Analogous detection of circulating tumor cells using the AccuCyte® -CyteFinder® system and ISET system in patients with locally advanced and metastatic prostate cancer

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 circulating tumor cells: opportunities and challenges

Circulating tumor cells (CTCs) are cells that shed from a primary tumor and travel through the bloodstream. Studying the functional and molecular characteristics of CTCs may provide in-depth knowledge regarding highly lethal tumor diseases. Researchers are working to design devices and develop analytical methods that can capture and detect CTCs in whole blood from cancer patients with improved sensitivity and specificity. Techniques using whole blood samples utilize physical prosperity, immunoaffinity or a combination of the above methods and positive and negative enrichment during separation. Further analysis of CTCs is helpful in cancer monitoring, efficacy evaluation and designing of targeted cancer treatment methods. Although many advances have been achieved in the detection and molecular characterization of CTCs, several challenges still exist that limit the current use of this burgeoning diagnostic approach. In this review, a brief summary of the biological characterization of CTCs is presented. We focus on the current existing CTC detection methods and the potential clinical implications and challenges of CTCs. We also put forward our own views regarding the future development direction of CTCs.

Transcriptomic profiling of single circulating tumor cells provides insight into human metastatic gastric cancer

Transcriptome analysis of circulating tumor cells (CTCs), which migrate into blood vessels from primary tumor tissues, at the single-cell level offers critical insights into the biology of metastasis and contributes to drug discovery. However, transcriptome analysis of single CTCs has only been reported for a limited number of cancer types, such as multiple myeloma, breast, hepatocellular, and prostate cancer. Herein, we report the transcriptome analysis of gastric cancer single-CTCs. We utilized an antigen-independent strategy for CTC isolation from metastatic gastric cancer patients involving a size-dependent recovery of CTCs and a single cell isolation technique. The transcriptomic profile of single-CTCs revealed that a majority of gastric CTCs had undergone epithelial-mesenchymal transition (EMT), and indicated the contribution of platelet adhesion toward EMT progression and acquisition of chemoresistance. Taken together, this study serves to employ CTC characterization to elucidate the mechanisms of chemoresistance and metastasis in gastric cancer.

Digital Pathology Slides-based Measurement of Tumor Cells and Lymphocytes Within Cytology Samples Supports the Relevance of the Separation by Size of Nonhematological Tumor and Hematological Nontumor Cells in Liquid Biopsies

Filtration by size is one method used to study circulating tumor cells in blood samples. Filtration-migration ability is highly dependent of the size of cell nucleus. This implies to search for the appropriate nucleus size able to separate between hematological nucleated and nonhematological nucleated blood cells to maximize circulating tumor cell isolation. Digitalized cytology slides [May-Grünwald Giemsa (MGG) stained and immunocytochemistry (ICC) slides] from various cancer metastases served for manual measurements of nuclei about tumor cells and adjacent lymphocytes to determine the diameters the more able to separate between tumor cells and lymphocytes. Among 2022 cells analyzed (1067 tumor cells and 955 lymphocytes) on MGG stained slides, the mean diameter of tumor cells nuclei was 14.77 µm whereas the mean diameter of lymphocytic nuclei was 6.47 µm (P<0.001). In ICC slides, about 6583 cells (4753 tumor cells and 1830 lymphocytes), the mean diameter of tumor cells nuclei was 9.28 µm whereas the mean diameter of lymphocytic nuclei was 4.95 µm (P<0.001). Areas under the receiver operating characteristic curves analyses concluded that diameters of 9.37 µm and 6 µm separated the best between tumor cells and lymphocytes in MGG and ICC slides, respectively. Measuring manually the diameters of the smallest tumor cells in ICC slides, we established more than 99% of tumor cells had diameters superior to 8 µm. The sizes differences between tumor cells and lymphocytes support the relevance of the filtration by size to isolate blood circulating nonhematological tumor cells. The existence of small tumor cells with sizes overlapping with those of lymphocytes is worth to optimize the threshold to separate between tumor cells and hematological cells.

Simple-to-Operate Approach for Single Cell Analysis Using a Hydrophobic Surface and Nanosized Droplets

Microfluidics-based technologies for single-cell analysis are becoming increasingly important tools in biological studies. With the increasing sophistication of microfluidics, cellular barcoding techniques, and next-generation sequencing, a more detailed picture of cellular subtype is emerging. Unfortunately, the majority of the methods developed for single-cell analysis are high-throughput and not suitable for rare cell analysis as they require a high input cell number. Here, we report a low-cost and reproducible method for rare single-cell analysis using a highly hydrophobic surface and nanosized static droplets. Our method allows rapid and efficient on-chip single-cell lysis and subsequent collection of genetic materials in nanoliter droplets using a micromanipulator or a laboratory pipette before subsequent genetic analysis. We show precise isolation of single cancer cells with high purity using two different strategies (i- cytospin and ii- static droplet array) for subsequent RNA analysis using droplet digital polymerase chain reaction (PCR) and real-time PCR. Our highly controlled isolation method opens a new avenue for the study of subcellular functional mechanisms, enabling the identification of rare cells of potential functional or pathogenic consequence.

Quantitative and Qualitative Analysis of Blood-based Liquid Biopsies to Inform Clinical Decision-making in Prostate Cancer

CONTEXT

Genomic stratification can impact prostate cancer (PC) care through diagnostic, prognostic, and predictive biomarkers that aid in clinical decision-making. The temporal and spatial genomic heterogeneity of PC together with the challenges of acquiring metastatic tissue biopsies hinder implementation of tissue-based molecular profiling in routine clinical practice. Blood-based liquid biopsies are an attractive, minimally invasive alternative.

OBJECTIVE

To review the clinical value of blood-based liquid biopsy assays in PC and identify potential applications to accelerate the development of precision medicine.

EVIDENCE ACQUISITION

A systematic review of PubMed/MEDLINE was performed to identify relevant literature on blood-based circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), and extracellular vesicles (EVs) in PC.

EVIDENCE SYNTHESIS

Liquid biopsy has emerged as a practical tool to profile tumor dynamics over time, elucidating features that evolve (genome, epigenome, transcriptome, and proteome) with tumor progression. Liquid biopsy tests encompass analysis of DNA, RNA, and proteins that can be detected in CTCs, ctDNA, or EVs. Blood-based liquid biopsies have demonstrated promise in the context of localized tumors (diagnostic signatures, risk stratification, and disease monitoring) and advanced disease (response/resistance biomarkers and prognostic markers).

CONCLUSIONS

Liquid biopsies have value as a source of prognostic, predictive, and response biomarkers in PC. Most clinical applications have been developed in the advanced metastatic setting, where CTC and ctDNA yields are significantly higher. However, standardization of assays and analytical/clinical validation is necessary prior to clinical implementation.

PATIENT SUMMARY

Traces of tumors can be isolated from blood samples from patients with prostate cancer either as whole cells or as DNA fragments. These traces provide information on tumor features. These minimally invasive tests can guide diagnosis and treatment selection.

Analysis of the Circulating Tumor Cell Capture Ability of a Slit Filter-Based Method in Comparison to a Selection-Free Method in Multiple Cancer Types

Circulating tumor cells (CTCs) are a promising biomarker for cancer liquid biopsy. To evaluate the CTC capture bias and detection capability of the slit filter-based CTC isolation platform (CTC-FIND), we prospectively compared it head to head to a selection-free platform (AccuCyte^®-CyteFinder^® system). We used the two methods to determine the CTC counts, CTC positive rates, CTC size distributions, and CTC phenotypes in 36 patients with metastatic cancer. Between the two methods, the median CTC counts were not significantly different and the total counts were correlated (r = 0.63, p < 0.0001). The CTC positive rate by CTC-FIND was significantly higher than that by AccuCyte^®-CyteFinder^® system (91.7% vs. 66.7%, p < 0.05). The median diameter of CTCs collected by CTC-FIND was significantly larger (13.0 μm, range 5.2–52.0 vs. 10.4 μm, range 5.2–44.2, p < 0.0001). The distributions of CTC phenotypes (CK+EpCAM+, CK+EpCAM− or CK−EpCAM+) detected by both methods were similar. These results suggested that CTC-FIND can detect more CTC-positive cases but with a bias toward large size of CTCs.

Performance evaluation of a high-throughput separation system for circulating tumor cells based on microcavity array

Circulating tumor cells (CTCs) are widely known as useful biomarkers in the liquid biopsies of cancer patients. Although single-cell genetic analysis of CTCs is a promising diagnostic tool that can provide detailed clinical information for precision medicine, the capacity of single-CTC isolation for genetic analysis requires improvement. To overcome this problem, we previously developed a multiple single-cell encapsulation system for CTCs using hydrogel-encapsulation, which allowed for the high-throughput isolation of single CTCs. However, isolation of a single cell from adjacent cells remained difficult and often resulted in contamination by neighboring cells due to the limited resolution of the generated hydrogel. We developed a novel multiple single-cell encapsulation system equipped with a high magnification lens for high throughput and a more accurate single-cell encapsulation. The multiple single-cell encapsulation system has sufficient sensitivity to detect immune-stained CTCs, and could also generate a micro-scaled hydrogel that can isolate a single cell from adjacent cells within 10 µm, with high efficiency. The proposed system enables high throughput and accurate single-cell manipulation and genome amplification without contamination from neighboring cells.

The combination of size-based separation and selection-free technology provides higher circulating tumour cells detection sensitivity than either method alone in patients with metastatic prostate cancer

OBJECTIVE

To investigate the circulating tumour cells (CTCs) capture abilities of two technologies that are not dependent on cell-surface marker expression: a selection-free platform [AccuCyte^® -CyteFinder^® system (Rarecyte)] and a size-based platform [fluid-assisted separation technology (FAST)]. In addition, the combination of the two systems to more completely assess CTCs was investigated.

PATIENTS AND METHODS

In all, 28 patients with metastatic prostate cancer were included. Two 6 mL peripheral blood samples were taken from each patient at the same time-point. The samples were then subjected to the two different technology platforms in parallel. An additional group of samples was acquired by applying the waste chamber material from the FAST-group tests (flow-through that goes through the FAST filter membrane) to the Rarecyte system for the detection any CTCs that were not captured by FAST.

RESULTS

The three groups had significantly different putative CTC-positive tests, with positive rates of 29% for Rarecyte, 57% for FAST, and 79% for the combination. We also assessed CTC phenotype: 56.6% of the CTCs were cytokeratin (CK)+/epithelial cell adhesion molecule (EpCAM)-, 3.1% were CK-/EpCAM+, and 40.3% were CK+/EPCAM+. The captured CTCs diameter ranged from 5.2 to 16.9 µm. The mean CTC size from the FAST waste chamber was significantly smaller. The diameters for each of the phenotypic groups were significantly different.

CONCLUSIONS

These data highlight disparities in the positive rates and enumerated CTC numbers detected by the two techniques. Notably, the combination of the two technologies resulted in the highest CTC-capture rates. Smaller CTCs were more likely to be missed by the FAST as they passed through the filter system. Sizes of CTCs varied with different cell surface marker phenotypes.

Detection of AXL expression in circulating tumor cells of lung cancer patients using an automated microcavity array system

Noninvasive diagnostics using circulating tumor cells (CTCs) are expected to be useful for decision making in precision cancer therapy. AXL, a receptor tyrosine kinase is associated with tumor progression, epithelial‐to‐mesenchymal transition (EMT), and drug resistance, and is a potential therapeutic target. However, the epithelial markers generally used for CTC detection may be not enough to detect AXL‐expressing CTCs due to EMT. Here, we evaluated the detection of AXL‐expressing CTCs using the mesenchymal marker vimentin with a microcavity array system. To evaluate the recovery of cancer cells, spike‐in experiments were performed using cell lines with varying cytokeratin (CK) or vimentin (VM) expression levels. With high CK and low VM‐expressing cell lines, PC‐9 and HCC827, the recovery rate of AXL‐expressing cancer cells was 1%‐17% using either CK or VM as markers. Whereas, with low CK and high VM‐expressing cell lines, MDA‐MB231 and H1299, it was 52%‐75% using CK and 72%‐88% using VM as a marker. For clinical evaluation, peripheral blood was collected from 20 non–small cell lung cancer patients and CTCs were detected using CK or VM as markers in parallel. Significantly more AXL‐expressing single CTCs were detected in VM‐positive than CK‐positive CTCs (P < .001). Furthermore, CTC clusters were identified only among VM‐positive CTCs in 20% of patients. Patients with one or more prior treatments harbored significantly more VM‐positive AXL‐expressing CTCs, suggesting the involvement of these CTCs in drug resistance. These results indicate the necessity of integrating mesenchymal markers with CTC detection and this should be further evaluated clinically.

Advanced liquid biopsy technologies for circulating biomarker detection

Liquid biopsy is a new diagnostic concept that provides important information for monitoring and identifying tumor genomes in body fluid samples. Detection of tumor origin biomolecules like circulating tumor cells (CTCs), circulating tumor specific nucleic acids (circulating tumor DNA (ctDNA), circulating tumor RNA (ctRNA), microRNAs (miRNAs), long non-coding RNAs (lnRNAs)), exosomes, autoantibodies in blood, saliva, stool, urine, etc. enables cancer screening, early stage diagnosis and evaluation of therapy response through minimally invasive means. From reliance on painful and hazardous tissue biopsies or imaging depending on sophisticated equipment, cancer management schemes are witnessing a rapid evolution towards minimally invasive yet highly sensitive liquid biopsy-based tools. Clinical application of liquid biopsy is already paving the way for precision theranostics and personalized medicine. This is achieved especially by enabling repeated sampling, which in turn provides a more comprehensive molecular profile of tumors. On the other hand, integration with novel miniaturized platforms, engineered nanomaterials, as well as electrochemical detection has led to the development of low-cost and simple platforms suited for point-of-care applications. Herein, we provide a comprehensive overview of the biogenesis, significance and potential role of four widely known biomarkers (CTCs, ctDNA, miRNA and exosomes) in cancer diagnostics and therapeutics. Furthermore, we provide a detailed discussion of the inherent biological and technical challenges associated with currently available methods and the possible pathways to overcome these challenges. The recent advances in the application of a wide range of nanomaterials in detecting these biomarkers are also highlighted.

Current status of liquid biopsies for the detection and management of prostate cancer

In recent years, new therapeutic options have become available for prostate cancer (PC) patients, generating an urgent need for better biomarkers to guide the choice of therapy and monitor treatment response. Liquid biopsies, including circulating tumor cells (CTCs), circulating nucleic acids, and exosomes, have been developed as minimally invasive assays allowing oncologists to monitor PC patients with real-time cellular or molecular information. While CTC counts remain the most extensively validated prognostic biomarker to monitor treatment response, recent advances demonstrate that CTC morphology and androgen receptor characterization can provide additional information to guide the choice of treatment. Characterization of cell-free DNA (cfDNA) is another rapidly emerging field with novel technologies capable of monitoring the evolution of treatment relevant alterations such as those in DNA damage repair genes for poly (ADP-ribose) polymerase (PARP) inhibition. In addition, several new liquid biopsy fields are emerging, including the characterization of heterogeneity, CTC RNA sequencing, the culture and xenografting of CTCs, and the characterization of extracellular vesicles (EVs) and circulating microRNAs. This review describes the clinical utilization of liquid biopsies in the management of PC patients and emerging liquid biopsy technologies with the potential to advance personalized cancer therapy.

The current role of circulating biomarkers in non-muscle invasive bladder cancer

Non-muscle invasive bladder cancer (NMIBC) is characterized by its high rate of disease recurrence and relevant disease progression rates. Up to today clinical models are insufficiently predicting outcomes for reliable patient counseling and treatment decision-making. This particularly is a serious problem in patients with high-risk NMIBC who are at high risk for failure of local treatment and thus candidates for early radical cystectomy or even systemic (neoadjuvant) chemotherapy. Next to its clinical variability, bladder cancer is genetically a highly heterogeneous disease. There is an essential need of biomarkers for improving clinical staging, real-time monitoring of disease with or without active treatment, as well as improved outcome prognostication. Liquid biopsies of circulating biomarkers in the blood and urine are promising non-invasive diagnostics that hold the potential facilitating these needs. In this review we report the latest data and evidence on cell-free circulating tumor desoxyribonucleic acid (ctDNA) and circulating tumor cells (CTC) in NMIBC. We summarize their current status in clinical diagnostics, discuss limitations and address future needs.