Recent advances and prospects in the isolation by size of epithelial tumor cells (ISET) methodology

Circulating Tumor Cells as a Promising Tool for Early Detection of Hepatocellular Carcinoma

Liver cancer is a significant contributor to the cancer burden, and its incidence rates have recently increased in almost all countries. Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer and is the second leading cause of cancer-related deaths worldwide. Because of the late diagnosis and lack of efficient therapeutic modality for advanced stages of HCC, the death rate continues to increase by ~2-3% per year. Circulating tumor cells (CTCs) are promising tools for early diagnosis, precise prognosis, and follow-up of therapeutic responses. They can be considered to be an innovative biomarker for the early detection of tumors and targeted molecular therapy. In this review, we briefly discuss the novel materials and technologies applied for the practical isolation and detection of CTCs in HCC. Also, the clinical value of CTC detection in HCC is highlighted.

Assessment of Different Circulating Tumor Cell Platforms for Uveal Melanoma: Potential Impact for Future Routine Clinical Practice

Liquid biopsy and circulating tumor cell (CTC) screening has gained interest over the last two decades for detecting almost all solid malignancies. To date, the major limitation in terms of the applicability of CTC screening in daily clinical practice is the lack of reproducibility due to the high number of platforms available that use various technologies (e.g., label-dependent versus label-free detection). Only a few studies have compared different CTC platforms. The aim of this study was to compare the efficiency of four commercially available CTC platforms (Vortex (VTX-1), ClearCell FX, ISET, and Cellsearch) for the detection and identification of uveal melanoma cells (OMM 2.3 cell line). Tumor cells were seeded in RPMI medium and venous blood from healthy donors, and then processed similarly using these four platforms. Melan-A immunochemistry was performed to identify tumor cells, except when the Cellsearch device was used (automated identification). The mean overall recovery rates (with mean recovered cells) were 39.2% (19.92), 22.2% (11.31), 8.9% (4.85), and 1.1% (0.20) for the ISET, Vortex (VTX-1), ClearCell FX, and CellSearch platforms, respectively. Although paramount, the recovery rate is not sufficient to assess a CTC platform. Other parameters, such as the purpose for using a platform (diagnosis, genetics, drug sensitivity, or patient-derived xenograft models), reproducibility, purity, user-friendliness, cost-effectiveness, and ergonomics, should also be considered before they can be used in daily clinical practice and are discussed in this article.

Highly efficient and robust π-FISH rainbow for multiplexed in situ detection of diverse biomolecules

In the unprecedented single-cell sequencing and spatial multiomics era of biology, fluorescence in situ hybridization (FISH) technologies with higher sensitivity and robustness, especially for detecting short RNAs and other biomolecules, are greatly desired. Here, we develop the robust multiplex π-FISH rainbow method to detect diverse biomolecules (DNA, RNA, proteins, and neurotransmitters) individually or simultaneously with high efficiency. This versatile method is successfully applied to detect gene expression in different species, from microorganisms to plants and animals. Furthermore, we delineate the landscape of diverse neuron subclusters by decoding the spatial distribution of 21 marker genes via only two rounds of hybridization. Significantly, we combine π-FISH rainbow with hybridization chain reaction to develop π-FISH+ technology for short nucleic acid fragments, such as microRNA and prostate cancer anti-androgen therapy-resistant marker ARV7 splicing variant in circulating tumour cells from patients. Our study provides a robust biomolecule in situ detection technology for spatial multiomics investigation and clinical diagnosis.

Comprehensive optimization of urinary exfoliated tumor cells tests in bladder cancer with a promising microfluidic platform

BACKGROUND

Enrichment of urinary exfoliated tumor cells (UETCs) is a noninvasive way of bladder cancer diagnosis, but the lack of specific capture and identification of tumor cells from the urine remains a limitation that impedes the development of liquid biopsy.

METHODS

The CytoBot^® 2000, a novel circulating cell isolation and enrichment platform, was used for UETCs isolation after comprehensive optimization. The commercial cell lines of bladder cancer were used in spiking assay for cell recovery test. The flow cytometry and immunofluorescent staining assays were performed for expression validation of capture target and identification markers. The performance of optimized platform was validated by 159 clinical samples and analyzed using receiver operator characteristic curve.

RESULTS

The chip that had a pore diameter of 15*20 μm could reduce the background residues while maintaining a higher cell recovery rate. We found that the cell capture ability of chip significantly improved after anti-EpCam antibody encapsulation, but not with T4L6FM1. In identification system optimization, the spiking assay and validation of clinical sample showed that the performance of CK20 and DBC-1 were better that pan-CK in tumor cell identification, in addition, the staining quality is more legible with CK20.

CONCLUSION

The optimized capture chip is more specific for UETCs isolation. CK20 and DBC-1 are both sensitive biomarkers of UETCs in bladder cancer diagnosis. The performance of this optimized platform is excellent in clinical test that improves the accuracy of urine cell testing and provides a new alternative for the clinical application of BLCA liquid biopsy assessment.

Recent advances in micro-/nanostructure array integrated microfluidic devices for efficient separation of circulating tumor cells

Circulating tumor cells (CTCs) released from the primary tumor to peripheral blood are promising targets for liquid biopsies. Their biological information is vital for early cancer detection, efficacy assessment, and prognostic monitoring. Despite the tremendous clinical applications of CTCs, development of effective separation techniques are still demanding. Traditional separation methods usually use batch processing for enrichment, which inevitably destroy cell integrity and affect the complete information acquisition. Considering the rarity and heterogeneity of CTCs, it is urgent to develop effective separation methods. Microfluidic chips with precise fluid control at the micron level are promising devices for CTC separation. Their further combination with micro-/nanostructure arrays adds more biomolecule binding sites and exhibit unique fluid barrier effect, which significantly improve the CTC capture efficiency, purity, and sensitivity. This review summarized the recent advances in micro-/nanostructure array integrated microfluidic devices for CTC separation, including microrods, nanowires, and 3D micro-/nanostructures. The mechanisms by which these structures contribute to improved capture efficiency are discussed. Two major categories of separation methods, based on the physical and biological properties of CTCs, are discussed separately. Physical separation includes the design and preparation of micro-/nanostructure arrays, while chemical separation additionally involves the selection and modification of specific capture probes. These emerging technologies are expected to become powerful tools for disease diagnosis in the future.

Bioplatforms in liquid biopsy: advances in the techniques for isolation, characterization and clinical applications

Tissue biopsy analysis has conventionally been the gold standard for cancer prognosis, diagnosis and prediction of responses/resistances to treatments. The existing biopsy procedures used in clinical practice are, however, invasive, painful and often associated with pitfalls like poor recovery of tumor cells and infeasibility for repetition in single patients. To circumvent these limitations, alternative non-invasive, rapid and economical, yet sturdy, consistent and dependable, biopsy techniques are required. Liquid biopsy is an emerging technology that fulfills these criteria and potentially much more in terms of subject-specific real-time monitoring of cancer progression, determination of tumor heterogeneity and treatment responses, and specific identification of the type and stages of cancers. The present review first briefly revisits the state-of-the-art technique of liquid biopsy and then proceeds to address in detail, the advances in the potential clinical applications of four major biological agencies present in liquid biopsy samples (circulating tumor DNA (ctDNA), circulating tumor cells (CTCs), exosomes and tumor-educated platelets (TEPs)). Finally, the authors conclude with the limitations that need to be addressed in order for liquid biopsy to effectively replace the conventional invasive biopsy methods in the clinical settings.

Membranes for the life sciences and their future roles in medicine

Since the global outbreak of COVID-19, membrane technology for clinical treatments, including extracorporeal membrane oxygenation (ECMO) and protective masks and clothing, has attracted intense research attention for its irreplaceable abilities. Membrane research and applications are now playing an increasingly important role in various fields of life science. In addition to intrinsic properties such as size sieving, dissolution and diffusion, membranes are often endowed with additional functions as cell scaffolds, catalysts or sensors to satisfy the specific requirements of different clinical applications. In this review, we will introduce and discuss state-of-the-art membranes and their respective functions in four typical areas of life science: artificial organs, tissue engineering, in vitro blood diagnosis and medical support. Emphasis will be given to the description of certain specific functions required of membranes in each field to provide guidance for the selection and fabrication of the membrane material. The advantages and disadvantages of these membranes have been compared to indicate further development directions for different clinical applications. Finally, we propose challenges and outlooks for future development.

Dielectrophoresis-Based SERS Sensors for the Detection of Cancer Cells in Microfluidic Chips

The detection of freely circulating cancer cells (CTCs) is one of the greatest challenges of modern medical diagnostics. For several years, there has been increased attention on the use of surface-enhanced Raman spectroscopy (SERS) for the detection of CTCs. SERS is a non-destructive, accurate and precise technique, and the use of special SERS platforms even enables the amplification of weak signals from biological objects. In the current study, we demonstrate the unique arrangement of the SERS technique combined with the deposition of CTCs cells on the surface of the SERS platform via a dielectrophoretic effect. The appropriate frequencies of an alternating electric field and a selected shape of the electric field can result in the efficient deposition of CTCs on the SERS platform. The geometry of the microfluidic chip, the type of the cancer cells and the positive dielectrophoretic phenomenon resulted in the trapping of CTCs on the surface of the SERS platform. We presented results for two type of breast cancer cells, MCF-7 and MDA-MB-231, deposited from the 0.1 PBS solution. The limit of detection (LOD) is 20 cells/mL, which reflects the clinical potential and usefulness of the developed approach. We also provide a proof-of-concept for these CTCs deposited on the SERS platform from blood plasma.

Embryonated Chicken Tumor Xenografts Derived from Circulating Tumor Cells as a Relevant Model to Study Metastatic Dissemination: A Proof of Concept

Simple Summary

Circulating Tumor Cells (CTCs) are heterogeneous and rare in the bloodstream, but responsible for cancer metastasis. Their in vitro or in vivo expansion remains a major challenge. The chicken Chorioallantoic Membrane (CAM) assay has proven to be a reliable alternative to the murine model, notably for tumor xenografts. We have developed a promising model of CTC-derived xenografts in the chicken CAM and demonstrated the feasibility of Next Generation Sequencing (NGS) analysis in this assay, with a genomic concordance between the in ovo tumor and the original patient’s tumor. We also evidenced metastatic dissemination from the xenograft in the chicken embryo’s distant organs. Further characterization of the in ovo tumors and metastases may provide new insights into the mechanisms of tumor dissemination. The development of a xenograft from a given patient’s CTCs, in a time frame compatible with managing the patient’s treatment, could also be a step forward towards personalized medicine.

Abstract

Patient-Derived Xenografts (PDXs) in the Chorioallantoic Membrane (CAM) are a representative model for studying human tumors. Circulating Tumor Cells (CTCs) are involved in cancer dissemination and treatment resistance mechanisms. To facilitate research and deep analysis of these few cells, significant efforts were made to expand them. We evaluated here whether the isolation of fresh CTCs from patients with metastatic cancers could provide a reliable tumor model after a CAM xenograft. We enrolled 35 patients, with breast, prostate, or lung metastatic cancers. We performed microfluidic-based CTC enrichment. After 48–72 h of culture, the CTCs were engrafted onto the CAM of embryonated chicken eggs at day 9 of embryonic development (EDD9). The tumors were resected 9 days after engraftment and histopathological, immunochemical, and genomic analyses were performed. We obtained in ovo tumors for 61% of the patients. Dedifferentiated small tumors with spindle-shaped cells were observed. The epithelial-to-mesenchymal transition of CTCs could explain this phenotype. Beyond the feasibility of NGS in this model, we have highlighted a genomic concordance between the in ovo tumor and the original patient’s tumor for constitutional polymorphism and somatic alteration in one patient. Alu DNA sequences were detected in the chicken embryo’s distant organs, supporting the idea of dedifferentiated cells with aggressive behavior. To our knowledge, we performed the first chicken CAM CTC-derived xenografts with NGS analysis and evidence of CTC dissemination in the chicken embryo.

Significance of circulating tumor cells in the portal vein regarding metastases and vascular invasion in hepatocellular carcinoma patients

BACKGROUND

Vascular invasion is an important risk factor of poor prognosis in hepatocellular carcinoma (HCC) patients. The detection of circulating tumor cells (CTCs) in the blood is direct evidence of tumor presence. There are few reports on CTCs and metastasis and vascular invasion of HCC. The purpose of this study was to analyze the significance of CTCs in the portal vein regarding metastases and vascular invasion in HCC patients.

METHODS

A total of 104 HCC patients diagnosed and treated in Zhengzhou University People's Hospital were enrolled. Surgery was performed in 60 individuals. Portal vein blood samples were collected before treatment for CTCs detection. We used the isolation by size of epithelial tumor cells (ISET) and fluorescence in situ hybridization (FISH) to enrich and classify CTCs from blood samples. The patients were divided into metastasis and nonmetastasis groups according to the metastasis status before treatment. Differences in clinical indicators such as alpha-fetoprotein (AFP) levels, tumor size, CTCs count, and macrovascular tumor thrombus between the two groups were analyzed as well as the associations of CTCs count with the above indicators. For individuals with postoperative pathology, the relationship between CTCs counts and microvascular invasion (MVI) was analyzed.

RESULTS

The amounts of portal vein CTCs were higher in patients with metastases compared with the nonmetastases group (20 vs. 7; z=3.795; P<0.001). Multivariate logistic regression analysis showed that the CTC count was a risk factor for HCC metastasis [odds ratio (OR) =1.044; 95% CI: 1.011-1.079]. The sensitivity and specificity of CTC count in predicting HCC metastasis were 82.93% and 52.38%, respectively. CTC count was significantly correlated with tumor size (rs=0.308; P=0.001), vascular invasion (z=4.211; P<0.001), and MVI (z=12.763; P=0.002). A threshold CTC count of seven showed the most significant power for predicting metastasis.

CONCLUSIONS

Vascular invasion positivity was closely related to HCC metastasis. Portal vein CTC count before treatment was correlated with vascular invasion and could be considered one of the factors affecting HCC metastasis. However, the ability of CTC count was limited in predicting HCC metastasis due to insufficient specificity.

Digital Pathology Slides-based Measurement of Tumor Cells and Lymphocytes Within Cytology Samples Supports the Relevance of the Separation by Size of Nonhematological Tumor and Hematological Nontumor Cells in Liquid Biopsies

Filtration by size is one method used to study circulating tumor cells in blood samples. Filtration-migration ability is highly dependent of the size of cell nucleus. This implies to search for the appropriate nucleus size able to separate between hematological nucleated and nonhematological nucleated blood cells to maximize circulating tumor cell isolation. Digitalized cytology slides [May-Grünwald Giemsa (MGG) stained and immunocytochemistry (ICC) slides] from various cancer metastases served for manual measurements of nuclei about tumor cells and adjacent lymphocytes to determine the diameters the more able to separate between tumor cells and lymphocytes. Among 2022 cells analyzed (1067 tumor cells and 955 lymphocytes) on MGG stained slides, the mean diameter of tumor cells nuclei was 14.77 µm whereas the mean diameter of lymphocytic nuclei was 6.47 µm (P<0.001). In ICC slides, about 6583 cells (4753 tumor cells and 1830 lymphocytes), the mean diameter of tumor cells nuclei was 9.28 µm whereas the mean diameter of lymphocytic nuclei was 4.95 µm (P<0.001). Areas under the receiver operating characteristic curves analyses concluded that diameters of 9.37 µm and 6 µm separated the best between tumor cells and lymphocytes in MGG and ICC slides, respectively. Measuring manually the diameters of the smallest tumor cells in ICC slides, we established more than 99% of tumor cells had diameters superior to 8 µm. The sizes differences between tumor cells and lymphocytes support the relevance of the filtration by size to isolate blood circulating nonhematological tumor cells. The existence of small tumor cells with sizes overlapping with those of lymphocytes is worth to optimize the threshold to separate between tumor cells and hematological cells.

Microfluidics for label-free sorting of rare circulating tumor cells

A review discussing the working principles and performances of label-free CTC sorting methods.

CTC analysis: an update on technological progress

There is a growing need for a more accurate, real-time assessment of tumor status and the probability of metastasis, relapse, or response to treatment. Conventional means of assessment include imaging and tissue biopsies that can be highly invasive, may not provide complete information of the disease's heterogeneity, and not ideal for repeat analysis. Therefore, a less-invasive means of acquiring similar information at greater time points is necessary. Liquid biopsies are samples of a patients' peripheral blood and hold potential of addressing these criteria. Ongoing research has revealed that a tumor can release circulating cells, genetic materials (DNA or RNA), and exosomes into circulation. These potential biomarkers can be captured in a liquid biopsy and analyzed to determine disease status. To achieve these goals, numerous technologies have been developed. In this review, we discuss both prominent and newly developed technologies for circulating tumor cell capture and analysis and their clinical impact.

Biophysical Insights on the Enrichment of Cancer Cells from Whole Blood by (Affinity) Filtration

Circulating tumor cells (CTCs) play a key role during the metastatic process of human cancers and their reliable detection and characterization could enable new and effective ways of cancer diagnosis, monitoring and treatment. However, due to their ultralow concentration in patient blood, the CTCs must first be enriched before such analysis can be performed. Classical microfiltration is an important and widely used method for the mechanical enrichment of CTCs. This method exploits that CTCs are generally larger than the accompanying blood cells, however, does not differentiate the cells in other ways. In an affinity filtration, selectivity is added by functionalizing the membrane with specific antibodies against a CTC-characteristic surface protein such as the epithelial cell adhesion molecule (EpCAM). A common shortcoming of both filtration approaches is that there is still a poor understanding of the enrichment process and the systems developed so far are frequently operated under non-optimized conditions. To address this, systematic filtration experiments are performed in this work using the EpCAM+ cell line MCF-7 as CTC-model and standard track-etched membranes modified with or without antibodies against EpCAM. The influences of the key filtration parameters time and applied pressure are studied and it is found that in all cases the extent of cell recovery is limited by a lysis process which occurs on the membrane surface. Counterintuitively, it is found that filtration at rather high pressures is advantageous to ensure high recovery rates. To describe the pressure-induced lysis process a biophysical model is developed. This model allows the determination of optimum filtration conditions to achieve both high cancer cell recovery and large blood sample throughput. It is demonstrated that this way practically 100% of spiked cancer cells can be recovered from milliliters of undiluted whole blood within seconds.

Prognostic value of pre- and post-operative circulating tumor cells detection in colorectal cancer patients treated with curative resection: a prospective cohort study based on ISET device

Background

Circulating tumor cells (CTCs) have been regarded as a promising biomarker for colorectal cancer (CRC); however, the prognostic value of post-operative (op) CTCs is still unclear. This study aimed to compare the recurrence prediction value of pre- and post-op CTCs in CRC patients treated with curative resection.

Patients and methods

Consecutive CRC patients treated with curative resection from January 2014 to March 2015 were identified. CTCs from 2.5 mL peripheral blood were enumerated with an ISETdevice-CTCBIOPSY^® before and after surgery. Based on the status of pre- and post-op CTCs, the included patients were grouped into four cohorts: pre- and post-op CTCs−, pre-op CTCs− but post-op CTCs+, pre-op CTCs+ but post-op CTCs−, and pre- and post-op CTCs+. The 3-year recurrence-free survival (RFS) rate of patients was analyzed.

Results

A total of 138 patients (79 [57.2%] male; median age=62 [43–75] years) were enrolled. Patients with pre-op CTCs− had a 19.2% higher 3-year RFS rate (86.2%) than the combined cohorts with pre-op CTCs+ (67.0%) (P=0.038). Patients with post-op CTCs+ had aa 25.6% lower 3-year RFS rate (57.1%) than the combined cohorts with post-op CTCs− (82.7%) (P=0.001). Moreover, patients with pre- and post-op CTCs+ had a 25.1% lower 3-year RFS rate (53.8%) than patients with pre-op CTCs+ but post-op CTCs− (78.9%) (P=0.004). Multivariate analyses confirmed that post-op CTCs+ (HR=2.82, 95% CI=1.39–5.75, P=0.004), but not but pre-op CTCs+ (HR=2.17, 95% CI=0.75–6.31, P=0.153), was independently associated with shorter 3-year RFS rate.

Conclusion

Post-op CTCs+, but not pre-op CTCs+, is an independent indicator of poor prognosis for CRC patients treated with curative resection. Patients with post-op CTCs+ have a higher risk of recurrence those with pre-op CTCs+. Evaluation of post-op, rather than pre-op, CTCs is warranted.

A Label Free Disposable Device for Rapid Isolation of Rare Tumor Cells from Blood by Ultrasounds

The use of blood samples as liquid biopsy is a label-free method for cancer diagnosis that offers benefits over traditional invasive biopsy techniques. Cell sorting by acoustic waves offers a means to separate rare cells from blood samples based on their physical properties in a label-free, contactless and biocompatible manner. Herein, we describe a flow-through separation approach that provides an efficient separation of tumor cells (TCs) from white blood cells (WBCs) in a microfluidic device, “THINUS-Chip” (Thin-Ultrasonic-Separator-Chip), actuated by ultrasounds. We introduce for the first time the concept of plate acoustic waves (PAW) applied to acoustophoresis as a new strategy. It lies in the geometrical chip design: different to other microseparators based on either bulk acoustic waves (BAW) or surface waves (SAW, SSAW and tSAW), it allows the use of polymeric materials without restrictions in the frequency of work. We demonstrate its ability to perform high-throughput isolation of TCs from WBCs, allowing a recovery rate of 84% ± 8% of TCs with a purity higher than 80% and combined viability of 85% at a flow rate of 80 μL/min (4.8 mL/h). The THINUS-Chip performs cell fractionation with low-cost manufacturing processes, opening the door to possible easy printing fabrication.

Detection of circulating tumor cells in cervical cancer using a conditionally replicative adenovirus targeting telomerase-positive cells

Circulating tumor cells (CTC) are newly discovered biomarkers of cancers. Although many systems detect CTC, a gold standard has not yet been established. We analyzed CTC in uterine cervical cancer patients using an advanced version of conditionally replicative adenovirus targeting telomerase-positive cells, which was enabled to infect coxsackievirus-adenovirus receptor-negative cells and to reduce false-positive signals in myeloid cells. Blood samples from cervical cancer patients were hemolyzed and infected with the virus and then labeled with fluorescent anti-CD45 and anti-pan cytokeratin antibodies. GFP (+)/CD45 (-) cells were isolated and subjected to whole-genome amplification followed by polymerase chain reaction analysis of human papillomavirus (HPV) DNA. CTC were detected in 6 of 23 patients with cervical cancers (26.0%). Expression of CTC did not correlate with the stage of cancer or other clinicopathological factors. In 5 of the 6 CTC-positive cases, the same subtype of HPV DNA as that of the corresponding primary lesion was detected, indicating that the CTC originated from HPV-infected cancer cells. These CTC were all negative for cytokeratins. The CTC detected by our system were genetically confirmed. CTC derived from uterine cervical cancers had lost epithelial characteristics, indicating that epithelial marker-dependent systems do not have the capacity to detect these cells in cervical cancer patients.

Detection of FAM172A expressed in circulating tumor cells is a feasible method to predict high-risk subgroups of colorectal cancer

Previous studies used to enumerate circulating tumor cells to predict prognosis and therapeutic effect of colorectal cancer. However, increasing studies have shown that only circulating tumor cells enumeration was not enough to reflect the heterogeneous condition of tumor. In this study, we classified different metastatic-potential circulating tumor cells from colorectal cancer patients and measured FAM172A expression in circulating tumor cells to improve accuracy of clinical diagnosis and treatment of colorectal cancer. Blood samples were collected from 45 primary colorectal cancer patients. Circulating tumor cells were enriched by blood filtration using isolation by size of epithelial tumor cells, and in situ hybridization with RNA method was used to identify and discriminate subgroups of circulating tumor cells. Afterwards, FAM172A expression in individual circulating tumor cells was measured. Three circulating tumor cell subgroups (epithelial/biophenotypic/mesenchymal circulating tumor cells) were identified using epithelial-mesenchymal transition markers. In our research, mesenchymal circulating tumor cells significantly increased along with tumor progression, development of distant metastasis, and vascular invasion. Furthermore, FAM172A expression rate in mesenchymal circulating tumor cells was significantly higher than that in epithelial circulating tumor cells, which suggested that FAM172A may correlate with malignant degree of tumor. This hypothesis was further verified by FAM172A expression in mesenchymal circulating tumor cells, which was strictly related to tumor aggressiveness factors. Mesenchymal circulating tumor cells and FAM172A detection may predict highrisk stage II colorectal cancer. Our research proved that circulating tumor cells were feasible surrogate samples to detect gene expression and could serve as a predictive biomarker for tumor evaluation.

High-Throughput Selective Capture of Single Circulating Tumor Cells by Dielectrophoresis at a Wireless Electrode Array

We demonstrate continuous high-throughput selective capture of circulating tumor cells by dielectrophoresis at arrays of wireless electrodes (bipolar electrodes, BPEs). The use of BPEs removes the requirement of ohmic contact to individual array elements, thus enabling otherwise unattainable device formats. Capacitive charging of the electrical double layer at opposing ends of each BPE allows an AC electric field to be transmitted across the entire device. Here, two such designs are described and evaluated. In the first design, BPEs interconnect parallel microchannels. Pockets extruding from either side of the microchannels volumetrically control the number of cells captured at each BPE tip and enhance trapping. High-fidelity single-cell capture was achieved when the pocket dimensions were matched to those of the cells. A second, open design allows many non-targeted cells to pass through. These devices enable high-throughput capture of rare cells and single-cell analysis.

FAM172A expression in circulating tumor cells for prediction of high-risk subgroups of colorectal cancer

Objectives

Previous studies used enumerated circulating tumor cells (CTCs) to predict prognosis and therapeutic effect in several types of cancers. However, increasing evidence showed that only enumerated CTCs were not enough to reflect the heterogeneity of tumors. Therefore, we classified different metastasis potentials of CTCs from colorectal cancer (CRC) patients to improve the accuracy of prognosis by CTCs.

Methods

Blood samples were collected from 45 primary CRC patients. CTCs were enriched by blood filtration, and the RNA in situ hybridization method was used to identify and discriminate subgroups of CTCs. Later, FAM172A expression in individual CTCs was measured.

Results

Three CTC subgroups (epithelial/biophenotypic/mesenchymal CTCs) were identified using epithelial–mesenchymal transition markers. In our research, mesenchymal CTCs significantly increased along with tumor progression, including developing distant metastasis and vascular invasion. Furthermore, FAM172A expression rate in mesenchymal CTCs was significantly higher than that in epithelial CTCs, which suggested that FAM172A may correlate with tumor malignancy. This hypothesis was further verified by FAM172A expression in mesenchymal CTCs strictly related to tumor aggressiveness factors. Finally, we revealed that mesenchymal CTCs and FAM172A expression may predict high-risk subgroups in stage II CRC.

Conclusion

Our research proved that CTCs could serve as feasible surrogate samples to detect gene expression as a predictive biomarker for tumor evaluation.

A New Size-based Platform for Circulating Tumor Cell Detection in Colorectal Cancer Patients

BACKGROUND

Circulating tumor cells (CTCs) might play a significant role in cancer progression and metastasis. However, the ability to detect CTCs is limited, especially in cells undergoing epithelial-mesenchymal transition. In this study, we evaluated a new size-based CTC detection platform and its clinical efficacy in colorectal cancer.

PATIENTS AND METHODS

Blood samples were obtained from 76 patients with colorectal cancer and 20 healthy control subjects for CTC analysis. CTCs were enriched using a high-density microporous chip filter and were detected using a 4-color staining protocol including 4',6-diamidino-2-phenylindole (DAPI) for nucleated cells, CD45 monoclonal antibody (mAb) as a leukocyte marker, and epithelial cell adhesion molecule (EpCAM) mAb or cytokeratin (CK) mAb as an epithelial cell marker. CTC positivity was defined as DAPI-positive (DAPI⁺)/CD45^-/EpCAM⁺ or CK⁺ cells and clinical outcomes of patients were analyzed according to CTC counts.

RESULTS

CTCs were detected in 50 patients using this size-based filtration platform. CTC⁺ patients were more frequently identified with a high level of carcinoembryonic antigen and advanced stage cancer (P = .038 and P = .017, respectively). CTC counts for patients with stage IV cancer (12.47 ± 24.00) were significantly higher than those for patients with cancers that were stage I to III (2.84 ± 5.29; P = .005) and healthy control subjects (0.25 ± 0.55; P < .001). In addition, progression-free survival tended to be lower in CTC⁺ patients compared with CTC^- patients (P = .092). In patients with stage I to III cancer, recurrence occurred only in CTC⁺ patients.

CONCLUSION

CTC positivity was found to correlate with clinical features of colorectal cancer patients. Our results suggest that this new size-based platform has potential for determining prognosis and therapeutic response in colorectal cancer patients.

Circulating Tumor Cell and Cell-free Circulating Tumor DNA in Lung Cancer

Circulating tumor cells (CTCs) are tumor cells that are separated from the primary site or metastatic lesion and disseminate in blood circulation. CTCs are considered to be part of the long process of cancer metastasis. As a 'liquid biopsy', CTC molecular examination and investigation of single cancer cells create an important opportunity for providing an understanding of cancer biology and the process of metastasis. In the last decade, we have seen dramatic development in defining the role of CTCs in lung cancer in terms of diagnosis, genomic alteration determination, treatment response and, finally, prognosis prediction. The aims of this review are to understand the basic biology and to review methods of detection of CTCs that apply to the various types of solid tumor. Furthermore, we explored clinical applications, including treatment monitoring to anticipate therapy resistance as well as biomarker analysis, in the context of lung cancer. We also explored the potential use of cell-free circulating tumor DNA (ctDNA) in the genomic alteration analysis of lung cancer.

High expression of TRF2, SOX10, and CD10 in circulating tumor microemboli detected in metastatic melanoma patients. A potential impact for the assessment of disease aggressiveness

Circulating tumors cells (CTCs) can be detected in the blood of metastatic melanoma patients (MMPs) both as isolated circulating tumor cells (iCTCs) and circulating tumor microemboli (CTMs), but their clinical significance remains unknown. The aim of this work was to evaluate the prognostic impact in metastatic cutaneous melanoma of CTMs and iCTCs identified by a cytomorphological approach using the isolation by size of tumor cell (ISET) method. We characterized the phenotype of CTCs using anti-PS100, anti-SOX10, anti-CD10, and anti-TRF2 antibodies. 128 MMPs and 37 control healthy individuals with benign nevi were included in this study. Results were compared to the follow-up of patients. 109/128 (85%) MMPs showed CTCs, 44/128 (34%) with 2 to 6 CTMs and 65/128 (51%) with 4 to 9 iCTCs. PS100 expression was homogeneous in iCTCs and heterogeneous in CTMs. SOX10, CD10, and TRF2 were mainly expressed in CTMs. None of the control subjects demonstrated circulating malignant tumor cells. Overall survival was significantly decreased in patients with CTMs, independently of the therapeutic strategies. In conclusion, the presence of CTMs is an independent predictor of shorter survival from the time of diagnosis of MMPs.

Do circulating tumor cells, exosomes, and circulating tumor nucleic acids have clinical utility? A report of the association for molecular pathology

Diagnosing and screening for tumors through noninvasive means represent an important paradigm shift in precision medicine. In contrast to tissue biopsy, detection of circulating tumor cells (CTCs) and circulating tumor nucleic acids provides a minimally invasive method for predictive and prognostic marker detection. This allows early and serial assessment of metastatic disease, including follow-up during remission, characterization of treatment effects, and clonal evolution. Isolation and characterization of CTCs and circulating tumor DNA (ctDNA) are likely to improve cancer diagnosis, treatment, and minimal residual disease monitoring. However, more trials are required to validate the clinical utility of precise molecular markers for a variety of tumor types. This review focuses on the clinical utility of CTCs and ctDNA testing in patients with solid tumors, including somatic and epigenetic alterations that can be detected. A comparison of methods used to isolate and detect CTCs and some of the intricacies of the characterization of the ctDNA are also provided.

Notes for developing a molecular test for the full characterization of circulating tumor cells

The proved association between the circulating tumor cell (CTC) levels and the patients' survival parameters has been growing interest to investigate the molecular profile of these neoplastic cells among which hide out precursors capable of initiating a new distant metastatic lesion. The full characterization of the tumor cells in peripheral blood of cancer patients is expected to be of help for understanding and (prospectively) for counteracting the metastatic process. The major hitch that is hampering the successful gaining of this result is the lack of a consensus onto standard operating procedures (SOPs) for performing what we generally define as the "liquid biopsy". Here we review the more recent acquisitions in the analysis of CTCs and tumor related nucleic acids, looking to the main open questions that are hampering their definitive employ in the routine clinical practice.

Circulating tumor cells isolation: the "post-EpCAM era"

Circulating tumor cells (CTCs) represent a submicroscopic fraction detached from a primary tumor and in transit to a secondary site. The prognostic significance of CTCs in metastatic cancer patients was demonstrated for the first time more than ten years ago. To date, it seems clear enough that CTCs are highly heterogeneous and dynamically change their shape. Thus, the inadequacy of epithelial cell adhesion molecule (EpCAM) as universal marker for CTCs detection seems unquestionable and alternative methods able to recognize a broader spectrum of phenotypes are definitely needed. In this review the pleiotropic functions of EpCAM are discussed in detail and the role of the molecule in the biology of CTCs is critically dissected.

Breast cancer circulating biomarkers: advantages, drawbacks, and new insights

As of today, the level of individualization of cancer therapies has reached a level that 20 years ago would be considered visionary. However, most of the diagnostic, prognostic, and therapy-predictive procedures which aim to improve the overall level of personalization are based on the evaluation of tumor tissue samples, therefore requiring surgical operations with consequent low compliance for patients and high costs for the hospital. Hence, the research of a panel of circulating indicators which may serve as source of information about tumor characteristics and which may be obtainable by a simple withdrawal of peripheral blood today represents a growing field of interest. This review aims to objectively summarize the characteristics of the currently available breast cancer circulating biomarkers, also providing an overview about the multitude of novel potential soluble predictors which are still under evaluation. Specifically, the usefulness of a so-called "liquid biopsy" will be discussed in terms of improvements of diagnosis, prognosis, and therapy-prediction, but an overview will be given also on the potentiality of the molecular characterization arising from the isolation of circulating biomarkers and cells. Although this review will focus on the specific case of the breast, in the future liquid biopsies will hopefully be available for virtually any type of neoplasms.

Microfluidic impedance cytometry of tumour cells in blood

The dielectric properties of tumour cells are known to differ from normal blood cells, and this difference can be exploited for label-free separation of cells. Conventional measurement techniques are slow and cannot identify rare circulating tumour cells (CTCs) in a realistic timeframe. We use high throughput single cell microfluidic impedance cytometry to measure the dielectric properties of the MCF7 tumour cell line (representative of CTCs), both as pure populations and mixed with whole blood. The data show that the MCF7 cells have a large membrane capacitance and size, enabling clear discrimination from all other leukocytes. Impedance analysis is used to follow changes in cell viability when cells are kept in suspension, a process which can be understood from modelling time-dependent changes in the dielectric properties (predominantly membrane conductivity) of the cells. Impedance cytometry is used to enumerate low numbers of MCF7 cells spiked into whole blood. Chemical lysis is commonly used to remove the abundant erythrocytes, and it is shown that this process does not alter the MCF7 cell count or change their dielectric properties. Combining impedance cytometry with magnetic bead based antibody enrichment enables MCF7 cells to be detected down to 100 MCF7 cells in 1 ml whole blood, a log 3.5 enrichment and a mean recovery of 92%. Microfluidic impedance cytometry could be easily integrated within complex cell separation systems for identification and enumeration of specific cell types, providing a fast in-line single cell characterisation method.

Optimisation of an immunohistochemistry method for the determination of androgen receptor expression levels in circulating tumour cells

BACKGROUND

AZD3514 inhibits and down regulates the androgen receptor (AR) and has undergone clinical trials in prostate cancer. To provide proof-of-mechanism (POM) in patients, an immunohistochemistry (IHC) method for determination of AR in circulating tumour cells (CTC) was developed and validated.

METHODS

After an assessment of specificity validation focused on intra- and inter-operator reproducibility utilising a novel modification of incurred sample reanalysis (ISR). β-Content γ-confidence tolerance intervals (BCTI) and Cohen's Kappa (κ) were employed in statistical analysis of results.

RESULTS

In a first set of IHC reproducibility experiments, almost perfect agreement was recorded (κ=0.94) when two different operators scored CTC as overall positive or negative for AR. However, BCTI analysis identified a specific bias in scoring staining intensity, where one operator favoured moderate over strong assignments, whereas the reverse was the case with the second operator. After a period of additional training involving deployment of a panel of standardised images, a second set of validation experiments were conducted. These showed correction of the inter-operator bias by BCTI with κ for scoring intensity increasing from 0.59 to 0.81, indicative of almost perfect agreement.

CONCLUSIONS

By application of BCTI to the validation of IHC, operator bias and therefore poor reproducibility can be identified, characterised and corrected to achieve a level of error normally associated with a quantitative biomarker assay, such as an ELISA. The methodological approach described herein can be applied to any generic IHC technique.

Isolation of circulating tumor cells by dielectrophoresis

Dielectrophoresis (DEP) is an electrokinetic method that allows intrinsic dielectric properties of suspended cells to be exploited for discrimination and separation. It has emerged as a promising method for isolating circulation tumor cells (CTCs) from blood. DEP-isolation of CTCs is independent of cell surface markers. Furthermore, isolated CTCs are viable and can be maintained in culture, suggesting that DEP methods should be more generally applicable than antibody-based approaches. The aim of this article is to review and synthesize for both oncologists and biomedical engineers interested in CTC isolation the pertinent characteristics of DEP and CTCs. The aim is to promote an understanding of the factors involved in realizing DEP-based instruments having both sufficient discrimination and throughput to allow routine analysis of CTCs in clinical practice. The article brings together: (a) the principles of DEP; (b) the biological basis for the dielectric differences between CTCs and blood cells; (c) why such differences are expected to be present for all types of tumors; and (d) instrumentation requirements to process 10 mL blood specimens in less than 1 h to enable routine clinical analysis. The force equilibrium method of dielectrophoretic field-flow fractionation (DEP-FFF) is shown to offer higher discrimination and throughput than earlier DEP trapping methods and to be applicable to clinical studies.

Technologies for label-free separation of circulating tumor cells: from historical foundations to recent developments

Circulating tumor cells (CTCs) are malignant cells shed into the bloodstream from a tumor that have the potential to establish metastases in different anatomical sites. The separation and subsequent characterization of these cells is emerging as an important tool for both biomarker discovery and the elucidation of mechanisms of metastasis. Established methods for separating CTCs rely on biochemical markers of epithelial cells that are known to be unreliable because of epithelial-to-mesenchymal transition, which reduces expression for epithelial markers. Emerging label-free separation methods based on the biophysical and biomechanical properties of CTCs have the potential to address this key shortcoming and present greater flexibility in the subsequent characterization of these cells. In this review we first present what is known about the biophysical and biomechanical properties of CTCs from historical studies and recent research. We then review biophysical label-free technologies that have been developed for CTC separation, including techniques based on filtration, hydrodynamic chromatography, and dielectrophoresis. Finally, we evaluate these separation methods and discuss requirements for subsequent characterization of CTCs.