Circulating tumor cells in solid cancer: Tumor marker of clinical relevance?

Circulating tumor cells are associated with poor outcomes in early-stage hepatocellular carcinoma: a prospective study

BACKGROUND

Previous studies evaluating association between circulating tumor cells (CTCs) and clinical outcomes in hepatocellular carcinoma (HCC) have shown inconsistent results due to suboptimal detection methods and patient heterogeneity.

METHODS

Patients undergoing surgery for early-stage HCC were prospectively enrolled. The CTC numbers were determined using a tapered slit platform, which detects CTCs based on the cell size and morphology. Survival and recurrence were evaluated, and Cox proportional hazards models were used to demonstrate the prognostic significance of CTC.

RESULTS

Of 105 patients, 25 had increased CTC numbers after surgery (ΔCTC > 0, defined as positive) and a significantly higher level of recurrence (p = 0.042). A positive ΔCTC was seen to be an independent predictor of recurrence (hazard ratio 2.28), along with hepatitis B virus infection, alanine aminotransferase level, and the presence of satellite nodules (all p < 0.05). Subgroup analyses showed that a positive ΔCTC was associated with lower survival and higher recurrence among patients with low alpha-fetoprotein levels and cirrhosis (all p < 0.05).

CONCLUSION

Calculation of ΔCTC based on the physical properties of the cells is predictive of recurrence in patients with early HCC undergoing surgery.

Clinical application of circulating tumor cells in breast cancer

Circulating tumor cells (CTCs) play a major role in the metastatic spread of breast cancer. CTC detection has proven to be an important parameter for predicting progression free and overall survival. Collection of CTCs is minimally invasive and can be performed more often than disseminated tumor cell (DTC) collection from bone marrow, thus providing a real-time "liquid biopsy". In this review, the most important techniques for enrichment and detection of CTCs are discussed for clinical application in low and higher staged breast cancer, as well as the genetic and molecular characterization of CTCs. For CTCs, the use of immunology-based enrichment techniques with multiple antibodies is recommended in a clinical setting, as well as the use of cytometric detection techniques, combined with RT-PCR for confirmation. Special attention is given to the value of cancer stem cell (CSC) activity, which may be the main cause of ineffectiveness of the control over metastatic lesions due to intratumor heterogeneity. Accumulating information on CSCs offers new paradigms to generate effective targets for the treatment of metastatic disease. Genetic and molecular characterization of CTCs has potential to stratify patients for optimal personalized treatment regimens. CTCs can be used for monitoring patients during treatment schedules.

Detection and isolation of circulating tumor cells: principles and methods

Efforts to improve the clinical management of several cancers include finding better methods for the quantitative and qualitative analysis of circulating tumor cells (CTCs). However, detection and isolation of CTCs from the blood circulation is not a trivial task given their scarcity and the lack of reliable markers to identify these cells. With a variety of emerging technologies, a thorough review of the exploited principles and techniques as well as the trends observed in the development of these technologies can assist researchers to recognize the potential improvements and alternative approaches. To help better understand the related biological concepts, a simplified framework explaining cancer formation and its spread to other organs as well as how CTCs contribute to this process has been presented first. Then, based on their basic working-principles, the existing methods for detection and isolation of CTCs have been classified and reviewed as nucleic acid-based, physical properties-based and antibody-based methods. The review of literature suggests that antibody-based methods, particularly in conjunction with a microfluidic lab-on-a-chip setting, offer the highest overall performance for detection and isolation of CTCs. Further biological and engineering-related research is required to improve the existing methods. These include finding more specific markers for CTCs as well as enhancing the throughput, sensitivity, and analytic functionality of current devices.

Using circulating tumor cells as a prognostic indicator in metastatic castration-resistant prostate cancer

A more reliable tumor marker is needed as a prognostic indicator in metastatic castration-resistant prostate cancer. Circulating tumor cells (CTCs) are cells that have broken away from a tumor and flow in the bloodstream. Evidence has indicated that the presence of CTCs in the peripheral blood of men with solid malignancies correlates with clinical outcomes. When the CTC number is reduced to fewer than five cells per 7.5 ml of blood, survival outcomes often improve. The relationship between the number of CTCs and prognosis has the potential to influence treatment decisions. Therefore, oncology nurses and practitioners must evaluate the scientific evidence, understand the clinical implications, and realize the impact CTC counts may have on practice to effectively communicate the CTC results to a patient. In addition, oncology nurses and practitioners must know that although favorable changes in CTC count are associated with a better prognosis, that alone cannot be used to guide treatment decisions for an individual.

Detection of circulating tumor cells in peripheral blood from patients with gastric cancer using piRNAs as markers

OBJECTIVE

To investigate the feasibility of detecting circulating cancer cells in peripheral blood from gastric cancer patients using Piwi-interacting RNAs (piRNAs) as markers.

DESIGN AND METHODS

Real-time quantitative reverse transcription-polymerase chain reaction was used to analyze piR-651 and piR-823 levels in the peripheral blood of 93 patients with gastric cancer and 32 healthy volunteers. Receiver operating characteristic (ROC) curves were constructed to evaluate the diagnostic values.

RESULTS

The peripheral blood levels of piR-651 and piR-823 in the patients with gastric cancer were significantly lower than those from controls (P<0.001). The piR-651 level in gastric adenocarcinoma was higher than that in gastric signet ring cell carcinoma (P = 0.003). The piR-823 level was positively associated with tumor-node-metastasis stage (P = 0.027) and distant metastasis (P = 0.026). The areas under the ROC curve were 0.841, 0.812 and 0.860 for piR-651, piR-823 and the combination, respectively.

CONCLUSIONS

piRNAs may be valuable biomarkers for detecting circulating gastric cancer cells.

Enumeration, characterization, and collection of intact circulating tumor cells by cross contamination-free flow cytometry

Circulating tumor cells (CTC) are an important biomarker for several solid cancers. Most of the commercially available systems for enumeration of CTC are based on immunomagnetic enrichment of epithelial cell adhesion molecule (EpCAM/CD326)-expressing CTC before microscopic cell imaging or reverse-transcription PCR (RT-PCR). The aim of this study was to establish a practical method for enumeration of CTC using a novel flow cytometer that has a disposable microfluidic chip, which is designed to realize absolute cross contamination-free measurements and to collect the analyzed cell sample. Although the process of enumeration and labeling of CTC was optimized for this device, the simplified protocol described here could be applied to other flow cytometers. Cultured cancer cells spiked into normal blood were enriched using MACS® EpCAM-MicroBeads following cell labeling with an allophycocyanin (APC)-conjugated EpCAM mAb, instead of by intracellular staining of cytokeratins (CK). The EpCAM double-positive selection/labeling method allows enumeration of intact CTC, maintenance of cellular integrity, and the concomitant performance of a CTC viability test. The combination of the fine-tuned CTC enrichment process and the cytometric multicolor analysis resulted in a linear relationship between the output cell count and the input cell number from zero to hundreds of cells. In particular, a satisfactory signal/noise ratio was obtained by gate-exclusion of leukocyte signals using an anti-CD45 mAb. The entire process had little influence on the viability of the spiked lung cancer cell PC-9. Measured PC-9 and breast cancer MCF-7 cells bearing EpCAM-MicroBeads, APC-conjugated EpCAM mAb, and the DNA staining dye SYTO9 grew normally, demonstrating the potential usefulness of the collected samples for further studies. This intact CTC enumeration and analysis procedure (iCeap) would be of great benefit to clinicians by providing them with rapid stratification of antitumor therapy, and to basic researchers by permitting further molecular and cellular characterization of CTC.

Using detection of survivin-expressing circulating tumor cells in peripheral blood to predict tumor recurrence following curative resection of gastric cancer

BACKGROUND AND OBJECTIVES

The present study was designed to investigate the clinicopathological role of survivin-expressing circulating tumor cells (CTCs) and to determine whether the presence of survivin-expressing CTCs is an independent predictor of tumor recurrence following curative resection of gastric cancer.

METHODS

This study included 98 patients who underwent potentially curative resection. Reverse transcription polymerase chain reaction enzyme linked immunosorbent assay (RT-PCR ELISA) was used to measure survivin mRNA in peripheral blood.

RESULTS

Of the 98 patients studied, 45 (45.9%) were positive for survivin mRNA. Survivin mRNA expression correlated with Lauren classification (P < 0.001), pathological tumor (pT) stage (P < 0.001), pathological tumor node metastasis (pTNM) stage (P = 0.009), and degree of differentiation (P = 0.001). The pTNM stage and the status of survivin mRNA were independent prognostic factors of disease-free survival (P = 0.007 and <0.001, respectively).

CONCLUSIONS

The detection of CTCs expressing survivin mRNA could be a good clinical biomarker used to predict the prognosis of patients with curatively resected gastric cancer.

Microsystems for the capture of low-abundance cells

Efficient selection and enumeration of low-abundance biological cells are highly important in a variety of applications. For example, the clinical utility of circulating tumor cells (CTCs) in peripheral blood is recognized as a viable biomarker for the management of various cancers, in which the clinically relevant number of CTCs per 7.5 ml of blood is two to five. Although there are several methods for isolating rare cells from a variety of heterogeneous samples, such as immunomagnetic-assisted cell sorting and fluorescence-activated cell sorting, they are fraught with challenges. Microsystem-based technologies are providing new opportunities for selecting and isolating rare cells from complex, heterogeneous samples. Such approaches involve reductions in target-cell loss, process automation, and minimization of contamination issues. In this review, we introduce different application areas requiring rare cell analysis, conventional techniques for their selection, and finally microsystem approaches for low-abundance-cell isolation and enumeration.

Survivin gene levels in the peripheral blood of patients with gastric cancer independently predict survival

BACKGROUND

The detection of circulating tumor cells (CTC) is considered a promising tool for improving risk stratification in patients with solid tumors. We investigated on whether the expression of CTC related genes adds any prognostic power to the TNM staging system in patients with gastric carcinoma.

METHODS

Seventy patients with TNM stage I to IV gastric carcinoma were retrospectively enrolled. Peripheral blood samples were tested by means of quantitative real time PCR (qrtPCR) for the expression of four CTC related genes: carcinoembryonic antigen (CEA), cytokeratin-19 (CK19), vascular endothelial growth factor (VEGF) and Survivin (BIRC5).

RESULTS

Gene expression of Survivin, CK19, CEA and VEGF was higher than in normal controls in 98.6%, 97.1%, 42.9% and 38.6% of cases, respectively, suggesting a potential diagnostic value of both Survivin and CK19. At multivariable survival analysis, TNM staging and Survivin mRNA levels were retained as independent prognostic factors, demonstrating that Survivin expression in the peripheral blood adds prognostic information to the TNM system. In contrast with previously published data, the transcript abundance of CEA, CK19 and VEGF was not associated with patients' clinical outcome.

CONCLUSIONS

Gene expression levels of Survivin add significant prognostic value to the current TNM staging system. The validation of these findings in larger prospective and multicentric series might lead to the implementation of this biomarker in the routine clinical setting in order to optimize risk stratification and ultimately personalize the therapeutic management of these patients.

Isolation of tumor cells using size and deformation

The isolation and analysis of circulating tumor cells (CTCs) from blood are the subject of intense research. Although tests to detect metastasis on a molecular level are available, progress has been hampered by a lack of tumor-specific markers and predictable DNA abnormalities. The main challenge in this endeavor is the small number of available cells of interest, 1-2 per mL in whole blood. We have designed a micromachined device to fractionate whole blood using physical means to enrich for and/or isolate rare cells from peripheral circulation. It has arrays of four successively narrower channels, each consisting of a two-dimensional array of columns. Current devices have channels ranging in width from 20 to 5 microm, and in depth from 20 to 5 microm. Several optimizations resulting in the fabrication of a total of 10 derivative devices have been carried out; only two types are used in this study. Both have increasingly narrower gap widths between the columns along the flow axis with 20, 15, 10, and 5 microm spacing all on one device. The first 20 microm wide segment disperses the cell suspension and creates an evenly distributed flow over the entire device, whereas the others were designed to retain increasingly smaller cells. The channel depth is constant across the entire device, the first type was 10 microm deep and the second type is 20 microm deep. When cells from each of eight tumor cell lines were loaded into the device, all cancerous cells were isolated. In mixing experiments using human whole blood, we were able to fractionate cancer cells without interference from the blood cells. Additionally, either intact cells, or DNA, could be extracted for molecular analysis. The ultimate goal of this work is to characterize the cells on the molecular level to provide non-invasive methods to monitor patients, stage disease, and assess treatment efficacy. Furthermore, this work will use gene expression profiles to gain insights into metastasis.

Molecular characterization of circulating tumor cells in large quantities of contaminating leukocytes by a multiplex real-time PCR

Detection of circulating tumor cells (CTCs) in whole blood from metastatic cancer patients by the CellSearch CTC Test (Veridex LLC, Warren, NJ, USA) has been shown to have clinical relevance. In addition to enumeration, there is great interest in molecular characterization of these CTCs. We aimed to establish a robust method to perform mRNA expression analysis of multiple genes by a real-time reverse transcriptase (RT)-PCR on small numbers of CTCs enriched from whole blood by the CellSearch system. Despite the 4 log depletion of leukocytes after CellSearch enrichment, the CTC-enriched fractions still contained leukocytes, in particular B-lymphocytes, which severely interfered with our CTC-specific gene expression profiling. After extensive washing and leukocyte-specific depletion by anti-CD45 coated magnetic beads prior to CellSearch enrichment, the number of leukocytes present in the enriched fraction was still high (range 60-929). However, by using a set of genes with no or minor expression by leukocytes, we succeeded to perform quantitative gene expression profiling specific for as little as one breast cancer CTC present in a CTC-enriched environment typically containing over 800 contaminating leukocytes. Our method allows molecular characterization specific for as little as one CTC, and can be used to expand the understanding of the biology of metastasis and, potentially, to improve patient management.