Comparison of immunocytochemistry, reverse transcriptase polymerase chain reaction, and nucleic acid sequence-based amplification for the detection of circulating breast cancer cells

Circulating tumor cells in gastric cancer: developments and clinical applications

Circulating tumor cells (CTCs), which are shed from primary tumor or metastatic sites into the bloodstream and subsequently seed into distant tissues, are considered as the precursors of metastases. Gastric cancer (GC) is a highly heterogeneous malignant tumor. With regard to the diagnosis of GC, secondary pathological biopsy is difficult, while invasive examination is harmful to patients. In recent years, CTCs have made great progress in tumor diagnosis, prognosis prediction, efficacy detection and treatment guidance, but the research on the role of CTCs in GC remains limited. The following sections review the landmark studies demonstrating the technical approaches of CTCs monitoring in the field of GC. Moreover, we highlight the clinical application of CTCs numbers and phenotypes in monitoring the therapeutic efficacy and judging patient prognosis by sequential blood analyses.

Circulating tumor cells detected in follow-up predict survival outcomes in tri-modality management of advanced non-metastatic esophageal cancer: a secondary analysis of the QUINTETT randomized trial

Background

Our aim was to establish if presence of circulating tumor cells (CTCs) predicted worse outcome in patients with non-metastatic esophageal cancer undergoing tri-modality therapy.

Methods

We prospectively collected CTC data from patients with operable non-metastatic esophageal cancer from April 2009 to November 2016 enrolled in our QUINTETT esophageal cancer randomized trial (NCT00907543). Patients were randomized to receive either neoadjuvant cisplatin and 5-fluorouracil (5-FU) plus radiotherapy followed by surgical resection (Neoadjuvant) or adjuvant cisplatin, 5-FU, and epirubicin chemotherapy with concurrent extended volume radiotherapy following surgical resection (Adjuvant). CTCs were identified with the CellSearch® system before the initiation of any treatment (surgery or chemoradiotherapy) as well as at 6-, 12-, and 24-months post-treatment. The threshold for CTC positivity was one and the findings were correlated with patient prognosis.

Results

CTC data were available for 74 of 96 patients and identified in 27 patients (36.5%) at a median follow-up of 13.1months (interquartile range:6.8-24.1 months). Detection of CTCs at any follow-up visit was significantly predictive of worse disease-free survival (DFS;hazard ratio [HR]: 2.44; 95% confidence interval [CI]: 1.41-4.24; p=0.002), regional control (HR: 6.18; 95% CI: 1.18-32.35; p=0.031), distant control (HR: 2.93; 95% CI: 1.52-5.65;p=0.001) and overall survival (OS;HR: 2.02; 95% CI: 1.16-3.51; p=0.013). After adjusting for receiving neoadjuvant vs. adjuvant chemoradiotherapy, the presence of CTCs at any follow-up visit remained significantly predictive of worse OS ([HR]:2.02;95% [Cl]:1.16-3.51; p=0.013) and DFS (HR: 2.49;95% Cl: 1.43-4.33; p=0.001). Similarly, any observed increase in CTCs was significantly predictive of worse OS (HR: 3.14; 95% CI: 1.56-6.34; p=0.001) and DFS (HR: 3.34; 95% CI: 1.67-6.69; p<0.001).

Conclusion

The presence of CTCs in patients during follow-up after tri-modality therapy was associated with significantly poorer DFS and OS regardless of timing of chemoradiotherapy.

The Diagnostic and Prognostic Value of a Liquid Biopsy for Esophageal Cancer: A Systematic Review and Meta-Analysis

Simple Summary

The “liquid biopsy” is a novel concept for detecting circulating biomarkers in the peripheral blood of patients with various cancers, including esophageal cancer. There are two main methods to identify circulating cancer related biomarkers such as morphological techniques or molecular biological techniques. There are some differences in the sensitivity and specificity for detecting circulating tumor cells (CTCs) or circulating markers between each method. Although it is still challenging to determine strong candidates for early diagnosis and predicting prognosis in patients with esophageal cancer, our meta-analysis might be a milestone for the future development of liquid biopsies in use with esophageal cancer.

Abstract

Esophageal cancer is among the most aggressive diseases, and circulating tumor cells (CTCs) have been recognized as novel biomarkers for various cancers over the past two decades, including esophageal cancer. CTCs might provide crucial clinical information for predicting cancer prognosis, monitoring therapeutic responses or recurrences, or elucidating the mechanism of metastasis. The isolation of CTCs is among the applications of a “liquid biopsy”. There are various technologies for liquid biopsies, and they are classified into two main methods: cytometric or non-cytometric techniques. Here, we review a total of 57 eligible articles to summarize various technologies for the use of a liquid biopsy in esophageal cancer and perform a meta-analysis to assess the clinical utility of liquid biopsies as a prognostic and diagnostic biomarker technique. For prognostic evaluation, the pooled hazard ratio in the cytometric assay is relatively higher than that of the non-cytometric assay. On the other hand, a combination of multiple molecules, using a non-cytometric assay, might be a favorable biomarker technique for the early diagnosis of esophageal cancer. Although determining strong evidence for a biomarker by using a liquid biopsy is still challenging, our meta-analysis might be a milestone for the future development of liquid biopsies in use with esophageal cancer.

Analysis of circulating tumor DNA in breast cancer as a diagnostic and prognostic biomarker

Despite all the advances in diagnosis and treatment of breast cancer, a large number of patients suffer from late diagnosis or recurrence of their disease. Current available imaging modalities do not reveal micrometastasis and tumor biopsy is an invasive method to detect early stage or recurrent cancer, signifying the need for an inexpensive, non-invasive diagnostic modality. Cell-free tumor DNA (ctDNA) has been tried for early detection and targeted therapy of breast cancer, but its diagnostic and prognostic utility is still under investigation. This review summarizes the existing evidence on the use of ctDNA specifically in breast cancer, including detection methods, diagnostic accuracy, role in genetics and epigenetics evaluation of the tumor, and comparison with other biomarkers. Current evidence suggests that increasing levels of ctDNA in breast cancer can be of significant diagnostic value for early detection of breast cancer although the sensitivity and specificity of the methods is still suboptimal. Additionally, ctDNA allows for characterizing the tumor in a non-invasive way and monitor the response to therapy, although discordance of ctDNA results with direct biopsy (i.e. due to tumor heterogeneity) is still considered a notable limitation.

Clinical significance of circulating tumor cells in gastric cancer patients

Circulating tumor cells (CTCs) are rare cancer cells released from tumors into the blood stream that are thought to have a key role in cancer metastasis. Investigation of CTCs is an exciting area of research but remains in its infancy, and the presence of CTCs has been associated with worse prognosis in several major cancer types. Gastric cancer (GC) is a highly lethal malignancy and a serious public health concern in East Asia especially in China. There is an urgent need for identifying new, better prognostic markers to enhance diagnosis and prognosis, facilitate drug development, and to improve the treatment of gastric cancer patients. There are considerable interests in gastric CTCs given their potential use as gastric cancer biomarkers. This review highlights recent advances in studies of gastric CTCs, including the isolation and biological molecular characteristics of gastric CTCs, and their clinical significance.

Circulating tumor cells in genitourinary tumors

Management of advanced urogenital malignancies has profoundly changed in recent years due to the development of novel targeted drugs that have significantly improved patient's clinical outcomes. This process has been made possible mainly thanks to better knowledge of tumor genetic alterations and molecular altered pathways. Despite these remarkable results, several issues such as early detection of the disease as well as the research into early markers of recurrence or disease progression still remain an open challenge for clinical research. The detection of circulating tumor cells and circulating DNA appears an attractive option since it is a minimally invasive approach potentially able to allow clinicians an accurate diagnosis and maybe lead to more customized treatment strategies. This review focuses on the current techniques adopted for the detection and isolation of circulating tumor cells in genitourinary tumors highlighting their present and possible future application in clinical practice.

Clinical significance of circulating tumor cells in blood from patients with gastric cancer

Circulating tumor cells (CTC) have been focused on as a target for detecting occult tumors, predicting therapeutic responses and prognoses, and monitoring postoperative recurrence in the clinical management of patients with various malignancies, including gastric cancer. Recent advances in molecular diagnostic tools have contributed to high sensitivity and specificity for the detection of CTC. A conspicuous disparity exists in the incidence of CTC among studies. However, a close relationship has been reported between positivity for CTC and well‐known prognostic clinicopathological factors including depth of tumor invasion, lymph node metastasis, stage, and lymphatic and venous invasion in patients with gastric cancer. According to most studies published on the clinical impact of CTC, the presence of CTC negatively affects the prognosis of patients with gastric cancer. Moreover, the study of CTC based on a meta‐analysis demonstrated their importance as a poor prognostic indicator. In clinical management, pre‐ and post‐therapeutic monitoring of CTC using liquid biopsy may be useful for early detection of subclinical patients or disease recurrence, prediction of tumor progression, and administrative control of adjuvant chemotherapy. Although their functional properties remain unclear, molecular profiling of CTC may contribute to the development of personalized treatment that effectively inhibits tumor progression in patients with advanced gastric cancer. We herein review the clinical significance of CTC as a promising blood marker and therapeutic target in patients with gastric cancer.

Application of optically-induced-dielectrophoresis in microfluidic system for purification of circulating tumour cells for gene expression analysis- Cancer cell line model

Circulating tumour cells (CTCs) in a blood circulation system are associated with cancer metastasis. The analysis of the drug-resistance gene expression of cancer patients' CTCs holds promise for selecting a more effective therapeutic regimen for an individual patient. However, the current CTC isolation schemes might not be able to harvest CTCs with sufficiently high purity for such applications. To address this issue, this study proposed to integrate the techniques of optically induced dielectrophoretic (ODEP) force-based cell manipulation and fluorescent microscopic imaging in a microfluidic system to further purify CTCs after the conventional CTC isolation methods. In this study, the microfluidic system was developed, and its optimal operating conditions and performance for CTC isolation were evaluated. The results revealed that the presented system was able to isolate CTCs with cell purity as high as 100%, beyond what is possible using the previously existing techniques. In the analysis of CTC gene expression, therefore, this method could exclude the interference of leukocytes in a cell sample and accordingly contribute to higher analytical sensitivity, as demonstrated in this study. Overall, this study has presented an ODEP-based microfluidic system capable of simply and effectively isolating a specific cell species from a cell mixture.

A fluorescence turn-on biosensor based on graphene quantum dots (GQDs) and molybdenum disulfide (MoS2) nanosheets for epithelial cell adhesion molecule (EpCAM) detection

This paper presents a "turn-on" fluorescence biosensor based on graphene quantum dots (GQDs) and molybdenum disulfide (MoS₂) nanosheets for rapid and sensitive detection of epithelial cell adhesion molecule (EpCAM). PEGylated GQDs were used as donor molecules, which could not only largely increase emission intensity but also prevent non-specific adsorption of PEGylated GQD on MoS₂ surface. The sensing platform was realized by adsorption of PEGylated GQD labelled EpCAM aptamer onto MoS₂ surface via van der Waals force. The fluorescence signal of GQD was then quenched by MoS₂ nanosheets via fluorescence resonance energy transfer (FRET) mechanism. In the presence of EpCAM protein, the stronger specific affinity interaction between aptamer and EpCAM protein could detach GQD labelled EpCAM aptamer from MoS₂ nanosheets, leading to the restoration of fluorescence intensity. By monitoring the change of fluorescence signal, the target EpCAM protein could be detected sensitively and selectively with a linear detection range from 3nM to 54nM and limit of detection (LOD) around 450pM. In addition, this nanobiosensor has been successfully used for EpCAM-expressed breast cancer MCF-7 cell detection.

The potential for liquid biopsies in the precision medical treatment of breast cancer

Currently the clinical management of breast cancer relies on relatively few prognostic/predictive clinical markers (estrogen receptor, progesterone receptor, HER2), based on primary tumor biology. Circulating biomarkers, such as circulating tumor DNA (ctDNA) or circulating tumor cells (CTCs) may enhance our treatment options by focusing on the very cells that are the direct precursors of distant metastatic disease, and probably inherently different than the primary tumor's biology. To shift the current clinical paradigm, assessing tumor biology in real time by molecularly profiling CTCs or ctDNA may serve to discover therapeutic targets, detect minimal residual disease and predict response to treatment. This review serves to elucidate the detection, characterization, and clinical application of CTCs and ctDNA with the goal of precision treatment of breast cancer.

Circulating tumor cells in germ cell tumors: are those biomarkers of real prognostic value? A review

Analysis of circulating tumor cells from patients with different types of cancer is nowadays a fascinating new tool of research and their number is proven to be useful as a prognostic factor in metastatic breast, colon and prostate cancer patients. Studies are going beyond enumeration, exploring the circulating tumor cells to better understand the mechanisms of tumorigenesis, invasion and metastasis and their value for characterization, prognosis and tailoring of treatment. Few studies investigated the prognostic significance of circulating tumor cells in germ cell tumors. In this review, we examine the possible significance of the detection of circulating tumor cells in this setting.

Prognostic significance of circulating tumor cells in esophageal carcinoma: a meta-analysis

PURPOSE

The prognostic significance of circulating tumor cells (CTCs) in esophageal carcinoma (EC) is controversial. We aim to assess its association with clinicopathological and prognostic relevance in EC by using a meta-analysis.

METHODS

We searched PubMed, Cochrane Database, Embase databases, and the references in relevant studies that assessed the clinicopathological or prognostic relevance of CTCs in peripheral blood of patients with EC. Statistical analyses were conducted by using Stata software to calculate the pooled odds ratio (OR), hazard ratio (HR), and 95% confidence intervals (CIs) using fixed or random-effects models according to the heterogeneity of included studies. The subgroup analyses were performed according to ethnicity, histological type, and detection method.

RESULTS

Sixteen trials containing 1,260 patients were included for analysis. Pooled results showed that presence of CTCs was significantly associated with poor overall survival (HR =1.71, 95% CI [1.30, 2.12], P<0.001) and progression-free survival (HR =1.67, 95% CI [1.19, 2.15], P<0.001) in EC patients. Subgroup analysis indicated that presence of CTCs was closely associated with worse overall survival (Asian: HR =1.66, 95% CI [1.24, 2.08], P<0.001; squamous cell carcinoma [SCC]: HR =1.66, 95% CI [1.24, 2.08], P<0.001; no polymerase chain reaction [PCR]: HR =2.08, 95% CI [1.40, 2.76], P<0.001) and progression-free survival (Asian: HR =1.63, 95% CI [1.15, 2.12], P<0.001; SCC: HR =1.63, 95% CI [1.15, 2.12], P<0.001; PCR: HR =1.63, 95% CI [1.15, 2.12], P<0.001). Additionally, ORs showed that presence of CTCs was significantly correlated with tumor node metastasis (TNM) staging (overall: OR = 1.96, 95% CI [1.34, 2.87], P=0.001; Asian: OR =2.09, 95% CI [1.37, 3.19], P=0.001; SCC: OR =1.97, 95% CI [1.21, 3.07], P=0.003; PCR: OR =2.23, 95% CI [1.43, 3.47], P<0.001), venous invasion (overall: OR =2.23, 95% CI [1.46, 3.40], P<0.001; Asian: OR =2.23, 95% CI [1.46, 3.40], P<0.001; SCC: OR =2.23, 95% CI [1.46, 3.40], P<0.001; PCR: OR =2.23, 95% CI [1.46, 3.40], P<0.001), lymph node metastasis (overall: OR =2.41, 95% CI [1.50, 3.86], P<0.001; Asian: OR =2.89, 95% CI [1.80, 4.65], P<0.001; SCC: OR =2.44, 95% CI [1.47, 4.07], P=0.001; PCR: OR =2.89, 95% CI [1.80, 4.65], P<0.001) and distant metastasis (Asian: OR =2.68, 95% CI [1.01, 7.08], P=0.047) in patients with EC.

CONCLUSION

The presence of CTCs indicates a poor prognosis in EC patients, especially in Asian and SCC patients. Further well-designed prospective studies are recommended to explore the clinical applications of CTCs in patients with EC.

Oligonucleotide aptamers: A next-generation technology for the capture and detection of circulating tumor cells

A critical challenge for treating cancer is the early identification of those patients who are at greatest risk of developing metastatic disease. The number of circulating tumor cells (CTCs) in cancer patients has recently been shown to be a valuable (and non-invasively accessible) diagnostic indicator of the state of metastatic disease. CTCs are rare cancer cells found in the blood circulation of cancer patients believed to provide a means of diagnosing the likelihood for metastatic spread and assessing response to therapy in advanced, as well as early stage disease settings. Numerous technical efforts have been made to reliably detect and quantify CTCs, but the development of a universal assay has proven quite difficult. Notable challenges for developing a broadly useful CTC-based diagnostic assay are the development of easy-to-operate methods that (1) are sufficiently sensitive to reliably detect the small number of CTCs that are present in the circulation and (2) can capture the molecular heterogeneity of tumor cells. In this review, we describe recent progress towards the application of synthetic oligonucleotide aptamers as promising, novel, robust tools for the isolation and detection of CTCs. Advantages and challenges of the aptamer approach are also discussed.

Development of a microfluidic-based optical sensing device for label-free detection of circulating tumor cells (CTCs) through their lactic acid metabolism

This study reports a microfluidic-based optical sensing device for label-free detection of circulating tumor cells (CTCs), a rare cell species in blood circulation. Based on the metabolic features of cancer cells, live CTCs can be quantified indirectly through their lactic acid production. Compared with the conventional schemes for CTC detection, this label-free approach could prevent the biological bias due to the heterogeneity of the surface antigens on cancer cells. In this study, a microfluidic device was proposed to generate uniform water-in-oil cell-encapsulating micro-droplets, followed by the fluorescence-based optical detection of lactic acid produced within the micro-droplets. To test its feasibility to quantify cancer cells, experiments were carried out. Results showed that the detection signals were proportional to the number of cancer cells within the micro-droplets, whereas such signals were insensitive to the existence and number of leukocytes within. To further demonstrate its feasibility for cancer cell detection, the cancer cells with known cell number in a cell suspension was detected based on the method. Results revealed that there was no significant difference between the detected number and the real number of cancer cells. As a whole, the proposed method opens up a new route to detect live CTCs in a label-free manner.

High-purity and label-free isolation of circulating tumor cells (CTCs) in a microfluidic platform by using optically-induced-dielectrophoretic (ODEP) force

Negative selection-based circulating tumor cell (CTC) isolation is believed valuable to harvest more native, and in particular all possible CTCs without biases relevant to the properties of surface antigens on the CTCs. Under such a cell isolation strategy, however, the CTC purity is normally compromised. To address this issue, this study reports the integration of optically-induced-dielectrophoretic (ODEP) force-based cell manipulation, and a laminar flow regime in a microfluidic platform for the isolation of untreated, and highly pure CTCs after conventional negative selection-based CTC isolation. In the design, six sections of moving light-bar screens were continuously and simultaneously exerted in two parallel laminar flows to concurrently separate the cancer cells from the leukocytes based on their size difference and electric properties. The separated cell populations were further partitioned, delivered, and collected through the two flows. With this approach, the cancer cells can be isolated in a continuous, effective, and efficient manner. In this study, the operating conditions of ODEP for the manipulation of prostate cancer (PC-3) and human oral cancer (OEC-M1) cells, and leukocytes with minor cell aggregation phenomenon were first characterized. Moreover, performances of the proposed method for the isolation of cancer cells were experimentally investigated. The results showed that the presented CTC isolation scheme was able to isolate PC-3 cells or OEC-M1 cells from a leukocyte background with high recovery rate (PC-3 cells: 76-83%, OEC-M1 cells: 61-68%), and high purity (PC-3 cells: 74-82%, OEC-M1 cells: 64-66%) (set flow rate: 0.1 μl min(-1) and sample volume: 1 μl). The latter is beyond what is currently possible in the conventional CTC isolations. Moreover, the viability of isolated cancer cells was evaluated to be as high as 94 ± 2%, and 95 ± 3% for the PC-3, and OEC-M1 cells, respectively. Furthermore, the isolated cancer cells were also shown to preserve their proliferative capability. As a whole, this study has presented an ODEP-based microfluidic platform that is capable of isolating CTCs in a continuous, label-free, cell-friendly, and particularly highly pure manner. All these traits are found particularly meaningful for exploiting the harvested CTCs for the subsequent cell-based, or biochemical assays.

Markers of circulating breast cancer cells

The detection of circulating tumor cells (CTC) aids in diagnosis of disease, prognosis, disease recurrence, and therapeutic response. The molecular aspects of metastasis are reviewed including its relevance in the identification and characterization of putative markers that may be useful in the detection thereof. Also discussed are methods for CTC enrichment using molecular strategies. The clinical application of CTC in the metastatic disease process is also summarized.

Isolation of rare circulating tumor cells in cancer patients: technical aspects and clinical implications

Circulating tumor cells (CTCs) may be detected in the blood of patients with epithelial tumors using different analytical approaches. The relative number of CTCs is low and they include a heterogeneous population of cells with diverse biological and molecular characteristics, often different from those of the respective primary tumor. Until recently, they have been difficult to detect and, even though discordant results have been reported when different methods of detection were used, they may provide prognostic and predictive information. Several antibody- or molecular-based CTC detection methods have been developed, offering hope for individualized risk assessment by utilizing CTCs as biomarkers of disease progression and drug response. Pilot studies have also shown that by utilizing methods that permit, besides enumeration, a molecular characterization of CTCs, one could better identify high-risk patients, predict response to targeted therapies, analyze gene expression profiles (in order to identify new potential drug targets) and increase our knowledge of the metastatic process. In this article we review the techniques currently utilized for isolation and characterization of CTCs and we discuss their potential utility in clinical oncology focusing on the future perspectives in this field.

A direct comparison of CellSearch and ISET for circulating tumour-cell detection in patients with metastatic carcinomas

Background:

Circulating tumour cells (CTCs) can provide information on patient prognosis and treatment efficacy. However, there is no universal method to detect CTC currently available. Here, we compared the performance of two CTC detection systems based on the expression of the EpCAM antigen (CellSearch assay) or on cell size (ISET assay).

Methods:

Circulating tumour cells were enumerated in 60 patients with metastatic carcinomas of breast, prostate and lung origins using CellSearch according to the manufacturer's protocol and ISET by studying cytomorphology and immunolabelling with anti-cytokeratin or lineage-specific antibodies.

Results:

Concordant results were obtained in 55% (11 out of 20) of the patients with breast cancer, in 60% (12 out of 20) of the patients with prostate cancer and in only 20% (4 out of 20) of lung cancer patients.

Conclusion:

Our results highlight important discrepancies between the numbers of CTC enumerated by both techniques. These differences depend mostly on the tumour type. These results suggest that technologies limiting CTC capture to EpCAM-positive cells, may present important limitations, especially in patients with metastatic lung carcinoma.

Circulating tumor cells: advances in detection methods, biological issues, and clinical relevance

BACKGROUND

Circulating tumor cells (CTCs) have long been considered a reflection of tumor aggressiveness. Hematogenous spreading of CTCs from a primary tumor is a crucial step in the metastasis cascade, which leads ultimately to the formation of overt metastases. However, owing to the rarity of CTCs in peripheral blood, detecting these cells requires methods combined with high sensitivity and specificity, which sets tremendous challenges for the implementation of these assays into clinical routine.

METHODS

Generally, CTCs detection methods are composed of the following two steps: enrichment (isolation) process (morphological and immunological techniques) and detection (identification) process (cytometric and nucleic acid techniques), which may or may not be separate from enrichment. Genetic and molecular characterization of CTCs carried out by fluorescent in situ hybridization (FISH), comparative genomic hybridization (CGH), PCR-based techniques, and biomarker immunofluorescent staining extract more information about malignant profile, metastatic potential of CTCs, and the extent to which CTCs are genetically identical to the primary tumor.

RESULTS

Recent technical advances made it possible to detect CTCs. The efficacy of circulating tumor cell (CTC) detection among patients with solid malignancy has been investigated, which shows great potential to become a tool for real-time parameter of prognosis and serve as an early marker to assess the therapeutic response in overt cancers. Improvements in detection and characterization of CTCs will hopefully lead to refinement of clinical management of cancer patients.

CONCLUSION

This review addresses the majority of assays that have been published thus far, including the enrichment and detection steps and the markers used in these assays, accompanied by some biological issues of CTC and the results of clinical application harvested.

The clinical significance of circulating tumor cells in non-metastatic colorectal cancer--a review

BACKGROUND

Finding a clinical tool to improve the risk stratification and identifying those colorectal cancer patients with an increased risk of recurrence is of great importance. The presence of circulating tumor cells (CTC) in peripheral blood can be a strong marker of poor prognosis in patients with metastatic disease, but the prognostic role of CTC in non-metastatic colorectal cancer is less clear. The aim of this review is to examine the possible clinical significance of circulating tumor cells in non-metastatic colorectal cancer (TNM-stage I-III) with the primary focus on detection methods and prognosis.

METHODS

The PubMed and Cochrane database and reference lists of relevant articles were searched for scientific literature published in English from January 2000 to June 2010. We included studies with non-metastatic colorectal cancer (TNM-stage I-III) and CTC detected pre- and/or post-operatively in peripheral blood.

RESULTS

Nine studies qualified for further analyses. Detection rates of CTC in peripheral blood of patients with non-metastatic colorectal cancer varied from 4% to 57%. Seven studies applied RT-PCR and two studies used immunocytochemical methods. Seven studies found the presence of CTC to be a prognostic marker of poor disease-free survival.

CONCLUSION

The presence of CTC in peripheral blood is a potential marker of poor disease-free survival in patients with non-metastatic colorectal cancer. The low abundance of CTC in non-metastatic colorectal cancer requires very sensitive and specific detection methods. An international consensus on choice of detection method and markers, is warranted before incorporating CTC into risk stratification in the clinical setting.

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.

Circulating tumour cell detection: a direct comparison between the CellSearch System, the AdnaTest and CK-19/mammaglobin RT-PCR in patients with metastatic breast cancer

BACKGROUND

The detection, enumeration and isolation of circulating tumour cells (CTCs) have considerable potential to influence the clinical management of patients with breast cancer. There is, however, substantial variability in the rates of positive samples using existing detection techniques. The lack of standardisation of technology hampers the implementation of CTC measurement in clinical routine practice.

METHODS

This study was designed to directly compare three techniques for detecting CTCs in blood samples taken from 76 patients with metastatic breast cancer (MBC) and from 20 healthy controls: the CellSearch CTC System, the AdnaTest Breast Cancer Select/Detect and a previously developed real-time qRT-PCR assay for the detection of CK-19 and mammaglobin transcripts.

RESULTS

As a result, 36% of patients with MBC were positive by the CellSearch System, 22% by the AdnaTest, 26% using RT-PCR for CK-19 and 54% using RT-PCR for mammaglobin. Samples were significantly more likely to be positive for at least one mRNA marker using RT-PCR than using the CellSearch System (P=0.001) or the AdnaTest (P<0.001).

CONCLUSION

We observed a substantial variation in the detection rates of CTCs in blood from breast cancer patients using three different techniques. A higher rate of positive samples was observed using a combined qRT-PCR approach for CK-19 and mammaglobin, which suggests that this is currently the most sensitive technique for detecting CTCs.

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.

Circulating tumor cells (CTCs): detection methods and their clinical relevance in breast cancer

The enumeration of circulating tumor cells has long been regarded as an attractive diagnostic tool, as circulating tumor cells are thought to reflect aggressiveness of the tumor and may assist in therapeutic decisions in patients with solid malignancies. However, implementation of this assay into clinical routine has been cumbersome, as a validated test was not available until recently. Circulating tumor cells are rare events which can be detected specifically only by using a combination of surface and intracellular markers, and only recently a number of technical advances have made their reliable detection possible. Most of these new techniques rely on a combination of an enrichment and a detection step. This review addresses the assays that have been described so far in the literature, including the enrichment and detection steps and the markers used in these assays. We have focused on breast cancer as most clinical studies on CTC detection so far have been done in these patients.

Diagnostic accuracy of small breast epithelial mucin mRNA as a marker for bone marrow micrometastasis in breast cancer: a pilot study

BACKGROUND

Detection of isolated tumour cells (ITC) in the blood or minimal deposits in distant organs such as bone marrow (BM) could be important to identify breast cancer patients at high risk of relapse or disease progression. PCR amplification of tissue or tumour selective mRNA is the most powerful analytical tool for detection of this micrometastasis. We have evaluated for the first time, the diagnostic accuracy of small breast epithelial mucin (SBEM) as a potential marker for BM micrometastasis in breast cancer.

METHODS

A nested RT-PCR assay for detection of SBEM mRNA was compared with immunocytochemistry (ICC) with anticytokeratin AE1/AE3 antibody in paired samples obtained from the BM of breast cancer patients. Associations of SBEM mRNA detection in BM and clinical and pathological parameters were evaluated. SBEM mRNA status and time to breast cancer progression were analysed using Kaplan-Meyer curves.

RESULTS

Fifty stages I-IV breast cancer female patients were prospectively included in our study. SBEM specific transcript was found in BM in 26% of the patients. Detection rate was similar to the percentage of patients with ITCs detected using ICC (24%). SBEM mRNA in BM aspirates were significantly associated with presence of clinically active disease, including locally advanced and metastatic patients (47%, P = 0.021) and tumours with positive hormonal receptors (36.7%, P = 0.035). In addition association with Her2/neu over-expression (44.4%, P = 0.051) and low proliferating tumours (36%, P = 0.067) were close to significant levels. When we analysed time to breast cancer progression adjusting for grade or hormone receptor status, presence of SBEM mRNA in BM defines distinct prognostic groups.

CONCLUSIONS

SBEM might represent a suitable marker for molecular detection of ITCs in BM in breast cancer patients. Analysis of prognostic value for SBEM mRNA-based assay should take into account the heterogeneity and different molecular subtypes of breast cancer.

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.

Towards an optimized platform for the detection, enrichment, and semi-quantitation circulating tumor cells

Metastasis describes the process of migration of a frequently clinically occult circulating tumor cell (CTC) from the primary lesion to a new location and the subsequent formation of an overt growth. We and others have shown that the detection and quantitation of these cells has significant prognostic value, however there still remains no consensus as to the optimal methods to achieve this. The work described herein therefore considered various techniques, from storage and sample processing to data acquisition and analysis, to find an optimal combination of methods for an effective and practical platform for the detection of CTCs in peripheral blood. A dual-antigen epithelial cell enrichment procedure followed by a multi-marker QPCR analysis demonstrated the highest sensitivity and specificity, with the ability to detect as few as 10 tumor cells from a background of 10(6) peripheral blood mononuclear cells. Using these techniques in conjunction with a quadratic linear discriminant analysis (QDA) resulted in a platform able to generate this data and then combine it a single score for each patient, in which positivity reflected tumor cell presence, and negativity represented tumor cell absence. This assay was able to correctly determine tumor cell presence or absence in 100% of healthy controls and 84% of metastatic patients in a validation cohort of 39 individuals. This platform represents a highly sensitive and specific assay which could augment current routine assays for CTCs in the clinic.

Postoperative serum proteomic profiles may predict metastatic relapse in high-risk primary breast cancer patients receiving adjuvant chemotherapy

A total of 30-50% of early breast cancer (EBC) patients considered as high risk using standard prognostic factors develop metastatic recurrence despite standard adjuvant systemic treatment. A means to better predict clinical outcome is needed to optimize and individualize therapeutic decisions. To identify a protein signature correlating with metastatic relapse, we performed surface-enhanced laser desorption/ionization-time of flight mass spectrometry profiling of early postoperative serum from 81 high-risk EBC patients. Denatured and fractionated serum samples were incubated with IMAC30 and CM10 ProteinChip arrays. Several protein peaks were differentially expressed according to clinical outcome. By combining partial least squares and logistic regression methods, we built a multiprotein model that correctly predicted outcome in 83% of patients. The 5-year metastasis-free survival in 'good prognosis' and 'poor prognosis' patients as defined using the multiprotein index were strikingly different (83 and 22%, respectively; P<0.0001, log-rank test). In a multivariate Cox regression including conventional pathological factors and multiprotein index, the latter retained the strongest independent prognostic significance for metastatic relapse. Major components of the multiprotein index included haptoglobin, C3a complement fraction, transferrin, apolipoprotein C1 and apolipoprotein A1. Therefore, postoperative serum protein pattern may have an important prognostic value in high-risk EBC.

Evaluation of expression based markers for the detection of breast cancer cells

INTRODUCTION

Genes that are expressed in a highly tissue- or disease-specific manner provide possible targets for therapeutics, early detection of cancer, and monitoring of disease burden during and after treatment. Further, genes of this type that code for secreted or shed proteins may allow for serum detection of the product facilitating our ability to specifically detect the cancer in all circumstances. To this end, we are working towards identification and characterization of such genes that are specifically expressed in breast epithelium. In the current study, we have measured the expression of two markers that emerged from a screen of the Incyte LifeSeq Database and were subsequently shown to be highly restricted to breast epithelium termed BU101 (also called Lipophilin B) and BS106 (small mucin-like protein). These two novel markers were compared with two other candidate markers, Mammaglobin and Cytokeratin 19 (CK19).

METHODS

Utilizing quantitative real-time PCR, we compared the expression of these four genes in a series of 95 primary breast cancers, 9 lymph nodes from breast cancer patients, 13 lymph nodes from non-cancer patients and 10 normal breast tissues.

RESULTS

Cytokeratin was shown to be highly sensitive in detecting all breast cancers, while BU101, BS106 and Mammaglobin were more restricted.

CONCLUSION

While no one of the these markers efficiently detects all breast cancers, a combination of two or more could achieve a very high sensitivity in assaying for circulating or occult breast cancer cells.

No common denominator for breast cancer lymph node metastasis

The axillary lymph node status is the most powerful prognostic factor for breast cancer patients to date. The molecular mechanisms that control lymph node metastasis, however, remain poorly understood. To define patterns of genes or gene regulatory pathways that drive breast cancer lymph node metastasis, we compared the gene expression profiles of 15 primary breast carcinomas and their matching lymph node metastases using microarrays. In general, primary breast carcinomas and lymph node metastases do not differ at the transcriptional level by a common subset of genes. No classifier or single gene discriminating the group of primary tumours from those of the lymph node metastases could be identified. Also, in a series of 295 breast tumours, no classifier predicting lymph node metastasis could be developed. However, subtle differences in the expression of genes involved in extracellular-matrix organisation and growth factor signalling are detected in individual pairs of matching primary and metastatic tumours. Surprisingly, however, different sets of these genes are either up- or downregulated in lymph node metastases. Our data suggest that breast carcinomas do not use a shared gene set to accomplish lymph node metastasis.

Detection and quantification of circulating tumor cells in mouse models of human breast cancer using immunomagnetic enrichment and multiparameter flow cytometry

BACKGROUND

Circulating tumor cells (CTCs) in the peripheral blood of breast cancer patients may be an important indicator of metastatic disease and poor prognosis. However, the use of experimental models is required to fully elucidate the functional consequences of CTCs. The purpose of this study was to optimize the sensitivity of multiparameter flow cytometry for detection of human tumor cells in mouse models of breast cancer.

METHODS

MDA-MB-468 human breast cancer cells were serially diluted in whole mouse blood. Samples were lysed and incubated with a fluorescein isothiocyanate-conjugated anti-human leukocytic antigen antibody and a phycoerythrin-conjugated anti-mouse pan-leukocyte CD45 antibody. Samples were then immunomagnetically depleted of CD45-positive leukocytes, fixed, permeabilized, and stained with propidium iodide before flow cytometric analysis.

RESULTS

Human breast cancer cells could be differentiated from mouse leukocytes based on increased light scatter, cell surface marker expression, and aneuploid DNA content. The method was found to have a lower sensitivity limit of 10(-5) and was effective for detecting human breast cancer cells in vivo in the circulation of experimental mice carrying primary human mammary tumors.

CONCLUSIONS

This technique has the potential to be a valuable and sensitive tool for investigating the biological relevance of CTCs in experimental mouse models of breast cancer.

Detection of circulating epithelial cells in the blood of patients with breast cancer: comparison of three techniques

This study compares the sensitivities and specificities of three techniques for the detection of circulating epithelial cells in the blood of patients with breast cancer. The number of circulating epithelial cells present in the blood of 40 patients with metastatic breast cancer and 20 healthy volunteers was determined by: immunomagnetic separation (IMS) and laser scanning cytometry (LSC), cell filtration and LSC and a multimarker real-time RT–PCR assay. Numbers of cytokeratin-positive cells identified and expression of three PCR markers were significantly higher in the blood of patients with breast cancer than in healthy volunteers. Using the upper 95% confidence interval of cells detected in controls to determine positive patient samples: 30% of patients with metastatic breast cancer were positive following cell filtration, 48% following IMS, and 60, 45 and 35% using real-time RT–PCR for cytokeratin 19, mammaglobin and prolactin-inducible peptide. Samples were significantly more likely to be positive for at least one PCR marker than by cell filtration (83 vs 30%, P<0.001) or IMS (83 vs 48%, P<0.001).The use of a multimarker real-time RT–PCR assay was therefore found to be the most sensitive technique for the detection of circulating epithelial cells in the blood of patients with breast cancer.

Characterization and enumeration of cells secreting tumor markers in the peripheral blood of breast cancer patients

In the process of metastasis, malignant cells are released from the primary tumor and migrate to specific organs via the lymphatic and blood circulation systems. These circulating tumor cells have been characterized by immunochemistry, the reverse transcription-polymerase chain reaction, and flow cytometry. Using the MCF-7 breast cancer cell line, we have developed a two-color ELISPOT assay to detect cells secreting cathepsin D protease and MUC1 glycoprotein, markers associated with the risk of metastases in breast cancer. The threshold of detection of this ELISPOT assay was one cathepsin D- or MUC1-secreting MCF7 cell per 5 ml of control blood. In 16 patients with breast carcinoma metastases, 1 to 1940 cathepsin D- or MUC1-secreting cells per 2x10(7) PBMC were enumerated, whereas none were found in 11 controls. Moreover, in six patients 6-60% of MUC1-secreting cells also expressed the CXCR4 chemokine receptor, which is involved in the homing of metastatic breast cancer cells. The ELISPOT assay described here allowed us to enumerate cathepsin D- and/or MUC1-secreting cells in the MCF-7 cell line and in the peripheral blood of patients with disseminated breast cancer. The combination of the ELISPOT assay and CXCR4-positive cell sorting identified subsets of MUC1-secreting cells in the peripheral blood of these patients.

Real-time RT-PCR correlates with immunocytochemistry for the detection of disseminated epithelial cells in bone marrow aspirates of patients with breast cancer

Real-time reverse transcriptase–polymerase chain reaction (RT–PCR) is a technique with the potential of improving the quantification of disseminated epithelial cells (DEC) in haematological tissues due to its exquisite sensitivity. This sensitivity may lead to false positivity. Immunocytochemistry (ICC) is regarded as the standard methodology to diagnose DEC. In this study, detection with ICC was compared with quantitative real-time RT–PCR for CK-19 and mammaglobin (hMAM) mRNA in bone marrow (BM) of patients with metastatic breast cancer (MBC). Bone marrow was aspirated from 14 control patients and from 29 patients with MBC. Mononuclear cells (MNC) were isolated. Immunostaining was carried out with the Epimet kit. Quantitative PCR was performed on the ABI Prism 7700. The CK-19 and hMAM mRNA quantities were normalised against β-Actin and calculated relative to a calibrator sample (relative gene expression). All controls were negative by ICC and for hMAM expression measured by RT–PCR, whereas the median RGE value for CK-19 was 0.57. For the MBC patients, the median RGE for hMAM was 0 and 10 out of 25 (40%) tested positive. Median RGE for CK-19 was 2.9 and 20 out of 25 (80%) tested positive. With ICC, the median value was 1 stained cell per sample, and 15 out of 24 (62%) samples were positive. A correlation was observed between CK-19 and hMAM expression (r=0.7; P=0.0003), and between hMAM expression and ICC (r=0.6; P=0.003). CK-19 expression and ICC (r=0.9; P<0.0001) showed the strongest correlation. Reverse transcriptase–polymerase chain reaction for CK-19 resulted in a higher number of positive BM samples of patients with MBC than ICC. Since an excellent correlation is observed between ICC and RT–PCR, and RT–PCR is probably more sensitive with the advantage of being less observer dependent and thus also more easy to automate, we consider our quantitative real-time RT–PCR method as validated for the detection of DEC in the bone marrow of breast cancer patients.

Detection of metastases in sentinel lymph nodes of breast cancer patients by multiple mRNA markers

Disseminated breast tumour cells in sentinel lymph nodes (SNs) were evaluated by quantitative real-time PCR and the sensitivity of this assay was compared to the routine histological analysis. First, several candidate marker genes were tested for their specificity in axillary lymph nodes (ALN) of 50 breast cancer patients and 43 women without breast cancer. The marker gene panel selected, designed to detect the mRNA of CK19, p1B, EGP2 and SBEM, was subsequently applied to detect metastases in 70 SNs that were free of metastases as determined by standard histological evaluation. Remarkably, seven negative SNs showed increased marker gene expression, suggesting the presence of (micro) metastases. Four of these seven SNs positive by real-time PCR proved to contain tumour deposits after careful review of the slides or further sectioning of the paraffin-embedded material. In three PCR positive SNs, however, no tumour cells were found by haematoxylin and eosin staining (H&E) and immunohistologically analysis. The quantitative real-time PCR assay with multiple mRNA markers for the detection of disseminated breast cancer cells in SNs thus resulted in an upstaging of SNs containing metastastic disease of 10% compared to the routine histological analysis. The application of this technique may be of clinical relevance, as it is suggested that micrometastatic disease in SNs are associated with further nodal non-SN metastases in breast cancer.

Circulating tumour cells in breast cancer

By use of modern immunological and molecular analytical techniques, cells with the characteristics of tumour cells can be detected in the blood of many patients with breast cancer. The ability to detect and characterise such cells routinely could have a profound influence on the early diagnosis of breast cancer, risk stratification in the adjuvant setting, early detection of relapse, and the development of new targeted strategies. In this review we discuss current techniques to detect circulating breast-cancer cells and the limitations of these approaches. We also review the clinical studies in breast cancer and discuss the potential relevance of this research to the future management of the disorder.

Detection of micrometastatic breast cancer by means of real time quantitative RT-PCR and immunostaining in perioperative blood samples and sentinel nodes

The aim of our study was to detect micrometastatic breast cancer by epithelial glycoprotein-2 (EGP-2) and cytokeratin 19 (CK19), using immunostaining and real time quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR). Fifty-eight breast cancer patients, 52 primary tumors, 75 sentinel nodes (SN) and 149 peripheral blood (PB) samples (from before, during and 4 days after operation) were examined. Immunostaining was performed with antibodies directed against EGP-2 and CK19. Detection limits were one Michigan Cancer Foundation-7 (MCF-7) breast cancer cell line cell/2.10(6) leukocytes (immunostaining) and one MCF-7 cell/10(6) leukocytes qRT-PCR. Control noncancer lymph nodes (n = 10) showed nonspecific CK19 staining, but were qRT-PCR negative; control healthy volunteer PB (n = 11) was always negative. Primary tumor samples, all positive with immunostaining, showed a wide variation of EGP-2 (>10(4) fold) and CK19 mRNA expression (>10(3) fold). SN (n = 19) from 16 patients were tumor-positive with routine haematoxylin-eosin (H&E) and/or immunostaining. SN tumor presence was positively correlated to qRT-PCR expression, but 3 tumor-positive SN were false negative with qRT-PCR. Three SN were qRT-PCR positive, while tumor negative with H&E and/or immunostaining. No immunostaining positive PB was observed, but 19 patients (33%) had one or more qRT-PCR positive PB samples. We concluded that primary tumors have varying expressions of EGP-2 and CK19 mRNA. Both markers can be used in qRT-PCR to obtain adequate sensitivity for single tumor cell detection. In SN, immunostaining appears more sensitive/specific than H&E or qRT-PCR for tumor detection. No immunostaining positivity was found in PB, while 33% of patients had qRT-PCR positive PB. The clinical value of these findings will have to be clarified.

Characterization of antibody binding to three cancer-related antigens using flow cytometry and cell tracking velocimetry

Proper antibody labeling is a fundamental step in the positive selection/isolation of rare cancer cells using immunomagnetic cell separation technology. Using either a two-step or single-step labeling protocol, we examined a combination of six different antibodies specific for three different antigens (epithelial specific antigen, epithelial membrane antigen, and HER-2/Neu) on two different breast cancer cell lines (HCC1954 and MCF-7). When a two-step labeling protocol was used (i.e., anti-surface marker-fluoroscein-isothiocyanate [FITC] [primary Ab], anti-FITC magnetic colloid [secondary Ab]) saturation of the primary antibody was determined using fluorescence intensity measurements from flow cytometry (FCM). The saturation of the secondary antibody (or saturation of a single-step labeling) was determined using magnetophoretic mobility measurements from cell tracking velocimetry (CTV). When the maximum magnetophoretic mobility was the primary objective, our results demonstrate that the quantities necessary for antibody saturation with respect to fluorescence intensity were generally higher than those recommended by the manufacturer. The results demonstrate that magnetophoretic mobility varies depending on the types of cell lines, primary antibodies, and concentration of secondary magnetic colloid-conjugated antibody. It is concluded that saturation studies are a vital preparatory step in any separation method involving antibody labeling, especially those that require the specificity of rare cell detection.

Marker genes for circulating tumour cells predict survival in metastasized breast cancer patients

We investigated the prognostic significance of circulating breast cancer cells in peripheral blood detected by quantitative RT-PCR of marker genes in patients with advanced breast cancer. Blood samples from 94 breast cancer patients with metastatic disease (M1) were examined for circulating tumour cells by studying the mRNA expression of CK19, p1B, PS2 and EGP2 by real-time PCR. Using a score function, developed for predicting circulating tumour cells by quadratic discriminant analysis (QDA), the four expression levels were combined into a single discriminant value. Tumour cells were present in 24 out of 94 (31%) of the patients. In 77% (72 out of 94) of the patients distant metastatic disease was localised in the bone. In 36% (26 out of 72) of the patients with bone metastases at the time of blood sampling, a positive QDA for the four genes was found, in contrast to only 14% (three out of 22) without bone involvement. Overall survival rates by Kaplan-Meier revealed no prognostic effect for the presence of bone metastases (P=0.93). However, patients with a positive QDA value did have a progression-free survival at 1 year of 3% and overall survival at 2 years of 17%, against 22 and 36% for patients with a negative QDA value (P=0.015 and 0.0053, respectively). Breast cancer patients with metastatic disease have a significantly worse progression-free and overall survival when circulating tumour cells can be detected in their peripheral blood.

Comparison of the RNA-amplification based methods RT-PCR and NASBA for the detection of circulating tumour cells

Increasingly, reverse transcriptase polymerase chain reaction (RT-PCR) is used to detect clinically significant tumour cells in blood or bone marrow. This may result in a redefinition of disease-free and clinical relapse. However, its clinical utility may be limited by lack of automation or reproducibility. Recent studies have suggested nucleic acid sequence-based amplification of target RNA may be more robust. In this study, nucleic acid sequence-based amplification was established to detect melanoma, colorectal and prostate cancer cells. Nucleic acid sequence-based amplification and RT-PCR both successfully amplified target RNA in peripheral blood samples from patients with melanoma and colorectal cancer, but only RT-PCR detected PSA in blood samples from patients with prostate cancer. There was relatively good agreement between sample replicates analyzed by RT-PCR (Kappa values of one for tyrosinase, 0.67 for CK-20 and one for PSA), but less agreement when analyzed by nucleic acid sequence-based amplification. This may limit the routine use of NASBA for the detection of clinically significant disease. In summary, RT-PCR appears at present to be the most reliable and reproducible method for the detection of low-level disease in cancer patients, although prospective studies are warranted to assess the clinical utility of different molecular diagnostic methods.

Detection of MAGE-A3 in breast cancer patients' sentinel lymph nodes

The detection of occult metastatic breast cancer cells by RT-PCR is limited by the poor specificity of most tumour mRNA markers. MAGE-A3 is a highly specific tumour mRNA marker that is not expressed in non-cancer cells. This study assesses MAGE-A3 mRNA as a molecular marker for the detection of tumour cells in the sentinel lymph nodes (SLN) of breast cancer patients. Serial frozen sections of SLN (n = 121) were obtained from 77 AJCC (American Joint Committee on Cancer) Stage I-IIIA breast cancer patients. MAGE-A3 mRNA analysis of SLN was performed by RT-PCR and Southern blot analysis. Tumour cells were detected in 48 of 121 (40%) SLN from 77 patients by H&E or IHC staining, and 35 of 77 (45%) patients, overall, had histopathologically (H&E and/or IHC) positive SLN. Among histopathologically negative SLN, 28 of 73 (38%) SLN were MAGE-A3 mRNA positive by RT-PCR. Overall, 41 of 77 (53%) patients and 50 of 121 (41%) SLN were positive for MAGE-A3. MAGE-A3 mRNA expression in the SLN occurred more frequently with infiltrating lobular carcinoma (P < 0.001) than with infiltrating ductal carcinoma, adding further evidence of possible phenotypic differences between these 2 subtypes of breast cancer. Due to its high specificity, MAGE-A3 mRNA is a potentially useful marker for detecting breast cancer cells in the SLN. One half of breast tumours expressed MAGE-A3 mRNA, which has important potential implications for antigen-specific targeted immunotherapy.