Microfluidic flow fractionation device for label-free isolation of circulating tumor cells (CTCs) from breast cancer patients

Effects of Shear and Extensional Stresses on Cells: Investigation in a Spiral Microchannel and Contraction-Expansion Arrays

In recent decades, inertial microfluidic devices have been widely used for cell separation. However, these techniques inevitably exert mechanical stresses, causing cell damage and death during the separation process. This remains a significant challenge for their biological and clinical applications. Despite extensive research on cell separation, the effects of mechanical stresses on cells in microfluidic separation have remained insufficiently explored. This review focuses on the effects of mechanical stresses on cells, particularly in spiral microchannels and contraction-expansion arrays (Contraction and Expansion Arrays (CEAs)). We derived the approximated magnitude of shear stress in a spiral microchannel, extensional stress in CEAs and conventional methods, along with exposure time in a single map to illustrate cell damage and operational zones. Finally, this review serves as a practical guideline to help readers in evaluating stress damages, enabling the effective selection of appropriate techniques that optimize cell viability and separation efficiency for biological and clinical applications.

Novel Isolating Approaches to Circulating Tumor Cell Enrichment Based on Microfluidics: A Review

Circulating tumor cells (CTCs), derived from the primary tumor and carrying genetic information, contribute significantly to the process of tumor metastasis. The analysis and detection of CTCs can be used to assess the prognosis and treatment response in patients with tumors, as well as to help study the metastatic mechanisms of tumors and the development of new drugs. Since CTCs are very rare in the blood, it is a challenging problem to enrich CTCs efficiently. In this paper, we provide a comprehensive overview of microfluidics-based enrichment devices for CTCs in recent years. We explore in detail the methods of enrichment based on the physical or biological properties of CTCs; among them, physical properties cover factors such as size, density, and dielectric properties, while biological properties are mainly related to tumor-specific markers on the surface of CTCs. In addition, we provide an in-depth description of the methods for enrichment of single CTCs and illustrate the importance of single CTCs for performing tumor analyses. Future research will focus on aspects such as improving the separation efficiency, reducing costs, and increasing the detection sensitivity and accuracy.

Multistage microfluidic cell sorting method and chip based on size and stiffness

High performance sorting of circulating tumor cells (CTCs) from peripheral blood is key to liquid biopsies. Size-based deterministic lateral displacement (DLD) technique is widely used in cell sorting. But conventional microcolumns have poor fluid regulation ability, which limits the sorting performance of DLD. When the size difference between CTCs and leukocytes is small (e.g., less than 3 μm), not only DLD, many size-based separation techniques fail due to low specificity. CTCs have been confirmed to be softer than leukocytes, which could serve as a basis for sorting. In this study, we presented a multistage microfluidic CTCs sorting method, first sorting CTCs using a size-based two-array DLD chip, then purifying CTCs mixed by leukocytes using a stiffness-based cone channel chip, and finally identifying cell types using Raman techniques. The entire CTCs sorting and analysis process was label free, highly pure, high-throughput and efficient. The two-array DLD chip employed a droplet-shaped microcolumn (DMC) developed by optimization design rather than empirical design. Attributed to the excellent fluid regulation capability of DMC, the CTCs sorter system developed by parallelizing four DMC two-array DLD chips was able to process a sample of 2.5 mL per minute with a recovery efficiency of 96.30 ± 2.10% and a purity of 98.25 ± 2.48%. To isolate CTCs mixed dimensionally by leukocytes, a cone channel sorting method and chip were developed based on solid and hydrodynamic coupled analysis. The cone channel chip allowed CTCs to pass through the channel and entrap leukocytes, improving the purity of CTCs mixed by leukocytes by 1.8-fold.

Continuous CTC separation through a DEP-based contraction-expansion inertial microfluidic channel

The efficient isolation of viable and intact circulating tumor cells (CTCs) from blood is critical for the genetic analysis of cancer cells, prediction of cancer progression, development of drugs, and evaluation of therapeutic treatments. While conventional cell separation devices utilize the size difference between CTCs and other blood cells, they fail to separate CTCs from white blood cells (WBCs) due to significant size overlap. To overcome this issue, we present a novel approach that combines curved contraction-expansion (CE) channels with dielectrophoresis (DEP) and inertial microfluidics to isolate CTCs from WBCs regardless of size overlap. This label-free and continuous separation method utilizes dielectric properties and size variation of cells for the separation of CTCs from WBCs. The results demonstrate that the proposed hybrid microfluidic channel can effectively isolate A549 CTCs from WBCs regardless of their size with a throughput of 300 μL/min, achieving a high separation distance of 233.4 μm at an applied voltage of 50 Vp-p . The proposed method allows for the modification of cell migration characteristics by controlling the number of CE sections of the channel, applied voltage, applied frequency, and flow rate. With its unique features of a single-stage separation, simple design, and tunability, the proposed method provides a promising alternative to the existing label-free cell separation techniques and may have a wide range of applications in biomedicine.

Electrochemical detection and analysis of tumor-derived extracellular vesicles to evaluate malignancy of pancreatic cystic neoplasm using integrated microfluidic device

Tumor-derived extracellular vesicles (tdEVs) are one of the most promising biomarkers for liquid biopsy-based cancer diagnostics, owing to the expression of specific membrane proteins of their cellular origin. The investigation of epithelial-to-mesenchymal transition (EMT) in cancer using tdEVs is an alternative way of evaluating the risk of malignancy transformation. An ultra-sensitive selection and detection methodology is an essential step in developing a tdEVs-based cancer diagnostic device. In this study, we developed an indium-tin-oxide (ITO) sensor integrated microfluidic device consisting of two main parts: 1) a multi-orifice flow-fractionation (MOFF) channel for extraction of pure EVs by removing blood cellular debris, and 2) an ITO sensor coupled with a geometrically activated surface interaction (GASI) channel for enrichment and quantification of tdEV. The microfluidic channel and the ITO sensors are assembled with a 3D printed magnetic housing to prevent sample leakage and to easily attach/detach the sensors to/from the microfluidic channel. The tdEVs were successfully captured on the specific antibody modified ITO surfaces in the integrated microfluidic channel. The integrated sensors showed an excellent linear response between 10³ and 10⁹ tdEVs/mL. Simultaneous evaluation of the epithelial and mesenchymal markers on the tdEV surfaces successfully revealed the EMT index of the corresponding pancreatic cancer cells. Our ITO sensor integrated microfluidic device showed excellent detection in the clinically relevant tdEVs-concentration range for patients with pancreatic cystic neoplasms. Hence, this system is expected to open a new avenue for liquid biopsy-based cancer prognostics and diagnostics.

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.

Deep learning assisted holography microscopy for in-flow enumeration of tumor cells in blood

Currently, detection of circulating tumor cells (CTCs) in cancer patient blood samples relies on immunostaining, which does not provide access to live CTCs, limiting the breadth of CTC-based applications. Here, we take the first steps to address this limitation, by demonstrating staining-free enumeration of tumor cells spiked into lysed blood samples using digital holographic microscopy (DHM), microfluidics and machine learning (ML). A 3D-printed module for laser assembly was developed to simplify the optical set up for holographic imaging of cells flowing through a sheath-based microfluidic device. Computational reconstruction of the holograms was performed to localize the cells in 3D and obtain the plane of best focus images to train deep learning models. We developed a custom-designed light-weight shallow Network dubbed s-Net and compared its performance against off-the-shelf CNN models including ResNet-50. The accuracy, sensitivity and specificity of the s-Net model was found to be higher than the off-the-shelf ML models. By applying an optimized decision threshold to mixed samples prepared in silico, the false positive rate was reduced from 1 × 10^-2 to 2.77 × 10^-4. Finally, the developed DHM-ML framework was successfully applied to enumerate spiked MCF-7 breast cancer cells and SkOV3 ovarian cancer cells from lysed blood samples containing white blood cells (WBCs) at concentrations typical of label-free enrichment techniques. We conclude by discussing the advances that need to be made to translate the DHM-ML approach to staining-free enumeration of actual CTCs in cancer patient blood samples.

Clinical Relevancy of Circulating Tumor Cells in Breast Cancer: Epithelial or Mesenchymal Characteristics, Single Cells or Clusters?

Metastatic breast cancer (MBC) is typically an incurable disease with high mortality rates; thus, early identification of metastatic features and disease recurrence through precise biomarkers is crucial. Circulating tumor cells (CTCs) consisting of heterogeneous subpopulations with different morphology and genetic, epigenetic, and gene expression profiles represent promising candidate biomarkers for metastatic potential. The experimentally verified role of epithelial-to-mesenchymal transition in cancer dissemination has not been clearly described in BC patients, but the stemness features of CTCs strongly contributes to metastatic potency. Single CTCs have been shown to be protected in the bloodstream against recognition by the immune system through impaired interactions with T lymphocytes and NK cells, while associations of heterotypic CTC clusters with platelets, leucocytes, neutrophils, tumor-associated macrophages, and fibroblasts improve their tumorigenic behavior. In addition to single CTC and CTC cluster characteristics, we reviewed CTC evaluation methods and clinical studies in early and metastatic BCs. The variable CTC tests were developed based on specific principles and strategies. However, CTC count and the presence of CTC clusters were shown to be most clinically relevant in existing clinical trials. Despite the known progress in CTC research and sampling of BC patients, implementation of CTCs and CTC clusters in routine diagnostic and treatment strategies still requires improvement in detection sensitivity and precise molecular characterizations, focused predominantly on the role of CTC clusters for their higher metastatic potency.

ALCAM: A Novel Surface Marker on EpCAMlow Circulating Tumor Cells

Background: Current strategies in circulating tumor cell (CTC) isolation in pancreatic cancer heavily rely on the EpCAM and cytokeratin cell status. EpCAM is generally not considered a good marker given its transitory change during Epithelial to Mesenchymal Transition (EMT) or reverse EMT. There is a need to identify other surface markers to capture the complete repertoire of PDAC CTCs. The primary objective of the study is to characterize alternate surface biomarkers to EpCAM on CTCs that express low or negligible levels of surface EpCAM in pancreatic cancer patients. Methods: Flow cytometry and surface mass spectrometry were used to identify proteins expressed on the surface of PDAC CTCs in culture. CTCs were grown under conditions of attachment and in co-culture with naïve neutrophils. Putative biomarkers were then validated in GEMMs and patient samples. Results: Surface proteomic profiling of CTCs identified several novel protein biomarkers. ALCAM was identified as a novel robust marker in GEMM models and in patient samples. Conclusions: We identified several novel surface biomarkers on CTCs expressed under differing conditions of culture. ALCAM was validated and identified as a novel alternate surface marker on EpCAMlow CTCs.

Detection of live breast cancer cells in bright-field microscopy images containing white blood cells by image analysis and deep learning

SIGNIFICANCE

Circulating tumor cells (CTCs) are important biomarkers for cancer management. Isolated CTCs from blood are stained to detect and enumerate CTCs. However, the staining process is laborious and moreover makes CTCs unsuitable for drug testing and molecular characterization.

AIM

The goal is to develop and test deep learning (DL) approaches to detect unstained breast cancer cells in bright-field microscopy images that contain white blood cells (WBCs).

APPROACH

We tested two convolutional neural network (CNN) approaches. The first approach allows investigation of the prominent features extracted by CNN to discriminate in vitro cancer cells from WBCs. The second approach is based on faster region-based convolutional neural network (Faster R-CNN).

RESULTS

Both approaches detected cancer cells with higher than 95% sensitivity and 99% specificity with the Faster R-CNN being more efficient and suitable for deployment presenting an improvement of 4% in sensitivity. The distinctive feature that CNN uses for discrimination is cell size, however, in the absence of size difference, the CNN was found to be capable of learning other features. The Faster R-CNN was found to be robust with respect to intensity and contrast image transformations.

CONCLUSIONS

CNN-based DL approaches could be potentially applied to detect patient-derived CTCs from images of blood samples.

Coil spring-powered pump with inertial microfluidic chip for size-based isolation and enrichment of biological cells

Coil spring-powered device for circulating biomarker isolation.

Microfluidic chip for rapid and selective isolation of tumor-derived extracellular vesicles for early diagnosis and metastatic risk evaluation of breast cancer

The epithelial-to-mesenchymal transition (EMT) index in cancer is a complementary approach for estimating metastatic risk. Considering the demand for evaluating metastatic risk based on liquid biopsies, tumor-derived extracellular vesicles (EVs) can be exploited to generate the EMT index. For the generation of EVs-based EMT index, it is essential to selectively isolate each epithelial cell and mesenchymal cell-derived EVs. This study proposes a novel microfluidic chip for selectively separating two types of EVs in an efficient and timely manner. The microfluidic chip is fully integrated with a micromixer for the creation of efficient collision between EVs and specific antibody-coated microbeads (7 and 15 μm in diameter) and a hydrodynamic particle separator for the stratification of EVs bound microbeads according to the sizes of microbeads. Using this chip, over 90% of EVs expressing the epithelial marker (epithelial cell adhesion molecule, EpCAM) and the mesenchymal marker (CD49f) can be selectively isolated within 6.7 min per 100 μL of sample volume. The clinical relevance of EMT is investigated using plasma samples from 20 breast cancer patients and 10 age-matched controls. The EMT index produced from the microfluidic chip is in a good agreement with the conventional tissue-based EMT index and is significantly high in patients with aggressive breast cancer subtypes, compared with healthy controls. In addition, the patients with high scores on the EMT index (≥5) shows recurrence within 5 years after adjuvant treatment. Predicting EMT-index-based metastatic risk using our microfluidic chip can be beneficial for cancer diagnosis and prognosis.

State-of-the-arts techniques and current evolving approaches in the separation and detection of circulating tumor cell

Circulating tumor cells (CTCs) are cancer cells that shed from the primary tumor and then enter the circulatory system, a small part of which may evolve into metastatic cancer under appropriate microenvironment conditions. The detection of CTCs is a truly noninvasive, dynamic monitor for disease changes, which has considerable clinical implications in the selection of targeted drugs. However, their inherent rarity and heterogeneity pose significant challenges to their isolation and detection. Even the "gold standard", CellSearch™, suffers from high expenses, low capture efficiency, and the consumption of time. With the advancement of CTCs analysis technologies in recent years, the yield and efficiency of CTCs enrichment have gradually been improved, as well as detection sensitivity. In this review, the isolation and detection strategies of CTCs have been completely described and the potential directions for future research and development have also been highlighted through analyzing the challenges faced by current strategies.

Microfluidic Systems for Cancer Diagnosis and Applications

Microfluidic devices have led to novel biological advances through the improvement of micro systems that can mimic and measure. Microsystems easily handle sub-microliter volumes, obviously with guidance presumably through laminated fluid flows. Microfluidic systems have production methods that do not need expert engineering, away from a centralized laboratory, and can implement basic and point of care analysis, and this has attracted attention to their widespread dissemination and adaptation to specific biological issues. The general use of microfluidic tools in clinical settings can be seen in pregnancy tests and diabetic control, but recently microfluidic platforms have become a key novel technology for cancer diagnostics. Cancer is a heterogeneous group of diseases that needs a multimodal paradigm to diagnose, manage, and treat. Using advanced technologies can enable this, providing better diagnosis and treatment for cancer patients. Microfluidic tools have evolved as a promising tool in the field of cancer such as detection of a single cancer cell, liquid biopsy, drug screening modeling angiogenesis, and metastasis detection. This review summarizes the need for the low-abundant blood and serum cancer diagnosis with microfluidic tools and the progress that has been followed to develop integrated microfluidic platforms for this application in the last few years.

Design and Fabrication of a Microfluidic Chip for Particle Size-Exclusion and Enrichment

Based on the size of particles, a microfluidic chip integrating micro particles capture, controlled release and counting analysis was designed and fabricated in this paper. The chip is composed of a polydimethylsiloxane (PDMS) cover sheet and a PDMS substrate. The PDMS substrate is made of a sample inlet, microfluidic channels, a micropillar array, a three-dimensional (3D) focusing channel, and a sample outlet. The chip was fabricated by the multistep SU-8 lithography and PDMS molding method in this study. The micropillar array and channels in the chip can be molded in one step and can be replicated multiple times, which reduces the production cost and increases the practicability of the chip. Using a homemade electromagnetic drive device, the detection function of the chip was tested using a deionized water solution containing 22 μm polyethylene particles. The results showed that under the action of electromagnetic force, the chip enriched polyethylene particles; when the electromagnetic force disappeared, the enriched polyethylene particles were released by injecting buffer solution, and it was looked at as new sample solution. The flow rate of the sample solution and the sheath flow solution (deionized water) was injected into the three-dimensional focusing channel at a flow rate ratio of 1:4, and the polyethylene particles sample solution was focused, which could be used for the counting and analysis of polyethylene particles. The work of this paper can provide a reference for the subsequent detection of circulating tumor cells (CTCs).

Inertial microfluidics in contraction-expansion microchannels: A review

Inertial microfluidics has brought enormous changes in the conventional cell/particle detection process and now become the main trend of sample pretreatment with outstanding throughput, low cost, and simple control method. However, inertial microfluidics in a straight microchannel is not enough to provide high efficiency and satisfying performance for cell/particle separation. A contraction-expansion microchannel is a widely used and multifunctional channel pattern involving inertial microfluidics, secondary flow, and the vortex in the chamber. The strengthened inertial microfluidics can help us to focus particles with a shorter channel length and less processing time. Both the vortex in the chamber and the secondary flow in the main channel can trap the target particles or separate particles based on their sizes more precisely. The contraction-expansion microchannels are also capable of combining with a curved, spiral, or serpentine channel to further improve the separation performance. Some recent studies have focused on the viscoelastic fluid that utilizes both elastic forces and inertial forces to separate different size particles precisely with a relatively low flow rate for the vulnerable cells. This article comprehensively reviews various contraction-expansion microchannels with Newtonian and viscoelastic fluids for particle focusing, separation, and microfluid mixing and provides particle manipulation performance data analysis for the contraction-expansion microchannel design.

Advances in Micro/Nanoporous Membranes for Biomedical Engineering

Porous membrane materials at the micro/nanoscale have exhibited practical and potential value for extensive biological and medical applications associated with filtration and isolation, cell separation and sorting, micro-arrangement, in-vitro tissue reconstruction, high-throughput manipulation and analysis, and real-time sensing. Herein, an overview of technological development of micro/nanoporous membranes (M/N-PMs) is provided. Various membrane types and the progress documented in membrane fabrication techniques, including the electrochemical-etching, laser-based technology, microcontact printing, electron beam lithography, imprinting, capillary force lithography, spin coating, and microfluidic molding are described. Their key features, achievements, and limitations associated with micro/nanoporous membrane (M/N-PM) preparation are discussed. The recently popularized applications of M/N-PMs in biomedical engineering involving the separation of cells and biomolecules, bioparticle operations, biomimicking, micropatterning, bioassay, and biosensing are explored too. Finally, the challenges that need to be overcome for M/N-PM fabrication and future applications are highlighted.

Reducing Ovarian Cancer Mortality Through Early Detection: Approaches Using Circulating Biomarkers

More than two-thirds of all women diagnosed with epithelial ovarian cancer (EOC) will die from the disease (>14,000 deaths annually), a fact that has not changed considerably in the last three decades. Although the 5-year survival rates for most other solid tumors have improved steadily, ovarian cancer remains an exception, making it the deadliest of all gynecologic cancers and five times deadlier than breast cancer. When diagnosed early, treatment is more effective, with a 5-year survival rate of up to 90%. Unfortunately, most cases are not detected until after the cancer has spread, resulting in a dismal 5-year survival rate of less than 30%. Current screening methods for ovarian cancer typically use a combination of a pelvic examination, transvaginal ultrasonography, and serum cancer antigen 125 (CA125), but these have made minimal impact on improving mortality. Thus, there is a compelling unmet need to develop new molecular tools that can be used to diagnose early-stage EOC and/or assist in the clinical management of the disease after a diagnosis, given that more than 220,000 women are living with ovarian cancer in the United States and are at risk of recurrence. Here, we discuss the state of advancing liquid-based approaches for improving the early detection of ovarian cancer.See all articles in this Special Collection Honoring Paul F. Engstrom, MD, Champion of Cancer Prevention.

A Review of Circulating Tumour Cell Enrichment Technologies

Simple Summary

Circulating tumour cells (CTCs) are cancer cells shed into the bloodstream from tumours and their analysis can provide important insights into cancer detection and monitoring, with the potential to direct personalised therapies for the patient. These CTCs are rare in the blood, which makes their detection and enrichment challenging and to date, only one technology (the CellSearch) has gained FDA approval for determining the prognosis of patients with advanced breast, prostate and colorectal cancers. Here, we review the wide range of enrichment technologies available to isolate CTCs from other blood components and highlight the important characteristics that new technologies should possess for routine clinical use.

Abstract

Circulating tumour cells (CTCs) are the precursor cells for the formation of metastatic disease. With a simple blood draw, liquid biopsies enable the non-invasive sampling of CTCs from the blood, which have the potential to provide important insights into cancer detection and monitoring. Since gaining FDA approval in 2004, the CellSearch system has been used to determine the prognosis of patients with metastatic breast, prostate and colorectal cancers. This utilises the cell surface marker Epithelial Cell Adhesion Molecule (EpCAM), to enrich CTCs, and many other technologies have adopted this approach. More recently, the role of mesenchymal-like CTCs in metastasis formation has come to light. It has been suggested that these cells are more aggressive metastatic precursors than their epithelial counterparts; however, mesenchymal CTCs remain undetected by EpCAM-based enrichment methods. This has prompted the development of a variety of ‘label free’ enrichment technologies, which exploit the unique physical properties of CTCs (such as size and deformability) compared to other blood components. Here, we review a wide range of both immunocapture and label free CTC enrichment technologies, summarising the most significant advantages and disadvantages of each. We also highlight the important characteristics that technologies should possess for routine clinical use, since future developments could have important clinical implications, with the potential to direct personalised therapies for patients with cancer.

Sequential Ensemble-Decision Aliquot Ranking Isolation and Fluorescence In Situ Hybridization Identification of Rare Cells from Blood by Using Concentrated Peripheral Blood Mononuclear Cells

Isolation and analysis of circulating rare cells is a promising approach for early detection of cancer and other diseases and for prenatal diagnosis. Isolation of rare cells is usually difficult due to their heterogeneity as well as their low abundance in peripheral blood. We previously reported a two-stage ensemble-decision aliquot ranking platform (S-eDAR) for isolating circulating tumor cells from whole blood with high throughput, high recovery rate (>90%), and good purity (>70%), allowing detection of low surface antigen-expressing cancer cells linked to metastasis. However, due to the scarcity of these cells, large sample volumes and large quantities of antibodies were required to isolate sufficient cells for downstream analysis. Here, we drastically increased the number of nucleated cells analyzed by first concentrating peripheral blood mononuclear cells (PBMCs) from whole blood by density gradient centrifugation. The S-eDAR platform was capable of isolating rare cells from concentrated PBMCs (10⁸/mL, equivalent to processing ∼20 mL of whole blood in the 1 mL sample volume used by our instrument) at a high recovery rate (>85%). We then applied the S-eDAR platform for isolating rare fetal nucleated red blood cells (fNRBCs) from concentrated PBMCs spiked with umbilical cord blood cells and confirmed fNRBC recovery by immunostaining and fluorescence in situ hybridization, demonstrating the potential of the S-eDAR system for isolating rare fetal cells from maternal PBMCs to improve noninvasive prenatal diagnosis.

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.

Microfluidic biosensing of circulating tumor cells (CTCs): Recent progress and challenges in efficient diagnosis of cancer

Cancer metastasis is one of the foremost causes of cancer incidence and fatality in the whole of the world. Circulating tumor cells (CTC) have been confirmed to be among the most significant stimuli of metastasis in recent years and presently are the subject of extensive research aiming to be accurately identified by using biological and physical properties. Among the various studies conducted for isolation, identification, and characterization of CTCs, microfluidic systems have aroused great attention owing to their unique advantages such as low-cost, simplicity, reduction in reagent consumption, miniaturization, fast and precise control. The purpose of this review is to provide an overview of current state of the microfluidic biosensors for the screening of CTCs. Additionally, given the recent progress in this field, future outlook for the development of the microfluidics biosensing is briefly discussed.

Inertial microfluidics: Recent advances

Inertial microfluidics has attracted significant attentions in last decade due to its superior advantages of high throughput, label- and external field-free operation, simplicity, and low cost. A wide variety of channel geometry designs were demonstrated for focusing, concentrating, isolating, or separating of various bioparticles such as blood components, circulating tumor cells, bacteria, and microalgae. In this review, we first briefly introduce the physics of inertial migration and Dean flow for allowing the readers with diverse backgrounds to have a better understanding of the fundamental mechanisms of inertial microfluidics. Then, we present a comprehensive review of the recent advances and applications of inertial microfluidic devices according to different channel geometries ranging from straight channels, curved channels to contraction-expansion-array channels. Finally, the challenges and future perspective of inertial microfluidics are discussed. Owing to its superior benefit for particle manipulation, the inertial microfluidics will play a more important role in biology and medicine applications.

Incorporation of lateral microfiltration with immunoaffinity for enhancing the capture efficiency of rare cells

The methods for isolating rare cells such as circulating tumor cells (CTCs) can be generally classified into two categories: those based on physical properties (e.g., size) and methods based on biological properties (e.g., immunoaffinity). CellSearch, the only FDA-approved method for the CTC-based cancer prognosis, relies on immunoaffinity interactions between CTCs and antibodies immobilized on magnetic particles. Immunoaffinity-based CTC isolation has also been employed in microfluidic devices, which show higher capture efficiency than CellSearch. We report here our investigation of combining size-based microfiltration into a microfluidic device with immunoaffinity for enhanced capture efficiency of CTCs. The device consists of four serpentine main channels, and each channel contains an array of lateral filters that create a two-dimensional flow. The main flow is through the serpentine channel, allowing the majority of the sample to pass by while the secondary flow goes through the lateral filters. The device design is optimized to make all fluid particles interact with filters. The filter sizes range from 24 to 12 µm, being slightly larger than or having similar dimension of CTCs. These filters are immobilized with antibodies specific to CTCs and thus they function as gates, allowing normal blood cells to pass by while forcing the interactions between CTCs and antibodies on the filter surfaces. The hydrodynamic force experienced by a CTC was also studied for optimal experimental conditions to ensure immunoaffinity-enabled cell capture. The device was evaluated by capturing two types of tumor cells spiked in healthy blood or a buffer, and we found that their capture efficiency was between 87.2 and 93.5%. The platform was further validated by isolating CTCs from blood samples of patients with metastatic pancreatic cancer.

Recent Advances in Microfluidic Platforms Applied in Cancer Metastasis: Circulating Tumor Cells' (CTCs) Isolation and Tumor-On-A-Chip

Cancer remains the leading cause of death worldwide despite the enormous efforts that are made in the development of cancer biology and anticancer therapeutic treatment. Furthermore, recent studies in oncology have focused on the complex cancer metastatic process as metastatic disease contributes to more than 90% of tumor-related death. In the metastatic process, isolation and analysis of circulating tumor cells (CTCs) play a vital role in diagnosis and prognosis of cancer patients at an early stage. To obtain relevant information on cancer metastasis and progression from CTCs, reliable approaches are required for CTC detection and isolation. Additionally, experimental platforms mimicking the tumor microenvironment in vitro give a better understanding of the metastatic microenvironment and antimetastatic drugs' screening. With the advancement of microfabrication and rapid prototyping, microfluidic techniques are now increasingly being exploited to study cancer metastasis as they allow precise control of fluids in small volume and rapid sample processing at relatively low cost and with high sensitivity. Recent advancements in microfluidic platforms utilized in various methods for CTCs' isolation and tumor models recapitulating the metastatic microenvironment (tumor-on-a-chip) are comprehensively reviewed. Future perspectives on microfluidics for cancer metastasis are proposed.

Antibody-free isolation and regulation of adherent cancer cells via hybrid branched microtube-sandwiched hydrodynamic system

The detection of circulating tumor cells (CTCs) has achieved promising progress for early diagnosis and disease analysis. Microfluidic chip techniques have recently promoted the technologies of CTC sorting and analysis, yet seldom can the microfluidic chips for CTC enrichment via antibody-free capture provide in situ regulation of both extracellular and intracellular activity, which would be advantageous for cell-based pharmaceutical therapeutics and screening. Herein, we have demonstrated a hybrid TiO2/ZnO branched microtube array (HBMTA)-sandwiched hydrodynamic device that integrates the multiple functions of selective enrichment of adherent tumor cells in an antibody-free manner and in situ delivery to the extracellular and intracellular spaces of the enriched tumor cells. More than 90% cancer cells were enriched on the device due to their preferential adhesion with the nano-branches of HBMTA, while more than 91% blood cells were eliminated from the device by constant hydrodynamic fluid shearing. For in situ regulation, temporally and spatially controlled extracellular delivery to the enriched tumor cells could be precisely achieved through the hollow structures of the HBMTA. In addition, reagents (e.g. propidium iodide) could be delivered into the intracellular spaces of enriched tumor cells by coupling an electric field to nondestructively perforate the cell membrane. Our study not only offers a promising and facile strategy for antibody-free isolation of tumor cells, but also provides unique opportunities to facilitate cancer research, including antitumor drug screening and personalized therapeutics.

Examination of the dielectrophoretic spectra of MCF7 breast cancer cells and leukocytes

The detection of circulating tumor cells (CTCs) in blood is crucial to assess metastatic progression and to guide therapy. Dielectrophoresis (DEP) is a powerful cell surface marker-free method that allows intrinsic dielectric properties of suspended cells to be exploited for CTC enrichment/isolation from blood. Design of a successful DEP-based CTC enrichment/isolation system requires that the DEP response of the targeted particles should accurately be known. This paper presents a DEP spectrum method to investigate the DEP spectra of cells without directly analyzing their membrane and cytoplasmic properties in contrast to the methods in literature, which employ theoretical assumptions and complex modeling. Integrating electric field simulations based on DEP theory with the experimental data enables determination of the DEP spectra of leukocyte subpopulations, polymorphonuclear and mononuclear leukocytes, and MCF7 breast cancer cells as a model of CTC due to their metastatic origin over the frequency range 100 kHz-50 MHz at 10 V_pp . In agreement with earlier findings, differential DEP responses were detected for mononuclear and polymorphonuclear leukocytes due to the richness of the cell surface features and morphologies of the different leukocyte types. The data reveal that the strength of the DEP force exerted on MCF7 cells was particularly high between 850 kHz and 20 MHz. These results illustrate that the proposed technique has the potential to provide a generic platform to identify DEP responses of different biological particles.

Microfluidics for label-free sorting of rare circulating tumor cells

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

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

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

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

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

Liquid biopsy in breast cancer: A comprehensive review

Breast cancer is the most common cancer among women worldwide. Due to its complexity in nature, effective breast cancer treatment can encounter many challenges. Traditional methods of cancer detection such as tissue biopsy are not comprehensive enough to capture the entire genomic landscape of breast tumors. However, with the introduction of novel techniques, the application of liquid biopsy has been enhanced, enabling the improvement of various aspects of breast cancer management including early diagnosis and screening, prediction of prognosis, early detection of relapse, serial sampling and efficient longitudinal monitoring of disease progress and response to treatment. Various components of tumor cells released into the blood circulation can be analyzed in liquid biopsy sampling, some of which include circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), cell-free RNA, tumor-educated platelets and exosomes. These components can be utilized for different purposes. As an example, ctDNA can be sequenced for genetic profiling of the tumors to enhance individualized treatment and longitudinal screening. CTC plasma count analysis or ctDNA detection after curative tumor resection surgery could facilitate early detection of minimal residual disease, aiding in the initiation of adjuvant therapy to prevent recurrence. Furthermore, CTC plasma count can be assessed to determine the stage and prognosis of breast cancer. In this review, we discuss the advantages and limitations of the various components of liquid biopsy used in breast cancer diagnosis and will expand on aspects that require further focus in future research.

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.

Combining 3D sidewall electrodes and contraction/expansion microstructures in microchip promotes isolation of cancer cells from red blood cells

Cell sorting from heterogeneous organisms and tissues composed of multi-type cells is of great importance in biological and clinical applications. As promising cell sorting methods, dielectrophoresis (DEP) and hydrodynamics are attracting much attention in recent years. In this paper, we report a novel strategy by coupling DEP unit (3D sidewall electrodes) and hydrodynamic unit (microchannels with contraction/expansion structures) together in one microfluidic chip. Depending on the relative positions of 3D sidewall electrodes and contraction/expansion structure, three microchips (full-coupling, semi-coupling and non-coupling) are developed and their cell sorting performance are compared by isolating lung cancer cells (PC-9 cells) from red blood cells (RBCs). Both finite element simulation and practical cell sorting prove that high cell sorting efficiency (recovery of PC-9 cells: 90.21%, recovery of RBCs: 94.35%) can be achieved in full-coupling microchip, mainly owing to the synergistic effects between DEP sorting and hydrodynamic sorting. i.e., the positive DEP force generated by 3D sidewall electrodes can simultaneously act as an additional shear gradient lift force and thus trigger secondary flow even at low flow velocity. Live/dead cell staining, hemolysis ratio, fluorescence images and CCK-8 assay prove that RBCs and PC-9 cells show no significance difference in cell viability before and after cell sorting. The proposed coupling platform for cell sorting brings on a new pathway to construct integrated microfluidic chips for effective cell sorting and separation.

Nucleus of Circulating Tumor Cell Determines Its Translocation Through Biomimetic Microconstrictions and Its Physical Enrichment by Microfiltration

The mechanism of cells passing through microconstrictions, such as capillaries and endothelial junctions, influences metastasis of circulating tumor cells (CTCs) in vivo, as well as size-based enrichment of CTCs in vitro. However, very few studies observe such translocation of microconstrictions in real time, and thus the inherent biophysical mechanism is poorly understood. In this study, a multiplexed microfluidic device is fabricated for real-time tracking of cell translocation under physiological pressure and recording deformation of the whole cell and nucleus, respectively. It is found that the deformability and size of the nucleus instead of the whole cell dominate cellular translocation through microconstrictions under a normal physiological pressure range. More specifically, cells with a large and stiff nucleus are prone to be blocked by relatively small constrictions. The same phenomenon is also observed in the size-based enrichment of CTCs from peripheral blood of metastatic cancer patients. These findings are different from a popular viewpoint that the size and deformability of a whole cell mainly determine cell translation through microconstrictions, and thus may elucidate interactions between CTCs and capillaries from a new perspective and guide the rational design of size-based microfilters for rare cell enrichment.

Immunomagnetic antibody plus aptamer pseudo-DNA nanocatenane followed by rolling circle amplication for highly-sensitive CTC detection

Biosensing and detecting the rare circulating tumor cells (CTCs) in complex blood samples are a great challenge but necessary for cancer metastasis prevention. Here we show a novel highly-sensitive biosensing system for detecting CTCs in whole blood. The system is composed of Her2-coated immunomagnetic beads and an anti-EpCAM aptamer assembled pseudo-DNA nanocatenane (PDN) for dual targeting and separating CTCs, in conjunction with the rolling circle amplification (RCA) and molecular beacon (MB) system for CTCs signal amplification. The Her-2-coated beads separated CTCs from blood after their elution from a magnetic column. The unique PDN, which is a tailor-designed self-assembly of three circular DNAs that are inter-locked with independent and non-interfered templates for periodic RCA process, binds EpCAM-rich CTCs. In the presence of the RCA primer, phi29 DNA polymerase and MB, the system collaboratively generated the amplified fluorescent signals for highly-sensitive detection of CTCs. Through this system, we achieved the limit of detection less than 10 CTCs/mL blood, and quantified the number of CTCs in patient blood, which is proportional to the patient cancer status. Our technique is highly-sensitive, practicable and convenient enough for clinical detection of breast CTCs.

Microparticle Inertial Focusing in an Asymmetric Curved Microchannel

Inertial Microfluidics offer a high throughput, label-free, easy to design, and cost-effective solutions, and are a promising technique based on hydrodynamic forces (passive techniques) instead of external ones, which can be employed in the lab-on-a-chip and micro-total-analysis-systems for the focusing, manipulation, and separation of microparticles in chemical and biomedical applications. The current study focuses on the focusing behavior of the microparticles in an asymmetric curvilinear microchannel with curvature angle of 280°. For this purpose, the focusing behavior of the microparticles with three different diameters, representing cells with different sizes in the microchannel, was experimentally studied at flow rates from 400 to 2700 µL/min. In this regard, the width and position of the focusing band are carefully recorded for all of the particles in all of the flow rates. Moreover, the distance between the binary combinations of the microparticles is reported for each flow rate, along with the Reynolds number corresponding to the largest distances. Furthermore, the results of this study are compared with those of the microchannel with the same curvature angle but having a symmetric geometry. The microchannel proposed in this study can be used or further modified for cell separation applications.

Circulating Tumor Cell Phenotyping via High-Throughput Acoustic Separation

The study of circulating tumor cells (CTCs) offers pathways to develop new diagnostic and prognostic biomarkers that benefit cancer treatments. In order to fully exploit and interpret the information provided by CTCs, the development of a platform is reported that integrates acoustics and microfluidics to isolate rare CTCs from peripheral blood in high throughput while preserving their structural, biological, and functional integrity. Cancer cells are first isolated from leukocytes with a throughput of 7.5 mL h-1 , achieving a recovery rate of at least 86% while maintaining the cells' ability to proliferate. High-throughput acoustic separation enables statistical analysis of isolated CTCs from prostate cancer patients to be performed to determine their size distribution and phenotypic heterogeneity for a range of biomarkers, including the visualization of CTCs with a loss of expression for the prostate specific membrane antigen. The method also enables the isolation of even rarer, but clinically important, CTC clusters.

Scaling code-multiplexed electrode networks for distributed Coulter detection in microfluidics

Microfluidic devices can discriminate particles based on their properties and map them into different locations on the device. For distributed detection of these particles, we have recently introduced a multiplexed sensing technique called Microfluidic CODES, which combines code division multiple access with Coulter sensing. Our technique relies on micromachined sensor geometries to produce distinct waveforms that can uniquely be linked to specific locations on the microfluidic device. In this work, we investigated the scaling of the code-multiplexed Coulter sensor network through theoretical and experimental analysis. As a model system, we designed and fabricated a microfluidic device integrated with a network of 10 code-multiplexed sensors, each of which was characterized and verified to produce a 31-bit orthogonal digital code. To predict the performance of the sensor network, we developed a mathematical model based on communications and coding theory, and calculated the error rate for our sensor network as a function of the network size and sample properties. We theoretically and experimentally demonstrated the effect of electrical impedance on the signal-to-noise ratio and developed an optimized device. We also introduced a computational approach that can process the sensor network data with minimal input from the user and demonstrated system-level operation by processing suspensions of cultured human cancer cells. Taken together, our results demonstrated the feasibility of deploying large-scale code-multiplexed electrode networks for distributed Coulter detection to realize integrated lab-on-a-chip devices.

Circulating Tumor Cells: Diagnostic and Therapeutic Applications

Metastasis contributes to poor prognosis in many types of cancer and is the leading cause of cancer-related deaths. Tumor cells metastasize to distant sites via the circulatory and lymphatic systems. In this review, we discuss the potential of circulating tumor cells for diagnosis and describe the experimental therapeutics that aim to target these disseminating cancer cells. We discuss the advantages and limitations of such strategies and how they may lead to the development of the next generation of antimetastasis treatments.

Emerging Technologies for Cancer Research: Towards Personalized Medicine with Microfluidic Platforms and 3D Tumor Models

In the present review, we describe three hot topics in cancer research such as circulating tumor cells, exosomes, and 3D environment models. The first section is dedicated to microfluidic platforms for detecting circulating tumor cells, including both affinity-based methods that take advantage of antibodies and aptamers, and "label-free" approaches, exploiting cancer cells physical features and, more recently, abnormal cancer metabolism. In the second section, we briefly describe the biology of exosomes and their role in cancer, as well as conventional techniques for their isolation and innovative microfluidic platforms. In the third section, the importance of tumor microenvironment is highlighted, along with techniques for modeling it in vitro. Finally, we discuss limitations of two-dimensional monolayer methods and describe advantages and disadvantages of different three-dimensional tumor systems for cell-cell interaction analysis and their potential applications in cancer management.

The Continuous Concentration of Particles and Cancer Cell Line Using Cell Margination in a Groove-Based Channel

In the capillary venules, blood cells auto-separate with red blood cells aggregating near the centre of vessel and the nucleated cells marginating toward the wall of vessel. In this experiment, we used cell margination to help enrich the Jurkat cells via a groove-based channel which provides a vertical expansion-contraction structure, wherein the red blood cells invade the grooves and push the Jurkat cells to the bottom of the channel. The secondary flows induced by the anisotropic grooves bring the Jurkat cells to the right sidewall. Rigid, 13-µm diameter polystyrene particles were spiked into the whole blood to verify the operating principle under various working conditions, and then tests were carried out using Jurkat cells (~15 µm). The performance of this device was quantified by analysing the cell distribution in a transverse direction at the outlet, and then measuring the cell concentration from the corresponding outlets. The results indicate that Jurkat cells were enriched by 22.3-fold with a recovery rate of 83.4%, thus proving that this microfluidic platform provides a gentle and passive way to isolate intact and viable Jurkat cells.

Precisely Enumerating Circulating Tumor Cells Utilizing a Multi-Functional Microfluidic Chip and Unique Image Interpretation Algorithm

Enumerating circulating tumor cells (CTCs) has been demonstrably useful in cancer treatment. Although there are several approaches that have proved effective in isolating CTC-like cells, the crucial identification of CTCs continues to rely on the manual interpretation of immunofluorescence images of all cells that have been isolated. This procedure is time consuming and more importantly, CTC identification relies on subjective criteria that may differ between examiners. In this study, we describe the design, testing, and verification of a microfluidic platform that provides accurate and automated CTC enumeration using a common objective criterion. Methods: The platform consists of a multi-functional microfluidic chip and a unique image processing algorithm. The microfluidic chip integrates blood filtering, cell isolation, and single cell positioning to ensure minimal cell loss, efficient cell isolation, and fixed arraying of single cells to facilitate downstream image processing. By taking advantage of the microfluidic chip design to reduce calculation loads and eliminate measurement errors, our specially designed algorithm has the capability of rapidly interpreting hundreds of images to provide accurate CTC counts. Results: Following intensive optimization of the microfluidic chip, the image processing algorithm, and their collaboration, we verified the complete platform by enumerating CTCs from six clinical blood samples of patients with breast cancer. Compared to tube-based CTC isolation and manual CTC identification, our platform had better accuracy and reduced the time needed from sample loading to result review by 50%. Conclusion: This automated CTC enumeration platform demonstrates not only a sound strategy in integrating a specially designed multi-functional microfluidic chip with a unique image processing algorithm for robust, accurate, and "hands-free" CTC enumeration, but may also lead to its use as a novel in vitro diagnostic device used in clinics and laboratories as readily as a routine blood test.

Microvesicles releasing by oral cancer cells enhance endothelial cell angiogenesis via Shh/RhoA signaling pathway

The present study aimed to investigate the significance of hedgehog signaling pathway in association with clinicopathology parameters and its effect on angiogenesis in oral squamous cell carcinoma (OSCC). The expression of Sonic Hh (Shh) and Gli1 were done on primary tumors and metastatic lymph nodes in OSCC samples from 80 patients by immunohistochemical analysis. The western blot was used to examine the expression of Shh in OSCC cell lines and OSCC-derived microvesicles (MVs). The role of Shh carried by MVs to induce endothelial cell angiogenesis was further investigated by matrigel assay. Our results indicated that the expression of Shh was positive associated with microvesseldentisty(MVD), TNM stage, tumor recurrence and lymph node metastasis. Moreover, Shh and Gli1 expression were higher in paired metastatic lymph nodes compared with expression of their primary tumors. The expression of Shh was abundant in Cal27, and present in SCC4, SCC9, and the amount of Shh protein in Cal27 targeting MVs was increased significantly than Cal27 cell group, up to ∼ fifth-fold. The Cal27 derived MVs increased significantly angiogenesis of HUVECs in vitro, and this effect was blocked with exoenzyme C3 transferase (C3) and shRNA targeting RhoA by suppressing RhoA expression and activation. The data suggested that OSCC derived Shh carried by MVs may facilitate the tumor growth and modulate the preparation of a vascular network in primary tumor and/or premetastatic niche.