Detection of cytokeratins 19/20 and guanylyl cyclase C in peripheral blood of colorectal cancer patients

Keratin intermediate filaments in the colon: guardians of epithelial homeostasis

Keratin intermediate filament proteins are major cytoskeletal components of the mammalian simple layered columnar epithelium in the gastrointestinal tract. Human colon crypt epithelial cells express keratins 18, 19 and 20 as the major type I keratins, and keratin 8 as the type II keratin. Keratin expression patterns vary between species, and mouse colonocytes express keratin 7 as a second type II keratin. Colonic keratin patterns change during cell differentiation, such that K20 increases in the more differentiated crypt cells closer to the central lumen. Keratins provide a structural and mechanical scaffold to support cellular stability, integrity and stress protection in this rapidly regenerating tissue. They participate in central colonocyte processes including barrier function, ion transport, differentiation, proliferation and inflammatory signaling. The cell-specific keratin compositions in different epithelial tissues has allowed for the utilization of keratin-based diagnostic methods. Since the keratin expression pattern in tumors often resembles that in the primary tissue, it can be used to recognize metastases of colonic origin. This review focuses on recent findings on the biological functions of mammalian colon epithelial keratins obtained from pivotal in vivo models. We also discuss the diagnostic value of keratins in chronic colonic disease and known keratin alterations in colon pathologies. This review describes the biochemical properties of keratins and their molecular actions in colonic epithelial cells and highlights diagnostic data in colorectal cancer and inflammatory bowel disease patients, which may facilitate the recognition of disease subtypes and the establishment of personal therapies in the future.

Highly degraded RNA can still provide molecular information: An in vitro approach

The long-term survival of RNA in postmortem tissues is a tricky topic. Many aged/forensic specimens show, in fact, high rates of null/inconclusive PCR-based results, while reliable outcomes were sometimes achieved from archaeological samples. On the other hand, several data show that the RNA is a molecule that survives even to several physical-chemical stresses. In the present study, a simple protocol, which was already developed for the prolonged hydrolysis of DNA, was applied to a RNA sample extracted from blood. This protocol is based on the heat-mediated (70°C) hydrolysis for up to 36 h using ultrapure water and di-ethyl-pyro-carbonate-water as hydrolysis medium. Measurable levels of depurination were not found even if microfluidic devices showed a progressive pattern of degradation. The reverse transcription/quantitative PCR analysis of two (60 bp long) housekeeping targets (glyceraldehyde-3-phosphate dehydrogenase and porphobilinogen deaminase) showed that the percentage of amplifiable target (%AT) decreased in relation to the duration of the damaging treatment (r² > 0.973). The comparison of the %AT in the degraded RNA and in the DNA samples that underwent the same damaging treatment showed that the %AT is always higher in RNA, reaching up to three orders of magnitude. Lastly, even the end-point PCR of blood-specific markers gave reliable results, which is in agreement with the body fluid origin of the sample. In conclusion, all the PCR-based results show that RNA maintains the ability to be retro-transcribed in short cDNA fragments even after 36 h of incubation at 70°C in mildly acidic buffers. It is therefore likely that the long-term survival of RNA samples depends mainly on the protection against RNAase attacks rather than on environmental factors (such as humidity and acidity) that are instead of great importance for the stability of DNA. As a final remark, our results suggest that the RNA analysis can be successfully performed even when DNA profiling failed.

Colorectal carcinoma screening: Established methods and emerging technology

Colorectal carcinoma screening programs have shown success in lowering both the incidence and mortality rate of colorectal carcinoma at a population level, in part because this carcinoma is relatively slow growing and has an identifiable premalignant lesion. Still, many patients do not undergo the recommended screening for colorectal carcinoma, and of those who do, a subset may be over- or under-diagnosed by the currently available testing methods. The primary purpose of this article is to review the data regarding currently available colorectal cancer screening modalities, which include fecal occult blood testing, direct colonic visualization, and noninvasive imaging techniques. In addition, readers will be introduced to a variety of biomarkers that may serve as stand-alone or adjunct tests in the future. Finally, there is a brief discussion of the current epidemiologic considerations that public health officials must address as they create population screening guidelines. The data we provide as laboratory physicians and scientists are critical to the construction of appropriate recommendations that ultimately decrease the burden of disease from colorectal carcinoma.

Expression of guanylyl cyclase C in tissue samples and the circulation of rectal cancer patients

Guanylyl cyclase C (GCC) is a transmembrane surface receptor restricted to intestinal epithelial cells, from the duodenum to the rectum. We compared GCC expression in tumors and normal rectal tissues, and investigated the relation between GCC expression and metastasis and long-term survival of rectal cancer patients. Based on the UICC classification, 42 rectal cancer patients in this study were classified as stage I, 48 patients as stage II, and 90 patients as stage III. Overexpression of GCC was observed in 80 rectal tumors as compared to matched normal tissues, where no strong staining of GCC was observed. An association between GCC mRNA in the circulation and tumor emboli in vessels, CK20 mRNA, distant organ metastasis, and survival status was observed in 100 rectal cancer patients. Univariate Cox regression analysis indicated that tumor emboli in vessels, lymph node metastasis, mesenteric root lymph node metastasis and GCC mRNA correlated with 5-year disease-free survival (DFS); while lymph node metastasis, GCC mRNA, and CK20 mRNA strongly correlated with 5-year overall survival (OS). In a multivariate Cox regression model, GCC mRNA level and mesenteric root lymph node metastasis associated with DFS, while GCC mRNA levels associated with OS. Quantification of GCC expression in circulation is a valuable biomarker for assessing tumor burden and predicting outcome in rectal cancer patients.

Serum Levels of Cyfra 21 in Patients with Benign and Malignant Salivary Gland Tumors

INTRODUCTION

Cyfra 21 is a serum-soluble fragment of cytokeratin19. Increased Cyfra 21 serum levels and their benefit as a tumor marker have been shown in some malignancies. This study aimed to evaluate the serum levels of Cyfra 21 in patients with benign and malignant salivary gland tumors.

MATERIALS AND METHODS

In this cross-sectional study, the serum level of Cyfra 21 in 44 patients with malignant salivary gland tumors and 16 cases of pleomorphic adenoma were compared with 28 healthy controls using enzyme-linked immunosorbent assay (ELISA). Data were analyzed statistically using the Kruskal Wallis test, analysis of variance (ANOVA) and Spearman's correlation tests.

RESULTS

Mean serum levels of Cyfra 21 were 0.135 ± 0.285 ng/ ml in the control group, 0.167 ± 0.142 ng/ ml in patients with pleomorphic adenoma and 1.059 ± 3.251 ng/ml in patients with malignant salivary gland tumors. There was no significant difference among groups. Cyfra 21 levels did not correlate with location of tumor, clinical stage or cigarette smoking.

CONCLUSION

Results of the present study showed no significant difference in Cyfra 21 serum level in salivary gland tumors compared with normal individuals. In addition, Cyfra 21 serum level was not sufficiently sensitive to function as a tumor marker in salivary gland tumors.

Expression of the PLS3 Gene in Circulating Cells in Patients with Colorectal Cancer

Circulating tumor cells (CTC) are cells in circulating blood that have the antigen and gene features of tumor cells of a specific type. Since they can be potentially used in diagnostics and monitoring of treatment of many tumors, they have been attracting attention of researchers worldwide. Plastin-3 (PL S3) is one of such markers of CTC. The aim of the study was to assess expression of PL S3 in CTC in patients with colorectal cancer, to conduct a statistical analysis and to demonstrate a link between expression of PL S3 and progress of the disease, level of CEA and Ca19-9 markers, gender and age of the patients.

MATERIAL AND METHODS

A group of 85 patients of the Department of General and Colorectal Surgery of the Medical University in Łódź were enrolled in this study. Circulating tumor cells were isolated from whole blood of patients with colorectal cancer and an analysis of PL S3 gene expression in CTC was conducted. The next step was to conduct a statistical analysis and to demonstrate a link between expression of PL S3 in patients' CTC and progress of the disease, level of CEA and Ca 19-9 markers, gender and age of the patients.

RESULTS

PL S3 is a marker which can be potentially used in prediction and monitoring of colorectal cancer. A link between expression of PL S3 in CTC of patients with colorectal cancer and metastasis to lymph nodes has been demonstrated. It may be of key importance how PL S3 could impact the qualification to supplementary cancer treatment in patients with stage II colorectal cancer. A link between expression of PL S3 gene in CTC and gender requires further in-depth studies. It is beyond doubt that PL S3 must be further investigated to determine its role in diagnostics, prediction, treatment and monitoring of treatment of colorectal cancer.

Cytokeratin 20 positive cells in blood of colorectal cancer patients as an unfavorable prognostic marker

OBJECTIVES

Cytokeratin 20 (CK20) is one of the most investigated markers for the detection of circulating colorectal cancer (CRC) cells by reverse transcription polymerase chain reaction (RT-PCR). The aim of this study was to evaluate prognostic value of RT-PCR detection of circulating CRC cells using CK20 as a marker, and to compare the value of preoperative and postoperative blood sample analysis for that purpose.

METHODS

Ribonucleic acid (RNA) was isolated from mononuclear cell fraction of blood samples taken from 95 CRC patients before and after tumor resection and from 23 healthy volunteers and assayed by real-time RT-PCR for CK20 expression.

RESULTS

In patients positive for CK20 postoperatively both progression-free survival (PFS) and overall survival were significantly shorter than in patients negative for CK20 postoperatively, while the difference between patients positive and negative for CK20 preoperatively was not statistically significant in terms of neither PFS nor overall survival.

CONCLUSION

Our results have shown prognostic value of circulating cancer cells detected in postoperative blood samples from CRC patients using CK20 as marker for RT-PCR, which has potential implications for treatment of these patients. In clinical practice, CK20 expression profile could be a factor in weighting treatment options in CRC patients. In cases where multiple treatment options are possible, patients with positive postoperative CK20 expression could be candidates to receive more aggressive treatment.

Construction and Quantitative Validation of Chicken CXCR4 Expression Reporter

Site directional migration is an important biological event and an essential behavior for latent migratory cells. A migratory cell maintains its motility, survival, and proliferation abilities by a network of signaling pathways where CXCR4/SDF signaling route plays crucial role for directed homing of a polarized cell. The chicken embryo due to its specific vasculature modality has been used as a valuable model for organogenesis, migration, cancer, and metastasis. In this research, the regulatory regions of chicken CXCR4 gene have been characterized in a chicken hematopoietic lymphoblast cell line (MSB1). A region extending from -2000 bp upstream of CXCR4 gene to +68 after its transcriptional start site, in addition to two other mutant fragments were constructed and cloned in a promoter-less reporter vector. Promoter activity was analyzed by quantitative real-time RT-PCR and flow cytometry techniques. Our findings show that the full sequence from -2000 to +68 bp of CXCR4 regulatory region is required for maximum promoter functionality, while the mutant CXCR4 promoter fragments show a partial promoter activity. The chicken CXCR4 promoter validated in this study could be used for characterization of directed migratory cells in chicken development and disease models.

A Pilot Study of CK19, CK20 and GCC mRNA in the Peripheral Blood as a Colorectal Cancer Biomarker Panel

Colorectal cancer remains one of the major cancer- related deaths despite progress in the treatment during past decades. Detection of disease at earlier stages reduces its mortality. The aim of current study was to investigate expression of Cytokeratin 19 (CK19), Cytokeratin 20 (CK20) and Guanylyl Cyclase C (GCC) mRNA in peripheral blood of non- metastatic colorectal cancer patients which may result into introducing of an early detection test. 25 patients with colorectal cancer and 25 healthy controls were recruited. Blood was obtained from all individuals. Expression of CK19 and CK20 and GCC mRNA and 18SrRNA (as reference gene) were determined based on real- time RT-PCR on total RNA from blood. CK19, CK20 and GCC expression had been detected in 68%, 76% & 52% of patient group, respectively, which was higher than healthy group, with 8%, 32% and 0% expression, respectively (p<0.05). CK20 was over-expressed 8- fold more in patients compared to controls. Similar result was found for CK19 with 4- fold over- expression. Sensitivity and specificity of combination of markers were 88% and 68%, respectively. Current data suggest that the detection of CK20 & CK19 as relative sensitive markers may become a valuable tool for primary diagnosis of colorectal cancer in early stages. GCC could be considered as a specific tumor marker for detection of colorectal cancer. Higher expression of these markers in patients may be considered as a relative good tool for the diagnosis of disease in non- metastatic stages.

Colorectal Cancer Biomarkers: Where Are We Now?

Colorectal cancer is one of the major causes of cancer-related death in the Western world. Patient survival is highly dependent on the tumor stage at the time of diagnosis. Reduced sensitivity to chemotherapy is still a major obstacle in effective treatment of advanced disease. Due to the fact that colorectal cancer is mostly asymptomatic until it progresses to advanced stages, the implementation of screening programs aimed at early detection is essential to reduce incidence and mortality rates. Current screening and diagnostic methods range from semi-invasive procedures such as colonoscopy to noninvasive stool-based tests. The combination of the absence of symptoms, the semi-invasive nature of currently used methods, and the suboptimal accuracy of fecal blood tests results in colorectal cancer diagnosis at advanced stages in a significant number of individuals. Alterations in gene expression leading to colorectal carcinogenesis are reflected in dysregulated levels of nucleic acids and proteins, which can be used for the development of novel, minimally invasive molecular biomarkers. The purpose of this review is to discuss the commercially available colorectal cancer molecular diagnostic methods as well as to highlight some of the new candidate predictive and prognostic molecular markers for tumor, stool, and blood samples.

Short communication: quantitative comparison of iodothyronine deiodinase I and II mRNA expression in ovine tissues

Iodothyronine deiodinases I and II (DIO1 and DIO2) remove iodine from T4 to convert it to a more biologically active T3. The relative contribution of different tissue deiodinases to the establishment of a euthyroid state in sheep is not known. The objective of this study was to quantitate the amounts of transcription of DIO1 and DIO2 deiodinases in different ovine tissues. Using RT-qPCR, we found that DIO1 deiodinase is transcribed in skeletal muscle, kidney, and heart, more than thyroid, in diaphragm in quantities very similar to thyroid, and in liver, spleen, lung, and mammary gland lower than thyroid. We also found that the level of DIO2 transcription in all other tissues was lower than that in thyroid. In clinical settings, measurement of DIO1 and DIO2 expression in a given tissue may provide important clues on the intensity of selenium deficiency and its effects on the metabolism of thyroid hormones.

Expression dynamics of pluripotency genes in chicken primordial germ cells before and after colonization of the genital ridges

Mammalian species utilize an inductive mechanism of germ cell specification, diverting the fate of some of somatic cells toward pluripotency and germ-cell totipotency. It is not known if avian species utilize a similar mechanism nor if, analogous to mammalian primordial germ cells (PGCs), pluripotency genes are continuously upregulated in migrating and genital ridge-colonizing avian PGCs. Thus, this study was conducted to quantify and to analyze the expression profile of pluripotency genes at different stages of chicken PGCs development at Hamburger and Hamilton (HH) stage 14, when the majority of PGCs have entered into the bloodstream; at HH stage 18, when PGCs have resided for 8-12 hr in the bloodstream; and at HH stage 28, when the majority of PGCs are found in the genital ridge. The transcription for Oct4, Sox2, and Nanog continuously decreased from HH stage 14 to HH stage 28. In addition, equal amounts of total RNA could be isolated from chicken PGCs at each stage of development, indicating that the observed drop of transcription of pluripotency genes is not a consequence of transcriptional repression in general. Decreased expression for all three proteins was also observed at HH stage 28. Furthermore, in comparison to blood PGCs, those residing in the gonad have lost their full capacity for colony formation. Our results indicate that, in contrast to mammalian PGCs, chicken PGCs continuously downregulate the expression of pluripotency genes and show a progressive loss of pluripotency-associated features during different stages of germ-line migration.

Sodium selenite increases the transcript levels of iodothyronine deiodinases I and II in ovine and bovine fetal thyrocytes in vitro

Selenium is essential for thyroid hormone homeostasis. Selenium is co-translationally incorporated into the protein backbone of 5' deiodinase enzymes, which are responsible for the intra- and extra-thyroidal activation of thyroid hormones. The objective of this study was to evaluate the effects of sodium selenite on the transcript levels of type I (DIO1) and II (DIO2) deiodinases in the primary culture of ovine and bovine fetal thyroid. By culture of fetal thyrocytes in the presence or absence of sodium selenite, and quantification of DIO1 and DIO2 transcripts using real-time reverse transcription polymerase chain reaction (RT-qPCR), we found that sodium selenite is able to increase the abundance of transcripts for DIO1 and DIO2 genes. We also found that cultured thyrocytes in the presence of sodium selenite compared to control cultured thyrocytes release more T3 into the culture medium. This indicates that in the presence of sodium selenite higher levels of DIO1 and DIO2 enzymes are produced, which are able to convert T4 to T3. In conclusion, we have shown that sodium selenite is increasing the abundance of DIO1 and DIO2 transcripts and increasing the production and release of T3 from cultured fetal thyrocytes. This finding emphasizes the role of selenium in transcriptional and expression processes during development and suggests that selenium deficiency during pregnancy in sheep and cattle may lead to the lower levels of DIO1 and DIO2 transcription in fetal thyroid, and thus, lower level of thyroidal T3 release into the fetal serum.

Detection of cytokeratin-20-positive cells in preoperative and postoperative blood samples from colorectal cancer patients by real-time RT-PCR

BACKGROUND

Detection of circulating cancer cells by reverse transcription polymerase chain reaction (RT-PCR) has been studied as a prognostic marker in patients with colorectal cancer (CRC) but so far with conflicting results regarding specificity and prognostic value. In this study cytokeratin-20 (CK20) was evaluated by real-time RT-PCR as a marker for circulating CRC cell detection and the influence of surgical tumor resection on the presence of circulating CRC cells was analyzed.

METHODS

RNA was isolated from the mononuclear cell fraction of blood samples taken from 95 CRC patients before and after tumor resection and from 23 healthy volunteers and assayed by real-time RT-PCR for CK20 expression.

RESULTS

Among 23 healthy volunteers one was positive for CK20. Among 95 CRC patients, 25 were positive for CK20 before and 23 after surgery. Sixteen patients positive before surgery became negative after surgery, while 14 patients negative before surgery became positive after surgery. An increase in the proportion of CK20-positive samples with increasing stage of disease was observed for preoperative but not postoperative blood samples.

CONCLUSIONS

Its association with clinical stage indicates that CK20 might have prognostic value as a marker for detection of circulating CRC cells. Surgical tumor resection can both reduce and induce the presence of circulating CRC cells.

Sensitivity estimates of blood-based tests for colorectal cancer detection: impact of overrepresentation of advanced stage disease

A large number of blood-based markers have been proposed for early detection of colorectal cancer (CRC). Their sensitivity for detecting CRC has mostly been evaluated in clinical settings, and found to be higher in more advanced stages compared with earlier stages of the disease. The aim of this study is to estimate the overall sensitivity of blood-based markers expected in screening settings, where the proportion of advanced stages is typically lower than in clinical settings. A systematic literature review was performed on studies evaluating sensitivity and specificity of blood-based markers for early detection of CRC. For each study, overall sensitivity expected in screening settings was estimated by weighting stage-specific sensitivities according to the stage distribution of CRC expected in the screening setting. The latter was derived from 12,605 CRC cases diagnosed in the German screening colonoscopy program during 2003-2007. Overall, 73 studies evaluating 55 blood-based markers were identified. Adjusted sensitivity was lower than reported sensitivity in 120 (90%) evaluations of different markers. Median absolute reduction in sensitivity after adjustment was 9.0% (interquartile range: 4.0-13.0) units, whereas median relative reduction was 19.5% (interquartile range: 11.3-33.3%). Blood-based markers for CRC detection reported from clinical settings showed higher sensitivities than expected in the screening setting in most cases, mainly due to substantially higher proportions of advanced stage cancers. Adjustment of sensitivity to the stage distribution expected in the screening setting is crucial to obtain realistic and comparable estimates of sensitivities.

Perioperative cancer cell dissemination detected with a real-time RT-PCR assay for EpCAM is not associated with worse prognosis in pancreatic ductal adenocarcinoma

Background

Epithelial cell adhesion molecule (EpCAM) has been used as surrogate marker for the quantification of circulating tumour cells (CTC). Our aim was to prospectively study the value of a real-time RT-PCR assay for EpCAM detection in the peripheral blood and peritoneal cavity of patients undergoing pancreatectomy for pancreatic ductal adenocarcinoma (PDAC).

Methods

From 48 patients with PDAC (40 resectable, 8 unresectable) and 10 patients with chronic pancreatitis undergoing pancreatectomy 10 ml of venous blood was drawn preoperatively (PB) and postoperatively (POB, day 1 (D1B), day 7 (D7B) and after 6 weeks (6WB). Of all patients undergoing pancreatectomy, 40 ml peritoneal lavage fluid was taken preoperatively and postoperatively. A real-time RT-PCR assay (TaqMan, ABI Prism 7700) was developed for the detection of EpCAM mRNA. To discriminate between EpCAM-positive and negative samples a cut-off was applied. Median postoperative follow-up was 24.0 months (range: 0.7 - 41.3).

Results

PB was EpCAM-positive (+) in 25% of patients versus 65% of patients in POB (p < 0.0001). EpCAM(+) was noted at D1B, D7B and 6WB was found in 28.6%, 23.1% and 23.5% of patients respectively. Preoperative peritoneal lavage fluid was EpCAM(+) in 10.3% versus 53.8% of patients postoperatively (p < 0.0001).

At none of the time-points, an association was found between EpCAM positivity in blood and/or peritoneal cavity and cancer-specific or disease-free survival. Also, no significant associations were found between clinicopathological variables and perioperative EpCAM positivity.

Conclusions

Despite a significant increase in EpCAM counts in postoperative blood and peritoneal lavage fluid this was not associated with worse prognosis after pancreatectomy for PDAC.

Trial registration

Clinicaltrials.gov NCT00495924

A combination of serum markers for the early detection of colorectal cancer

PURPOSE

Fecal occult blood testing is recommended as first-line screening to detect colorectal cancer (CRC). We evaluated markers and marker combinations in serum as an alternative to improve the detection of CRC.

EXPERIMENTAL DESIGN

Using penalized logistic regression, 6 markers were selected for evaluation in 1,027 samples (301 CRC patients, 143 patients with adenoma, 266 controls, 141 disease controls, and 176 patients with other cancer). The diagnostic performance of each marker and of marker combinations was assessed.

RESULTS

To detect CRC from serum samples, we tested 22 biomarkers. Six markers were selected for a marker combination, including the known tumor markers CEA (carcinoembryonic antigen) and CYFRA 21-1 as well as novel markers or markers that are less routinely used for the detection of CRC: ferritin, osteopontin (OPN), anti-p53, and seprase. CEA showed the best sensitivity at 95% specificity with 43.9%, followed by seprase (42.4%), CYFRA 21-1 (35.5%), OPN (30.2%), ferritin (23.9%), and anti-p53 (20.0%). A combination of these markers gave 69.6% sensitivity at 95% specificity and 58.7% at 98% specificity. Focusing on International Union against Cancer (UICC) stages 0-III reduced the sensitivity slightly to 68.0% and 53.3%, respectively. In a subcollective, with matched stool samples (75 CRC cases and 234 controls), the sensitivity of the marker combination was comparable with fecal immunochemical testing (FIT) with 82.4% and 68.9% versus 81.8% and 72.7% at 95% and 98% specificity, respectively.

CONCLUSIONS

The performance of the serum marker combination is comparable with FIT. This provides a novel tool for CRC screening to trigger a follow-up colonoscopy for a final diagnosis.

Molecular detection of colorectal neoplasia

A variety of noninvasive molecular approaches to colorectal cancer screening are emerging with potential to improve screening effectiveness and user-friendliness. These approaches are based on the sensitive assay of molecular markers in stool, blood, and urine samples. New methods, especially next generation stool-based tests, have been shown to detect both colorectal cancers and precancerous lesions with high accuracy. Validation of these technologies in average-risk populations are needed to establish their role for general colorectal cancer screening. This review addresses the biological rationale, technical advances, recent clinical performance data, and remaining issues with molecular screening for colorectal cancer.

Real-time electrochemical monitoring of the polymerase chain reaction by mediated redox catalysis

We described the proof-of-principle of a nonoptical real-time PCR that uses cyclic voltammetry for indirectly monitoring the amplified DNA product generated in the PCR reaction solution after each PCR cycle. To enable indirect measurement of the amplicon produced throughout PCR, we monitor electrochemically the progressive consumption (i.e., the decrease of concentration) of free electroactive deoxynucleoside triphosphates (dNTPs) used for DNA synthesis. This is accomplished by exploiting the fast catalytic oxidation of native deoxyguanosine triphosphate (dGTP) or its unnatural analogue 7-deaza-dGTP by the one-electron redox catalysts Ru(bpy)(3)(3+) (with bpy = 2,2'-bipyridine) or Os(bpy)(3)(3+) generated at an electrode. To demonstrate the feasibility of the method, a disposable array of eight miniaturized self-contained electrochemical cells (working volume of 50 microL) has been developed and implemented in a classical programmable thermal cycler and then tested with the PCR amplification of two illustrated examples of real-world biological target DNA sequences (i.e., a relatively long 2300-bp sequence from the bacterial genome of multidrug-resistant Achromobacter xylosoxidans and a shorter 283-bp target from the human cytomegalovirus). Although the method works with both mediator/base couples, the catalytic peak current responses recorded with the Ru(bpy)(3)(3+)/dGTP couple under real-time PCR conditions are significantly affected by a continuous current drift and interference with the background solvent discharge, thus leading to poorly reproducible data. Much more reproducible and reliable results are finally obtained with the Os(bpy)(3)(3+)/7-deaza-dGTP, a result that is attributed to the much lower anodic potential at which the catalytic oxidation of 7-deaza-dGTP by Os(bpy)(3)(3+) is detected. Under these conditions, an exponential decrease of the catalytic signal as a function of the number of PCR cycles is obtained, allowing definition of a cycle threshold value (C(t)) that correlates inversely with the initial amount of target DNA. A semilogarithmic plot of C(t) with the initial copy number of target DNA gives a standard linear curve similar to that obtained with fluorescent-based real-time PCR. Although the detection limit (10(3) molecules of target DNA in 50 microL) and sensitivity of the electrochemical method is not as high as conventional optical-based real-time PCR, the methodology described here offers many of the advantages of real-time PCR, such as a high dynamic range (over 8-log(10)) and speed, high amplification efficiency (close to 2), and the elimination of post-PCR processing. The method also has the advantage of being very simple, just requiring the use of low-cost single-use electrodes and the addition of a minute amount of redox catalyst into the PCR mixture. Moreover, compared to the other recently developed electrochemical real-time PCR based on solid-phase amplification, the present approach does not require electrode functionalization by a DNA probe. Finally, on account of the relative insensitivity of electrochemical methods to downscaling, the detection scheme is quite promising for use in miniaturized devices and in the development of point-of-care diagnosis applications.

Data-driven normalization strategies for high-throughput quantitative RT-PCR

BACKGROUND

High-throughput real-time quantitative reverse transcriptase polymerase chain reaction (qPCR) is a widely used technique in experiments where expression patterns of genes are to be profiled. Current stage technology allows the acquisition of profiles for a moderate number of genes (50 to a few thousand), and this number continues to grow. The use of appropriate normalization algorithms for qPCR-based data is therefore a highly important aspect of the data preprocessing pipeline.

RESULTS

We present and evaluate two data-driven normalization methods that directly correct for technical variation and represent robust alternatives to standard housekeeping gene-based approaches. We evaluated the performance of these methods against a single gene housekeeping gene method and our results suggest that quantile normalization performs best. These methods are implemented in freely-available software as an R package qpcrNorm distributed through the Bioconductor project.

CONCLUSION

The utility of the approaches that we describe can be demonstrated most clearly in situations where standard housekeeping genes are regulated by some experimental condition. For large qPCR-based data sets, our approaches represent robust, data-driven strategies for normalization.

Previstage GCC test for staging patients with colorectal cancer

The presence of tumor cells in regional lymph nodes is the most important prognostic and predictive marker in staging patients with colorectal cancer. Cancer cells in lymph nodes are associated with a poorer prognosis and an increased risk of recurrent disease. Additionally, nodal metastases identify patients who derive maximum benefit from adjuvant therapy. However, traditional paradigms for staging patients with colorectal cancer underestimate the extent of metastases and patients whose lymph nodes are ostensibly free of tumor cells by histopathology (pN0) have a 25-30% risk of developing recurrent disease, reflected by the presence of occult nodal metastases. These observations underscore the unmet clinical need for molecular approaches to accurately detect metastatic disease and identify patients at risk for disease relapse that could benefit from adjuvant chemotherapy. Detection of disease-specific mRNA targets as prognostic and predictive markers employing quantitative reverse transcription (qRT)-PCR is an emerging technology that has become a benchmark for individualization of patient management. However, to date, applications of qRT-PCR to detecting occult nodal metastases in colorectal cancer have been equivocal, reflecting markers with suboptimal sensitivity and specificity; limitations of utilizing qualitative, rather than quantitative, RT-PCR; and underpowered study designs based on inadequate patient populations. In that context, guanylyl cyclase C (GCC) is the most sensitive and specific biomarker for metastatic colorectal cancer in extra-intestinal tissues. GCC qRT-PCR detects occult metastases in lymph nodes, providing the most powerful independent prognostic information for predicting disease recurrence in pN0 patients in prospective multicenter clinical trials. This technology forms the basis for the Previstagetrade mark GCC Colorectal Cancer Staging Test encompassing a proprietary multiplex qRT-PCR assay compatible with formalin-fixed, paraffin-embedded lymph nodes for detecting occult metastases. Previstage GCC is a new diagnostic tool that may improve the accuracy of staging, prognosis of clinical outcomes and prediction of therapeutic responses to adjuvant therapy, representing a key advance in the management of patients with colorectal cancer.

Oxytocin and vasopressin gene expression and RNA splicing patterns in the rat supraoptic nucleus

In this study, we test the hypothesis that there are differential splicing patterns between the expressed oxytocin (OT) and vasopressin (VP) genes in the rat supraoptic nucleus (SON). We quantify the low abundance, intron-containing heteronuclear RNAs (hnRNAs) and the higher abundance mRNAs in the SON using two-step, quantitative SYBR Green real-time reverse transcription (RT)-PCR and external standard curves constructed using synthetic 90 nt sense-strand oligonucleotides. The levels of OT and VP mRNA in the SON were found to be similar, approximately 10(8) copies/SON pair, whereas the copy numbers of VP hnRNAs containing intron 1 or 2 and the OT hnRNA containing intron 1 are much lower, i.e., approximately 10(2)-10(3) copies/rat SON pair. However, the estimated copy number of the intron 2-containing OT hnRNA is much larger, approximately 10(6) copies/SON pair. The relative distributions of all the OT and VP RNA species were invariant and independent of the physiological status of the rats (e.g., osmotically stimulated or lactating rats). Using intron-specific riboprobes against hnRNAs, we demonstrate by fluorescence in situ hybridization strong signals of OT hnRNA containing intron 2 predominantly in the cytoplasm, in contrast to the localization of the VP hnRNA found only in the nuclei. Taken together, these data support the view that the splicing patterns between OT and VP gene transcripts are different and show that there is a selective cytoplasmic retention of OT intron 2.

DETECTION OF DISSEMINATED TUMOR CELLS IN PERIPHERAL BLOOD

Metastases are the major cause of cancer-related deaths in patients with solid epithelial malignancies, such as breast, colorectal and prostate carcinomas. Hematogenous spreading of tumor cells from a primary tumor can be considered as a crucial step in the metastasis cascade leading eventually to the formation of clinically manifest metastases. Consequently, as shown in recent studies, the detection of disseminated tumor cells in peripheral blood might be of clinical relevance with respect to individual patient prognosis and staging or monitoring of therapy. However, the rarity of disseminated tumor cells in peripheral blood renders the application of sensitive techniques mandatory for their detection. The emergence of highly sophisticated reverse transciptase-polymerase chain reaction (RT-PCR) assays, combining a preanalytical enrichment step with the assessment of multiple molecular tumor markers expressed in disseminated tumor cells, provides a powerful tool in detecting disseminated tumor cells with high sensitivity and specificity. This review will discuss currently used tumor markers as well as experimental means to enhance the sensitivity and specificity of RT-PCR assays to detect disseminated tumor cells in the peripheral blood of patients with breast, colorectal, and prostate cancers, and their clinical relevance assessed in recent studies.

Epithelial molecular markers in the peripheral blood of patients with colorectal cancer

Despite the modest improvements in patient survival from colorectal cancer in the last few decades, the overall five-year survival rate remains at 40 to 45 percent. Surgical resection is the mainstay of treatment for colorectal cancer; however, nearly one-half of all patients who undergo a potentially curative resection will relapse because of undetected micrometastasis. The fact that the overall survival rate remains poor strongly suggests that the dissemination of these cells occurs early in the disease process and emphasizes the need for finding feasible diagnostic methods with sufficient sensitivity and specificity. The most commonly used technique for the detection of nucleic acid material of disseminated tumor cells is the polymerase chain reaction. We critically review the literature on DNA and messenger ribonucleic acid molecular markers that have been used for the detection of circulating tumor cells in the peripheral blood of patients with colorectal cancer and other solid tumors as appropriate for comparison. The cytokeratins, particularly cytokeratin 19 and cytokeratin 20, are the most investigated prognostic markers, but even for these questions remain about their clinical value, and hence most recent studies are utilizing a combination of factors. There is an urgent need for standardized isolation and analysis techniques to be adopted thus allowing large-scale, appropriately controlled, multicenter trials to be undertaken on the most promising candidate markers.

Detection of disseminated tumor cells in the lymph nodes of colorectal cancer patients using a real-time polymerase chain reaction assay

INTRODUCTION

Postoperative treatment for colorectal cancer depends on tumor stage as defined by the International Union Against Cancer (UICC). Adjuvant chemotherapy is not recommended in patients without lymph node involvement (UICC stages I and II). As many as 20-30% of these patients, however, will develop recurrence.

AIMS AND OBJECTIVES

We conducted this study to determine the presence of disseminated tumor cells in the lymph nodes by quantitative real-time polymerase chain reaction (QRT-PCR) for cytokeratin 20 (CK20) in an attempt to provide supplementary information compared to histopathological findings.

MATERIALS AND METHODS

Using a standard QRT-PCR assay, we examined primary tumors and 391 lymph nodes from 31 patients with completely resected colorectal cancer.

RESULTS

Of the 31 primary tumors, 29 were positive for CK20 by QRT-PCR.

DISCUSSION

An examination of the lymph nodes from the 29 patients with CK20-positive primary tumors revealed that 35 (92.1% sensitivity) of the 38 histopathologically positive lymph nodes and 54 (16.7%) of the 324 histopathologically negative lymph nodes were positive by molecular analysis. CK20 expression was detected in 10 (100%) of 10 patients with a histopathologically positive lymph node status (pN1). In 9 (47.4%) of 19 patients with negative histopathological results (pN0), we detected a CK20 mRNA signal in at least one lymph node. Whereas eight patients with histopathologically negative lymph nodes could be upstaged on the basis of the molecular findings, no patient would be downstaged.

CONCLUSION

Our results suggest that QRT-PCR for CK20 is a useful tool for the quantitative detection of micrometastases in the regional lymph nodes. We introduce a standardized procedure that integrates a molecular diagnostic technique in the clinical staging.

Expression of C-Myc mRNA in squamous cell carcinoma of the tongue

BACKGROUND

The aim of this study was to evaluate clinical significance of C-myc mRNA in patients with tongue cancer.

METHODS

C-myc mRNA expression was studied by RT-PCR in peripheral blood of 25 tongue cancer patients and 24 controls. C-myc protein expression was studied by immunohistochemistry.

RESULTS

In tongue cancer patients, pretherapeutic C-myc mRNA expression was significantly higher as compared to controls. In tumor tissues, a trend of low expression of C-myc mRNA was noted as compared to pretherapeutic blood. The mean pretherapeutic C-myc mRNA level was lower in tobacco-users, in older patients, in keratinizing tumors, in tumors showed lymphocytic infiltration as well as in non-responders as compared to their respective counterparts. C-myc mRNA expression was lower in tumors showed lymphatic permeation and in patients with a habit of tobacco use. Further, low C-myc mRNA expression associated with poor prognosis. C-myc protein expression was noted in 72% of the tumors and an inverse correlation was noted between C-myc protein expression and disease stage. In early stage disease, an inverse correlation was noted while in advanced stage disease, a positive correlation was noted.

CONCLUSION

In tongue cancer, downregulation of C-myc mRNA associated with advancement of the disease and worse prognosis.

Guanylyl cyclase C: a molecular marker for staging and postoperative surveillance of patients with colorectal cancer

Staging patients with colorectal cancer defines their prognosis and therapeutic management. Unfortunately, histopathology, the current standard for staging, is relatively insensitive for detecting occult micrometastases and a significant fraction of patients are understaged and, consequently, undertreated. Similarly, current approaches to postoperative surveillance of patients with colorectal cancer detect disease recurrence at a point when interventions have little impact on survival. The detection of rare cells in tissue, for accurately staging patients, and in blood, for detecting disease recurrence, could be facilitated by employing sensitive and specific markers of disease. Guanylyl cyclase C (GCC), the receptor for the diarrheagenic bacterial heat-stable enterotoxin, is expressed selectively by cells derived from intestinal mucosa, including normal intestinal cells and colorectal tumor cells, but not by extragastrointestinal tissues and tumors. The nearly uniform expression of relatively high levels by metastatic colorectal tumors suggests that GCC may be a sensitive and specific molecular marker for metastatic colorectal cancer cells. Employing GCC reverse transcriptase PCR, occult colorectal cancer micrometastases were detected in lymph nodes that escaped detection by histopathology. Moreover, marker expression correlated with the risk of disease recurrence. Similarly, GCC reverse transcriptase PCR revealed the presence of tumor cells in blood of all patients examined with metastatic colorectal cancer and, in some studies, was associated with an increased risk of disease recurrence and mortality. These observations suggest that GCC reverse transcriptase PCR is a sensitive and specific technique for identifying tumor cells in extraintestinal sites and may be useful for staging and postoperative surveillance of patients with colorectal cancer.

Detection of disseminated pancreatic cells by amplification of cytokeratin-19 with quantitative RT-PCR in blood, bone marrow and peritoneal lavage of pancreatic carcinoma patients

AIM: To evaluate the diagnostic potential of cytokeratin-19 (CK-19) mRNA for the detection of disseminated tumor cells in blood, bone marrow and peritoneal lavage in patients with ductal adenocarcinoma of the pancreas.

METHODS: Sixty-eight patients with pancreatic cancer (n = 37), chronic pancreatitis (n = 16), and non-pancreatic benign surgical diseases (n = 15, control group) were included in the study. Venous blood was taken preoperatively, intraoperatively and at postoperative d 1 and 10. Preoperative bone marrow aspirates and peritoneal lavage taken before mobilization of the tumor were analyzed. All samples were evaluated for disseminated tumor cells by CK-19-specific nested-PCR and quantitative fluorogenic RT-PCR.

RESULTS: CK-19 mRNA expression was increased in 24 (64%) blood samples and 11 (30%) of the peritoneal lavage samples in the patients with pancreatic cancer. In 15 (40%) of the patients with pancreatic cancer, disseminated tumor cells were detected in venous blood and bone marrow and/or peritoneal lavage. In the peritoneal lavage, the detection rates were correlated with the tumor size and the tumor differentiation. CK-19 levels were increased in pT3/T4 and moderately/poorly differentiated tumors (G2/G3). Pancreatic cancer patients with at least one CK-19 mRNA-positive sample showed a trend towards shorter survival. Pancreatic cancer patients showed significantly increased detection rates of disseminated tumor cells in blood and peritoneal lavage compared to the controls and the patients with chronic pancreatitis.

CONCLUSION: Disseminated tumor cells can be detected in patients with pancreatic ductal adenocar-cinoma by CK-19 fluorogenic RT-PCR. In peritoneal lavage, detection rate is correlated with tumor stage and differentiation. In the clinical use, CK-19 is suitable for the distinction between malignant and benign pancreatic disease in combination with other tumor-specific markers.

Impact of disseminated tumor cells in gastrointestinal cancer

The detection of epithelial cells by sensitive immunological and molecular methods in blood, lymph nodes or bone marrow of gastrointestinal cancer patients may open a new approach to clinical metastasis research. The phenotypic and genomic characterization of these cells is of great value in the prediction of the further course of the disease and the monitoring of response to treatment. In addition, the role of ultrastaging in blood, lymph nodes and bone marrow of cancer patients for the indication of multimodal therapy is discussed in this review. The impact of prognostic or predictive factors for new treatment protocols in patients with gastrointestinal cancer was evaluated as well as the correlation with clinical factors.

Survivin mRNA in peripheral blood is frequently detected and significantly decreased following resection of gastrointestinal cancers

BACKGROUND AND OBJECTIVES

We evaluated if mRNA expression of survivin, an inhibitor of apoptosis, can be used to detect circulating tumor cells in peripheral blood of patients with various gastrointestinal cancers and if they decrease following complete surgical resection.

METHODS

Blood samples from 40 gastrointestinal cancer patients were analyzed prior and following surgical resection by direct quantitative real-time reverse transcriptase-PCR (RT-PCR) assays.

RESULTS

Survivin mRNA expression was pre-operatively detected in 35 of 40 cancer patients (88%). Post-operative survivin levels were significantly lower than pre-operative levels in 59% of resected patients and were non-detectable in 38% (Wilcoxon rank test: P < 0.04).

CONCLUSIONS

This is the first report showing that direct quantitative real-time RT-PCR analysis of survivin mRNA expression in peripheral blood of patients with gastrointestinal cancers is technically feasible. Survivin mRNA levels fall significantly following complete resection and might become a molecular marker for the completeness of surgical resection.

Real-time reverse transcription PCR (qRT-PCR) and its potential use in clinical diagnosis

qRT-PCR (real-time reverse transcription-PCR) has become the benchmark for the detection and quantification of RNA targets and is being utilized increasingly in novel clinical diagnostic assays. Quantitative results obtained by this technology are not only more informative than qualitative data, but simplify assay standardization and quality management. qRT-PCR assays are most established for the detection of viral load and therapy monitoring, and the development of SARS (severe acute respiratory syndrome)-associated coronavirus qRT-PCR assays provide a textbook example of the value of this technology for clinical diagnostics. The widespread use of qRT-PCR assays for diagnosis and the detection of disease-specific prognostic markers in leukaemia patients provide further examples of their usefulness. Their value for the detection of disease-associated mRNA expressed by circulating tumour cells in patients with solid malignancies is far less apparent, and the clinical significance of results obtained from such tests remains unclear. This is because of conceptual reservations as well as technical limitations that can interfere with the diagnostic specificity of qRT-PCR assays. Therefore, although it is evident that qRT-PCR assay has become a useful and important technology in the clinical diagnostic laboratory, it must be used appropriately and it is essential to be aware of its limitations if it is to fulfil its potential.

Molecular detection of clinical colorectal cancer metastasis: how should multiple markers be put to use?

BACKGROUND AND AIMS

Up to 45% of colorectal cancer (CRC) patients will develop local recurrence or metastasis following curative resection. The latter is due to cells shed from the primary carcinoma prior to or during surgery. The aim of this study was to contribute toward a "rational"-approach for detecting these disseminated tumor cells (DTC) using a combination of independent markers and detection methods.

PATIENTS/METHODS

Liver, lymph node, and bone marrow samples from 246 CRC patients were screened for DTC using three markers: mutated K-ras was detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), and cytokeratin 20 (CK20) and guanylylcyclase C (GCC), indicating circulating epithelial cells, were tracked by nested reverse-transcription (RT) PCR.

RESULTS

The rate of positive findings of the individual markers (CK20: 88%; GCC: 88%; K-ras: 67%) and their combinations (88-50%) was significantly higher in biopsies from liver metastases than in liver samples from patients without evident distant metastasis (M0; p<0.03). The detection rate of individual markers (except GCC) was also significantly elevated in inconspicuous liver tissue adjacent to metastasis compared with specimens from M0 patients. When using the concomitant detection of all three markers as criterion for DTC in the liver of M0 patients, however, no patient was DTC-positive. Therefore, the concomitant presence of the two CEC markers (CK20 plus GCC) and/or the presence of mutated K-ras were preferred for a combined evaluation, which resulted in a 24% detection rate for biopsies from both liver lobes. This translates into 39% of M0 patients with at least one positive liver biopsy.

CONCLUSION

Our results suggest that the concomitant detection of CK20 plus GCC and/or the presence of mutated K-ras are a rational approach for tracking CEC/DTC in CRC patients.

Quantitative real-time polymerase chain reaction: methodical analysis and mathematical model

Real-time polymerase chain reaction was established for 16 genes using the LightCycler system to evaluate gene expression in human hepatocytes. During the experiments a large set of data has been obtained. These data have now been evaluated with respect to template stability, accuracy of melting curve analysis, and reproducibility. In addition, the statistical evaluation of the efficiencies of all 16 polymerase chain reactions led to a new mathematical model. To examine template stability, the degradation of mRNA and cDNA was determined at different temperatures. Surprisingly, cDNA, which was obtained by first-strand synthesis, appeared to degrade significantly faster than the respective mRNA. Melting curve analysis is a fast and sensitive method to check for polymerase chain reaction specificity. However, we show that two transcription variants of the glutathione S-transferase 1 gene, with over 100 bp length difference, could not be distinguished by this method. Furthermore, an equation was set up describing the correlation between polymerase chain reaction efficiency and crossing point. This equation can be used to estimate the number of template molecules without having a standard of known concentration. Finally, experimental reproducibility of the real-time polymerase chain reaction was defined.

Identification of occult tumor cells in node negative lymph nodes of colorectal cancer patients by cytokeratin 20 gene and protein expression

BACKGROUND AND AIMS

Evaluation of cytokeratin 20 (CK20) specific quantitative reverse transcriptase polymerase chain reaction (QRT-PCR) and immunohistochemistry (IHC) for detection of occult tumor cells in lymph nodes of 72 patients with colorectal carcinoma (UICC stage I and II).

METHODS

Serial sections of formalin-fixed, paraffin-embedded lymph nodes (mean 14.3/case) were used for microdissection, RNA isolation and QRT-PCR and for CK20 IHC using routine protocols. Results of QRT-PCR and IHC were compared and correlated to the CK20 expression pattern of the primary tumors and clinical follow-up.

RESULTS

IHC revealed CK20-positive tumor cells in lymph nodes of 14.5% (10/69) and 0% (0/3) cases with a CK20-positive and CK20-negative primary tumor, respectively. CK20 mRNA was detected in the lymph nodes of 36.8% (7/19) cases by QRT-PCR with all 7 cases also expressing CK20 mRNA in the primary tumor. CK20 mRNA (QRT-PCR) and protein (IHC) detection in serial sections did not agree in 25% (5/20) of cases. A trend was seen towards a worse disease course for patients with CK20-positive lymph nodes by IHC (incidence of recurrent disease) and QRT-PCR (disease-free survival, incidence of recurrent disease).

CONCLUSION

CK20-specific IHC and QRT-PCR are supportive tools to conventional histology for detection of occult tumor cells in archival tissues, with the restriction that a laborious QRT-PCR procedure is necessary to achieve appropriate specificity. A prognostic value of CK20 IHC or QRT-PCR for stratification of UICC stage I and II patients into those likely to develop recurrent disease was not evident.

Quantitative real-time RT-PCR for detection of disseminated tumor cells in peripheral blood of patients with colorectal cancer using different mRNA markers

The detection of disseminated tumor cells in peripheral blood from colorectal cancer patients by RT-PCR could be an attractive method for selecting patients for adjuvant therapy. We here report on real-time RT-PCR assays (LightCycler) to quantitate potential mRNA markers. We investigated specimens from colon carcinoma and normal colon mucosa tissues, cell lines, blood samples from 129 patients with colorectal cancer (all stages) and 58 reference blood samples (healthy donors, persons suffering from inflammatory bowel or infectious diseases). The expression profile in tissues showed high values for CEA and CK20, whereas in cell lines ProtM was predominant. All markers were detected in reference and patient blood samples (ProtM, 22, 17%; CEA, 84, 86%; CK20, 85, 88%). After quantitative analysis, the definition of cutoff values for each marker and the combination of markers, 13% of patients were judged to have elevated marker concentrations in their blood, from which only 6 had values significantly differing from cutoff value. There were no differences between stages of disease. In the case of 19 patients, investigated prior to and 1 week after surgery, 2 samples revealed a significant postoperative increase in CEA or CK20 mRNA concentration. In spite of high expression levels in tissues and cell lines, we were not able to differentiate satisfyingly mRNA markers originating from tumor cells and those from illegitimate transcription in hematopoetic cells in blood. We conclude that either copy numbers of analyzed markers in circulating tumor cells are not sufficient for detection or, more probably, peripheral blood is not a suitable compartment for detection of tumor cells in colorectal cancer.

Detection of cancer cells in mesenteric vein and peripheral vessels by measuring telomerase activity in patients with colorectal cancer

BACKGROUND

Liver metastasis is an important factor determining prognosis in colorectal cancer. The objective of this study was to assess whether colorectal cancer cells in the drainage veins can be detected by measuring telomerase activity and its detection is correlated with liver metastasis.

METHODS

Telomeric repeat amplification protocol assay in combination with an immunomagnetic sorting was used for measuring telomerase activity of epithelial cells in blood samples collected from mesenteric (tumor-drainage) vein and peripheral vessels of 41 colorectal cancer patients. Telomerase activity was calculated as relative telomerase activity (RTA) against a control template and analyzed in terms of liver metastasis.

RESULTS

RTA of mesenteric blood samples was significantly higher in patients with liver metastasis (60.8%; n=7) than in those without metastasis (19.7%; n=34; P=.019). The RTA of peripheral blood sample was also higher in patients with liver metastasis (26.8%) than in those without metastasis (11.1%; p=.17). Moreover, 57% of cases with liver metastasis exhibited a positive telomerase activity in mesenteric blood sample, whereas it was 18% in cases without metastasis.

CONCLUSIONS

Our assay was proven to be a feasible method for detecting cancer cells in tumor-drainage veins. High telomerase activity of mesenteric blood samples reflected the existence of liver metastasis of colorectal cancer.

Cytokeratin 20 and guanylyl cyclase C mRNA is largely present in lymph node and liver specimens of colorectal cancer patients

The aim of our prospective study was to detect circulating epithelial cells (CEC) indicating the presence of disseminated tumor cells (DTC) in tissues affected by lymphatic and hematogenic colorectal cancer metastasis. DTC were tracked in lymph node, liver or bone marrow samples of 245 colorectal cancer patients using 2 independent RT-PCR assays for cytokeratin 20 (CK20) and guanylylcyclase C (GCC) that demonstrated a sensitivity of 1 colorectal cancer cell in 10(6) nucleated hematopoietic cells. CK20 mRNA was detected in 79% of lymph nodes, 35% of both liver lobes and 11% of bone marrow samples. GCC mRNA was found in 68% of lymph nodes, 60% of both liver lobes and 6% of bone marrow specimens. Both markers were recorded in 63% of lymph nodes, 45% of at least 1 liver lobe and 1% of bone marrow samples. There was no significant difference when comparing lymph node samples tested positive for both markers in patients with (N1/2; 65%) and without (N0; 56%) nodal involvement. The same was true when comparing the percentages of patients with and without clinically overt distant metastasis who were positive for both markers in at least 1 liver lobe (62% vs. 41%) or in bone marrow (4% vs. 0%). A score denoting the cumulative sum of tests indicating presence of CK20 and GCC mRNA in the liver was significantly related with UICC classification (p = 0.039). However, addition of lymph node results to this score decreased the correlation. The high incidence of clinically inconspicuous lymph node and liver samples tested positive for both markers emphasizes the function of these organs as primary filters for epithelial cells possibly shed from colorectal carcinomas. The potential prognostic significance of these findings warrants verification, especially regarding the importance of CEC or DTC resident in the liver of colorectal cancer patients.

hTERT mRNA expression correlates with telomerase activity in human breast cancer

AIMS

Telomerase is a ribonucleoprotein enzyme that synthesises telomeres after cell division and maintains chromosomal length and stability thus leading to cellular immortalisation. hTERT (human telomerase reverse transcriptase) gene seems to be the rate-limiting determinant of telomerase reactivation. hTERT mRNA expression was reported to correlate with telomerase activity in cell lines and some human tumours. However the correlation between telomerase activity and hTERT mRNA expression has not been previously examined in human breast cancer. The present study aims to quantitatively measure the expression of hTERT mRNA and telomerase activity in human breast cancer and examine the relationship between these parameters. Furthermore the associations with other parameters including estrogen receptor (ER) and progesterone receptor (PgR) status, DNA ploidy, and S-phase fraction (SPF) are also examined.

METHODS

RNA was extracted from 18 breast carcinomas and hTERT mRNA expressions were estimated by reverse transcriptase-PCR (RT-PCR) and Taqman methodology. These tumours had already been analysed for ER and PgR status using ligand-binding assays and had had their DNA ploidy and S-phase fractions measured by flow cytometry. Telomerase activity had already been determined by using a modified telomeric repeat and amplification protocol (TRAP) assay.

RESULTS

The expression of hTERT mRNA in the breast tumours ranged between 1.3 and 2.7 x 10(7) copy numbers per micro g of cellular RNA (the median value was 2.7x10(5) and the mean was 3.1 x 10(6)). Telomerase activity was between 0 and 246 units of Total Protein Generated (TPG), where one unit of TPG was equal to 600 molecules, of telomerase substrate primers extended by at least three telomeric repeats. The median level of TPG was 60 units and the mean level was 81 units). Telomerase activity was found to significantly correlate with hTERT expression (r(s)=0.51112, P=0.0302). There was no significant correlation between hTERT and other parameters.

CONCLUSION

hTERT mRNA expression significantly correlates with telomerase activity in human breast cancer. This is consistent with the hypothesis that hTERT is the catalytic and rate-limiting determinant subunit of the enzyme.

hTERT expression in human breast cancer and non-cancerous breast tissue: correlation with tumour stage and c-Myc expression

Telomerase is a ribonucleoprotein enzyme that synthesises telomeres after cell division and maintains chromosomal length and stability thus leading to cellular immortalisation. hTERT (human telomerase reverse transcriptase) gene is the rate-limiting determinant of telomerase reactivation. The present study aims to quantitatively measure the expression of hTERT mRNA in human breast cancer, adjacent non-cancerous tissue (ANCT) and benign breast lesions, examine the association between hTERT and the clinicopathological characteristics of the cancer specimens and to explore the relationship between c-Myc and hTERT expressions. RNA was extracted from 49 breast carcinomas, 46 matched ANCT, and eight fibroadenomas. hTERT and c-Myc mRNA expressions were estimated by reverse transcriptase-PCR (RT-PCR) and Taqman methodology. hTERT mRNA was present in all of the cancerous and most of ANCT specimens with levels being much higher in the cancerous tissue than in ANCT. The ratio of hTERT mRNA in tumour to that in ANCT was 2011 (95% confidence interval 373-10,853, P < 0.0001). There was no significant association between tumour hTERT expression and patient's age, tumour size, grade, nodal metastasis, estrogen receptor (ER) positivity, lymphovascular (LVI) or c-Myc expression. However, there was a weak but significant negative correlation between hTERT expression and progesterone receptor (PR) status (p = 0.04) in tumours. hTERT mRNA expression was also significantly higher in carcinomas (median = 2.61 x 10(6)) than in fibroadenomas (median = 424).We conclude that hTERT mRNA expression is significantly higher in human breast cancer than in non-cancerous breast tissue suggesting that hTERT has a potential role in breast cancer diagnosis. The hTERT mRNA levels in tumour do not seem to be associated with the patient's age or advanced tumour stage. Furthermore, hTERT mRNA expression does not correlate with c-Myc mRNA expression in breast cancer.

Quantification of cytokeratin 20, carcinoembryonic antigen and guanylyl cyclase C mRNA levels in lymph nodes may not predict treatment failure in colorectal cancer patients

Conventional histopathologic staging of primary colorectal cancers does not allow accurate prognostic stratification within a given tumour stage. Therefore, PCR-based assays are increasingly used to try to predict more accurately the likelihood of disease progression for the individual patient. Real-time reverse transcription PCR (RT-PCR) assays were used to detect and quantitate cytokeratin 20 (ck20), carcinoembryonic antigen (CEA) and guanylyl cyclase C (GCC) mRNA in 149 lymph nodes (LN) from 17 patients with benign disease and 302 LN from 42 patients with colorectal cancer who had curative (R0) resections. None of the markers were specific, with ck20, CEA and GCC mRNA detected in 47%, 89% and 13% of 149 LN, respectively, from patients with benign disease. The sensitivity of all 3 markers was very high, with mRNA detected in 93%, 100% and 97% of 30 histologically involved LN, respectively. There was significant overlap in the mRNA levels of all 3 markers between histologically involved and uninvolved LN. There was no association between mRNA levels and distant recurrence (median follow-up: 3.94 years, range 3.35-5.12). We conclude that the use of molecular techniques to detect occult disease in LN may suffer from the same limitations as conventional methods. Instead, accurate prognostic stratification requires careful assessment of the likely metastatic potential of the primary cancer.

Quantitative real-time reverse transcription polymerase chain reaction: normalization to rRNA or single housekeeping genes is inappropriate for human tissue biopsies

Careful normalization is essential when using quantitative reverse transcription polymerase chain reaction assays to compare mRNA levels between biopsies from different individuals or cells undergoing different treatment. Generally this involves the use of internal controls, such as mRNA specified by a housekeeping gene, ribosomal RNA (rRNA), or accurately quantitated total RNA. The aim of this study was to compare these methods and determine which one can provide the most accurate and biologically relevant quantitative results. Our results show significant variation in the expression levels of 10 commonly used housekeeping genes and 18S rRNA, both between individuals and between biopsies taken from the same patient. Furthermore, in 23 breast cancers samples mRNA and protein levels of a regulated gene, vascular endothelial growth factor (VEGF), correlated only when normalized to total RNA, as did microvessel density. Finally, mRNA levels of VEGF and the most popular housekeeping gene, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), were significantly correlated in the colon. Our results suggest that the use of internal standards comprising single housekeeping genes or rRNA is inappropriate for studies involving tissue biopsies.

Quantification of CK20 gene and protein expression in colorectal cancer by RT-PCR and immunohistochemistry reveals inter- and intratumour heterogeneity

Cytokeratin 20 (CK20) is an epithelial protein expressed almost exclusively in the gastrointestinal (GI) tract and is widely used as immunohistochemical marker for routine diagnosis. In contrast, CK20 gene expression is not an established marker for the classification of tumours and the detection of disseminated cancer cells in colorectal cancer. Recently, real-time reverse transcriptase polymerase chain reaction (RT-PCR) has provided the means for reproducible and quantitative investigation of molecular markers. This report directly compares CK20 mRNA and protein expression in serial sections of archival, formalin-fixed, paraffin-embedded (FFPE) colorectal adenocarcinomas. CK20 expression was detected by immunohistochemistry (IHC) in 60/63 (95.2%) cases, by conventional RT-PCR in 58/60 (96.7%) and by quantitative RT-PCR using the LightCycler (LightCycler is a trademark of a Member of the Roche Group) System in 29/32 (90.6%) microdissected cases, one case yielding variable results. Despite the high detection rate of all three techniques, marked heterogeneity of CK20 expression was seen between different cases and also within individual cases. CK20 expression profiles were not related to particular histopathological features of the tumours. A good correlation (r = 0.8964) was found between CK20 mRNA and protein expression by comparing quantitative RT-PCR with IHC in 32 cases. This was also true for selected heterogeneous tumour cells within individual cases. Both RT-PCR and IHC are therefore valuable tools for CK20 detection in colorectal adenocarcinoma, with real-time RT-PCR providing supplementary quantitative information. This suggests a promising supportive role for quantitative RT-PCR in molecular pathology.

Quantitative detection of CEA expressing free tumor cells in the peripheral blood of colorectal cancer patients during surgery with real-time RT-PCR on a LightCycler

We applied novel real-time reverse transcriptase-polymerase chain reaction (RT-PCR) with a LightCycler for quantitative detection of carcinoembryonic antigen (CEA) mRNA expressing tumor cells in the peripheral blood of colorectal cancer patients. Analysis of peripheral blood samples from 99 potentially curative colorectal cancer patients revealed a significantly higher mean CEA mRNA value in post-operative bloods (18.71) than in pre-operative blood (1.03) (P=0.003). Kaplan-Meier analysis demonstrated disease free survival of patients with positive CEA mRNA in post-operative blood to be significantly shorter than in cases negative for CEA mRNA (P=0.03). These results suggest that tumor cells could be shed into the bloodstream during surgical procedures, and these free tumor cells are accompanied by a poor patient outcome. Real-time quantitative RT-PCR is a useful technique for quantitative assessment of free tumor cells in the peripheral blood of colorectal cancer patients.

Quantitative detection of T-cell activation markers by real-time PCR in renal transplant rejection and correlation with histopathologic evaluation

BACKGROUND

The quest for noninvasive methods to diagnose rejection in solid-organ transplants has been rejuvenated by recent observations that specific cytotoxic T-cell markers are up-regulated during rejection.

METHODS

We developed a one-step real-time polymerase chain reaction (PCR) method allowing reliable detection of the expression of several T-cell genes within a relatively short period of time. The assay is highly sensitive and reproducible with a wide dynamic range allowing accurate quantification of target mRNA in as little as 3 pg total RNA. The utility of this assay in detecting renal allograft rejection was evaluated. Peripheral blood mononuclear cells were collected from 27 patients undergoing kidney allograft biopsies for renal dysfunction after transplantation. Expression of the T-cell activation markers, granzyme B, perforin, and HLA-DRA, was quantified and correlated to the histopathologic changes in the renal biopsies.

RESULTS

In cases with allograft rejection (n=8), peripheral lymphocyte expression was increased for granzyme B (P <0.001) and perforin (P <0.08) compared with cases without rejection (n=19). Granzyme B mRNA up-regulation showed the highest specificity for detecting rejection (95%). Moreover, HLA-DRA mRNA was significantly up-regulated (P <0.0016) and had the highest sensitivity (88%) detecting rejection. The up-regulation of both granzyme B and HLA-DRA was most specific in detecting rejection, P<0.001.

CONCLUSIONS

These data demonstrate that a rapid test of target gene up-regulation using real-time PCR can be used as an aid in the diagnosis of kidney allograft rejection. This is also the first report on the possible utility of HLA-DRA mRNA up-regulation as a marker for kidney transplant rejection.

Polymerase chain reaction in the staging of solid tumors

Polymerasechain reaction (PCR) is a molecular biology technique that holds great promise as a way to perform molecular staging of cancer by detecting very early metastatic disease. Significant data suggest that PCR analysis may play an important role in the management of colorectal cancer in the future. However, for PCR staging of breast cancer, progress awaits identification of gene markers that have sufficient sensitivity and specificity. Within the next few years, the results of the Sunbelt Melanoma Trial and other ongoing studies will determine whether PCR evaluation of sentinel lymph nodes and peripheral blood cells has prognostic relevance in melanoma. The future of cancer management will likely revolve around the molecular staging of tumors, and PCR is but one method that may better define subgroups of patients that are appropriate candidates forvarious anticancer therapies.

Evaluation of cytokeratin-19 mRNA as a tumor marker in the peripheral blood of nasopharyngeal carcinoma patients receiving concurrent chemoradiotherapy

The reverse transcriptase-polymerase chain reaction (RT-PCR) technique is a tool capable of detecting minute quantities of circulating tumor cell-derived transcripts. Nasopharyngeal carcinoma (NPC) is a rapidly growing tumor of epithelial origin and high metastatic potential. The aim of our study is to investigate the clinical value of circulating cytokeratin-19 (CK-19) mRNA detection in NPC patients. Between June 1997 and March 1999, 57 previously untreated, advanced NPC patients without distant metastasis were uniformly treated by concurrent chemoradiotherapy. Peripheral blood samples were collected prospectively before treatment and subjected to a nested RT-PCR assay. Measures were taken to prevent contamination and pseudogene interference. PCR products of positive results were verified by restriction enzyme Hae II and direct sequencing. Under our nested RT-PCR experimental conditions, 33.3% (19/57) clinically nonmetastatic NPC patients had CK-19 mRNA in their blood. The positive detection rates of CK-19 mRNA in the peripheral blood for different stages were 20.0% for stage II, 31.6% stage III and 43.5% stage IV (p = 0.1335). After a median follow-up time of 35 months, 2 patients had recurrences of their primary tumors and 14 developed distant metastases without locoregional recurrence. Nine of 19 (47.4%) CK-19 mRNA-positive patients and 5 of 38 (13.2%) CK-19 mRNA-negative patients developed distant metastasis (p = 0.00826). The 3-year metastasis-free survival rates were 49.9% for patients with detectable CK-19 and 85.9% for those with undetectable CK-19 (p = 0.0089, log-rank test). Our data suggest that the presence of CK-19 mRNA in the peripheral blood may be a potential marker of micrometastasis for NPC.

The mRNA expression of cyclo-oxygenase-2 (COX-2) and vascular endothelial growth factor (VEGF) in human breast cancer

AIMS

There is a growing body of evidence that cyclo-oxygenase 2 (COX-2) plays an important role in carcinogenesis and angiogenesis of human tumours. The present study aims to compare COX-2 expression in human breast cancer and adjacent non-cancerous tissue (ANCT), and to identify any correlation between COX-2 and VEGF expression.

METHODS

Total cellular RNA was extracted from frozen breast tissue samples according to standard methodology. The mRNA copy numbers for COX-2 and vascular endothelial growth factor 189 (VEGF-189) were determined 40 infiltrating carcinomas and 40 matched ANCT specimens using quantitative RT-PCR and TaqMan methodology.

RESULTS

The COX-2 mRNA copy number per microg of RNA was two-fold higher in ANCT compared with the cancerous tissue (p = 0.01). Median mRNA copy number was 5.44 x 10(6) for ANCT and 2.30 x 10(6) for tumour, (ANCT range: 1 x 10(6) to 4.12x 10(7)) (tumour range: 1.29 x 10(5) to 1.07 x 10(7)). There was a significant correlation between COX-2 and VEGF-189 mRNA copy numbers in the cancer specimens (correlation coefficient = 0.5528, p = 0.0076).

CONCLUSIONS

COX-2 mRNA is overexpressed in both human breast cancer and ANCT. We found higher levels in the matched ANCT which suggests that paracrine effects may be important in the role of COX-2 in mammary carcinogenesis. Furthermore, our results indicate that in human breast cancers COX-2 overexpression is linked to VEGF-189 overexpression and therefore tumour angiogenesis.