Circulating Tumor Cells And Circulating Tumor Dna PdfBy Kenxirocen In and pdf 22.03.2021 at 10:22 9 min read
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- Impact of circulating tumor DNA in hepatocellular and pancreatic carcinomas
- Circulating tumor DNA
- Impact of Circulating Tumor DNA (ctDNA) in Patients with Gastrointestinal Malignancies
- What is circulating tumor DNA and how is it used to diagnose and manage cancer?
Nanotheranostics ; 5 3 :
The precise mechanism of ctDNA release is unclear. The biological processes postulated to be involved in ctDNA release include apoptosis and necrosis from dying cells, or active release from viable tumor cells. Fragmentation of this length might be indicative of apoptotic DNA fragmentation , suggesting that apoptosis may be the primary method of ctDNA release. The fragmentation of cfDNA is altered in the plasma of cancer patients.
Impact of circulating tumor DNA in hepatocellular and pancreatic carcinomas
Despite many advances in the diagnosis and treatment of colorectal cancer CRC , its incidence and mortality rates continue to make an impact worldwide and in some countries rates are mounting. Over the past decade, liquid biopsies have been the object of fundamental and clinical research with regard to the different steps of CRC patient care such as screening, diagnosis, prognosis, follow-up, and therapeutic response.
They are attractive because they are considered to encompass both the cellular and molecular heterogeneity of tumours. They are easily accessible and can be applied to large-scale settings despite the cost. This review highlights the different advantages and disadvantages of each type of blood-based biopsy and underlines which specific one may be the most useful and informative for each step of CRC patient care.
Colorectal cancer CRC is a frequently diagnosed cancer in developed countries, ranking third in terms of both incidence and mortality [ 1 ]. In many countries, a bowel cancer screening program is available especially in patients with specific risks of colorectal cancer such as patients over 50 years old or hereditary colorectal cancers [ 2 ]. Common screening methods used are: 1 stool testing for blood such as guaiac fecal occult blood test or fecal immunochemical test FIT [ 3 ]; 2 endoscopy [ 4 ] such as rectoscopy or colonoscopy; and 3 computed tomographic CT colonography, which is less invasive.
For many years, a reliable diagnosis has been based on biopsies from colorectal tissues. However, biopsy results alone cannot display sensitive and specific information which can provide a more complete analysis of the tumour thus allowing us to target treatment in the different phases of CRC. This is linked to the heterogeneity of tumours not only in the spatial dimension but also in the temporal one [ 5 ].
Moreover, the procedure of tissue biopsy can sometimes be invasive with risk of complications such as pain, bleeding, infections, or perforations. During screening or diagnosing colonoscopies, the overall adverse event rate has been reported to be around 2. Even with computed tomographic CT colonography, a recent study including Japanese centres with , CT examinations showed 0. In addition, tissue biopsies are also time-consuming. A lack of speed in histologic response is an ever-increasing phenomenon due in particular to the number of demands and new therapies used, for example, chemotherapy or immunotherapy.
If we look globally at prognosis, follow-up, risk of recurrence, therapeutic response, and combined clinical modalities, we see that imaging and biopsy results often lack of sensitivity and specificity while exposing the patient to specific risks. As a result, research has been focused on developing more reliable and more accessible biomarkers. Blood, urine, cerebrospinal fluid, stool, and saliva were explored [ 8 ].
Despite, the technical difficulties and cost generated to develop those tools, progress has been made in this area. CTCs were first described by T. Ashworth, an Australian physician, in the blood of a deceased patient [ 9 ]. They originate from both primary tumours and metastases shedding. Different biological phenotypes of CTCs exist: epithelial, mesenchymal, stem cell-like or mixed [ 10 ].
They are present in blood in very small quantities, vastly outnumbered by other cells, especially white blood cells. As a result, their detection needs a phase of isolation-enrichment and a second phase of detection.
Firstly, the phase of isolation-enrichment can be performed by either physical or biological methods or by a combination of these 2 methods. Another form of physical enrichment is possible using density gradient centrifugation Ficoll and Percoll Figure 1. It is worth noting that typical antibodies used for enrichment are against epithelial cellular markers like EpCAM [ 18 ].
Secondly, the detection phase can be performed either at the cellular or nucleic scale Figure 2. It is key to note that detection of CTCs is most often achieved using epithelial markers such as cytokeratine [ 18 ]. The main drawback using CTCs, is that their analyses require extremely sensitive and specific methods.
In most of the devices for both isolation—enrichment and detection of CTCs, epithelial markers are used because a strong relationship between epithelial positive circulating cells and prognosis of cancer has been demonstrated in many studies independent of the type of cancer [ 25 ].
Indeed, CTCs correlate to the process of metastasis. However, different types of CTCs cohabit within the circulation. Thus, tumour cells need to invade the blood circulation using Epithelial-mesenchymal transition, EMT where they have a stem cell trait [ 26 ] and then invade distant organs mesenchymal-epithelial transition, MET. This heterogeneity of the population of CTCs may consequently be misleading.
However, we underline that detection of these cells can convey information thanks to their complete integrity, good quality, and easy to process leading proteins and nucleic acids DNA, RNA. Thus, cytologic techniques, molecular biologic techniques and cellular cultures of live CTCs with pharmacodynamic tests can be performed. Due to many protocols with lack of standardisation in regard to sample collections and methodologies for analyses, it is very difficult to translate this research into practical and clinical use.
Briefly, it is recommended to use plasma because cfDNA serum concentration that is approximately three- to twenty-four-fold higher compared to that of plasma due to white blood cell clotting [ 37 ]. Moreover, for isolation of cfDNA it is necessary to work with specific anticoagulants such as ethylenediaminetetraacetic acid EDTA that has been demonstrated as the best one for analysis as it protects cfDNA from DNAses activity [ 38 ]. Many authors have attempted to describe homogeneous protocols such as Nikolaev et al.
A recent literature review highlights the best pre analytical conditions to study cfDNA [ 40 ]. NGS is a method comparing DNA sequences of normal cells and tumoural cells allowing for the discovery of new oncogenic drivers [ 41 ]. Thus, the combination of these two methods can reveal the profile of tumours and their evolution.
It is an easy method using a simple blood sample collection and its analysis can assess both the tumour dynamics and the genomics modifications [ 42 ]. Different mechanisms are known to convey communication between cells such as autocrine, paracrine or endocrine pathways, depending on the distance between the cells. Another category of cell—cell communication has been discovered through vesicles; these are defined as an extension of the cell membrane.
These factors promote pathological processes, such as proliferation, metastasis [ 44 ], angiogenesis and epithelial-mesenchymal-transition [ 45 , 46 ].
In CRC, exosomes have been the most studied. There is no consensus about the best method to isolate them. Ultracentrifugation, and ultrafiltration [ 47 ] are commonly used to extract them. Much evidence in literature has shown that the role of non-coding RNA is fundamental concerning regulation of oncogenes and tumour suppressor genes in cancer.
The small miRNAs are 18—25 nucleotides in length. Their hairpin-loop structures protect them from RNAse degradation; furthermore, their stability is enhanced not only by an embedded system with vesicles [ 47 ] or platelets [ 48 ] but also by binding with Argonaute Each system of stability would be an indirect marker of cell type origin [ 49 ].
However the lack of standardization and robustness of the measuring methodology has led to contradictory results [ 51 ]. Firstly, it is difficult to extract and isolate miRNAs due to their small size and their different binding associations. Despite different ultracentrifugation methods with detergents or proteases to purify them, different variations exist highlighting the need for further studies. RT-qPCR has the highest sensitivity and specificity.
But studies have to be performed in order to improve isolation and use of miRNAs as validated biomarkers. Up to now, clinical studies have especially emphasized ctDNA as a potential biomarker for early diagnosis and screening.
Methylation of gene promoters is generally the first step in oncogenesis and according to the type of genes implicated, the origin of the tumour can be determined. Negative FIT can be preceded by the gold standard of a screening colonoscopy [ 56 ]. It is worth noting that recently, the team of Cohen et al. The difficulty to isolate and define CTCs highlights the weakness in using them in daily clinical practice for screening and early diagnosis.
Searches in the Pubmed and Cochrane databases were conducted. This article from Chen et al. Recent clinical studies have confirmed the presence of these unique CRC miRNAs in comparison with healthy people [ 60 , 61 ].
One recent publication by Wang et al. It is important to underline that for some studies, samples were from plasma while in others they were from serum; indeed, extracted DNA quality varies according to sample type. A literature search including articles between January and April was performed and 34 studies analysing serum or plasma miRNAs for diagnosis of CRC were included. The main issue of this meta-analysis is that a sub-group analysis according to the type of sample either serum or plasma was not carried out.
Another meta-analysis [ 66 ] looked at studies from to with CRC patients and control healthy patients. After meta-regression analyses, this study demonstrated that serum samples were the most accurate. The accuracy was also more important in the Asian population in comparison with Caucasian people. It appears that miRNAs are interesting prospective biomarkers but more studies are needed to confirm this in the preclinical stage, in particular within a cohort of patients who have a positive fecal immunochemical test FIT [ 69 ].
All in all, taking into account all the drawbacks of each biomarker, the best cancer screening method, particularly in colorectal cancer, appears at present to be CancerSEEK. It is a test developed in January by researchers in Baltimore [ 57 ] which combines the detection of ctDNA with different proteins in order to improve the signal to noise ratio.
In colon cancers stages II and III, after radical and curative treatment, surveillance is conducted using both scanners and biological assessments CEA biomarker [ 70 ]. However, imaging is not sensitive enough and exposes patients to radiation while CEA does not combine high sensitivity and specificity.
The best test to detect recurrences is an increase of CEA during the first year of follow-up in patients treated for CRC [ 71 ]. In rectal cancers, liquid biopsies could be of interest in order to predict the response of radiochemotherapy and disease recurrence; however, evidence in this domain is lacking.
As a consequence, it is the steady decrease with time of ctDNA rates that seems to best represent the absence of residual disease. A modification with increase of ctDNA is a synonym of recurrence [ 74 ].
This study started in July with a total of patients enrolled in the follow-up of 3 years. The first results will be available at the end of The first, focused on CTCs [ 77 ], gathered 15 studies with patients having undergone either surgery alone or chemotherapy alone or both therapies [ 21 , 79 — 92 ]. The presence of CTCs was linked to a poorer overall survival and progression-free disease; however there was an important heterogeneity among all the studies therefore sub-group analyses were also done.
They reported that positive CTC patients had significant poor overall survival OS and progression-free disease PFD according to different criteria time of blood collection, detection method, median follow-up and cutoff value of CTC number.
The second meta-analysis [ 78 ], included 9 studies of patients treated for CRC [ 93 — ] with both qualitative and quantitative evaluation of cfDNA. Here also, there was notable heterogeneity: population size of studies, tumour stages, time of collection 8 before treatment, 1 after treatment marker types, collection origins plasma, [ 93 — 95 ] or serum, [ 96 — ] , detection methods PCR followed by sequencing [ 93 , 96 ], spectrophotometry [ 97 ], quantitative PCR q-PCR [ 94 , 95 ], mutant-enriched PCR ME-PCR [ 98 ], and real-time PCR rt-PCR [ 95 , 99 — ].
After stratification on confounding factors such as type of tumour marker searched in cfDNA, tumour stage, collection origin [serum or plasma] and methods of detection [PCR, qPCR, others] and population size, it was demonstrated that cfDNA could predict both overall survival and recurrence-free survival.
Recurrences were considered as distant metastasis and confirmed by imaging. The role of prognostic assessment by both qualitative and quantitative analysis of ctDNA was useful in CRC at a metastatic stage [ ]. In different cases, neoadjuvant radio chemotherapy for middle and low rectal cancers stages II-III , or adjuvant chemotherapy metastatic diseases or recurrences are used.
Different combinations of drugs exist and different kinds of therapies are available: chemotherapies, targeted therapies, or immunotherapies. Heterogeneity defines cancers and explains why for both specific tumours and stages, each person will respond differently to therapies.
Circulating tumor DNA
Despite many advances in the diagnosis and treatment of colorectal cancer CRC , its incidence and mortality rates continue to make an impact worldwide and in some countries rates are mounting. Over the past decade, liquid biopsies have been the object of fundamental and clinical research with regard to the different steps of CRC patient care such as screening, diagnosis, prognosis, follow-up, and therapeutic response. They are attractive because they are considered to encompass both the cellular and molecular heterogeneity of tumours. They are easily accessible and can be applied to large-scale settings despite the cost. This review highlights the different advantages and disadvantages of each type of blood-based biopsy and underlines which specific one may be the most useful and informative for each step of CRC patient care. Colorectal cancer CRC is a frequently diagnosed cancer in developed countries, ranking third in terms of both incidence and mortality [ 1 ]. In many countries, a bowel cancer screening program is available especially in patients with specific risks of colorectal cancer such as patients over 50 years old or hereditary colorectal cancers [ 2 ].
Hepatocellular carcinoma HCC and pancreatic cancer PC belong to the most lethal malignancies worldwide. Despite advances in surgical techniques and perioperative multidisciplinary management, the prognosis of both carcinoma entities remains poor mainly because of rapid tumor progression and early dissemination with diagnosis in advanced tumor stages with poor sensitivity to current therapy regimens. Both highly heterogeneous visceral carcinomas exhibit unique somatic alterations, but share common driver genes and mutations as well. Recently, circulating tumor DNA ctDNA could be identified as a liquid biopsy tool with huge potential as non-invasive biomarker in early diagnosis and prognosis. CtDNA released from necrotic or apoptotic cells of primary tumors, metastasis, and circulating tumor cells can reveal genetic and epigenetic alterations with tumor-specific and individual mutation and methylation profiles. Hepatocellular carcinoma HCC and pancreatic cancer PC represent two of the most challenging visceral malignancies in oncology with rising incidence and lack of reliable biomarkers for early diagnosis, prognosis, and therapy response. PC and HCC are estimated to become the second and third respective leading causes of cancer-related death in western countries by Rahib et al.
The major potential advantage of CTC and ctDNA analysis is that they are minimally /Silicon_Biosystems_DEPArray_Brochure_pdf?t=
Impact of Circulating Tumor DNA (ctDNA) in Patients with Gastrointestinal Malignancies
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A biopsy sample of tissue often is tested for specific genetic variations also referred to as mutations that may have a targeted inhibitor that represents a clear optimal treatment for that cancer. However, it may not be possible to get enough tissue from the tumor to do these studies. DNA from our cells, including cancer cells, breaks down as part of its normal life cycle. Testing of ctDNA offers several advantages over attempts at repeated tissue biopsies.
Circulating tumor DNA ctDNA testing is rapidly emerging as a new tool for scientists and oncologists treating gastrointestinal cancers. The varied numbers of testing platforms, either research or the ones that are commercially available, are helping us understand several fundamental aspects of tumor The varied numbers of testing platforms, either research or the ones that are commercially available, are helping us understand several fundamental aspects of tumor biology. For example, tumor heterogeneity and tumor evolution is a concept that we as oncologists have always known about and seen in patients being treated for any of the gastrointestinal cancers.
What is circulating tumor DNA and how is it used to diagnose and manage cancer?
As a tumor grows, cells die and are replaced by new ones. The dead cells get broken down and their contents , including DNA, are released into the bloodstream. The quantity of ctDNA varies among individuals and depends on the type of tumor, its location, and for cancerous tumors, the cancer stage. Detecting and diagnosing a tumor. Finding DNA with genetic differences aids in tumor detection. Diagnosing the type of tumor using ctDNA can reduce the need for getting a sample of the tumor tissue tumor biopsy , which can be challenging when a tumor is difficult to access, such as a tumor in the brain or lung.
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ME TOO, что означало: Я. Беккер расхохотался. Он дожил до тридцати пяти лет, а сердце у него прыгало, как у влюбленного мальчишки. Никогда еще его не влекло ни к одной женщине. Изящные европейские черты лица и карие глаза делали Сьюзан похожей на модель, рекламирующую косметику Эсте Лаудер. Худоба и неловкость подростка бесследно исчезли.
Keywords: circulating tumor cells; ctDNA; cancer. 1. Introduction. Circulating tumor cells, or CTCs, are cells that are shed from tumors into the.
Миллиард долларов. Мидж хмыкнула. - Кажется, чуточку дороговато, не правда. - Да уж, - застонал. - Чуточку.
Похоже, нужно было проанализировать политический фон, на котором разворачивались эти события, сравнить их и перевести это сопоставление в магическое число… и все это за пять минут. ГЛАВА 124 - Атаке подвергся последний щит. На ВР отчетливо было видно, как уничтожалось окно программной авторизации.