Circulating biomarkers to monitor cancer progression and treatment

Transcriptional Profiling of Age-Associated Gene Expression Changes in Human Circulatory CD1c+ Myeloid Dendritic Cell Subset

Immune dysfunction is a hallmark of aging and is thought to be responsible for the age-associated diseases. Dendritic cells (DCs) of the immune system function as initiators and regulators of the immune responses. Recent studies have highlighted the division of labor between various DC subsets. CD1c+ DC subset has emerged as a major inducer of CD4 T cell response. There is a scarcity of information regarding the age-associated changes in the functions of DC subsets in the elderly. Here, we investigated the changes in transcriptional profile of CD1c+ DC subset from healthy aged and young individuals using RNA sequencing. Our results suggest that majority of the genes in DCs are upregulated with age. Glucose transport, GPCR, and potassium channel genes are all upregulated in DCs from aged as compared to young indicating an enhanced activation state of DCs from aged individuals. The expression of histones, small nucleolar RNA H/ACA box (SNORA) and small nucleolar RNA C/D/box (SNORD), and long non-coding RNA (lncRNA) is also substantially upregulated in the DCs from aged. In contrast, the antigen-presenting and energy generating pathways are downregulated. In summary, DCs from aged subjects display an activated state coupled with reduced antigen presentation which may be responsible for age-associate immune dysfunction.

Translational Potential of MicroRNAs for Preoperative Staging and Prediction of Chemoradiotherapy Response in Rectal Cancer

Colorectal cancer is the third most common cancer and the second cause of cancer-related deaths. Rectal cancer presents roughly one-third of all colorectal cancer cases and differs from it on both anatomical and molecular levels. While standard treatment of colon cancer patients is radical surgery, rectal cancer is usually treated with pre-operative chemoradiotherapy followed by total mesorectal excision, which requires precise estimation of TNM staging. Unfortunately, stage evaluation is based solely on imaging modalities, and they often do not correlate with postoperative pathological findings. Moreover, approximately half of rectal cancer patients do not respond to such pre-operative therapy, so they are exposed to its toxic effects without any clinical benefit. Thus, biomarkers that could precisely predict pre-operative TNM staging, and especially response to therapy, would significantly advance rectal cancer treatment—but till now, no such biomarker has been identified. In cancer research, microRNAs are emerging biomarkers due to their connection with carcinogenesis and exceptional stability. Circulating miRNAs are promising non-invasive biomarkers that could allow monitoring of a patient throughout the whole therapeutic process. This mini-review aims to summarize the current knowledge on miRNAs and circulating miRNAs involved in the prediction of response to treatment and pre-operative staging in rectal cancer patients.

Surveillance of Tumour Development: The Relationship Between Tumour-Associated RNAs and Ribonucleases

Tumour progression is accompanied by rapid cell proliferation, loss of differentiation, the reprogramming of energy metabolism, loss of adhesion, escape of immune surveillance, induction of angiogenesis, and metastasis. Both coding and regulatory RNAs expressed by tumour cells and circulating in the blood are involved in all stages of tumour progression. Among the important tumour-associated RNAs are intracellular coding RNAs that determine the routes of metabolic pathways, cell cycle control, angiogenesis, adhesion, apoptosis and pathways responsible for transformation, and intracellular and extracellular non-coding RNAs involved in regulation of the expression of their proto-oncogenic and oncosuppressing mRNAs. Considering the diversity/variability of biological functions of RNAs, it becomes evident that extracellular RNAs represent important regulators of cell-to-cell communication and intracellular cascades that maintain cell proliferation and differentiation. In connection with the elucidation of such an important role for RNA, a surge in interest in RNA-degrading enzymes has increased. Natural ribonucleases (RNases) participate in various cellular processes including miRNA biogenesis, RNA decay and degradation that has determined their principal role in the sustention of RNA homeostasis in cells. Findings were obtained on the contribution of some endogenous ribonucleases in the maintenance of normal cell RNA homeostasis, which thus prevents cell transformation. These findings directed attention to exogenous ribonucleases as tools to compensate for the malfunction of endogenous ones. Recently a number of proteins with ribonuclease activity were discovered whose intracellular function remains unknown. Thus, the comprehensive investigation of physiological roles of RNases is still required. In this review we focused on the control mechanisms of cell transformation by endogenous ribonucleases, and the possibility of replacing malfunctioning enzymes with exogenous ones.

Liquid Biopsy in Oligometastatic Prostate Cancer-A Biologist's Point of View

Prostate cancer (PCa) is the main cause of cancer-related mortality in males and the diagnosis, treatment, and care of these patients places a great burden on healthcare systems globally. Clinically, PCa is highly heterogeneous, ranging from indolent tumors to highly aggressive disease. In many cases treatment-generally either radiotherapy (RT) or surgery-can be curative. Several key genetic and demographic factors such as age, family history, genetic susceptibility, and race are associated with a high incidence of PCa. While our understanding of PCa, which is mainly based on the tools of molecular biology-has improved dramatically in recent years, efforts to better understand this complex disease have led to the identification of a new type of PCa-oligometastatic PCa. Oligometastatic disease should be considered an individual, heterogeneous entity with distinct metastatic phenotypes and, consequently, wide prognostic variability. In general, patients with oligometastatic disease typically present less biologically aggressive tumors whose metastatic potential is more limited and which are slow-growing. These patients are good candidates for more aggressive treatment approaches. The main aim of the presented review was to evaluate the utility of liquid biopsy for diagnostic purposes in PCa and for use in monitoring disease progression and treatment response, particularly in patients with oligometastatic PCa. Liquid biopsies offer a rapid, non-invasive approach whose use t is expected to play an important role in routine clinical practice to benefit patients. However, more research is needed to resolve the many existing discrepancies with regard to the definition and isolation method for specific biomarkers, as well as the need to determine the most appropriate markers. Consequently, the current priority in this field is to standardize liquid biopsy-based techniques. This review will help to improve understanding of the biology of PCa, particularly the recently defined condition known as "oligometastatic PCa". The presented review of the body of evidence suggests that additional research in molecular biology may help to establish novel treatments for oligometastatic PCa. In the near future, the treatment of PCa will require an interdisciplinary approach involving active cooperation among clinicians, physicians, and biologists.

Peripheral blood circulating microRNA-4636/-143 for the prognosis of cervical cancer

Cervical cancer is the third leading cause of female death in the world. Serum microRNAs (miRNAs) are currently considered to be valuable as noninvasive cancer biomarkers, but their role in the prognosis of cervical cancer has not been elucidated. We aimed to find serum miRNAs that can be used as prognostic factors for cervical cancer. A traumatic pathological biopsy is the only reliable method for determining the severity of cervical cancer currently. Thus, noninvasive diagnostic markers are needed. The serological expression of candidate miRNAs were measured in 90 participants, including 60 patients with cervical cancer and 50 patients with cervical intraepithelial neoplasia. Two patients with cervical cancer were excluded from the study because of lack of data. miRNAs were evaluated by quantitative reverse transcription polymerase chain reaction. miR-143/-4636 appeared specific for cervical cancer compared with cervical intraepithelial neoplasia (P < .001). The classification performance of validated miRNAs for cervical cancer [Area under the receiver operating characteristic curve (AUC) = 0.942] was better than that reached by squamous cell carcinoma antigen (SCC-Ag; AUC = 0.727). Poor-differentiation group has lower miR-143/-4636 levels in serum (P < .05). miR-4636 level was correlated gross tumor volume and the depth of invasion (P < .0001). In our study, we found a combination of miR-143 and miR-4636 that is independently and strongly associated with cervical cancer prognosis and can be used as a clinically prognostic factor.

The Prospect and Challenges to the Flow of Liquid Biopsy in Africa

Liquid biopsy technologies have the potential to transform cancer patient management as it offers non-invasive diagnosis and real-time monitoring of disease progression and treatment responses. The use of liquid biopsy for non-invasive cancer diagnosis can have pivotal importance for the African continent where access to medical infrastructures is limited, as it eliminates the need for surgical biopsies. To apply liquid biopsy technologies in the African setting, the influence of environmental and population genetic factors must be known. In this review, we discuss the use of circulating tumor cells, cell-free nucleic acids, extracellular vesicles, protein, and other biomolecules in liquid biopsy technology for cancer management with special focus on African studies. We discussed the prospect, barriers, and other aspects that pose challenges to the use of liquid biopsy in the African continent.

Liquid Biopsy as a Tool for Differentiation of Leiomyomas and Sarcomas of Corpus Uteri

Utilization of liquid biopsy in the management of cancerous diseases is becoming more attractive. This method can overcome typical limitations of tissue biopsies, especially invasiveness, no repeatability, and the inability to monitor responses to medication during treatment as well as condition during follow-up. Liquid biopsy also provides greater possibility of early prediction of cancer presence. Corpus uteri mesenchymal tumors are comprised of benign variants, which are mostly leiomyomas, but also a heterogenous group of malignant sarcomas. Pre-surgical differentiation between these tumors is very difficult and the final description of tumor characteristics usually requires excision and histological examination. The leiomyomas and malignant leiomyosarcomas are especially difficult to distinguish and can, therefore, be easily misdiagnosed. Because of the very aggressive character of sarcomas, liquid biopsy based on early diagnosis and differentiation of these tumors would be extremely helpful. Moreover, after excision of the tumor, liquid biopsy can contribute to an increased knowledge of sarcoma behavior at the molecular level, especially on the formation of metastases which is still not well understood. In this review, we summarize the most important knowledge of mesenchymal uterine tumors, the possibilities and benefits of liquid biopsy utilization, the types of molecules and cells that can be analyzed with this approach, and the possibility of their isolation and capture. Finally, we review the typical abnormalities of leiomyomas and sarcomas that can be searched and analyzed in liquid biopsy samples with the final aim to pre-surgically differentiate between benign and malignant mesenchymal tumors.

Preanalytics and Precision Pathology: Pathology Practices to Ensure Molecular Integrity of Cancer Patient Biospecimens for Precision Medicine

Biospecimens acquired during routine medical practice are the primary sources of molecular information about patients and their diseases that underlies precision medicine and translational research. In cancer care, molecular analysis of biospecimens is especially common because it often determines treatment choices and may be used to monitor therapy in real time. However, patient specimens are collected, handled, and processed according to routine clinical procedures during which they are subjected to factors that may alter their molecular quality and composition. Such artefactual alteration may skew data from molecular analyses, render analysis data uninterpretable, or even preclude analysis altogether if the integrity of a specimen is severely compromised. As a result, patient care and safety may be affected, and medical research dependent on patient samples may be compromised. Despite these issues, there is currently no requirement to control or record preanalytical variables in clinical practice with the single exception of breast cancer tissue handled according to the guideline jointly developed by the American Society of Clinical Oncology and College of American Pathologists (CAP) and enforced through the CAP Laboratory Accreditation Program. Recognizing the importance of molecular data derived from patient specimens, the CAP Personalized Healthcare Committee established the Preanalytics for Precision Medicine Project Team to develop a basic set of evidence-based recommendations for key preanalytics for tissue and blood specimens. If used for biospecimens from patients, these preanalytical recommendations would ensure the fitness of those specimens for molecular analysis and help to assure the quality and reliability of the analysis data.

Circulating mRNA signature as a marker for high-risk prostate cancer

Prostate cancer (PCa) is the second most common cancer in men. The indolent course of the disease makes the treatment choice a challenge for physicians and patients. In this study, a minimally invasive method was used to evaluate the potential of molecular markers in identifying patients with aggressive disease. Cell-free plasma samples from 60 PCa patients collected before radical prostatectomy were used to evaluate the levels of expression of eight genes (AMACR, BCL2, NKX3-1, GOLM1, OR51E2, PCA3, SIM2 and TRPM8) by quantitative real-time PCR. Overexpression of AMACR, GOLM1, TRPM8 and NKX3-1 genes was significantly associated with aggressive disease characteristics, including extracapsular extension, tumor stage and vesicular seminal invasion. A trio of genes (GOLM1, NKX3-1 and TRPM8) was able to identify high-risk PCa cases (85% of sensitivity and 58% of specificity), yielding a better overall performance compared with the biopsy Gleason score and prostate-specific antigen, routinely used in the clinical practice. Although more studies are required, these circulating markers have the potential to be used as an additional test to improve the diagnosis and treatment decision of high-risk PCa patients.

LncRNA SAMMSON negatively regulates miR-9-3p in hepatocellular carcinoma cells and has prognostic values

In the present study, we investigated the role of lncRNA SAMMSON in hepatocellular carcinoma (HCC). We found that SAMMSON was up-regulated in HCC tissues, and patients with high levels of SAMMSON in HCC tissues had significantly lower overall rate within 5 years after admission. miR-9-3p was down-regulated in HCC tissues and inversely correlated with SAMMSON. SAMMSON expression was not significantly affected by HBV and HCV infections in HCC patients. In HCC cells, SAMMSON overexpression resulted in down-regulated miR-9-3p expression, while miR-9-3p overexpression caused no significant changes in expression levels of SAMMSON. SAMMSON overexpression led to increased, while miR-9-3p overexpression resulted in decreased migration and invasion rates of HCC cells. Therefore, SAMMSON negatively regulated miR-9-3p in HCC cells to promote cancer cell migration and invasion.

Clinical significance of cell-free DNA as a prognostic biomarker in patients with diffuse large B-cell lymphoma

Background

Cell-free DNA (cfDNA) has the potential to serve as a non-invasive prognostic biomarker in some types of neoplasia. The investigation of plasma concentration of cfDNA may reveal its use as a valuable biomarker for risk stratification of diffuse large B-cell lymphoma (DLBCL). The present prognostic value of plasma cfDNA has not been widely confirmed in DLBCL subjects. Here, we evaluated cfDNA plasma concentration and assessed its potential prognostic value as an early DLBCL diagnostic tool.

Methods

cfDNA concentrations in plasma samples from 40 patients with DLBCL during diagnosis and of 38 normal controls were determined with quantitative polymerase chain reaction (qPCR) for the multi-locus L1PA2 gene.

Results

Statistically significant elevation in plasma cfDNA concentrations was observed in patients with DLBCL as compared to that in normal controls (P<0.05). A cutoff point of 2.071 ng/mL provided 82.5% sensitivity and 62.8% specificity and allowed successful discrimination of patients with DLBCL from normal controls (area under the curve=0.777; P=0.00003). Furthermore, patients with DLBCL showing higher concentrations of cfDNA had shorter overall survival (median, 9 mo; P=0.022) than those with lower cfDNA levels. In addition, elevated cfDNA concentration was significantly associated with age, B-symptoms, International Prognostic Index (IPI) score, and different stages of disease (all P<0.05).

Conclusion

Quantification of cfDNA with qPCR at the time of diagnosis may allow identification of patients with high cfDNA concentration, which correlates with aggressive clinical outcomes and adverse prognosis.

Opportunities and challenges of circulating biomarkers in neuroblastoma

Molecular analysis of nucleic acid and protein biomarkers is becoming increasingly common in paediatric oncology for diagnosis, risk stratification and molecularly targeted therapeutics. However, many current and emerging biomarkers are based on analysis of tumour tissue, which is obtained through invasive surgical procedures and in some cases may not be accessible. Over the past decade, there has been growing interest in the utility of circulating biomarkers such as cell-free nucleic acids, circulating tumour cells and extracellular vesicles as a so-called liquid biopsy of cancer. Here, we review the potential of emerging circulating biomarkers in the management of neuroblastoma and highlight challenges to their implementation in the clinic.

Life and death of circulating cell-free DNA

Tumor-specific, circulating cell-free DNA in liquid biopsies is a promising source of biomarkers for minimally invasive serial monitoring of treatment responses in cancer management. We will review the current understanding of the origin of circulating cell-free DNA and different forms of DNA release (including various types of cell death and active secretion processes) and clearance routes. The dynamics of extracellular DNA in blood during therapy and the role of circulating DNA in pathophysiological processes (tumor-associated inflammation, NETosis, and pre-metastatic niche development) provide insights into the mechanisms that contribute to tumor development and metastases formation. Better knowledge of circulating tumor-specific cell-free DNA could facilitate the development of new therapeutic and diagnostic options for cancer management.

Tumour biomarkers-Tracing the molecular function and clinical implication

In recent years, with the increase in cancer mortality caused by metastasis, and with the development of individualized and precise medical treatment, early diagnosis with precision becomes the key to decrease the death rate. Since detecting tumour biomarkers in body fluids is the most non‐invasive way to identify the status of tumour development, it has been widely investigated for the usage in clinic. These biomarkers include different expression or mutation in microRNAs (miRNAs), circulating tumour DNAs (ctDNAs), proteins, exosomes and circulating tumour cells (CTCs). In the present article, we summarized and discussed some updated research on these biomarkers. We overviewed their biological functions and evaluated their multiple roles in human and small animal clinical treatment, including diagnosis of cancers, classification of cancers, prognostic and predictive values for therapy response, monitors for therapy efficacy, and anti‐cancer therapeutics. Biomarkers including different expression or mutation in miRNAs, ctDNAs, proteins, exosomes and CTCs provide more choice for early diagnosis of tumour detection at early stage before metastasis. Combination detection of these tumour biomarkers may provide higher accuracy at the lowest molecule combination number for tumour early detection. Moreover, tumour biomarkers can provide valuable suggestions for clinical anti‐cancer treatment and execute monitoring of treatment efficiency.

Quantification of circulating miR-517c-3p and miR-210-3p levels in preeclampsia

MicroRNAs (miRNAs, miRs) are small regulatory non-coding RNAs that regulate gene expression by incomplete complementary attachment to the 3'UTR, 5'UTR, ORF and promoter regions of target mRNAs. We compared plasma levels of miR-210-3p and miR-517c-3p as cell-free microRNAs (cfmiRNAs) in preeclamptic (n = 20) and healthy women (n = 20). These miRs are responsible for cell growth and proliferation, placental hypoxia, immune response and apoptosis. We found higher expression levels of miR-210 and miR-517c in preeclamptic cases (+3.34 and +2.27 fold change, respectively). This is the first study that evaluates the plasma levels of miR-517c in preeclamptic cases by real time PCR (RT-PCR) technique. This study can lead to new opportunities for research about the roles of miRNAs in preeclampsia etiology or new biomarkers.

Malignant pleural effusion supernatant is an alternative liquid biopsy specimen for comprehensive mutational profiling

Background

The clinical utility of malignant pleural effusion (MPE) to detect mutation has been well documented; however, routine practice of the use of MPE involves collection of the cell pellet to detect mutation, and limited studies have interrogated the MPE supernatant as an alternative source of tumor‐derived DNA for mutation profiling. In this study, we investigated the potential of MPE supernatant as a liquid biopsy specimen by comparing its mutation profile with that of matched MPE cell pellets, tissue, and plasma samples.

Methods

Sequencing data from 17 patients with matched lung tissue, plasma, and MPE samples were retrospectively analyzed. Capture‐based targeted sequencing was performed on matched plasma and MPE supernatant samples obtained from 154 patients with advanced lung adenocarcinoma.

Results

MPE supernatants had significantly higher median maximum allelic fractions (maxAFs) than their corresponding cell pellets (P = 0.008) and plasma samples (P = 0.036), and a comparable maxAF value to that of tissue samples (P = 0.675). Comparison of MPE supernatant and matched plasma samples from the larger cohort (n = 154) revealed a comparable mutation detection rate; however, MPE supernatant had a significantly higher median maxAF than plasma (20.3% vs. 1.13%; P < 0.001). Furthermore, the concordance rates between MPE supernatant and plasma for single‐nucleotide and copy number variations were 56% and 18%, respectively, suggesting that MPE supernatant reveals a more comprehensive mutation spectrum, particularly for copy number variations.

Conclusion

Overall, our study shows that MPE supernatant is an optimal alternative source of tumor‐derived DNA for comprehensive mutation profiling.

Application of Circulating Cell-Free Tumor DNA Profiles for Therapeutic Monitoring and Outcome Prediction in Genetically Heterogeneous Metastatic Melanoma

PURPOSE

Circulating cell-free tumor DNA (ctDNA) reflects the heterogeneous spectrum of tumor-specific mutations, especially in systemic disease. We validated plasma-based assays that allow the dynamic quantitative detection of ctDNA as a prognostic biomarker for tumor load and prediction of therapy response in melanoma.

MATERIALS AND METHODS

We analyzed plasma-derived ctDNA from a large training cohort (n = 96) of patients with advanced-stage melanoma, with assays for the BRAF V600E and NRAS Q61 driver mutations as well as TERT C250T and TERT C228T promoter mutations. An independent patient cohort (n = 35) was used to validate the utility of ctDNA monitoring under mitogen-activated protein kinase-targeted or immune checkpoint therapies.

RESULTS

Elevated plasma ctDNA level at baseline was an independent prognostic factor of disease progression when compared with serum S100 and lactate dehydrogenase levels in multivariable analyses (hazard ratio [HR], 7.43; 95% CI, 1.01 to 55.19; P = .05). The change in ctDNA levels during therapy correlated with treatment response, where increasing ctDNA was predictive for shorter progression-free survival (eg, for BRAF V600E ctDNA, HR, 3.70; 95% CI, 1.86 to 7.34; P < .001). Increasing ctDNA levels predicted disease progression significantly earlier than did routine radiologic scans (P < .05), with a mean lead time of 3.5 months. NRAS-mutant ctDNA was detected in a significant proportion of patients with BRAF-mutant tumors under therapy, but unexpectedly also at baseline. In vitro sensitivity studies suggested that this represents higher-than-expected intratumoral heterogeneity. The detection of NRAS Q61 ctDNA in baseline samples of patients with BRAF V600E mutation who were treated with mitogen-activated protein kinase inhibitors significantly correlated with shorter progression-free survival (HR, 3.18; 95% CI, 1.31 to 7.68; P = .03) and shorter overall survival (HR, 4.08; 95% CI, 1.57 to 10.58; P = .01).

CONCLUSION

Our results show the potential role of ctDNA measurement as a sensitive monitoring and prediction tool for the early assessment of disease progression and therapeutic response in patients with metastatic melanoma.

The functional roles of exosomes-derived long non-coding RNA in human cancer

Cancer is one of the most pervasive causes of morbidity and mortality worldwide regardless of the fact that a majority of therapeutic strategies have been constantly invented. The survival rate of cancer patients remains unsatisfactory due to the late diagnosis, frequent metastasis and poor response to chemotherapeutics. Therefore, novel methods with high specificity and susceptibility for prompt diagnosis and precise treatment of cancer are imperative. Circulating RNA is located in bodily fluids, including urine, saliva, breast milk and naturally present in blood. Recently, long non-coding RNAs (lncRNAs), a subset of non-coding RNAs are discovered to be differentially expressed in a variety of cancers. LncRNAs have been broadly recognized as emerging mediators for cancer behavior. Presence of lncRNA in circulation can be cell-free or encapsulated in extracellular vesicles (EVs) released by cancer cells. The release of EVs, especially exosomes, with 40-120 nm diameter in size, has been implicated in the regulation of malignancies as carriers for nucleic acid cargo through intercellular transfer. Therefore, systematic understanding of the role of exosomal lncRNAs in carcinogenesis may offer ideal diagnostic and prognostic biomarker or even therapeutic targets for malignancies. Herein, the underlying functional roles of exosomal lncRNAs in regulating tumor progression, immunomodulation as well as drug resistance will be elaborated. Lastly, the importance of exosomal lncRNAs in cancer study will also be discussed.

Co-expression of HIF-1α, MDR1 and LAPTM4B in peripheral blood of solid tumors

The hypoxic tumor microenvironment is the major contributor of chemotherapy resistance in solid tumors. One of the key regulators of hypoxic responses within the cell is the hypoxia inducible factor-1α (HIF-1α) that is involved in transcription of genes promoting cell survival and chemotherapy resistance. Multidrug resistance gene-1 (MDR1) and Lysosome-associated protein transmembrane 4B-35 (LAPTM4B-35) are among those notable players which augment their responses to cellular hypoxia. MDR1 is the hypoxia responsive gene involved in multidrug resistance phenotype while LAPTM4B-35 is involved in chemotherapy resistance by stabilizing HIF-1α and overexpressing MDR1. Overexpression of HIF-1α, MDR1 and LAPTM4B has been associated with poor disease outcome in many cancers when studied individually at tissue level. However, accessibility of the tissues following the course of chemotherapy for ascertaining chemotherapy resistance is difficult and sometimes not clinically feasible. Therefore, indication of hypoxic biomarkers in patient’s blood can significantly alter the clinical outcome. Hence there is a need to identify a blood based marker to understand the disease progression. In the current study the expression of hypoxia associated chemotherapy resistance genes were studied in the peripheral blood lymphocytes of solid tumor patients and any potential correlation with disease progression were explored. The expression of HIF-1α, MDR1 and LAPTM4B was studied in blood of 72 breast, 42 ovarian, 32 colon and 21 prostate cancer patients through real time PCR analysis using delta cycle threshold method. The statistical scrutiny was executed through Fisher’s Exact test and the Spearman correlation method. There was 12–13 fold increased in expression of HIF-1α, two fold increased in MDR1 and 13–14 fold increased in LAPTM4B mRNA level in peripheral blood of breast, ovarian, prostate and colon cancer patients. In the current study there was an association of HIF-1α, MDR1 and LAPTM4B expression with advanced tumor stage, metastasis and chemotherapy treated group in breast, ovarian, prostate and colon cancer patients. The Spearman analysis also revealed a positive linear association among HIF-1α, MDR1 and LAPTM4B in all the studied cancer patients. The elevated expression of HIF-1α, MDR1 and LAPTM4B in peripheral blood of solid tumor patients can be a predictor of metastasis, disease progression and treatment response in these cancers. However, larger studies are needed to further strengthen their role as a potential biomarker for cancer prognosis.

Circulating Biomarkers for Prediction of Objective Response to Chemotherapy in Pancreatic Cancer Patients

Pancreatic cancer is a lethal disease with increasing incidence. Most patients present with advanced disease, for which palliative systemic chemotherapy is the only therapeutic option. Despite improved median survival rates with FOLFIRINOX or gemcitabine chemotherapy compared to the best supportive care, many individual patients may not benefit from chemotherapy. Biomarkers are needed to predict who will benefit from chemotherapy and to monitor a patient’s response to chemotherapy. This review summarizes current research and future perspectives on circulating biomarkers for systemic chemotherapy response.

Liquid biopsy for pediatric central nervous system tumors

Central nervous system (CNS) tumors are the most common solid tumors in children, and the leading cause of cancer-related death. Over the past decade, molecular profiling has been incorporated into treatment for pediatric CNS tumors, allowing for a more personalized approach to therapy. Through the identification of tumor-specific changes, it is now possible to diagnose, assign a prognostic subgroup, and develop targeted chemotherapeutic treatment plans for many cancer types. The successful incorporation of informative liquid biopsies, where the liquid biome is interrogated for tumor-associated molecular clues, has the potential to greatly complement the precision-based approach to treatment, and ultimately, to improve clinical outcomes for children with CNS tumors. In this article, the current application of liquid biopsy in cancer therapy will be reviewed, as will its potential for the diagnosis and therapeutic monitoring of pediatric CNS tumors.

Ultrasensitive quantification of tumor mRNAs in extracellular vesicles with an integrated microfluidic digital analysis chip

Extracellular vesicles (EVs) present a promising liquid biopsy for cancer diagnosis. However, it remains a daunting challenge to quantitatively measure molecular contents of EVs including tumor-associated mRNAs. Herein, we report a configurable microwell-patterned microfluidic digital analysis platform combined with a dual-probe hybridization assay for PCR-free, single-molecule detection of specific mRNAs in EVs. The microwell array in our device is configurable between the flow-through assay mode for enhanced hybridization capture and tagging of mRNAs and the digital detection mode based on femtoliter-scale enzymatic signal amplification for single-molecule counting of surface-bound targets. Furthermore, a dual-probe hybridization assay has been developed to enhance the sensitivity of the digital single-molecule detection of EV mRNAs. Combining the merits of the chip design and the dual-probe digital mRNA hybridization assay, the integrated microfluidic system has been demonstrated to afford quantitative detection of synthetic GAPDH mRNA with a LOD as low as 20 aM. Using this technology, we quantified the level of GAPDH and EWS-FLI1 mRNAs in EVs derived from two cell lines of peripheral primitive neuroectodermal tumor (PNET), CHLA-9 and CHLA-258. Our measurements detected 64.6 and 43.5 copies of GAPDH mRNA and 6.5 and 0.277 copies of EWS-FLI1 fusion transcripts per 105 EVs derived from CHLA-9 and CHLA-258 cells, respectively. To our knowledge, this is the first demonstration of quantitative measurement of EWS-FLI1 mRNA copy numbers in Ewing Sarcoma (EWS)-derived EVs. These results highlight the ultralow frequency of tumor-specific mRNA markers in EVs and the necessity of developing highly sensitive methods for analysis of EV mRNAs. The microfluidic digital mRNA analysis platform presented here would provide a useful tool to facilitate quantitative analysis of tumor-associated EV mRNAs for liquid biopsy-based cancer diagnosis and monitoring.

Discovery and Validation of Clinical Biomarkers of Cancer: A Review Combining Metabolomics and Proteomics

Early detection and diagnosis of cancer can allow timely medical intervention, which greatly improves chances of survival and enhances quality of life. Biomarkers play an important role in assisting clinicians and health care providers in cancer diagnosis and treatment follow-up. In spite of years of research and the discovery of thousands of candidate cancer biomarkers, only a few have transitioned to routine usage in the clinic. This review highlights advances in proteomics technologies that have enabled high rates of discovery of candidate cancer biomarkers and evaluates integration with other omics technologies to improve their progress through to validation and clinical translation. Furthermore, it gauges the role of metabolomics technology in cancer biomarker research and assesses it as a complementary tool in aiding cancer biomarker discovery and validation.

Expanding the Dynamic Range of Fluorescence Assays through Single-Molecule Counting and Intensity Calibration

Surface capture assays can measure fluorescently labeled analytes across a 1000-fold concentration range and at the sub-nanomolar level, but many biological molecules exhibit 1,000,000-fold variations in abundance down to the femtomolar level. The goal of this work is to expand the dynamic range of fluorescence assays by using imaging to combine molecular counting with single-molecule calibration of ensemble intensities. We evaluate optical limits imposed by surface-captured fluorescent labels, compare performances of different fluorophore classes, and use detector acquisition parameters to span wide ranges of fluorescence irradiance. We find that the fluorescent protein phycoerythrin provides uniquely suitable properties with exceptionally intense and homogeneous single-fluorophore brightness that can overcome arbitrary spot detection threshold biases. Major limitations imposed by nonspecifically bound fluorophores were then overcome using rolling circle amplification to densely label cancer-associated miRNA biomarkers, allowing accurate single-molecule detection and calibration across nearly 5 orders of magnitude of concentration with a detection limit of 29 fM. These imaging and molecular counting strategies can be widely applied to expand the limit of detection and dynamic range of a variety of surface fluorescence assays.

Identification of Biomarkers Based on Differentially Expressed Genes in Papillary Thyroid Carcinoma

The incidence of papillary thyroid carcinoma (PTC) is increasing rapidly throughout the world. Hence, there is an urgent need for identifying more specific and sensitive biomarkers to explorate the pathogenesis of PTC. In this study, three pairs of stage I PTC tissues and matched normal adjacent tissues were sequenced by RNA-Seq, and 719 differentially expressed genes (DEGs) were screened. KEGG pathway enrichment analyses indicated that the DEGs were significantly enriched in 28 pathways. A total of 18 nodes consisting of 20 DEGs were identified in the top 10% of KEGG integrated networks. The functions of DEGs were further analysed by GO. The 13 selected genes were confirmed by qRT-PCR in 16 stage I PTC patients and by The Cancer Genome Atlas (TCGA) database. The relationship interactions between DEGs were analysed by protein-protein interaction networks and chromosome localizations. Finally, four newly discovered genes, COMP, COL3A1, ZAP70, and CD247, were found to be related with PTC clinical phenotypes, and were confirmed by Spearman’s correlation analyses in TCGA database. These four DEGs might be promising biomarkers for early-stage PTC, and provide an experimental foundation for further exploration of the pathogenesis of early-stage PTC.

Profiling of 179 miRNA Expression in Blood Plasma of Lung Cancer Patients and Cancer-Free Individuals

Lung cancer is one of major cancers, and survival of lung cancer patients is dictated by the timely detection and diagnosis. Cell-free circulating miRNAs were proposed as candidate biomarkers for lung cancer. These RNAs are frequently deregulated in lung cancer and can persist in bodily fluids for extended periods of time, shielded from degradation by membrane vesicles and biopolymer complexes. To date, several groups reported the presence of lung tumour-specific subsets of miRNAs in blood. Here we describe the profiling of blood plasma miRNAs in lung cancer patients, healthy individuals and endobronchitis patients using miRCURY LNA miRNA qPCR Serum/Plasma Panel (Exiqon). From 241 ratios differently expressed between cancer patients and healthy individuals 19 miRNAs were selected for verification using the same platform. LASSO-penalized logistic regression model, including 10 miRNA ratios comprised of 14 individual miRNAs discriminated lung cancer patients from both control groups with AUC of 0.979.

Evidence-based approaches to reduce cancer health disparities: Discover, develop, deliver, and disseminate

The Texas Center for Health Disparities (TCHD) at the University of North Texas Health Science Center is a National Institute on Minority Health and Health Disparities-funded, specialized center of excellence for health disparities. TCHD organized its 12^th annual conference focusing on "Evidence-Based Approaches to Reduce Cancer Health Disparities: Discover, Develop, Deliver, and Disseminate." At this conference, experts in health care, biomedical sciences, and public health gathered to discuss the current status and strategies for reducing cancer health disparities. The meeting was conducted in three sessions on breast cancer, prostate cancer, and colorectal cancer disparities, in addition to roundtable discussions and a poster session. Each session highlighted differences in the effects of cancer, based on factors such as race/ethnicity, gender, socioeconomic status, and geographical location. In each session, expert speakers presented their findings, and this was followed by a discussion panel made up of experts in that field and cancer survivors, who responded to questions from the audience. This article summarizes the approaches to fundamental, translational, clinical, and public health issues in cancer health disparities discussed at the conference.

Extracellular vesicles: the growth as diagnostics and therapeutics; a survey

This article aims to document the growth in extracellular vesicle (EV) research. Here, we report the growth in EV-related studies, patents, and grants as well as emerging companies with major intent on exosomes. Four different databases were utilized for electronic searches of published literature: two general databases – Scopus/Elsevier and Web of Science (WoS), as well as two specialized US government databases – the USA Patent and Trademark Office and National Institutes of Health (NIH) of the Department of Health and Human Services. The applied combination of key words was carefully chosen to cover the most commonly used terms in titles of publications, patents and grants dealing with conceptual areas of EVs. Within the time frame from 1 January 2000 to 31 December 2016, limited to articles published in English, we identified output using search strategies based upon Scopus/Elsevier and WoS, patent filings and NIH Federal Reports of funded grants. Consistently, USA and UK universities are the most frequent among the top 15 affiliations/organizations of the authors of the identified records. There is clear evidence of upward streaming of EV-related publications. By documenting the growth of the EV field, we hope to encourage a roster of independent authorities skilled to provide peer review of manuscripts, evaluation of grant applications, support of foundation initiatives and corporate long-term planning. It is important to encourage EV research to further identify biomarkers in diseases and allow for the development of adequate diagnostic tools that could distinguish disease subpopulations and enable personalized treatment of patients.

Immuno-oncology from the perspective of somatic evolution

The past years have witnessed significant success for cancer immunotherapies that activate a patient's immune system against their cancer cells. At the same time our understanding of the genetic changes driving tumor evolution have progressed dramatically. The study of cancer genomes has shown that tumors are best understood as cell populations governed by the rules of evolution, leading to the emergence and spread of cell lineages with pathogenic mutations. Moreover, somatic evolution can explain the acquisition of mutations conferring drug resistance in the ever-lasting battle for reaching even fitter cell states. Here, we review the current state of the art of somatic cancer evolution and mechanisms of immune control and escape. We also revisit the principles of immunotherapy from the perspective of somatic evolution and discuss the basic rules of resistance to immunotherapies as dictated by evolution.

'Lnc'-ing Wnt in female reproductive cancers: therapeutic potential of long non-coding RNAs in Wnt signalling

Recent discoveries in the non-coding genome have challenged the original central dogma of molecular biology, as non-coding RNAs and related processes have been found to be important in regulating gene expression. MicroRNAs and long non-coding RNAs (lncRNAs) are among those that have gained attention recently in human diseases, including cancer, with the involvement of many more non-coding RNAs (ncRNAs) waiting to be discovered. ncRNAs are a group of ribonucleic acids transcribed from regions of the human genome, which do not become translated into proteins, despite having essential roles in cellular physiology. Deregulation of ncRNA expression and function has been observed in cancer pathogenesis. Recently, the roles of a group of ncRNA known as lncRNA have gained attention in cancer, with increasing reports of their oncogenic involvement. Female reproductive cancers remain a leading cause of death in the female population, accounting for almost a third of all female cancer deaths in 2016. The Wnt signalling pathway is one of the most important oncogenic signalling pathways which is hyperactivated in cancers, including female reproductive cancers. The extension of ncRNA research into their mechanistic roles in human cancers has also led to novel reported roles of ncRNAs in the Wnt pathway and Wnt-mediated oncogenesis. This review aims to provide a critical summary of the respective roles and cellular functions of Wnt-associated lncRNAs in female reproductive cancers and explores the potential of circulating cell-free lncRNAs as diagnostic markers and lncRNAs as therapeutic targets.

LINKED ARTICLES

This article is part of a themed section on WNT Signalling: Mechanisms and Therapeutic Opportunities. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.24/issuetoc.

Translating cancer epigenomics into the clinic: focus on lung cancer

Epigenetic deregulation is increasingly being recognized as a hallmark of cancer. Recent studies have identified many new epigenetic biomarkers, some of which are being introduced into clinical practice for diagnosis, molecular classification, prognosis or prediction of response to therapies. O-6-methylguanine-DNA methyltransferase gene is the most clinically advanced epigenetic biomarker as it predicts the response to temozolomide and carmustine in gliomas. Therefore, epigenomics may represent a novel and promising tool for precision medicine, and in particular, the detection of epigenomic biomarkers in liquid biopsies will be of great interest for monitoring diseases in patients. Of particular relevance is the identification of epigenetic biomarkers in lung cancer, one of the most prevalent and deadly types of cancer. DNA methylation of SHOX2 and RASSF1A could be used as diagnostic markers to differentiate between normal and tumor samples. MicroRNA and long noncoding RNA signatures associated with lung cancer development or tobacco smoke have also been identified. In addition to the field of biomarkers, therapeutic approaches using DNA methylation and histone deacetylation inhibitors are being tested in clinical trials for several cancer types. Moreover, new DNA editing techniques based on zinc finger and CRISPR/Cas9 technologies allow specific modification of aberrant methylation found in oncogenes or tumor suppressor genes. We envision that epigenomics will translate into the clinical field and will have an impact on lung cancer diagnosis/prognosis and treatment.

Circulating microRNAs in patients with hormone receptor-positive, metastatic breast cancer treated with dovitinib

BACKGROUND

Serial analysis of biomarkers in the circulation of patients undergoing treatment ("liquid biopsies") can provide new insights into drug effects. In particular the analysis of cell-free, circulating nucleic acids such as microRNAs (miRs) can reveal altered expression patterns indicative of mechanism of drug action, cancer growth, and tumor-stroma interactions.

RESULTS

Here we analyzed plasma miRs in patients with hormone receptor positive, metastatic breast cancer with prior disease progression during aromatase inhibitor therapy (n = 8) in a phase I/II trial with the multiple tyrosine kinase inhibitor dovitinib (TKI258). Plasma miR levels were measured by quantitative RT-qPCR before and after treatment with dovitinib. A candidate miR signature of drug response was established from a 379 miR screen for detectable plasma miRs as well as from the published literature. Changes in miR expression patterns and tumor sizes were compared. In this analysis we identified miR-21-5p, miR-100-5p, miR-125b-5p, miR-126-3p, miR-375 and miR-424-5p as potential indicators of a response to dovitinib. The altered expression patterns observed for the six circulating miRs separated patients with resistant disease from those with drug responsive disease. There was no relationship between adverse effects of dovitinib treatment and identifiable changes in miR patterns.

CONCLUSION

We conclude that changes in the expression patterns of circulating miRs can be indicators of drug responses that merit prospective studies for validation.

Circulating mRNAs and miRNAs as candidate markers for the diagnosis and prognosis of prostate cancer

Circulating nucleic acids are found in free form in body fluids and may serve as minimally invasive tools for cancer diagnosis and prognosis. Only a few studies have investigated the potential application of circulating mRNAs and microRNAs (miRNAs) in prostate cancer (PCa). The Cancer Genome Atlas (TCGA) database was used for an in silico analysis to identify circulating mRNA and miRNA as potential markers of PCa. A total of 2,267 genes and 49 miRNAs were differentially expressed between normal and tumor samples. The prediction analyses of target genes and integrative analysis of mRNA and miRNA expression revealed eleven genes and eight miRNAs which were validated by RT-qPCR in plasma samples from 102 untreated PCa patients and 50 cancer-free individuals. Two genes, OR51E2 and SIM2, and two miRNAs, miR-200c and miR-200b, showed significant association with PCa. Expression levels of these transcripts distinguished PCa patients from controls (67% sensitivity and 75% specificity). PCa patients and controls with prostate-specific antigen (PSA) ≤ 4.0 ng/mL were discriminated based on OR51E2 and SIM2 expression levels. The miR-200c expression showed association with Gleason score and miR-200b, with bone metastasis, bilateral tumor, and PSA > 10.0 ng/mL. The combination of circulating mRNA and miRNA was useful for the diagnosis and prognosis of PCa.

Circulating cell-free DNA mutation patterns in early and late stage colon and pancreatic cancer

Cancer is a heterogeneous disease harboring diverse subclonal populations that can be discriminated by their DNA mutations. Environmental pressure selects subclones that ultimately drive disease progression and tumor relapse. Circulating cell-free DNA (ccfDNA) can be used to approximate the mutational makeup of cancer lesions and can serve as a marker for monitoring disease progression at the molecular level without the need for invasively acquired samples from primary or metastatic lesions. This potential for molecular analysis makes ccfDNA attractive for the study of clonal evolution and for uncovering emerging therapeutic resistance or sensitivity. We assessed ccfDNA from colon and pancreatic adenocarcinoma patients using next generation sequencing of 56 cancer-associated genes at the time of primary resectable disease and metastatic progression and compared this to the mutational patterns of the primary tumor. 28%-47% of non-synonymous mutations in the primary tumors were also detected in the ccfDNA while 71%-78% mutations found in ccfDNA were not detected in the primary tumors. ccfDNA collected at the time of progression harbored 3-5 new mutations not detected in ccfDNA at the earlier collection time points. We conclude that incorporation of ccfDNA analysis provides crucial insights into the changing molecular makeup of progressive colon and pancreatic cancer.

Biological Markers in Nursing Research

INTRODUCTION

Biobehavioral research requires the ability to objectively measure the presence and/or severity of disease, symptoms and their burden, or to determine the effect of treatment on outcomes. Biomarker research has advanced care for patients across the lifespan. There have been significant advancements in biological marker use for nursing research in recent years. The purposes of this article are to define the characteristics of a valid biomarker; review common biological sources of genetic, hormonal, and proteomic biomarkers with attention to practical strengths, weaknesses, and challenges for specimen selection and quality; and discuss potential use of biomarkers in clinical and research settings.

METHODS

Authors draw on the literature and research experiences to address the issues relevant to incorporating biomarkers into nursing research.

RESULTS AND DISCUSSION

An overview of the practical aspects of incorporating biomarkers into nursing research, and the resultant actual and potential clinical applications, are discussed.

Pleiotropic Roles of Non-Coding RNAs in TGF-β-Mediated Epithelial-Mesenchymal Transition and Their Functions in Tumor Progression

Epithelial-mesenchymal transition (EMT) is a spatially- and temporally-regulated process involved in physiological and pathological transformations, such as embryonic development and tumor progression. While the role of TGF-β as an EMT-inducer has been extensively documented, the molecular mechanisms regulating this transition and their implications in tumor metastasis are still subjects of intensive debates and investigations. TGF-β regulates EMT through both transcriptional and post-transcriptional mechanisms, and recent advances underline the critical roles of non-coding RNAs in these processes. Although microRNAs and lncRNAs have been clearly identified as effectors of TGF-β-mediated EMT, the contributions of other atypical non-coding RNA species, such as piRNAs, snRNAs, snoRNAs, circRNAs, and even housekeeping tRNAs, have only been suggested and remain largely elusive. This review discusses the current literature including the most recent reports emphasizing the regulatory functions of non-coding RNA in TGF-β-mediated EMT, provides original experimental evidence, and advocates in general for a broader approach in the quest of new regulatory RNAs.

Precision wildlife medicine: applications of the human-centred precision medicine revolution to species conservation

The current species extinction crisis is being exacerbated by an increased rate of emergence of epizootic disease. Human-induced factors including habitat degradation, loss of biodiversity and wildlife population reductions resulting in reduced genetic variation are accelerating disease emergence. Novel, efficient and effective approaches are required to combat these epizootic events. Here, we present the case for the application of human precision medicine approaches to wildlife medicine in order to enhance species conservation efforts. We consider how the precision medicine revolution, coupled with the advances made in genomics, may provide a powerful and feasible approach to identifying and treating wildlife diseases in a targeted, effective and streamlined manner. A number of case studies of threatened species are presented which demonstrate the applicability of precision medicine to wildlife conservation, including sea turtles, amphibians and Tasmanian devils. These examples show how species conservation could be improved by using precision medicine techniques to determine novel treatments and management strategies for the specific medical conditions hampering efforts to restore population levels. Additionally, a precision medicine approach to wildlife health has in turn the potential to provide deeper insights into human health and the possibility of stemming and alleviating the impacts of zoonotic diseases. The integration of the currently emerging Precision Medicine Initiative with the concepts of EcoHealth (aiming for sustainable health of people, animals and ecosystems through transdisciplinary action research) and One Health (recognizing the intimate connection of humans, animal and ecosystem health and addressing a wide range of risks at the animal-human-ecosystem interface through a coordinated, collaborative, interdisciplinary approach) has great potential to deliver a deeper and broader interdisciplinary-based understanding of both wildlife and human diseases.

Liquid biopsy: a step forward towards precision medicine in urologic malignancies

There is a growing trend towards exploring the use of a minimally invasive "liquid biopsy" to identify biomarkers in a number of cancers, including urologic malignancies. Multiple aspects can be assessed in circulating cell-free DNA, including cell-free DNA levels, integrity, methylation and mutations. Other prospective liquid biopsy markers include circulating tumor cells, circulating RNAs (miRNA, lncRNAs and mRNAs), cell-free proteins, peptides and exosomes have also emerged as non-invasive cancer biomarkers. These circulating molecules can be detected in various biological fluids, including blood, urine, saliva and seminal plasma. Liquid biopsies hold great promise for personalized medicine due to their ability to provide multiple non-invasive global snapshots of the primary and metastatic tumors. Molecular profiling of circulating molecules has been a stepping-stone to the successful introduction of several non-invasive multi-marker tests into the clinic. In this review, we provide an overview of the current state of cell-free DNA-based kidney, prostate and bladder cancer biomarker research and discuss the potential utility other circulating molecules. We will also discuss the challenges and limitations facing non-invasive cancer biomarker discovery and the benefits of this growing area of translational research.

The context of prostate cancer genomics in personalized medicine

Prostate cancer is one of the most common types of cancer in males. Heterogeneous genomic aberrations may lead to prostate cancer onset, progression and metastasis. This heterogeneity also contributes to the variety in cancer risk and outcomes, different drug responses and progression, observed between individual patients. Classical prognostic factors, including prostate-specific antigen, Gleason Score and clinical tumor staging, are not sufficient to portray the complexity of a clinically relevant cancer diagnosis, risk prognosis, treatment choice and therapy monitoring. There is a requirement for novel genetic biomarkers in order to understand the oncogenic heterogeneity in a patient-personalized clinical setting and to improve the efficacy of risk prognosis and treatment choice. A number of biomarkers and gene panels have been established from patient sample cohort studies. These previous studies have provided distinct information to the investigation of heterogeneous malignancy in prostate cancer, which aids in clinical decision-making. Biomarker-guided therapies may facilitate the effective selection of drugs during early treatment; therefore, are beneficial to the individual patient. A non-invasive approach allows for convenient and repeated sampling to screen for cancer and monitor treatment response without the requirement for invasive tissue biopsies. With the current availability of numerous advanced technologies, reliable detection of the minimal tumor residues present following treatment may become clinical practice and, therefore, inform further in the field of personalized medicine.

The feasibility of using mutation detection in ctDNA to assess tumor dynamics

For many decades it has been known that tumor DNA is shed into the blood. As a consequence of technological limitations, researchers were unable to comprehensively characterize circulating DNA. The advent of ultrasensitive and highly specific molecular assays has provided a comprehensive profile of the molecular characteristics and dynamics of circulating DNA in healthy subjects and cancer patients. With these new tools in hand, significant interest has been provoked for an innovative type of tumor biopsy termed a "liquid biopsy". Liquid biopsies are obtained by minimal invasive blood draws from cancer patients. Circulating cancer cells, exosomes and a variety of molecules contained within the liquid biopsy including cell-free circulating tumor DNA (ctDNA) can serve as promising tools to track cancer evolution. Attractive features of ctDNA are that ctDNA isolation is straightforward, ctDNA levels increase or decrease in response to the degree of tumor burden and ctDNA contains DNA mutations found in both primary and metastatic lesions. Consequently, the analysis of circulating DNA for cancer-specific mutations might prove to be a valuable tool for cancer detection. Moreover, the capacity to screen for ctDNA in serial liquid biopsies offers the possibility to monitor tumor progression and responses to therapy and to influence treatment decisions that ultimately may improve patient survival. Here we focus on mutation detection in ctDNA and provide an overview of the characteristics of ctDNA, detection methods for ctDNA and the feasibility of ctDNA to monitor tumor dynamics. Current challenges associate with ctDNA will also be discussed.