Portable filter-based microdevice for detection and characterization of circulating tumor cells

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.

Nanotechnology-Based Strategies for Early Cancer Diagnosis Using Circulating Tumor Cells as a Liquid Biopsy

Circulating tumor cells (CTCs) are cancer cells that shed from a primary tumor and circulate in the bloodstream. As a form of “tumor liquid biopsy”, CTCs provide important information for the mechanistic investigation of cancer metastasis and the measurement of tumor genotype evolution during treatment and disease progression. However, the extremely low abundance of CTCs in the peripheral blood and the heterogeneity of CTCs make their isolation and characterization major technological challenges. Recently, nanotechnologies have been developed for sensitive CTC detection; such technologies will enable better cell and molecular characterization and open up a wide range of clinical applications, including early disease detection and evaluation of treatment response and disease progression. In this review, we summarize the nanotechnology-based strategies for CTC isolation, including representative nanomaterials (such as magnetic nanoparticles, gold nanoparticles, silicon nanopillars, nanowires, nanopillars, carbon nanotubes, dendrimers, quantum dots, and graphene oxide) and microfluidic chip technologies that incorporate nanoroughened surfaces and discuss their key challenges and perspectives in CTC downstream analyses, such as protein expression and genetic mutations that may reflect tumor aggressiveness and patient outcome.

Reducing WBC background in cancer cell separation products by negative acoustic contrast particle immuno-acoustophoresis

Cancer cells display acoustic properties enabling acoustophoretic separation from white blood cells (WBCs) with 2-3 log suppression of the WBC background. However, a subset of WBCs has overlapping acoustic properties with cancer cells, which is why label-free acoustophoretic cancer cell isolation needs additional purification prior to analysis. This paper reports for the first time a proof of concept for continuous flow acoustophoretic negative selection of WBCs from cancer cells using negative acoustic contrast elastomeric particles (EPs) activated with CD45-antibodies that specifically bind to WBCs. The EP/WBC complexes align at the acoustic pressure anti-nodes along the channel walls while unbound cancer cells focus to the pressure node in the channel center, enabling continuous flow based depletion of WBC background in a cancer cell product. The method does not provide a single process solution for the CTC separation challenge, but provides an elegant part to a multi-step process by further reducing the WBC background in cancer cell separation products derived from an initial step of label-free acoustophoresis. We report the recorded performance of the negative selection immuno-acoustophoretic WBC depletion and cancer cell recovery. To eliminate the negative impact of the separation due to the known problems of aggregation of negative acoustic contrast particles along the sidewalls of the acoustophoresis channel and to enable continuous separation of EP/WBC complexes from cancer cells, a new acoustic actuation method has been implemented where the ultrasound frequency is scanned (1.991MHz ± 100 kHz, scan rate 200 kHz ms^-1). Using this frequency scanning strategy EP/WBC complexes were acoustophoretically separated from mixtures of WBCs spiked with breast and prostate cancer cells (DU145 and MCF-7). An 86-fold (MCF-7) and 52-fold (DU145) reduction of WBCs in the cancer cell fractions were recorded with separation efficiencies of 98.6% (MCF-7) and 99.7% (DU145) and cancer cell recoveries of 89.8% (MCF-7) and 85.0% (DU145).

Personalizing Therapy for Metastatic Prostate Cancer: The Role of Solid and Liquid Tumor Biopsies

Although biopsies of metastatic prostate cancer are rarely undertaken in the clinical setting, there is increasing interest in developing personalized approaches to therapy by taking into account the genetic and phenotypic changes in an individual tumor. Indeed, analysis of metastatic prostate tumors can predict sensitivity to agents that inhibit DNA repair and resistance to novel hormonal agents, such as abiraterone and enzalutamide, and identify phenotypic changes, such as neuroendocrine differentiation, that have important clinical implications. Although obtaining metastatic tumor tissue is necessary for this genomic and molecular profiling, knowing when to biopsy, selecting the appropriate metastatic lesion, and interpreting the results are major challenges facing clinicians today. In this article, we discuss the rationale for obtaining metastatic tumor tissue, review the bioinformatic approach to analyzing these specimens, discuss the timing and approach to solid and liquid tumor biopsies, review the challenges associated with obtaining and acting on clinically relevant results, and discuss opportunities for the future.

Clinical-Scale Cell-Surface-Marker Independent Acoustic Microfluidic Enrichment of Tumor Cells from Blood

Enumeration of circulating tumor cells (CTCs) predicts overall survival and treatment response in metastatic cancer, but as many commercialized assays isolate CTCs positive for epithelial cell markers alone, CTCs with little or no epithelial cell adhesion molecule (EpCAM) expression stay undetected. Therefore, CTC enrichment and isolation by label-free methods based on biophysical rather than biochemical properties could provide a more representative spectrum of CTCs. Here, we report on a clinical-scale automated acoustic microfluidic platform processing 5 mL of erythrocyte-depleted paraformaldehyde (PFA)-fixed blood (diluted 1:2) at a flow rate of 75 μL/min, recovering 43/50 (86 ± 2.3%) breast cancer cell line cells (MCF7), with 0.11% cancer cell purity and 162-fold enrichment in close to 2 h based on intrinsic biophysical cell properties. Adjustments of the voltage settings aimed at higher cancer cell purity in the central outlet provided 0.72% cancer cell purity and 1445-fold enrichment that resulted in 62 ± 8.7% cancer cell recovery. Similar rates of cancer-cell recovery, cancer-cell purity, and fold-enrichment were seen with both prostate cancer (DU145, PC3) and breast cancer (MCF7) cell line cells. We identified eosinophil granulocytes as the predominant white blood cell (WBC) contaminant (85%) in the enriched cancer-cell fraction. Processing of viable cancer cells in erythrocyte-depleted blood provided slightly reduced results as to fixed cells (77% cancer cells in the enriched cancer cell fraction, with 0.2% WBC contamination). We demonstrate feasibility of enriching either PFA-fixed or viable cancer cells with a clinical-scale acoustic microfluidic platform that can be adjusted to meet requirements for either high cancer-cell recovery or higher purity and can process 5 mL blood samples in close to 2 h.

Frequency and clinical impact of preoperative circulating tumor cells in resectable non-metastatic lung adenocarcinomas

OBJECTIVES

Despite successful surgery, 30-50% of patients with resectable non-small cell lung cancer develop tumor recurrence within 5 years of surgery.

MATERIALS AND METHODS

In this prospective study, we performed CTC enumerations in 40 patients with non-metastatic lung adenocarcinoma (NMLA) using a size-based microfilter. Additionally, cfDNA isolated from plasma was analyzed in 35 out of 40 patients.

RESULTS

CTCs were identified in 15 out of 40 patients (37.5%) with a range of 1-44 cells, whereas mutated cfDNA was only detected in 3 out of 35 patients (8.6%). Disease-free survival (DFS) was significantly associated with CTC positivity (log-rank p=0.025), grading (log-rank p=0.019), tumor stage (log-rank p=0.025) and lymph node status (log-rank p=0.029). Multivariate analysis, including tumor stage and grading, showed that CTC positivity (p=0.006), grading (0.039) and tumor stage (p=0.022) were independently associated with DFS.

CONCLUSION

Our study found that microfilter-based CTC enumeration in NMLA patients is an independent predictor of worse DFS. The used NGS-based cfDNA characterization had limited sensitivity to be clinically informative in our study cohort. CTC assessment before surgery can thus identify NMLA patients at high risk of disease recurrence.

Multigene methylation analysis of enriched circulating tumor cells associates with poor progression-free survival in metastatic breast cancer patients

Blood-based biomarkers such as circulating tumor cells (CTCs) provide dynamic real-time assessment of molecular tumor characteristics beyond the primary tumor. The aim of this study was to evaluate the feasibility of a size-based microfilter to assess multigene methylation analysis of enriched CTCs in a prospective proof-of principle study. We examined the quantitative methylation status of nine genes (AKR1B1, BMP6, CST6, HOXB4, HIST1H3C, ITIH5, NEUROD1, RASSF1, SOX17) in enriched CTCs from metastatic breast cancer patients. Feasibility and clinical performance testing were assessed in a test set consisting of 37 patients and 25 healthy controls. With established cut-off values from the healthy control group, methylation of enriched CTCs was detected in at least one gene in 18/37 patients (48.6%), while 97.8% of all control samples were unmethylated. Patients with CTCs unmethylated for CST6, ITIH5, or RASSF1 showed significantly longer PFS compared to patients with corresponding enriched methylated CTCs. This proof-of-principle study shows the feasibility of a size-based microfilter to enrich and analyze multigene methylation profile of CTCs from metastatic breast cancer patients. For the first time, we report that multigene methylation analysis of enriched CTCs provides prognostic information in metastatic breast cancer patients.

Label-free ferrohydrodynamic cell separation of circulating tumor cells

Circulating tumor cells (CTCs) have significant implications in both basic cancer research and clinical applications. To address the limited availability of viable CTCs for fundamental and clinical investigations, effective separation of extremely rare CTCs from blood is critical. Ferrohydrodynamic cell separation (FCS), a label-free method that conducted cell sorting based on cell size difference in biocompatible ferrofluids, has thus far not been able to enrich low-concentration CTCs from cancer patients' blood because of technical challenges associated with processing clinical samples. In this study, we demonstrated the development of a laminar-flow microfluidic FCS device that was capable of enriching rare CTCs from patients' blood in a biocompatible manner with a high throughput (6 mL h^-1) and a high rate of recovery (92.9%). Systematic optimization of the FCS devices through a validated analytical model was performed to determine optimal magnetic field and its gradient, ferrofluid properties, and cell throughput that could process clinically relevant amount of blood. We first validated the capability of the FCS devices by successfully separating low-concentration (∼100 cells per mL) cancer cells using six cultured cell lines from undiluted white blood cells (WBCs), with an average 92.9% cancer cell recovery rate and an average 11.7% purity of separated cancer cells, at a throughput of 6 mL per hour. Specifically, at ∼100 cancer cells per mL spike ratio, the recovery rates of cancer cells were 92.3 ± 3.6% (H1299 lung cancer), 88.3 ± 5.5% (A549 lung cancer), 93.7 ± 5.5% (H3122 lung cancer), 95.3 ± 6.0% (PC-3 prostate cancer), 94.7 ± 4.0% (MCF-7 breast cancer), and 93.0 ± 5.3% (HCC1806 breast cancer), and the corresponding purities of separated cancer cells were 11.1 ± 1.2% (H1299 lung cancer), 10.1 ± 1.7% (A549 lung cancer), 12.1 ± 2.1% (H3122 lung cancer), 12.8 ± 1.6% (PC-3 prostate cancer), 11.9 ± 1.8% (MCF-7 breast cancer), and 12.2 ± 1.6% (HCC1806 breast cancer). Biocompatibility study on H1299 cell line and HCC1806 cell line showed that separated cancer cells had excellent short-term viability, normal proliferation and unaffected key biomarker expressions. We then demonstrated the enrichment of CTCs in blood samples obtained from two patients with newly diagnosed advanced non-small cell lung cancer (NSCLC). While still at its early stage of development, FCS could become a complementary tool for CTC separation for its high recovery rate and excellent biocompatibility, as well as its potential for further optimization and integration with other separation methods.

On-chip cell labelling and washing by capture and release using microfluidic trap arrays

Flow cytometry analysis requires a large amount of isolated, labelled, and purified cells for accurate results. To address the demand for a large quantity of cells prepared in a timely manner, we describe a novel microfluidic trap structure array for on-chip cell labelling, such as intracellular and extracellular labelling, and subsequent washing and release of cells. Each device contains [Formula: see text] trap structures, which made the preparation of large numbers of cells [Formula: see text] possible. The structure has a streamlined shape, which minimizes clogging of cells in capture and release steps. The trap structure arrays are built and tested using leukocytes, with different load flow speeds, incubation times, and release flow speeds. ∼85% of cells are captured independent of the input flow speed. The release efficiency depends on the incubation time, with over ∼80% of captured cells released for up to 20 min incubation, and on-chip labelling and washing with STYO13 are demonstrated. Qualitative models are developed as guidance for designing the proposed trap structure and to explain the increased performance over previous approaches.

Label-free Rapid Viable Enrichment of Circulating Tumor Cell by Photosensitive Polymer-based Microfilter Device

We present a clinical device for simple, rapid, and viable isolation of circulating tumor cells (CTCs) from cancer patient bloods. In spite of the clinical importance of CTCs, the lack of easy and non-biased isolation methods is a big hurdle for implementing CTC into clinical use. The present device made of photosensitive polymer was designed to attach to conventional syringe to isolate the CTCs at minimal resources. Its unique tapered-slits on the filter are capable not only to isolate the cell based on their size and deformability, but also to increase sample flow rate, thus achieving label-free rapid viable CTC isolation. We verified our device performance using 9 different types of cancer cells at the cell concentration from 5 to 100cells/ml, showing that the device capture 77.7% of the CTCs while maintaining their viability of 80.6%. We extended our study using the 18 blood samples from lung, colorectal, pancreatic and renal cancer patients and captured 1-172 CTCs or clustered CTCs by immunofluorescent or immunohistochemical staining. The captured CTCs were also molecularly assayed by RT-PCR with three cancer-associated genes (CK19, EpCAM, and MUC1). Those comprehensive studies proved to use our device for cancer study, thereby inaugurating further in-depth CTC-based clinical researches.

Materials and microfluidics: enabling the efficient isolation and analysis of circulating tumour cells

We present a critical review of microfluidic technologies and material effects on the analyses of circulating tumour cells (CTCs) selected from the peripheral blood of cancer patients. CTCs are a minimally invasive source of clinical information that can be used to prognose patient outcome, monitor minimal residual disease, assess tumour resistance to therapeutic agents, and potentially screen individuals for the early diagnosis of cancer. The performance of CTC isolation technologies depends on microfluidic architectures, the underlying principles of isolation, and the choice of materials. We present a critical review of the fundamental principles used in these technologies and discuss their performance. We also give context to how CTC isolation technologies enable downstream analysis of selected CTCs in terms of detecting genetic mutations and gene expression that could be used to gain information that may affect patient outcome.

Biological and Molecular Characterization of Circulating Tumor Cells: A Creative Strategy for Precision Medicine?

Circulating tumor cells (CTCs) are a group of rare cells disseminated from either primary or metastatic tumors into the blood stream. CTCs are considered to be the precursor of cancer metastasis. As a critical component of liquid biopsies, CTCs are a unique tool to understand the formation of metastasis and a valuable source of information on intratumor heterogeneity. Much effort has been invested in technologies for the detection of CTCs because they are rare cells among the vast number of blood cells. Studies in various cancers have repeatedly demonstrated that increased CTC counts prior to or during treatment are significantly associated with poor outcomes. In the new era of precision medicine, the study of CTCs reaches far beyond detection and counting. The rapidly growing field of analytical platforms for rare-cell analysis allows in-depth characterization of CTCs at the bulk cell and single-cell level. Genetic profiling of CTCs may provide an insight into the real-time tumor status, may allow the monitoring and evaluation of treatment response in clinical routine, and may lead to the development of novel therapeutic targets as well.

Circulating Tumor Cells: Moving Biological Insights into Detection

Circulating tumor cells (CTCs) have shown promising potential as liquid biopsies that facilitate early detection, prognosis, therapeutic target selection and monitoring treatment response. CTCs in most cancer patients are low in abundance and heterogeneous in morphological and phenotypic profiles, which complicate their enrichment and subsequent characterization. Several methodologies for CTC enrichment and characterization have been developed over the past few years. However, integrating recent advances in CTC biology into these methodologies and the selection of appropriate enrichment and characterization methods for specific applications are needed to improve the reliability of CTC biopsies. In this review, we summarize recent advances in the studies of CTC biology, including the mechanisms of their generation and their potential forms of existence in blood, as well as the current CTC enrichment technologies. We then critically examine the selection of methods for appropriately enriching CTCs for further investigation of their clinical applications.

Fluorescence Analysis of Vitamin D Receptor Status of Circulating Tumor Cells (CTCS) in Breast Cancer: From Cell Models to Metastatic Patients

The Vitamin D receptor (VDR) expressed in normal breast tissue and breast tumors has been suggested as a new prognostic biomarker in breast cancer (BC). Besides, increasing evidence supports the view that the detection of circulating tumor cells (CTCs) predicts outcome in early and metastatic BC. Consequently, an evaluation of VDR expression in the CTCs of BC patients may allow optimization of their treatment. As an attempt to profile and subtype the CTCs of metastatic patients, we established an innovative fluorescence technique using nine BC cell lines to visualize, define, and compare their individual VDR status. Afterwards, we tested the CTC presence and VDR expression in blood samples (cytospins) collected from 23 metastatic BC patients. The results demonstrated major differences in the VDR levels among the nine cell lines, and VDR positive CTCs were detected in 46% of CTC-positive patients, with a total of 42 CTCs individually analyzed. Due to the limited number of patients in this study, no correlation between VDR expression and BC subtype classification (according to estrogen receptor (ER), progesterone receptor (PR) and HER2) could be determined, but our data support the view that VDR evaluation is a potential new prognostic biomarker to help in the optimization of therapy management for BC patients.

Identification and Quantitation of Circulating Tumor Cells

Circulating tumor cells (CTCs) are shed from the primary tumor into the circulatory system and act as seeds that initiate cancer metastasis to distant sites. CTC enumeration has been shown to have a significant prognostic value as a surrogate marker in various cancers. The widespread clinical utility of CTC tests, however, is still limited due to the inherent rarity and heterogeneity of CTCs, which necessitate robust techniques for their efficient enrichment and detection. Significant recent advances have resulted in technologies with the ability to improve yield and purity of CTC enrichment as well as detection sensitivity. Current efforts are largely focused on the translation and standardization of assays to fully realize the clinical utility of CTCs. In this review, we aim to provide a comprehensive overview of CTC enrichment and detection techniques with an emphasis on novel approaches for rapid quantification of CTCs.

Isolation, Detection, and Quantification of Cancer Biomarkers in HPV-Associated Malignancies

Human Papillomavirus (HPV) infection has been recognized as the main etiologic factor in the development of various cancers including penile, vulva, oropharyngeal and cervical cancers. In the development of cancer, persistent HPV infections induce E6 and E7 oncoproteins, which promote cell proliferation and carcinogenesis resulting elevated levels of host antibodies (e.g., anti-HPV16 E7 antibody). Currently, these cancers are clinically diagnosed using invasive biopsy-based tests, which are performed only in centralized labs by experienced clinical staff using time-consuming and expensive tools and technologies. Therefore, these obstacles constrain their utilization at primary care clinics and in remote settings, where resources are limited. Here, we present a rapid, inexpensive, reliable, easy-to-use, customized immunoassay platform following a microfluidic filter device to detect and quantify anti-HPV16 E7 antibodies from whole blood as a non-invasive assisting technology for diagnosis of HPV-associated malignancies, especially, at primary healthcare and remote settings. The platform can detect and quantify anti-HPV16 E7 antibody down to 2.87 ng/mL. We further validated our immunoassay in clinical patient samples and it provided significantly high responses as compared to control samples. Thus, it can be potentially implemented as a pretesting tool to identify high-risk groups for broad monitoring of HPV-associated cancers in resource-constrained settings.

Antibody-independent capture of circulating tumor cells of non-epithelial origin with the ApoStream® system

Circulating tumor cells (CTCs) are increasingly employed for research and clinical monitoring of cancer, though most current methods do not permit the isolation of non-epithelial tumor cells. Furthermore, CTCs isolated with antibody-dependent methods are not suitable for downstream experimental uses, including in vitro culturing and implantation in vivo. In the present study, we describe the development, validation, and transfer across laboratories of a new antibody-independent device for the enrichment of CTCs from blood samples of patients with various cancer diagnoses. The ApoStream^® device uses dielectrophoresis (DEP) field-flow assist to separate non-hematopoietic cells from the peripheral blood mononuclear fraction by exposing cells in a laminar flow stream to a critical alternating current frequency. The ApoStream^® device was calibrated and validated in a formal cross-laboratory protocol using 3 different cancer cell lines spanning a range of distinct phenotypes (A549, MDA-MB-231, and ASPS-1). In spike-recovery experiments, cancer cell recovery efficiencies appeared independent of spiking level and averaged between 68% and 55%, depending on the cell line. No inter-run carryover was detected in control samples. Moreover, the clinical-readiness of the device in the context of non-epithelial cancers was evaluated with blood specimens from fifteen patients with metastatic sarcoma. The ApoStream^® device successfully isolated CTCs from all patients with sarcomas examined, and the phenotypic heterogeneity of the enriched cells was demonstrated by fluorescence in situ hybridization or with multiplex immunophenotyping panels. Therefore, the ApoStream^® technology expands the clinical utility of CTC evaluation to mesenchymal cancers.

Highly-sensitive capture of circulating tumor cells using micro-ellipse filters

Circulating tumor cells (CTCs) detection, enumeration and characterization with microfluidic chips has critical significance in cancer prognosis offering a non-invasive “liquid biopsy”. Based on physical differences of size and deformability, we explore micro-ellipse filters consisting of microfuidic slits in series gradually narrowed. Slender tunnels sensitively capture tumor cells with slim chance to escape. Tumor cells could reside at capture sites organized by arrays of micro-ellipse microposts enduring less stress. Circular elliptical microstructures produce smooth flow minimally reducing any damage. “Air Suction” could extremely shorten capture. Capture efficiency comes out to be a robust yield of 90% and percentage obeys Gaussian distribution at various stages. With rare number accurately enumerated, micro-Ellipse filters have been tested high efficiently capturing tumor cells in both whole and lysed blood. To clinically validate the device, the microfluidic chip was utilized to identify and capture CTCs from metastatic breast, colon and non-small-cell lung (NSCLC) cancer patients. CTCs were detected positive in all samples with 4 patients having more than 20 CTCs. Those sensitive results are consistent with theoretical expectation. Efficient micro-ellipse filters enable clinical enumeration of metastasis, on-chip anti-cancer drug responses and biological molecular analysis.

Rapid imaging and detection of circulating tumor cells using a wide-field fluorescence imaging system

Circulating tumor cells (CTCs) provide potentially accessible in vivo sources of metastatic cancer cells. As such, considerable focus has been placed on analyzing the genetics of single-CTCs. Prior to these analyses, however, CTCs must first be detected within the blood samples of cancer patients. Current methods for detection of CTCs by fluorescence microscopy require the analysis of hundreds of images per blood sample, making this a time-consuming process that creates a bottleneck in CTC analysis. In this study, we therefore developed a wide-field fluorescence imaging system for rapid CTC detection. For these analyses, CTCs were first isolated using the microcavity array (MCA), a micro-sized filter for CTC recovery that separates cells based on differences in cell size and deformability. Notably, the proposed imaging system enabled rapid (∼10 s) visualization of all stained cells within the 6 mm × 6 mm MCA field via one-shot imaging. Furthermore, the morphology of the cells in the resulting images accurately reflected that observed by conventional microscopy. In total, isolation and detection of CTCs using the MCA combined with our novel wide-field fluorescence imaging system was achieved within 1 h. Thus, our proposed system will provide rapid CTC detection system.

Ethanol-dispersed and antibody-conjugated polymer nanofibers for the selective capture and 3-dimensional culture of EpCAM-positive cells

Electrospun and ethanol-dispersed polystyrene-poly(styrene-co-maleic anhydride) (PS-PSMA) nanofibers (NFs) were used as a platform for the selective capture and three-dimensional culture of EpCAM-positive cells in cell culture medium and whole blood. The NFs were treated with streptavidin to facilitate bond formation between the amino groups of streptavidin and the maleic anhydride groups of the NFs. A biotinylated anti-EpCAM monoclonal antibody (mAb) was attached to the streptavidin-conjugated NFs via the selective binding of streptavidin and biotin. Upon simple mixing and shaking with EpCAM-positive cancer cells in a wide concentration range from 10 to 1000,000 cells per 10mL, the mAb-attached NFs (mAb-NFs) captured the Ep-CAM positive cells in an efficiency of 59%-67% depending on initial cell concentrations, with minor mechanical capture of 14%-36%. Captured cells were directly cultured, forming cell aggregates, in the NF matrix, which ensures the cell proliferation and follow-up analysis. Furthermore, the capture capacity of mAb-NFs was assessed in the presence of whole blood and blood lysates, indicating cluster formation that captured target cells. It is anticipated that the antibody-attached NFs can be employed for the capture and analysis of very rare EpCAM positive circulating cancer cells.

Integrating liquid biopsies into the management of cancer

During cancer progression and treatment, multiple subclonal populations of tumour cells compete with one another, with selective pressures leading to the emergence of predominant subclones that replicate and spread most proficiently, and are least susceptible to treatment. At present, the molecular landscapes of solid tumours are established using surgical or biopsy tissue samples. Tissue-based tumour profiles are, however, subject to sampling bias, provide only a snapshot of tumour heterogeneity, and cannot be obtained repeatedly. Genomic profiles of circulating cell-free tumour DNA (ctDNA) have been shown to closely match those of the corresponding tumours, with important implications for both molecular pathology and clinical oncology. Analyses of circulating nucleic acids, commonly referred to as 'liquid biopsies', can be used to monitor response to treatment, assess the emergence of drug resistance, and quantify minimal residual disease. In addition to blood, several other body fluids, such as urine, saliva, pleural effusions, and cerebrospinal fluid, can contain tumour-derived genetic information. The molecular profiles gathered from ctDNA can be further complemented with those obtained through analysis of circulating tumour cells (CTCs), as well as RNA, proteins, and lipids contained within vesicles, such as exosomes. In this Review, we examine how different forms of liquid biopsies can be exploited to guide patient care and should ultimately be integrated into clinical practice, focusing on liquid biopsy of ctDNA - arguably the most clinically advanced approach.

Enrichment and single-cell analysis of circulating tumor cells

Up to 90% of cancer-related deaths are caused by metastatic cancer. Circulating tumor cells (CTCs), a type of cancer cell that spreads through the blood after detaching from a solid tumor, are essential for the establishment of distant metastasis for a given cancer. As a new type of liquid biopsy, analysis of CTCs offers the possibility to avoid invasive tissue biopsy procedures with practical implications for diagnostics. The fundamental challenges of analyzing and profiling CTCs are the extremely low abundances of CTCs in the blood and the intrinsic heterogeneity of CTCs. Various technologies have been proposed for the enrichment and single-cell analysis of CTCs. This review aims to provide in-depth insights into CTC analysis, including various techniques for isolation of CTCs with capture methods based on physical and biochemical principles, and single-cell analysis of CTCs at the genomic, proteomic and phenotypic level, as well as current developmental trends and promising research directions.

Detection of Circulating Tumour Cells in Urothelial Cancers and Clinical Correlations: Comparison of Two Methods

Circulating tumour cells (CTC) are identified exploiting their protein/gene expression patterns or distinct size compared to blood cells. Data on CTC in bladder cancer (BC) are still scarce. We comparatively analyzed CTC enrichment by AdnaTest ProstateCancerSelect (AT) and ScreenCell®Cyto (SC) kits, combined with identification by EPCAM, MUC1, and ERBB2 expression and by cytological criteria, respectively, in 19 nonmetastatic (M₀) and 47 metastatic (M₊) BC patients, at baseline (T₀) and during treatment (T₁). At T₀, CTC positivity rates by AT were higher in M₊ compared to M₀ cases (57.4% versus 25%, p = 0.041). EPCAM was detected in 75% of CTC-positive samples by AT, showing increasing expression levels from T₀ to T₁ (median (interquartile range, IQR): 0.18 (0.07-0.42) versus 0.84 (0.33-1.84), p = 0.005) in M₊ cases. Overall, CTC positivity by SC was around 80% regardless of clinical setting and time point of analysis, except for a lower occurrence at T₁ in M₀ cases. At T₀, circulating tumour microemboli were more frequently (25% versus 8%) detected and more numerous in M₊ compared to M₀ patients. The approach used for CTC detection impacts the outcome of CTC studies. Further investigations are required to clarify the clinical validity of AT and SC in specific BC clinical contexts.

Evaluating a novel dimensional reduction approach for mechanical fractionation of cells using a tandem flexible micro spring array (tFMSA)

We present a novel methodology to establish experimental models for the rational design of cell fractionation based on physical properties of cells. Label-free microfluidic separation of cells based on size is a widely employed technique. However, close observation reveals that cell capture results cannot be explained by cell sizes alone. This is particularly apparent with viable cell fractionation, where cells retain their native deformability. We have developed a principal size cutoff (PSC) model based on the analysis of size distribution and size-based filtration efficiency for cell populations. The goal of this analysis is to use an unbiased approach to achieve dimensional reduction of deformability and other mechanical properties that affect cell capture. The PSC model provides a single calibrated principal size component that may be compared directly to device gap width, which is the critical dimension for cell filtration. The PSC model was evaluated experimentally using a tandem flexible micro spring array (tFMSA) device made of parylene filtration elements applied within micro-molded polydimethylsiloxane (PDMS) chambers. In the tFMSA device, a mixture of cells is sequentially passed through individual filters with decreasing gap widths to allow size-based selection. We applied this method to demonstrate viable separation of subgroups of cells with different mechanical properties from complex mixtures, including fractionation according to cancer cell type, cell cycle stage, cell viability status, and leukocyte nuclear phenotype. The PSC methodology and tFMSA device can advance a better understanding of complex factors affecting mechanical cell fractionation and provide a miniature platform for obtaining rationally designed cell fractions for biomedical applications.

Aptamer-functionalized nano/micro-materials for clinical diagnosis: isolation, release and bioanalysis of circulating tumor cells

Detection of rare circulating tumor cells (CTCs) in peripheral blood is a challenging, but necessary, task in order to diagnose early onset of metastatic cancer and to monitor treatment efficacy. Over the last decade, step-up produced aptamers have attracted great attention in clinical diagnosis. They have offered great promise for a broader range of cell-specific recognition and isolation. In particular, aptamer-functionalized magnetic particles for selective extraction of target CTCs have shown reduced damage to cells and relatively simple operation. Also, efforts to develop aptamer-functionalized microchannel/microstructures able to efficiently isolate target CTCs are continuing, and these efforts have brought more advanced geometrically designed substrates. Various aptamer-mediated cell release techniques are being developed to enable subsequent biological studies. This article reviews some of these advances in aptamer-functionalized nano/micro-materials for CTCs isolation and methods for releasing captured CTCs from aptamer-functionalized surfaces. Biological studies of CTCs after release are also discussed.

Highly Selective Capture Surfaces on Medical Wires for Fishing Tumor Cells in Whole Blood

The detection of circulating tumor cells (CTCs) in the blood of cancer patients is a challenging task. CTCs are, especially at the early stages of cancer development, extremely rare cells hidden in a vast background of regular blood cells. We describe a new strategy for the isolation of CTCs from whole blood. The key component is a medical wire coated with a multilayer assembly that allows highly specific capture of EpCAM (epithelial cell adhesion molecule) positive CTCs from blood. The assembly is generated in a layer-by-layer fashion through photochemically induced C,H insertion reactions and consists of a protective layer, which shields the contacting solution from the metal, a protein resistant layer, which prevents nonspecific interactions with proteins and a layer containing the EpCAM antibodies. In vitro experiments show that these surfaces can capture tumor cells from whole blood with enrichment factors (specifically vs nonspecifically bound cells) of up to about 3000 compared to the number of leucocytes in the blood. The purity of the isolated cells is greater than 90%. After "fishing" them from the blood, the cells, still bound to the wire, can be genetically analyzed. This demonstrates that this strategy might prove useful for next generation sequencing.

Technical Insights into Highly Sensitive Isolation and Molecular Characterization of Fixed and Live Circulating Tumor Cells for Early Detection of Tumor Invasion

Circulating Tumor Cells (CTC) and Circulating Tumor Microemboli (CTM) are Circulating Rare Cells (CRC) which herald tumor invasion and are expected to provide an opportunity to improve the management of cancer patients. An unsolved technical issue in the CTC field is how to obtain highly sensitive and unbiased collection of these fragile and heterogeneous cells, in both live and fixed form, for their molecular study when they are extremely rare, particularly at the beginning of the invasion process. We report on a new protocol to enrich from blood live CTC using ISET^® (Isolation by SizE of Tumor/Trophoblastic Cells), an open system originally developed for marker-independent isolation of fixed tumor cells. We have assessed the impact of our new enrichment method on live tumor cells antigen expression, cytoskeleton structure, cell viability and ability to expand in culture. We have also explored the ISET^®in vitro performance to collect intact fixed and live cancer cells by using spiking analyses with extremely low number of fluorescent cultured cells. We describe results consistently showing the feasibility of isolating fixed and live tumor cells with a Lower Limit of Detection (LLOD) of one cancer cell per 10 mL of blood and a sensitivity at LLOD ranging from 83 to 100%. This very high sensitivity threshold can be maintained when plasma is collected before tumor cells isolation. Finally, we have performed a comparative next generation sequencing (NGS) analysis of tumor cells before and after isolation from blood and culture. We established the feasibility of NGS analysis of single live and fixed tumor cells enriched from blood by our system. This study provides new protocols for detection and characterization of CTC collected from blood at the very early steps of tumor invasion.

A surface tension magnetophoretic device for rare cell isolation and characterization

The cancer community continues to search for an efficient and cost-effective technique to isolate and characterize circulating cells (CTCs) as a 'real-time liquid biopsy'. Existing methods to isolate and analyze CTCs require various transfer, wash, and staining steps that can be time consuming, expensive, and led to the loss of rare cells. To overcome the limitations of existing CTC isolation strategies, we have developed an inexpensive 'lab on a chip' device for the enrichment, staining, and analysis of rare cell populations. This device utilizes immunomagnetic positive selection of antibody-bound cells, isolation of cells through an immiscible interface, and filtration. The isolated cells can then be stained utilizing immunofluorescence or used for other downstream detection methods. We describe the construction and initial preclinical testing of the device. Initial tests suggest that the device may be well suited for the isolation of CTCs and could allow the monitoring of cancer progression and the response to therapy over time.

Enhancement of isolation sensitivity for the viable heterogeneous circulating tumor cells swelled by hypo-osmotic pressure

We have applied a hypo-osmotic gradient for enhancing the isolation of viable heterogeneous circulating tumor cells.

Fourier Ptychographic Microscopy for Rapid, High-Resolution Imaging of Circulating Tumor Cells Enriched by Microfiltration

Examining the hematogenous compartment for evidence of metastasis has increased significantly within the oncology research community in recent years, due to the development of technologies aimed at the enrichment of circulating tumor cells (CTCs), the subpopulation of primary tumor cells that gain access to the circulatory system and are responsible for colonization at distant sites. In contrast to other technologies, filtration-based CTC enrichment, which exploits differences in size between larger tumor cells and surrounding smaller, non-tumor blood cells, has the potential to improve CTC characterization through isolation of tumor cell populations with greater molecular heterogeneity. However, microscopic analysis of uneven filtration surfaces containing CTCs is laborious, time-consuming, and inconsistent, preventing widespread use of filtration-based enrichment technologies. Here, integrated with a microfiltration-based CTC and rare cell enrichment device we have previously described, we present a protocol for Fourier Ptychographic Microscopy (FPM), a method that, unlike many automated imaging platforms, produces high-speed, high-resolution images that can be digitally refocused, allowing users to observe objects of interest present on multiple focal planes within the same image frame. The development of a cost-effective and high-throughput CTC analysis system for filtration-based enrichment technologies could have profound clinical implications for improved CTC detection and analysis.

Inertial microfluidics combined with selective cell lysis for high throughput separation of nucleated cells from whole blood

The ability to rapidly analyze blood cells provides a wealth of information about our health. Here, we report on an automated, high-throughput, method that completely removes red blood cells and sort cells into subpopulation for downstream analysis.

Microfilter-Based Capture and Release of Viable Circulating Tumor Cells

Microfilters with slot-pore geometry can be used for size-based capture of circulating tumor cells (CTC) from the blood of cancer patients. The slot pore geometry reduces the shear stress that the cells would typically experience during filtration process and allows the cells to remain viable. The microfilter provides a platform capable of high CTC capture efficiency; however, the release of these cells from the filter following capture is nontrivial, possibly due to the strong nonspecific electrostatic adhesion of CTC to the microfilter surface. Techniques such as reverse flow or cell scraping result in recovery of only a small percentage of captured cells. We describe, in detail, a protocol for novel application of thermo-responsive polymer poly(N-iso-propylacrylamide) (PIPAAm) to release viable CTCs from microfilters with slot pores. Following fabrication of the microfilter, a coating of PIPAAm is applied to the surface to exploit its thermoresponsive interfacial properties to release the cells. Typically, cancer patient's blood is filtered at room temperature (below 32 °C) when PIPAAm is hydrophilic. Thereafter, the filter is placed in either culture medium or a buffer maintained at 37 °C, which renders PIPAAm hydrophobic, allowing subsequent release of the electrostatically bound cells with high efficiency. Using this method, viable CTC captured directly from cancer patients' blood can be subjected to downstream off-chip culture, analyses, and characterization.

Successful chemoimmunotherapy against hepatocellular cancer in a novel murine model

BACKGROUND & AIMS

We have established a clinically relevant animal model of hepatocellular cancer (HCC) in immune competent mice to elucidate the complex dialog between host immunity and tumors during HCC initiation and progression. Mechanistic findings have been leveraged to develop a clinically feasible anti-tumor chemoimmunotherapeutic strategy.

METHODS

Intraperitoneal injection of carbon tetrachloride and intrasplenic inoculation of oncogenic hepatocytes were combined to induce progressive HCCs in fibrotic livers of immunocompetent mice. Immunization and adoptive cell transfer (ACT) were used to dissect the tumor antigen-specific immune response. The ability of the tyrosine kinase inhibitor sunitinib to enhance immunotherapy in the setting of HCC was evaluated.

RESULTS

This new mouse model mimics human HCC and reflects its typical features. Tumor-antigen-specific CD8⁺ T cells maintained a naïve phenotype and remained responsive during early-stage tumor progression. Late tumor progression produced circulating tumor cells, tumor migration into draining lymph nodes, and profound exhaustion of tumor-antigen-specific CD8⁺ T cells associated with accumulation of programmed cell death protein 1 (PD-1)^hi CD8⁺ T cells and regulatory T cells (Tregs). Sunitinib-mediated tumoricidal effect and Treg suppression synergized with antibody-mediated blockade of PD-1 to powerfully suppress tumor growth and activate anti-tumor immunity.

CONCLUSION

Treg accumulation and upregulation of PD-1 provide two independent mechanisms to induce profound immune tolerance in HCC. Chemoimmunotherapy using Food and Drug Administration-approved sunitinib with anti-PD-1 antibodies achieved significant tumor control, supporting translation of this approach for the treatment of HCC patients.

LAY SUMMARY

In the current study, we have established a clinically relevant mouse model which mimics human liver cancer. Using this unique model, we studied the response of the immune system to this aggressive cancer. Findings from this trial have led to the development of an innovative and clinically feasible chemoimmunotherapeutic strategy.

Filtration and Analysis of Circulating Cancer Associated Cells from the Blood of Cancer Patients

Filtration is one of the most efficient methods to remove red and white blood cells from whole blood, while retaining larger cells on the surface of the filter. Precision pore microfilters, such as the CellSieve™ microfilters, are ideally suited for this purpose, as they are strong, with uniform pore size and distribution, and have low fluorescent background required for microscopic image analysis. We present a system to implement the filtration of whole blood in combination with CellSieve™ microfilters that is simple and straightforward to use. Being that the blood of cancer patients often contains both tumor cells and stromal cells associated with cancer that are larger than normal blood cells, microfiltration shows great promise in better understanding these cell types. Accurate identification and characterization of cancer associated cells has led to increased specificity as it relates to CTCs and epithelial-mesenchymal transition cells (EMTs) and enabled the identification of previously unknown cell types, such as cancer associated macrophage-like cells (CAMLs). Using a system that isolates both CTCs and circulating stromal cells, clinicians can better diagnose cancer patients to determine therapy, monitor treatment, and watch for recurrence.

Rapid and Sensitive Detection of Cancer Cells Based on the Photothermal Effect of Graphene Functionalized Magnetic Microbeads

A strategy based on an immune-graphene oxide (GO)-magnetic microbead complex for the sensitive, rapid, portable, and low-cost detection of cancer cells was developed. The high-efficiency cell capture and high sensitive thermal contrast detection could be simultaneously achieved using magnetic microbeads and the photothermal effect of GOs. The temperature variation caused by irradiating the GOs with a laser was used to establish the standard curve of temperature variation and cancer cell number. Under optimal conditions, the limit of detection could reach 100 cells. 4T1 cells spiked in human blood could be successfully detected in 1.5 h, and the recovery was between 90.8% and 116.5%.

Automated electrorotation shows electrokinetic separation of pancreatic cancer cells is robust to acquired chemotherapy resistance, serum starvation, and EMT

We used automated electrorotation to measure the cytoplasmic permittivity, cytoplasmic conductivity, and specific membrane capacitance of pancreatic cancer cells under environmental perturbation to evaluate the effects of serum starvation, epithelial-to-mesenchymal transition, and evolution of chemotherapy resistance which may be associated with the development and dissemination of cancer. First, we compared gemcitabine-resistant BxPC3 subclones with gemcitabine-naive parental cells. Second, we serum-starved BxPC3 and PANC-1 cells and compared them to untreated counterparts. Third, we induced the epithelial-to-mesenchymal transition in PANC-1 cells and compared them to untreated PANC-1 cells. We also measured the electrorotation spectra of white blood cells isolated from a healthy donor. The properties from fit electrorotation spectra were used to compute dielectrophoresis (DEP) spectra and crossover frequencies. For all three experiments, the median crossover frequency for both treated and untreated pancreatic cancer cells remained significantly lower than the median crossover frequency for white blood cells. The robustness of the crossover frequency to these treatments indicates that DEP is a promising technique for enhancing capture of circulating cancer cells.

Capture and Release of Viable Circulating Tumor Cells from Blood

We demonstrate a method for size based capture of viable circulating tumor cell (CTC) from whole blood, along with the release of these cells from chip for downstream analysis and/or culture. The strategy employs the use of a novel Parylene C membrane slot pore microfilter to capture CTC and a coating of poly (N-iso-propylacrylamide) (PIPAAm) for thermoresponsive viable release of the captured CTC. The capture of live cells is enabled by leveraging the design of a slot pore geometry with specific dimensions to reduce the shear stress typically associated with the filtration process. While the microfilter exhibits a high capture efficiency, the release of these cells is non-trivial. Typically, only a small percentage of cells are released when techniques such as reverse flow or cell scraping are used. The strong adhesion of these epithelial cancer cells to the Parylene C membrane is attributable to non-specific electrostatic interaction. To counteract this effect, we employed the use of PIPAAm coating and exploited its thermal responsive interfacial properties to release the cells from the filter. Blood is first filtered at room temperature. Below 32 °C, PIPAAm is hydrophilic. Thereafter, the filter is placed in either culture media or a buffer maintained at 37 °C, which results in the PIPAAm turning hydrophobic, and subsequently releasing the electrostatically bound cells.

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

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

Clinical Application of Circulating Tumour Cells in Prostate Cancer: From Bench to Bedside and Back

Prostate cancer is the most common cancer in men worldwide. To improve future drug development and patient management, surrogate biomarkers associated with relevant outcomes are required. Circulating tumour cells (CTCs) are tumour cells that can enter the circulatory system, and are principally responsible for the development of metastasis at distant sites. In recent years, interest in detecting CTCs as a surrogate biomarker has ghiiukjrown. Clinical studies have revealed that high levels of CTCs in the blood correlate with disease progression in patients with prostate cancer; however, their predictive value for monitoring therapeutic response is less clear. Despite the important progress in CTC clinical development, there are critical requirements for the implementation of their analysis as a routine oncology tool. The goal of the present review is to provide an update on the advances in the clinical validation of CTCs as a surrogate biomarker and to discuss the principal obstacles and main challenges to their inclusion in clinical practice.

Surface micromachining of polydimethylsiloxane for microfluidics applications

Polydimethylsiloxane (PDMS) elastomer has emerged as one of the most frequently applied materials in microfluidics. However, precise and large-scale surface micromachining of PDMS remains challenging, limiting applications of PDMS for microfluidic structures with high-resolution features. Herein, surface patterning of PDMS was achieved using a simple yet effective method combining direct photolithography followed by reactive-ion etching (RIE). This method incorporated a unique step of using oxygen plasma to activate PDMS surfaces to a hydrophilic state, thereby enabling improved adhesion of photoresist on top of PDMS surfaces for subsequent photolithography. RIE was applied to transfer patterns from photoresist to underlying PDMS thin films. Systematic experiments were conducted in the present work to characterize PDMS etch rate and etch selectivity of PDMS to photoresist as a function of various RIE parameters, including pressure, RF power, and gas flow rate and composition. We further compared two common RIE systems with and without bias power and employed inductively coupled plasma and capacitively coupled plasma sources, respectively, in terms of their PDMS etching performances. The RIE-based PDMS surface micromachining technique is compatible with conventional Si-based surface and bulk micromachining techniques, thus opening promising opportunities for generating hybrid microfluidic devices with novel functionalities.

Affinity Versus Label-Free Isolation of Circulating Tumor Cells: Who Wins?

The study of circulating tumor cells (CTCs) has been made possible by many technological advances in their isolation. Their isolation has seen many fronts, but each technology brings forth a new set of challenges to overcome. Microfluidics has been a key player in the capture of CTCs and their downstream analysis, with the aim of shedding light into their clinical application in cancer and metastasis. Researchers have taken diverging paths to isolate such cells from blood, ranging from affinity-based isolation targeting surface antigens expressed on CTCs, to label-free isolation taking advantage of the size differences between CTCs and other blood cells. For both major groups, many microfluidic technologies have reported high sensitivity and specificity for capturing CTCs. However, the question remains as to the superiority among these two isolation techniques, specifically to identify different CTC populations. This review highlights the key aspects of affinity and label-free microfluidic CTC technologies, and discusses which of these two would be the highest benefactor for the study of CTCs.

Opportunities and Challenges for Pancreatic Circulating Tumor Cells

Sensitive and reproducible platforms have been developed for detection, isolation, and enrichment of circulating tumor cells (CTCs)-rare cells that enter the blood from solid tumors, including those of the breast, prostate gland, lung, pancreas, and colon. These might be used as biomarkers in diagnosis or determination of prognosis. CTCs are no longer simply detected and quantified; they are now used in ex vivo studies of anticancer agents and early detection. We review what we have recently learned about CTCs from pancreatic tumors, describing advances in their isolation and analysis and challenges to their clinical utility. We summarize technologies used to isolate CTCs from blood samples of patients with pancreatic cancer, including immunoaffinity and label-free physical attribute-based capture. We explain methods of CTC analysis and how findings from these studies might be used to detect cancer at earlier stages, monitor disease progression, and determine prognosis. We review studies that have expanded CTCs for testing of anticancer agents and how these approaches might be used to personalize treatment. Advances in the detection, isolation, and analysis of CTCs have increased our understanding of the dissemination and progression of pancreatic cancer. However, standardization of methodologies and prospective studies are needed for this emerging technology to have a significant effect on clinical care.

Adhesion-based tumor cell capture using nanotopography

Circulating tumor cells (CTCs) shed from primary tumors, transport through the blood stream to distant sites, and cause 90% of cancer deaths. Although different techniques have been developed to isolate CTCs for cancer detection, diagnosis and treatment, the heterogeneity of expression of the target antigen and the significant size variance in CTCs limit clinical applications of antibody- and size-based isolation techniques. Cell adhesion using nanotopography has been suggested as a promising approach to isolate CTCs independent of surface marker expression or size of CTCs. However, the nanotopographies studied are mainly nanopillars; the influence of other nanotopography such as nanogratings and their dimensions on tumor cell capture remains to be investigated. This study examined capture performance of several cancer cell lines of different types, surface marker expression and metastatic status on nanotopographies of various geometries and dimensions without antibody conjugation. The cancer cells exhibited differential capture performance on the nanotopographies with an efficiency up to 52%. Compared with flat surfaces and isotropic, discrete nanopillars, nanogratings favored cancer cell adhesion, thus improving the capture efficiency. The influence of nanotopography height studied, on the other hand, was less significant. This study provides useful information to optimize nanotopography for further improvement of CTC capture efficiency.

Poly(ethylene glycol)-Modified Tapered-Slit Membrane Filter for Efficient Release of Captured Viable Circulating Tumor Cells

The grafting of poly(ethylene glycol) (PEG) onto an SU8 microfilter has been demonstrated for efficient capture and release of circulating tumor cells (CTCs). Previous CTC filters showed low cell release efficiency due to hydrophobic surfaces, even though their capture efficiency was considerable. PEG, a hydrophilic polymeric compound mainly used to form nonfouling thin films on silicon surfaces, induces repulsive force so that the nonspecific adsorption of the surface is incomparably reduced in comparison with unmodified filter surfaces. The effectiveness of PEG-modified CTC filters was verified through lung (H358) and colorectal (SW620) cancer cells spiked, respectively, in phosphate-buffered saline (PBS) and unprocessed whole blood. The modified SU8 filters achieved approximately 37.7% and 22.8% improvement in release efficiency without significant changes in cell viability and capture efficiency. In order to verify the filter's potential for clinical applications, we extended our experiments using cancer patient blood samples. Six blood samples from colorectal and lung cancer patients were processed, and captured CTCs were efficiently released. From these experiments, the present PEG-modified filter captures and releases on average 14 ± 7.4 CTCs/mL, including EpCAM-negative CTCs, which could not be captured by previous single antibody-based methods. The antibody-free isolation with enhanced release efficiency facilitates viable cell retrieval, which is significant to CTC culture and comprehensive molecular study for verifying the mechanism of metastasis and cancer.

Promise and limits of the CellSearch platform for evaluating pharmacodynamics in circulating tumor cells

Circulating tumor cells (CTCs), which are captured from blood with anti-epithelial cell adhesion molecule (EpCAM) antibodies, have established prognostic value in specific epithelial cancers, but less is known about their utility for assessing patient response to molecularly targeted agents via measurement of pharmacodynamic (PD) endpoints. We discuss the use of CellSearch (Janssen Diagnostics, LLC, Raritan, NJ) CTC isolation technology for monitoring PD response in early phase trials. We present representative data from three clinical trials with the poly(ADP-ribose) polymerase (PARP) inhibitor veliparib (ABT-888) suggesting that CTCs can be used to measure PD effects. However, while often leading to hypothesis-generating information, our experience points to the difficulty in obtaining sufficient EpCAM-expressing CTCs from patients with advanced disease to reach statistically significant conclusions about PD effects from each trial. Overall, the level of phenotypic heterogeneity observed in specimens from patients with advanced carcinomas suggests caution in the use of cell-surface differentiation marker-based methods for isolating CTCs.