Three-Dimensional Scaffold Chip with Thermosensitive Coating for Capture and Reversible Release of Individual and Cluster of Circulating Tumor Cells

Endogenously Gated DNA Walking Machine for Prescreened MicroRNA Detection in Extracellular Vesicles

Tumor-derived extracellular vesicle (T-EV) microRNAs have been investigated as promising biomarkers in clinical diagnosis as well as disease progression monitoring. However, the expression profiles of microRNA in different tissues vary widely, the precise monitoring of microRNA levels in EVs originating from diseased tissues is susceptible to background interference, thus remains a challenge. Conventional assays require extensive processing, such as EV isolation and even sample lysis, which is both slow and laborious, and the cumbersome pretreatment could spoil the downstream analysis. To address this issue, we developed a generalizable strategy for T-EVs-selective activation and therefore specific amplified microRNA imaging. The conditional signal amplification is established by integrating a traditional DNA walker system with endogenously activated motif to achieve sensitized microRNA imaging in T-EVs. The preorganized endogenous activation with additional sensing criteria narrowed the scope against the complex specimens, and the amplified sensing with reduced off-target signals was supposed to be sensitive to monitor the tiny changes of microRNA expression during the disease course, which holds great potential for accurate diagnosis and prognosis.

The application, safety, and future of ex vivo immune cell therapies and prognosis in different malignancies

Introduction

Immunotherapy has revolutionized how cancer is treated. Many of these immunotherapies rely on ex vivo expansion of immune cells, classically T cells. Still, several immunological obstacles remain, including tumor impermeability by immune cells and the immunosuppressive nature of the tumor microenvironment (TME). Logistically, high costs of treatment and variable clinical responses have also plagued traditional T cell-based immunotherapies.

Methods

To review the existing literature on cellular immunotherapy, the PubMed database was searched for publications using variations of the phrases "cancer immunotherapy", "ex vivo expansion", and "adoptive cell therapy". The Clinicaltrials.gov database was searched for clinical trials related to ex vivo cellular therapies using the same phrases. The National Comprehensive Cancer Network guidelines for cancer treatment were also referenced.

Results

To circumvent the challenges of traditional T cell-based immunotherapies, researchers have developed newer therapies including tumor infiltrating lymphocyte (TIL), chimeric antigen receptor (CAR), T cell receptor (TCR) modified T cell, and antibody-armed T cell therapies. Additionally, newer immunotherapeutic strategies have used other immune cells, including natural killer (NK) and dendritic cells (DC), to modulate the T cell immune response to cancers. From a prognostic perspective, circulating tumor cells (CTC) have been used to predict cancer morbidity and mortality.

Conclusion

This review highlights the mechanism and clinical utility of various types of ex vivo cellular therapies in the treatment of cancer. Comparing these therapies or using them in combination may lead to more individualized and less toxic chemotherapeutics.

Exploring the Potential Driver Gene Mutations That Promote Renal Cancer Cell Metastasis and Implantation Based on Circulating Tumor Cells Culture

Studies have shown that the circulating tumor cell (CTC) is a necessary condition for the invasion and distant metastasis of renal cell carcimona (RCC). However, few CTCs-related gene mutations have been developed which could promote the metastasis and implantation of RCC. The objective of this study is to explore the potential driver gene mutations that promote RCC metastasis and implantation based on CTCs culture. Fifteen patients with primary mRCC and three healthy subjects were included, and peripheral blood was obtained. After the preparation of synthetic biological scaffolds, peripheral blood CTCs were cultured. Successful cultured CTCs were applied to construct CTCs-derived xenograft (CDX) models, followed by DNA extraction, whole exome sequencing (WES) and bioinformatics analysis. Synthetic biological scaffolds were constructed based on previously applied techniques, and peripheral blood CTCs culture was successfully performed. We then constructed CDX models and performed WES, and explored the potential driver gene mutations that may promote RCC metastasis and implantation. Bioinformatics analysis showed that KAZN and POU6F2 may be closely related to the prognosis of RCC. We successfully performed the culture of peripheral blood CTCs and, on this basis we initially explored the potential driver mutations for the metastasis and implantation of RCC.

Conductive Nanofibers-Enhanced Microfluidic Device for the Efficient Capture and Electrical Stimulation-Triggered Rapid Release of Circulating Tumor Cells

The effective detection and release of circulating tumor cells (CTCs) are of great significance for cancer diagnosis and monitoring. The microfluidic technique has proved to be a promising method for CTCs isolation and subsequent analysis. However, complex micro-geometries or nanostructures were often constructed and functionalized to improve the capture efficiency, which limited the scale-up for high-throughput production and larger-scale clinical applications. Thus, we designed a simple conductive nanofiber chip (CNF-Chip)-embedded microfluidic device with a herringbone microchannel to achieve the efficient and specific capture and electrical stimulation-triggered rapid release of CTCs. Here, the most used epithelial cell adhesion molecule (EpCAM) was selected as the representative biomarker, and the EpCAM-positive cancer cells were mainly studied. Under the effects of the nanointerface formed by the nanofibers with a rough surface and the herringbone-based high-throughput microfluidic mixing, the local topographic interaction between target cells and nanofibrous substrate in the microfluidic was synergistically enhanced, and the capture efficiency for CTCs was further improved (more than 85%). After capture, the sensitive and rapid release of CTCs (release efficiency above 97%) could be conveniently achieved through the cleavage of the gold-sulfur bond by applying a low voltage (-1.2 V). The device was successfully used for the effective isolation of CTCs in clinical blood samples from cancer patients, indicating the great potential of this CNF-Chip-embedded microfluidic device in clinical applications.

Three-Dimensional PLGA Nanofiber-Based Microchip for High-Efficiency Cancer Cell Capture

A 3D network capture substrate based on poly(lactic-co-glycolic acid) (PLGA) nanofibers was studied and successfully used for high-efficiency cancer cell capture. The arc-shaped glass micropillars were prepared by chemical wet etching and soft lithography. PLGA nanofibers were coupled with micropillars by electrospinning. Given the size effect of the microcolumn and PLGA nanofibers, a three-dimensional of micro-nanometer spatial network was prepared to form a network cell trapping substrate. After the modification of a specific anti-EpCAM antibody, MCF-7 cancer cells were captured successfully with a capture efficiency of 91%. Compared with the substrate composed of 2D nanofibers or nanoparticles, the developed 3D structure based on microcolumns and nanofibers had a greater contact probability between cells and the capture substrate, leading to a high capture efficiency. Cell capture based on this method can provide technical support for rare cells in peripheral blood detection, such as circulating tumor cells and circulating fetal nucleated red cells.

Glucometer Readout for Portable Detection of Heterogeneous Circulating Tumor Cells in Lung Cancer Captured on a Dual Aptamer Functionalized Wrinkled Cellulose Hydrogel Interface

The rarity of circulating tumor cells (CTCs) poses a great challenge to their clinical application as reliable "liquid biopsy" markers for cancer diagnosis. Meanwhile, the epithelial-mesenchymal transition (EMT) led to a reduced efficiency in capturing cells with lost or downregulated epithelial cell adhesion molecule (EpCAM) expressions. In this study, we proposed an integrated, highly efficient strategy for heterogeneous CTC capture and portable detection from the blood of non-small-cell lung cancer (NSCLC) patients. First, the cellulose wrinkled hydrogel with excellent biocompatibility and high specific area was employed as the biointerface to capture heterogeneous CTCs with an improved capture efficiency in virtue of dual targeting against epithelial and mesenchymal ones. Meanwhile, the strategy of glucometer readout was introduced for the quantification of captured CTCs on the same hydrogel interface by a detection probe, Au-G-MSN-Apt, which was fabricated via entrapping glucose into the amino group functionalized mesoporous silica nanoparticle (MSN) framework sealed by l-cysteine modified gold nanoparticles (AuNPs) and then linked with dual aptamers of EpCAM and Vimentin. The number of captured CTCs on the hydrogel could be reflected according to the portable glucose meter (PGM) readings. Moreover, it was found that the captured cells maintained a higher viability on the hydrogel and could be in situ recultured without releasing from the substrate. Finally, this integrated strategy was successfully applied to inspect the correlations between the number of heterogeneous CTCs in the blood of NSCLC patients with disease stage and whether there was distant metastasis.

Role of m6A RNA methylation in the development of hepatitis B virus-associated hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common liver malignancy that can be developed from hepatitis B and cirrhosis. Many pathophysiological alterations, including hepatitis B virus (HBV) DNA integration, oxidative stress, cytokine release, telomerase homeostasis, mitochondrial damage, epigenetic modification, and tumor microenvironment, are involved in the biological process from hepatitis B to cirrhosis and HCC. N6-methyladenosine (m6A), as an epitranscriptomic modification of RNAs, can regulate the stability, splicing, degradation, transcription, and translation of downstream target RNAs in HBV and liver cancer cells. m6A regulators (writers, erasers, and readers) play an important role in the pathogenesis of HBV-associated HCC by regulating cell proliferation, apoptosis, migration, autophagy, differentiation, inflammation, angiogenesis, and tumor microenvironment. This review summarizes the current progress of m6A methylation in the molecular mechanisms, biological functions, and potential clinical implications of HBV-associated HCC.

Facile Preparation of Three-Dimensional Wafer with Interconnected Porous Structure for High-Performance Capture and Nondestructive Release of Circulating Tumor Cells

Efficient isolation and downstream bioinformation analysis of circulating tumor cells (CTCs) in whole blood contribute to the early diagnosis of cancer and investigation of cancer metastasis. However, the separation and release of CTCs remain a great challenge due to the extreme rarity of CTCs and severe interference from other cells in complex clinical samples. Herein, we developed a low-cost and easy-to-fabricate aptamer-functionalized wafer with a three-dimensional (3D) interconnected porous structure by grafting polydopamine (PDA), poly(ethylene glycol) (PEG), and aptamer in sequence (Ni@PDA-PEG-Apt) for the capture and release of CTCs. The Ni@PDA-PEG-Apt wafer integrated the features of Ni foam with a 3D interconnected porous structure offering enough tunnels for cells to flow through and enhancing aptamer-cell contact frequency, the spacer PEG with flexible and high hydrophilic property increasing anti-interference ability and providing the wafer with more binding sites for aptamer, which result in an enhanced capture specificity and efficiency for CTCs. Because of these advantages, the Ni@PDA-PEG-Apt wafer achieved a high capture efficiency of 78.25%. The captured cancer cells were mildly released by endonuclease with up to 61.85% efficiency and good proliferation. Furthermore, tumor cells were injected into mice and experienced circulation in vivo. In blood samples after circulation, 65% of target tumor cells can be efficiently captured by the wafer, followed by released and recultured cells with high viability. Further downstream metabolomics analysis showed that target cancer cells remained with high biological activity and can be well separated from MCF-10A cells based on metabolic profiles by the PCA analysis, indicating the great potential of our strategy for further research on the progression of cancer metastasis. Notably, not only is the wafer cheap with a cost of only 3.58 U.S. dollars and easily prepared by environmental-friendly reagents but also the process of capturing and releasing tumor cells can be completed within an hour, which is beneficial for large-scale clinical use in the future.

Microfluidic techniques for isolation, formation, and characterization of circulating tumor cells and clusters

Circulating tumor cell (CTC) clusters that are shed from the primary tumor into the bloodstream are associated with a poor prognosis, elevated metastatic potential, higher proliferation rate, and distinct molecular features compared to single CTCs. Studying CTC clusters may give us information on the differences in the genetic profiles, somatic mutations, and epigenetic changes in circulating cells compared to the primary tumor and metastatic sites. Microfluidic systems offer the means of studying CTC clusters through the ability to efficiently isolate these rare cells from the whole blood of patients in a liquid biopsy. Microfluidics can also be used to develop in vitro models of CTC clusters and make possible their characterization and analysis. Ultimately, microfluidic systems can offer the means to gather insight on the complexities of the metastatic process, the biology of cancer, and the potential for developing novel or personalized therapies. In this review, we aim to discuss the advantages and challenges of the existing microfluidic systems for working with CTC clusters. We hope that an improved understanding of the role microfluidics can play in isolation, formation, and characterization of CTC clusters, which can lead to increased sophistication of microfluidic platforms in cancer research.

Ulex Europaeus Agglutinin-I-Based Magnetic Isolation for the Efficient and Specific Capture of SW480 Circulating Colorectal Tumor Cells

The efficient and specific capture of circulating tumor cells (CTCs) from patients' peripheral blood is of significant value in precise cancer diagnosis and cancer therapy. As fine targeting molecules, lectins can recognize cancer cells specifically due to the abnormal glycosylation of molecules on the cancer cell membrane and the specific binding of lectin with glycoconjugates. Herein, a Ulex europaeus agglutinin-I (UEA-I)-based magnetic isolation strategy was developed to efficiently and specifically capture α-1,2-fucose overexpression CTCs from colorectal cancer (CRC) patients' peripheral blood. Using UEA-I-modified Fe₃O₄ magnetic beads (termed MB-UEA-I), up to 94 and 89% of target cells (i.e., SW480 CRC cells) were captured from the cell spiking complete cell culture medium and whole blood, respectively. More than 90% of captured cells show good viability and proliferation ability without detaching from MB-UEA-I. In combination with three-color immunocytochemistry (ICC) identification, MB-UEA-I has been successfully used to capture CTCs from CRC patients' peripheral blood. The experimental results indicate a correlation between CTC characterization and tumor metastasis. Specifically, MB-UEA-I can be applied to screen early CRC by capturing CTCs when served as a liquid biopsy. The presented work offers a new insight into developing cost-effective lectin-functionalized methods for biomedical applications.

An electroactive microwell array device to realize simultaneous trapping of single cancer cells and clusters

The importance of circulating tumor cells (CTCs) as biomarkers has been greatly increased for early diagnosis and detection of cancer metastases. Along with a single form of CTCs, CTC clusters have recently attracted much attention due to their characteristics, such as suppression of apoptosis and survival from immune responses with high metastatic potential. Thus, it is highly necessary to investigate not only single cells but clustered cells at the same time to perform precise analysis of the current cancer state and develop suitable treatment. However, no cancer marker-free microfluidic devices have been realized to trap single cells and clusters at the same time in a single device yet. In this paper, we introduced a novel microfluidic device utilizing a microwell-on-electrode (MOE) array to realize simultaneous trapping of a single cell and clustered cells at a single cell/cluster level. Cell-sized microwells fabricated on interdigitated electrodes efficiently arrayed single cells with high trapping efficiency and single-cell occupancy (more than 90%) using dielectrophoresis (DEP). This high single cell trapping performance of MOE allows arraying of single clusters by trapping one of the cells that constitute a cluster. The feasibility of the MOE device for simultaneous arraying of single cancer cells and clusters was demonstrated by trapping a mixture of single cancer cells and clusters and measuring the size distribution of trapped clusters, which was almost identical with that of introduced cell population. Our work demonstrated that the developed MOE device can be one of the promising methods for trapping single cancer cells as well as clusters on a single device for cancer diagnosis and performing further analyses at a single cell/cluster level.

Electric field-assisted MnO2 nanomaterials for rapid capture and in situ delivery of circulating tumour cells

The heterogeneity of cancer has become a major obstacle to treatment, and the development of an efficient, fast, and accurate drug delivery system is even more urgent. In this work, we designed a device that integrated multiple functions of cell capture, in situ manipulation, and non-destructive release on a single device. With an applied electric field, an intelligent device based on MnO₂ nanomaterials was used to realize efficient and rapid capture of cancer cells in both patients' blood and artificial blood samples. This device could capture cancer cells with high efficiency (up to about 93%) and strong specificity in blood samples, the capture time was nearly 50 min faster than that of natural sedimentation, and reduce the effects on cells caused by long-time in vitro culture. In addition, Mn³⁺ on the surface of the MnO₂ substrate was reduced to Mn²⁺ by an electrochemical method, partial dissolution occurred, and then the captured cells were non-destructively released with rapid speed (about 8 s) and high efficiency (about 94 ± 2%). For in situ regulation, upon applying a pulse electric field, the captured cells were perforated nondestructively, and extracellular molecules could be delivered to the captured cells with well-performed dose and temporal controls. As a proof-of-concept application, we proved that the device could capture circulating tumor cells in peripheral blood faster and achieve in situ drug delivery. Finally, it can also quickly release circulating tumour cells for subsequent analysis, highlighting its accuracy, due to which it is widely used in medical treatment, basic tumor research and drug development.

Recent Advances in Microfluidic Platform for Physical and Immunological Detection and Capture of Circulating Tumor Cells

CTCs (circulating tumor cells) are well-known for their use in clinical trials for tumor diagnosis. Capturing and isolating these CTCs from whole blood samples has enormous benefits in cancer diagnosis and treatment. In general, various approaches are being used to separate malignant cells, including immunomagnets, macroscale filters, centrifuges, dielectrophoresis, and immunological approaches. These procedures, on the other hand, are time-consuming and necessitate multiple high-level operational protocols. In addition, considering their low efficiency and throughput, the processes of capturing and isolating CTCs face tremendous challenges. Meanwhile, recent advances in microfluidic devices promise unprecedented advantages for capturing and isolating CTCs with greater efficiency, sensitivity, selectivity and accuracy. In this regard, this review article focuses primarily on the various fabrication methodologies involved in microfluidic devices and techniques specifically used to capture and isolate CTCs using various physical and biological methods as well as their conceptual ideas, advantages and disadvantages.

Relevance of Circulating Tumor Cells as Predictive Markers for Cancer Incidence and Relapse

Shedding of cancer cells from the primary site or undetectable bone marrow region into the circulatory system, resulting in clinically overt metastasis or dissemination, is the hallmark of unfavorable invasive cancers. The shed cells remain in circulation until they extravasate to form a secondary metastatic lesion or undergo anoikis. The circulating tumor cells (CTCs) found as single cells or clusters carry a plethora of information, are acknowledged as potential biomarkers for predicting cancer prognosis and cancer progression, and are supposed to play key roles in determining tailored therapies for advanced diseases. With the advent of novel technologies that allow the precise isolation of CTCs, more and more clinical trials are focusing on the prognostic and predictive potential of CTCs. In this review, we summarize the role of CTCs as a predictive marker for cancer incidence, relapse, and response to therapy.

Specific capture and intact release of breast cancer cells using a twin-layer vein-shaped microchip with a self-assembled surface

Breast cancer is the most fatal disease among female cancers yet its detection still relies on needle biopsy. The unique physical and immune characteristics of breast cancer cells different from blood cells make them suitable to be employed as excellent biomarkers in liquid biopsy, through which breast cancer cells are collected from peripheral blood for further cancer diagnosis, medical treatment monitoring, and drug screening. Although the separation and enrichment of breast cancer cells from peripheral blood have been studied for years, there are still two problems to be solved in these methods: the low efficiency of on-chip immunologic capture in the flow state and the influence of the conjugated antibodies for the following analyses during cell release. In this paper, a vein-shaped microchip with self-assembled surface was developed for the specific and robust capture (91.2%) of breast cancer cells in the flow state. A protein-recovery process was proposed, in which trypsin served as a mild release reagent, releasing 92% of cells with high viability (96%), normal adherent proliferation, and complete proteins on the cell membrane, avoiding disturbance of the conjugated chemical molecules in the following clinical study. The excellent performance demonstrated in isolating free breast cancer cells from real peripheral blood sample, originating from the orthotopic 4T1 breast cancer metastatic models, suggest the microchip could be utilized as a multiple circulating tumor cell capture and release platform that could allow providing more reliable information in liquid biopsies.

Better together: circulating tumor cell clustering in metastatic cancer

Circulating tumor cells (CTCs) are vital components of liquid biopsies for diagnosis of residual cancer, monitoring of therapy response, and prognosis of recurrence. Scientific dogma focuses on metastasis mediated by single CTCs, but advancement of CTC detection technologies has elucidated multicellular CTC clusters, which are associated with unfavorable clinical outcomes and a 20- to 100-fold greater metastatic potential than single CTCs. While the mechanistic understanding of CTC cluster formation is still in its infancy, multiple cell adhesion molecules and tight junction proteins have been identified that underlie the outperforming attributes of homotypic and heterotypic CTC clusters, such as cell survival, cancer stemness, and immune evasion. Future directions include high-resolution characterization of CTCs at multiomic levels for diagnostic/prognostic evaluations and targeted therapies.

Enhancing interactions between cells and hierarchical micro/nanostructured TiO2films for efficient capture of circulating tumor cells

Micro/nano hierarchical substrates with different micropillar spacings were designed and prepared for capture of tumor cells. The cell capture efficiency of hierarchical substrates with low-density micropillar arrays was similar to that of nanostructured substrate. Increasing the density of micopillars could significantly improve the capture efficiency. The maximum capture efficiency was achieved on the hierarchical substrate with micropillar spacings of 15μm, but further reducing the micropillar spacings did not increase the cell capture efficiency. It was also found that hierarchical substrates with appropriate spacing of micropillars appeared more favorable for cell attachment and spreading, and thus enhancing the cell-material interaction. These results suggested that optimizing the micropillar arrays, such as the spacing between adjacent micropillars, could give full play to the synergistic effect of hierarchical hybrid micro/nanostructures in the interaction with cells. This study may provide promising guidance to design and optimize micro/nano hierarchical structures of biointerfaces for biomedical application.

A Three-Dimensional Conductive Scaffold Microchip for Effective Capture and Recovery of Circulating Tumor Cells with High Purity

Effective acquirement of highly pure circulating tumor cells (CTCs) is very important for CTC-related research. However, it is a great challenge since abundant white blood cells (WBCs) are always co-collected with CTCs because of nonspecific bonding or low depletion rate of WBCs in various CTC isolation platforms. Herein, we designed a three-dimensional (3D) conductive scaffold microchip for highly effective capture and electrochemical release of CTCs with high purity. The conductive 3D scaffold was prepared by dense immobilization of gold nanotubes (Au NTs) on porous polydimethylsiloxane and was functionalized with a CTC-specific biomolecule facilitated by a Au-S bond before embedding into a microfluidic device. The spatially distributed 3D macroporous structure compelled cells to change migration from linear to chaotic and the densely covered Au NTs enhanced the topographic interaction between cells and the substrate, thus synergistically improving the CTC capture efficiency. The Au NT-coated 3D scaffold had good electrical conductivity and the Au-S bond was breakable by voltage exposure so that captured CTCs could be specifically released by electrochemical stimulation while nonspecifically bonded WBCs were not responsive to this process, facilitating recovery of CTCs with high purity. The 3D conductive scaffold microchip was successfully applied to obtain highly pure CTCs from cancer patients' blood, benefiting the downstream analysis of CTCs.

Microtechnology-enabled filtration-based liquid biopsy: challenges and practical considerations

Liquid biopsy, an important enabling technology for early diagnosis and dynamic monitoring of cancer, has drawn extensive attention in the past decade. With the rapid developments of microtechnology, it has been possible to manipulate cells at the single-cell level, which dramatically improves the liquid biopsy capability. As the microtechnology-enabled liquid biopsy matures from proof-of-concept demonstrations towards practical applications, a main challenge it is facing now is to process clinical samples which are usually of a large volume while containing very rare targeted cells in complex backgrounds. Therefore, a high-throughput liquid biopsy which is capable of processing liquid samples with a large volume in a reasonable time along with a high recovery rate of rare targeted cells from complex clinical liquids is in high demand. Moreover, the purity, viability and release feasibility of recovered targeted cells are the other three key impact factors requiring careful considerations. To date, among the developed techniques, micropore-type filtration has been acknowledged as the most promising solution to address the aforementioned challenges in practical applications. However, the presently reported studies about micropore-type filtration are mostly based on trial and error for device designs aiming at different cancer types, which requires lots of efforts. Therefore, there is an urgent need to investigate and elaborate the fundamental theories of micropore-type filtration and key features that influence the working performances in the liquid biopsy of real clinical samples to promote the application efficacy in practical applications. In this review, the state of the art of microtechnology-enabled filtration is systematically and comprehensively summarized. Four key features of the filtration, including throughput, purity, viability and release feasibility of the captured targeted cells, are elaborated to provide the guidelines for filter designs. The recent progress in the filtration mode modulation and sample standardization to improve the filtration performance of real clinical samples is also discussed. Finally, this review concludes with prospective views for future developments of filtration-based liquid biopsy to promote its application efficacy in clinical practice.

Repurposing nano-enabled polymeric scaffolds for tumor-wound management and 3D tumor engineering

The main challenges of cancer drugs are toxicity, effect on wound healing/patient outcome and in vivo instability. Polymeric scaffolds have been used separately for tissue regeneration in wound healing and as anticancer drug releasing devices. Bringing these two together in bifunctional scaffolds can provide a tool for postoperative local tumor management by promoting healthy tissue regrowth and to deliver anticancer drugs. Another addition to the versatility of polymeric scaffold is its recently discovered ability to act as 3D cell culture models for in vitro isolation and amplification of cancer cells for personalized drug screening and to recapitulate the tumor microenvironment. This review focuses on the repurposing of 3D polymeric scaffolds for local tumor-wound management and development of in vitro cell culture models.

[Research Advances of m⁶A RNA Methylation in Non-small Cell Lung Cancer]

m⁶A修饰是真核生物mRNA中最丰富的修饰之一，该过程受m⁶A甲基转移酶和去甲基化酶的共同调控。m⁶A修饰后的RNA能够被m⁶A识别蛋白特异性识别并结合，进而介导RNA的剪接、成熟、出核、降解和翻译等。目前国内外对于m⁶A修饰及其相关蛋白如何参与非小细胞肺癌发生发展的研究，主要集中于细胞恶性增殖、迁移、侵袭、转移和耐药等方面。m⁶A修饰相关蛋白在肺癌组织标本和血液循环肿瘤细胞（circulating tumor cell, CTC）中表达异常，有望成为肺癌诊断和预后判断的潜在分子标志物。本文围绕m⁶A修饰相关蛋白的组成、作用方式、在非小细胞肺癌恶性进展中的生物学功能，以及针对m⁶A修饰的靶向治疗等方面的研究进展进行综述，旨在为非小细胞肺癌的早期临床诊断和靶向药物的开发提供新思路。

Circulating tumor cells as Trojan Horse for understanding, preventing, and treating cancer: a critical appraisal

Circulating tumor cells (CTCs) are regarded as harbingers of metastases. Their ability to predict response to therapy, relapse, and resistance to treatment has proposed their value as putative diagnostic and prognostic indicators. CTCs represent one of the zeniths of cancer evolution in terms of cell survival; however, the triggers of CTC generation, the identification of potentially metastatic CTCs, and the mechanisms contributing to their heterogeneity and aggressiveness represent issues not yet fully deciphered. Thus, prior to enabling liquid biopsy applications to reach clinical prime time, understanding how the above mechanistic information can be applied to improve treatment decisions is a key challenge. Here, we provide our perspective on how CTCs can provide mechanistic insights into tumor pathogenesis, as well as on CTC clinical value. In doing so, we aim to (a) describe how CTCs disseminate from the primary tumor, and their link to epithelial-mesenchymal transition (EMT); (b) trace the route of CTCs through the circulation, focusing on tumor self-seeding and the possibility of tertiary metastasis; (c) describe possible mechanisms underlying the enhanced metastatic potential of CTCs; (d) discuss how CTC could provide further information on the tissue of origin, especially in cancer of unknown primary origin. We also provide a comprehensive review of meta-analyses assessing the prognostic significance of CTCs, to highlight the emerging role of CTCs in clinical oncology. We also explore how cell-free circulating tumor DNA (ctDNA) analysis, using a combination of genomic and phylogenetic analysis, can offer insights into CTC biology, including our understanding of CTC heterogeneity and tumor evolution. Last, we discuss emerging technologies, such as high-throughput quantitative imaging, radiogenomics, machine learning approaches, and the emerging breath biopsy. These technologies could compliment CTC and ctDNA analyses, and they collectively represent major future steps in cancer detection, monitoring, and management.

Nanotechnology-Assisted Isolation and Analysis of Circulating Tumor Cells on Microfluidic Devices

Circulating tumor cells (CTCs), a type of cancer cell that spreads from primary tumors into human peripheral blood and are considered as a new biomarker of cancer liquid biopsy. It provides the direction for understanding the biology of cancer metastasis and progression. Isolation and analysis of CTCs offer the possibility for early cancer detection and dynamic prognosis monitoring. The extremely low quantity and high heterogeneity of CTCs are the major challenges for the application of CTCs in liquid biopsy. There have been significant research endeavors to develop efficient and reliable approaches to CTC isolation and analysis in the past few decades. With the advancement of microfabrication and nanomaterials, a variety of approaches have now emerged for CTC isolation and analysis on microfluidic platforms combined with nanotechnology. These new approaches show advantages in terms of cell capture efficiency, purity, detection sensitivity and specificity. This review focuses on recent progress in the field of nanotechnology-assisted microfluidics for CTC isolation and detection. Firstly, CTC isolation approaches using nanomaterial-based microfluidic devices are summarized and discussed. The different strategies for CTC release from the devices are specifically outlined. In addition, existing nanotechnology-assisted methods for CTC downstream analysis are summarized. Some perspectives are discussed on the challenges of current methods for CTC studies and promising research directions.

Update on Circulating Tumor Cells in Genitourinary Tumors with Focus on Prostate Cancer

Current developments in the treatment of genitourinary tumors underline the unmet clinical need for biomarkers to improve decision-making in a challenging clinical setting. The detection of circulating tumor cells (CTCs) has become one of the most exciting and important new approaches to identifying biomarkers at different stages of disease in a non-invasive way. Potential applications of CTCs include monitoring treatment efficacy and early detection of progression, selecting tailored therapies, as well as saving treatment costs. However, despite the promising implementation of CTCs in a clinical scenario, the isolation and characterization of these cells for molecular studies remain expensive with contemporary platforms, and significant technical challenges still need to be overcome. This updated, critical review focuses on the state of CTCs in patients with genitourinary tumor with focus on prostate cancer, discussing technical issues, main clinical results and hypothesizing potential future perspectives in clinical scenarios.

Relevance of CTC Clusters in Breast Cancer Metastasis

Metastasis is the major cause of mortality in patients with breast cancer; however, the mechanisms of tumor cell dissemination and metastasis formation are not well established yet. The study of circulating tumour cells (CTCs), the metastatic precursors of distant disease, may help in this search. CTCs can be found in the blood of cancer patients as single cells or as tumor cell aggregates, known as CTC clusters. CTC clusters have differential biological features such as an enhanced survival and metastatic potential, and they hold great promises for the evaluation of prognosis, diagnosis and therapy of the metastatic cancer. The analysis of CTC clusters offers new insights into the mechanism of metastasis and can guide towards the development of new diagnostic and therapeutic strategies to suppress cancer metastasis. This has become possible thanks to the development of improved technologies for detection of CTCs and CTC clusters. However, more efficient methods are needed in order to address important questions regarding the metastatic potential of CTC and future clinical applications. In this chapter, we explore the current knowledge on the role of CTC clusters in breast cancer metastasis, their origin, metastatic advantages and clinical importance.

Circulating Tumor Cell Clusters: United We Stand Divided We Fall

The presence of circulating tumor cells (CTCs) and CTC clusters, also known as tumor microemboli, in biological fluids has long been described. Intensive research on single CTCs has made a significant contribution in understanding tumor invasion, metastasis tropism, and intra-tumor heterogeneity. Moreover, their being minimally invasive biomarkers has positioned them for diagnosis, prognosis, and recurrence monitoring tools. Initially, CTC clusters were out of focus, but major recent advances in the knowledge of their biogenesis and dissemination reposition them as critical actors in the pathophysiology of cancer, especially metastasis. Increasing evidence suggests that "united" CTCs, organized in clusters, resist better and carry stronger metastatic capacities than "divided" single CTCs. This review gathers recent insight on CTC cluster origin and dissemination. We will focus on their distinct molecular package necessary to resist multiple cell deaths that all circulating cells normally face. We will describe the molecular basis of their increased metastatic potential as compared to single CTCs. We will consider their clinical relevance as prognostic biomarkers. Finally, we will propose future directions for research and clinical applications in this promising topic in cancer.

Flexible Three-Dimensional Net for Intravascular Fishing of Circulating Tumor Cells

Current strategies for in vitro isolation of circulating tumor cells (CTCs) fail to detect extremely rare CTCs heterogeneously distributed in blood. It is possible to devise methods for in vivo capture of CTCs based on processing almost all of the blood in the human body to improve detection sensitivity, but the complicated manipulation, biosafety concerns, and limited capture efficiency of conventional detection strategies prohibit their implementation in the clinic. Herein, we present a flexible three-dimensional (3-D) CTC-Net probe for intravascular collection of CTCs. The CTC-Net, consisting of a 3-D elastic scaffold with an interconnected, spatially distributed network accommodates a large quantity of immobilized antibodies and provides an enhanced substrate-cell contact frequency, which results in an enhanced capture efficiency and effective detection of heterogeneous CTCs. The as-prepared CTC-Net can be readily compressed and injected into blood vessels and fully unfolded to form a 3-D "fishing-net" structure for capture of the CTCs, and then retracted for imaging and downstream gene analysis of the captured CTCs. Significant advantages for the CTC-Net over currently available in vitro and in vivo procedures are demonstrated for detection of extremely rare CTCs from wild-type rats and successful capture of CTCs and CTC clusters before metastasis in the case of tumor-bearing rats. Our research demonstrates for the first time the use of a 3-D scaffold CTC-Net probe for in vivo capture of CTCs. The method shows exceptional performance for cell capture, which is readily implemented and holds great potential in the clinic for early diagnosis of cancer.

Aminophenylboronic Acid-Functionalized Thorny-Trap-Shaped Monolayer Microarray for Efficient Capture and Release of Circulating Tumor Cells

An aminophenylboronic acid (APBA)-functionalized thorny-trap-shaped monolayer microarray as a 3D fractal structures' substrate was fabricated to capture and release circulating tumor cells (CTCs) efficiently. The microarray can not only trap cells inside by microbowls but also enhance the interaction between cell and substrate by providing more binding sites and facilitating the spread of cell filopodias via the growth of nanorods. Modification of APBA enhanced the interaction further by binding with sialic acid of CTCs surface. The special topological structure achieved a high capture efficiency of 79.5%. The captured cancer cells were released without introducing any affinity molecules by a ligand exchange reaction with up to 70% efficiency and good proliferation. This substrate can isolate 33 tumor cells from a mimic blood sample even at a low spiked number of 50 cancer cells. This study provides valuable guidance for isolation and release of CTCs and is significant for the further study of tumors.

Affinity-Enhanced CTC-Capturing Hydrogel Microparticles Fabricated by Degassed Mold Lithography

Technologies for the detection and isolation of circulating tumor cells (CTCs) are essential in liquid biopsy, a minimally invasive technique for early diagnosis and medical intervention in cancer patients. A promising method for CTC capture, using an affinity-based approach, is the use of functionalized hydrogel microparticles (MP), which have the advantages of water-like reactivity, biologically compatible materials, and synergy with various analysis platforms. In this paper, we demonstrate the feasibility of CTC capture by hydrogel particles synthesized using a novel method called degassed mold lithography (DML). This technique increases the porosity and functionality of the MPs for effective conjugation with antibodies. Qualitative fluorescence analysis demonstrates that DML produces superior uniformity, integrity, and functionality of the MPs, as compared to conventional stop flow lithography (SFL). Analysis of the fluorescence intensity from porosity-controlled MPs by each reaction step of antibody conjugation elucidates that more antibodies are loaded when the particles are more porous. The feasibility of selective cell capture is demonstrated using breast cancer cell lines. In conclusion, using DML for the synthesis of porous MPs offers a powerful method for improving the cell affinity of the antibody-conjugated MPs.

High-Efficiency Isolation and Rapid Identification of Heterogeneous Circulating Tumor Cells (CTCs) Using Dual-Antibody-Modified Fluorescent-Magnetic Nanoparticles

Extreme rarity and inherent heterogeneity of circulating tumor cells (CTCs) result in a tremendous challenge for the CTC isolation from patient blood samples with high efficiency and purity. Current CTC isolation approaches mainly rely on the epithelial cell adhesion molecule (EpCAM), which may significantly reduce the ability to capture CTCs when the expression of EpCAM is lost or down-regulated in epithelial-mesenchymal transition. Here, a rapid and highly efficient method is developed to isolate and identify heterogeneous CTCs with high efficiency from patient blood samples using the fluorescent-magnetic nanoparticles (F-MNPs). A dual-antibody interface targeting EpCAM and N-cadherin is fabricated onto the F-MNPs to capture epithelial CTCs as well as mesenchymal CTCs from whole blood samples. The poly(carboxybetaine methacrylate) brushes of excellent antifouling properties are employed to decrease nonspecific cell adhesion. Moreover, the F-MNPs provide a prompt identification strategy for heterogeneous CTCs (F-MNPs+, Hoechst 33342+, and CD45-) that can directly identify CTCs in a gentle one-step processing within 1 h after isolation from patient blood samples. This has been demonstrated through artificial samples as well as patient samples in details.

Investigating circulating tumor cells and distant metastases in patient-derived orthotopic xenograft models of triple-negative breast cancer

BACKGROUND

Circulating tumor cells (CTCs) represent a temporal "snapshot" of a patient's cancer and changes that occur during disease evolution. There is an extensive literature studying CTCs in breast cancer patients, and particularly in those with metastatic disease. In parallel, there is an increasing use of patient-derived models in preclinical investigations of human cancers. Yet studies are still limited demonstrating CTC shedding and metastasis formation in patient-derived models of breast cancer.

METHODS

We used seven patient-derived orthotopic xenograft (PDOX) models generated from triple-negative breast cancer (TNBC) patients to study CTCs and distant metastases. Tumor fragments from PDOX tissue from each of the seven models were implanted into 57 NOD scid gamma (NSG) mice, and tumor growth and volume were monitored. Human CTC capture from mouse blood was first optimized on the marker-agnostic Vortex CTC isolation platform, and whole blood was processed from 37 PDOX tumor-bearing mice.

RESULTS

Staining and imaging revealed the presence of CTCs in 32/37 (86%). The total number of CTCs varied between different PDOX tumor models and between individual mice bearing the same PDOX tumors. CTCs were heterogeneous and showed cytokeratin (CK) positive, vimentin (VIM) positive, and mixed CK/VIM phenotypes. Metastases were detected in the lung (20/57, 35%), liver (7/57, 12%), and brain (1/57, less than 2%). The seven different PDOX tumor models displayed varying degrees of metastatic potential, including one TNBC PDOX tumor model that failed to generate any detectable metastases (0/8 mice) despite having CTCs present in the blood of 5/5 tested, suggesting that CTCs from this particular PDOX tumor model may typify metastatic inefficiency.

CONCLUSION

PDOX tumor models that shed CTCs and develop distant metastases represent an important tool for investigating TNBC.

Circulating Tumor Cell Clusters in Patients with Metastatic Breast Cancer: a SWOG S0500 Translational Medicine Study

PURPOSE

Metastasis requires malignant cell circulation from the primary to a distant tissue. Elevated levels of circulating tumor cells (CTC) portend a poor prognosis in breast and other cancers. Recent studies have suggested that CTC clusters may be a factor in the metastatic process. We conducted a prospective retrospective study of the SWOG0500 clinical trial to test whether CTC clusters are associated with poorer prognosis.

EXPERIMENTAL DESIGN

CTC CellSearch galleries from SWOG0500 trial were reread using prespecified criteria for CTC clusters, doublets, and enumeration. Survival analysis methods include Kaplan-Meier plots and log-rank tests.

RESULTS

Patients were classified into three prognostic subgroups based on baseline CTC/7.5 mL whole blood (WB): Arm A: <5CTC; Arm B/C: ≥5CTC and then B (<5CTC) and C (≥5CTC)/7.5 mL WB at first follow-up. At baseline, 19% of patients had CTC doublets or clusters, which were more likely in Arm B/C versus Arm A (38% vs. 1.4%; P < 0.0001). Furthermore, doublets or clusters were significantly more common in patients who were ultimately assigned to Arm C versus B (54% vs. 25%; P < 0.0001). In Arm C, doublets and clusters were associated with worse overall survival than only doublets, clusters, or no doublets nor clusters at baseline (P = 0.008) and first follow-up (P = 0.010). When compared with enumeration alone, doublets, clusters, or both were not prognostic in patients who had 5-19 or ≥20 CTC/7.5 mL WB.

CONCLUSIONS

In patients with metastatic breast cancer starting first-line chemotherapy, mortality is independent of the presence of CTC clusters, but rather depends on the number of CTC/7.5 mL WB.

Synergistic bio-recognition/spatial-confinement for effective capture and sensitive photoelectrochemical detection of MCF-7 cells

A synergistic bio-recognition/spatial-confinement strategy is proposed for the effective capture of cancer cells and sensitive photoelectrochemical detection with the lowest limit of detection of 2 cells per mL.

Advances in isolation and detection of circulating tumor cells based on microfluidics

Circulating tumor cells (CTCs) are the cancer cells that circulate in the peripheral blood after escaping from the original or metastatic tumors. CTCs could be used as non-invasive source of clinical information in early diagnosis of cancer and evaluation of cancer development. In recent years, CTC research has become a hotspot field wherein many novel CTC detection technologies based on microfluidics have been developed. Great advances have been made that exhibit obvious technical advantages, but cannot yet satisfy the current clinical requirements. In this study, we review the main advances in isolation and detection methods of CTC based on microfluidics research over several years, propose five technical indicators for evaluating these methods, and explore the application prospects. We also discuss the concepts, issues, approaches, advantages, limitations, and challenges with an aim of stimulating a broader interest in developing microfluidics-based CTC detection technology.

Near-Infrared Fluorescent Ag2S Nanodot-Based Signal Amplification for Efficient Detection of Circulating Tumor Cells

The level of circulating tumor cells (CTCs) plays a critical role in tumor metastasis and personalized therapy, but it is challenging for highly efficient capture and detection of CTCs because of the extremely low concentration in peripheral blood. Herein, we report near-infrared fluorescent Ag₂S nanodot-based signal amplification combing with immune-magnetic spheres (IMNs) for highly efficient magnetic capture and ultrasensitive fluorescence labeling of CTCs. The near-infrared fluorescent Ag₂S nanoprobe has been successfully constructed through hybridization chain reactions using aptamer-modified Ag₂S nanodots, which can extremely improve the imaging sensitivity and reduce background signal of blood samples. Moreover, the antiepithelial-cell-adhesion-molecule (EpCAM) antibody-labeled magnetic nanospheres have been used for highly capture rare tumor cells in whole blood. The near-infrared nanoprobe with signal amplification and IMNs platform exhibits excellent performance in efficient capture and detection of CTCs, which shows great potential in cancer diagnostics and therapeutics.

Perspective on Circulating Tumor Cell Clusters: Why It Takes a Village to Metastasize

Circulating tumor cell (CTC) clusters may represent one of the key mechanisms initiating the metastasis process. However, the series of pathophysiologic events by which CTC clusters originate, enter the circulation, and reach the distant sites remain to be identified. The cellular and molecular mechanisms that provide survival advantage for CTC clusters during the transit in the blood stream are also still largely unknown. Understanding the biology of CTC clusters is critical to assess this unified scheme employed by cancer and to device strategies to overcome key pathways responsible for their improved metastatic potential. CTC clusters remain an underdeveloped area of research begging the attention of multidisciplinary cancer research teams. Here, we provide insight on existing preclinical evidence on the potential mechanisms leading to CTC cluster formation and dissemination and on processes that may offer survival advantage. We also offer our perspective on future directions to delineate the role of CTC clusters in metastatic cascade and discuss their clinical significance. Cancer Res; 78(4); 845-52. ©2018 AACR.

Highly efficient isolation and release of circulating tumor cells based on size-dependent filtration and degradable ZnO nanorods substrate in a wedge-shaped microfluidic chip

Circulating tumor cells (CTCs) have been regarded as the major cause of metastasis, holding significant insights for tumor diagnosis and treatment. Although many efforts have been made to develop methods for CTC isolation and release in microfluidic system, it remains significant challenges to realize highly efficient isolation and gentle release of CTCs for further cellular and bio-molecular analyses. In this study, we demonstrate a novel method for CTC isolation and release using a simple wedge-shaped microfluidic chip embedding degradable znic oxide nanorods (ZnNRs) substrate. By integrating size-dependent filtration with degradable nanostructured substrate, the capture efficiencies over 87.5% were achieved for SKBR3, PC3, HepG2 and A549 cancer cells spiked in healthy blood sample with the flow rate of 100 μL min^-1. By dissolving ZnNRs substrate with an extremely low concentration of phosphoric acid (12.5 mM), up to 85.6% of the captured SKBR3 cells were released after reverse injection with flow rate of 100 μL min^-1 for 15 min, which exhibited around 73.6% cell viability within 1 h after release to around 93.9% after re-cultured for 3 days. It is conceivable that our microfluidic device has great potentials in carrying on cell-based biomedical studies and guiding individualized treatment in the future.