A novel microchannel-based device to capture and analyze circulating tumor cells (CTCs) of breast cancer

Decoding physical principles of cell migration under controlled environment using microfluidics

Living cells can perform incredible tasks that man-made micro/nano-sized robots have not yet been able to accomplish. One example is that white blood cells can sense and move to the site of pathogen attack within minutes. The robustness and precision of cellular functions have been perfected through billions of years of evolution. In this context, we ask the question whether cells follow a set of physical principles to sense, adapt, and migrate. Microfluidics has emerged as an enabling technology for recreating well-defined cellular environment for cell migration studies, and its ability to follow single cell dynamics allows for the results to be amenable for theoretical modeling. In this review, we focus on the development of microfluidic platforms for recreating cellular biophysical (e.g., mechanical stress) and biochemical (e.g., nutrients and cytokines) environments for cell migration studies in 3D. We summarize the basic principles that cells (including bacteria, algal, and mammalian cells) use to respond to chemical gradients learned from microfluidic systems. We also discuss about novel biological insights gained from studies of cell migration under biophysical cues and the need for further quantitative studies of cell function under well-controlled biophysical environments in the future.

Towards Small Scale: Overview and Applications of Microfluidics in Biotechnology

Thanks to recent and continuing technological innovations, modern microfluidic systems are increasingly offering researchers working across all fields of biotechnology exciting new possibilities (especially with respect to facilitating high throughput analysis, portability, and parallelization). The advantages offered by microfluidic devices-namely, the substantially lowered chemical and sample consumption they require, the increased energy and mass transfer they offer, and their comparatively small size-can potentially be leveraged in every sub-field of biotechnology. However, to date, most of the reported devices have been deployed in furtherance of healthcare, pharmaceutical, and/or industrial applications. In this review, we consider examples of microfluidic and miniaturized systems across biotechnology sub-fields. In this context, we point out the advantages of microfluidics for various applications and highlight the common features of devices and the potential for transferability to other application areas. This will provide incentives for increased collaboration between researchers from different disciplines in the field of biotechnology.

Recent Advances in Methods for Circulating Tumor Cell Detection

Circulating tumor cells (CTCs) are released from primary tumors and transported through the body via blood or lymphatic vessels before settling to form micrometastases under suitable conditions. Accordingly, several studies have identified CTCs as a negative prognostic factor for survival in many types of cancer. CTCs also reflect the current heterogeneity and genetic and biological state of tumors; so, their study can provide valuable insights into tumor progression, cell senescence, and cancer dormancy. Diverse methods with differing specificity, utility, costs, and sensitivity have been developed for isolating and characterizing CTCs. Additionally, novel techniques with the potential to overcome the limitations of existing ones are being developed. This primary literature review describes the current and emerging methods for enriching, detecting, isolating, and characterizing CTCs.

Role of Circulating Tumor Cells in Determining Prognosis in Metastatic Breast Cancer

Dinesh Chandra DovalBackground  Circulating tumor cells (CTCs) in the peripheral blood may play a major role in the metastatic spread of breast cancer. This study was conducted to assess the role of CTCs to determine the prognosis in terms of survival in metastatic breast cancer patients. Methods  This prospective study of 36 patients was conducted at the Hospital from April 2016 to May 2018. Details of each patient related to the demographic profile, tumor type, treatment, and follow-up information were recorded. The number of CTCs in the peripheral blood was measured by Celsee PREP 400 sample processing system and Celsee Analyzer imaging station. Results  There was a positive correlation between the number of site of metastasis with number of CTCs ( p -value < 0.001). In the patients with clinical/partial response, a significant reduction in the number of CTCs after 1 month of therapy was observed ( p -value = 0.003). When the number of CTCs at baseline and 6 months were compared with the positron emission tomography response at 6 months, a statistically significant difference in CTCs in patients having partial response after 6 months was observed ( p -value = 0.001). On comparison with the responder groups, a statistically significant reduction in CTCs at baseline and 6 months was observed ( p -value = 0.001). Patients with CTCs less than 5 and more than or equal to 5 after 1 month of treatment had a mean progression-free survival of 11.1 months and 7.5 months ( p -value = 0.04) and a mean overall survival of 11.6 and 9.6 months ( p -value = 0.08), respectively. Conclusion  Assessment of CTCs provides a more quantifiable response than radiographic evaluation and at a much earlier time point and is also a better predictor of survival.

A micropillar array-based microfluidic chip for label-free separation of circulating tumor cells: The best micropillar geometry?

INTRODUCTION

The information derived from the number and characteristics of circulating tumor cells (CTCs), is crucial to ensure appropriate cancer treatment monitoring. Currently, diverse microfluidic platforms have been developed for isolating CTCs from blood, but it remains a challenge to develop a low-cost, practical, and efficient strategy.

OBJECTIVES

This study aimed to isolate CTCs from the blood of cancer patients via introducing a new and efficient micropillar array-based microfluidic chip (MPA-Chip), as well as providing prognostic information and monitoring the treatment efficacy in cancer patients.

METHODS

We fabricated a microfluidic chip (MPA-Chip) containing arrays of micropillars with different geometries (lozenge, rectangle, circle, and triangle). We conducted numerical simulations to compare velocity and pressure profiles inside the micropillar arrays. Also, we experimentally evaluated the capture efficiency and purity of the geometries using breast and prostate cancer cell lines as well as a blood sample. Moreover, the device's performance was validated on 12 patients with breast cancer (BC) in different states.

RESULTS

The lozenge geometry was selected as the most effective and optimized micropillar design for CTCs isolation, providing high capture efficiency (>85 %), purity (>90 %), and viability (97 %). Furthermore, the lozenge MPA-chip was successfully validated by the detection of CTCs from 12 breast cancer (BC) patients, with non-metastatic (median number of 6 CTCs) and metastatic (median number of 25 CTCs) diseases, showing different prognoses. Also, increasing the chemotherapy period resulted in a decrease in the number of captured CTCs from 23 to 7 for the metastatic patient. The MPA-Chip size was only 0.25 cm² and the throughput of a single chip was 0.5 ml/h, which can be increased by multiple MPA-Chips in parallel.

CONCLUSION

The lozenge MPA-Chip presented a novel micropillar geometry for on-chip CTC isolation, detection, and staining, and in the future, the possibilities can be extended to the culture of the CTCs.

PillarX: A Microfluidic Device to Profile Circulating Tumor Cell Clusters Based on Geometry, Deformability, and Epithelial State

Circulating tumor cell (CTC) clusters are associated with increased metastatic potential and worse patient prognosis, but are rare, difficult to count, and poorly characterized biophysically. The PillarX device described here is a bimodular microfluidic device (Pillar-device and an X-magnetic device) to profile single CTCs and clusters from whole blood based on their size, deformability, and epithelial marker expression. Larger, less deformable clusters and large single cells are captured in the Pillar-device and sorted according to pillar gap sizes. Smaller, deformable clusters and single cells are subsequently captured in the X-device and separated based on epithelial marker expression using functionalized magnetic nanoparticles. Clusters of established and primary breast cancer cells with variable degrees of cohesion driven by different cell-cell adhesion protein expression are profiled in the device. Cohesive clusters exhibit a lower deformability as they travel through the pillar array, relative to less cohesive clusters, and have greater collective invasive behavior. The ability of the PillarX device to capture clusters is validated in mouse models and patients of metastatic breast cancer. Thus, this device effectively enumerates and profiles CTC clusters based on their unique geometrical, physical, and biochemical properties, and could form the basis of a novel prognostic clinical tool.

Snail Augments Nuclear Deformability to Promote Lymph Node Metastasis of Head and Neck Squamous Cell Carcinoma

Up to 50% of head and neck squamous cell carcinoma (HNSCC) patients have lymph node (LN) metastasis, resulting in poor survival rate. Numerous studies have supported the notion that the alterations of gene expression and mechanical properties of cancer cells play an important role in cancer metastasis. However, which genes and how they regulate the biomechanical properties of HNSCC cells to promote LN metastasis remains elusive. In this study, we used an LN-metastatic mouse model in vivo to generate an LN-metastatic head and neck squamous cell carcinoma cell line and compared the differences in the biomolecular and biomechanical properties of LN-metastatic and non-metastatic cells. Our results showed that LN-metastatic cells had a higher level of Snail expression compared to non-LN-metastatic cells. The higher Snail expression promoted the cellular invasion capability in confined environments, mainly by increasing the longitudinal strain of the cell nuclei, which could be attributed to the stronger cell traction force and softer nuclear stiffness. These two biomechanical changes were correlated, respectively, to a larger amount of focal adhesion and less amount of nuclear lamins. Taken together, our works revealed not only the biomechanical profiles of LN-metastatic cells but also the corresponding biomolecular expressions to pinpoint the key process in LN metastasis.

Breast cancer circulating tumor cells with mesenchymal features-an unreachable target?

Circulating tumor cells (CTCs) mediate dissemination of solid tumors and can be an early sign of disease progression. Moreover, they show a great potential in terms of non-invasive, longitudinal monitoring of cancer patients. CTCs have been extensively studied in breast cancer (BC) and were shown to present a significant phenotypic plasticity connected with initiation of epithelial-mesenchymal transition (EMT). Apart from conferring malignant properties, EMT affects CTCs recovery rate, making a significant portion of CTCs from patients’ samples undetected. Wider application of methods and markers designed to isolate and identify mesenchymal CTCs is required to expand our knowledge about the clinical impact of mesenchymal CTCs. Therefore, here we provide a comprehensive review of clinical significance of mesenchymal CTCs in BC together with statistical analysis of previously published data, in which we assessed the suitability of a number of methods/markers used for isolation of CTCs with different EMT phenotypes, both in in vitro spike-in tests with BC cell lines, as well as clinical samples. Results of spiked-in cell lines indicate that, in general, methods not based on epithelial enrichment only, capture mesenchymal CTCs much more efficiently that CellSearch^® (golden standard in CTCs detection), but at the same time are not much inferior to Cell Search^®, though large variation in recovery rates of added cells among the methods is observed. In clinical samples, where additional CTCs detection markers are needed, positive epithelial-based CTCs enrichment was the most efficient in isolating CTCs with mesenchymal features from non-metastatic BC patients. From the marker side, PI3K and VIM were contributing the most to detection of CTCs with mesenchymal features (in comparison to SNAIL) in non-metastatic and metastatic BC patients, respectively. However, additional data are needed for more robust identification of markers for efficient detection of CTCs with mesenchymal features.

Partial thermal imidization of polyelectrolyte multilayer cell tethering surfaces (TetherChip) enables efficient cell capture and microtentacle fixation for circulating tumor cell analysis

The technical challenges of imaging non-adherent tumor cells pose a critical barrier to understanding tumor cell responses to the non-adherent microenvironments of metastasis, like the bloodstream or lymphatics. In this study, we optimized a microfluidic device (TetherChip) engineered to prevent cell adhesion with an optically-clear, thermal-crosslinked polyelectrolyte multilayer nanosurface and a terminal lipid layer that simultaneously tethers the cell membrane for improved spatial immobilization. Thermal imidization of the TetherChip nanosurface on commercially-available microfluidic slides allows up to 98% of tumor cell capture by the lipid tethers. Importantly, time-lapse microscopy demonstrates that unique microtentacles on non-adherent tumor cells are rapidly destroyed during chemical fixation, but tethering microtentacles to the TetherChip surface efficiently preserves microtentacle structure post-fixation and post-blood isolation. TetherChips remain stable for more than 6 months, enabling shipment to distant sites. The broad retention capability of TetherChips allows comparison of multiple tumor cell types, revealing for the first time that carcinomas beyond breast cancer form microtentacles in suspension. Direct integration of TetherChips into the Vortex VTX-1 CTC isolation instrument shows that live CTCs from blood samples are efficiently captured on TetherChips for rapid fixation and same-day immunofluorescence analysis. Highly efficient and unbiased label-free capture of CTCs on a surface that allows rapid chemical fixation also establishes a streamlined clinical workflow to stabilize patient tumor cell samples and minimize analytical variables. While current studies focus primarily on CTC enumeration, this microfluidic device provides a novel platform for functional phenotype testing in CTCs with the ultimate goal of identifying anti-metastatic, patient-specific therapies.

Magnetically driven microfluidics for isolation of circulating tumor cells

Circulating tumor cells (CTCs) largely contribute to cancer metastasis and show potential prognostic significance in cancer isolation and detection. Miniaturization has progressed significantly in the last decade which in turn enabled the development of several microfluidic systems. The microfluidic systems offer a controlled microenvironment for studies of fundamental cell biology, resulting in the rapid development of microfluidic isolation of CTCs. Due to the inherent ability of magnets to provide forces at a distance, the technology of CTCs isolation based on the magnetophoresis mechanism has become a routine methodology. This historical review aims to introduce two principles of magnetic isolation and recent techniques, facilitating research in this field and providing alternatives for researchers in their study of magnetic isolation. Researchers intend to promote effective CTC isolation and analysis as well as active development of next-generation cancer treatment. The first part of this review summarizes the primary principles based on positive and negative magnetophoretic isolation and describes the metrics for isolation performance. The second part presents a detailed overview of the factors that affect the performance of CTC magnetic isolation, including the magnetic field sources, functionalized magnetic nanoparticles, magnetic fluids, and magnetically driven microfluidic systems.

FISH and chips: a review of microfluidic platforms for FISH analysis

Fluorescence in situ hybridization (FISH) allows visualization of specific nucleic acid sequences within an intact cell or a tissue section. It is based on molecular recognition between a fluorescently labeled probe that penetrates the cell membrane of a fixed but intact sample and hybridizes to a nucleic acid sequence of interest within the cell, rendering a measurable signal. FISH has been applied to, for example, gene mapping, diagnosis of chromosomal aberrations and identification of pathogens in complex samples as well as detailed studies of cellular structure and function. However, FISH protocols are complex, they comprise of many fixation, incubation and washing steps involving a range of solvents and temperatures and are, thus, generally time consuming and labor intensive. The complexity of the process, the relatively high-priced fluorescent probes and the fairly high-end microscopy needed for readout render the whole process costly and have limited wider uptake of this powerful technique. In recent years, there have been attempts to transfer FISH assay protocols onto microfluidic lab-on-a-chip platforms, which reduces the required amount of sample and reagents, shortens incubation times and, thus, time to complete the protocol, and finally has the potential for automating the process. Here, we review the wide variety of approaches for lab-on-chip-based FISH that have been demonstrated at proof-of-concept stage, ranging from FISH analysis of immobilized cell layers, and cells trapped in arrays, to FISH on tissue slices. Some researchers have aimed to develop simple devices that interface with existing equipment and workflows, whilst others have aimed to integrate the entire FISH protocol into a fully autonomous FISH on-chip system. Whilst the technical possibilities for FISH on-chip are clearly demonstrated, only a small number of approaches have so far been converted into off-the-shelf products for wider use beyond the research laboratory.

Characterization of a novel automated microfiltration device for the efficient isolation and analysis of circulating tumor cells from clinical blood samples

The detection and analysis of circulating tumor cells (CTCs) may enable a broad range of cancer-related applications, including the identification of acquired drug resistance during treatments. However, the non-scalable fabrication, prolonged sample processing times, and the lack of automation, associated with most of the technologies developed to isolate these rare cells, have impeded their transition into the clinical practice. This work describes a novel membrane-based microfiltration device comprised of a fully automated sample processing unit and a machine-vision-enabled imaging system that allows the efficient isolation and rapid analysis of CTCs from blood. The device performance was characterized using four prostate cancer cell lines, including PC-3, VCaP, DU-145, and LNCaP, obtaining high assay reproducibility and capture efficiencies greater than 93% after processing 7.5 mL blood samples spiked with 100 cancer cells. Cancer cells remained viable after filtration due to the minimal shear stress exerted over cells during the procedure, while the identification of cancer cells by immunostaining was not affected by the number of non-specific events captured on the membrane. We were also able to identify the androgen receptor (AR) point mutation T878A from 7.5 mL blood samples spiked with 50 LNCaP cells using RT-PCR and Sanger sequencing. Finally, CTCs were detected in 8 out of 8 samples from patients diagnosed with metastatic prostate cancer (mean ± SEM = 21 ± 2.957 CTCs/mL, median = 21 CTCs/mL), demonstrating the potential clinical utility of this device.

A melt-electrowritten filter for capture and culture of circulating colon cancer cells

Metastasis is the major cause of death in cancer patients accounting for about 90% of the mortality. The detection and analysis of the hallmark of metastasis, circulating tumor cells (CTCs), have significant impact in cancer biology and clinical practice. However, the scarcity of CTCs in blood, particularly in that of colorectal cancer patients, is a serious bottleneck in the development of CTC-based precision medicine. Herein, the melt electrowriting (MEW) technology was used for reproductive fabrication of a biocompatible antibody-presenting polycaprolactone filter with tailored porous structure. It is demonstrated, for the first time, that such filter can be used not only to catch cancer cells spiked in whole blood but also to culture the cancer cells directly on site. Specifically, HT29 colon cancer cells can be captured with an efficiency of 85%, and when spiked into 4 mL of whole blood, 47% were captured on one Ø12mm filter. Furthermore, repeated capture and culture experiments have shown that as few as 20 HT29 colon cancer cells spiked into 4 mL of whole blood can be captured on the filter and within 2 weeks be expanded on site to become tumor bodies that are visible to the untrained eye. This filter allows for downstream analysis, such as flow cytometry, immunocytochemistry, Western blotting, and rt-qPCR. This technology represents a simple and cost-effective platform that potentially enables fast and efficient culture of rare CTCs from patients' blood. This provides non-invasive alternatives for solid biopsy tumor materials for treatment screening, with great potential to realize precision medicine for cancer treatment.

A Novel, Circulating Tumor Cell Enrichment Method Reduces ARv7 False Positivity in Patients with Castration-Resistant Prostate Cancer

BACKGROUND

The AR-V7 splice variant is a cause of castration-resistant prostate cancer (CRPC). However, testing for the presence of AR-V7 by real-time polymerase chain reaction (RT-PCR) shows AR-V7 positivity in healthy individuals. We hypothesized that the positivity reflects contamination by hematopoietic cells. We tried a novel circulating tumor cell (CTC) enrichment instrument, using Celsee, to clear hematopoietic cells.

METHODS

We tested whole blood or Celsee-enriched samples for AR-V7 by RT-PCR, and included samples from 41 CRPC patients undergoing sequential therapy. We evaluated the associations between AR-V7 status and clinical factors. We evaluated factors affecting AR-V7 positivity.

RESULTS

AR-V7 positivity was lower in Celsee-enriched than in whole blood specimens. AR-V7 and clinical factors did not predict the therapy effectiveness. We found no significant differences in the effectiveness of enzalutamide/abiraterone (Enz/Abi) upon AR-V7 evaluation. All AR-V7 positive patients had resistance to Enz/Abi. Docetaxel (DTX), cabazitaxel (CBZ), and Radium223 treatment showed no significant difference in the treatment effectiveness, regardless of AR-V7 presence. AR-V7 was more frequently positive than Extent of disease (EOD) 2 in cases with bone metastases.

CONCLUSION

Celsee CTC enrichment suppresses AR-V7 false positivity. All AR-V7 positive patients presented resistance to Enz/Abi. DTX, CBZ, and Radium223 were effective and remain treatment options. AR-V7 positivity should progressively appear in patients with advanced bone metastases.

Heterogeneity of Circulating Tumor Cells in Breast Cancer: Identifying Metastatic Seeds

Metastasis being the main cause of breast cancer (BC) mortality represents the complex and multistage process. The entrance of tumor cells into the blood vessels and the appearance of circulating tumor cells (CTCs) seeding and colonizing distant tissues and organs are one of the key stages in the metastatic cascade. Like the primary tumor, CTCs are extremely heterogeneous and presented by clusters and individual cells which consist of phenotypically and genetically distinct subpopulations. However, among this diversity, only a small number of CTCs is able to survive in the bloodstream and to form metastases. The identification of the metastasis-initiating CTCs is believed to be a critical issue in developing therapeutic strategies against metastatic disease. In this review, we summarize the available literature addressing morphological, phenotypic and genetic heterogeneity of CTCs and the molecular makeup of specific subpopulations associated with BC metastasis. Special attention is paid to the need for in vitro and in vivo studies to confirm the tumorigenic and metastatic potential of metastasis-associating CTCs. Finally, we consider treatment approaches that could be effective to eradicate metastatic CTCs and to prevent metastasis.

Circulating tumor cells in precision oncology: clinical applications in liquid biopsy and 3D organoid model

Circulating tumor cells (CTCs) are a rare subset of cells found in the blood of patients with solid tumors, which function as a seed for metastases. Cancer cells metastasize through the bloodstream either as single migratory CTCs or as multicellular groupings-CTC clusters. The CTCs preserve primary tumor heterogeneity and mimic tumor properties, and may be considered as clinical biomarker, preclinical model, and therapeutic target. The potential clinical application of CTCs is being a component of liquid biopsy. CTCs are also good candidates for generating preclinical models, especially 3D organoid cultures, which could be applied in drug screening, disease modeling, genome editing, tumor immunity, and organoid biobanks. In this review, we summarize current knowledge on the value and promise of evolving CTC technologies and highlight cutting-edge research on CTCs in liquid biopsy, tumor metastasis, and organoid preclinical models. The study of CTCs offers broad pathways to develop new biomarkers for tumor patient diagnosis, prognosis, and response to therapy, as well as translational models accelerating oncologic drug development.

Development of a Highly Sensitive Technique for Capturing Renal Cell Cancer Circulating Tumor Cells

Purpose: Liquid biopsy is becoming increasingly important as a guide for selecting new drugs and determining their efficacy. In urological cancer, serum markers for renal cell and urothelial cancers has made the development of liquid biopsy for these cancers strongly desirable. Liquid biopsy is less invasive than conventional tissue biopsy is, enabling frequent biopsies and, therefore, is considered effective for monitoring the treatment course. Circulating tumor cells (CTCs) are a representative liquid biopsy specimen. In the present study, we focused on developing our novel technology for capturing renal cell cancer (RCC)-CTCs using an anti-G250 antibody combined with new devices. Basic experiments of our technology showed that it was possible to detect RCC-CTC with a fairly high accuracy of about 95%. Also, RCC-CTC was identified in the peripheral blood of actual RCC patients. Additionally, during the treatment course of the RCC patient, change in the number of RCC-CTC was confirmed in one case. We believe that the technology we developed will be useful for determining the treatment efficacy and drug selection for the treatment of renal cell cancer (RCC). In order to solve issues such as thresholds setting of this technology, large-scale clinical trials are expected.

Liquid biopsy using the nanotube-CTC-chip: capture of invasive CTCs with high purity using preferential adherence in breast cancer patients

In this paper, we report the development of the nanotube-CTC-chip for isolation of tumor-derived epithelial cells (circulating tumor cells, CTCs) from peripheral blood, with high purity, by exploiting the physical mechanisms of preferential adherence of CTCs on a nanotube surface. The nanotube-CTC-chip is a new 76-element microarray technology that combines carbon nanotube surfaces with microarray batch manufacturing techniques for the capture and isolation of tumor-derived epithelial cells. Using a combination of red blood cell (RBC) lysis and preferential adherence, we demonstrate the capture and enrichment of CTCs with a 5-log reduction of contaminating WBCs. EpCAM negative MDA-MB-231/luciferase-2A-green fluorescent protein (GFP) cells were spiked in the blood of wild mice and enriched using an RBC lysis protocol. The enriched samples were then processed using the nanotube-CTC-chip for preferential CTC adherence on the nanosurface and counting the GFP cells yielded anywhere from 89% to 100% capture from the droplets. Electron microscopy (EM) studies showed focal adhesion with filaments from the cell body to the nanotube surface. We compared the nanotube preferential adherence to collagen adhesion matrix (CAM) scaffolding, reported as a viable strategy for CTC capture in patients. The CAM scaffolding on the device surface yielded 50% adherence with 100% tracking of cancer cells (adhered vs. non-adhered) versus carbon nanotubes with >90% adherence and 100% tracking for the same protocol. The nanotube-CTC-chip successfully captured CTCs in the peripheral blood of breast cancer patients (stage 1-4) with a range of 4-238 CTCs per 8.5 ml blood or 0.5-28 CTCs per ml. CTCs (based on CK8/18, Her2, EGFR) were successfully identified in 7/7 breast cancer patients, and no CTCs were captured in healthy controls (n = 2). CTC enumeration based on multiple markers using the nanotube-CTC-chip enables dynamic views of metastatic progression and could potentially have predictive capabilities for diagnosis and treatment response.

Fast and efficient microfluidic cell filter for isolation of circulating tumor cells from unprocessed whole blood of colorectal cancer patients

Liquid biopsy offers unique opportunities for low invasive diagnosis, real-time patient monitoring and treatment selection. The phenotypic and molecular profile of circulating tumor cells (CTCs) can provide key information about the biology of tumor cells, contributing to personalized therapy. CTC isolation is still challenging, mainly due to their heterogeneity and rarity. To overcome this limitation, a microfluidic chip for label-free isolation of CTCs from peripheral blood was developed. This device, the CROSS chip, captures CTCs based on their size and deformability with an efficiency of 70%. Using 2 chips, 7.5 ml of whole blood are processed in 47 minutes with high purity, as compared to similar technologies and assessed by in situ immunofluorescence. The CROSS chip performance was compared to the CellSearch system in a set of metastatic colorectal cancer patients, resulting in higher capture of DAPI+/CK+/CD45- CTCs in all individuals tested. Importantly, CTC enumeration by CROSS chip enabled stratification of patients with different prognosis. Lastly, cells isolated in the CROSS chip were lysed and further subjected to molecular characterization by droplet digital PCR, which revealed a mutation in the APC gene for most patient samples analyzed, confirming their colorectal origin and the versatility of the technology for downstream applications.

Hydro-Seq enables contamination-free high-throughput single-cell RNA-sequencing for circulating tumor cells

Molecular analysis of circulating tumor cells (CTCs) at single-cell resolution offers great promise for cancer diagnostics and therapeutics from simple liquid biopsy. Recent development of massively parallel single-cell RNA-sequencing (scRNA-seq) provides a powerful method to resolve the cellular heterogeneity from gene expression and pathway regulation analysis. However, the scarcity of CTCs and the massive contamination of blood cells limit the utility of currently available technologies. Here, we present Hydro-Seq, a scalable hydrodynamic scRNA-seq barcoding technique, for high-throughput CTC analysis. High cell-capture efficiency and contamination removal capability of Hydro-Seq enables successful scRNA-seq of 666 CTCs from 21 breast cancer patient samples at high throughput. We identify breast cancer drug targets for hormone and targeted therapies and tracked individual cells that express markers of cancer stem cells (CSCs) as well as of epithelial/mesenchymal cell state transitions. Transcriptome analysis of these cells provides insights into monitoring target therapeutics and processes underlying tumor metastasis.

Heterogeneity in Circulating Tumor Cells: The Relevance of the Stem-Cell Subset

The release of circulating tumor cells (CTCs) into vasculature is an early event in the metastatic process. The analysis of CTCs in patients has recently received widespread attention because of its clinical implications, particularly for precision medicine. Accumulated evidence documents a large heterogeneity in CTCs across patients. Currently, the most accepted view is that tumor cells with an intermediate phenotype between epithelial and mesenchymal have the highest plasticity. Indeed, the existence of a meta-stable or partial epithelial–mesenchymal transition (EMT) cell state, with both epithelial and mesenchymal features, can be easily reconciled with the concept of a highly plastic stem-like state. A close connection between EMT and cancer stem cells (CSC) traits, with enhanced metastatic competence and drug resistance, has also been described. Accordingly, a subset of CTCs consisting of CSC, present a stemness profile, are able to survive chemotherapy, and generate metastases after xenotransplantation in immunodeficient mice. In the present review, we discuss the current evidence connecting CTCs, EMT, and stemness. An improved understanding of the CTC/EMT/CSC connections may uncover novel therapeutic targets, irrespective of the tumor type, since most cancers seem to harbor a pool of CSCs, and disclose important mechanisms underlying tumorigenicity.

Microfluidic technologies for circulating tumor cell isolation

Metastasis is the main cause of tumor-related death, and the dispersal of tumor cells through the circulatory system is a critical step in the metastatic process. Early detection and analysis of circulating tumor cells (CTCs) is therefore important for early diagnosis, prognosis, and effective treatment of cancer, enabling favorable clinical outcomes in cancer patients. Accurate and reliable methods for isolating and detecting CTCs are necessary to obtain this clinical information. Over the past two decades, microfluidic technologies have demonstrated great potential for isolating and detecting CTCs from blood. The present paper reviews current advanced microfluidic technologies for isolating CTCs based on various biological and physical principles, and discusses their fundamental advantages and drawbacks for subsequent cellular and molecular assays. Owing to significant genetic heterogeneity among CTCs, microfluidic technologies for isolating individual CTCs have recently been developed. We discuss these single-cell isolation methods, as well as approaches to overcoming the limitations of current microfluidic CTC isolation technologies. Finally, we provide an overview of future innovative microfluidic platforms.

A microfluidic platform integrated with field-effect transistors for enumeration of circulating tumor cells

Circulating tumor cells (CTCs) are one of the promising cancer biomarkers whose concentrations are measured not only in the initial diagnostic stages, but also as treatment progresses. However, the existing methods for CTC detection are relatively time-consuming and labor-intensive. In this study, a new microfluidic platform integrated with field-effect transistors (FETs) and chambers for the trapping of CTCs was developed. This novel design could not only trap CTCs from whole blood samples, but also enumerate them via FET sensing of CTC-specific aptamer-CTC complexes. The FET output signal was experimentally found to increase with the increasing number of captured CTCs. More importantly, the enumeration of spiked CTCs in blood samples could be achieved in accordance with the signals measured on the FET devices. We therefore believe that this automated system could be a useful tool for enumeration of CTCs.

Liquid Biopsy in Thyroid Cancer: New Insight

Thyroid cancer, one of the most widespread malignancies of the endocrine-related system that over the past three decades, has a vivid increasing rate. The diagnosis and management of it is dependent on the tumor type and stage. Thyroid cancer is divided into four main types, including PTC (papillary thyroid carcinoma), FTC (follicular thyroid carcinoma), MTC (medullarly thyroid carcinoma), and ATC (anaplastic thyroid carcinoma). The development of the noninvasive diagnostic tool for plasma genotyping, also known as "liquid biopsy", brings a new insight for cancer diagnosis and prognosis. It is mainly containing circulating tumor DNA (ctDNA), circulating tumor cell (CTC), exosomes and extrachromosomal circular DNA (ecDNA). Liquid biopsy as a new plasma genotyping source brings a new prospective of tumor monitoring and therapy. It beneficially reduces the need of tissue biopsy and made early recognition of relapse as well. This article summarizes its components characteristics and their benefit in diagnosis and treatment of thyroid cancer.

Entrapment of Prostate Cancer Circulating Tumor Cells with a Sequential Size-Based Microfluidic Chip

Circulating tumor cells (CTCs) are broadly accepted as an indicator for early cancer diagnosis and disease severity. However, there is currently no reliable method available to capture and enumerate all CTCs as most systems require either an initial CTC isolation or antibody-based capture for CTC enumeration. Many size-based CTC detection and isolation microfluidic platforms have been presented in the past few years. Here we describe a new size-based, multiple-row cancer cell entrapment device that captured LNCaP-C4-2 prostate cancer cells with >95% efficiency when in spiked mouse whole blood at ∼50 cells/mL. The capture ratio and capture limit on each row was optimized and it was determined that trapping chambers with five or six rows of micro constriction channels were needed to attain a capture ratio >95%. The device was operated under a constant pressure mode at the inlet for blood samples which created a uniform pressure differential across all the microchannels in this array. When the cancer cells deformed in the constriction channel, the blood flow temporarily slowed down. Once inside the trapping chamber, the cancer cells recovered their original shape after the deformation created by their passage through the constriction channel. The CTCs reached the cavity region of the trapping chamber, such that the blood flow in the constriction channel resumed. On the basis of this principle, the CTCs will be captured by this high-throughput entrapment chip (CTC-HTECH), thus confirming the potential for our CTC-HTECH to be used for early stage CTC enrichment and entrapment for clinical diagnosis using liquid biopsies.

Liquid biopsy in pancreatic cancer: the beginning of a new era

With dismal survival rate pancreatic cancer remains one of the most aggressive and devastating malignancy. Predominantly, due to the absence of a dependable methodology for early identification and limited therapeutic options for advanced disease. However, it takes over 17 years to develop pancreatic cancer from initiation of mutation to metastatic cancer; therefore, if diagnosed early; it may increase overall survival dramatically, thus, providing a window of opportunity for early detection. Recently, genomic expression analysis defined 4 subtypes of pancreatic cancer based on mutated genes. Hence, we need simple and standard, minimally invasive test that can monitor those altered genes or their associated pathways in time for the success of precision medicine, and liquid biopsy seems to be one answer to all these questions. Again, liquid biopsy has an ability to pair with genomic tests. Additionally, liquid biopsy based development of circulating tumor cells derived xenografts, 3D organoids system, real-time monitoring of genetic mutations by circulating tumor DNA and exosome as the targeted drug delivery vehicle holds lots of potential for the treatment and cure of pancreatic cancer. At present, diagnosis of pancreatic cancer is frantically done on the premise of CA19-9 and radiological features only, which doesn't give a picture of genetic mutations and epigenetic alteration involved. In this manner, the current diagnostic paradigm for pancreatic cancer diagnosis experiences low diagnostic accuracy. This review article discusses the current state of liquid biopsy in pancreatic cancer as diagnostic and therapeutic tools and future perspectives of research in the light of circulating tumor cells, circulating tumor DNA and exosomes.

Enrichment and mutation detection of circulating tumor cells from blood samples

The potential of circulating tumor cells (CTCs) in the diagnosis and prognosis of cancer patients has become increasingly attractive. However, molecular analysis of CTCs is hindered by low sensitivity and a high level of background leukocytes in CTC enrichment technologies. We have developed a novel protocol using a microfluidic device, which enriches and retrieves CTCs from blood samples. The principle of CTC capturing is that tumor cells are larger and less deformable than normal blood cells. To evaluate the potential of utilizing Celsee PREP100 in CTC molecular analysis, we prepared prostate cancer cell lines PC3 and LNCaP, retrieved the captured cells and analyzed them using PCR amplicon sequencing. We were able to recover an average of 79% of 110-1,100 PC3 and 60–1,500 LNCaP cells, and detect the p.K139fs*3 deletion of the p53 gene in PC3 cells and p.T877A mutation of the androgen receptor gene in LNCaP cells. Next, we spiked these two types of cells into normal donor blood samples, captured the cells and analyzed them using PCR amplicon sequencing. The PC3 and LNCaP cells were captured and retrieved with the ratio of captured CTCs to the background leukocytes reaching 1:1.5 for PC3 and 1:2.9 for LNCaP cells. We further revealed that the p.K139fs*3 deletion and p.T877A mutation can be detected in the captured PC3 and LNCaP cells, respectively. We successfully validated this approach using clinical blood samples from patients with metastatic prostate cancer. Our results demonstrated a novel approach for CTC enrichment and illustrated the potential of CTC molecular characterization for diagnosis, prognosis and treatment selection of patients with metastatic malignancy.

Size-Based Differentiation of Cancer and Normal Cells by a Particle Size Analyzer Assisted by a Cell-Recognition PC Software

Detection of anomalous cells such as cancer cells from normal blood cells has the potential to contribute greatly to cancer diagnosis and therapy. Conventional methods for the detection of cancer cells are usually tedious and cumbersome. Herein, we report on the use of a particle size analyzer for the convenient size-based differentiation of cancer cells from normal cells. Measurements made using a particle size analyzer revealed that size parameters for cancer cells are significantly greater (e.g., inner diameter and width) than the corresponding values for normal cells (white blood cells (WBC), lymphocytes and splenocytes), with no significant difference in shape parameters (e.g., circularity and convexity). The inner diameter of many cancer cell lines is greater than 10 µm, in contrast to normal cells. For the detection of WBC having similar size to that of cancer cells, we developed a PC software "Cancer Cell Finder" that differentiates them from cancer cells based on brightness stationary points on a cell surface. Furthermore, the aforementioned method was validated for cancer cell/clusters detection in spiked mouse blood samples (a B16 melanoma mouse xenograft model) and circulating tumor cell cluster-like particles in the cat and dog (diagnosed with cancer) blood samples. These results provide insights into the possible applicability of the use of a particle size analyzer in conjunction with PC software for the convenient detection of cancer cells in experimental and clinical samples for theranostics.

New insights in non-small-cell lung cancer: circulating tumor cells and cell-free DNA

Lung cancer is the second most frequent tumor and the leading cause of death by cancer in both men and women. Increasing knowledge about the cancer genome and tumor environment has led to a new setting in which morphological and molecular characterization is needed to treat patients in the most personalized way in order to achieve better outcomes. Since tumor products can be detected in body fluids, the liquid biopsy, particularly, peripheral blood, has emerged as a new source for lung cancer biomarker's analysis. A variety of tumor components can be used for this purpose. Among them, circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA) should be especially considered. Different detection methods for both CTCs and ctDNA have been and are being developed to improve the sensitivity and specificity of these tests. This would lead to better characterization and would solve some clinical doubts at different disease evolution times, e.g., intratumoral or temporal heterogeneity, difficulty in the obtaining a tumor sample, etc., and would also avoid the side effects of very expensive and complicated tumor obtaining interventions. CTCs and ctDNA are useful in different lung cancer settings. Their value has been shown for the early diagnosis, prognosis, prediction of treatment efficacy, monitoring responses and early detection of lung cancer relapse. CTCs have still not been validated for use in clinical settings in non-small-cell lung cancer (NSCLC), while ctDNA has been approved by the Food and Drug Administration (FDA) and European Medical Association (EMA), and the main clinical guidelines used for detect different epidermal growth factor receptor (EGFR) mutations and the monitoring and treatment choice of mutated patients with tyrosine kinase inhibitors (TKIs). This review, describes how ctDNA seem to be winning the race against CTCs from the laboratory bench to clinical practice due to easier obtaining methods, manipulation and its implementation into clinical practice.

Analytical evaluation for somatic mutation detection in circulating tumor cells isolated using a lateral magnetophoretic microseparator

CTCs are currently in the spotlight because provide comprehensive genetic information that enables monitoring of the evolution of cancer and selection of appropriate therapeutic strategies that cannot be obtained from a single-site tumor biopsy. Despite their importance, current techniques for isolating CTCs are limited in terms of their ability to yield high-quality CTCs from peripheral blood for use in profiling cancer genetic mutations by DNA sequencing technologies. This paper introduces a lateral magnetophoretic microseparator (the 'CTC-μChip') for isolating highly pure CTCs from blood, which facilitates the detection of somatic mutations in isolated CTCs. To isolate CTCs from peripheral blood, nucleated cells were first prepared by red blood cell lysis. Then, CTCs were isolated from nucleated cells within 30 min using the CTC-μChip. Analytical evaluation using 5 mL blood samples spiked with 5-50 MCF7 breast cancer cells demonstrated that the average recovery rate of the CTC-μChip was 99.08 %. The average number of residual white blood cells (WBCs) in isolated samples was 53, meaning that the WBC depletion rate is 472,000-fold (5.67 log), assuming that blood contains 5 × 10(6) WBCs per milliliter. The isolated MCF7 cells had a purity of 6.9 - 67.9 %, depending on the spiked MCF7 concentration. Using next-generation sequencing technology, heterozygous somatic mutations (PIK3CA and APC) of MCF7 cells were evaluated in the isolated samples. The results showed that somatic mutations could be detected in as few as two MCF7 cells per milliliter of blood, indicating that the CTC-μChip facilitates the detection of somatic variants in CTCs.

Nucleolin Staining May Aid in the Identification of Circulating Prostate Cancer Cells

INTRODUCTION

Circulating tumor cells (CTCs) have great potential as circulating biomarkers for solid malignancies. Currently available assays for CTC detection rely on epithelial markers with somewhat limited sensitivity and specificity. We found that the staining pattern of nucleolin, a common nucleolar protein in proliferative cells, separates CTCs from white blood cells (WBCs) in men with metastatic prostate cancer.

PATIENTS AND METHODS

Whole peripheral blood from 3 men with metastatic prostate cancer was processed with the AccuCyte CTC system (RareCyte, Seattle, WA). Slides were immunostained with 4',6-diamidino-2-phenylindole (DAPI), anti-pan-cytokeratin, anti-CD45/CD66b/CD11b/CD14/CD34, and anti-nucleolin antibodies and detected using the CyteFinder system. DAPI nucleolin colocalization and staining pattern wavelet entropy were measured with novel image analysis software.

RESULTS

A total of 33,718 DAPI-positive cells were analyzed with the novel imaging software, of which 45 (0.13%) were known CTCs based on the established AccuCyte system criteria. Nucleolin staining pattern for segmentable CTCs demonstrated greater wavelet entropy than that of WBCs (median wavelet entropy, 6.86 × 107 and 3.03 × 106, respectively; P = 2.92 × 10-22; approximated z statistic = 9.63). Additionally, the total nucleolin staining of CTCs was greater than that of WBCs (median total pixel intensity, 1.20 × 105 and 2.55 × 104 integrated pixel units, respectively; P = 2.40 × 10-21; approximated z statistic = 9.41).

CONCLUSION

Prostate cancer CTCs displayed unique nucleolin expression and localization compared to WBCs. This finding has the potential to serve as the basis for a sensitive and specific CTC detection method.

Advances in single-cell RNA sequencing and its applications in cancer research

Unlike population-level approaches, single-cell RNA sequencing enables transcriptomic analysis of an individual cell. Through the combination of high-throughput sequencing and bioinformatic tools, single-cell RNA-seq can detect more than 10,000 transcripts in one cell to distinguish cell subsets and dynamic cellular changes. After several years’ development, single-cell RNA-seq can now achieve massively parallel, full-length mRNA sequencing as well as in situ sequencing and even has potential for multi-omic detection. One appealing area of single-cell RNA-seq is cancer research, and it is regarded as a promising way to enhance prognosis and provide more precise target therapy by identifying druggable subclones. Indeed, progresses have been made regarding solid tumor analysis to reveal intratumoral heterogeneity, correlations between signaling pathways, stemness, drug resistance, and tumor architecture shaping the microenvironment. Furthermore, through investigation into circulating tumor cells, many genes have been shown to promote a propensity toward stemness and the epithelial-mesenchymal transition, to enhance anchoring and adhesion, and to be involved in mechanisms of anoikis resistance and drug resistance. This review focuses on advances and progresses of single-cell RNA-seq with regard to the following aspects:

1. Methodologies of single-cell RNA-seq

2. Single-cell isolation techniques

3. Single-cell RNA-seq in solid tumor research

4. Single-cell RNA-seq in circulating tumor cell research

5. Perspectives

Single-Cell Mechanical Characteristics Analyzed by Multiconstriction Microfluidic Channels

A microfluidic device composed of variable numbers of multiconstriction channels is reported in this paper to differentiate a human breast cancer cell line, MDA-MB-231, and a nontumorigenic human breast cell line, MCF-10A. Differences between their mechanical properties were assessed by comparing the effect of single or multiple relaxations on their velocity profiles which is a novel measure of their deformation ability. Videos of the cells were recorded via a microscope using a smartphone, and imported to a tracking software to gain the position information on the cells. Our results indicated that a multiconstriction channel design with five deformation (50 μm in length, 10 μm in width, and 8 μm in height) separated by four relaxation (50 μm in length, 40 μm in width, and 30 μm in height) regions was superior to a single deformation design in differentiating MDA-MB-231 and MCF-10A cells. Velocity profile criteria can achieve a differentiation accuracy around 95% for both MDA-MB-231 and MCF-10A cells.

Nanoparticle functionalized laser patterned substrate: an innovative route towards low cost biomimetic platforms

Integration of nanotechnology and advanced manufacturing processes presents an attractive route to produce devices for adaptive biomedical device technologies.

Microfluidic-Based Enrichment and Retrieval of Circulating Tumor Cells for RT-PCR Analysis

Molecular analysis of circulating tumor cells (CTCs) is hindered by low sensitivity and high level of background leukocytes of currently available CTC enrichment technologies. We have developed a novel device to enrich and retrieve CTCs from blood samples by using a microfluidic chip. The Celsee PREP100 device captures CTCs with high sensitivity and allows the captured CTCs to be retrieved for molecular analysis. It uses the microfluidic chip which has approximately 56,320 capture chambers. Based on differences in cell size and deformability, each chamber ensures that small blood escape while larger CTCs of varying sizes are trapped and isolated in the chambers. In this report, we used the Celsee PREP100 to capture cancer cells spiked into normal donor blood samples. We were able to show that the device can capture as low as 10 cells with high reproducibility. The captured CTCs were retrieved from the microfluidic chip. The cell recovery rate of this back-flow procedure is 100% and the level of remaining background leukocytes is very low (about 300-400 cells). RNA from the retrieved cells are extracted and converted to cDNA, and gene expression analysis of selected cancer markers can be carried out by using RT-PCR assays. The sensitive and easy-to-use Celsee PREP100 system represents a promising technology for capturing and molecular characterization of CTCs.

Technical challenges in the isolation and analysis of circulating tumor cells

Increasing evidence suggests that cancer cells display dynamic molecular changes in response to systemic therapy. Circulating tumor cells (CTCs) in the peripheral blood represent a readily available source of cancer cells with which to measure this dynamic process. To date, a large number of strategies to isolate and characterize CTCs have been described. These techniques, however, each have unique limitations in their ability to sensitively and specifically detect these rare cells. In this review we focus on the technical limitations and pitfalls of the most common CTC isolation and detection strategies. Additionally, we emphasize the difficulties in correctly classifying rare cells as CTCs using common biomarkers. As for assays developed in the future, the first step must be a uniform and clear definition of the criteria for assigning an object as a CTC based on disease-specific biomarkers.

Recent advances in the biology of human circulating tumour cells and metastasis

The development of a metastatic disease is recognised as the cause of death of over 90% of patients diagnosed with cancer. Understanding the biological features of metastasis has been hampered for a long time by the difficulties to study widespread cancerous lesions in patients, and by the absence of reliable methods to isolate viable metastatic cells during disease progression. These difficulties negatively impact on our ability to develop new agents that are tailored to block the spread of cancer. Yet, recent advances in specialised devices for the isolation of circulating tumour cells (CTCs), hand-in-hand with technologies that enable single cell resolution interrogation of their genome and transcriptome, are now paving the way to understanding those molecular mechanisms that drive the formation of metastasis. In this review, we aim to summarise some of the latest discoveries in CTC biology in the context of several types of cancer, and to highlight those findings that have a potential to improve the clinical management of patients with metastatic cancer.

Stem-like features of cancer cells on their way to metastasis

More than 90 % of cancer-related deaths are due to the development of a systemic metastatic disease. Clearly, much remains to be understood about the biological principles that govern human cancer metastasis, aiming at the ambitious objective to decrease metastasis-related mortality in patients. For many years, research on metastasis has been conducted in great part on experimental mouse models, mainly because of the difficulties in sampling, longitudinal studies, and molecular interrogation of a human metastatic disease. However, recently, extraordinary advances in microfluidic technologies are allowing the isolation and characterization of human circulating tumor cells (CTCs) that escaped a primary tumor mass and are in the process of seeding a distant metastasis. Analysis of human CTCs has now revealed important features of cancer metastasis, such as the high metastatic potential of CTC-clusters compared to single CTCs, the dynamic expression of epithelial and mesenchymal markers on CTCs during treatment, and the possibility to culture CTCs from patients for a real-time and individualized testing of drug susceptibility. Nevertheless, several aspects of CTC biology remain unsolved, such as the characterization of the stem-like cell population among human CTCs. Here, we focus on describing the latest findings in the CTC field, and discuss them in the context of cancer stem cell biology. Defining the molecular features of those few metastasis-initiating, stem-like CTCs holds the exceptional promise to develop metastasis-tailored therapies for patients with cancer.

REVIEWERS

This article was reviewed by Elisa Cimetta, Luca Pellegrini and Sirio Dupont (nominated by LP).

Single-Cell Isolation of Circulating Tumor Cells from Whole Blood by Lateral Magnetophoretic Microseparation and Microfluidic Dispensing

This paper introduces a single-cell isolation technology for circulating tumor cells (CTCs) using a microfluidic device (the "SIM-Chip"). The SIM-Chip comprises a lateral magnetophoretic microseparator and a microdispenser as a two-step cascade platform. First, CTCs were enriched from whole blood by the lateral magnetophoretic microseparator based on immunomagnetic nanobeads. Next, the enriched CTCs were electrically identified by single-cell impedance cytometer and isolated as single cells using the microshooter. Using 200 μL of whole blood spiked with 50 MCF7 breast cancer cells, the analysis demonstrated that the single-cell isolation efficiency of the SIM-Chip was 82.4%, and the purity of the isolated MCF7 cells with respect to WBCs was 92.45%. The data also showed that the WBC depletion rate of the SIM-Chip was 2.5 × 10(5) (5.4-log). The recovery rates were around 99.78% for spiked MCF7 cells ranging in number from 10 to 90. The isolated single MCF7 cells were intact and could be used for subsequent downstream genetic assays, such as RT-PCR. Single-cell culture evaluation of the proliferation of MCF7 cells isolated by the SIM-Chip showed that 84.1% of cells at least doubled in 5 days. Consequently, the SIM-Chip could be used for single-cell isolation of rare target cells from whole blood with high purity and recovery without cell damage.

In patients with metastatic breast cancer the identification of circulating tumor cells in epithelial-to-mesenchymal transition is associated with a poor prognosis

BACKGROUND

Although recent models suggest that the detection of Circulating Tumor Cells (CTC) in epithelial-to-mesenchymal transition (EM CTC) might be related to disease progression in metastatic breast cancer (MBC) patients, current detection methods are not efficient in identifying this subpopulation of cells. Furthermore, the possible association of EM CTC with both clinicopathological features and prognosis of MBC patients has still to be demonstrated. Aims of this study were: first, to optimize a DEPArray-based protocol meant to identify, quantify and sort single, viable EM CTC and, subsequently, to test the association of EM CTC frequency with clinical data.

METHODS

This prospective observational study enrolled 56 MBC patients regardless of the line of treatment. Blood samples, depleted of CD45(pos) leukocytes, were stained with an antibody cocktail recognizing both epithelial and mesenchymal markers. Four CD45(neg) cell subpopulations were identified: cells expressing only epithelial markers (E CTC), cells co-expressing epithelial and mesenchymal markers (EM CTC), cells expressing only mesenchymal markers (MES) and cells negative for every tested marker (NEG). CTC subpopulations were quantified as both absolute cell count and relative frequency. The association of CTC subpopulations with clinicopathological features, progression free survival (PFS), and overall survival (OS) was explored by Wilcoxon-Mann-Whitney test and Univariate Cox Regression Analysis, respectively.

RESULTS

By employing the DEPArray-based strategy, we were able to assess the presence of cells pertaining to the above-described classes in every MBC patient. We observed a significant association between specific CD45(neg) subpopulations and tumor subtypes (e.g. NEG and triple negative), proliferation (NEG and Ki67 expression) and sites of metastatic spread (e.g. E CTC and bone; NEG and brain). Importantly, the fraction of CD45(neg) cells co-expressing epithelial and mesenchymal markers (EM CTC) was significantly associated with poorer PFS and OS, computed, this latter, both from the diagnosis of a stage IV disease and from the initial CTC assessment.

CONCLUSION

This study suggests the importance of dissecting the heterogeneity of CTC in MBC. Precise characterization of CTC could help in estimating both metastatization pattern and outcome, driving clinical decision-making and surveillance strategies.

Circulating Tumor Cells: A Window Into Tumor Development and Therapeutic Effectiveness

BACKGROUND

Circulating tumor cells (CTCs) are an important diagnostic tool for understanding the metastatic process and the development of cancer.

METHODS

This review covers the background, relevance, and potential limitations of CTCs as a measurement of cancer progression and how information derived from CTCs may affect treatment efficacy. It also highlights the difficulties of characterizing these rare cells due to the limited cell surface molecules unique to CTCs and each particular type of cancer.

RESULTS

The analysis of cancer in real time, through the measure of the number of CTCs in a " liquid" biopsy specimen, gives us the ability to monitor the therapeutic efficacy of treatments and possibly the metastatic potential of a tumor.

CONCLUSIONS

Through novel and innovative techniques yielding encouraging results, including microfluidic techniques, isolating and molecularly analyzing CTCs are becoming a reality. CTCs hold promise for understanding how tumors work and potentially aiding in their demise.

Development of an Automated and Sensitive Microfluidic Device for Capturing and Characterizing Circulating Tumor Cells (CTCs) from Clinical Blood Samples

Current analysis of circulating tumor cells (CTCs) is hindered by sub-optimal sensitivity and specificity of devices or assays as well as lack of capability of characterization of CTCs with clinical biomarkers. Here, we validate a novel technology to enrich and characterize CTCs from blood samples of patients with metastatic breast, prostate and colorectal cancers using a microfluidic chip which is processed by using an automated staining and scanning system from sample preparation to image processing. The Celsee system allowed for the detection of CTCs with apparent high sensitivity and specificity (94% sensitivity and 100% specificity). Moreover, the system facilitated rapid capture of CTCs from blood samples and also allowed for downstream characterization of the captured cells by immunohistochemistry, DNA and mRNA fluorescence in-situ hybridization (FISH). In a subset of patients with prostate cancer we compared the technology with a FDA-approved CTC device, CellSearch and found a higher degree of sensitivity with the Celsee instrument. In conclusion, the integrated Celsee system represents a promising CTC technology for enumeration and molecular characterization.

Biomarker detection for disease diagnosis using cost-effective microfluidic platforms

Early and timely detection of disease biomarkers can prevent the spread of infectious diseases, and drastically decrease the death rate of people suffering from different diseases such as cancer and infectious diseases. Because conventional diagnostic methods have limited application in low-resource settings due to the use of bulky and expensive instrumentation, simple and low-cost point-of-care diagnostic devices for timely and early biomarker diagnosis is the need of the hour, especially in rural areas and developing nations. The microfluidics technology possesses remarkable features for simple, low-cost, and rapid disease diagnosis. There have been significant advances in the development of microfluidic platforms for biomarker detection of diseases. This article reviews recent advances in biomarker detection using cost-effective microfluidic devices for disease diagnosis, with the emphasis on infectious disease and cancer diagnosis in low-resource settings. This review first introduces different microfluidic platforms (e.g. polymer and paper-based microfluidics) used for disease diagnosis, with a brief description of their common fabrication techniques. Then, it highlights various detection strategies for disease biomarker detection using microfluidic platforms, including colorimetric, fluorescence, chemiluminescence, electrochemiluminescence (ECL), and electrochemical detection. Finally, it discusses the current limitations of microfluidic devices for disease biomarker detection and future prospects.

Circulating tumor cell isolation: the assets of filtration methods with polycarbonate track-etched filters

Circulating tumor cells (CTCs) arise from primary or secondary tumors and enter the bloodstream by active or passive intravasation. Given the low number of CTCs, enrichment is necessary for detection. Filtration methods are based on selection of CTCs by size using a filter with 6.5 to 8 µm pores. After coloration, collected CTCs are evaluated according to morphological criteria. Immunophenotyping and fluorescence in situ hybridization techniques may be used. Selected CTCs can also be cultivated in vitro to provide more material. Analysis of genomic mutations is difficult because it requires adapted techniques due to limited DNA materials. Filtration-selected CTCs have shown prognostic value in many studies but multicentric validating trials are mandatory to strengthen this assessment. Other clinical applications are promising such as follow-up, therapy response prediction and diagnosis. Microfluidic emerging systems could optimize filtration-selected CTCs by increasing selection accuracy.