Limitations of cytokeratin 20 RT-PCR to detect disseminated tumour cells in blood and bone marrow of patients with colorectal cancer: expression in controls and downregulation in tumour tissue

Biomarkers of minimal residual disease and treatment

Minimal residual disease (MRD) has been defined as a very small numbers of cancer cells that remain in the body after curative treatment. Its presence or absence will ultimately determine prognosis. With the introduction of new technologies the presence of MRD in patients with solid tumours can be detected and characterized. As MRD predicts future relapse, be it early or late treatment failure, in an otherwise asymptomatic patient its treatment and when to start treatment remains to be determined. Thus the concepts of personalized medicine using different biomarkers to classify the biological properties of MRD maybe come possible. Based on this determinations it may be possible to use targeted therapies rather than all patients with the same type of cancer receiving a standard treatment. However, it is important to understand the limitations of the different technologies, what these techniques are detecting and how they may help in the treatment of patients with cancer. The majority of published studies are in patients with metastatic cancer and there are few reports in patients with MRD. In this chapter the concept of MRD, the methods used to detect it and what treatments may be effective based on the biological characteristics of the tumour cells as determined by different biomarkers is reviewed. MRD depends on the phenotypic properties of the tumour cells to survive in their new environment and the anti-tumour immune response. This is a dynamic process and changes with time in the wake of immunosuppression caused by the tumour cells and/or the effects of treatment to select resistant tumour cells. With the use of biomarkers to typify the characteristics of MRD and the development of new drugs a personalized treatment can be designed rather than all patients given the same treatment. Patients who are initially negative for MRD may not require further treatment with liquid biopsies used to monitor the patients during follow-up in order to detect those patients who may become MRD positive. The liquid biopsy used during the follow up of MRD positive patients can be used to detect changes in the biological properties of the tumour cells and thus may need treatment changes to overcome tumour cell resistance.

Assessment of circulating tumor cells in peripheral blood using flow cytometry in patients with surgery for colorectal cancer – review

Introduction: Colorectal cancer (CRC) is the third most common neoplasia in the world. Circulating tumor cells (CTC) have a prognostic value and can be useful in monitoring solid neoplasia. Only one method for CTC identification has received the approval and this is the CellSearch® system based on the immunomagnetic separation. Multiple markers are used in CTC identification, as epithelial markers and cytokeratines. CTC identification in peripheral blood is associated with a worse prognostic and reduced free survival in CRC.

Material and methods: We performed a systematic search in PubMed database for articles that reports the circulating tumor cells in CRC until July 2019. We selected studies in English and French and the main words used for search were ‘circulating tumor cells’, ‘colorectal cancer’, ‘colon cancer’, ‘rectal cancer’, ‘flow cytometry’, ‘peripheral blood’. We included studies with more than 10 patients, where samples were collected from the blood in relation with surgery and flow cytometry was used as analyzing technique.

Results: We included 7 studies in final analysis, that showed in flow cytometry analysis a cut-off value of CTC that can vary from 2-4 CTC/ 7.5 ml peripheral blood with a sensitivity of 50.8% and specificity of 95%. Patients with positive CTC were associated with higher T stage and positive lymph nodes, with a worse overall survival (OS) and disease free survival (DFS) comparing with negative patients.

Conclusion: CTC are considered to be a prognostic factor who needs more validation studies in order to be included in the clinical practice.

Common molecular markers between circulating tumor cells and blood exosomes in colorectal cancer: a systematic and analytical review

Nearly half of patients with colorectal cancer (CRC), the third leading cause of cancer deaths worldwide, are diagnosed in the late stages of the disease. Appropriate treatment is not applied in a timely manner and nearly 90% of the patients who experience metastasis ultimately die. Timely detection of CRC can increase the five-year survival rate of patients. Existing histopathological and molecular classifications are insufficient for prediction of metastasis, which limits approaches to treatment. Detection of reliable cancer-related biomarkers can improve early diagnosis, prognosis, and treatment response prediction and recurrence risk. Circulating tumor cells (CTCs) and exosomes in peripheral blood can be used in a liquid biopsy to assess the status of a tumor. Exosomes are abundant and available in all fluids of the body, have a high half-life and are released by most cells. Tumor-derived exosomes are released from primary tumors or CTCs with selective cargo that represents the overall tumor. The current systematic review highlights new trends and approaches in the detection of CRC biomarkers to determine tumor signatures using CTC and exosomes. When these are combined, they could be used to guide molecular pathology and can revolutionize detection tools. Relevant observational studies published until July 24, 2019 which evaluated the expression of tumor markers in CTCs and exosomes were searched in PubMed, Scopus, Embase, and ISI Web of Science databases. The extracted biomarkers were analyzed using String and EnrichR tools.

The Potential for Circulating Tumor Cells in Pancreatic Cancer Management

Pancreatic cancer is one the most lethal malignancies. Only a small proportion of patients with this disease benefit from surgery. Chemotherapy provides only a transient benefit. Though much effort has gone into finding new ways for early diagnosis and treatment, average patient survival has only been improved in the order of months. Circulating tumor cells (CTCs) are shed from primary tumors, including pre-malignant phases. These cells possess information about the genomic characteristics of their tumor source in situ, and their detection and characterization holds potential in early cancer diagnosis, prognosis, and treatment. Liquid Biopsies present an alternative to tumor biopsy that are hard to sample. Below we summarize current methods of CTC detection, the current literature on CTCs in pancreatic cancer, and future perspectives.

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.

Molecular biomarkers for the detection of metastatic colorectal cancer cells

Approximately half of all patients with colorectal cancer develop local recurrence or distant metastasis during the course of their illness. Recently, the molecular detection of metastatic cancer cells in various types of clinical samples, such as lymph nodes, bone marrow, peripheral blood, and peritoneal lavage fluid, has been investigated as a potential prognostic marker. The prognostic value of molecular tumor cell detection was independent of the type of detection method used. As assays become more sensitive and quantitative, a more thorough assessment of the cancer status of patients will be based on molecular markers alone. At present, it is difficult to conclude that one specific molecular marker is superior to others. Comparative analyses are recommended to assess the prognostic impact of molecular analyses in the same patient and determine the biomarkers that provide the most accurate prognostic information.

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.

Evaluation of laparoscopic resection of colorectal carcinoma from the viewpoint of molecular biology

AIM

Detection of the possible impact of surgical management on the occurrence of minimal residual disease (MRD) in patients with colorectal carcinoma (CRC) in bone marrow samples, portal and peripheral blood samples. Comparison of MRD prevalence in patients with laparoscopic resection of CRC and those with open colorectal resection. Assessment of the potential impact of MRD on the relapse of the disease and overall survival of patients.

MATERIAL AND METHODS

The study included 124 patients with primary CRC without proven distant metastases indicated for elective laparoscopic resection and operated on between September 21, 2006 and December 31, 2008 at the Department of Surgery, Hospital and J.G. Mendel Oncological Centre Novy Jicin. 6 samples were collected from each patient to determine MRD (system venous blood and bone marrow at the beginning of surgery, venous blood from mesenteric bloodstream, system venous blood after the resection, system venous blood and bone marrow 1 month after the surgery). Detection of MRD on the basis of CEA expression was performed by real-time RT-PCR technique. The results were compared with those obtained within the similar research using the same methodology at the 2(nd) Department of Surgery, University Hospital in Olomouc (the group included 230 patients treated with open resection of CRC).

RESULTS

In the group of patients treated with laparoscopic resection, a correlation between positive MRD in the sample of bone marrow collected before the surgery and the stage of the disease was found (p < 0.035). We also recorded the impact of surgical management on MRD occurrence in system venous blood in primary negative patients (p < 0.025). However, in the course of the short period of time we have not found a statistically significant correlation between the finding in patients with stage I-III, and the period prior to the relapse of the disease (p < 0.59). With regard to the results obtained, we can expect a potential direct correlation between a positive MRD finding in system venous blood taken prior to surgery in patients with stage I-III CRC and shorter time of survival (p < 0.075). In the group of patients treated with open resection of CRC, no statistically significant relationship between the stage of the disease and MRD occurrence was found. Incidence of circulating tumour cells (CTC) in the samples of venous blood taken prior to surgery is a prognostically important factor (p < 0.05) from the viewpoint of disease-free survival (DFS). Another prognostically important factor with regard to DFS seems to be the occurrence of disseminated tumour cells (DTC) in the bone marrow taken 1 month after the surgery.

CONCLUSIONS

The data recorded suggest a relationship between MRD finding and the disease prognosis. Collection of samples as well as evaluation of results continue as we strive to include more patients in our study and to obtain more data within 5-10 years of the follow-up. The comparison between the data obtained in the laparoscopic approach and the data obtained in open resection performed from the viewpoint of molecular biology did not show a significant difference in MRD detection in the samples collected after the surgery.

Molecular tests for colorectal cancer screening

Detecting and removing high-risk adenomas and early colorectal cancer (CRC) can reduce mortality of this disease. The noninvasive fecal occult blood test (FOBT; guaiac-based or immunochemical) is widely used in screening programs and although effective, it leaves room for improvement in terms of test accuracy. Molecular tests are expected to be more sensitive, specific and informative than current detection tests, and are promising future tools for CRC screening. This review provides an overview of the performances of DNA, RNA, and protein markers for CRC detection in stool and blood. Most emphasis currently is on DNA and protein markers. Among DNA markers there is trend to move away from mutation markers in favor of methylation markers. The recent boost in proteomics research leads to many new candidate protein markers. Usually in small series, some markers show better performance than the present FOBT. Evaluation in large well-controlled randomized trials is the next step needed to take molecular markers for CRC screening to the next level and warrant implementation in a screening setting.

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.

Multiplex RT-PCR-based detections of CEA, CK20 and EGFR in colorectal cancer patients

AIM: To develop a multiplex reverse transcription polymerase chain reaction (RT-PCR) method detecting circulating tumor cells in the peripheral blood of colorectal cancer (CRC) patients.

METHODS: Peripheral blood samples were collected from 88 CRC patients and 40 healthy individuals from the blood donors’ clinic and subsequently analyzed by multiplex RT-RCR for the expression of carcinoembryonic antigen (CEA), cytokeratin 20 (CK20) and epidermal growth factor receptor (EGFR) mRNA. The analysis involved determining the detection rates of CEA, CK20 and EGFR transcripts vs disease stage and overall survival. Median follow-up period was 19 mo (range 8-28 mo).

RESULTS: Rates of CEA, CK20 and EGFR detection in CRC patients were 95.5%, 78.4% and 19.3%, respectively. CEA transcripts were detected in 3 healthy volunteer samples (7.5%), whereas all control samples were tested negative for CK20 and EGFR transcripts. The increasing number of positive detections for CEA, CK20 and EGFR transcripts in each blood sample was positively correlated with Astler-Coller disease stage (P < 0.001) and preoperative serum levels of CEA (P = 0.029) in CRC patients. Data analysis using Kaplan-Meier estimator documented significant differences in the overall survival of the different CRC patient groups as formed according to the increasing number of positivity for CEA, CK20 and EGFR transcripts.

CONCLUSION: These data suggest that multiplex RT-PCR assay can provide useful information concerning disease stage and overall survival of CRC patients.

Implications of cancer-associated systemic inflammation for biomarker studies

Highly sensitive molecular technologies provide new capacities for cancer biomarker research, but with sensitivity improvements marker specificity is significantly decreased, and too many false-positive results should disqualify the measurement from clinical use. Hence, of the thousands of potential cancer biomarkers only a few have found their way to clinical application. Differentiating false-positive results from true-positive (cancer-specific) results can indeed be difficult, if validation of a marker is performed against inadequate controls. We present examples of accumulating evidence that not only local but also systemic inflammatory reactions are implicated in cancer development and progression and interfere with the molecular image of cancer disease. We analyze several modern strategies of tumor marker discovery, namely, proteomics, metabonomics, studies on circulating tumor cells and circulating free nucleic acids, or their methylation degree, and provide examples of scarce, methodologically correct biomarker studies as opposed to numerous methodologically flawed biomarker studies, that examine cancer patients' samples against those of healthy, inflammation-free persons and present many inflammation-related biomarker alterations in cancer patients as cancer-specific. Inflammation as a cancer-associated condition should always be considered in cancer biomarker studies, and biomarkers should be validated against their expression in inflammatory conditions.

Evaluation of plakophilin-3 mRNA as a biomarker for detection of circulating tumor cells in gastrointestinal cancer patients

BACKGROUND

This study aims to assess Plakophilin-3 (PKP3) as a surrogate biomarker of circulating tumor cells in patients with gastrointestinal cancer.

METHODS

The primary aim is to estimate the diagnostic accuracy of PKP3 real-time reverse transcriptase-PCR in blood. Receiver operating characteristic curves were constructed. Correlations between the blood PKP3 levels and the clinicopathologic features of the study subjects were analyzed. Logistic regression was used to predict outcomes based on PKP3.

RESULTS

Sixty-four patients with gastrointestinal cancer and 23 controls were included. The mean relative PKP3 mRNA expression was 48.45 in cancer patients and 2.8 in controls (P < 0.0001). Comparing the PKP3 levels in patients and controls, the area under the curve was 0.852 (95% confidence interval, 0.76-0.94; P < 0.0001) in receiver operating characteristic analysis. A higher blood level of PKP3 mRNA was associated with a more advanced stage (P = 0.025), pT(3-4) tumors (P = 0.028), metastasis (P = 0.021), and residual (R2) disease (P = 0.037). Higher PKP3 mRNA was associated with the risk of cancer progression and death (odds ratio, 3.875; 95% confidence interval, 1.781-8.430; P = 0.001).

CONCLUSIONS

Increased PKP3 mRNA was detected in the blood of gastrointestinal cancer patients. Significant correlations were found with advanced stage, pT(3-4), metastatic disease, and the residual disease status. PKP3 mRNA in blood was associated with the risk of cancer progression and death.

IMPACT

PKP3 mRNA can be used as a marker of subclinical disease in gastrointestinal cancer and thus holds potential clinical relevance as a predictor for disease outcome.

Detection of circulating tumor cells in peripheral blood from patients with gastric cancer using microRNA as a marker

Recently, the detection of occult cancer cells in peripheral blood has received a great deal of attention regarding the prediction of postoperative cancer recurrence and for novel strategies of adjuvant therapy. The aim of this study was to establish a new molecular diagnostic method of detecting circulating tumor cells. Gastric cancer SGC-7901 cells in 2 ml blood from healthy volunteers were serially diluted. Additional peripheral blood samples were collected from 90 patients and 27 healthy volunteers. Real-time reverse transcription-polymerase chain reaction was used to detect the levels of microRNA-106a (miR-106a) and microRNA-17 (miR-17). Receiver operating characteristics (ROC) curves were constructed. In recovery experiments, a significant correlation between the number of cancer cells and the levels of both miR-106a (r = -0.906, p = 0.037) and miR-17 (r = -0.912, p = 0.031) was found. In preoperative and postoperative patient groups, miR-106a and miR-17 levels were significantly higher than those in controls. The areas under the ROC curve for miR-106a, miR-17, and combination were 0.684 (p = 0.0066), 0.743 (p = 0.0001), and 0.741 (p = 0.0002), respectively. Our results indicate that the detection of miRNA in peripheral blood may be a novel tool for monitoring circulating tumor cells in patients with gastric cancers.

Clinical relevance associated to the analysis of circulating tumour cells in patients with solid tumours

The distant growth of tumour cells escaping from primary tumours, a process termed metastasis, represents the leading cause of death among patients affected by malignant neoplasias from breast and colon. During the metastasis process, cancer cells liberated from primary tumour tissue, also termed circulating tumour cells (CTCs), travel through the circulatory and/or lymphatic systems to reach distant organs. The early detection and the genotypic and phenotypic characterisation of such CTCs could represent a powerful diagnostic tool of the disease, and could also be considered an important predictive and prognostic marker of disease progression and treatment response. In this article we discuss the potential relevance in the clinic of monitoring CTCs from patients suffering from solid epithelial tumours, with emphasis on the impact of such analyses as a predictive marker for treatment response.

Cancer micrometastasis and tumour dormancy

Many epithelial cancers carry a poor prognosis even after curative resection of early stage tumours. Tumour progression in these cancer patients has been attributed to the existence and persistence of disseminated tumour cells (DTC) in various body compartments as a sign of minimal residual disease. Bone marrow (BM) has been shown to be a common homing organ and reservoir for DTC. A significant correlation between the presence of DTC in BM and metastatic relapse has been reported in various tumour types. However, only a portion of patients with DTC in BM at primary surgery relapse. Thus far, little is known about the conditions required for the persistence of dormancy or the escape from the dormant phase into the active phase of metastasis formation. Thereby, this peculiar stage of conceivably balanced tumour cell division and death may last for decades in cancer patients. Most likely, the ability of a dormant DTC to "be activated" is a complex process involving (i) somatic aberrations in the tumour cells, (ii) the interaction of the DTC with the new microenvironment at the secondary site, and (iii) hereditary components of the host (i.e., cancer patient). In this review, we will summarize the key findings of research on micrometastatic cancer cells and discuss these findings in the context of the concept of tumour dormancy.

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.

Bioinformatics approach to mRNA markers discovery for detection of circulating tumor cells in patients with gastrointestinal cancer

BACKGROUND

Detection of tumor cells in the blood, or minimal deposits in distant organs as bone marrow, could be important to identify cancer patients at high risk of relapse or disease progression. Quantitative polymerase chain reaction (PCR) amplification of tissue or tumor selective mRNA is the most powerful tool for the detection of this circulating or occult metastatic cells. Our study aims to identify novel gastrointestinal cancer-specific markers for circulating tumor cell detection.

METHOD

Phase I preclinical study was performed by means of computational tools for expression analysis. In silico data were used to identify and prioritize molecular markers highly expressed in gastrointestinal cancers but absent in hematopoietic-derived libraries. Selected genes were evaluated by means of qRT-PCR in gastrointestinal cancer and hematopoietic cell-lines, normal human bone marrows and bloods, tumor tissue, and blood from cancer patients.

RESULTS

Novel and known mRNA markers for circulating tumor cell detection in gastrointestinal cancer have been identified. Among all the genes assessed, PKP3, AGR2, S100A16, S100A6, LGALS4, and CLDN3 were selected and assays based on blood qRT-PCR were developed. Reliably qRT-PCR assays for the novel targets plakophilin 3 (PKP3) and anterior gradient-2 (AGR2) to identify blood-borne cells in cancer patients were developed.

CONCLUSIONS

Novel and known gastrointestinal-specific mRNA markers for circulating tumor cells have been identified through in silico analysis and validated in clinical material. qRT-PCR assay targeted to PKP3 and AGR2 mRNAs might be helpful to detect circulating tumor cells in patients with gastrointestinal cancer.

Relationship between vascular invasion and microvessel density and micrometastasis

AIM

To evaluate the relationship between vascular invasion and microvessel density (MVD) of tissue and micrometastasis in blood.

METHODS

Vascular invasion was detected by both hematoxylin and eosin staining and immunohistochemiscal staining. Blood samples were collected from 17 patients with vascular invasion and 29 patients without vascular invasion and examined for cytokeratin20 (CK20) expression by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. Microvessel density of tissue samples was also determined by immunohistochemistry using antibodies to CD105.

RESULTS

CK20 was detected in 12 of the 17 patients with vascular invasion and in 9 of the 29 patients without vascular invasion. Positive RT-PCR was significantly correlated with vascular invasion (70.6% vs 30.0%, P < 0.05). The average MVD was significantly higher in patients with positive vascular invasion than in patients with negative vascular invasion (29.2 +/- 3.3 vs 25.4 +/- 4.7, P < 0.05). The vascular invasion detected with hematoxylin-eosin staining was less than that with immunohistochemical staining. There was a significant difference between the two staining methods (19.6% vs 36.9%, P < 0.05).

CONCLUSION

Positive CK20 RT-PCR, depth of tumor invasion, lymph node status, metastasis and MVD are significantly correlated with vascular invasion. Immunohistochemical staining is more sensitive than hematoxylin-eosin staining for detecting vascular invasion.

Quantitative RT-PCR detection of colorectal tumor cells in peripheral blood--a systematic review

BACKGROUND

Twenty percent to 40% of patients with node-negative colorectal cancer die of metastatic disease. Detection of cancer cell dissemination has been proposed as a tool to select patients at highest risk for recurrence. In this review, we summarize the evidence for detection with quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) assays of circulating tumor cells (CTCs) in peripheral blood of colorectal cancer patients.

MATERIALS AND METHODS

Pubmed and Embase were systematically searched for all English publications relevant to circulating cancer cells, peripheral blood, quantitative RT-PCR (q-RT-PCR), and colorectal cancer. Cross-references and the "related articles" function were used to broaden the search. Manuscripts reporting on the results of nonquantitative RT-PCR assays were excluded. The study methodology, CTCs detection rates in peripheral blood, and prognostic value were reviewed.

RESULTS

Twelve manuscripts on qRT-PCR were retrieved. Stage dependence was found for detection of CTCs in four of 10 studies. From univariate analysis performed for disease-free survival and overall survival in 4 of 12 studies, there was evidence (P < 0.05) for an effect of the detection of CTCs with qRT-PCR. None of the included trials identified detection of CTCs in peripheral blood as an independent predictor of survival.

CONCLUSION

Quantification of CTCs in peripheral blood holds promise in predicting stage and outcome in colorectal cancer patients. At present, evidence from the literature is too scarce to integrate quantitative RT-PCR assays to detect CTCs into the management of colorectal cancer.

Blood markers for early detection of colorectal cancer: a systematic review

BACKGROUND

Despite different available methods for colorectal cancer (CRC) screening and their proven benefits, morbidity, and mortality of this malignancy are still high, partly due to low compliance with screening. Minimally invasive tests based on the analysis of blood specimens may overcome this problem. The purpose of this review was to give an overview of published studies on blood markers aimed at the early detection of CRC and to summarize their performance characteristics.

METHOD

The PUBMED database was searched for relevant studies published until June 2006. Only studies with more than 20 cases and more than 20 controls were included. Information on the markers under study, on the underlying study populations, and on performance characteristics was extracted. Special attention was given to performance characteristics by tumor stage.

RESULTS

Overall, 93 studies evaluating 70 different markers were included. Most studies were done on protein markers, but DNA markers and RNA markers were also investigated. Performance characteristics varied widely between different markers, but also between different studies using the same marker. Promising results were reported for some novel assays, e.g., assays based on SELDI-TOF MS or MALDI-TOF MS, for some proteins (e.g., soluble CD26 and bone sialoprotein) and also for some genetic assays (e.g., L6 mRNA), but evidence thus far is restricted to single studies with limited sample size and without further external validation.

CONCLUSIONS

Larger prospective studies using study populations representing a screening population are needed to verify promising results. In addition, future studies should pay increased attention to the potential of detecting precursor lesions.

Circulating tumor cells in colorectal cancer: correlation with clinical and pathological variables

BACKGROUND

The CellSearch System is a technique to detect circulating tumor cells (CTCs) in patients with cancer. Few data have been published concerning the role of CTCs detection by this method in colorectal cancer. The aim of this study was to correlate the presence of CTCs with the commonest clinical and morphological variables.

PATIENTS AND METHODS

Blood samples were collected from 97 patients and 30 healthy volunteers. Quantification of CTCs in 7.5 ml of blood was carried out with the CellSearch System. The results were expressed as number of CTCs/7.5 ml and the cut-off of >or=2 CTCs/7.5 ml was chosen to define the test as positive.

RESULTS

Positive CTCs were detected in 34 of 94 patients (36.2%). Correlation was not found among positive CTCs and location of primary tumor, increased carcinoembryonic antigen level, increased lactate dehydrogenase level or grade of differentiation. Only stage correlated with positive CTCs (20.7% in stage II, 24.1% in stage III and 60.7% in stage IV, P = 0.005).

CONCLUSIONS

CTCs detection by CellSearch is a highly reproducible method that correlates with stage but not with other clinical and morphological variables in patients with colorectal cancer. Colon cancer tumor cells are detectable in all stages. Further studies are warranted.

Relationship between vascular invasion and microvessel density and micrometastasis

AIM: To evaluate the relationship between vascular invasion and microvessel density (MVD) of tissue and micrometastasis in blood.

METHODS: Vascular invasion was detected by both hematoxylin and eosin staining and immunohistochemiscal staining. Blood samples were collected from 17 patients with vascular invasion and 29 patients without vascular invasion and examined for cytokeratin20 (CK20) expression by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. Microvessel density of tissue samples was also determined by immunohistochemistry using antibodies to CD105.

RESULTS: CK20 was detected in 12 of the 17 patients with vascular invasion and in 9 of the 29 patients without vascular invasion. Positive RT-PCR was significantly correlated with vascular invasion (70.6% vs 30.0%, P < 0.05). The average MVD was significantly higher in patients with positive vascular invasion than in patients with negative vascular invasion (29.2 ± 3.3 vs 25.4 ± 4.7, P < 0.05). The vascular invasion detected with hematoxylin-eosin staining was less than that with immunohistochemical staining. There was a significant difference between the two staining methods (19.6% vs 36.9%, P < 0.05).

CONCLUSION: Positive CK20 RT-PCR, depth of tumor invasion, lymph node status, metastasis and MVD are significantly correlated with vascular invasion. Immunohistochemical staining is more sensitive than hematoxylin-eosin staining for detecting vascular invasion.

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.

Immunomagnetic CD45 depletion does not improve cytokeratin 20 RT-PCR in colorectal cancer

BACKGROUND

Cytokeratin 20 reverse transcriptase polymerase chain reaction (CK20 RT-PCR) of blood and bone marrow specimens has been suggested for assessment of hematogenously disseminated tumor cell (DTC) spread in colorectal cancer (CRC) patients. Considerable discrepancies among the studies reported indicate a need for better evaluation procedures. We investigated whether mononucleated cell (MNC) enrichment by Ficoll density gradient centrifugation followed by immunomagnetic depletion of CD45-positive cells (extended enrichment) allows better detection of DTC-associated CK20 mRNA compared to MNC enrichment by Ficoll density gradient centrifugation alone (Ficoll enrichment).

METHODS

We analyzed 53 samples [38 peripheral blood (PB), 15 bone marrow (BM)] from 38 CRC patients. Extended enrichment was performed for 30 specimens (PB and BM, n=15 each), and Ficoll enrichment for 23 blood specimens. Total RNA was extracted, reverse-transcribed and analyzed by real-time RT-PCR using a LightCycler instrument.

RESULTS

Despite extended enrichment, 10 PB and 8 BM samples could not be analyzed because of low cellular yield. The depletion efficiency of CD45 separation was 2 log. RT-PCR of the housekeeping gene PBGD resulted in high and varied crossing point values (mean 37.1+3.0) for five PB and seven BM specimens. Ficoll enrichment yielded 23 analyzable blood specimens for which the mean crossing point value was 26.7+0.5 in PBGD RT-PCR. CK20 RT-PCR of 23 blood samples (all from Dukes D patients) revealed CK20 transcripts in four cases (17%).

CONCLUSIONS

Extended enrichment was not superior to Ficoll enrichment; in fact, the sensitivity was lower. Improvement of the reported CK20 RT-PCR assay of Ficoll-enriched MNC populations is warranted.

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.

Detection of carcinoembryonic antigen messenger RNA-expressing cells in peripheral blood 7 days after curative surgery is a novel prognostic factor in colorectal cancer

BACKGROUND

The significance of detection of circulating cancer cells in blood during surgery in patients with colorectal cancer (CRC) remains controversial. Experimental study revealed that the cancer cells injected from the vein disappeared completely until 7 days. The aim of this study was to clarify that the detection of circulating cancer cells in blood taken later than 7 days after curative surgery may be a prognostic factor.

METHODS

Two hundred consecutive patients with CRC who underwent potentially curative surgery were the subjects. Peripheral blood was collected between 7 and 10 days after resection. Cancer cells were detected using reverse transcriptase-polymerase chain reaction targeting carcinoembryonic antigen (CEA) messenger RNA (mRNA). The median follow-up period was 52 months (range: 34-69 months).

RESULTS

The overall positive incidence of CEA mRNA was 22%. Detection of CEA mRNA was not significantly related to conventional clinicopathological findings. Recurrence has been confirmed in 55 patients (28%). The recurrence rate was significantly higher in patients with rectal cancer, deep penetration, lymph node metastasis, preoperative chemoradiotherapy and positive CEA mRNA. The CEA mRNA positive patients showed significantly poorer disease free survival (DFS) and overall survival (OS) than the negative patients (DFS, P = 0.007; OS, P = 0.04). Multivariate analysis revealed that the positive expression of CEA mRNA (P < 0.01) as well as the tumor location and TNM stage classification was identified as the significant risk factors for recurrence.

CONCLUSIONS

Detection of CEA mRNA expressing cells in peripheral blood 7 days after curative surgery is a novel independent factor predicting recurrence in patients with CRC.

Quantitative real-time RT-PCR detection for CEA, CK20 and CK19 mRNA in peripheral blood of colorectal cancer patients

This study is aimed at establishing a sensitive approach to detect disseminated tumor cells in peripheral blood and evaluate its clinical significance. A total of 198 blood samples including 168 from colorectal carcinoma (CRC) patients and 30 from healthy volunteers were examined by quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) to evaluate the expression of carcinoembryonic antigen (CEA), cytokeratin 20 (CK20) and cytokeratin 19 (CK19) mRNA. CEA mRNA was detected in 35.8% of patients and 3.3% of controls, CK20 mRNA in 28.3% of patients and 6.7% of controls, and CK19 mRNA in 41.9% of patients and 3.3% of controls. CEA and CK20 mRNA positive ratio increased with the advancing Dukes stages, but there was no significant difference in positive ratio between any two stages (P>0.05). Also, relatively high positive ratio of CEA, CK20 and CK19 mRNA expression was observed in some CRC patients with earlier Dukes stages. A higher positive ratio was obtained when two or three detection markers were combined compared to a single marker. Our study indicates that quantitative real-time RT-PCR detection for CEA, CK20 and CK19 mRNA in peripheral blood is a valuable tool for monitoring early stage dissemination of CRC cells in blood circulation.

Specific detection of cytokeratin 20-positive cells in blood of colorectal and breast cancer patients by a high sensitivity real-time reverse transcriptase-polymerase chain reaction method

A real-time reverse transcriptase-polymerase chain reaction (RT-PCR) method for detection of cytokeratin 20-positive cells in blood characterized by two novel features was developed and tested on 99 patients with colorectal cancer, 110 with breast cancer, and 150 healthy subjects. To optimize the specificity and sensitivity of the method, two novel features were used. First, a primer overlapping two adjacent exons was generated to inhibit nonspecific amplification both in healthy donors and cancer patients; second, a non-end-point first-round amplification was used to increase sensitivity. The number of first-round cycles was chosen to reach the highest level of sensitivity while conserving quantitative characteristics. PCR efficiency increased from 88.9% in single-round RT-PCR to 99.0% in nested real-time RT-PCR. To establish sensitivity and specificity of the method, HT29 cells were serially diluted with normal blood. Detection limit improved from 100 HT29 cells (single-round RT-PCR) to 1 to 10 cells (nested real-time RT-PCR) per 3 ml of whole blood. None of the healthy subjects was positive, whereas 22 and 29% of all colorectal and breast cancer patients, respectively, had cytokeratin 20 cell equivalents in blood. The association between cytokeratin 20 cell equivalents and metastasis was statistically significant for breast (P = 0.026) but not colorectal cancer patients (P = 0.361). Negativity of all 150 healthy controls examined confers diagnostic potential to the method.

Molecular detection of circulating tumor cells in the peripheral blood of patients with colorectal cancer using RT-PCR: significance of the prediction of postoperative metastasis

BACKGROUND

Approximately 20%-45% of colorectal cancer (CRC) patients ultimately develop local recurrence or metastasis following curative surgical resection. The latter is caused by tumor cells shed from the primary carcinoma prior to or during operation, currently undetected by standard clinical staging. Fortunately, the presence of tumor cells in peripheral blood can be detected by molecular methods and is being regarded increasingly as a clinically relevant prognostic factor.

MATERIALS AND METHODS

To detect the presence of circulating tumor cells and evaluate their relationship to postoperative metastatic relapse, we simultaneously examined human telomerase reverse transcriptase (hTERT), cytokeratin-19 (CK-19), cytokeratin-20 (CK-20), and carcinoembryonic antigen (CEA) mRNA (messenger RNA) in the peripheral blood of 72 CRC patients and 30 healthy individuals. Using a reverse-transcriptase polymerase chain reaction (RT-PCR), these tumor-related mRNAs were amplified; in addition, analyses were carried out for their correlation with patients' clinicopathologic features, as well as the occurrence of postoperative metastasis.

RESULTS

In RT-PCR analysis of the peripheral blood, 69.4% (50 out of 72), 66.7% (48 out of 72), 52.8% (38 out of 72), and 72.2% (52 out of 72) of CRC patients were positive for hTERT, CK-19, CK-20, and CEA mRNA respectively. All 30 healthy individuals were negative for hTERT and CEA mRNA expression, while 2 were positive for either CK-19 mRNA or CK-20 mRNA expression. The detection of CEA mRNA was significantly correlated with depth of tumor invasion (P=0.012), vessel invasion (P=0.035), TNM stage (P<0.0001), and postoperative metastasis (P<0.0001), while positive hTERT mRNA was correlated with TNM stage (P=0.037) and CK-19 was correlated with depth of tumor invasion (P=0.039) and postoperative metastasis (P=0.017). In addition, multivariate logistic regression showed that only CEA mRNA was an independent and significant predictor of postoperative metastasis (P=0.006). Our findings suggest that CEA mRNA may be a more reliable marker than hTERT, CK-19, and CK-20 for the detection of circulating cancer cells in the peripheral blood of CRC patients.

CONCLUSIONS

Using RT-PCR for the detection of CEA mRNA is feasible and may be a promising tool for early detection of micrometastatic circulating tumor cells in CRC patients. CRC patients expressing positive CEA mRNA in peripheral blood have a significantly higher risk of postoperative metastasis. Nevertheless, confirmation of CEA mRNA as a prognostic predictive factor requires the continuation of patient follow-up.

Nucleic acid quantification and disease outcome prediction in colorectal cancer

Histopathological stage at diagnosis remains the most important prognostic determinant for colorectal cancer. However, conventional staging is unable to predict disease outcome accurately for each individual patient. This results in considerable prognostic heterogeneity within a given tumor stage and is of particular relevance for a subgroup of patients with stage II disease that would benefit from adjuvant therapy. The recent advances in functional genomics are beginning to have a significant impact on clinical oncology, and there is widespread interest in using molecular techniques for clinical applications. These have focused on two approaches: the use of polymerase chain reaction (PCR)-based methods for the detection of occult disease in lymph nodes, bone marrow and blood and the use of microarrays for the expression profiling of primary tumors. The aim is to develop molecular classifiers that will allow the prediction of disease outcome, thus matching patients with individualized treatment. Despite the obvious attractions of these approaches, there have been significant technical, biological and analytical problems in their translation into clinically relevant practice. This is particularly true for colorectal cancer, the second most common cancer in the western world. Nevertheless, progress is being made and the improved awareness and appreciation of those difficulties is beginning to generate results that should prove useful for clinical oncology.

Real-time reverse transcription PCR and the detection of occult disease in colorectal cancer

Molecular diagnostics offers the promise of accurately matching patient with treatment, and a resultant significant effect on improved disease outcome. More specifically, the real-time reverse transcription polymerase chain reaction (qRT-PCR), with its combination of conceptual simplicity and technical utility, has the potential to become a valuable analytical tool for the detection of mRNA targets from tissue biopsies and body fluids. Its potential is particularly promising in cancer patients, both as a prognostic assay and for monitoring response to therapy. Colorectal cancer provides an instructive paradigm for this potential as well as the problems associated with its use as a clinical assay. Currently, histopathological staging, which provides a static description of the anatomical extent of tumour spread within a surgical specimen, defines patient prognosis. The detection of lymph node (LN) metastasis constitutes the most important prognostic factor in colorectal cancer and as the primary indicator of systemic disease spread, LN status determines the choice of postoperative adjuvant chemotherapy. However, its limitations are emphasised by the considerable prognostic heterogeneity of patients within a given tumour stage: not all patients with LN-negative cancers are cured and not all patients with LN-positive tumours die from their disease. This has resulted in a search for more accurate staging protocols and has seen the introduction of the concept of "molecular staging", the incorporation of molecular parameters into clinical tumour staging. Quantification of disease-associated mRNA is one such parameter that utilises the qRT-PCR assay's potential for generating quantitative results. These are not only more informative than qualitative data, but contribute to assay standardisation and quality management. This review provides an assessment of the practical value to the clinician of RT-PCR-based molecular diagnostics. It points out reasons for the many contradictory results encountered in the literature and concludes that there is an urgent need for standardisation at every level, starting with pre-assay sample acquisition and template preparation, assay protocols and post-assay analysis.

Critical evaluation of real-time reverse transcriptase-polymerase chain reaction for the quantitative detection of cytokeratin 20 mRNA in colorectal cancer patients

We evaluated the usefulness of cytokeratin 20 (CK20) mRNA expression in the quantitative detection of circulating tumor cells in the blood of patients with colorectal cancer (CRC). Blood samples from healthy volunteers (HVs; n = 37), patients with localized (n = 42) and metastatic colorectal cancer (n = 40), and patients with chronic inflammatory bowel disease (CID; n = 15) were examined. After immunomagnetic enrichment using microbeads against human epithelial antigen, total RNA was extracted, reverse transcribed, and analyzed by real-time reverse transcriptase-polymerase chain reaction using the LightCycler instrument. CK20 expression in peripheral blood was found in 46 of 82 (56%) patients with CRC, 8 of 37 (22%) HVs, and 9 of 15 (60%) patients with CID. Levels of CK20 mRNA were significantly higher in blood samples from CRC patients (median 681) than in blood samples from HVs (median 0) (P = 0.001), whereas no difference could be detected between patients with CRC and CID. Although the present technique could not distinguish CRC from CID, the method warrants further efforts to improve sample preparation and tumor cell enrichment, which may render real-time CK20 reverse transcriptase-polymerase chain reaction a feasible technique in identifying circulating tumor cells in peripheral blood of cancer patients.

Detection of CK20 in peripheral blood of rectal cancer patients with fluorescence quantitative polymerase chain reaction and its significance

AIM: To analyze the relations of CK20 expression in the peripheral blood with the Dukes stages and histological types, and to discuss the value of fluorescence quantitative polymerase chain reaction (FQ-PCR) for predicting the metastases and prognosis of rectal cancer.

METHODS: The peripheral blood samples were collected from 47 patients with rectal cancer, 10 patients with benign intestinal diseases, and 10 healthy volunteers. Then FQ-PCR was performed to detect the expression of CK20 mRNA in the peripheral blood.

RESULTS: There was no positive expression of CK20 mRNA in the patients with benign intestinal diseases and the healthy volunteers, which was significantly different from that in the patients with rectal cancer (72.34%, 34/47) (χ² = 37.434, P < 0.01). The level of CK20 expression in the peripheral blood of the 47 patients with rectal cancer was positively correlated with the Dukes stages of rectal cancer (r = 0.680, P < 0.01).

CONCLUSION: The level of CK20 expression is positively related with tumor stages in the peripheral blood of the rectal cancer patients. CK20 detection by FQ-PCR is more sensitive than routine histological methods in predicting the metastases and prognosis of rectal cancer.

Detection of carcinoembryonic antigen messenger RNA-expressing cells in portal and peripheral blood during surgery does not influence relapse in colorectal cancer

BACKGROUND

No consensus has been reached on whether cancer cells detected in blood during colorectal cancer (CRC) surgery may serve as a prognostic indicator.

METHODS

One hundred patients with CRC who underwent curative surgery were the subjects. Portal and peripheral blood were collected immediately after celiotomy and examined for carcinoembryonic antigen (CEA) messenger RNA (mRNA) by using competitive semi-nested reverse transcriptase-polymerase chain reaction. The median follow-up period was 59 months (range, 49-74 months).

RESULTS

Until now, recurrence has been confirmed in 13 patients (13%). The 4-year recurrence rate was 6.7% (3 of 45) in patients with CEA mRNA-positive portal blood and 20.8% (10 of 48) in patients with CEA mRNA-negative portal blood (P = .09); it was 5.6% (2 of 36) and 19.3% (11 of 57) in patients with CEA mRNA-positive peripheral blood and CEA mRNA-negative blood, respectively (P = .12). There was no difference in disease-free survival between the CEA mRNA-positive and -negative groups. The multivariate analysis showed that the presence of tumor cells in portal or peripheral blood was a factor that reduced recurrence. The relative risks were .17 (P = .01) for the portal vein and .24 (P = .07) for the peripheral vein.

CONCLUSIONS

The detection of cancer cells in blood taken during surgery is not considered to be a poor-prognostic factor in CRC.

Detection of cytokeratin 20 mRNA in the peripheral blood of patients with colorectal cancer by immunomagnetic bead enrichment and real-time reverse transcriptase-polymeras chain reaction

BACKGROUND

Detection of circulating cancer cells is a useful indicator for the risk of recurrence of advanced carcinoma. The aim of the present study was to evaluate the potential value of a novel approach to detect the circulating cancer cells in patients with colorectal cancer. This method is based on a combination of isolation of epithelial cell by a combination of negative and positive immunomagnetic beads with detection of cytokeratin 20 (CK20) mRNA by reverse transcriptase-polymeras chain reaction (RT-PCR).

METHODS

Peripheral blood samples were collected from 40 patients with colorectal carcinoma on the day before operation or chemical therapy. Mononuclear cells (MNC) were isolated by centrifugation through a Ficoll gradient. Each MNC sample was equally divided into three parts and then CD45 immunomagnetic beads and/or Ber-EP4 immunomagnetic beads were used to enrich colon cancer cells. Finally, the CK20 mRNA was detected by real-time quantitative RT-PCR. As a control, LS174T colon cancer cells were serially diluted with blood from healthy individuals.

RESULTS

When CD45 and Ber-EP4 immunomagnetic beads were used successively, a significant correlation between CK20 mRNA levels and the initial cell concentrations was found in the control recovery experiment. The sensitivity of the assay was one cancer cell in 1 mL healthy blood. In the patient group, CK20 mRNA was detected in 80.0%, 82.5% and 72.5% of patients when CD45, Ber-EP4, and CD45/Ber-EP4 immunomagnetic beads were used, respectively. The positive detection rates of patients with colorectal carcinoma at Dukes A, B, C, and D stage were 0.0% (0/2), 33.3% (3/9), 86.7% (13/15), and 92.9% (13/14), respectively. The CK20 mRNA positive detection rate in peripheral blood was significantly correlated with tumor diameter (P < 0.01, chi(2)), lymphatic metastasis (P < 0.05) and hepatic metastasis (P < 0.05), but not with the differentiation of tumor cells.

CONCLUSION

The combined use of negative and positive immunomagnetic beads followed by amplification of CK20 mRNA by means of RT-PCR is a non-invasive, sensitive, and specific assay for the detection of circulating colonic cancer cells.

Disseminated tumor cells in the blood of patients with gastric cancer are an independent predictive marker of poor prognosis

OBJECTIVE

Gastric cancer carries a poor prognosis even after curative resection (R0). Tumor progression in gastric cancer patients has been attributed to the persistence of disseminated tumor cells (DTC) in various body compartments as a sign of minimal residual disease, although the prognostic relevance of DTC is still unclear. In this study the prognostic relevance of DTC in the blood of gastric cancer patients was investigated.

MATERIALS AND METHODS

Venous blood samples of 70 cancer patients were taken intraoperatively before surgical manipulation and examined by reverse transcription-polymerase chain reaction (RT-PCR) for expression of cytokeratin 20 (CK20) as a marker for DTC. Tumor-related survival was analyzed using univariate and multivariate models assessing occurrence of DTC, residual tumor classification, and tumor stage. Median follow-up was 20 months (range 1-57 months).

RESULTS

Twenty-eight of the 70 patients (40%) were CK20 positive. The prevalence of DTC in patients following R0 resection (15/41, 37%) was similar to that in patients with residual tumor (13/29, 45%, NS). Furthermore, expression of CK20 was independent of TNM stage. Univariate analysis of R0-resected patients revealed CK20 to be a marker for significantly shorter tumor-related survival (p = 0.0363). In a multivariate analysis, CK20 was an independent prognostic marker. Detection of CK20 had greatest impact for early tumor stages (T1 and T2, N0; p < 0.0032).

CONCLUSIONS

Detection of DTC in venous blood of gastric cancer patients is an independent predictive marker of poor prognosis and thus could help to define patients for adjuvant therapy with this tumor entity.

Preoperative evaluation and postoperative follow-up for patients with rectal cancer

Rectal cancer has a wide variety of presentations. In most cases, it is the surgeon who is faced with the challenge of determining the extent of disease and advising the patient how to proceed with treatment. Utilizing diagnostic tests of the highest accuracy and relevance will help in the selection of the best initial therapy, which is critical for achieving the highest cure rate while also avoiding over-treatment and unnecessary morbidity. Following curative treatment, surveillance testing for detection of recurrence is traditionally done, but the efficacy of this practice has been questioned. Surveillance will detect a number of asymptomatic recurrences that are treatable by potentially curative salvage surgery, but to what extent early detection improves salvage therapy is not well established. In this brief review, the goals, methods, and expected benefits of rectal cancer staging and surveillance are assessed.

Combined use of positive and negative immunomagnetic isolation followed by real-time RT-PCR for detection of the circulating tumor cells in patients with colorectal cancers

To establish a novel molecular diagnostic method of detecting circulating tumor cells (CTCs) LS174T colon cancer cells were serially diluted with normal blood. Additional peripheral blood samples were collected from 25 patients with colorectal carcinoma. Mononuclear cells (MNCs) were collected, equally divided into four parts, and then cancer cells were enriched by four methods: method A, nonimmunobead method; method B, negative immunobead method: CD45 immunomagnetic beads were used to deplete the leukocytes; method C, positive immunobead method: Ber-EP4 immunomagnetic beads were used to enrich cancer cells; method D, negative-and-positive immunobead method: CD45 immunomagnetic beads were first used to deplete the leukocytes from MNC and then Ber-EP4 immunomagnetic beads were used to enrich cancer cells. Finally, real-time quantitative RT-PCR was used to monitor mRNA expression of beta2-mircoglobulin (beta2M) and carcinoembryonic antigen (CEA). The relative CEA mRNA values were corrected with reference to beta2M mRNA, to CEA mRNA/beta2M mRNA ratios according to a CEA mRNA external standards prepared with tenfold serial dilutions (1-10(4) IS174T cells) of cDNA and beta2M mRNA external standards prepared with tenfold serial dilutions (10(2)-10(7) leukocytes) of cDNA. In recovery experiments a significant correlation between the number of cancer cells and CEA mRNA expression was found when CD45 or Ber-EP4 immunomagnetic beads were used alone. A highly significant correlation was found when CD45 and Ber-EP4 immunomagnetic beads were used successively. The sensitivity of method D was one cancer cell per milliliter of blood. Circulating cancer cells were detected in 19 of 25 patients with colorectal cancers. The relative CEA mRNA value obtained by method D was the smallest. The positive detection rate of circulating cancer cells in patients at Dukes' B, C, and D stages were 25.0% (1/4), 83.3% (10/12), and 88.9% (8/9). Combinative use of immunomagnetic isolation followed by real-time RT-PCR is a useful technique to detect circulating tumor cells in patients with colorectal carcinomas. Applying negative and positive immunomagnetic beads successively yields the highest correlation with amount of tumor cells.

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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.

Detection of disseminated tumor cells in nude mice with human gastric cancer

Disseminated tumor cells (DTC) are a potential contributor to relapse of cancer. In the present study we developed a model for induction of disseminated tumor cells in nude mice, which can aid in the search for therapeutic approaches as well as improve our understanding of metastasizing gastric cancer. To detect DTC in blood and bone marrow we established a modified animal model of orthotopic transplantation. Two groups of nude mice were used for xenotransplantation of gastric cancer specimens. In group I tumor specimens originating from a gastric adenocarcinoma cell line were transplanted onto the stomach; in group II they were transplanted subcutaneously into both axillaries. Tumor growth, metastases and presence of DTC were compared in both groups. For detection of DTC a nested reverse transcriptase polymerase chain reaction (RT-PCR) for human cytokeratin (CK)-20 was performed on blood and bone marrow of all mice. Tumor growth occurred in both groups (9/10 animals in group I, 10/10 in group II) within 14 weeks. Only animals in group I developed local invasive tumor growth, stenosis of the stomach and distant metastases. Tumors in animals of group II grew with local displacement only and developed no metastases. There were no signals of CK-20 detected in the blood in both groups. In group I, 5 of 9 animals had positive signals of human CK-20 in their bone marrow as a sign of DTC. In group II no DTC were detected in bone marrow. We conclude that orthotopic transplantation is a prerequisite for the development of DTC and metastasizing tumor growth in this modified gastric cancer model.

Colon cancer: prevalence, screening, gene expression and mutation, and risk factors and assessment

Colon cancer detection at an early stage and identifying susceptible individuals can result in reduced mortality from this prevalent cancer. Genetic events leading to the development of this cancer involve a multistage progression of adenoma polyps to invasive metastatic carcinomas. Currently, there is no satisfactory screening method that is highly specific, sensitive, or reliable. Dietary patterns associated with the greatest increase in colon cancer risk are the ones that typify a diet rich in fat and calories, and low in vegetable, fruits, and fibers. Genetic susceptibility to environmental carcinogenesis must be factored into the risk assessment for this cancer. Many genes have been shown to be associated with increased expression and mutations in colorectal cancer patients. These genes have been reviewed; it is hoped that by carefully selecting a number of them, a molecular approach that is suitable for arriving at a tumorigenic expression index is developed, which will reliably detect this cancer at an early stage (i.e., before it metastasizes), especially in exfoliated samples (e.g., stool and blood), so that appropriate intervention strategies can be implemented. Illustrated herein is the utility of employing real-time reverse transcriptase polymerase chain reaction (RT-PCR) to quantitatively measure gene expression, and develop an index that is specific for this cancer, which if perfected may result in a reliable and sensitive screening technique for colorectal cancer detection.