in the regulation of cancer drug resistance. Their dysregulation contributes to the development of cancer drug resistance by modulating the expression of specific target genes involved in cellular apoptosis, autophagy, drug efflux, epithelial-to-mesenchymal transition (EMT), and cancer stem cells (CSCs). Moreover, some ncRNAs also possess great potential as efficient, specific biomarkers in diagnosis and prognosis as well as therapeutic targets in cancer patients. In this review, we summarize the recent findings on the emerging role and underlying mechanisms of ncRNAs involved in cancer drug resistance and focus on their clinical applications as biomarkers and therapeutic targets in cancer treatment. This information will be of great benefit to early diagnosis and prognostic assessments of cancer as well as the development of ncRNA-based therapeutic strategies for cancer patients.

Early detection of colorectal cancer based on circular DNA and common clinical detection indicators

BACKGROUND

Colorectal cancer (CRC) is the third most common cancer worldwide, and it is the second leading cause of death from cancer in the world, accounting for approximately 9% of all cancer deaths. Early detection of CRC is urgently needed in clinical practice.

AIM

To build a multi-parameter diagnostic model for early detection of CRC.

METHODS

Total 59 colorectal polyps (CRP) groups, and 101 CRC patients (38 early-stage CRC and 63 advanced CRC) for model establishment. In addition, 30 CRP groups, and 62 CRC patients (30 early-stage CRC and 32 advanced CRC) were separately included to validate the model. 51 commonly used clinical detection indicators and the 4 extrachromosomal circular DNA markers NDUFB7, CAMK1D, PIK3CD and PSEN2 that we screened earlier. Four multi-parameter joint analysis methods: binary logistic regression analysis, discriminant analysis, classification tree and neural network to establish a multi-parameter joint diagnosis model.

RESULTS

Neural network included carcinoembryonic antigen (CEA), ischemia-modified albumin (IMA), sialic acid (SA), PIK3CD and lipoprotein a (LPa) was chosen as the optimal multi-parameter combined auxiliary diagnosis model to distinguish CRP and CRC group, when it differentiated 59 CRP and 101 CRC, its overall accuracy was 90.8%, its area under the curve (AUC) was 0.959 (0.934, 0.985), and the sensitivity and specificity were 91.5% and 82.2%, respectively. After validation, when distinguishing based on 30 CRP and 62 CRC patients, the AUC was 0.965 (0.930-1.000), and its sensitivity and specificity were 66.1% and 70.0%. When distinguishing based on 30 CRP and 32 early-stage CRC patients, the AUC was 0.960 (0.916-1.000), with a sensitivity and specificity of 87.5% and 90.0%, distinguishing based on 30 CRP and 30 advanced CRC patients, the AUC was 0.970 (0.936-1.000), with a sensitivity and specificity of 96.7% and 86.7%.

CONCLUSION

We built a multi-parameter neural network diagnostic model included CEA, IMA, SA, PIK3CD and LPa for early detection of CRC, compared to the conventional CEA, it showed significant improvement.

The FOXO family of transcription factors: key molecular players in gastric cancer

Gastric cancer (GC) is the fifth most frequently diagnosed cancer worldwide and the third leading cause of cancer-related death with an oncological origin. Despite its decline in incidence and mortality in recent years, GC remains a global public problem that seriously threatens patients' health and lives. The forkhead box O proteins (FOXOs) are a family of evolutionarily conserved transcription factors (TFs) with crucial roles in cell fate decisions. In mammals, the FOXO family consists of four members FOXO1, 3a, 4, and 6. FOXOs play crucial roles in a variety of biological processes, such as development, metabolism, and stem cell maintenance, by regulating the expression of their target genes in space and time. An accumulating amount of evidence has shown that the dysregulation of FOXOs is involved in GC progression by affecting multiple cellular processes, including proliferation, apoptosis, invasion, metastasis, cell cycle progression, carcinogenesis, and resistance to chemotherapeutic drugs. In this review, we systematically summarize the recent findings on the regulatory mechanisms of FOXO family expression and activity and elucidate its roles in GC progression. Moreover, we also highlight the clinical implications of FOXOs in GC treatment.

Extrachromosomal Circular DNA (eccDNA): From Chaos to Function

Extrachromosomal circular DNA (eccDNA) is a type of double-stranded circular DNA that is derived and free from chromosomes. It has a strong heterogeneity in sequence, length, and origin and has been identified in both normal and cancer cells. Although many studies suggested its potential roles in various physiological and pathological procedures including aging, telomere and rDNA maintenance, drug resistance, and tumorigenesis, the functional relevance of eccDNA remains to be elucidated. Recently, due to technological advancements, accumulated evidence highlighted that eccDNA plays an important role in cancers by regulating the expression of oncogenes, chromosome accessibility, genome replication, immune response, and cellular communications. Here, we review the features, biogenesis, physiological functions, potential functions in cancer, and research methods of eccDNAs with a focus on some open problems in the field and provide a perspective on how eccDNAs evolve specific functions out of the chaos in cells.

Identification of full-length circular nucleic acids using long-read sequencing technologies

Unlike the traditional perception in genomic DNA or linear RNA, circular nucleic acids are a class of functional biomolecules with a circular configuration and are often observed in nature. These circular molecules encompass the full spectrum of size and play an important role in organisms, making circular nucleic acids research worthy. Due to the low abundance of most types of circular nucleic acids and the disadvantages of short-read sequencing platforms, accurate and full-length circular nucleic acid sequencing and identification is difficult. In this review, we have provided insights into full-length circular nucleic acid detection methods using long-read sequencing technologies, with a focus on the experimental and bioinformatics strategies to obtain accurate sequences.

The Effect of Genomic DNA Contamination on the Detection of Circulating Long Non-Coding RNAs: The Paradigm of MALAT1

The presence of contaminating gDNA in RNA preparations is a frequent cause of false positives in RT-PCR-based analysis. However, in some cases, this cannot be avoided, especially when there are no exons-intron junctions in the lncRNA sequences. Due to the lack of exons in few of long noncoding RNAs (lncRNAs) and the lack of DNAse treatment step in most studies reported so far, serious questions are raised about the specificity of lncRNA detection and the potential of reporting false-positive results. We hypothesized that minute amounts of gDNA usually co-extracted with RNA could give false-positive signals since primers would specifically bind to gDNA due to the lack of junction. In the current study, we evaluated the effect of gDNA and other forms of DNA like extrachromosomal circular DNAs (eccDNAs) contamination and the importance of including a DNAse treatment step on lncRNAsexpression.As a model, we have chosen as one of the most widely studied lncRNAs in cancer namely MALAT1, which lacks exons. When we tested this hypothesis in plasma and primary tissue samples from NSCLC patients, our findings clearly indicated that results on MALAT1 expression are highly affected by the presence of DNA contamination and that the DNAse treatment step is absolutely necessary to avoid false positive results.