Prognostic Relevance of Viable Circulating Tumor Cells Detected by EPISPOT in Metastatic Breast Cancer Patients

Factors influencing the diagnostic and prognostic values of circulating tumor cells in breast cancer: a meta-analysis of 8,935 patients

Background

Circulating tumor cells (CTCs) could serve as a predictive biomarker in breast cancer (BC). Due to its high heterogeneity, the diagnostic and prognostic values of CTC are challenging.

Methods

We searched published studies from the databases of PubMed, Cochrane Library, Embase, and MEDLINE. The detection capability and hazard ratios (HRs) of CTCs were extracted as the clinical diagnosis and prognosis evaluation. Subgroup analyses were divided according to the detection methods, continents, treatment periods, therapeutic plans, and cancer stages.

Results

In this study, 35 publications had been retrieved with 8,935 patients enrolled. The diagnostic efficacy of CTC detection has 74% sensitivity and 98% specificity. The positive CTC detection (CTC+ ) would predict worse OS and PFS/DFS in both mid-therapy and post-therapy (HROS, 3.09; 95% CI, 2.17–4.39; HRPFS/DFS, 2.06; 95% CI, 1.72–2.47). Moreover, CTC+ indicated poor survival irrespective of the treatment phases and sampling times (HROS, 2.43; 95% CI, 1.85–3.19; HRPFS/DFS, 1.82; 95% CI, 1.66–1.99). The CTC+ was associated with poor survival regardless of the continents of patients (HROS = 2.43; 95% CI, 1.85–3.19).

Conclusion

Our study suggested that CTC+ was associated with a worse OS and PFS/DFS in the Asian population. The detection method, the threshold level of CTC+ , therapeutic approaches, and sampling times would not affect its diagnostic and prognostic values.

New advances in circulating tumor cell‑mediated metastasis of breast cancer (Review)

Breast cancer stands as the most prevalent form of cancer affecting women, with metastasis serving as a leading cause of mortality among patients with breast cancer. Gaining a comprehensive understanding of the metastatic mechanism in breast cancer is essential for early detection and precision treatment of the disease. Circulating tumor cells (CTCs) play a vital role in this context, representing cancer cells that detach from tumor tissues and enter the bloodstream of cancer patients. These cells travel in the blood circulation as single cells or clusters. Recent research has shed light on the enhanced metastatic potential of CTC clusters compared to single CTCs, despite their limited occurrence. The aim of the present review was to explore recent findings on CTCs with a particular focus on the clustering phenomenon of CTCs observed in breast cancer. Additionally, the present review delved into the comparison between single CTCs and CTC clusters regarding their implications for the treatment and prognosis of patients diagnosed with metastatic breast cancer. By examining the role and mechanisms of CTCs in breast cancer metastasis, the present review provided an improved understanding of CTCs and their significance in early detection of breast cancer metastasis through peripheral blood analysis. Moreover, it contributed to the comprehension of cancer prognosis and prediction by highlighting the implications of CTCs in these aspects. Ultimately, the present study seeks to advance knowledge in the field and pave the way for improved approaches to breast cancer management.

Sequence-Based Platforms for Discovering Biomarkers in Liquid Biopsy of Non-Small-Cell Lung Cancer

Lung cancer detection and monitoring are hampered by a lack of sensitive biomarkers, which results in diagnosis at late stages and difficulty in tracking response to treatment. Recent developments have established liquid biopsies as promising non-invasive methods for detecting biomarkers in lung cancer patients. With concurrent advances in high-throughput sequencing technologies and bioinformatics tools, new approaches for biomarker discovery have emerged. In this article, we survey established and emerging biomarker discovery methods using nucleic acid materials derived from bodily fluids in the context of lung cancer. We introduce nucleic acid biomarkers extracted from liquid biopsies and outline biological sources and methods of isolation. We discuss next-generation sequencing (NGS) platforms commonly used to identify novel biomarkers and describe how these have been applied to liquid biopsy. We highlight emerging biomarker discovery methods, including applications of long-read sequencing, fragmentomics, whole-genome amplification methods for single-cell analysis, and whole-genome methylation assays. Finally, we discuss advanced bioinformatics tools, describing methods for processing NGS data, as well as recently developed software tailored for liquid biopsy biomarker detection, which holds promise for early diagnosis of lung cancer.

Paired Comparison of Routine Molecular Screening of Patient Samples with Advanced Non-Small Cell Lung Cancer in Circulating Cell-Free DNA Using Three Targeted Assays

INTRODUCTION

Progressive advanced non-small cell lung cancer (NSCLC) accounts for about 80-85% of all lung cancers. Approximately 10-50% of patients with NSCLC harbor targetable activating mutations, such as in-frame deletions in Exon 19 (Ex19del) of EGFR. Currently, for patients with advanced NSCLC, testing for sensitizing mutations in EGFR is mandatory prior to the administration of tyrosine kinase inhibitors.

PATIENTS AND METHODS

Plasma was collected from patients with NSCLC. We carried out targeted NGS using the Plasma-SeqSensei™ SOLID CANCER IVD kit on cfDNA (circulating free DNA). Clinical concordance for plasma detection of known oncogenic drivers was reported. In a subset of cases, validation was carried out using an orthogonal OncoBEAM^TM EGFR V2 assay, as well as with our custom validated NGS assay. Somatic alterations were filtered, removing somatic mutations attributable to clonal hematopoiesis for our custom validated NGS assay.

RESULTS

In the plasma samples, driver targetable mutations were studied, with a mutant allele frequency (MAF) ranging from 0.00% (negative detection) to 82.25%, using the targeted next-generation sequencing Plasma-SeqSensei™ SOLID CANCER IVD Kit. In comparison with the OncoBEAM^TM EGFR V2 kit, the EGFR concordance is 89.16% (based on the common genomic regions). The sensitivity and specificity rates based on the genomic regions (EGFR exons 18, 19, 20, and 21) were 84.62% and 94.67%. Furthermore, the observed clinical genomic discordances were present in 25% of the samples: 5% in those linked to the lower of coverage of the OncoBEAM^TM EGFR V2 kit, 7% in those induced by the sensitivity limit on the EGFR with the Plasma-SeqSensei™ SOLID CANCER IVD Kit, and 13% in the samples linked to the larger KRAS, PIK3CA, BRAF coverage of the Plasma-SeqSensei™ SOLID CANCER IVD kit. Most of these somatic alterations were cross validated in our orthogonal custom validated NGS assay, used in the routine management of patients. The concordance is 82.19% in the common genomic regions (EGFR exons 18, 19, 20, 21; KRAS exons 2, 3, 4; BRAF exons 11, 15; and PIK3CA exons 10, 21). The sensitivity and specificity rates were 89.38% and 76.12%, respectively. The 32% of genomic discordances were composed of 5% caused by the limit of coverage of the Plasma-SeqSensei™ SOLID CANCER IVD kit, 11% induced by the sensitivity limit of our custom validated NGS assay, and 16% linked to the additional oncodriver analysis, which is only covered by our custom validated NGS assay.

CONCLUSIONS

The Plasma-SeqSensei™ SOLID CANCER IVD kit resulted in de novo detection of targetable oncogenic drivers and resistance alterations, with a high sensitivity and accuracy for low and high cfDNA inputs. Thus, this assay is a sensitive, robust, and accurate test.

Liquid Biopsies, Novel Approaches and Future Directions

Cancer is among the leading causes of death worldwide. Early diagnosis and prognosis are vital to improve patients' outcomes. The gold standard of tumor characterization leading to tumor diagnosis and prognosis is tissue biopsy. Amongst the constraints of tissue biopsy collection is the sampling frequency and the incomplete representation of the entire tumor bulk. Liquid biopsy approaches, including the analysis of circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), circulating miRNAs, and tumor-derived extracellular vesicles (EVs), as well as certain protein signatures that are released in the circulation from primary tumors and their metastatic sites, present a promising and more potent candidate for patient diagnosis and follow up monitoring. The minimally invasive nature of liquid biopsies, allowing frequent collection, can be used in the monitoring of therapy response in real time, allowing the development of novel approaches in the therapeutic management of cancer patients. In this review we will describe recent advances in the field of liquid biopsy markers focusing on their advantages and disadvantages.

Diagnostic value of liquid biopsy in the era of precision medicine: 10 years of clinical evidence in cancer

Liquid biopsy is a diagnostic repeatable test, which in last years has emerged as a powerful tool for profiling cancer genomes in real-time with minimal invasiveness and tailoring oncological decision-making. It analyzes different blood-circulating biomarkers and circulating tumor DNA (ctDNA) is the preferred one. Nevertheless, tissue biopsy remains the gold standard for molecular evaluation of solid tumors whereas liquid biopsy is a complementary tool in many different clinical settings, such as treatment selection, monitoring treatment response, cancer clonal evolution, prognostic evaluation, as well as the detection of early disease and minimal residual disease (MRD). A wide number of technologies have been developed with the aim of increasing their sensitivity and specificity with acceptable costs. Moreover, several preclinical and clinical studies have been conducted to better understand liquid biopsy clinical utility. Anyway, several issues are still a limitation of its use such as false positive and negative results, results interpretation, and standardization of the panel tests. Although there has been rapid development of the research in these fields and recent advances in the clinical setting, many clinical trials and studies are still needed to make liquid biopsy an instrument of clinical routine. This review provides an overview of the current and future clinical applications and opening questions of liquid biopsy in different oncological settings, with particular attention to ctDNA liquid biopsy.

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.

Detection of Circulating Tumor Cells in Cerebrospinal Fluid of Patients with Suspected Breast Cancer Leptomeningeal Metastases: A Prospective Study

BACKGROUND

The diagnosis of breast cancer (BC)-related leptomeningeal metastases (LM) relies on the detection of tumor cells in cerebrospinal fluid (CSF) using conventional cytology (gold standard). However, the sensitivity of this technique is low. Our goal was to evaluate whether circulating tumor cell (CTC) detection in CSF using the CellSearch® system could be used for LM diagnosis.

METHODS

This prospective, monocentric study included adult patients with suspected BC-related LM. The clinical sensitivity and specificity of CTC detection in CSF for LM diagnosis were calculated relative to conventional CSF cytology.

RESULTS

Forty-nine eligible patients were included and 40 were evaluable (CTC detection technical failure: n = 8, eligibility criteria failure: n = 1). Cytology was positive in 18/40 patients. CTCs were detected in these 18 patients (median: 5824 CTC, range: 93 to 45052) and in 5/22 patients with negative cytology (median: 2 CTC, range: 1 to 44). The detection of ≥1 CSF CTC was associated with a clinical sensitivity of 100% (95% CI, 82.4-100) and a specificity of 77.3% (95% CI, 64.3-90.3) for LM diagnosis. HER2+ CTCs were detected in the CSF of 40.6% of patients with HER2- BC (median: 500 CTC, range: 13 to 28 320).

CONCLUSIONS

The clinical sensitivity of CTC detection in CSF with the CellSearch® system for LM diagnosis is higher than that of CSF cytology. CTC detection in patients with negative cytology, however, must be further investigated. The finding of HER2+ CTCs in patients with HER2- BC suggests that the HER2 status of LM should be evaluated to increase the treatment opportunities for these patients.

Functional analysis of circulating tumour cells: the KEY to understand the biology of the metastatic cascade

Metastasis formation is the main cause of cancer-related death in patients with solid tumours. At the beginning of this process, cancer cells escape from the primary tumour to the blood circulation where they become circulating tumour cells (CTCs). Only a small subgroup of CTCs will survive during the harsh journey in the blood and colonise distant sites. The in-depth analysis of these metastasis-competent CTCs is very challenging because of their extremely low concentration in peripheral blood. So far, only few groups managed to expand in vitro and in vivo CTCs to be used as models for large-scale descriptive and functional analyses of CTCs. These models have shown already the high variability and complexity of the metastatic cascade in patients with cancer, and open a new avenue for the development of new diagnostic and therapeutic approaches.

Combinatorial Power of cfDNA, CTCs and EVs in Oncology

Liquid biopsy is a promising technique for clinical management of oncological patients. The diversity of analytes circulating in the blood useable for liquid biopsy testing is enormous. Circulating tumor cells (CTCs), cell-free DNA (cfDNA) and extracellular vesicles (EVs), as well as blood cells and other soluble components in the plasma, were shown as liquid biopsy analytes. A few studies directly comparing two liquid biopsy analytes showed a benefit of one analyte over the other, while most authors concluded the benefit of the additional analyte. Only three years ago, the first studies to examine the value of a characterization of more than two liquid biopsy analytes from the same sample were conducted. We attempt to reflect on the recent development of multimodal liquid biopsy testing in this review. Although the analytes and clinical purposes of the published multimodal studies differed significantly, the additive value of the analytes was concluded in almost all projects. Thus, the blood components, as liquid biopsy reservoirs, are complementary rather than competitive, and orthogonal data sets were even shown to harbor synergistic effects. The unmistakable potential of multimodal liquid biopsy testing, however, is dampened by its clinical utility, which is yet to be proven, the lack of methodical standardization and insufficiently mature reimbursement, logistics and data handling.

Liquid biopsy: a step closer to transform diagnosis, prognosis and future of cancer treatments

Over the past decade, invasive techniques for diagnosing and monitoring cancers are slowly being replaced by non-invasive methods such as liquid biopsy. Liquid biopsies have drastically revolutionized the field of clinical oncology, offering ease in tumor sampling, continuous monitoring by repeated sampling, devising personalized therapeutic regimens, and screening for therapeutic resistance. Liquid biopsies consist of isolating tumor-derived entities like circulating tumor cells, circulating tumor DNA, tumor extracellular vesicles, etc., present in the body fluids of patients with cancer, followed by an analysis of genomic and proteomic data contained within them. Methods for isolation and analysis of liquid biopsies have rapidly evolved over the past few years as described in the review, thus providing greater details about tumor characteristics such as tumor progression, tumor staging, heterogeneity, gene mutations, and clonal evolution, etc. Liquid biopsies from cancer patients have opened up newer avenues in detection and continuous monitoring, treatment based on precision medicine, and screening of markers for therapeutic resistance. Though the technology of liquid biopsies is still evolving, its non-invasive nature promises to open new eras in clinical oncology. The purpose of this review is to provide an overview of the current methodologies involved in liquid biopsies and their application in isolating tumor markers for detection, prognosis, and monitoring cancer treatment outcomes.

Advances in microfluidics devices and its applications in personalized medicines

Microfluidics is an exponentially growing area and is being used for numerous applications from basic science to advanced biotechnology and medicines. Microfluidics provides a platform to the research community for studying and building new strategies for the diagnosis and therapeutics applications. In the last decade, microfluidic have enriched the field of diagnostics by providing new solutions which was not possible with conventional detection and treatment methods. Microfluidics has the ability to precisely control and perform high-throughput functions. It has been proven as an efficient and rapid method for biological sample preparation, analysis and controlled drug delivery system. Microfluidics plays significant role in personalized medicine. These personalized medicines are used for medical decisions, practices and other interventions as well as for individual patients based on their predicted response or risk of disease. This chapter highlights microfluidics in developing personalized medical applications for its applications in diseases such as cancer, cardiovascular disease, diabetes, pulmonary disease and several others.

Detection of circulating tumour cells in colorectal cancer: Emerging techniques and clinical implications

Despite several advances in oncological management of colorectal cancer, morbidity and mortality are still high and devastating. The diagnostic evaluation by endoscopy is cumbersome, which is uncomfortable to many. Because of the intra- and inter-tumour heterogeneity and changing tumour dynamics, which is continuous in nature, the diagnostic biopsy and assessment of the pathological sample are difficult and also not adequate. Late manifestation of the disease and delayed diagnosis may lead to relapse or metastases. One of the keys to improving the outcome is early detection of cancer, ease of technology to detect with uniformity, and its therapeutic implications, which are yet to come. "Liquid biopsy" is currently the most recent area of interest in oncology, which may provide important tools regarding the characterization of the primary tumour and its metastasis as cancer cells shed into the bloodstream even at the early stages of the disease. By using this approach, clinicians may be able to find out information about the tumour at a given time. Any of the following three types of sampling of biological material can be used in the "liquid biopsy". These are circulating tumour cells (CTCs), circulating tumour DNA, and exosomes. The most commonly studied amongst the three is CTCs. CTCs with their different applications and prognostic value has been found useful in colorectal cancer detection and therapeutics. In this review, we will discuss various markers for CTCs, the core tools/techniques for detection, and also important findings of clinical studies in colorectal cancer and its clinical implications.

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.

The Plasticity of Circulating Tumor Cells in Ovarian Cancer During Platinum-containing Chemotherapy

BACKGROUND

Circulating tumor cells (CTCs) are a potential source of metastases and relapses. The data on the ovarian cancer (OC) CTCs molecular characteristics are limited.

OBJECTIVE

To assess the TGFβ, CXCL2, VEGFA and ERCC1 expression in two OC CTC subpopulations before and during chemotherapy (CT), and its relation to clinical characteristics.

METHODS

Two CTCs subpopulations (EpCAM+CK18+E-cadherin+; EpCAM+CK18+Vimentin+) were enriched using immunomagnetic separation before treatment and after 3 cycles of platinum-containing CT. Expression of mRNA was assessed using RT-qPCR.

RESULTS

The study included 31 I-IV stage OC patients. During CT, TGFβ levels increased in both fractions (p=0.054) compared with the initial levels. ERCC1 expression in E-cadherin+ CTCs was higher during neoadjuvant than adjuvant CT (p=0.004). CXCL2 level in E-cadherin+ CTCs increased (p=0.038) during neoadjuvant CT compared with the initial. TGF-β expression in vimentin+ CTCs during CT was negatively correlated to disease stage (p=0.003). Principal component analysis before CT revealed a component combining VEGFA, TGFβ, CXCL2, and a component with ERCC1 and VEGFA; during CT, component 1 contained ERCC1 and VEGFA, component 2 - TGFβ and CXCL2 in both fractions. Increased ERCC1 expression in E-cadherin+ CTCs during CT was associated with decreased progression-free survival (PFS) (HR 1.11 (95% CI 1.03-1.21, p=0.009) in multivariate analysis.

CONCLUSION

EpCAM+ OC CTCs are phenotypically heterogeneous, which may reflect variability in their metastatic potential. CT changes the molecular characteristics of CTCs. Expression of TGFβ in EpCAM+ CTCs increases during CT. High ERCC1 expression in EpCAM+CK18+E-cadherin+ CTCs during CT is associated with decreased PFS in OC.

Circulating tumour cells at baseline and late phase of treatment provide prognostic value in breast cancer

To determine the prognostic value of the timing of circulating breast tumour cell measurement during treatment, peripheral blood from 164 patients with breast disease was collected. Circulating tumour cells (CTCs) were enriched by using immunomagnetic nanospheres (IMNs) and were identified by using immunofluorescent staining. The CTC shows nuclear-positive, EpCAM-positive, CK19-positive, and CD45-negative. Patients with CTC positivity (> 19/7.5 mL blood) had shorter progression-free survival (PFS) and overall survival (OS) than those with negative results (≤ 19/7.5 mL blood) at baseline. Surgery caused an increase in the number and prevalence of CTCs, and the effect disappeared on day 14 after surgery. During adjuvant chemotherapy, CTCs detected before therapy was only correlated with PFS; however, CTCs at the end of adjuvant chemotherapy were correlated with both PFS and OS. The PFS and OS of the CTC-positive group were significantly shorter than those of the CTC-negative group at the end-point follow-up visit. The prognostic value of CTCs at different measurement time points was demonstrated during breast cancer treatment. Surgery and chemotherapy affected the prevalence of CTCs, leading to different prognostic relevance of CTCs at different treatment stages. CTCs detected at baseline or in the late phase of treatment are preferable for prognosis.

Clinical Relevance of Viable Circulating Tumor Cells in Patients with Metastatic Colorectal Cancer: The COLOSPOT Prospective Study

Simple Summary

The analysis of circulating tumor cells (CTCs) as a “real-time liquid biopsy” in epithelial tumors for personalized medicine has received tremendous attention over the past years, with important clinical implications. In metastatic colorectal cancer (mCRC), the CellSearch^® system has already demonstrated its prognostic value and interest in monitoring treatment response, but the number of recovered CTCs remains low. In this article, we evaluate the early prognostic and predictive value of viable CTCs in patients with mCRC treated with FOLFIRI–bevacizumab with an alternative approach, the functional EPISPOT assay. This study shows that viable CTCs can be detected in patients with mCRC before and during FOLFIRI–bevacizumab treatment and that CTC detection at D₂₈ and the D₀–D₂₈ CTC kinetics evaluated with the EPISPOT assay are associated with response to treatment.

Abstract

Background: Circulating tumor cells (CTCs) allow the real-time monitoring of tumor course and treatment response. This prospective multicenter study evaluates and compares the early predictive value of CTC enumeration with EPISPOT, a functional assay that detects only viable CTCs, and with the CellSearch^® system in patients with metastatic colorectal cancer (mCRC). Methods: Treatment-naive patients with mCRC and measurable disease (RECIST criteria 1.1) received FOLFIRI–bevacizumab until progression or unacceptable toxicity. CTCs in peripheral blood were enumerated at D₀, D₁₄, D₂₈, D₄₂, and D₅₆ (EPISPOT assay) and at D₀ and D₂₈ (CellSearch^® system). Progression-free survival (PFS) and overall survival (OS) were assessed with the Kaplan–Meier method and log-rank test. Results: With the EPISPOT assay, at least 1 viable CTC was detected in 21% (D₀), 15% (D₁₄), 12% (D₂₈), 10% (D₄₂), and 12% (D₅₆) of 155 patients. PFS and OS were shorter in patients who remained positive, with viable CTCs between D₀ and D₂₈ compared with the other patients (PFS = 7.36 vs. 9.43 months, p = 0.0161 and OS = 25.99 vs. 13.83 months, p = 0.0178). The prognostic and predictive values of ≥3 CTCs (CellSearch^® system) were confirmed. Conclusions: CTC detection at D₂₈ and the D₀–D₂₈ CTC dynamics evaluated with the EPISPOT assay were associated with outcomes and may predict response to treatment.

Detection of cancer metastasis: past, present and future

The clinical importance of metastatic spread of cancer has been recognized for centuries, and melanoma has loomed large in historical descriptions of metastases, as well as the numerous mechanistic theories espoused. The "fatal black tumor" described by Hippocrates in 5000 BC that was later termed "melanose" by Rene Laennec in 1804 was recognized to have the propensity to metastasize by William Norris in 1820. And while the prognosis of melanoma was uniformly acknowledged to be dire, Samuel Cooper described surgical removal as having the potential to improve prognosis. Subsequent to this, in 1898 Herbert Snow was the first to recognize the potential clinical benefit of removing clinically normal lymph nodes at the time of initial cancer surgery. In describing "anticipatory gland excision," he noted that "it is essential to remove, whenever possible, those lymph glands which first receive the infective protoplasm, and bar its entrance into the blood, before they have undergone increase in bulk". This revolutionary concept marked the beginning of a debate that rages today: are regional lymph nodes the first stop for metastases ("incubator" hypothesis) or does their involvement serve as an indicator of aggressive disease with inherent metastatic potential ("marker" hypothesis). Is there a better way to improve prediction of disease outcome? This article attempts to address some of the resultant questions that were the subject of the session "Novel Frontiers in the Diagnosis of Cancer" at the 8th International Congress on Cancer Metastases, held in San Francisco, CA in October 2019. Some of these questions addressed include the significance of sentinel node metastasis in melanoma, and the optimal method for their pathologic analysis. The finding of circulating tumor cells in the blood may potentially supplant surgical techniques for detection of metastatic disease, and we are beginning to perfect techniques for their detection, understand how to apply the findings clinically, and develop clinical followup treatment algorithms based on these results. Finally, we will discuss the revolutionary field of machine learning and its applications in cancer diagnosis. Computer-based learning algorithms have the potential to improve efficiency and diagnostic accuracy of pathology, and can be used to develop novel predictors of prognosis, but significant challenges remain. This review will thus encompass latest concepts in the detection of cancer metastasis via the lymphatic system, the circulatory system, and the role of computers in enhancing our knowledge in this field.

Liquid Biopsy: From Discovery to Clinical Application

Over the past 10 years, circulating tumor cells (CTC) and circulating tumor DNA (ctDNA) have received enormous attention as new biomarkers and subjects of translational research. Although both biomarkers are already used in numerous clinical trials, their clinical utility is still under investigation with promising first results. Clinical applications include early cancer detection, improved cancer staging, early detection of relapse, real-time monitoring of therapeutic efficacy, and detection of therapeutic targets and resistance mechanisms. Here, we propose a conceptual framework of CTC and ctDNA assays and point out current challenges of CTC and ctDNA research, which might structure this dynamic field of translational cancer research. SIGNIFICANCE: The analysis of blood for CTCs or cell-free nucleic acids called "liquid biopsy" has opened new avenues for cancer diagnostics, including early detection of tumors, improved risk assessment and staging, as well as early detection of relapse and monitoring of tumor evolution in the context of cancer therapies.

Liquid biopsy in head and neck squamous cell carcinoma: circulating tumor cells, circulating tumor DNA, and exosomes

Introduction: Head and neck squamous cell carcinoma (HNSCC) is one of the most common cancers worldwide. Due to a lack of reliable markers, HNSCC patients are usually diagnosed at a late stage, which will lead to a worse outcome. Therefore, it is critical to improve the clinical management of cancer patients. Nowadays, the development of liquid biopsy enables a minimally invasive manner to extract molecular information from HNSCCs. Thus, this review aims to outline the clinical value of liquid biopsy in early detection, real-time monitoring, and prognostic evaluation of HNSCC. Areas covered: This comprehensive review focused on the characteristics as well as clinical applications of three liquid biopsy markers (CTCs, ctDNA, and exosomes) in HNSCC. What is more, it is promising to incorporate machine learning and 3D organoid models in the liquid biopsy of HNSCC. Expert opinion: Liquid biopsy provides a noninvasive technique to reflect the inter and intra-lesional heterogeneity through the detection of tumor cells or materials released from the primary and secondary tumors. Recently, some evolving technologies have the potential to combine with liquid biopsy to improve clinical management of HNSCC patients.

Molecular and Functional Characterization of Circulating Tumor Cells: From Discovery to Clinical Application

BACKGROUND

One of the objectives for the liquid biopsy is to become a surrogate to tissue biopsies in diagnosis of cancer as a minimally invasive method, with clinical utility in real-time follow-ups of patients. To achieve this goal, it is still necessary to achieve a better understanding of the mechanisms of cancer and the biological principles that govern its behavior, particularly with regard to circulating tumor cells (CTCs).

CONTENT

The isolation, enumeration, detection, and characterization of CTCs have already proven to provide relevant clinical information about patient prognosis and treatment prediction. Moreover, CTCs can be analyzed at the genome, proteome, transcriptome, and secretome levels and can also be used for functional studies in in vitro and in vivo models. These features, taken together, have made CTCs a very valuable biosource.

SUMMARY

To further advance the field and discover new clinical applications for CTCs, several studies have been performed to learn more about these cells and better understand the biology of metastasis. In this review, we describe the recent literature on the topic of liquid biopsy with particular focus on the biology of CTCs.

Circulating Tumor Cell Detection Technologies and Clinical Utility: Challenges and Opportunities

The potential clinical utility of circulating tumor cells (CTCs) in the diagnosis and management of cancer has drawn a lot of attention in the past 10 years. CTCs disseminate from tumors into the bloodstream and are believed to carry vital information about tumor onset, progression, and metastasis. In addition, CTCs reflect different biological aspects of the primary tumor they originate from, mainly in their genetic and protein expression. Moreover, emerging evidence indicates that CTC liquid biopsies can be extended beyond prognostication to pharmacodynamic and predictive biomarkers in cancer patient management. A key challenge in harnessing the clinical potential and utility of CTCs is enumerating and isolating these rare heterogeneous cells from a blood sample while allowing downstream CTC analysis. That being said, there have been serious doubts regarding the potential value of CTCs as clinical biomarkers for cancer due to the low number of promising outcomes in the published results. This review aims to present an overview of the current preclinical CTC detection technologies and the advantages and limitations of each sensing platform, while surveying and analyzing the published evidence of the clinical utility of CTCs.

Characterization of circulating breast cancer cells with tumorigenic and metastatic capacity

Functional studies giving insight into the biology of circulating tumor cells (CTCs) remain scarce due to the low frequency of CTCs and lack of appropriate models. Here, we describe the characterization of a novel CTC‐derived breast cancer cell line, designated CTC‐ITB‐01, established from a patient with metastatic estrogen receptor‐positive (ER⁺) breast cancer, resistant to endocrine therapy. CTC‐ITB‐01 remained ER⁺ in culture, and copy number alteration (CNA) profiling showed high concordance between CTC‐ITB‐01 and CTCs originally present in the patient with cancer at the time point of blood draw. RNA‐sequencing data indicate that CTC‐ITB‐01 has a predominantly epithelial expression signature. Primary tumor and metastasis formation in an intraductal PDX mouse model mirrored the clinical progression of ER⁺ breast cancer. Downstream ER signaling was constitutively active in CTC‐ITB‐01 independent of ligand availability, and the CDK4/6 inhibitor Palbociclib strongly inhibited CTC‐ITB‐01 growth. Thus, we established a functional model that opens a new avenue to study CTC biology.

The Utility of Liquid Biopsies in Radiation Oncology

The use of therapeutic radiation is primarily guided by clinicopathologic factors and medical imaging, whereas molecular biomarkers currently play a comparatively minor role in most settings. Liquid biopsies provide a rich source of noninvasive tumor-specific biomarkers and are amenable to repeated and noninvasive assessment. Here, we review the current status of liquid biopsies and their potential impact on the field of radiation oncology. We focus on established and emerging approaches to analyze circulating tumor DNA and circulating tumor cells from peripheral blood. These promising classes of biomarkers could have an outsized impact on cancer management by meaningfully stratifying patients into risk groups, tracking radiation therapy efficacy during and after treatment, and identifying patients with radiosensitive or radioresistant disease. Finally, we highlight opportunities for future investigation including the need for prospective interventional studies employing liquid biopsies to guide the management of radiation therapy-treated patients.

Clinical significance of circulating tumor cells in patients with locally advanced head and neck squamous cell carcinoma

The present study aimed to investigate the clinical relevance of circulating tumor cells (CTCs) in patients with locally advanced head and neck squamous cell carcinoma (LA‑HNSCC), particularly in patients with nasopharyngeal and hypopharyngeal squamous cell carcinoma. CTCs were isolated using negative immunomagnetic bead enrichment and were identified by fluorescence in situ hybridization. Youden's index and the receiver operating characteristic (ROC) curve were used to select the optimal CTC baseline value. χ2 test or Fisher's test were used to determine the association between CTC counts and clinical parameters, curative effects and prognosis. The Kaplan‑Meier estimator was used to analyze overall survival (OS) and progression‑free survival (PFS). In the present study, 356 peripheral blood samples (178 pretreatment samples and 178 post‑treatment samples) from 178 patients were examined. The results revealed that the pretreatment CTC detection rate was 73.8%. The minimum, maximum and median CTC counts were 1, 22 and 2/3.2 ml, respectively. The number of polyploid CTCs was associated with distant metastasis (P=0.026). In addition, patients with undetectable CTCs, and decreasing or negative CTCs post‑treatment tended to have a good prognosis (P<0.05). For nasopharyngeal squamous cell carcinoma, the PFS of patients with increased CTCs and CTCs ≥2/3.2 ml after treatment was significantly lower (P<0.05). For hypopharyngeal squamous cell carcinoma, it was suggested that CTCs with a cutoff value of 3 may be used to evaluate PFS and OS before and after treatment. In conclusion, CTCs may be used to monitor disease progression and the response to chemoradiotherapy for patients with LA‑HNSCC. Furthermore, CTCs are a better predictor of the prognosis of hypopharyngeal squamous cell carcinoma than that of nasopharyngeal squamous cell carcinoma.

Circulating Tumor Cells as a Marker of Disseminated Disease in Patients with Newly Diagnosed High-Risk Prostate Cancer

The aim of this study was to investigate whether the enumeration of circulating tumor cells (CTCs) in blood can differentiate between true localized and metastatic prostate cancer. A cross-sectional study of 104 prostate cancer patients with newly diagnosed high-risk prostate cancer was conducted. In total, 19 patients presented metastatic disease and 85 were diagnosed with localized disease. Analyses included intergroup comparison of CTC counts, determined using the CellSearch® system, EPISPOT assay and GILUPI CellCollector®, and ROC analysis verifying the accuracy of CTC count as a maker of disseminated prostate cancer. The vast majority (94.7%) of patients with advanced-stage cancer tested positively for CTCs in at least one of the assays. However, significantly higher CTC counts were determined with the CellSearch® system compared to EPISPOT assay and GILUPI CellCollector®. Identification of ≥4 CTCs with the CellSearch® system was the most accurate predictor of metastatic disease (sensitivity 0.500; specificity 0.900; AUC (95% CI) 0.760 (0.613-0.908). Furthermore, we tried to create a model to enhance the specificity and sensitivity of metastatic prediction with CTC counts by incorporating patient's clinical data, including PSA serum levels, Gleason score and clinical stage. The composite biomarker panel achieved the following performance: sensitivity, 0.611; specificity, 0.971; AUC (95% CI), 0.901 (0.810-0.993). Thus, although the sensitivity of CTC detection needs to be further increased, our findings suggest that high CTC counts might contribute to the identification of high-risk prostate cancer patients with occult metastases at the time of diagnosis.

Methodology for the Isolation and Analysis of CTCs

The majority of deaths related to breast cancer are caused by metastasis. Understanding the process of metastasis is key to achieve a reduction on breast cancer mortality. Currently, liquid biopsies are gaining attention in this regard. Circulating tumor cells (CTCs), an important component of liquid biopsies, are cells shed from primary tumor that disseminate to blood circulation being responsible of distal metastasis. Hence, the study CTCs is a promising alternative to monitor the progress of metastasis disease and can be used for early diagnosis of cancers as well as for earlier assessment of cancer recurrence and therapy efficacy. Despite their clinical interest, CTC analysis is not recommended by oncology guidelines so far. The main reason is that there is no gold standard technology for CTCs isolation and most of the current technologies are not yet validated for clinical use. In this chapter we will focus on the most relevant technologies for CTC isolation based on their properties and depending on whether it is a positive or negative selection. We also describe each technology based on its potential use and its relevance in breast cancer. The chapter also contains a future perspective including the challenges and requirements of CTC detection.

Prognostic and therapeutic significance of circulating tumor cells in patients with lung cancer

BACKGROUND

Lung cancer is the second most common cancer and the main cause of cancer-related mortality worldwide. In spite of various efforts that have been made to facilitate the early diagnosis of lung cancer, most patients are diagnosed when the disease is already in stage IV, which is generally associated with the occurrence of distant metastases and a poor survival. Moreover, a large proportion of these patients will relapse after treatment, heralding the need for the stratification of lung cancer patients in addition to identifying those who are at a higher risk of relapse and, thus, require alternative and/or additional therapies. Recently, circulating tumor cells (CTCs) have been considered as valuable markers for the early diagnosis, prognosis and risk stratification of cancer patients, and they have been found to be able to predict the survival of patients with various types of cancer, including lung cancer. Additionally, the characterization of CTCs has recently provided fascinating insights into the heterogeneity of tumors, which may be instrumental for the development of novel targeted therapies.

CONCLUSIONS

Here we review our current understanding of the significance of CTCs in lung cancer metastasis. We also discuss prominent studies reporting the utility of enumeration and characterization of CTCs in lung cancer patients as prognostic and pharmacodynamic biomarkers for those who are at a higher risk of metastasis and drug resistance.

Circulating Tumor Cells as a Prognostic Factor in Recurrent or Metastatic Head and Neck Squamous Cell Carcinoma: The CIRCUTEC Prospective Study

BACKGROUND

This prospective multicenter study evaluated the prognostic value of circulating tumor cells (CTCs) in relapsing nonoperable or metastatic head and neck squamous cell carcinoma (rHNSCC) treated by chemotherapy and cetuximab.

METHODS

In 65 patients suitable for analyses, peripheral blood was taken at day 0 (D0) D7, and D21 of treatment for CTC detection by CellSearch®, EPISPOT, and flow cytometry (FCM). Progression-free survival (PFS) was assessed with the Kaplan–Meier method and compared with the log-rank test (P &lt; 0.05).

RESULTS

At D0, CTCs were detected with EPISPOT, CellSearch, and FCM in 69% (45/65), 21% (12/58), and 11% (7/61) of patients, respectively. In the patients tested with all 3 methods, EPISPOT identified 92% (36/39), 92% (35/38), and 90% (25/28) of all positive samples at D0, D7, and D21, respectively. Median PFS time was significantly lower in (a) patients with increasing or stable CTC counts (36/54) from D0 to D7 with EPISPOTEGFR (3.9 vs 6.2 months; 95% CI, 5.0–6.9; P = 0.0103) and (b) patients with ≥1 CTC detected with EPISPOT or CellSearch® (37/51) (P = 0.0311), EPISPOT or FCM (38/54) (P = 0.0480), and CellSearch or FCM (11/51) (P = 0.0005) at D7.

CONCLUSIONS

CTCs can be detected before and during chemotherapy in patients with rHNSCC. D0–D7 CTC kinetics evaluated with EPISPOTEGFR are associated with the response to treatment. This study indicates that CTCs can be used as a real-time liquid biopsy to monitor the early response to chemotherapy in rHNSCC.

ClinicalTrials.gov Identifier

NCT02119559

CTC analysis: an update on technological progress

There is a growing need for a more accurate, real-time assessment of tumor status and the probability of metastasis, relapse, or response to treatment. Conventional means of assessment include imaging and tissue biopsies that can be highly invasive, may not provide complete information of the disease's heterogeneity, and not ideal for repeat analysis. Therefore, a less-invasive means of acquiring similar information at greater time points is necessary. Liquid biopsies are samples of a patients' peripheral blood and hold potential of addressing these criteria. Ongoing research has revealed that a tumor can release circulating cells, genetic materials (DNA or RNA), and exosomes into circulation. These potential biomarkers can be captured in a liquid biopsy and analyzed to determine disease status. To achieve these goals, numerous technologies have been developed. In this review, we discuss both prominent and newly developed technologies for circulating tumor cell capture and analysis and their clinical impact.

Epithelial keratins: Biology and implications as diagnostic markers for liquid biopsies

Keratins are essential elements of the cytoskeleton of normal and malignant epithelial cells. Because carcinomas commonly maintain their specific keratin expression pattern during malignant transformation, keratins are extensively used as tumor markers in cancer diagnosis including the detection of circulating tumor cells in blood of carcinoma patients. Interestingly, recent biological insights demonstrate that epithelial keratins should not only be considered as mere tumor markers. Emerging evidence suggests an active biological role of keratins in tumor cell dissemination and metastasis. In this review, we illustrate the family of keratin proteins, summarize the latest biological insights into keratin function related to cancer metastasis and discuss the current use of keratins for detection of CTCs and other blood biomarkers used in oncology.

Panoptic View of Prognostic Models for Personalized Breast Cancer Management

The efforts to personalize treatment for patients with breast cancer have led to a focus on the deeper characterization of genotypic and phenotypic heterogeneity among breast cancers. Traditional pathology utilizes microscopy to profile the morphologic features and organizational architecture of tumor tissue for predicting the course of disease, and is the first-line set of guiding tools for customizing treatment decision-making. Currently, clinicians use this information, combined with the disease stage, to predict patient prognosis to some extent. However, tumoral heterogeneity stubbornly persists among patient subgroups delineated by these clinicopathologic characteristics, as currently used methodologies in diagnostic pathology lack the capability to discern deeper genotypic and subtler phenotypic differences among individual patients. Recent advancements in molecular pathology, however, are poised to change this by joining forces with multiple-omics technologies (genomics, transcriptomics, epigenomics, proteomics, and metabolomics) that provide a wealth of data about the precise molecular complement of each patient's tumor. In addition, these technologies inform the drivers of disease aggressiveness, the determinants of therapeutic response, and new treatment targets in the individual patient. The tumor architecture information can be integrated with the knowledge of the detailed mutational, transcriptional, and proteomic phenotypes of cancer cells within individual tumors to derive a new level of biologic insight that enables powerful, data-driven patient stratification and customization of treatment for each patient, at each stage of the disease. This review summarizes the prognostic and predictive insights provided by commercially available gene expression-based tests and other multivariate or clinical -omics-based prognostic/predictive models currently under development, and proposes a more inclusive multiplatform approach to tackling the challenging heterogeneity of breast cancer to individualize its management. "The future is already here-it's just not very evenly distributed."-William Ford Gibson.

S100-EPISPOT: A New Tool to Detect Viable Circulating Melanoma Cells

Metastatic melanoma is one of the most aggressive and drug-resistant cancers with very poor overall survival. Circulating melanoma cells (CMCs) were first described in 1991. However, there is no general consensus on the clinical utility of CMC detection, largely due to conflicting results linked to the use of heterogeneous patient populations and different detection methods. Here, we developed a new EPithelial ImmunoSPOT (EPISPOT) assay to detect viable CMCs based on their secretion of the S100 protein (S100-EPISPOT). Then, we compared the results obtained with the S100-EPISPOT assay and the CellSearch^® CMC kit using blood samples from a homogeneous population of patients with metastatic melanoma. We found that S100-EPISPOT sensitivity was significantly higher than that of CellSearch^®. Specifically, the percentage of patients with ≥2 CMCs was significantly higher using S100-EPISPOT than CellSearch^® (48% and 21%, respectively; p = 0.0114). Concerning CMC prognostic value, only the CellSearch^® results showed a significant association with overall survival (p = 0.006). However, due to the higher sensitivity of the new S100-EPISPOT assay, it would be interesting to determine whether this functional test could be used in patients with non-metastatic melanoma for the early detection of tumor relapse and for monitoring the treatment response.

Human-specific RNA analysis shows uncoupled epithelial-mesenchymal plasticity in circulating and disseminated tumour cells from human breast cancer xenografts

Blood samples, bone marrow, tumours and metastases where possible were collected from SCID mice bearing orthotopic xenografts of the triple-negative MDA-MB-468 cell line or a transplantable ER-positive patient derived xenograft (ED-03), and assessed using human-specific, tandem-nested RT-qPCR for markers relating to detection of circulating (CTCs) and disseminated tumour cells (DTCs), breast cancer clinicopathology, the 'cancer stem cell' phenotype, metabolism, hypoxia and epithelial-mesenchymal plasticity (EMP). Increased levels of SNAI1, ILK, NOTCH1, CK20, and PGR, and a decrease/loss of EPCAM in CTCs/DTCs were observed relative to the primary xenograft across both models. Decreased CD24 and EGFR was restricted to the MDA-MB-468 model, while increased TFF1 was seen in the ED-03 model. The major metabolic regulator PPARGC1A, and several hypoxia-related markers (HIF1A, APLN and BNIP3) were significantly elevated in both models. Increased expression of mesenchymal markers including SNAI1 was seen across both models, however CDH1 did not decrease concordantly, and several other epithelial markers were increased, suggesting an uncoupling of EMP to produce an EMP hybrid or partial-EMT. Single cell analysis of ED-03 CTCs, although limited, indicated uncoupling of the EMP axis in single hybrid cells, rather than distinct pools of epithelial or mesenchymal-enriched cells, however dynamic heterogeneity between CTCs/DTCs cannot be ruled out. Reduced CD24 expression was observed in the MDA-MB-468 CTCs, consistent with the 'breast cancer stem cell' phenotype, and metastatic deposits in this model mostly resembled the primary xenografts, consistent with the mesenchymal-epithelial transition paradigm.

Analysis of Circulating Tumor Cells in Patients with Non-Metastatic High-Risk Prostate Cancer before and after Radiotherapy Using Three Different Enumeration Assays

The characterization of circulating tumor cells (CTCs) can lead to a promising strategy for monitoring residual or relapsing prostate cancer (PCa) after local therapy. The aim of this study was to compare three innovative technologies for CTC enumeration in 131 high-risk patients with PCa, before and after radiotherapy, combined with androgen deprivation. The CTC number was tested using the FDA-cleared CellSearch^® system, the dual fluoro-EPISPOT assay that only detects functional CTCs, and the in vivo CellCollector^® technology. The highest percentage of CTC-positive patients was detected with the CellCollector^® (48%) and dual fluoro-EPISPOT (42%) assays, while the CellSearch^® system presented the lowest rate (14%). Although the concordance among methods was only 23%, the cumulative positivity rate was 79%. A matched-pair analysis of the samples before, and after, treatment suggested a trend toward a decrease in CTC count after treatment with all methods. CTC tended to be positivity correlated with age for the fluoro-EPISPOT assay and with PSA level from the data of three assays. Combining different CTC assays improved CTC detection rates in patients with non-metastatic high-risk PCa before and after treatment. Our findings do not support the hypothesis that radiotherapy leads to cancer cell release in the circulation.

A Silicon-based Coral-like Nanostructured Microfluidics to Isolate Rare Cells in Human Circulation: Validation by SK-BR-3 Cancer Cell Line and Its Utility in Circulating Fetal Nucleated Red Blood Cells

Circulating fetal cells (CFCs) in maternal blood are rare but have a strong potential to be the target for noninvasive prenatal diagnosis (NIPD). "Cell Reveal^TM system" is a silicon-based microfluidic platform capable to capture rare cell populations in human circulation. The platform is recently optimized to enhance the capture efficiency and system automation. In this study, spiking tests of SK-BR-3 breast cancer cells were used for the evaluation of capture efficiency. Then, peripheral bloods from 14 pregnant women whose fetuses have evidenced non-maternal genomic markers (e.g., de novo pathogenic copy number changes) were tested for the capture of circulating fetal nucleated red blood cells (fnRBCs). Captured cells were subjected to fluorescent in situ hybridization (FISH) on chip or recovered by an automated cell picker for molecular genetic analyses. The capture rate for the spiking tests is estimated as 88.1%. For the prenatal study, 2⁻71 fnRBCs were successfully captured from 2 mL of maternal blood in all pregnant women. The captured fnRBCs were verified to be from fetal origin. Our results demonstrated that the Cell Reveal^TM system has a high capture efficiency and can be used for fnRBC capture that is feasible for the genetic diagnosis of fetuses without invasive procedures.

Prostate-specific markers to identify rare prostate cancer cells in liquid biopsies

Despite improvements in early detection and advances in treatment, patients with prostate cancer continue to die from their disease. Minimal residual disease after primary definitive treatment can lead to relapse and distant metastases, and increasing evidence suggests that circulating tumour cells (CTCs) and bone marrow-derived disseminated tumour cells (BM-DTCs) can offer clinically relevant biological insights into prostate cancer dissemination and metastasis. Using epithelial markers to accurately detect CTCs and BM-DTCs is associated with difficulties, and prostate-specific markers are needed for the detection of these cells using rare cell assays. Putative prostate-specific markers have been identified, and an optimized strategy for staining rare cancer cells from liquid biopsies using these markers is required. The ideal prostate-specific marker will be expressed on every CTC or BM-DTC throughout disease progression (giving high sensitivity) and will not be expressed on non-prostate-cancer cells in the sample (giving high specificity). Some markers might not be specific enough to the prostate to be used as individual markers of prostate cancer cells, whereas others could be truly prostate-specific and would make ideal markers for use in rare cell assays. The goal of future studies is to use sensitive and specific prostate markers to consistently and reliably identify rare cancer cells.

Circulating tumor cells (CTCs) for the noninvasive monitoring and personalization of non-small cell lung cancer (NSCLC) therapies

Growing evidences for tumor heterogeneity confirm that single-tumor biopsies frequently fail to reveal the widespread mutagenic profile of tumor. Repeated biopsies are in most cases unfeasible, especially in advanced cancers. We describe here how circulating tumor cells (CTCs) isolated from minimally invasive blood sample might inform us about intratumor heterogeneity, tumor evolution and treatment resistance. We also discuss the advances of CTCs research, most notably in molecularly selected non-small cell lung cancer (NSCLC) patients, highlighting challenges and opportunities related to personalized therapy.

RNA Profiles of Circulating Tumor Cells and Extracellular Vesicles for Therapy Stratification of Metastatic Breast Cancer Patients

BACKGROUND

Liquid biopsies are discussed to provide surrogate markers for therapy stratification and monitoring. We compared messenger RNA (mRNA) profiles of circulating tumor cells (CTCs) and extracellular vesicles (EVs) in patients with metastatic breast cancer (MBC) to estimate their utility in therapy management.

METHODS

Blood was collected from 35 hormone receptor-positive/HER2-negative patients with MBC at the time of disease progression and at 2 consecutive staging time points. CTCs were isolated from 5 mL of blood by positive immunomagnetic selection, and EVs from 4 mL of plasma by a membrane affinity-based procedure. mRNA was reverse transcribed, preamplified, and analyzed for 18 genes by multimarker quantitative polymerase chain reaction (qPCR) assays. RNA profiles were normalized to healthy donor controls (n = 20), and results were correlated with therapy outcome.

RESULTS

There were great differences in mRNA profiles of EVs and CTCs, with only 5% (21/403) of positive signals identical in both fractions. Transcripts involved in the PI3K signaling pathway were frequently overexpressed in CTCs, and AURKA, PARP1, and SRC signals appeared more often in EVs. Of all patients, 40% and 34% showed ERBB2 and ERBB3 signals, respectively, in CTCs, which was significantly associated with disease progression (P = 0.007). Whereas MTOR signals in CTCs significantly correlated with response (P = 0.046), signals in EVs indicated therapy failure (P = 0.011). The presence of AURKA signals in EVs seemed to be a marker for the indication of unsuccessful treatment of bone metastasis.

CONCLUSIONS

These results emphasize the potential of CTCs and EVs for therapy monitoring and the need for critical evaluation of the implementation of any liquid biopsy in clinical practice.

Impact of label-free technologies in head and neck cancer circulating tumour cells

Background

The ability to identify high risk head and neck cancer (HNC) patients with disseminated disease prior to presenting with clinically detectable metastases holds remarkable potential. A fraction of circulating tumour cells (CTCs) are invasive cancer cells which mediate metastasis by intravasation, survival and extravasation from the blood stream to metastatic sites. CTCs have been cleared by the FDA for use as surrogate markers of overall survival and progression free survival for breast, prostate and colorectal cancers using the CellSearch^® system. However, the clinical significance of CTCs in head and neck cancer patients has yet to be determined. There has been a significant shift in CTC enrichment platforms, away from exclusively single marker selection, to epitope-independent systems.

Methods

The aim of this study was to screen advanced stage HNC patients by the CellSearch^® platform and utilise two other epitope-independent approaches, ScreenCell^® (microfiltration device) and RosetteSep^™ (negative enrichment), to determine how a shift to such methodologies would enable CTC enrichment and detection.

Results

In advanced stage HNC patients, single CTCs were detected in 8/43 (18.6%) on CellSearch^®, 13/28 (46.4%) on ScreenCell^® and 16/25 (64.0%) by RosetteSep™ (the latter could also detect CTC clusters). Notably, in patients with suspicious lung nodules, too small to biopsy, CTCs were found upon presentation. Moreover, CTCs were readily detected in advanced stage HNC patients.

Conclusion

The epitope-independent platforms detected higher CTC numbers and clusters. Further studies are needed to ascertain whether CTCs can be used as independent prognostic markers for HNCs.

Establishment of a multimarker qPCR panel for the molecular characterization of circulating tumor cells in blood samples of metastatic breast cancer patients during the course of palliative treatment

Background

Circulating tumor cells (CTC) are discussed to be an ideal surrogate marker for individualized treatment in metastatic breast cancer (MBC) since metastatic tissue is often difficult to obtain for repeated analysis. We established a nine gene qPCR panel to characterize the heterogeneous CTC population in MBC patients including epithelial CTC, their receptors (EPCAM, ERBB2, ERBB3, EGFR) CTC in Epithelial-Mesenchymal-Transition [(EMT); PIK3CA, AKT2), stem cell-like CTC (ALDH1) as well as resistant CTC (ERCC1, AURKA] to identify individual therapeutic targets.

Results

At TP0, at least one marker was detected in 84%, at TP1 in 74% and at TP2 in 79% of the patients, respectively. The expression of ERBB2, ERBB3 and ERCC1 alone or in combination with AURKA was significantly associated with therapy failure. ERBB2 + CTC were only detected in patients not receiving ERBB2 targeted therapies which correlated with no response. Furthermore, patients responding at TP2 had a significantly prolonged overall-survival than patients never responding (p = 0.0090).

Patients and Methods

2 × 5 ml blood of 62 MBC patients was collected at the time of disease progression (TP0) and at two clinical staging time points (TP1 and TP2) after 8–12 weeks of chemo-, hormone or antibody therapy for the detection of CTC (AdnaTest EMT-2/StemCell Select™, QIAGEN Hannover GmbH, Germany). After pre-amplification, multiplex qPCR was performed. Establishment was performed using various cancer cell lines. PTPRC (Protein tyrosine phosphatase receptor type C) and GAPDH served as controls.

Conclusions

Monitoring MBC patients using a multimarker qPCR panel for the characterization of CTC might help to treat patients accordingly in the future.

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.

Noninvasive prenatal diagnosis of fetal aneuploidy by circulating fetal nucleated red blood cells and extravillous trophoblasts using silicon-based nanostructured microfluidics

BACKGROUND

Noninvasive prenatal testing (NIPT) based on cell-free DNA in maternal circulation has been accepted worldwide by the clinical community since 2011 but limitations, such as maternal malignancy and fetoplacental mosaicism, preclude its full replacement of invasive prenatal diagnosis. We present a novel silicon-based nanostructured microfluidics platform named as "Cell Reveal™" to demonstrate the feasibility of capturing circulating fetal nucleated red blood cells (fnRBC) and extravillous cytotrophoblasts (EVT) for cell-based noninvasive prenatal diagnosis (cbNIPD).

METHODS

The "Cell Reveal™" system is a silicon-based, nanostructured microfluidics using immunoaffinity to capture the trophoblasts and the nucleated RBC (nRBC) with specific antibodies. The automated computer analysis software was used to identify the targeted cells through additional immunostaining of the corresponding antigens. The identified cells were retrieved for whole genome amplification for subsequent investigations by micromanipulation in one microchip, and left in situ for subsequent fluorescence in situ hybridization (FISH) in another microchip. When validation, bloods from pregnant women (n = 24) at gestational age 11-13+6 weeks were enrolled. When verification, bloods from pregnant women (n = 5) receiving chorionic villus sampling or amniocentesis at gestation age 11+4-21 weeks with an aneuploid or euploid fetus were enrolled, followed by genetic analyses using FISH, short tandem repeat (STR) analyses, array comparative genomic hybridization, and next generation sequencing, in which the laboratory is blind to the fetal genetic complement.

RESULTS

The numbers of captured targeted cells were 1-44 nRBC/2 ml and 1-32 EVT/2 ml in the validation group. The genetic investigations performed in the verification group confirmed the captured cells to be fetal origin. In every 8 ml of the maternal blood being blindly tested, both fnRBC and EVT were always captured. The numbers of captured fetal cells were 14-22 fnRBC/4 ml and 1-44 EVT/4 ml of maternal blood.

CONCLUSIONS

This report is one of the first few to verify the capture of fnRBC in addition to EVT. The scalability of our automated system made us one step closer toward the goal of in vitro diagnostics.

Molecular characterization of circulating tumor cells-from bench to bedside

Circulating tumor cells (CTCs) are cancer cells discovered in cancer patients' peripheral blood that successfully escape from the primary tumor site and/or metastases, struggle to survive in the bloodstream, and have potential for seeding metastases. Numerous methods have been proposed to capture CTCs. The value of CTCs as a means of understanding cancer metastasis and a major form of 'liquid biopsy' has been widely demonstrated. Recently, single-cell molecular analyses of CTCs have provided profound biological insights into tumor heterogeneity, mechanism of metastasis and tumor evolution. In addition, because CTC analysis is non-invasive, CTCs exhibit great potential as biomarkers for assessment of cancer prognosis and therapy response. In this review, we summarize modern technologies for CTC detection and isolation, single-cell genomic/transcriptomic characterization of CTCs, and prospective clinical applications of CTCs. We expect that, after further technical improvements in methods of detection and sequencing, CTC analyses will shed new light on the mechanisms driving cancer metastasis and benefit many cancer patients.

Detection of Activating Estrogen Receptor Gene (ESR1) Mutations in Single Circulating Tumor Cells

Purpose: Early detection is essential for treatment plans before onset of metastatic disease. Our purpose was to demonstrate feasibility to detect and monitor estrogen receptor 1 (ESR1) gene mutations at the single circulating tumor cell (CTC) level in metastatic breast cancer (MBC).Experimental Design: We used a CTC molecular characterization approach to investigate heterogeneity of 14 hotspot mutations in ESR1 and their correlation with endocrine resistance. Combining the CellSearch and DEPArray technologies allowed recovery of 71 single CTCs and 12 WBC from 3 ER-positive MBC patients. Forty CTCs and 12 WBC were subjected to whole genome amplification by MALBAC and Sanger sequencing.Results: Among 3 selected patients, 2 had an ESR1 mutation (Y537). One showed two different ESR1 variants in a single CTC and another showed loss of heterozygosity. All mutations were detected in matched cell-free DNA (cfDNA). Furthermore, one had 2 serial blood samples analyzed and showed changes in both cfDNA and CTCs with emergence of mutations in ESR1 (Y537S and T570I), which has not been reported previously.Conclusions: CTCs are easily accessible biomarkers to monitor and better personalize management of patients with previously demonstrated ER-MBC who are progressing on endocrine therapy. We showed that single CTC analysis can yield important information on clonal heterogeneity and can be a source of discovery of novel and potential driver mutations. Finally, we also validate a workflow for liquid biopsy that will facilitate early detection of ESR1 mutations, the emergence of endocrine resistance and the choice of further target therapy. Clin Cancer Res; 23(20); 6086-93. ©2017 AACR.