Detection and isolation of circulating tumor cells: principles and methods

Design and Application of Microfluidic Capture Device for Physical-Magnetic Isolation of MCF-7 Circulating Tumor Cells

Circulating tumor cells (CTCs) are a type of cancer cell that spreads from the main tumor to the bloodstream, and they are often the most important among the various entities that can be isolated from the blood. For the diagnosis of cancer, conventional biopsies are often invasive and unreliable, whereas a liquid biopsy, which isolates the affected item from blood or lymph fluid, is a less invasive and effective diagnostic technique. Microfluidic technologies offer a suitable channel for conducting liquid biopsies, and this technology is utilized to extract CTCs in a microfluidic chip by physical and bio-affinity-based techniques. This effort uses functionalized magnetic nanoparticles (MNPs) in a unique microfluidic chip to collect CTCs using a hybrid (physical and bio-affinity-based/guided magnetic) capturing approach with a high capture rate. Accordingly, folic acid-functionalized Fe3O4 nanoparticles have been used to capture MCF-7 (breast cancer) CTCs with capture efficiencies reaching up to 95% at a 10 µL/min flow rate. Moreover, studies have been conducted to support this claim, including simulation and biomimetic investigations.

Circulating tumor cells in gastric cancer: developments and clinical applications

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

Clinical value of folate receptor-positive circulating tumor cells in patients with esophageal squamous cell carcinomas: a retrospective study

BACKGROUND

The aim of the study is to explore the role of preoperative folate receptor-positive circulating tumor cell (FR+CTC) levels in predicting disease-free survival (DFS) and overall survival (OS) in patients with esophageal squamous cell carcinomas (ESCC).

METHODS

Three ml blood samples were prospectively drawn from ESCC patients, and ligand-targeted polymerase chain reaction (LT-PCR) was used for the quantification of FR+CTCs. Other serum indicators were measured by traditional methods. Clinicopathological characteristics were obtained from the hospital medical record system, DFS and OS data were obtained by follow-up. The correlation between clinico-pathological characteristics, DFS, and OS and FR+CTCs were analyzed, respectively. Risk factors potentially affecting DFS and OS were explored by Cox regression analysis.

RESULTS

there were no significant correlations between FR+CTCs and patient age, sex, albumin, pre-albumin, C-reactive protein (CRP), ferritin and CRP/Albumin ratio, tumor size, grade of differentiation, lymph node metastasis, TNM stage, perineural invasion/vessel invasion (all P > 0.05). Nevertheless, preoperative FR+CTCs were an independent prognostic factor for DFS (HR 2.7; 95% CI 1.31-, P = 0.007) and OS (HR 3.37; 95% CI 1.06-, P = 0.04). DFS was significantly shorter for patients with post-operative FR+CTCs ≥ 17.42 FU/3ml compared with patients < 17.42 FU/3ml (P = 0.0012). For OS, it was shorter for patients with FR+CTCs ≥ 17.42 FU/3ml compared with patients < 17.42 FU/3ml, however, the difference did not reach statistical significance (P = 0.51).

CONCLUSIONS

ESCC patients with high FR+CTCs tend to have a worse prognosis. FR+CTCs may monitor the recurrence of cancers in time, accurately assess patient prognosis, and guide clinical decision-making.

TRIAL REGISTRATION

The study was approved by the Sichuan Cancer Hospital & Institute Ethics Committee (No. SCCHEC-02-2022-050).

Label-free approaches for extracellular vesicle detection

Extracellular vesicles (EVs) represent pivotal mediators in cell-to-cell communication. They are lipid-membranous carriers of several biomolecules, which can be produced by almost all cells. In the current Era of precision medicine, EVs gained growing attention thanks to their potential in both biomarker discovery and nanotherapeutics applications. However, current technical limitations in isolating and/or detecting EVs restrain their standard use in clinics. This review explores all the state-of-the-art analytical technologies which are currently overcoming these issues. On one end, several innovative optical-, electrical-, and spectroscopy-based detection methods represent advantageous label-free methodologies for faster EV detection. On the other end, microfluidics-based lab-on-a-chip tools support EV purification from low-concentrated samples. Altogether, these technologies will strengthen the routine application of EVs in clinics.

Raman Spectroscopy Combined with Malaria Protein for Early Capture and Recognition of Broad-Spectrum Circulating Tumor Cells

Early identification of tumors can significantly reduce the mortality rate. Circulating tumor cells (CTCs) are a type of tumor cell that detaches from the primary tumor and circulates through the bloodstream. Monitoring CTCs may allow the early identification of tumor progression. However, due to their rarity and heterogeneity, the enrichment and identification of CTCs is still challenging. Studies have shown that Raman spectroscopy could distinguish CTCs from metastatic cancer patients. VAR2CSA, a class of malaria proteins, has a strong broad-spectrum binding effect on various tumor cells and is a promising candidate biomarker for cancer detection. Here, recombinant malaria VAR2CSA proteins were synthesized, expressed, and purified. After confirming that various types of tumor cells can be isolated from blood by recombinant malaria VAR2CSA proteins, we further proved that the VAR2CSA combined with Raman spectroscopy could be used efficiently for tumor capture and type recognition using A549 cell lines spiked into the blood. This would allow the early screening and detection of a broad spectrum of CTCs. Finally, we synthesized and purified the malaria protein fusion antibody and confirmed its in vitro tumor-killing activity. Herein, this paper exploits the theoretical basis of a novel strategy to capture, recognize, and kill broad-spectrum types of CTCs from the peripheral blood.

Chemically-Modified Sepharose 6B Beads for Collection of Circulating Tumor Cells

The isolation and quantitative characterization of circulating tumor cells (CTCs) are of great importance in cancer diagnosis and prognosis. However, isolating and detecting CTCs in whole blood presents a significant challenge due to the low numbers of CTCs (often ranging from one to five) in samples containing billions of erythrocytes. Recently, point-of-care devices that use antibody trapping coupled with remote immunofluorescence analyses have been described to identify the number and type of CTCs in blood. In this study, we propose a novel method for trapping and quantifying CTCs using Sepharose 6B beads of 45-160 μm size that are engineered with capture antibodies. Specifically, we employed CD44 antibody conjugates (bearing a maleimide group) that are specific to the CTCs of breast cancer to thiol-Sepharose beads 6B. These beads, when mixed with MDAMB231 and Jurkat cells and filtered through a 40 μm filter, can capture ~80% of MDAMB231 cells. Furthermore, the antibody-modified Sepharose 6B can be stored at four degrees Celsius for a period exceeding six months.

Rapid detection of EGFR mutation in CTCs based on a double spiral microfluidic chip and the real-time RPA method

Circulating tumor cells (CTCs) are cells shed from primary or metastatic tumors and spread into the peripheral bloodstream. Mutation detection in CTCs can reveal vital genetic information about the tumors and can be used for "liquid biopsy" to indicate cancer treatment and targeted medication. However, current methods to measure the mutations in CTCs are based on PCR or DNA sequencing which are cumbersome and time-consuming and require sophisticated equipment. These largely limited their applications especially in areas with poor healthcare infrastructure. Here we report a simple, convenient, and rapid method for mutation detection in CTCs, including an example of a deletion at exon 19 (Del19) of the epidermal growth factor receptor (EGFR). CTCs in the peripheral blood of NSCLC patients were first sorted by a double spiral microfluidic chip with high sorting efficiency and purity. The sorted cells were then lysed by proteinase K, and the E19del mutation was detected via real-time recombinase polymerase amplification (RPA). Combining the advantages of microfluidic sorting and real-time RPA, an accurate mutation determination was realized within 2 h without professional operation or complex data interpretation. The method detected as few as 3 cells and 1% target variants under a strongly interfering background, thus, indicating its great potential in the non-invasive diagnosis of E19del mutation for NSCLC patients. The method can be further extended by redesigning the primers and probes to detect other deletion mutations, insertion mutations, and fusion genes. It is expected to be a universal molecular diagnostic tool for real-time assessment of relevant mutations and precise adjustments in the care of oncology patients.

Modular microfluidics for life sciences

The advancement of microfluidics has enabled numerous discoveries and technologies in life sciences. However, due to the lack of industry standards and configurability, the design and fabrication of microfluidic devices require highly skilled technicians. The diversity of microfluidic devices discourages biologists and chemists from applying this technique in their laboratories. Modular microfluidics, which integrates the standardized microfluidic modules into a whole, complex platform, brings the capability of configurability to conventional microfluidics. The exciting features, including portability, on-site deployability, and high customization motivate us to review the state-of-the-art modular microfluidics and discuss future perspectives. In this review, we first introduce the working mechanisms of the basic microfluidic modules and evaluate their feasibility as modular microfluidic components. Next, we explain the connection approaches among these microfluidic modules, and summarize the advantages of modular microfluidics over integrated microfluidics in biological applications. Finally, we discuss the challenge and future perspectives of modular microfluidics.

Attention Mask R-CNN with edge refinement algorithm for identifying circulating genetically abnormal cells

Recent studies have suggested that circulating tumor cells with abnormalities in gene copy numbers in mononuclear cell-enriched peripheral blood samples, such as circulating genetically abnormal cells (CACs), can be used as a non-invasive tool to detect patients with benign pulmonary nodules. These cells are identified through fluorescence signals counting by using 4-color fluorescence in situ hybridization (FISH) technology that exhibits high stability, sensitivity, and specificity. When FISH data are analyzed, the overlapping cells and fluorescence noise is a great challenge for identifying of CACs, thereby seriously affecting the efficiency of clinical diagnosis. To address this problem, in this study, we proposed an end-to-end FISH-based method (CACNET) for CAC identification. CACNET achieved nuclear segmentation and counted 4-color staining signals through improved Mask region-based convolutional neural network (R-CNN), followed by cell category (normal cell, deletion cell, gain cell, or CAC) according to pathological criteria. Firstly, the segmentation accuracy of overlapping nuclei was improved by adding an edge constraint head during training. Then, the interference of fluorescence noise was reduced by fusing non-local module to reconstruct the feature extraction network of Mask R-CNN. We trained and tested the proposed model on a dataset comprising 700 frames with 58,083 nuclei. The Accuracy, Sensitivity, and Specificity (overall performance metric for the algorithm) of CAC identification with CACNET were 94.06%, 92.1%, and 99.8%, respectively. Moreover, the developed method exhibited approximately identification speed of approximately 0.22 s per frames. The results showed that the proposed method outperformed the existing CAC identification methods, making it a promising approach for early screening of lung cancer.

High-throughput isolation of cancer cells in spiral microchannel by changing the direction, magnitude and location of the maximum velocity

Circulating tumor cells (CTCs) are scarce cancer cells that rarely spread from primary or metastatic tumors inside the patient's bloodstream. Determining the genetic characteristics of these paranormal cells provides significant data to guide cancer staging and treatment. Cell focusing using microfluidic chips has been implemented as an effective method for enriching CTCs. The distinct equilibrium positions of particles with different diameters across the microchannel width in the simulation showed that it was possible to isolate and concentrate breast cancer cells (BCCs) from WBCs at a moderate Reynolds number. Therefore we demonstrate high throughput isolation of BCCs using a passive, size-based, label-free microfluidic method based on hydrodynamic forces by an unconventional (combination of long loops and U-turn) spiral microfluidic device for isolating both CTCs and WBCs with high efficiency and purity (more than 90%) at a flow rate about 1.7 mL/min, which has a high throughput compared to similar ones. At this golden flow rate, up to 92% of CTCs were separated from the cell suspension. Its rapid processing time, simplicity, and potential ability to collect CTCs from large volumes of patient blood allow the practical use of this method in many applications.

Current and Emerging Techniques for Diagnosis and MRD Detection in AML: A Comprehensive Narrative Review

Acute myeloid leukemia (AML) comprises a group of hematologic neoplasms characterized by abnormal differentiation and proliferation of myeloid progenitor cells. AML is associated with poor outcome due to the lack of efficient therapies and early diagnostic tools. The current gold standard diagnostic tools are based on bone marrow biopsy. These biopsies, apart from being very invasive, painful, and costly, have low sensitivity. Despite the progress uncovering the molecular pathogenesis of AML, the development of novel detection strategies is still poorly explored. This is particularly important for patients that check the criteria for complete remission after treatment, since they can relapse through the persistence of some leukemic stem cells. This condition, recently named as measurable residual disease (MRD), has severe consequences for disease progression. Hence, an early and accurate diagnosis of MRD would allow an appropriate therapy to be tailored, improving a patient's prognosis. Many novel techniques with high potential in disease prevention and early detection are being explored. Among them, microfluidics has flourished in recent years due to its ability at processing complex samples as well as its demonstrated capacity to isolate rare cells from biological fluids. In parallel, surface-enhanced Raman scattering (SERS) spectroscopy has shown outstanding sensitivity and capability for multiplex quantitative detection of disease biomarkers. Together, these technologies can allow early and cost-effective disease detection as well as contribute to monitoring the efficiency of treatments. In this review, we aim to provide a comprehensive overview of AML disease, the conventional techniques currently used for its diagnosis, classification (recently updated in September 2022), and treatment selection, and we also aim to present how novel technologies can be applied to improve the detection and monitoring of MRD.

Clinical significance of circulating tumor cell (CTC)-specific microRNA (miRNA) in breast cancer

As a noninvasive method, circulating tumor cell (CTC) provides ideal liquid biopsy specimens for early cancer screening and diagnosis. CTCs detection in breast cancer is correlated with patient prognosis such as disease-free survival (DFS) and overall survival (OS). Besides, accumulating evidence supported that CTCs count may be indicator for chemotherapy response as well. The functional roles of microRNA (miRNA) in breast cancer have been well-recognized for the last few years. Due to its stability in circulation, numerous studies have proven that circulating miRNA may serve as promising diagnostic and prognostic biomarkers in breast cancer. The potential ability of miRNAs in disease screening, staging or even molecular subtype classification makes them valuable tools for early breast cancer patients. It would be of great significance to characterize the miRNA expression profile in CTCs, which could provide reliable biological information originated from tumor. However, some issues need to be addressed before the utility of CTC-specific miRNAs in clinical setting. Taken together, we believe that CTC-specific miRNA detection will be trend for early breast cancer screening, diagnosis and treatment monitor in near future.

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

Background

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

Methods

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

Results

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

Conclusion

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

Microfluidics for the Isolation and Detection of Circulating Tumor Cells

Nowadays, liquid biopsy represents one of the most promising techniques for early diagnosis, monitoring, and therapy screening of cancer. This novel methodology includes, among other techniques, the isolation, capture, and analysis of circulating tumor cells (CTCs). Nonetheless, the identification of CTC from whole blood is challenging due to their extremely low concentration (1-100 per ml of whole blood), and traditional methods result insufficient in terms of purity, recovery, throughput and/or viability of the processed sample. In this context, the development of microfluidic devices for detecting and isolating CTCs offers a wide range of new opportunities due to their excellent properties for cell manipulation and the advantages to integrate and bring different laboratory processes into the microscale improving the sensitivity, portability, reducing cost and time. This chapter explores current and recent microfluidic approaches that have been developed for the analysis and detection of CTCs, which involve cell capture methods based on affinity binding and label-free methods and detection based on electrical, chemical, and optical sensors. All the exposed technologies seek to overcome the limitations of commercial systems for the analysis and isolation of CTCs, as well as to provide extended analysis that will allow the development of novel and more efficient diagnostic tools.

An efficient fluorescence in situ hybridization (FISH)-based circulating genetically abnormal cells (CACs) identification method based on Multi-scale MobileNet-YOLO-V4

BACKGROUND

Circulating tumor cells (CTCs) acting as "liquid biopsy" of cancer are cells that have been shed from the primary tumor, which cause the development of a secondary tumor in a distant organ site, leading to cancer metastasis. Recent research suggests that CTCs with abnormalities in gene copy numbers in mononuclear cell-enriched peripheral blood samples, namely circulating genetically abnormal cells (CACs), could be used as a non-invasive decision tool to detect patients with benign pulmonary nodules. Such cells are identified by counting the fluorescence signals of fluorescence in situ hybridization (FISH). However, owing to the rarity of CACs in the blood, identification of CACs using this technique is time-consuming and is a drawback of this method.

METHODS

This study has proposed an efficient and automatic FISH-based CACs identification approach which is based on a combination of the high accuracy of You Only Look Once (YOLO)-V4 and the lightweight and rapidness of MobileNet-V3. The backbone of YOLO-V4 was replaced with MobileNet-V3 to improve the detection efficiency and prevent overfitting, and the architecture of YOLO-V4 was optimized by utilizing a new feature map with a larger scale to enable the enhanced detection ability for small targets.

RESULTS

We trained and tested the proposed model using a dataset containing more than 7,000 cells based on five-fold cross-validation. All the images in the dataset were 2,448×2,048 (pixels) in size. The number of cells in each image was >70. The accuracy of four-color fluorescence signals detection for our proposed model were all approximately 98%, and the mean average precision (mAP) were close to 100%. The final outcome of the developed method was the type of cells, i.e., normal cells, CACs, gaining cells or deletion cells. The method had a CACs identification accuracy of 93.86% (similar to an expert pathologist), and a detection speed that was about 500 times greater than that of a pathologist.

CONCLUSIONS

The developed method could greatly increase the review accuracy, enhance the efficiency of reviewers, and reduce the review turnaround time during CACs identification.

Unraveling Cancer Metastatic Cascade Using Microfluidics-based Technologies

Cancer has long been a leading cause of death. The primary tumor, however, is not the main cause of death in more than 90% of cases. It is the complex process of metastasis that makes cancer deadly. The invasion metastasis cascade is the multi-step biological process of cancer cell dissemination to distant organ sites and adaptation to the new microenvironment site. Unraveling the metastasis process can provide great insight into cancer death prevention or even treatment. Microfluidics is a promising platform, that provides a wide range of applications in metastasis-related investigations. Cell culture microfluidic technologies for in vitro modeling of cancer tissues with fluid flow and the presence of mechanical factors have led to the organ-on-a-chip platforms. Moreover, microfluidic systems have also been exploited for capturing and characterization of circulating tumor cells (CTCs) that provide crucial information on the metastatic behavior of a tumor. We present a comprehensive review of the recent developments in the application of microfluidics-based systems for analysis and understanding of the metastasis cascade from a wider perspective.

New horizons in the identification of circulating tumor cells (CTCs): An emerging paradigm shift in cytosensors

Circulating tumor cells (CTCs) are cancer cells that are shed from a primary tumor into the bloodstream and function as seeds for cancer metastasis at distant locations. Enrichment and identification methods of CTCs in the blood of patients plays an important role in diagnostic assessments and personalized treatments of cancer. However, the current traditional identification methods not only impact the viability of cells, but also cannot determine the type of cancer cells when the disease is unknown. Hence, new methods to identify CTCs are urgently needed. In this context, many advanced and safe technologies have emerged to distinguish between cancer cells and blood cells, and to distinguish specific types of cancer cells. In this review, at first we have briefly discussed recent advances in technologies related to the enrichment of CTCs, which lay a good foundation for the identification of CTCs. Next, we have summarized state-of-the-art technologies to confirm whether a given cell is indeed a tumor cell and determine the type of tumor cell. Finally, the challenges for application and potential directions of the current identification methods in clinical analysis of CTCs have been discussed.

Discriminating Epithelial to Mesenchymal Transition Phenotypes in Circulating Tumor Cells Isolated from Advanced Gastrointestinal Cancer Patients

Gastrointestinal (GI) cancers constitute a group of highest morbidity worldwide, with colorectal cancer (CRC) and gastric cancer being among the most frequently diagnosed. The majority of gastrointestinal cancer patients already present metastasis by the time of diagnosis, which is widely associated with cancer-related death. Accumulating evidence suggests that epithelial-to-mesenchymal transition (EMT) in cancer promotes circulating tumor cell (CTCs) formation, which ultimately drives metastasis development. These cells have emerged as a fundamental tool for cancer diagnosis and monitoring, as they reflect tumor heterogeneity and the clonal evolution of cancer in real-time. In particular, EMT phenotypes are commonly associated with therapy resistance. Thus, capturing these CTCs is expected to reveal important clinical information. However, currently available CTC isolation approaches are suboptimal and are often targeted to capture epithelial CTCs, leading to the loss of EMT or mesenchymal CTCs. Here, we describe size-based CTCs isolation using the RUBYchip™, a label-free microfluidic device, aiming to detect EMT biomarkers in CTCs from whole blood samples of GI cancer patients. We found that, for most cases, the mesenchymal phenotype was predominant, and in fact a considerable fraction of isolated CTCs did not express epithelial markers. The RUBYchip™ can overcome the limitations of label-dependent technologies and improve the identification of CTC subpopulations that may be related to different clinical outcomes.

Emerging on-chip electrokinetic based technologies for purification of circulating cancer biomarkers towards liquid biopsy: A review

Early detection of cancer can significantly reduce mortality and save lives. However, the current cancer diagnosis is highly dependent on costly, complex, and invasive procedures. Thus, a great deal of effort has been devoted to exploring new technologies based on liquid biopsy. Since liquid biopsy relies on detection of circulating biomarkers from biofluids, it is critical to isolate highly purified cancer-related biomarkers, including circulating tumor cells (CTCs), cell-free nucleic acids (cell-free DNA and cell-free RNA), small extracellular vesicles (exosomes), and proteins. The current clinical purification techniques are facing a number of drawbacks including low purity, long processing time, high cost, and difficulties in standardization. Here, we review a promising solution, on-chip electrokinetic-based methods, that have the advantage of small sample volume requirement, minimal damage to the biomarkers, rapid, and label-free criteria. We have also discussed the existing challenges of current on-chip electrokinetic technologies and suggested potential solutions that may be worthy of future studies.

Liquid Biopsy-Based Colorectal Cancer Screening via Surface Markers of Circulating Tumor Cells

Colorectal cancer (CRC) is ranked second for cancer-related deaths worldwide with approximately half of the patients being diagnosed at the late stages. The untimely detection of CRC results in advancement to the metastatic stage and nearly 90% of cancer-related deaths. The early detection of CRC is crucial to decrease its overall incidence and mortality rates. The recent introduction of circulating tumor cells (CTCs) has enabled a less invasive sampling method from liquid biopsies, besides revealing key information toward CRC metastasis. The current gold standard for CTC identification is the CellSearch® system (Veridex). This first-generation instrumentation relies on a single cell surface marker (CSM) to capture and count CTCs. Detection of CTCs allows the identification of patients at risk for metastasis, whereas CTC enumeration could improve risk assessment, monitoring of systemic therapy, and detection of therapy resistance in advanced metastatic CRC. In this review, we compared the pros and cons between single CSM-based CTC enrichment techniques and multi-marker-based systems. We also highlighted the challenges faced in the routine implementation of CSM-dependent CTC detection methods in CRC screening, prediction, prognosis, disease monitoring, and therapy selection toward precision medicine, as well as the dwelling on post-CTC analysis and characterization methods.

Enhanced Separation Efficiency and Purity of Circulating Tumor Cells Based on the Combined Effects of Double Sheath Fluids and Inertial Focusing

Circulating tumor cells (CTCs) play a crucial role in solid tumor metastasis, but obtaining high purity and viability CTCs is a challenging task due to their rarity. Although various works using spiral microchannels to isolate CTCs have been reported, the sorting purity of CTCs has not been significantly improved. Herein, we developed a novel double spiral microchannel for efficient separation and enrichment of intact and high-purity CTCs based on the combined effects of two-stage inertial focusing and particle deflection. Particle deflection relies on the second sheath to produce a deflection of the focused sample flow segment at the end of the first-stage microchannel, allowing larger particles to remain focused and entered the second-stage microchannel while smaller particles moved into the first waste channel. The deflection of the focused sample flow segment was visualized. Testing by a binary mixture of 10.4 and 16.5 μm fluorescent microspheres, it showed 16.5 μm with separation efficiency of 98% and purity of 90% under the second sheath flow rate of 700 μl min⁻¹. In biological experiments, the average purity of spiked CTCs was 74% at a high throughput of 1.5 × 10⁸ cells min⁻¹, and the recovery was more than 91%. Compared to the control group, the viability of separated cells was 99%. Finally, we validated the performance of the double spiral microchannel using clinical cancer blood samples. CTCs with a concentration of 2–28 counts ml⁻¹ were separated from all 12 patients’ peripheral blood. Thus, our device could be a robust and label-free liquid biopsy platform in inertial microfluidics for successful application in clinical trials.

Label-free enrichment of rare unconventional circulating neoplastic cells using a microfluidic dielectrophoretic sorting device

Cellular circulating biomarkers from the primary tumor such as circulating tumor cells (CTCs) and circulating hybrid cells (CHCs) have been described to harbor tumor-like phenotype and genotype. CHCs are present in higher numbers than CTCs supporting their translational potential. Methods for isolation of CHCs do not exist and are restricted to low-throughput, time consuming, and biased methodologies. We report the development of a label-free dielectrophoretic microfluidic platform facilitating enrichment of CHCs in a high-throughput and rapid fashion by depleting healthy peripheral blood mononuclear cells (PBMCs). We demonstrated up to 96.5% depletion of PBMCs resulting in 18.6-fold enrichment of cancer cells. In PBMCs from pancreatic adenocarcinoma patients, the platform enriched neoplastic cells identified by their KRAS mutant status using droplet digital PCR with one hour of processing. Enrichment was achieved in 75% of the clinical samples analyzed, establishing this approach as a promising way to non-invasively analyze tumor cells from patients.

HER2 Expression in Circulating Tumour Cells Isolated from Metastatic Breast Cancer Patients Using a Size-Based Microfluidic Device

HER2 is a prognostic and predictive biomarker in breast cancer, normally assessed in tumour biopsy and used to guide treatment choices. Circulating tumour cells (CTCs) escape the primary tumour and enter the bloodstream, exhibiting great metastatic potential and representing a real-time snapshot of the tumour burden. Liquid biopsy offers the unique opportunity for low invasive sampling in cancer patients and holds the potential to provide valuable information for the clinical management of cancer patients. This study assesses the performance of the RUBYchip™, a microfluidic system for CTC capture based on cell size and deformability, and compares it with the only FDA-approved technology for CTC enumeration, CellSearch®. After optimising device performance, 30 whole blood samples from metastatic breast cancer patients were processed with both technologies. The expression of HER2 was assessed in isolated CTCs and compared to tissue biopsy. Results show that the RUBYchipTM was able to isolate CTCs with higher efficiency than CellSearch®, up to 10 times more, averaging all samples. An accurate evaluation of different CTC subpopulations, including HER2+ CTCs, was provided. Liquid biopsy through the use of the RUBYchipTM in the clinic can overcome the limitations of histological testing and evaluate HER2 status in patients in real-time, helping to tailor treatment during disease evolution.

The Yin and Yang of exosome isolation methods: conventional practice, microfluidics, and commercial kits

Exosomes are a subset of extracellular vesicles released from various cells, and they can be found in different bodily fluids. Exosomes are used as biomarkers to diagnose many diseases and to monitor therapy efficiency as they represent the status and origin of the cell, which they are released from. Considering that they co-exist in bodily fluids with other types of particles, their isolation still remains challenging since conventional separation methods are time-consuming, user-dependent, and result in low isolation yield. This review summarizes the conventional strategies and microfluidic-based methods for exosome isolation along with their strengths and limitations. Microfluidic devices emerge as a promising approach to overcome the limitations of the conventional methods due to their inherent characteristics, such as the need for minute sample volume and rapid operation, in order to isolate exosomes with a high yield and a high purity in a short amount of time, which make them unprecedented tools for molecular biology and clinical applications. This review elaborates on the existing microfluidic-based exosome isolation methods and denotes their benefits and drawbacks. Herein, we also introduce various commercially available platforms and kits for exosome isolation along with their working principles.

Inertial-Assisted Immunomagnetic Bioplatform towards Efficient Enrichment of Circulating Tumor Cells

Serving as an effective biomarker in liquid biopsy, circulating tumor cells (CTCs) can provide an accessible source for cancer biology study. For the in-depth evaluation of CTCs in cancer analysis, their efficient enrichment is essential, owing to their low abundance in peripheral blood. In this paper, self-assembled immunomagnetic beads were developed to isolate CTCs from the ordered bundles of cells under the assistance of the spiral inertial effect. Parametric numerical simulations were performed to explore the velocity distribution in the cross section. Based on this chip, rare CTCs could be recovered under the throughput of 500 μL/min, making this device a valuable supplement in cancer analysis, diagnostics, and therapeutics.

Liquid biopsy in cholangiocarcinoma: Current status and future perspectives

Cholangiocarcinoma (CCA) are a heterogeneous group of tumors in terms of aetiology, natural history, morphological subtypes, molecular alterations and management, but all sharing complex diagnosis, management, and poor prognosis. Several mutated genes and epigenetic changes have been detected in CCA, with the potential to identify diagnostic and prognostic biomarkers and therapeutic targets. Accessing tumoral components and genetic material is therefore crucial for the diagnosis, management and selection of targeted therapies; but sampling tumor tissue, when possible, is often risky and difficult to be repeated at different time points. Liquid biopsy (LB) represents a way to overcome these issues and comprises a diverse group of methodologies centering around detection of tumor biomarkers from fluid samples. Compared to the traditional tissue sampling methods LB is less invasive and can be serially repeated, allowing a real-time monitoring of the tumor genetic profile or the response to therapy. In this review, we analysis the current evidence on the possible roles of LB (circulating DNA, circulating RNA, exosomes, cytokines) in the diagnosis and management of patients affected by CCA.

Aptamer-Based Detection of Circulating Targets for Precision Medicine

The past decade has witnessed ongoing progress in precision medicine to improve human health. As an emerging diagnostic technique, liquid biopsy can provide real-time, comprehensive, dynamic physiological and pathological information in a noninvasive manner, opening a new window for precision medicine. Liquid biopsy depends on the sensitive and reliable detection of circulating targets (e.g., cells, extracellular vesicles, proteins, microRNAs) from body fluids, the performance of which is largely governed by recognition ligands. Aptamers are single-stranded functional oligonucleotides, capable of folding into unique tertiary structures to bind to their targets with superior specificity and affinity. Their mature evolution procedure, facile modification, and affinity regulation, as well as versatile structural design and engineering, make aptamers ideal recognition ligands for liquid biopsy. In this review, we present a broad overview of aptamer-based liquid biopsy techniques for precision medicine. We begin with recent advances in aptamer selection, followed by a summary of state-of-the-art strategies for multivalent aptamer assembly and aptamer interface modification. We will further describe aptamer-based micro-/nanoisolation platforms, aptamer-enabled release methods, and aptamer-assisted signal amplification and detection strategies. Finally, we present our perspectives regarding the opportunities and challenges of aptamer-based liquid biopsy for precision medicine.

A DNA logic gate with dual-anchored proximity aptamers for the accurate identification of circulating tumor cells

We have designed a DNA logic gate that can integrate the recognition of multiple biomarkers with signal amplification to perform the accurate and sensitive analysis of circulating tumor cells (CTCs). It also has the potential to analyze rare cells that exist in small amounts but are of great significance (such as stem cells) in the fields of clinical diagnosis and biomedicine.

Toward a New Era for the Management of Circulating Tumor Cells

Circulating tumor cells (CTCs) are malignant cells separate from primary tumors, which can migrate through the peripheral blood, colonize other tissues, and lead to the formation of metastases. The first description of CTCs dates back to 1869 when Thomas Ashworth recognized malignant cells similar to the ones of the primary tumor in the blood vessels of an autopsied patient with metastatic cancer. Currently, CTCs have been identified in various types of cancer and have been recognized for their clinical value in the prediction of prognosis, diagnosis of minimal residual diseases, assessment of tumor sensitivity to anticancer drugs, and personalization of therapies. However, research about these topics has several limitations, principally the rarity of CTCs in bloodstream and their heterogeneous characteristics, which makes detection and isolation difficult. As a result of these limitations, current studies are focused on improvement of isolation and characterization techniques to achieve better sensitivity in clinical applications. This review covers the methods of CTC isolation and detection and current research progression on CTC in different cancer types. The clinical applications, limitations, and perspectives of CTCs are also discussed.

Development and Clinical Prospects of Techniques to Separate Circulating Tumor Cells from Peripheral Blood

Detection of circulating tumor cells (CTC) is an important liquid biopsy technique that has advanced considerably in recent years. To further advance the development of technology for curing cancer, several CTC technologies have been proposed by various research groups. Despite their potential role in early cancer diagnosis and prognosis, CTC methods are currently used for research purposes only, and very few methods have been accepted for clinical applications because of difficulties, including CTC heterogeneity, CTC separation from the blood, and a lack of thorough clinical validation. Although current CTC technologies have not been truly implemented, they possess high potential as future clinical diagnostic techniques for individualized cancer. Here, we review current developments in CTC separation technology. We also explore new CTC detection methods based on telomerase and nanomaterials, such as in vivo flow cytometry. In addition, we discuss the difficulties that must be overcome before CTC can be applied in clinical settings.

Protein glycosylation in head and neck cancers: From diagnosis to treatment

Glycosylation is the most common post-translational modification (PTM) of proteins. Malignant tumour cells frequently undergo an alteration in surface protein glycosylation. This phenomenon is also common in cancers of the head and neck, most of which are squamous cell carcinomas (HNSCC). It affects cell functions, including proliferation, motility and invasiveness, thus increasing the propensity to metastasise. HNSCC represents the sixth most frequent malignancy worldwide. These neoplasms, which arise from the mucous membranes of the various anatomical subsites of the upper aero-digestive tract, are heterogeneous in terms of aetiology and clinico-pathologic features. With current treatments, only about 50% of HNSCC patients survive beyond 5-years. Therefore, there is the pressing need to dissect NHSCC heterogeneity to inform treatment choices. In particular, reliable biomarkers of predictive and prognostic value are eagerly needed. This review describes the current state of the art and bio-pathological meaning of glycosylation signatures associated with HNSCC and explores the possible role of tumour specific glycoproteins as potential biomarkers and attractive therapeutic targets. We have also compiled data relating to altered glycosylation and the nature of glycoproteins as tools for the identification of circulating tumour cells (CTCs) in the new era of liquid biopsy.

Prognostic Significance of Circulating Tumor Cells with Mesenchymal Phenotypes in Patients with Gastric Cancer: A Prospective Study

BACKGROUND

Circulating tumor cells (CTCs) have been shown to be heterogeneous. Focusing on the epithelial-mesenchymal transition and perioperative kinetics, we evaluated CTCs with mesenchymal phenotypes as a potential prognostic biomarker for patients with gastric cancer.

METHODS

Peripheral blood was collected from 54 patients with gastric cancer before surgery and at 1 week and 1 month after surgery. CTCs were enriched using density-gradient centrifugation and magnetic-activated cell sorting (negative selection). Cell suspensions were characterized by multi-immunofluorescence staining against cytokeratin and N-cadherin, and by 4',6'-diamidino-2-phenyldole staining.

RESULTS

CTCs were detected in five patients (17%) with early cancer and 14 patients (56%) with advanced cancer (p < 0.05). In our system, N-cadherin, but not cytokeratin, was expressed in the CTCs of 90% (19/21) of patients. Postoperative recurrence was detected in 10 patients, all of whom had N-cadherin+/cytokeratin-/CD45- CTCs preoperatively. Regarding perioperative kinetics, we divided patients into three risk groups: a high-risk group, with one or more preoperative CTCs and increased CTCs postoperatively; an intermediate-risk group, with one or more preoperative CTCs and decreased CTCs postoperatively; and a low-risk group, with no preoperative CTCs. Recurrence rates were 57% (4/7), 33% (4/12), and 6% (2/35), respectively. The relapse-free survival rate was lower in patients at high risk versus those at intermediate or low risk, for all patients (p = 0.00024) and in patients with advanced cancer (p = 0.00103).

CONCLUSIONS

N-cadherin is a highly useful marker to detect CTCs lacking cytokeratin, and the perioperative kinetics of CTC numbers is beneficial in risk stratification for survival in patients with gastric cancer.

Simultaneous Single Cell Gene Expression and EGFR Mutation Analysis of Circulating Tumor Cells Reveals Distinct Phenotypes in NSCLC

While cancer cell populations are known to be highly heterogeneous within a tumor, the current gold standard of tumor profiling is through a tumor biopsy. These biopsies are invasive and prone to missing these clones due to spatial heterogeneity, and this bulk analysis approach can miss information from rare subpopulations. To noninvasively investigate tumor cell heterogeneity, a streamlined workflow is developed to scrutinize rare cells, such as circulating tumor cells (CTCs), for simultaneous analysis of mutations and gene expression profiles at the single cell level. This powerful workflow overcomes low-input limitations of single cell analysis techniques. The utility of this multiplexed workflow to unravel inter- and intra-patient heterogeneity is demonstrated using non-small-cell lung cancer (NSCLC) CTCs (n = 58) from six epidermal growth factor receptor (EGFR) mutant positive NSCLC patients. CTCs are isolated using a high-throughput microfluidic technology, the Labyrinth, and their EGFR mutation status and gene expression profiles are characterized.

Past, Present, and Future of Affinity-based Cell Separation Technologies

Progress in cell purification technology is critical to increase the availability of viable cells for therapeutic, diagnostic, and research applications. A variety of techniques are now available for cell separation, ranging from non-affinity methods such as density gradient centrifugation, dielectrophoresis, and filtration, to affinity methods such as chromatography, two-phase partitioning, and magnetic-/fluorescence-assisted cell sorting. For clinical and analytical procedures that require highly purified cells, the choice of cell purification method is crucial, since every method offers a different balance between yield, purity, and bioactivity of the cell product. For most applications, the requisite purity is only achievable through affinity methods, owing to the high target specificity that they grant. In this review, we discuss past and current methods for developing cell-targeting affinity ligands and their application in cell purification, along with the benefits and challenges associated with different purification formats. We further present new technologies, like stimuli-responsive ligands and parallelized microfluidic devices, towards improving the viability and throughput of cell products for tissue engineering and regenerative medicine. Our comparative analysis provides guidance in the multifarious landscape of cell separation techniques and highlights new technologies that are poised to play a key role in the future of cell purification in clinical settings and the biotech industry. STATEMENT OF SIGNIFICANCE: Technologies for cell purification have served science, medicine, and industrial biotechnology and biomanufacturing for decades. This review presents a comprehensive survey of this field by highlighting the scope and relevance of all known methods for cell isolation, old and new alike. The first section covers the main classes of target cells and compares traditional non-affinity and affinity-based purification techniques, focusing on established ligands and chromatographic formats. The second section presents an excursus of affinity-based pseudo-chromatographic and non-chromatographic technologies, especially focusing on magnetic-activated cell sorting (MACS) and fluorescence-activated cell sorting (FACS). Finally, the third section presents an overview of new technologies and emerging trends, highlighting how the progress in chemical, material, and microfluidic sciences has opened new exciting avenues towards high-throughput and high-purity cell isolation processes. This review is designed to guide scientists and engineers in their choice of suitable cell purification techniques for research or bioprocessing needs.

Bioprinting of in vitro tumor models for personalized cancer treatment: a review

Studying biological characteristics of tumors and evaluating the treatment effects require appropriate in vitro tumor models. However, the occurrence, progression, and migration of tumors involve spatiotemporal changes, cell-microenvironment and cell-cell interactions, and signal transmission in cells, which makes the construction of in vitro tumor models extremely challenging. In the past few years, advances in biomaterials and tissue engineering methods, especially development of the bioprinting technology, have paved the way for innovative platform technologies for in vitro cancer research. Bioprinting can accurately control the distribution of cells, active molecules, and biomaterials. Furthermore, this technology recapitulates the key characteristics of the tumor microenvironment and constructs in vitro tumor models with bionic structures and physiological systems. These models can be used as robust platforms to study tumor initiation, interaction with the microenvironment, angiogenesis, motility and invasion, as well as intra- and extravasation. Bioprinted tumor models can also be used for high-throughput drug screening and validation and provide the possibility for personalized cancer treatment research. This review describes the basic characteristics of the tumor and its microenvironment and focuses on the importance and relevance of bioprinting technology in the construction of tumor models. Research progress in the bioprinting of monocellular, multicellular, and personalized tumor models is discussed, and comprehensive application of bioprinting in preclinical drug screening and innovative therapy is reviewed. Finally, we offer our perspective on the shortcomings of the existing models and explore new technologies to outline the direction of future development and application prospects of next-generation tumor models.

Multiple functions of microfluidic platforms: Characterization and applications in tissue engineering and diagnosis of cancer

Microfluidic system, or lab-on-a-chip, has grown explosively. This system has been used in research for the first time and then entered in the clinical section. Due to economic reasons, this technique has been used for screening of laboratory and clinical indices. The microfluidic system solves some difficulties accompanied by clinical and biological applications. In this review, the interpretation and analysis of some recent developments in microfluidic systems in biomedical applications with more emphasis on tissue engineering and cancer will be discussed. Moreover, we try to discuss the features and functions of microfluidic systems.

Sheathless Inertial Focusing Chip Combining a Spiral Channel with Periodic Expansion Structures for Efficient and Stable Particle Sorting

Efficient and reliable manipulation of biological particles is crucial in medical diagnosis and chemical synthesis. Inertial microfluidic devices utilizing passive hydrodynamic forces in the secondary flow have drawn considerable attention for their high throughputs, low costs, and harmless particle manipulation. However, as the dominant mechanism, the inertial lift force is difficult to quantitatively analyze because of the uncertainties of its magnitude and direction. The equilibrium position of particles varies along the migration process, thus inducing the instabilities of particle separation. Herein, we present a designable inertial microfluidic chip combining a spiral channel with periodic expansion structures for the sheathless separation of particles with different sizes. The stable vortex-induced lift force arising from the periodic expansion and the Dean drag force significantly enhanced the focusing process and determined the final equilibrium position. The experimental results showed that over 99% of target particles could be isolated with the high target sample purity of 86.12%. In the biological experiment, 93.5% of the MCF-7, 89.5% of the Hela, and 88.6% of the A549 cells were steadily recovered with excellent viabilities to verify the potential of the device in dealing with biological particles over a broad range of throughputs. The device presented in this study can further serve as a lab-on-chip platform for liquid biopsy and diagnostic analysis.

Microfluidics for label-free sorting of rare circulating tumor cells

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

Circulating Tumor Cells in Gastrointestinal Cancers: Current Status and Future Perspectives

Circulating tumor cells (CTCs), which are now defined as the "break away" cancer cells that derive from primary- or metastatic-tumor sites and present in the bloodstream, are considered to be the precursors of metastases. Considering the key role of CTCs in cancer progression, researchers are committed to analyze them in the past decades and many technologies have been proposed for achieving CTCs isolation and characterization with highly sensitivity and specificity until now. On this basis, clinicians gradually realize the clinical values of CTCs' detection through various clinical studies. As a "liquid biopsy," CTCs' detection and measurement can supply important information for predicting patient's survival, monitoring of response/resistance, assessment of minimal residual disease, evaluating distant metastasis, and sometimes, customizing therapy choices. Nowadays, eliminating CTCs of the blood circulation has been regarded as a promising method to prevent tumor metastasis. However, research on CTCs still faces many challenges. Herein, we present an overview to discuss the current concept of CTCs, summarize the available techniques for CTCs detection, and provide an update on the clinical significance of CTCs in gastrointestinal malignancies, especially focus on gastric and colorectal cancer.

A Dual-Targeting Functionalized Graphene Film for Rapid and Highly Sensitive Fluorescence Imaging Detection of Hepatocellular Carcinoma Circulating Tumor Cells

High recurrence and metastasis rates are the major causes of the high mortality of hepatocellular carcinoma (HCC). Circulating tumor cells (CTCs) disseminating into the bloodstream play an essential role in cancer metastasis. However, since HCC-CTCs are extremely rare, limitations of current detection methods impede accurate discerning of HCC-CTCs under complicated biological context. Here, a dual-targeting functionalized reduced graphene oxide film (DTFGF) for specifically identifying HCC-CTCs was created via coinstantaneous targeting epithelial cell adhesion molecule (EpCAM) and HCC cell-specific asialoglycoprotein receptor (ASGPR). Anti-EpCAM antibodies and galactose-rhodamine-polyacrylamide nanoparticles (Gal-Rh-PAA NPs) specifically recognizing ASGPR are modified on the surface of a graphene film that quenches the rhodamine fluorescence. HCC-CTCs can be captured by anti-EpCAM antibodies and endocytose Gal-Rh-PAA NPs, recovering the rhodamine fluorescence. Profiting from the accuracy of dual-targeting, less handling steps, and high resolution of fluorescence imaging, a simple, rapid, and low-cost HCC-CTC enumeration method is established with excellent sensitivity and selectivity than conventional methods. Using DTFGFs, as low as five HCC-CTCs were detected in a 1 mL blood sample. Further results revealed that larger HCC-CTC quantities indicate more advanced stages of HCC in patients. Overall, this work holds great promise for the early diagnosis, prognosis, and therapeutic evaluation of HCC.

Recent advances in microfluidic methods in cancer liquid biopsy

Early cancer detection, its monitoring, and therapeutical prediction are highly valuable, though extremely challenging targets in oncology. Significant progress has been made recently, resulting in a group of devices and techniques that are now capable of successfully detecting, interpreting, and monitoring cancer biomarkers in body fluids. Precise information about malignancies can be obtained from liquid biopsies by isolating and analyzing circulating tumor cells (CTCs) or nucleic acids, tumor-derived vesicles or proteins, and metabolites. The current work provides a general overview of the latest on-chip technological developments for cancer liquid biopsy. Current challenges for their translation and their application in various clinical settings are discussed. Microfluidic solutions for each set of biomarkers are compared, and a global overview of the major trends and ongoing research challenges is given. A detailed analysis of the microfluidic isolation of CTCs with recent efforts that aimed at increasing purity and capture efficiency is provided as well. Although CTCs have been the focus of a vast microfluidic research effort as the key element for obtaining relevant information, important clinical insights can also be achieved from alternative biomarkers, such as classical protein biomarkers, exosomes, or circulating-free nucleic acids. Finally, while most work has been devoted to the analysis of blood-based biomarkers, we highlight the less explored potential of urine as an ideal source of molecular cancer biomarkers for point-of-care lab-on-chip devices.

Detection of circulating tumor cells in blood by shell-isolated nanoparticle - enhanced Raman spectroscopy (SHINERS) in microfluidic device

Isolation and detection of circulating tumor cells (CTCs) from human blood plays an important role in non- invasive screening of cancer evolution and in predictive therapeutic treatment. Here, we present the novel tool utilizing: (i) the microfluidic device with (ii) incorporated photovoltaic (PV) based SERS-active platform, and (iii) shell-isolated nanoparticles (SHINs) for simultaneous separation and label-free analysis of circulating tumour cells CTCs in the blood specimens with high specificity and sensitivity. The proposed microfluidic chip enables the efficient size - based inertial separation of circulating cancer cells from the whole blood samples. The SERS-active platform incorporated into the microfluidic device permits the label-free detection and identification of isolated cells through the insight into their molecular and biochemical structure. Additionally, the silver nanoparticles coated with an ultrathin shell of silica (Ag@SiO2) was used to improve the detection accuracy and sensitivity of analysed tumor cells via taking advantages of shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). The empirical analysis of SHINERS spectra revealed that there are some differences among studied (HeLa), renal cell carcinoma (Caki-1), and blood cells. Unique SHINERS features and differences in bands intensities between healthy and cancer cells might be associated with the variations in the quantity and quality of molecules such as lipid, protein, and DNA or their structure during the metastasis cancer formation. To demonstrate the statistical efficiency of the developed method and improve the differentiation for circulating tumors cells detection the principal component analysis (PCA) has been performed for all SHINERS data. PCA method has been applied to recognize the most significant differences in SHINERS data among the three analyzed cells: Caki-1, HeLa, and blood cells. The proposed approach challenges the current multi-steps CTCs detection methods in the terms of simplicity, sensitivity, invasiveness, destructivity, time and cost of analysis, and also prevents the defragmentation/damage of tumor cells and thus leads to improving the accuracy of analysis. The results of this research work show the potential of developed SERS based tool for the separation of tumor cells from whole blood samples in a simple and minimally invasive manner, their detection and molecular characterization using one single technology.

Technologies for circulating tumor cell separation from whole blood

The importance of early cancer diagnosis and improved cancer therapy has been clear for years and has initiated worldwide research towards new possibilities in the care strategy of patients with cancer using technological innovations. One of the key research fields involves the separation and detection of circulating tumor cells (CTC) because of their suggested important role in early cancer diagnosis and prognosis, namely, providing easy access by a liquid biopsy from blood to identify metastatic cells before clinically detectable metastasis occurs and to study the molecular and genetic profile of these metastatic cells. Provided the opportunity to further progress the development of technology for treating cancer, several CTC technologies have been proposed in recent years by various research groups and companies. Despite their potential role in cancer healthcare, CTC methods are currently mainly used for research purposes, and only a few methods have been accepted for clinical application because of the difficulties caused by CTC heterogeneity, CTC separation from the blood, and a lack of thorough clinical validation. Therefore, the standardization and clinical application of various developed CTC technologies remain important subsequent necessary steps. Because of their suggested future clinical benefits, we focus on describing technologies using whole blood samples without any pretreatment and discuss their advantages, use, and significance. Technologies using whole blood samples utilize size-based, immunoaffinity-based, and density-based methods or combinations of these methods as well as positive and negative enrichment during separation. Although current CTC technologies have not been truly implemented yet, they possess high potential as future clinical diagnostic techniques for the individualized therapy of patients with cancer. Thus, a detailed discussion of the clinical suitability of these new advanced technologies could help prepare clinicians for the future and can be a foundation for technologies that would be used to eliminate CTCs in vivo.

Molecular detection of epithelial-mesenchymal transition markers in circulating tumor cells from pancreatic cancer patients: Potential role in clinical practice

AIM

To evaluate the clinical properties of three subpopulations of circulating tumor cells (CTCs) undergoing epithelial-mesenchymal transition (EMT) in pancreatic ductal adenocarcinoma (PDAC) patients.

METHODS

We identified CTCs for expression of the epithelial cell marker cytokeratin or epithelial cell adhesion molecule (EpCAM) (E-CTC), the mesenchymal cell markers vimentin and twist (M-CTC), or both (E/M-CTC) using the CanPatrol system. Between July 2014 and July 2016, 107 patients with PDAC were enrolled for CTC evaluation. CTC enumeration and classification were correlated with patient clinicopathological features and outcomes.

RESULTS

CTCs were detected in 78.5% of PDAC patients. The number of total CTCs ranged from 0 to 26 across all 107 patients, with a median value of six. CTC status correlated with lymph node metastasis, TNM stage, distant metastasis, blood lymphocyte counts, and neutrophil-to-lymphocyte ratio (NLR). Kaplan-Meier survival analysis showed that patients with ≥ 6 total CTCs had significantly decreased overall survival and progression-free survival compared with patients with < 6 total CTCs. The presence of M-CTCs was positively correlated with TNM stage (P < 0.01) and distant metastasis (P < 0.01). Additionally, lymphocyte counts and NLR in patients without CTCs were significantly different from those in patients testing positive for each CTC subpopulation (P < 0.01).

CONCLUSION

Classifying CTCs by EMT markers helps to identify the more aggressive CTC subpopulations and provides useful evidence for determining a suitable clinical approach.

Development of a microfluidic platform for size-based hydrodynamic enrichment and PSMA-targeted immunomagnetic isolation of circulating tumour cells in prostate cancer

Efforts to further improve the clinical management of prostate cancer (PCa) are hindered by delays in diagnosis of tumours and treatment deficiencies, as well as inaccurate prognoses that lead to unnecessary or inefficient treatments. The quantitative and qualitative analysis of circulating tumour cells (CTCs) may address these issues and could facilitate the selection of effective treatment courses and the discovery of new therapeutic targets. Therefore, there is much interest in isolation of elusive CTCs from blood. We introduce a microfluidic platform composed of a multiorifice flow fractionation (MOFF) filter cascaded to an integrated microfluidic magnetic (IMM) chip. The MOFF filter is primarily employed to enrich immunomagnetically labeled blood samples by size-based hydrodynamic removal of free magnetic beads that must originally be added to samples at disproportionately high concentrations to ensure the efficient immunomagnetic labeling of target cancer cells. The IMM chip is then utilized to capture prostate-specific membrane antigen-immunomagnetically labeled cancer cells from enriched samples. Our preclinical studies showed that the proposed method can selectively capture up to 75% of blood-borne PCa cells at clinically-relevant low concentrations (as low as 5 cells/ml), with the IMM chip showing up to 100% magnetic capture capability.