The potential of circulating cell-free RNA as a cancer biomarker: challenges and opportunities

Introduction: Cancer statistics show that recent improvements in cancer management are only mildly effective in the absence of reliable biomarkers for the detection, diagnosis and monitoring of malignant disease. Recently circulating nucleic acids have been suggested as potential biomarker candidates to fill this role.

Areas covered: This review focuses on the different types of circulating RNA biomarkers under investigation, describing the latest advances in their development and application to clinical settings, as well as challenges that researchers face in the process. Immediate perspectives of the field are outlined, and authors’ recommendations on the best progression path are provided.

Expert commentary: The development of RNA-based cancer biomarkers is a thriving area of biomedical research that has progressed significantly over the last decade. However, it seems that it is now at the point, where unless several key issues are resolved, no significant progress can be made further. Currently several areas of biomarker research require re-assessment, as indicated by the latest findings regarding the biology of circulating nucleic acids and the accumulated data of their analysis using various techniques. Additionally, regulating agencies need to be working alongside researchers to facilitate faster and easier adoption of new effective biomarkers into the clinical practice.     

The potential of circulating exosomal RNA biomarkers in cancer

ABSTRACT

Introduction

There are great potentials of using exosomal RNAs (exoRNA) as biomarkers in cancers. The isolation of exoRNA requires the use of ultracentrifugation to isolate cell-free RNA followed by detection using real-time PCR, microarray, next-generation sequencing, or Nanostring nCounter system. The use of exoRNA enrichment panels has largely increased the detection sensitivity and specificity when compared to traditional diagnostic tests. Moreover, using exoRNA as biomarkers can assist the early detection of chemo and radioresistance cancer, and in turn opens up the possibility of personalized treatment to patients. Finally, exoRNA can be detected at an early stage of cancer recurrence to improve the survival rate.     

The emerging role of non-coding circulating RNA as a biomarker in renal cell carcinoma

Introduction: Bodily fluids like serum and plasma contain significant amounts of tumor-derived circulating cell-free RNA, which holds the potential to serve as diagnostic biomarker. Consequently, liquid biopsies comprising circulating cell-free RNA might help to facilitate personalized treatment strategies for patients with renal cell carcinoma (RCC).

Areas covered: The present review provides a summary of the literature obtained by a PubMed search and covers the current knowledge on circulating non-coding cell-free RNA in patients with RCC.

Expert commentary: Altered circulating microRNA and long non-coding RNAs signatures allow for the discrimination of patients with RCC and healthy individuals. On the other hand, little is known about non-coding RNA expression in benign tumors. Cell-free microRNA expression levels may help to identify patients at risk for disease recurrence. However, accurate determination of cell-free RNAs is methodologically challenging and currently no biomarker candidate has reached a sufficient level of clinical validation. Thus, short-term implementation of cell-free circulating microRNA into clinical routine seems unlikely.     

Long noncoding RNA CCDC26 as a potential predictor biomarker contributes to tumorigenesis in pancreatic cancer

Pancreatic cancer (PC) is the fourth most common cancer worldwide and has the least patient survival rate of any cancer. Emerging studies have demonstrated that long noncoding RNAs (lncRNAs) were present in cancer patients and have shown great potential as powerful markers and therapeutic targets. However, little is known about the role of lncRNAs in PC. The present study aimed to investigate the expression pattern, clinical significance and biological function of lncRNA CCDC26 (CCDC26) in PC. With quantitative real-time PCR, we analyzed CCDC26 expression levels in 40 PC patients. We found that the CCDC26 expression was significantly higher in PC tissues than in normal tissues. CCDC26 levels were correlated with tumor size, tumor number, and reduced overall survival (OS). Univariate and multivariate analysis showed that CCDC26 expression is an independent prognostic factor of OS in patients with PC. Additionally, ROC^AUC of CCDC26 was up to 0.663, implicating that CCDC26 could be a diagnostic marker for distinguishing PC from normal. Knockdown of CCDC26 expression by small interfering RNA significantly promoted growth arrest and apoptosis. Moreover, we found that the expression of CCDC26 was positively correlated with PCNA and Bcl2. Our data suggest that CCDC26 may be identified as a novel oncogene in PC, and responsible for growth and apoptosis of cancer cell, partly by regulating the PCNA and Bcl2 expression. This work provides a novel biomarker and therapeutic target of PC for cancer clinic in future.     

The potential of liquid biopsies in gastrointestinal cancer

BackgroundLiquid biopsy is a novel approach for cancer diagnosis, the value of which in human gastrointestinal (GI) cancer has been confirmed by the previous studies. This article summarized the recent advances in liquid biopsy with a focus on novel technologies and the use of it in the screening, monitoring, and treatment of human GI cancer.ContentThe concept of liquid biopsy was first used to define the detection of circulating tumor cells (CTCs) in cancer patients, and has been expanded to other biomarkers in blood and body fluids, such as circulating tumor DNA (ctDNA), extracellular vesicles (EVs) and circulating tumor RNA. If analyzed with proper and advanced techniques like next generation sequencing (NGS) or proteomics, liquid biopsies can open an enormous array of potential biomarkers. The amount changes of target biomarkers and the mutation of genetic materials provide quantitative and qualitative information, which can be utilized clinically for cancer diagnosis and disease monitoring.SummaryAs a highly efficient, minimally invasive, and cost-effective approach to diagnose and evaluate prognosis of GI cancer, liquid biopsy has lots of advantages over traditional biopsy and is promising in future clinical utility. If the challenges are overcome in the near future, liquid biopsy will become a widely available and dependable option.     

The role of small RNAs in human diseases: potential troublemaker and therapeutic tools

Small RNAs, including short interfering RNAs (siRNAs) and microRNAs (miRNAs), are ubiquitous, versatile repressors of gene expression in plants, animals, and many fungi. They can trigger destruction of homologous mRNA or inhibition of cognate mRNA translation and play an important role in maintaining the stable state of chromosome structure and regulating the expression of protein-coding genes. Furthermore, the recent research showed that there exists close relationship between small RNAs and human diseases. Several human diseases have surfaced in which miRNAs or their machinery might be implicated, such as some neurological diseases and cancers. The specificity and potency of small RNAs suggest that they might be promising as therapeutic agents. This article will review the role of small RNAs in some human diseases etiology and investigations of taking siRNAs as therapeutic tools for treating viral infection, cancer, and other diseases. We also discuss the potential of miRNAs in gene therapy.     

Detection of folate receptor‐positive circulating tumor cells as a biomarker for diagnosis,prognostication, and therapeutic monitoring in breast cancer

ObjectivesThis study is to explore the clinical significance of folate receptor‐positive circulating tumor cells (FR⁺CTC) in the early diagnosis and disease progress in patients with breast cancer.MethodsFolate receptor‐positive circulating tumor cells was enriched from peripheral blood of the patients with immunomagnetic separation method and quantitated by folate receptor on the CTC with the ligand‐targeted PCR.ResultsThe levels of FR⁺CTC were significantly higher in breast cancer patients compared with healthy controls. Detective rate of FR⁺CTC was decreased in 19 of 27 patients underwent the surgery in 2 weeks post‐operation compared with pre‐operation; statistical analysis showed the difference was significant. We also found that the combination of FR⁺CTC, CEA, CA125, and CA153 can significantly improve the diagnostic efficiency for breast cancer.ConclusionsThis study showed the detective rate of FR⁺CTC is significantly increased in the patients with breast cancer, and the detective level is associated with disease progress.     

Plasma circular RNA hsa_circ_0001821 acts as a novel diagnostic biomarker for malignant tumors

BackgroundCircular RNAs (circRNAs) can function as key regulators of oncogenic processes. The main purpose of this study was to evaluate the expression of hsa_circ_0001821 in plasma of patients with colorectal cancer (CRC) and other malignant tumors and analyze its correlations with clinical features and diagnostic values.MethodsIn total, 467 plasma samples, including samples from 80 healthy controls, were collected between 2015 and 2019 from patients at the Affiliated People''s Hospital of Ningbo University. Plasma levels of hsa_circ_0001821 were analyzed by qRT‐PCR. The diagnostic value was performed using receiver operating characteristic (ROC) curve.ResultsPlasma hsa_circ_0001821 was increased in CRC patients, and high hsa_circ_0001821 expression predicted advanced stage and unfavorable in overall survival. In addition, this study showed the upregulation of hsa_circ_0001821 in plasma of lung cancer and hepatocellular carcinoma (HCC). ROC curve showed that the region under the loop for the diagnosis of CRC, HCC, and lung cancer was 0.815, 0.692, and 0.792.ConclusionPlasma hsa_circ_0001821 possibly is a novel biological marker for malignant tumors.     

长链非编码RNA在结直肠癌诊断及预后中的研究进展

早期诊断和预后标志物的缺乏是导致结直肠癌(colorectal cancer,CRC)患者生存率低的主要原因。长链非编码RNA(long non-coding RNA,lncRNA)由于在CRC发生发展中发挥重要的作用,并且能在外周血中稳定存在,而被认为是具有潜在临床应用价值的生物标志物。     

Circular RNA hsa_circ_0000567 can be used as a promising diagnostic biomarker for human colorectal cancer

Background

Recent studies have revealed that circular RNAs are involved in the biological process of some kinds of human cancers. However, little is known about their diagnostic values and functions in colorectal cancer (CRC).

Methods

The expression levels of hsa_circ_0000567 in 102 paired CRC tissues and adjacent noncancerous tissues, 5 CRC cell lines, and a normal colorectal epithelial cell line were detected by quantitative real‐time polymerase chain reaction (qRT‐PCR). The correlations between hsa_circ_0000567 expression levels and the clinicopathological factors of patients with CRC were analyzed. Furthermore, the loss‐of‐function assay was performed to investigate the functions of hsa_circ_0000567 in vitro. Finally, a receiver operating characteristic (ROC) curve was established to evaluate the diagnostic value of hsa_circ_0000567.

Results

Hsa_circ_0000567 expression was significantly downregulated in CRC tissues and CRC cell lines. In addition, the decreased hsa_circ_0000567 expression in CRC was negatively correlated with tumor size (P = .011), lymph metastasis (P = .003), distal metastasis (P < .0001), and tumor–node–metastasis (TNM) stage (P = .003) in CRC. Moreover, knockdown of hsa_circ_0000567 promoted CRC cells proliferation and migration in vitro. Importantly, the area under the ROC curve (AUC) was 0.8653, which indicates hsa_circ_0000567 can serve as a diagnostic biomarker.

Conclusion

Hsa_circ_0000567 may be a novel suppressor and a potential diagnosis biomarker in CRC.

     

Circulating cell-free nucleic acids as biomarkers in colorectal cancer screening and diagnosis

Screening methods for the most frequent diagnosed malignant tumor, colorectal cancer (CRC), have limitations. Circulating cell-free DNA (cfDNA) analysis came into focus as a potential screening test for CRC. Detection of epigenetic and genetic alterations of cfDNA as DNA methylation or DNA mutations and related ribonucleic acids may improve cancer detection based on unique, CRC-specific patterns. In this review the authors summarize the CRC-specific nucleic acid biomarkers measured in peripheral blood and their potential as screening markers. Detection of DNA mutation has inadequate sensitivity; however, methylated DNA can be established with higher sensitivity from CRC plasma samples. The ribonucleic acid based miRNA studies represented higher sensitivity for CRC as compared with mRNA studies. Recently, isolation of cfDNA has become automated, highly reproducible and a high throughput method. With automated possible diagnostic tools, a new approach may be available for CRC screening as liquid biopsy.     

Plasma circular RNA panel acts as a novel diagnostic biomarker for colorectal cancer

BackgroundColorectal cancer (CRC) is one of the most common cancers worldwide, and emerging lines of evidence have implicated circular RNAs (circRNAs), a novel class of endogenous noncoding RNAs, in CRC development. However, whether plasma circRNAs might be novel diagnostic biomarkers for CRC remains unclear.MethodsWe investigated the plasma levels of selected circRNAs by quantitative real-time PCR (qRT-PCR). The presence of the candidate circRNAs was confirmed through RNase R assays, qRT-PCR and DNA sequencing, and their diagnostic value was evaluated using a receiver operating characteristic (ROC) curve.ResultsThe plasma levels of three circRNAs (circ-CCDC66, circ-ABCC1 and circ-STIL) were significantly decreased in CRC patients (n = 45) compared with healthy controls (n = 61). The ROC curve analysis showed that the area under the ROC curve (AUC) of the three-circRNA panel was 0.780, which is higher than that of traditional protein biomarkers, such as carcinoembryonic antigen (CEA) and carbohydrate antigen 19–9 (CA19-9). Combining the circRNA panel with CEA and CA19-9 might improve the ability to diagnose CRC (AUC = 0.855). In addition, the plasma circ-ABCC1 level was related to tumor growth and progression, and the plasma circ-CCDC66 and circ-ABCC1 levels were decreased in precursor lesions of CRC, including colon adenomas and adenomatous polyps. More importantly, circ-CCDC66 and circ-STIL were found to be useful for diagnosing early-stage CRC, and the three-circRNA panel improved the ability to diagnose CEA-negative and CA19-9-negative CRC.ConclusionOur study provides the first identification of a panel of three plasma circRNAs that could serve as a novel and independent diagnostic biomarker for CRC.     

The potential use of urine cell free DNA as a marker for cancer

Introduction: Although the role of circulating cell free DNA in cancer has been widely demonstrated, less is known about the role of urine cell free DNA (UcfDNA). UcfDNA can serve as a ‘liquid biopsy’ for urological and non-urological tumors, as it carries information on DNA from cells exfoliated in urine and from circulation.

Areas covered: We review the studies on UcfDNA as a source of biomarkers for cancer, focusing on the new techniques and the differences between urological and non-urological tumors. We searched Pubmed for articles published between 1998 and 2016 with the following key words and phrases: ‘urine’ and ‘cell free DNA’ or ‘liquid biopsy’ or ‘cancer’.

Expert commentary: Despite the few papers published on this topic, UcfDNA is an important component of ‘liquid biopsy’, a useful and non-invasive tool for cancer diagnosis, prognosis and treatment monitoring, containing a wide range of genetic information.