Detection and evaluation of epithelial cells in the blood of colon cancer patients using RT-PCR

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.

Recent advances in microfluidic methods in cancer liquid biopsy

Early cancer detection, its monitoring, and therapeutical prediction are highly valuable, though extremely challenging targets in oncology. Significant progress has been made recently, resulting in a group of devices and techniques that are now capable of successfully detecting, interpreting, and monitoring cancer biomarkers in body fluids. Precise information about malignancies can be obtained from liquid biopsies by isolating and analyzing circulating tumor cells (CTCs) or nucleic acids, tumor-derived vesicles or proteins, and metabolites. The current work provides a general overview of the latest on-chip technological developments for cancer liquid biopsy. Current challenges for their translation and their application in various clinical settings are discussed. Microfluidic solutions for each set of biomarkers are compared, and a global overview of the major trends and ongoing research challenges is given. A detailed analysis of the microfluidic isolation of CTCs with recent efforts that aimed at increasing purity and capture efficiency is provided as well. Although CTCs have been the focus of a vast microfluidic research effort as the key element for obtaining relevant information, important clinical insights can also be achieved from alternative biomarkers, such as classical protein biomarkers, exosomes, or circulating-free nucleic acids. Finally, while most work has been devoted to the analysis of blood-based biomarkers, we highlight the less explored potential of urine as an ideal source of molecular cancer biomarkers for point-of-care lab-on-chip devices.

Cytokeratin 17 mRNA as a prognostic marker of oral squamous cell carcinoma

Despite diagnostic and therapeutic advances, the 5-year survival rate of oral squamous cell carcinoma (OSCC) remains between 70–80% due to recurrences and secondary metastases to cervical lymph nodes. It is difficult to find these recurrences and metastases postoperatively, thus, careful follow-up is recommended. Cytokeratins (CKs) are intermediate filaments of the cytoskeleton and candidate prognostic biomarkers for OSCC, as they are overexpressed in OSCC compared with normal mucosa. The aim of the present study was to determine the relative levels of occurrence of 3 CK mRNA (CK17, CK19, CK20) transcripts in peripheral blood mononuclear cells (PBMC) using reverse transcription-quantitative polymerase chain reaction. The study comprised pre- and post-operative PBMC samples from 19 OSCC patients. In the good-prognosis group, 10 of 13 patients demonstrated reduced CK17 mRNA expression post-operatively, compared with pre-operative samples, conversely, only 3 of 6 patients in the poor-prognosis group had reduced post-operative CK17 mRNA expression. This difference was statistically significant (P<0.01). The disease-free survival rate of the group with reduced post-operative CK17 mRNA expression was significantly increased compared with the elevated CK17 mRNA group (P<0.01); however, the overall survival rates of the two groups were not significantly different. Neither CK19 mRNA nor CK20 mRNA were significantly expressed in the PBMC of OSCC patients. Overall, CK17 mRNA expression may be a useful prognostic biomarker for OSCC.

Circulating Tumor Cells as Cancer Biomarkers in the Clinic

It is believed that the development of metastatic cancer requires the presence of circulating tumor cells (CTCs) , which are found in a patient's circulation as rare abnormal cells comingled with billions of the normal red and white blood cells. The systems developed for detection of CTCs have brought progress to cancer treatment. The molecular characterization of CTCs can aid in the development of new drugs, and their presence during treatment can help clinicians determine the prognosis of the patient. Studies have been carried out in patients early in the disease course, with only primary tumors, and the role of CTCs in prognosis seems to be as important as it is in patients with metastatic disease. The published studies on CTCs have focused on their prognostic significance, their utility in real-time monitoring of therapies, the identification of therapeutic and resistance targets, and understanding the process of metastasis . The analysis of CTCs during the early stages, as a "liquid biopsy," helps to monitor patients at different points in the disease course, including minimal residual disease, providing valuable information about the very early assessment of treatment effectiveness. Finally, CTCs can be used to screen patients with family histories of cancer or with diseases that can lead to the development of cancer. With standard protocols, this easily obtained and practical tool can be used to prevent the growth and spread of cancer. In this chapter, we review some important aspects of CTCs , surveying the disease aspects where these cells have been investigated.

CK20 mRNA Expression in Serum as a Biomarker for Colorectal Cancer Diagnosis: A Meta-analysis

The aim of this study was to evaluate the diagnostic value of serumCK20 mRNA as a biomarker for colorectal cancer diagnosis by meta-analysis. Clinical studies related to serum CK20 mRNA expression for colorectal cancer diagnosis were searched in the databases of Pubmed, Cochrane Library, Embase, ISI Web of Knowledge, CNKI and Wanfang. The number of true positive (tp), false positive (fp), false negative (fn) and true negative (tn) of the original included publications were extracted by two reviewers independently. The diagnostic sensitivity, specificity, positive likely hood ratio (+LR), negative likelyhood ratio (-LR), diagnostic odds ratio (DOR) and area under the symmetric ROC curve (AUC) were pooled by random or fixed effect method according to the statistical heterogeneity among the studies. After screening the databases, nineteen publications met the inclusion criteria and were finally included in this meta-analysis. The diagnostic sensitivity and specificity were pooled by random effect model(I2>50%). The pooled diagnostic sensitivity and specificity of CK20 mRNA in serum as biomarker for colorectal cancer were 0.49 (95% CI:0.46 to 0.51) and 0.94 (95%CI:0.92-0.96) respectively. The pooled +LR and -LR were 10.90 (95%CI:5.78 to 20.55) and 0.51 (95%CI:0.45 to 0.57) respectively by random-effect method. The pooled DOR was 22.31 with the 95% CI of 11.65 to 42.71. The pooled area under the ROC curve (AUC) was 0.72for CK20 mRNA in serum as a biomarker for colorectal cancer diagnosis. Conclusion Serum CK20 mRNA expression was significantly elevated in colorectal cancer patients which could be a promising serum biomarker for colorectal cancer diagnosis with high specificity.

Change in number and size of circulating tumor cells with high telomerase activity during treatment of patients with gastric cancer

Detection of circulating tumor cells (CTCs) in peripheral blood is useful for estimating the prognosis of patients with cancer. We previously reported the detection of CTCs by OBP-401, a telomerase-specific, replication-selective, oncolytic adenoviral agent carrying the green fluorescent protein (GFP) gene. We demonstrated that the number of large (L)-GFP+ cells (≥7.735 µm in diameter) in peripheral blood samples correlated significantly with the prognosis of treatment-naïve gastric cancer patients, whereas the number of small (S)-GFP+ cells (<7.735 µm in diameter) did not. In the present study, we studied the change in the number of GFP+ cells during treatment, and analyzed the association between the number of GFP+ cells in blood samples and the outcome of patients. Peripheral blood samples were obtained from 37 gastric patients prior and subsequent to surgery (three samples per time point). Upon infection of blood cells with OBP-401, GFP+ cells of different sizes were counted and measured. The association between the number of GFP+ cells and surgical outcome was determined by statistical analysis. The median follow-up period after surgery was 39 months. Although the difference was not significant, patients with ≥6 L-GFP+ cells in preoperative blood samples had a lower relapse-free survival rate than patients with 0-5 L-GFP+ cells. There was no significant correlation between the number of L-GFP+ cells in postoperative blood samples and the prognosis of patients receiving adjuvant therapy. Although the difference was not significant, the number of S-GFP+ cells in samples from patients who had received postoperative chemotherapy was higher than in those who had not. The number of L-GFP+ cells was not significantly correlated with the relapse-free survival rate in gastric cancer patients who underwent surgery. The number of S-GFP+ cells was relatively high in samples from patients who had received postoperative chemotherapy.

Diversity of assessing circulating tumor cells (CTCs) emphasizes need for standardization: a CTC Guide to design and report trials

Hematogenous spreading of tumor cells from primary tumors is a crucial step in the cascade to metastasis, the latter being the most limiting factor for patients' survival prognosis. Therefore, circulating tumor cells (CTCs) have become a field of intensive research. However, the process of isolation and identification of CTCs lacks standardization. This article presents an overview of 71 CTC studies reported in PUBMED since 2000 and focusing on colorectal cancer. These studies are evaluated regarding standardization of CTC isolation and identification, marker proteins used, study population and blood sample quality management, clinical performance, and quality measures. Overall, standardization of CTC assessment seems insufficient. Thus, comparability of CTC studies is hampered and results should be interpreted carefully. We here propose a standardized CTC guideline (CTC Guide) to prospectively design and report studies/trials in a harmonized form. Despite the current interstudy heterogeneity, the data indicate that CTC detection is of clinical relevance and CTCs should be considered as a surrogate prognostic marker. Many studies indicate the high potential for CTCs as prognostic markers, e.g., in colorectal cancer treatment. However, standardized, large-scale multicenter validation studies are still needed to pave the way for clinical implementation of CTC detection that could ameliorate individualized medicine regimes.

Cytokeratin-20 and Survivin-Expressing Circulating Tumor Cells Predict Survival in Metastatic Colorectal Cancer Patients by a Combined Immunomagnetic qRT-PCR Approach

Circulating tumor cells (CTC) express epithelial and stem cell-like genes, though current approved detection methods mainly use epithelial markers. We optimized a CTC isolation method that could capture their molecular heterogeneity and predict overall survival (OS) in metastatic colorectal cancer (mCRC) patients receiving various chemotherapy regimens. We combined immunomagnetic enrichment of CD45-negative, EpCAM-positive circulating cancer cells with qRT-PCR amplification of CK20 and survivin expression in 88 mCRC patients and 20 healthy controls. We then evaluated the prognostic value of baseline CTC CK20 and survivin expression in mCRC patients. The presence of elevated CTC CK20 or survivin expression distinguished mCRC patients from controls with sufficient sensitivity (79.6%) and specificity (85%). In univariate analysis, patients with high CTC-CK20 expression (9 vs. 33.2+ months, log-rank P < 0.001) or high CTC-survivin expression (10 vs. 33.2+ months, log-rank P = 0.032) had a significantly worse median OS than those with low expression of either marker. In multivariable analysis, the high CTC-CK20 group had significantly shortened OS (HR, 3.11; adjusted P = 0.01), and there was a trend toward inferior OS in the high CTC-survivin group (HR, 1.76; adjusted P = 0.099). Patients with either high CTC CK20 or survivin expression had inferior OS compared with those with low expression of both markers (HR, 4.39; 95% confidence interval, 1.56-12.35; adjusted P = 0.005). Colorectal cancer CTCs can be reliably isolated using epithelial and stem cell markers. CTC CK20 and survivin expression may effectively predict OS in mCRC patients receiving chemotherapy.

Hydroxyethyl starch 200/0.5 decreases circulating tumor cells of colorectal cancer patients and reduces metastatic potential of colon cancer cell line through inhibiting platelets activation

Platelets play an important role in metastasis of circulating tumor cells (CTCs). It has been demonstrated that hydroxyethyl starch (HES) inhibits platelets function. However, the effect of HES on CTCs in patients with colorectal cancer remains unclear. We compared the effects of HES 200/0.5 and HES 130/0.4 on CTCs and platelets activation of colorectal patients in this study. Additionally, the effects of HES 200/0.5 or HES 130/0.4 on metastasis ability of colon cancer cell line that stimulated by activated platelets have been explored. In vivo, 90 patients undergoing colorectal cancer radical surgery received randomly 15 mL/kg of HES 200/0.5 (n = 45) or HES 130/0.4 (n = 45) infusion before surgery. Platelet glycoprotein IIb/IIIa (GPIIb/IIIa), CD62P and platelets aggregation rate (PAR) were evaluated pre-, intra- and postoperatively. Cytokeratin-20 (CK-20) mRNA was detected by reverse transcriptase polymerase chain reaction before and after surgery. In vitro, colon cancer SW480 cells were incubated with activated platelets in the presence or absence HES 200/0.5 or HES 130/0.4. The metastasis ability of SW480 cells was assessed by Transwell assay. The results showed that CK-20 mRNA positive rate in HES 200/0.5 group after surgery was decreased significantly as compared to group HES 130/0.4 (χ (2) = 6.164, P = 0.013). Simultaneously, a more pronounced inhibition of platelets activation was observed in group HES 200/0.5. A positive correlation between platelets activation marker and CK-20 mRNA positive rate was found. In vitro, HES 200/0.5, but not HES 130/0.4, decreased the invasion and migration ability of SW480 cells that induced by activated platelets. Besides, the expression of GPIIb/IIIa, CD62P and PAR was inhibited more strongly in group HES 200/0.5 than those in group HES 130/0.4. In summary, we found that HES 200/0.5 significantly decreased CTCs of patients undergoing colorectal cancer radical surgery as compared to HES 130/0.4, which might be associated with inhibiting platelets activation of HES 200/0.5. Furthermore, HES 200/0.5, but not HES 130/0.4, reduced the metastatic potential of colon cell line stimulated by activated platelets through depressing platelets activation. Modulation of platelets activity may be a novel strategy to minimize the risk of metastasis during surgery.

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.

Prognostic impact of the number of viable circulating cells with high telomerase activity in gastric cancer patients: a prospective study

The identification of circulating tumor cells (CTCs) in peripheral blood is a useful approach to estimate prognosis, monitor disease progression and measure treatment effects in several types of malignancies. We have previously used OBP-401, a telomerase-specific, replication-selective, oncolytic adenoviral agent carrying the green fluorescent protein (GFP) gene. GFP-positive cells (GFP+ cells) were counted under a fluorescence microscope. Our results showed that the number of at least 7.735 µm in diameter GFP+ cells (L-GFP+ cells) in the peripheral blood was a significant marker of prognosis in gastric cancer patients. However, tumor cells undergoing epithelial-mesenchymal transition (EMT) have been reported to be smaller in size than cells without EMT features; thus, CTCs undergoing EMT may escape detection with this technique. Therefore, in this study, we analyzed the relationship between patient outcome and the number of GFP+ cells of any size. We obtained peripheral blood samples from 65 patients with gastric cancer. After infection of OBP-401, GFP+ cells were counted and measured. The relationship between the number of GFP+ cells and surgical outcome was analyzed. The median follow-up period of the surviving patients was 36 months. A significant difference in overall survival was found between patients with 0-5 and patients with ≥6 L-GFP+ cells. No clear relationship was established between the number of small-sized GFP+ cells and patient prognosis. The number of L-GFP+ cells was significantly related to overall survival in patients with gastric cancer. The detection of L-GFP+ cells using OBP-401 may be a useful prognostic marker in gastric cancer.

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.

Prognostic significance of isolated tumor cells in patients with colorectal cancer in recent 10-year studies

Circulating tumor cells (CTCs) that detach from the primary tumor and move into the circulation are detected in patients with metastatic cancer. The discovery of such cancer cells has been used as a predictor of recurrence and prognosis, although a consensus regarding such applications has not been reached. Peritoneal cytology may be used for identifying high risk of recurrence or mortality, whereas the intraoperative presence of tumor cells in drainage veins, bone marrow, or the liver is not always useful for evaluating the prognosis. The reported positive rate for tumor cells in the peripheral blood of patients with colorectal cancer, including metastasis, has varied from 10 to 80%; however, numerous studies have demonstrated significant differences in the recurrence and mortality rates between patients with and without isolated tumor cells (ITCs) in the peripheral blood. However, the clinical significance of CTCs as an absolute prognostic factor has not been elucidated, since the measurement methodologies and/or the number of cases differed between the studies. Future prospective studies including larger patient populations may elucidate the utility of routine detection of ITCs in daily practice.

Prognostic impact of detecting viable circulating tumour cells in gastric cancer patients using a telomerase-specific viral agent: a prospective study

Background

The identification of circulating tumour cells (CTCs) in peripheral blood is a useful approach to estimate prognosis, monitor disease progression, and measure treatment effects in various malignancies. However, clinical relevance of CTCs is controversial. We attempted to detect viable CTCs in the peripheral blood of gastric cancer patients using a telomerase-specific viral agent.

Methods

We took a 7.5-ml blood sample from 65 treatment-negative gastric cancer patients before surgery and 10 healthy volunteers. We detected viable CTCs in the blood samples after incubating them with a telomerase-specific, replication-selective, oncolytic adenoviral agent carrying the green fluorescent protein (GFP) gene (OBP-401). GFP-positive CTCs were defined as having a diameter of at least 7.735 μm; this threshold was determined by receiver operating characteristic curve analysis. GFP-positive cells were counted under a fluorescence microscope.

Results

There was a significant difference in overall survival among the patients with 0–4 and those with ≥5 GFP-positive CTCs in the stage I–IV disease group and stage II–IV advanced disease group. The number of GFP-positive CTCs was not related to cancer stage. Among the pathological findings, the number of GFP-positive CTCs was only significantly related to venous invasion, although there were trends towards more GFP-positive CTCs with disease progression (tumour depth, lymph node metastasis, distant metastasis, lymphatic invasion, and histological type).

Conclusions

There was a significant relationship between the number of GFP-positive CTCs and overall survival in the patients with gastric cancer. The detection of CTCs using OBP-401 may be useful for prognostic evaluation.

Trial registration

University Hospital Medical Information Network in Japan, UMIN000002018.

Clinical significance of CDX2-positive circulating tumour cells in colorectal cancer patients

Background:

Our recent work has shown the feasibility of using a refined immunomagnetic enrichment (IE) assay to detect cytokeratin 20-positive circulating tumour cells (CK20 pCTCs) in colorectal cancer (CRC) patients. We attempted to improve the sensitivity for CRC by detecting another intestinal-type differentiation marker, CDX2 pCTCs, using the same methodology.

Methods:

CDX2 pCTCs were detected in patients with CRC, colorectal adenoma (CAD), benign colorectal diseases (BCD), other common cancers (OCC) and normal subjects (NS). Statistical analysis was used to correlate CDX2 pCTCs to the clinicohistopathological factors, recurrence, metastasis and survival after follow-up for 42 months in CRC patients.

Results:

CDX2 pCTCs were detected in 81% CRC patients (73 out of 90, median number=21.5 CTCs), 7.5% CAD patients (3 out of 40), 0% patients with BCD (0 out of 90), 2.5% patients with OCC (2 out of 80) and 0% NS (0 out of 40). Furthermore, statistical analysis showed that CDX2 pCTC numbers were associated with tumour- node-metastasis stage and lymph node status. Using the median CDX2 pCTC numbers as the cutoff points, stratified groups of CRC patients had significant differences in their recurrence and survival.

Conclusions:

This study showed that the refined IE assay can detect CDX2 pCTCs with high sensitivity and that CDX2 pCTCs can generate clinically important information for CRC patients.

Predictive markers of colorectal cancer liver metastases

Liver metastases are the most common site of distant failure after curative resection of colorectal cancer and a source of significant cancer-related morbidity and mortality. Currently, imaging and conventional histopathologic features, such as T-stage and N-stage, are used by clinicians to inform prognosis and guide adjuvant treatment to reduce the risk of developing distant metastases. However, these tools only have a moderate ability to predict the development of liver metastases. Novel methods, including the detection of circulating tumor cells and carcinoembryonic antigens in serum, have been developed, and their prognostic and predictive characteristics have been assessed. In addition, several molecular and genetic markers in the primary tumor have been studied. Unfortunately, these studies are often small and their results have been mixed, yielding no consistent sets of externally validated predictors of colorectal liver metastases. For widespread clinical relevance, future tests need to be independently carried out on large independent patient samples.

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.

Meta-analysis shows that detection of circulating tumor cells indicates poor prognosis in patients with colorectal cancer

BACKGROUND & AIMS

The prognostic significance of circulating (CTCs) and disseminated tumor cells in patients with colorectal cancer (CRC) is controversial. We performed a meta-analysis of available studies to assess whether the detection of tumor cells in the blood and bone marrow (BM) of patients diagnosed with primary CRC can be used as a prognostic factor.

METHODS

We searched the Medline, Biosis, Science Citation Index, and Embase databases and reference lists of relevant articles (including review articles) for studies that assessed the prognostic relevance of tumor cell detection in the peripheral blood (PB), mesenteric/portal blood (MPB), or BM of patients with CRC. Meta-analyses were performed using a random effects model, with hazard ratio (HR) and 95% confidence intervals (95% CIs) as effect measures.

RESULTS

A total of 36 studies, including 3094 patients, were eligible for final analyses. Pooled analyses that combined all sampling sites (PB, MPB, and BM) associated the detection of tumor cells with poor recurrence-free survival (RFS) (HR = 3.24 [95% CI: 2.06-5.10], n = 26, I(2) = 77%) and overall survival (OS) (2.28 [1.55-3.38], n = 21, I(2) = 66%). Stratification by sampling site showed that detection of tumor cells in the PB compartment was a statistically significant prognostic factor (RFS: 3.06 [1.74-5.38], n = 19, I(2) = 78%; OS: 2.70 [1.74-4.20], n = 16, I(2) = 59%) but not in the MPB (RFS: 4.12 [1.01-16.83], n = 8, I(2) = 75%; OS: 4.80 [0.81-28.32], n = 5, I(2) = 82%) or in the BM (RFS: 2.17 [0.94-5.03], n = 4, I(2) = 78%; OS: 1.50 [0.52-4.32], n = 3, I(2) = 84%).

CONCLUSION

Detection of CTCs in the PB indicates poor prognosis in patients with primary CRC.

Prognostic significance of circulating tumour cells following surgical resection of colorectal cancers: a systematic review

Background:

The role of adjuvant chemotherapy after resection of colorectal cancers (CRCs) is well understood for patients with stage-I or stage-III disease. Its efficacy for those with stage-II disease remains much less clear. Many investigators have sought to identify prognostic markers that might clarify which patients have the highest risk of recurrence and would, therefore, be most likely to benefit from chemotherapy. This systematic review examines evidence for the use of peripherally sampled, circulating tumour cells (CTCs) as such a prognostic marker.

Methods:

A comprehensive literature search was used to identify studies reporting on the significance of CTCs in the postoperative blood of CRC patients.

Results:

Fourteen studies satisfied the inclusion criteria. Six of the nine studies that took blood samples 24 h or more postoperatively found detection of postoperative CTCs to be an independent predictor of cancer recurrence.

Conclusion:

The presence of CTCs in peripheral blood at least 24 h after resection of CRCs is an independent prognostic marker of recurrence. Further studies are needed to clarify the optimal time point for blood sampling and determine the benefit of chemotherapy in CTC-positive patients with stage-II disease.

Circulating tumor cells: evolving evidence and future challenges

Circulating tumor cells (CTCs) are rare malignant cells found in the peripheral blood that originate from the primary tumor or metastatic sites. New techniques have been developed to isolate and characterize these cells. CTC enumeration has been incorporated into different fields of oncology as a prognostic marker, a tool to monitor therapy response, and a method to understand basic tumor characteristics. This review covers the different techniques available for isolation of CTCs, the clinical utility of CTCs in breast, prostate, and colon cancer, and future directions in this field.

Clinical significance of cytokeratin 20-positive circulating tumor cells detected by a refined immunomagnetic enrichment assay in colorectal cancer patients

PURPOSE

Current immunomagnetic enrichment method can only detect general epithelial antigens of circulating tumor cells (CTC). Further characterization of the CTCs to provide specific information on the tumor type is not possible. We attempted to overcome this drawback by developing the methodology for using a gastrointestinal-specific anti-cytokeratin (CK) 20 antibody to detect CTCs in colorectal cancer patients' blood.

EXPERIMENTAL DESIGN

The protocol was validated using a colorectal cancer SW480 cell line. The clinical significance of findings in colorectal cancer was investigated by detecting CK20-positive CTCs (pCTC) in patients with colorectal cancer, other common cancers, colorectal adenoma, benign colorectal diseases, and normal subjects. Moreover, the malignant nature of CK20 pCTCs was examined by comparing chromosome 17 aberration patterns with those from the corresponding primary tumors.

RESULTS

The assay successfully showed CK20-positive SW480 cells. When applied in patient samples, the detection rates were 62% (132 colorectal cancer patients; median number = 11 CTCs), 0% (120 patients with other common cancers), 6% (50 colorectal adenoma patients), 0% (120 patients with benign colorectal diseases), and 0% (40 normal subjects). Furthermore, statistical analysis showed that CK20 pCTC numbers were associated with tumor-node-metastasis stage and lymph node status. Using the median CK20 pCTC numbers as the cutoff points, stratified groups of colorectal cancer patients had significant differences in their recurrence, metastasis, and survival. Finally, chromosome 17 aneusomy in 90% of colorectal cancer patients with CK20 pCTCs matched with those from the primary tumors.

CONCLUSIONS

Detection of CK20 pCTCs using the new protocol could generate clinically important information for colorectal cancer patients.

The human keratins: biology and pathology

The keratins are the typical intermediate filament proteins of epithelia, showing an outstanding degree of molecular diversity. Heteropolymeric filaments are formed by pairing of type I and type II molecules. In humans 54 functional keratin genes exist. They are expressed in highly specific patterns related to the epithelial type and stage of cellular differentiation. About half of all keratins—including numerous keratins characterized only recently—are restricted to the various compartments of hair follicles. As part of the epithelial cytoskeleton, keratins are important for the mechanical stability and integrity of epithelial cells and tissues. Moreover, some keratins also have regulatory functions and are involved in intracellular signaling pathways, e.g. protection from stress, wound healing, and apoptosis. Applying the new consensus nomenclature, this article summarizes, for all human keratins, their cell type and tissue distribution and their functional significance in relation to transgenic mouse models and human hereditary keratin diseases. Furthermore, since keratins also exhibit characteristic expression patterns in human tumors, several of them (notably K5, K7, K8/K18, K19, and K20) have great importance in immunohistochemical tumor diagnosis of carcinomas, in particular of unclear metastases and in precise classification and subtyping. Future research might open further fields of clinical application for this remarkable protein family.

Isolated tumor cells and circulating CK20 mRNA in pN0 colorectal cancer patients

Micrometastases in lymph nodes and blood may provide important prognostic information. In this study, cytokeratin 20 (CK20) positive cells in lymph nodes and circulating CK20 mRNA were studied using 57 paraffin-embedded lymph node specimens and blood from 24 patients with pN0 colorectal cancer (CRC), respectively. Results showed that 29 out of 56 (52%) lymph node specimens had CK20-positive cells (range: 1-35). Follow-up of the patients for 12 months indicated that 4 patients (7%) had CRC metastases to liver, lung, and bone. In addition, 8 out of 24 (33%) samples had at least 2-fold circulating CK20 mRNA expression higher than the pooled normal sample. This study provides evidence that CK20-positive cells were found in the lymph nodes and differentially expressed circulating CK20 mRNA was also detected in the blood from patients with pN0 CRC. Long-term follow-up is necessary to study their prognostic use in patients with non-metastatic CRC.