p53 and APC mutations are detectable in the plasma and serum of patients with colorectal cancer (CRC) or adenomas

The genetic factors associated with Wnt signaling pathway in colorectal cancer

Colorectal cancer (CRC) is a common cancer with poor prognosis and high mortality. There is growing information about the factors involved in the pathogenesis of CRC. However, the knowledge of the predisposing factors is limited. The development of CRC is strongly associated with the Wingless/Integrated (Wnt) signaling pathway. This pathway comprises several major target proteins, including LRP5/6, GSK3β, adenomatous polyposis coli (APC), axis inhibition protein (Axin), and β-catenin. Genetic variations in these components of the Wnt signaling pathway may lead to the activation of β-catenin, potentially increasing the proliferation of colorectal cells. Because of the potentially important role of the Wnt signaling pathway in CRC, we aimed to review the involvement of different mutations in the main downstream proteins of this pathway, including LRP5/6, APC, GSK3β, Axin, and β-catenin. Determination of the genetic risk factors involved in the progression of CRC may lead to novel approaches for the early diagnosis of CRC and the identification of potential therapeutic targets in the treatment of CRC.

Inactivation of APC Induces CD34 Upregulation to Promote Epithelial-Mesenchymal Transition and Cancer Stem Cell Traits in Pancreatic Cancer

Pancreatic cancer (PC) is a highly lethal malignancy due to the cancer routinely being diagnosed late and having a limited response to chemotherapy. Pancreatic ductal adenocarcinoma (PDAC) is the most common form of pancreatic malignant tumor, representing more than 85% of all pancreatic cancers. In the present study, we characterized the phenotypes of concomitant P53 and APC mutations in pancreatic neoplasms driven by the oncogene KRAS in genetically modified mice (GEMM). In this GEMM setting, APC haploinsufficiency coupled with P53 deletion and KRAS^G12D activation resulted in an earlier appearance of pancreatic intraepithelial neoplasia (PanIN) lesions and progressed rapidly to highly invasive and metastatic PDAC. Through a microarray analysis of murine PDAC cells derived from our APC-deficient PDAC model, we observed that APC loss leads to upregulated CD34 expression in PDAC. CD34 is a member of a family of single-pass transmembrane proteins and is selectively expressed in hematopoietic progenitor cells, vascular endothelial cells, interstitial precursor cells, and various interstitial tumor cells. However, the functional roles of CD34 in pancreatic cancer remain unclear. Thus, in this study, we explored the mechanisms regarding how CD34 promotes the deterioration of pancreatic malignancy. Our results demonstrated that the increased expression of CD34 induced by APC inactivation promotes the invasion and migration of PDAC cells, which may relate to PDAC metastasis in vivo. Collectively, our study provides first-line evidence to delineate the association between CD34 and the APC/Wnt pathway in PDAC, and reveals the potential roles of CD34 in PDAC progression.

Colorectal Adenomas-Genetics and Searching for New Molecular Screening Biomarkers

Colorectal cancer (CRC) is a malignant disease with an incidence of over 1.8 million new cases per year worldwide. CRC outcome is closely related to the respective stage of CRC and is more favorable at less advanced stages. Detection of early colorectal adenomas is the key to survival. In spite of implemented screening programs showing efficiency in the detection of early precancerous lesions and CRC in asymptomatic patients, a significant number of patients are still diagnosed in advanced stages. Research on CRC accomplished during the last decade has improved our understanding of the etiology and development of colorectal adenomas and revealed weaknesses in the general approach to their detection and elimination. Recent studies seek to find a reliable non-invasive biomarker detectable even in the blood. New candidate biomarkers could be selected on the basis of so-called liquid biopsy, such as long non-coding RNA, microRNA, circulating cell-free DNA, circulating tumor cells, and inflammatory factors released from the adenoma into circulation. In this work, we focused on both genetic and epigenetic changes associated with the development of colorectal adenomas into colorectal carcinoma and we also discuss new possible biomarkers that are detectable even in adenomas prior to cancer development.

Cell-free tumour DNA testing for early detection of cancer - a potential future tool

In recent years, detection of cell-free tumour DNA (ctDNA) or liquid biopsy has emerged as an attractive noninvasive methodology to detect cancer-specific genetic aberrations in plasma, and numerous studies have reported on the feasibility of ctDNA in advanced cancer. In particular, ctDNA assays can capture a more 'global' portrait of tumour heterogeneity, monitor therapy response, and lead to early detection of resistance mutations. More recently, ctDNA analysis has also been proposed as a promising future tool for detection of early cancer and/or cancer screening. As the average proportion of mutated DNA in plasma is very low (0.4% even in advanced cancer), exceedingly sensitive techniques need to be developed. In addition, as tumours are genetically heterogeneous, any screening test needs to assay multiple genetic targets in order to increase the chances of detection. Further research on the genetic progression from normal to cancer cells and their release of ctDNA is imperative in order to avoid overtreating benign/indolent lesions, causing more harm than good by early diagnosis. More knowledge on the sources and elimination of cell-free DNA will enable better interpretation in older individuals and those with comorbidities. In addition, as white blood cells are the major source of cell-free DNA in plasma, it is important to distinguish acquired mutations in leukocytes (benign clonal haematopoiesis) from an upcoming haematological malignancy or other cancer. In conclusion, although many studies report encouraging results, further technical development and larger studies are warranted before applying ctDNA analysis for early cancer detection in the clinic.

Role of adenomatous polyposis coli (APC) gene mutations in the pathogenesis of colorectal cancer; current status and perspectives

Colorectal cancer (CRC) is one of the most common forms of solid tumors in the world with high rates of mortality and morbidity. Most cases of CRCs are initiated by inactivating mutations in a tumor suppressor gene, adenomatous polyposis coli (APC), leading to constitutive activation of the Wnt signaling pathway. This review summarizes the roles of somatic and germline mutations of the APC gene in hereditary as well as sporadic forms of CRC. We also discuss the diagnostic and prognostic value of the APC gene in the pathogenesis of CRC for a better understanding of CRC disease.

Advances in Circulating Tumor DNA Analysis

The analysis of cell-free circulating tumor DNA (ctDNA) is a very promising tool and might revolutionize cancer care with respect to early detection, identification of minimal residual disease, assessment of treatment response, and monitoring tumor evolution. ctDNA analysis, often referred to as "liquid biopsy" offers what tissue biopsies cannot-a continuous monitoring of tumor-specific changes during the entire course of the disease. Owing to technological improvements, efforts for the establishment of preanalytical and analytical benchmark, and the inclusion of ctDNA analyses in clinical trial, an actual clinical implementation has come within easy reach. In this chapter, recent advances of the analysis of ctDNA are summarized starting from the discovery of cell-free DNA, to methodological approaches and the clinical applicability.

Do circulating tumor cells, exosomes, and circulating tumor nucleic acids have clinical utility? A report of the association for molecular pathology

Diagnosing and screening for tumors through noninvasive means represent an important paradigm shift in precision medicine. In contrast to tissue biopsy, detection of circulating tumor cells (CTCs) and circulating tumor nucleic acids provides a minimally invasive method for predictive and prognostic marker detection. This allows early and serial assessment of metastatic disease, including follow-up during remission, characterization of treatment effects, and clonal evolution. Isolation and characterization of CTCs and circulating tumor DNA (ctDNA) are likely to improve cancer diagnosis, treatment, and minimal residual disease monitoring. However, more trials are required to validate the clinical utility of precise molecular markers for a variety of tumor types. This review focuses on the clinical utility of CTCs and ctDNA testing in patients with solid tumors, including somatic and epigenetic alterations that can be detected. A comparison of methods used to isolate and detect CTCs and some of the intricacies of the characterization of the ctDNA are also provided.

Digital PCR analysis of circulating nucleic acids

Detection of plasma circulating nucleic acids (CNAs) requires the use of extremely sensitive and precise methods. The commonly used quantitative real-time polymerase chain reaction (PCR) poses certain technical limitations in relation to the precise measurement of CNAs whereas the costs of massively parallel sequencing are still relatively high. Digital PCR (dPCR) now represents an affordable and powerful single molecule counting strategy to detect minute amounts of genetic material with performance surpassing many quantitative methods. Microfluidic (chip) and emulsion (droplet)-based technologies have already been integrated into platforms offering hundreds to millions of nanoliter- or even picoliter-scale reaction partitions. The compelling observations reported in the field of cancer research, prenatal testing, transplantation medicine and virology support translation of this technology into routine use. Extremely sensitive plasma detection of rare mutations originating from tumor or placental cells among a large background of homologous sequences facilitates unraveling of the early stages of cancer or the detection of fetal mutations. Digital measurement of quantitative changes in plasma CNAs associated with cancer or graft rejection provides valuable information on the monitoring of disease burden or the recipient's immune response and subsequent therapy treatment. Furthermore, careful quantitative assessment of the viral load offers great value for effective monitoring of antiviral therapy for immunosuppressed or transplant patients. The present review describes the inherent features of dPCR that make it exceptionally robust in precise and sensitive quantification of CNAs. Moreover, I provide an insight into the types of potential clinical applications that have been developed by researchers to date.

Generation of blood circulating DNA: the sources, peculiarities of circulation and structure

Extracellular nucleic acids (exNA) were described in blood of both healthy and illness people as early as in 1948, but staied overlooked until middle 60-th. Starting from the beginning of new millennium and mainly in the last 5 years exNA are intensively studied. Main attention is directed to investigation of exNA as the source of diagnostic material whereas the mechanisms of their generation, as well as mechanisms to providing long-term circulation of exNA in the bloodstream are not established unambiguously. According to some authors, the main source of circulating nucleic acids in blood are the processes of apoptosis and necrosis, while others refer to the possible nucleic acid secretion by healthy and tumor cells. Circulating DNA were found to be stable in the blood for a long time, escaping from the action of DNA hydrolyzing enzymes and are apparently packed in different supramolecular complexes. This review presents the opinions of various authors and evidence in favor of all the theories describingappearance of extracellular DNA, the features of the circulation and structure of the extracellular DNA and factors affecting the time of DNA circulation in blood

Protein-protein interaction analysis of distinct molecular pathways in two subtypes of colorectal carcinoma

The aim of this study was to identify the molecular events that distinguish serrated colorectal carcinoma (SCRC) from conventional colorectal carcinoma (CCRC) through differential gene expression, pathway and protein-protein interaction (PPI) network analysis. The GSE4045 and GSE8671 microarray datasets were downloaded from the Gene Expression Omnibus database. We identified the genes that are differentially expressed between SCRC and normal colon tissues, CCRC and healthy tissues, and between SCRC and CCRC using Student’s t-tests and Benjamini-Hochberg (BH) multiple testing corrections. The differentially expressed genes (DEGs) were then mapped to Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways and their enrichment for specific pathways was investigated using the Database for Annotation, Visualization and Integrated Discovery (DAVID) tool with a significance threshold of 0.1. Analysis of the potential interactions between the protein products of 220 DEGs (between CCRC and SCRC) was performed by constructing a PPI network using data from the high performance RDF database (P<0.1). The interaction between pathways was also analyzed in CCRC based on the PPI network. Our study identified thousands of genes differentially expressed in SCRC and CCRC compared to healthy tissues. The DEGs in SCRC and CCRC were enriched in cell cycle, DNA replication, and base excision repair pathways. The proteasome pathway was significantly enriched in SCRC but not in CCRC after BH adjustment. The PPI network showed that tumour necrosis factor receptor-associated factor 6 (TRAF6) and atrophin 1 (ATN1) were the most central genes in the network, with respective degrees of node predicted at 90 and 88. In conclusion, the preoteasome pathway was shown to be specifically enriched in SCRC. Furthermore, TRAF6 and ATN1 may be promising biomarkers for the distinction between serrated and conventional CRC.

NIH-3T3 fibroblasts cultured with plasma from colorectal cancer patients generate poorly differentiated carcinomas in mice

The ability of cells to undergo cellular transitions, in particular, to switch between epithelial and mesenchymal states, might be highly advantageous during the progression of carcinoma. Using histological and immunohistochemical techniques, we here show that the injection into mice of spontaneously transformed NIH-3T3 cells generated fusocellular sarcomas, whereas NIH-3T3 cells that had been transformed by culturing with plasma from colorectal cancer patients gave rise to tumors that phenotypically resembled the carcinomas of the original cancer patients. Thus, plasma from cancer patients is able to transform NIH-3T3 fibroblasts into malignant epithelial-like cells, suggesting that such cells might undergo mesenchymal to epithelial transition during plasma-induced transformation.

Protein kinase CK2α is overexpressed in colorectal cancer and modulates cell proliferation and invasion via regulating EMT-related genes

Background

Protein kinase CK2 is a highly conserved, ubiquitous protein serine/threonine kinase that phosphorylates many substrates and has a global role in numerous biological and pathological processes. Overexpression of the protein kinase CK2α subunit (CK2α) has been associated with the malignant transformation of several tissues, with not nearly as much focus on the role of CK2α in colorectal cancer (CRC). The aims of this study are to investigate the function and regulatory mechanism of CK2α in CRC development.

Methods

Expression levels of CK2α were analyzed in 144 patients (104 with CRC and 40 with colorectal adenoma) by immunohistochemistry. Proliferation, senescence, motility and invasion assays as well as immunofluorescence staining and western blots were performed to assess the effect of CK2α in CRC.

Results

The immunohistochemical expression of nuclear CK2α was stronger in tumor tissues than in adenomas and normal colorectal tissues. Suppression of CK2α by small-interfering RNA or the CK2α activity inhibitor emodin inhibited proliferation of CRC cells, caused G0/G1 phase arrest, induced cell senescence, elevated the expression of p53/p21 and decreased the expression of C-myc. We also found that knockdown of CK2α suppressed cell motility and invasion. Significantly, CK2α inhibition resulted in β-catenin transactivation, decreased the expression levels of vimentin and the transcription factors snail1 and smad2/3, and increased the expression of E-cadherin, suggesting that CK2α regulates the epithelial-mesenchymal transition (EMT) process in cancer cells.

Conclusions

Our results indicate that CK2α plays an essential role in the development of CRC, and inhibition of CK2α may serve as a promising therapeutic strategy for human CRC.

Circulating free tumor DNA and colorectal cancer

Cancer is characterized by multiple somatic genetic and epigenetic alterations that could be useful as molecular markers for detecting tumor DNA in different bodily fluids. In patients with various diseases as well as in healthy subjects, circulating plasma and serum carry small amounts of non-cell-bound DNA. In this free circulating DNA, tumor-associated molecular alterations can be detected in patients who have cancer. In many instances, the alterations identified are the same as those found in the primary tumor tissue, thereby suggesting tumor origin from a fraction of the circulating free DNA. In fact, various types of DNA alterations described in colorectal cancer have been detected in the circulating free DNA of patients with colorectal cancer. These alterations include KRAS2, APC and TP53 mutations, DNA hypermethylation, microsatellite instability (MSI) and loss of heterozygosity (LOH). Also, advances in polymerase chain reaction (PCR)-based technology now allow the detection and quantification of extremely small amounts of tumor-derived circulating free DNA in colorectal cancer patients. The present report summarizes the literature available so far on the mechanisms of circulating free DNA, and on the studies aimed at assessing the clinical and biological significance of tumor-derived circulating free DNA in colorectal cancer patients. Thus, tumor-derived circulating free DNA could serve as a marker for the diagnosis, prognosis and early detection of recurrence, thereby significantly improving the monitoring of colorectal cancer patients.

Circulating nucleic acids in plasma/serum

Since the discovery of circulating nucleic acids in plasma in 1948, many diagnostic applications have emerged. For example, diagnostic and prognostic potentials of circulating tumour-derived DNA have been demonstrated for many types of cancer. The parallel development of fetal-derived DNA detection in maternal plasma has opened up the possibility of non-invasive prenatal diagnosis and monitoring of many pregnancy-associated disorders. In this regard, non-invasive fetal rhesus blood group genotyping has already been translated to clinical practice. Other applications of circulating DNA in traumatology and transplant monitoring have also been reported. The more recent discoveries of circulating tumour-derived RNA and fetal-derived RNA have proven to be equally important as their DNA counterparts. Successful prenatal diagnosis of Down's syndrome by fetal RNA analysis has recently been reported. However, the definite origin and release mechanisms of circulating nucleic acids have remained incompletely understood, with cell death being suggested to be associated with such nucleic acid release. Pre-analytical standardisation will become increasingly relevant when comparing data from different laboratories. In conclusion, studies of circulating nucleic acids have promised exciting developments in molecular diagnostics in the years to come.

Circulating nucleic acids (CNAs) and cancer--a survey

It has been known for decades that it is possible to detect small amounts of extracellular nucleic acids in plasma and serum of healthy and diseased human beings. The unequivocal proof that part of these circulating nucleic acids (CNAs) is of tumor origin, initiated a surge of studies which confirmed and extended the original observations. In the past few years many experiments showed that tumor-associated alterations can be detected at the DNA and RNA level. At the DNA level the detection of point mutations, microsatellite alterations, chromosomal alterations, i.e. inversion and deletion, and hypermethylation of promoter sequences were demonstrated. At the RNA level the overexpression of tumor-associated genes was shown. These observations laid the foundation for the development of assays for an early detection of cancer as well as for other clinical means.

DNA Integrity Assay: A Plasma-Based Screening Tool for the Detection of Prostate Cancer

PURPOSE

The aim of this study was to evaluate the utility of the DNA integrity assay (DIA) as a plasma-based screening tool for the detection of prostate cancer.

EXPERIMENTAL DESIGN

Blood samples were collected from patients with biopsy-proven prostate cancer prior to prostatectomy (n = 123) and processed as two-spin plasma preparations. The three control groups included: males <40 years old with no history of cancer (group 1, n = 20); cancer-free postprostatectomy patients (group 2, n = 25), and patients with a negative prostate biopsy (group 3, n = 22). DNA in plasma preparations were isolated, hybrid-captured, and DNA fragments (200 bp, 1.3, 1.8, and 2.4 kb) were multiplexed in real-time PCR. A baseline cutoff was determined for individual fragment lengths to establish a DIA score for each patient sample.

RESULTS

Patients with prostate cancer (86 of 123; 69.9%) were determined to have a positive DIA score of >or=7. The DIA results from control groups 1, 2, and 3 showed specificities of 90%, 92%, and 68.2%, respectively. Of the patients with negative age-adjusted prostate-specific antigen (PSA) and prostate cancer, 19 of 30 (63%) had a positive DIA score. The area under the receiver operating characteristic curve for DIA was 0.788.

CONCLUSION

While detecting 69.9% of those with prostate cancer, DIA maintained an overall specificity of 68.2% to 92%, a range favorably comparable to that currently accepted for PSA (60-70%). The variability in specificity between control groups is likely explained by the established 19% to 30% detection of prostate cancer on subsequent biopsies associated with control group 3. DIA detected 63% of the prostate cancers undetected by currently accepted PSA ranges.

Comparisons between capillary zone electrophoresis and real-time PCR for quantification of circulating DNA levels in human sera

BACKGROUND

Recently, some research results showed that the circulating DNA in serum or plasma had potential for the molecular diagnosis and prognosis of certain cancers. Several methods have been employed for the quantification of circulating DNA. However, the circulating DNA levels obtained by various methods exhibited considerable differences. Additionally, these methods were labor-extensive and time-consuming, and not suitable for the quantification of circulating DNA in numerous samples due to the use of commercial DNA extraction kits for the purification of circulating DNA. We presented a new method for the quantification of circulating DNA in sera by capillary zone electrophoresis (CZE) with laser-induced fluorescence detection (LIF).

METHODS

In the present work, we want to make comparison between CZE-LIF assay and real time PCR for the quantification of circulating DNA levels. Linearity, intra and inter variability of two methods were evaluated.

RESULTS

The intra and inter variability of circulating DNA quantification by real-time PCR were 7.3% and 14.92%, respectively. In CZE assay the intra and inter variability were 4.19% and 6.91%, respectively. The R.S.D. values of the same coated capillary and different coated capillaries were 5.14% and 9.02%, respectively. Our data showed that the circulating DNA levels obtained by two methods had a good correlation. Moreover, we further confirmed that blood samples collection, serum preparation and other treatment procedures had a significant impact on the DNA levels in sera.

CONCLUSION

Our data further illustrated that CZE-LIF is a simple, rapid and sensitive method for the quantification of circulating DNA in human sera, and well suitable for the analysis of a large number of samples in clinical diagnosis.

Restriction enzyme cleavage of fluorescently labeled DNA fragments--analysis of the method and its usage in examination of digestion completeness

Restriction enzymes have proven to be among the most valuable tools in molecular biology. In this work, we demonstrate that the cleavage of fluorescently labeled, PCR-amplified DNA can be used as a simple and highly sensitive technique for detection of sequences present in a percentage as low as 0.6% in a DNA pool. Due to the fact that fluorescent labeling of DNA fragments enables such sensitive detection and quantification of restriction enzyme cleavage, the method was further exploited in monitoring of the enzymatic digestion completeness and in determination of factors that influence restriction enzyme effectiveness. We analyzed the activity of six restriction endonucleases; the percentage of uncleaved DNA fragments predominantly ranged between 2.0 and 2.5 and the highest value was 8.00%. We conclude that, since the enzymatic digestion completeness may not always be assured, each assay based on restriction enzyme cleavage that is intended to be used in investigations of heterogeneity in a DNA pool should be constructed so that the presence of cleaved sequences is the indication of pool nonuniformity. When the presence of uncleaved sequences indicates pool heterogeneity, the results could be misleading due to possible incompleteness of enzymatic cleavage.

From Colonic Polyps to Colon Cancer: Pathophysiology, Clinical Presentation, and Diagnosis

Epidemiologists, basic researchers, clinicians, and public health administrators unite! Develop and implement a simple, safe, and effective preventive and screening test for colon cancer. The public will willingly and enthusiastically accept such a test. Many thousands of lives are at stake every year.

The pathophysiology, clinical presentation, and diagnosis of colon cancer and adenomatous polyps

A review of the pathophysiology, clinical presentation, and diagnosis of colon cancer and colonic polyps is important and timely. This field is rapidly changing because of breakthroughs in the molecular basis of carcinogenesis and in the technology for colon cancer detection and treatment. This article reviews colon cancer and colonic polyps, with a focus on recent dramatic advances, to help the pri-mary care physician and internist appropriately refer patients for screening colonoscopy and intelligently evaluate colonoscopic findings to reduce the mortality from this cancer.

Molecular detection of APC, K- ras, and p53 mutations in the serum of colorectal cancer patients as circulating biomarkers

Early detection of tumor DNA in serum/plasma prior to the development of recurrence or metastases could help improve the outcome of patients with colorectal cancer (CRC) after tumor resection. Recent advances in the detection of tumor DNA in the serum/plasma has opened up numerous new areas for investigation and new possibilities for molecular diagnosis. APC and K- ras mutations are considered to be early-stage developments of CRCs, whereas p53 mutations are thought to be relatively late events in the tumorigenesis of CRCs. The aim of this study was to search for the presence of genetic mutations in the DNA extracted from the serum of CRC patients and healthy subjects. We simultaneously evaluate the significance of APC, K- ras, and p53 gene mutations in cancer tissues and their paired serum samples of 104 CRC patients by polymerase chain reaction-single strand conformation polymorphism analysis (PCR-SSCP) followed by direct sequencing. Additionally, analysis was carried out to detect the serum carcinoembryonic antigen (CEA) levels in CRC patients. Overall, we found at least one of the gene mutations in tumor tissues from 75% (78/104) of the CRC patients. Comparison of the three molecular markers showed that the detection rates in the serum were 30.4%, 34.0%, and 34.2% for APC, K- ras, and p53 genes, respectively. Of these patients, 46.2% (36/78) were identified as having positive serum results, whereas all healthy controls remained negative. The overall positive tumor DNA detection rates in the serum were 0% (0/7) for Dukes' A classification, 22.4% (11/49) for Dukes' B, 48.7% (19/39) for Dukes' C, and 66.7% (6/9) for Dukes' D. The detection rate increased as the tumor stage progressed ( p = 0.012). Concurrently, a significant difference was observed between lymph node metastases and positive serum tumor DNA detection ( p < 0.001). A significantly higher postoperative metastasis/recurrence rate in patients harboring gene mutations with serum tumor DNA than those without serum tumor DNA was also demonstrated ( p < 0.001). However, no significant correlation between the postoperative metastasis/recurrence and serum CEA levels was observed ( p = 0.247). These data suggest that the identification of circulating tumor DNA using the molecular detection of APC, K- ras, and p53 gene mutations is a potential tool for early detection of postoperative recurrence/metastases. Moreover, these genes may be potential molecular markers of poor clinical outcome in CRC patients.

TP53Gene in Blood Plasma DNA of Tumor Patients

Tumor-specific TP53 mutations are detectable in the blood plasma of tumor patients. Mutations of the TP53 tumor suppressor gene are risk factors for tumor progression. The objective of this work is to compare the presence of TP53 mutations in plasma-DNA before and after tumor treatment with the status of this gene in the tumor tissue sample. DNA was extracted from plasma samples of 25 patients with gastrointestinal tumors, and from paraffin-embedded tumor tissues from the same patients. Temperature gradient gel electrophoresis (TGGE) was performed for mutation screening of exons 5-8 of GC-clamped polymerase chain reaction products. Mutation-positive and wildtype gel bands from TGGE were cut and reamplified for fluorescence-labeled sequence analysis. The results of several mutation analyses were correlated with analysis of p53 autoantibodies in the same plasma. Mutation frequency (one or several mutations per sample) was 7.1% in blood plasma of tumor-free patients, 87.0% in tumor tissues, 78.6% in plasma before tumor treatment, and 36.8% after treatment. Fifteen of 22 mutations in tumor tissues of 13 patients also were detected in the same exons of plasma before treatment (68.2%). Mutations in plasma after treatment (2-684 days) were the same in 6 of 30 cases of tissue mutations only. Six of seven patients with mutations after treatment in their plasma had metastases. One patient was p53 autoantibody negative, but has a terminator mutation of codon 196 in tissue and in posttreatment plasma as well. Genetic analysis of plasma in tumor patients should be further developed, as it might be of prognostic value.

Colon cancer during pregnancy

The medical community should become mobilized to diagnose colon cancer earlier in pregnancy to improve prognosis. The primary care physician or obstetrician should refer the pregnant patient with significant gastrointestinal complaints to the gastroenterologist for evaluation. Likewise, the gastroenterologist should be prepared to perform sigmoidoscopy, preferably without endoscopic medications, for significant lower gastrointestinal symptoms such as persistent rectal bleeding. Sigmoidoscopy is particularly sensitive in identifying colon cancer in pregnant patients because their cancers are usually distal and within reach of the sigmoidoscope.

Circulating DNA in plasma and serum: biology, preanalytical issues and diagnostic applications

The recent studies in circulating nucleic acids have brought about a new dimension to medical diagnostics. In oncology, various tumor-associated molecular alterations have been detected in the plasma/serum of cancer patients. These findings have important implications for the diagnosis, prognostication and monitoring of many types of malignancies. In pregnancy, the discovery of fetal DNA in maternal circulation has opened up a new source of fetal genetic material for noninvasive analysis for numerous fetal conditions and detection of certain pregnancy-associated disorders. The measurement of circulating DNA has also found potential application in the post-treatment monitoring of transplant patients and the assessment and prognostication of trauma patients. Although much attention has focused on circulating DNA, the knowledge of its biology is still at an early stage. For example, the origin and mechanisms of release of circulating DNA remain to be elucidated. The eventual clinical application of circulating DNA technology would also require the thorough elucidation of preanalytical factors that may affect its measurement in clinical laboratories.

Circulating DNA: a new diagnostic gold mine?

The recent discovery that cell-free DNA can be shed into the bloodstream as a result of tumour cell death has generated great interest. Numerous studies have demonstrated tumour-specific alterations in DNA recovered from plasma or serum of patients with various malignancies, a finding that has potential for molecular diagnosis and prognosis. The implication is that tumour-derived nucleic acids of human or viral origin can be retrieved from blood by a minimally invasive procedure, and used as a surrogate tumour marker to monitor the course of the disease or aid in early diagnosis. The present review will describe the main areas of ongoing investigation, with particular emphasis on technical issues and available data of clinical relevance.

Detecting rare mutations associated with cancer risk

For more than a decade, investigators have been searching for a means of determining the risk of individuals developing cancer by detecting rare oncogenic mutations. The accumulation of mutations and the clonal evolvement of tumors provide opportunities for monitoring disease development and intervening prior to the presentation of clinical symptoms, or determining the risk of disease relapse during remission. A number of techniques, mostly polymerase chain reaction (PCR)-based, have been developed that enable the detection of rare oncogenic mutations within the range of 10(-2) to 10(-4) wild-type cells. Only a handful of procedures enable the detection of intragenic single base mutations at one mutant in 10-6 or better. These ultra-sensitive mutation detection techniques have produced some interesting results regarding single base mutation spectra and frequencies in p53, Harvey-ras, N-ras, and other reporter genes and DNA sequences in human tissues. Although there is evidence that some individuals may harbor cells or clones expressing genomic instability, the connection with the processes of carcinogenesis is still tenuous. There remains a need for rigorous epidemiological studies employing these ultra-sensitive mutation detection procedures. Since genomic instability is considered key to tumor development, the relevance of the detection of hypermutable clones in individuals is discussed in the context of cancer risk.