Study Of Circulating Tumor Cells Research Articles

Circulating tumor cell detection may offer earlier diagnosis in patients suspected of asbestos-related lung cancer

Asbestos-Related Lung Cancer (ARLC) presents ongoing diagnostic challenges despite improved imaging technologies. The long latency period, coupled with limited access to occupational and environmental data along with the confounding effects of smoking and other carcinogens adds complexity to the diagnostic process. Compounding these challenges is the absence of a specific histopathologic or mutational signature of ARLC. A correlation between PD-L1 expression and response to immune checkpoint inhibition has not yet been proven. Thus, new biomarkers are needed to allow accurate diagnoses of ARLC, to enable prognostication and to offer personalized treatments. Liquid biopsies, encompassing circulating DNA and circulating tumor cells (CTCs), have gained attention as novel diagnostic methods in lung cancer to screen high-risk populations including those exposed to asbestos. CTCs can be enumerated and molecularly profiled to provide predictive and prognostic information. CTC studies have not been undertaken in populations at risk of ARLC to date. The potential of CTCs to provide real-time molecular insight into ARLC biology may significantly improve the diagnosis and management of ARLC patients.

Surfaceome: a new era in the discovery of immune evasion mechanisms of circulating tumor cells.

Circulating tumor cells (CTCs) are cancer cells that detach from the original site and reach the bloodstream. The most aggressive CTCs survive various immune system attacks and initiate metastasis formation. Importantly, CTCs are not specifically targeted by the current immunotherapies due to the limited knowledge on specific targets. Proteomic profiling can be a powerful tool for understanding some of the immune evasion mechanisms used by cancer cells and particularly CTCs. These mechanisms are generally linked to the expression of specific surface proteins/peptides (i.e. the surfaceome). The study of the peptides that bind to class I molecules of the major histocompatibility complex (MHC-I) and of the various glycoproteins expressed on CTC surface may open a completely new avenue for the discovery of novel mechanisms of immune evasion. In this review, we discuss how immunopeptidomic and glycoproteomic studies of CTCs that interact with immune cells could help to better understand how metastasis-initiator CTCs escape the host immune response. We also describe how immunopeptidomic and glycoproteomic studies are carried out.

Abstract 7501: Gene expression profiling of rare cells captured from liquid biopsy using the genesis cell isolation system

Abstract Background: Targeting rare cell types such as circulating tumor cells (CTCs), considered to be metastatic precursors in cancer progression, may provide long-term clinical benefits by enhancing patient outcomes. The study of CTCs comes with technical challenges due to their heterogeneity and low cell numbers, leading to difficulties in genomic characterization. This study aims to overcome these technical challenges by developing a comprehensive gene expression profiling workflow using qPCR and RNA sequencing (RNA-Seq) on rare cells enriched with Genesis System with Celselect SlidesTM. Methods: To mimic CTCs in blood, we created a rare cell model sample by spiking A549 non-small cell lung cancer cells at concentrations of 50, 100, 500 and 1000 cells/ml in whole blood from healthy donors. The Genesis System, which can capture rare cells of 8µm-30µm, isolated 83.73% of spiked A549 cells in whole blood. Using the same blood samples without A549 spiked in, we enriched cells using the Genesis and it was used as a baseline for gene expression controls. High quality RNA was extracted from each of the enriched samples and used for both qPCR and RNA-Seq to detect the gene expression signature of the non-small cell lung cancer cells. Results: Our analyses revealed significant differential expression of cancer-related genes (p < 0.05) in all A549-spiked samples when compared to the blood-only controls. Notably, in the 50 cells/ml dilution, RNA-Seq analysis identified over 3,000 differentially expressed genes, encompassing protein-coding genes, long non-coding RNAs, and small non-coding RNAs. Among these, 759 genes were consistently present across all enriched samples, suggesting a common expression pattern. To investigate the potential utility of these genes as non-small cell lung cancer biomarkers, we constructed a custom qPCR array comprising 38 of these genes and pre-amplified their targets using 50pg of RNA from the enriched cell samples. Notably, six genes from this panel (MET, TOP2A, NF1, SPP1, GAPDH, and ANXA5) exhibited significant differential expression (+/- 4-fold, p<0.05) in the enriched samples. MET and TOP2A, in particular, are well-known biomarkers for non-small cell lung cancer. Conclusion: Our liquid biopsy workflow demonstrates the recovery of high-quality RNA from enriched rare cells, including CTCs. It enables comprehensive profiling of the tumor transcriptome, encompassing RNAs of various sizes, including miRNAs. Our approach has the potential to facilitate the identification of patient-specific biomarkers, enabling swift monitoring using preamplification and qPCR in advancement of targeted oncology therapy and research. Citation Format: Srikanth Perike, Angelica Olcott, Cissy Jiang, Nish Kumar, Nathan Knapp, Jennifer Placek, Candice Cox, Yoon-Tae Kang, Linda Lingelbach, Elizabeth Dreskin. Gene expression profiling of rare cells captured from liquid biopsy using the genesis cell isolation system [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7501.

Circulating tumor cell-derived preclinical models: current status and future perspectives.

Despite the advancements made in the diagnosis and treatment of cancer, the stages associated with metastasis remain largely incurable and represent the primary cause of cancer-related deaths. The dissemination of cancer is facilitated by circulating tumor cells (CTCs), which originate from the primary tumor or metastatic sites and enter the bloodstream, subsequently spreading to distant parts of the body. CTCs have garnered significant attention in research due to their accessibility in peripheral blood, despite their low abundance. They are being extensively studied to gain a deeper understanding of the mechanisms underlying cancer dissemination and to identify effective therapeutic strategies for advanced stages of the disease. Therefore, substantial efforts have been directed towards establishing and characterizing relevant experimental models derived from CTCs, aiming to provide relevant tools for research. In this review, we provide an overview of recent progress in the establishment of preclinical CTC-derived models, such as CTC-derived xenografts (CDX) and cell cultures, which show promise for the study of CTCs. We discuss the advantages and limitations of these models and conclude by summarizing the potential future use of CTCs and CTC-derived models in cancer treatment decisions and their utility as precision medicine tools.

Abstract 6605: Automated isolation and identification of circulating rare cells from blood samples using a label-free rare cell isolation platform - the Genesis System with Celselect Slide technology

Abstract Introduction: Isolation and identification of circulating tumor cells (CTCs) offers a promising non-invasive diagnostic tool for cancer research, but significant technical hurdles have made practical application challenging. Recent studies have shown that CTCs undergo cellular changes, such as an epithelial-mesenchymal transition (EMT), with disease progression and metastasis, implying the heterogeneity of the tumor cell population in circulation. Systems for CTC isolation are often limited by a requirement for epithelial markers or separate systems for identification of CTCs. As such, an automated platform that successfully isolates both epithelial and mesenchymal cells and enables identification of cells is necessary for successful study of CTCs. The Genesis System from Bio-Rad™ Laboratories, Inc. isolates rare CTCs based on size and deformability. It also enables users to identify isolated cells through use of an on-slide immunofluorescence (IF) staining workflow, which minimizes sample manipulation and potential sample loss. Methods: In order to achieve high-throughput label-free CTC isolation, the Genesis System uses Celselect Slides™. Each slide contains 56,400 individual microchambers to capture CTCs while maintaining viability. This Celselect Slide technology can be used for either enrichment or enumeration protocols. For this study, enumeration protocols were performed to capture and identify CTCs using on-slide IF staining. Enrichment protocols were utilized to capture, enrich, and retrieve CTCs for downstream applications. The performance was evaluated using a breast cancer cell line, MCF-7, spiked into whole blood from healthy donors. Results: The slide isolated 83.95 ± 10.25% of spiked cancer cells in blood samples at a concentration of 10-250 cells/ml. During the CTC enrichment procedure, 99.92% of blood cells were eliminated. Afterwards, 70% of the isolated CTCs were successfully released from the slide and over 92% of the released cells remained viable. Discussion and Conclusion: We present a fully automated platform to isolate and identify CTCs using on-slide immunofluorescence staining, which minimizes inevitable cell loss during the workflow. Captured cells can be retrieved for downstream applications to facilitate discovery of unknown CTC functions and their clinical relevance in cancer research. The wide range of possible downstream applications include Droplet Digital™ PCR, quantitative PCR, western blot assays, bulk/single-cell genomics, cell culture, fluorescence in situ hybridization, and RNA-Seq. Additionally, the design of the system is amenable to other biofluids which may be utilized for liquid biopsies. The Genesis System with Celselect Slide technology offers a powerful diagnostic tool to monitor disease progression and personalized treatment. Citation Format: Yoon-Tae Kang, Errile Pusod, Ally Crudgington, Abiodun Bodunrin, Nick Bosio, Susana Chan, David Coe, Michelle Racey. Automated isolation and identification of circulating rare cells from blood samples using a label-free rare cell isolation platform - the Genesis System with Celselect Slide technology. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6605.

Recent progress of nanostructure-based enrichment of circulating tumor cells and downstream analysis.

The isolation and detection of circulating tumor cells (CTCs) play an important role in early cancer diagnosis and prognosis, providing easy access to identify metastatic cells before clinically detectable metastases. In the past 20 years, according to the heterogeneous expression of CTCs on the surface and their special physical properties (size, morphology, electricity, etc.), a series of in vitro enrichment methods of CTCs have been developed based on microfluidic chip technology, nanomaterials and various nanostructures. In recent years, the in vivo detection of CTCs has attracted considerable attention. Photoacoustic flow cytometry and fluorescence flow cytometry were used to detect CTCs in a noninvasive manner. In addition, flexible magnetic wire and indwelling intravascular non-circulating CTCs isolation system were developed for in vivo CTCs study. In the aspect of downstream analysis, gene analysis and drug sensitivity tests of enriched CTCs were developed based on various existing molecular analysis techniques. All of these studies constitute a complete study of CTCs. Although the existing reviews mainly focus on one aspect of capturing CTCs study, a review that includes the in vivo and in vitro capture and downstream analysis study of CTCs is highly needed. This review focuses on not only the classic work and latest research progress in in vitro capture but also includes the in vivo capture and downstream analysis, discussing the advantages and significance of the different research methods and providing new ideas for solving the heterogeneity and rarity of CTCs.

Circulating Tumor Cells and Breast Cancer Metastasis: From Enumeration to Somatic Mutational Profile.

Aims: This study investigates the association between circulating tumor cells (CTCs) and breast cancer metastasis. Methods: A retrospective study was conducted using patients with histologically confirmed breast cancer recruited from the First Affiliated Hospital of Nanjing Medical University during the period of August 2017–October 2020. We used adjusted logistic regression, the random forest algorithm, and sensitivity analysis to study the association between CTC enumeration and tumor metastasis. Further, we performed next-generation sequencing (NGS) on the CTCs obtained from two patients with breast cancer brain metastasis. Results: A total of 41 out of 116 enrolled patients were identified with tumor metastasis. CTC enumeration was significantly higher in patients with liver metastasis than in those without liver metastasis. Patients with CTCs ≥ 5 exhibited a higher risk of tumor metastasis than those with CTCs < 5 in the adjusted model (odds ratios (OR) = 6.25, 95% confidence interval (CI) = 2.63–15.58). The random forest model identified CTC enumeration as a significant metastasis-related variable with the highest mean decrease accuracy and mean decrease Gini score. No significant association was found between CTCs and visceral metastasis with an OR of 1.29 (95% CI = 0.98–2.05, p = 0.232). Upon further investigating organ-specific metastasis, we found that patients with high CTC levels were more likely to develop liver metastasis (OR = 4.87, 95% CI = 1.34–20.17, p = 0.021). The NGS study of CTCs identified a total of 120 indel mutations (e.g., CNGB1, NTSR1, ZG16). The enriched biological processes were mechanoreceptor differentiation and macrophage activation involved in the immune response. The enriched KEGG pathways included focal adhesion, the PI3K-Akt signaling pathway, and microRNAs involved in cancer. Conclusions: Our study revealed that CTCs ≥ 5 are a risk factor for tumor metastasis in breast cancer patients. In addition, we reported that CTCs ≥ 5 might be associated with a higher risk of liver metastasis in patients with metastatic breast cancer. We have provided the mutational profiles of CTCs based on next-generation sequencing.

Single-Circulating Tumor Cell Whole Genome Amplification to Unravel Cancer Heterogeneity and Actionable Biomarkers.

The field of single-cell analysis has advanced rapidly in the last decade and is providing new insights into the characterization of intercellular genetic heterogeneity and complexity, especially in human cancer. In this regard, analyzing single circulating tumor cells (CTCs) is becoming particularly attractive due to the easy access to CTCs from simple blood samples called “liquid biopsies”. Analysis of multiple single CTCs has the potential to allow the identification and characterization of cancer heterogeneity to guide best therapy and predict therapeutic response. However, single-CTC analysis is restricted by the low amounts of DNA in a single cell genome. Whole genome amplification (WGA) techniques have emerged as a key step, enabling single-cell downstream molecular analysis. Here, we provide an overview of recent advances in WGA and their applications in the genetic analysis of single CTCs, along with prospective views towards clinical applications. First, we focus on the technical challenges of isolating and recovering single CTCs and then explore different WGA methodologies and recent developments which have been utilized to amplify single cell genomes for further downstream analysis. Lastly, we list a portfolio of CTC studies which employ WGA and single-cell analysis for genetic heterogeneity and biomarker detection.

Single-Cell Phenotypic and Molecular Characterization of Circulating Tumor Cells Isolated from Cryopreserved Peripheral Blood Mononuclear Cells of Patients with Lung Cancer and Sarcoma.

The isolation of circulating tumor cells (CTCs) requires rapid processing of the collected blood due to their inherent fragility. The ability to recover CTCs from peripheral blood mononuclear cells (PBMCs) preserved from cancer patients could allow for retrospective analyses or multicenter CTC studies. We compared the efficacy of CTC recovery and characterization using cryopreserved PMBCs vs fresh whole blood from patients with non-small cell lung cancer (NSCLC; n = 8) and sarcoma (n = 6). Two epithelial cellular adhesion molecule (EpCAM)-independent strategies for CTC enrichment, based on Parsortix® technology or immunomagnetic depletion of blood cells (AutoMACS®) were tested, followed by DEPArray™ single-cell isolation. Phenotype and genotype, assessed by copy number alterations analysis, were evaluated at a single-cell level. Detection of target mutations in CTC-enriched samples from frozen NSCLC PBMCs was also evaluated by digital PCR (dPCR). The use of cryopreserved PBMCs from cancer patients allowed for the retrospective enumeration of CTCs and their molecular characterization, using both EpCAM-independent strategies that performed equally in capturing CTC. Cells isolated from frozen PBMCs were representative of whole blood-derived CTCs in terms of number, phenotype, and copy number aberration profile/target mutations. Long-term storage (≥3 years) did not affect the efficacy of CTC recovery. Detection of target mutations was also feasible by dPCR in CTC-enriched samples derived from stored PBMCs. Isolating CTCs from longitudinally collected PBMCs using an unbiased selection strategy can offer a wider range of retrospective genomic/phenotypic analyses to guide patients' personalized therapy, paving the way for sample sharing in multicenter studies.

Nanomaterial-Based Immunocapture Platforms for the Recognition, Isolation, and Detection of Circulating Tumor Cells.

Circulating tumor cells (CTCs) are a type of cancer cells that circulate in the peripheral blood after breaking away from solid tumors and are essential for the establishment of distant metastasis. Up to 90% of cancer-related deaths are caused by metastatic cancer. As a new type of liquid biopsy, detecting and analyzing CTCs will provide insightful information for cancer diagnosis, especially the in-time disease status, which would avoid some flaws and limitations of invasive tissue biopsy. However, due to the extremely low levels of CTCs among a large number of hematologic cells, choosing immunocapture platforms for CTC detection and isolation will achieve good performance with high purity, selectivity, and viability. These properties are directly associated with precise downstream analysis of CTC profiling. Recently, inspired by the nanoscale interactions of cells in the tissue microenvironment, platforms based on nanomaterials have been widely explored to efficiently enrich and sensitively detect CTCs. In this review, various immunocapture platforms based on different nanomaterials for efficient isolation and sensitive detection of CTCs are outlined and discussed. First, the design principles of immunoaffinity nanomaterials are introduced in detail. Second, the immunocapture and release of platforms based on nanomaterials ranging from nanoparticles, nanostructured substrates, and immunoaffinity microfluidic chips are summarized. Third, recent advances in single-cell release and analysis of CTCs are introduced. Finally, some perspectives and challenges are provided in future trends of CTC studies.

Numerical study of dielectrophoresis-modified inertial migration for overlapping sized cell separation.

Circulating tumor cells (CTCs) have been proven to have significant prognostic, diagnostic, and clinical values in early-stage cancer detection and treatment. The efficient separation of CTCs from peripheral blood can ensure intact and viable CTCs and can, thus, give proper genetic characterization and drug innovation. In this study, continuous and high-throughput separation of MDA-231 CTCs from overlapping sized white blood cells (WBCs) is achieved by modifying inertial cell focusing with dielectrophoresis (DEP) in a single-stage microfluidic platform by numeric simulation. The DEP is enabled by embedding interdigitated electrodes with alternating field control on a serpentine microchannel to avoid creating two-stage separation. Rather than using the electrokinetic migration of cells which slows down the throughput, the system leverages the inertial microfluidic flow to achieve high-speed continuous separation. The cell migration and cell positioning characteristics are quantified through coupled physics analyses to evaluate the effects of the applied voltages and Reynolds numbers (Re) on the separation performance. The results indicate that the introduction of DEP successfully migrates WBCs away from CTCs and that separation of MDA-231 CTCs from similar sized WBCs at a high Re of 100 can be achieved with a low voltage of magnitude 4 ×106 V/m. Additionally, the viability of MDA-231 CTCs is expected to be sustained after separation due to the short-term DEP exposure. The developed technique could be exploited to design active microchips for high-throughput separation of mixed cell beads despite their significant size overlap, using DEP-modified inertial focusing controlled simply by adjusting the applied external field.

VALUATING CLINICAL APPLICATIONS OF LIQUID BIOPSY BY COMBINING CIRCULATING TUMOR DNA AND TUMOR CELLS

"Liquid biopsy" concentrates on the identification of ‘Circulating Tumor Cells (CTC) as well as ‘Cell-free Tumor DNA’ (ctDNA) in the systemic circulation of individuals suffering from cancer, has received a lot of interest due to its evident clinical implications for individualized therapy. CTC and ctDNA studies have created fresh diagnostic approaches and are now the foundations of liquid biopsy. The existing study concentrates on cancer diagnoses, prognosis prediction in people having treatable diseases, observing systemic therapy, and patient categorization depending on the identification of aimed therapeutics or resistance mechanisms. Although the use of CTCs and ctDNA for initial cancer diagnosis is gaining popularity, existing techniques experience major challenges in terms of particularity and sensitivity. Prognosis projection in people with the treatable disease so far realized in some cancer entities, especially in breast cancer. Sequential assessments of CTCs or ctDNA can also be used to monitor the progress or non-success of systemic medicines (such as hormone and chemotherapy as well as various targeted therapies).To integrate liquid diagnostic tests into personalized medicine, interventional studies on therapy stratification based on CTC and ctDNA analyses are required. KEYWORDS: Tumor cells, DNA, Circulating cells, Chemotherapy, Liquid biopsy

Evaluation of the Safety and Feasibility of Apheresis in Dogs: For Application in Metastatic Cancer Research.

Simple SummaryIn cases of cancer metastasis, some tumor cells circulate in blood (CTCs) and function as a seed for metastasis. These cells are important for detailed study of the molecular basis of metastasis. However, their few numbers and difficult isolation hinder its analysis. Apheresis, a process used to isolate a specific component of blood, can efficiently separate peripheral blood monocyte (PBMC), whose density is closely like that of CTCs. In the present study we used the dogs as a precious model of human’s cancers to check the safety and feasibility of apheresis and to separate PBMC and infused MCF7 cells using Spectra Optia apheresis machine (Terumo). The process was performed safely to capture PBMC and MCF7. The captured MCF7 cells were regrown up in vitro and characterized. In conclusion, Spectra Optia apheresis machine (Terumo) can be used safely to isolate CTCs from dogs blood with precautions to keep hemodynamic stability.In patients with solid tumors, circulating tumor cells (CTCs) spread in their blood and function as a seed for metastases. However, the study of CTCs has been limited by their rarity, low frequency, and heterogeneity. The efficient collection of CTCs will contribute to further research of metastatic cancers. Apheresis is a process in which the whole blood of an individual is passed through a machine that isolates a particular constituent and returns the remainder to the circulation. In the present study, we investigated the safety and feasibility of apheresis to separate peripheral blood monocytes (PBMCs), whose density is closely similar to that of CTCs, and to capture intravenously administered human breast cancer cells, MCF7s, from the dogs. No life-threatening events were observed in dogs during the apheresis process. The changes in the hemogram were transient and recovered gradually within a few days after apheresis. During apheresis, 50 mL of PBMCs could be collected from each dog. Notably, a thrombus was formed along the circuit wall during apheresis, which decreased the blood collection pressure. MCF7 cells were successfully captured by the apheresis machine. The captured cells were regrown in vitro and characterized compared with the original cells. In conclusion, apheresis could be safely performed in dogs to isolate CTCs with precautions to maintain hemodynamic stability.

Circulating Tumor Cells: Technologies and Their Clinical Potential in Cancer Metastasis.

Circulating tumor cells (CTCs) are single cells or clusters of cells within the circulatory system of a cancer patient. While most CTCs will perish, a small proportion will proceed to colonize the metastatic niche. The clinical importance of CTCs was reaffirmed by the 2008 FDA approval of CellSearch®, a platform that could extract EpCAM-positive, CD45-negative cells from whole blood samples. Many further studies have demonstrated the presence of CTCs to stratify patients based on overall and progression-free survival, among other clinical indices. Given their unique role in metastasis, CTCs could also offer a glimpse into the genetic drivers of metastasis. Investigation of CTCs has already led to groundbreaking discoveries such as receptor switching between primary tumors and metastatic nodules in breast cancer, which could greatly affect disease management, as well as CTC-immune cell interactions that enhance colonization. In this review, we will highlight the growing variety of isolation techniques for investigating CTCs. Next, we will provide clinically relevant context for CTCs, discussing key clinical trials involving CTCs. Finally, we will provide insight into the future of CTC studies and some questions that CTCs are primed to answer.

Promising Role of Circulating Tumor Cells in the Management of SCLC.

Simple SummaryDespite the recent approval of immune-checkpoint inhibitors, therapeutic strategies for the treatment of small-cell lung cancer (SCLC) patients remained unchanged for decades. The aggressiveness of the disease and the lack of active treatments underlie the need for the identification of biomarkers that can drive therapeutic decisions. Here we discuss the potential role of circulating tumor cells in SCLC research as a promising tool for improving the clinical management of SCLC patients.Small cell lung cancer is an aggressive disease for which few therapeutic options are currently available. Although patients initially respond to therapy, they rapidly relapse. Up to today, no biomarkers for guiding treatment of SCLC patients have been identified. SCLC patients rarely undergo surgery and often the available tissue samples are inadequate for biomarker analysis. Circulating tumor cells (CTCs) are rare cells in the peripheral blood that might be used as surrogates of tissue samples. Different methodological approaches have been developed for studies of CTCs in SCLC. In addition to CTC count, which might provide prognostic and predictive information, genomic and transcriptomic analyses allow the characterization of molecular profiles of CTCs and permit the study of tumor heterogeneity. The employment of CTC-derived xenografts offers complementary information to genomic analyses and CTC enumeration about the mechanisms involved in the sensitivity/resistance to treatments. Using these approaches, CTC analysis is providing relevant information on SCLC biology that might aid in the development of personalized therapeutic strategies for SCLC patients.

Prognostic Significance of Gene Expression and DNA Methylation Markers in Circulating Tumor Cells and Paired Plasma Derived Exosomes in Metastatic Castration Resistant Prostate Cancer

Simple Summary“Liquid biopsy”, based on the analysis of circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA), provides non-invasive real-time monitoring of tumor evolution and therapeutic efficacy. We performed for the first time a direct comparison study on gene expression and DNA methylation markers in CTCs and paired plasma-derived exosomes and evaluated their prognostic significance in metastatic castration resistant prostate cancer. Our results revealed for the first time a significantly higher positivity of all markers in EpCAM-positive CTCs compared to plasma-derived exosomes. We report that in EpCAM-positive CTCs, CK-19, PSMA, TWIST1 expression and GSTP1 methylation are significantly correlated with worse overall survival (OS), while in exosomes, CK-8 expression and GSTP1 and RASSF1A methylation status were significantly correlated with a lower OS. We also enumerated CTC and tumor-derived extracellular vesicles (tdEVs) using CellSearch (CS) and found a correlation between the CTC and tumor-derived extracellular vesicles (tdEVs) enumeration values.Liquid biopsy, based on the analysis of circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA), provides non-invasive real-time monitoring of tumor evolution and therapeutic efficacy. We performed for the first time a direct comparison study on gene expression and DNA methylation markers in CTCs and paired plasma-derived exosomes and evaluated their prognostic significance in metastatic castration resistant prostate cancer. This prospective liquid biopsy (LB) study was based on a group of 62 metastatic castration resistant prostate cancer (mCRPC) patients and 10 healthy donors (HD) as controls. Identical blood draws were used to: (a) enumerate CTC and tumor-derived extracellular vesicles (tdEVs) using CellSearch (CS) and (b) analyze CTCs and paired plasma-derived exosomes at the gene expression and DNA methylation level. CTCs were enumerated using CellSearch in 57/62 patients, with values ranging from 5 to 854 cells/7.5 mL PB. Our results revealed for the first time a significantly higher positivity of gene expression markers (CK-8, CK-18, TWIST1, PSMA, AR-FL, AR-V7, AR-567 and PD-L1 mRNA) in EpCAM-positive CTCs compared to plasma-derived exosomes. GSTP1, RASSF1A and SCHLAFEN were methylated both in CTC and exosomes. In CTCs, Kaplan–Meier analysis revealed that CK-19 (p = 0.009), PSMA (p = 0.001), TWIST1 (p = 0.001) expression and GSTP1 (p = 0.001) methylation were correlated with OS, while in exosomes GSTP1 (p = 0.007) and RASSF1A (p = 0.001) methylation was correlated with OS. Our direct comparison study of CTCs and exosomes at gene expression and DNA methylation level, revealed for the first time a significantly higher positivity in EpCAM-positive CTCs compared to plasma-derived exosomes. Future perspective of this study should be the evaluation of clinical utility of molecular biomarkers in CTCs and exosomes on independent multicentric cohorts with mCRPC patients.

Current Status and Future Perspectives of Liquid Biopsy in Small Cell Lung Cancer.

Approximately 19% of all cancer-related deaths are due to lung cancer, which is the leading cause of mortality worldwide. Small cell lung cancer (SCLC) affects approximately 15% of patients diagnosed with lung cancer. SCLC is characterized by aggressiveness; the majority of SCLC patients present with metastatic disease, and less than 5% of patients are alive at 5 years. The gold standard of SCLC treatment is platinum and etoposide-based chemotherapy; however, its effects are short. In recent years, treatment for SCLC has changed; new drugs have been approved, and new biomarkers are needed for treatment selection. Liquid biopsy is a non-invasive, rapid, repeated and alternative tool to the traditional tumor biopsy that could allow the most personalized medicine into the management of SCLC patients. Circulating tumor cells (CTCs) and cell-free DNA (cfDNA) are the most commonly used liquid biopsy biomarkers. Some studies have reported the prognostic factors of CTCs and cfDNA in SCLC patients, independent of the stage. In this review, we summarize the recent SCLC studies of CTCs, cfDNA and other liquid biopsy biomarkers, and we discuss the future utility of liquid biopsy in the clinical management of SCLC.

DIPG-60. PILOT STUDY OF CIRCULATING TUMOR CELLS IN PEDIATRIC HIGH GRADE BRAIN TUMORS

BACKGROUNDDespite its increasing use, circulating tumor cells (CTCs) have not been studied in pediatric brain tumors.METHODSCell surface vimentin (CSV) is a marker for CTC detection. We developed an automated CSV-based CTC capture method for pediatric brain tumor using the Abnova Cytoquest platform. PBMCs isolated from blood samples from 52 brain tumor patients were processed to isolate CSV+ CTCs. Captured cells were then stained for CSV and CD45 and scanned to determine the number of CTCs. DIPG samples were additionally examined for H3K27M expression on CSV+ cells. Long term cancer survivors were used as a control cohort.RESULTS86.4% of all the samples exhibited between 1–13 CSV+ CTCs, with a median of 2 CSV+ CTCs per sample. Using a value of ≥ 1 CTC as a positive result, the sensitivity and specificity of this test was 83.05% and 60.0% respectively. 19 DIPG samples were analyzed and 70% (13 samples) were positive for 1–5 CTCs. Five of these 7 positive CSV+ CTCs DIPG samples were also positive for H3K27M mutations by immunohistochemistry (71%). Mean survival in days for the CTC positive and negative DIPG samples were 114 and 211 days, respectively (p= 0.13).CONCLUSIONThis is the first study of CTCs in pediatric CNS tumors using an automated approach. Patients with brain tumors can exhibit CSV+ CTCs within peripheral blood. The use of specific molecular markers such as H3K27M can improve the diagnostic capability of liquid biopsies and may enable future disease assessment for personalized therapy.

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.

Abstract IA19: Multiple uses of circulating tumor cells in lung cancer?

Abstract Liquid biopsies are increasingly being used in clinical studies as prognostic, predictive, and pharmacodynamics biomarkers, as surrogates of tumor response, to detect minimal residual disease after treatment with curative intent and to inform on mechanisms of treatment resistance and treatment switching. There is also steady progress in the development of liquid biopsies for early detection of cancers. The advantages of liquid biopsies are that they are minimally invasive and readily repeatable. The liquid biopsy that has been most widely adopted is circulating tumor DNA (ctDNA) as it is readily measured without specialist equipment in most molecular biology laboratories. Circulating tumor cells (CTCs) are technically more challenging and have yet to realize their full potential as biomarkers in clinic. However, CTC technology is constantly improving, and CTCs have several exciting applications beyond ctDNA that, once optimized, will assist personalized cancer medicine, including their use as cultures for real-time therapy testing and their utility, in some cancer types, to derive mouse models. I will discuss the use of CTCs from patients with lung cancer in this presentation. CTCs in both non-small cell lung cancer (NSCLC) and SCLC enumerated by CellSearch (EpCAM and cytokerin positive, CD45 negative) hold prognostic information. However, while CellSearch CTCs are scarce in NSCLC, most likely due to epithelial-to-mesenchymal transition (EMT) that leads to downrgulation of the EpCAM surface marker used to capture them for enumeration, they are prevalent in SCLC. Single CTC copy number analysis has led to the development of classifier that, with further validation studies, could predict response to chemotherapy alongside ctDNA analysis for therapy monitoring. We have exploited SCLC CTC prevalence to derive mouse models in immune-incompetent mice (termed CDX) that allow us to explore biology and test new therapeutics. I will also update on our research using our biobank of 46 CDX models, exploring inter and intratumoral heterogeneity. The most important aspect of this approach is the ability to generate pre- and post-therapy CDX models allowing interrogation of therapy resistance mechanisms and the biology of progressing disease in a tumor type where tumor evolution is rapid and where serial tumor biopsies are rarely obtained. I will also describe our approaches to study mechanisms of tumor dissemination, including vasculogenic mimicry and new models of brain metastasis. More recently, we are developing direct CTC cultures that may allow real-time therapy testing with reporting to the clinic. I will report on our NSCLC CTC studies within the UK TRACERx consortium to study tumor evolution. We have explored the potential of CTCs found in the pulmonary draining vein of stage I-IIIa patients at surgery with curative intent to predict risk of disease recurrence and shown in a case study that a lethal subclone that gives rise to metastasis 10 months later was identified in the pulmonary vein at surgery. In summary, this presentation will exemplify utility of CTCs in lung cancer that are distinct from but complement the implementation of ctDNA. Citation Format: Caroline Dive. Multiple uses of circulating tumor cells in lung cancer? [abstract]. In: Proceedings of the AACR Special Conference on Advances in Liquid Biopsies; Jan 13-16, 2020; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(11_Suppl):Abstract nr IA19.