Fugitives on the run: circulating tumor cells (CTCs) in metastatic diseases

Advances in the role of circulating tumor cell heterogeneity in metastatic small cell lung cancer

Small cell lung cancer (SCLC), a highly aggressive malignancy, is rapidly at an extensive stage once diagnosed and is one of the leading causes of death from malignancy. In the past decade, the treatment of SCLC has largely remained unchanged, and chemotherapy remains the cornerstone of SCLC treatment. The therapeutic value of adding immune checkpoint inhibitors to chemotherapy for SCLC is low, and only a few SCLC patients have shown a response to immune checkpoint inhibitors. Circulating tumor cells (CTCs) are tumor cells shed from solid tumor masses into the peripheral circulation and are key to tumor metastasis. Single-cell sequencing has revealed that the genetic profiles of individual CTCs are highly heterogeneous and contribute to the poor outcome and prognosis of SCLC patients. Theoretically, phenotypic analysis of CTCs may be able to predict the diagnostic significance of new potential targets for metastatic tumors. In this paper, we will discuss in depth the heterogeneity of CTCs in SCLC and the value of CTCs for the diagnosis and prognosis of SCLC and as relevant tumor markers in metastatic SCLC.

Crosstalk between Circulating Tumor Cells and Plasma Proteins-Impact on Coagulation and Anticoagulation

Cancer metastasis is a complex process. After their intravasation into the circulation, the cancer cells are exposed to a harsh environment of physical and biochemical hazards. Whether circulating tumor cells (CTCs) survive and escape from blood flow defines their ability to metastasize. CTCs sense their environment with surface-exposed receptors. The recognition of corresponding ligands, e.g., fibrinogen, by integrins can induce intracellular signaling processes driving CTCs' survival. Other receptors, such as tissue factor (TF), enable CTCs to induce coagulation. Cancer-associated thrombosis (CAT) is adversely connected to patients' outcome. However, cancer cells have also the ability to inhibit coagulation, e.g., through expressing thrombomodulin (TM) or heparan sulfate (HS), an activator of antithrombin (AT). To that extent, individual CTCs can interact with plasma proteins, and whether these interactions are connected to metastasis or clinical symptoms such as CAT is largely unknown. In the present review, we discuss the biological and clinical relevance of cancer-cell-expressed surface molecules and their interaction with plasma proteins. We aim to encourage future research to expand our knowledge of the CTC interactome, as this may not only yield new molecular markers improving liquid-biopsy-based diagnostics but also additional targets for better cancer therapies.

Bowel Preparation for Colonoscopy Changes Serum Composition as Detected by Thermal Liquid Biopsy and Fluorescence Spectroscopy

(1) Background: About 50% of prescribed colonoscopies report no pathological findings. A secondary screening test after fecal immunochemical test positivity (FIT+) would be required. Considering thermal liquid biopsy (TLB) as a potential secondary test, the aim of this work was to study possible interferences of colonoscopy bowel preparation on TLB outcome on a retrospective study; (2) Methods: Three groups were studied: 1/514 FIT(+) patients enrolled in a colorectal screening program (CN and CP with normal and pathological colonoscopy, respectively), with blood samples obtained just before colonoscopy and after bowel preparation; 2/55 patients from the CN group with blood sample redrawn after only standard 8-10 h fasting and no bowel preparation (CNR); and 3/55 blood donors from the biobank considered as a healthy control group; (3) Results: The results showed that from the 514 patients undergoing colonoscopy, 247 had CN and 267 had CP. TLB parameters in these two groups were similar but different from those of the blood donors. The resampled patients (with normal colonoscopy and no bowel preparation) had similar TLB parameters to those of the blood donors. TLB parameters together with fluorescence spectra and other serum indicators (albumin and C-reactive protein) confirmed the statistically significant differences between normal colonoscopy patients with and without bowel preparation; (4) Conclusions: Bowel preparation seemed to alter serum protein levels and altered TLB parameters (different from a healthy subject). The diagnostic capability of other liquid-biopsy-based methods might also be compromised. Blood extraction after bowel preparation for colonoscopy should be avoided.

High counting of circulating tumor cells in blood is not directly related to metastasis

Circulating tumor cells (CTCs) in blood flow have been believed as an essential biomarker of cancer. The technologies of in vitro and in vivo CTC enrichment and detection suggest although CTCs might play a role of "seed" in metastasis, only the minority of CTCs, probably in the form of CTC clusters, hold the potential to develop a tumor in organs. The detected amount of CTCs might be solely an indicator of tumor burden. To provide new insights into this argument, we take advantage of a safe drug to tune the pacemaker activity of a mouse tumor model to increase the heart rate for a period of time every day during the tumor development. We detect the CTCs in vivo by fast line scanning of a confocal microscope when the heart rate returns to the baseline and find the average CTC amount is significantly elevated in the drug-treated group but the metastases are even less than that of control. Our results imply the detected CTC counts in blood might not be directly related to metastasis.

Antibody mediated cotton-archetypal substrate for enumeration of circulating tumor cells and chemotherapy outcome in 3D tumors

Circulating tumor cells (CTCs) are distinct cancer biomarkers established in clinical settings for early cancer detection, metastasis progression, and minimal residual disease (MRD) monitoring. Despite numerous advances, the comprehensive molecular characterization of CTCs is extremely challenging owing to their rarity and heterogeneity. Here, we present a novel cotton microfluidic substrate (CMS) as an innovative biomedical matrix that efficiently isolates CTCs while facilitating in vitro CTC expansion to enable a further downstream analysis of these rare cells. CMS enabled static and dynamic isolation of cells from the MCF-7 cancer cell line, as well as from head and neck squamous cell carcinoma (HNSCC) patients' blood and the cell capture efficiencies were further compared with a clinically regulated OncoDiscover® Liquid Biopsy Test. Further, CMS acted as a matrix on which the captured cancer cells were grown in 3D tumor models for studying anti-cancer drug efficacy and multi-drug resistance (MDR) mechanisms. The design of the CMS employed two different surface chemistries, flattened and nanostructured surfaces, each conjugated to anti-EpCAM antibodies to evaluate the CTC capture efficiency and 3D tumor growth dynamics. The nanostructured surface was highly efficient for capturing CTCs and promoted 3D tumor spheroid formation with a 5-fold increase in size from day 03 to day 10 of culture. Moreover, when treated with an anti-cancer drug, cisplatin, an almost 1/2 reduction in tumor size was achieved within 24 hours, followed by a cytostatic threshold and eventual acquisition of drug resistance within 3 days. Conclusively, the CMS matrix exhibits potential for further development of "tissue on chip" and "point-of-care" medical devices in cancer diagnostics, and chemo-therapeutic efficacy evaluations in both drug discovery and development.

Clinical Applications of Circulating Tumour Cells and Circulating Tumour DNA in Non-Small Cell Lung Cancer-An Update

Despite efforts to improve earlier diagnosis of non-small cell lung cancer (NSCLC), most patients present with advanced stage disease, which is often associated with poor survival outcomes with only 15% surviving for 5 years from their diagnosis. Tumour tissue biopsy is the current mainstream for cancer diagnosis and prognosis in many parts of the world. However, due to tumour heterogeneity and accessibility issues, liquid biopsy is emerging as a game changer for both cancer diagnosis and prognosis. Liquid biopsy is the analysis of tumour-derived biomarkers in body fluids, which has remarkable advantages over the use of traditional tumour biopsy. Circulating tumour cells (CTCs) and circulating tumour DNA (ctDNA) are two main derivatives of liquid biopsy. CTC enumeration and molecular analysis enable monitoring of cancer progression, recurrence, and treatment response earlier than traditional biopsy through a minimally invasive liquid biopsy approach. CTC-derived ex-vivo cultures are essential to understanding CTC biology and their role in metastasis, provide a means for personalized drug testing, and guide treatment selection. Just like CTCs, ctDNA provides opportunity for screening, monitoring, treatment evaluation, and disease surveillance. We present an updated review highlighting the prognostic and therapeutic significance of CTCs and ctDNA in NSCLC.

Liquid Biopsy-Based Colorectal Cancer Screening via Surface Markers of Circulating Tumor Cells

Colorectal cancer (CRC) is ranked second for cancer-related deaths worldwide with approximately half of the patients being diagnosed at the late stages. The untimely detection of CRC results in advancement to the metastatic stage and nearly 90% of cancer-related deaths. The early detection of CRC is crucial to decrease its overall incidence and mortality rates. The recent introduction of circulating tumor cells (CTCs) has enabled a less invasive sampling method from liquid biopsies, besides revealing key information toward CRC metastasis. The current gold standard for CTC identification is the CellSearch® system (Veridex). This first-generation instrumentation relies on a single cell surface marker (CSM) to capture and count CTCs. Detection of CTCs allows the identification of patients at risk for metastasis, whereas CTC enumeration could improve risk assessment, monitoring of systemic therapy, and detection of therapy resistance in advanced metastatic CRC. In this review, we compared the pros and cons between single CSM-based CTC enrichment techniques and multi-marker-based systems. We also highlighted the challenges faced in the routine implementation of CSM-dependent CTC detection methods in CRC screening, prediction, prognosis, disease monitoring, and therapy selection toward precision medicine, as well as the dwelling on post-CTC analysis and characterization methods.

Capture, Detection, and Simultaneous Identification of Rare Circulating Tumor Cells Based on a Rhodamine 6G-Loaded Metal-Organic Framework

Circulating tumor cells (CTCs) play a key role in the development of tumor metastasis. It will be a big step forward for CTC application as a reliable clinical liquid biopsy marker to be able to identify the captured CTCs while achieving a high capture efficiency within one analytical system. Herein, in this work, a stimuli-responsive and rhodamine 6G (Rho 6G)-entrapped fluorescent metal-organic framework (MOF) probe, named MOF-Rho 6G-DNA, was designed to capture, detect, and subsequently identify CTCs from blood samples of cancer patients. The probe was fabricated by modifying the epithelial cell adhesion molecule (EpCAM) hairpin DNA aptamer with Rho 6G enclosed and an Arm-DNA-attached UiO-66-NH2 MOF by sequence complementation. CTCs could be captured by the EpCAM hairpin DNA on the probe; as a result, Rho 6G loaded in the probe was released, and the number of CTCs was positively related to the concentration of released Rho 6G. An excellent correlation of fluorescence intensities with CTC numbers was obtained from 2 to 500 cells/mL. More importantly, the MOF-Rho 6G-DNA probe simultaneously realized rapid identification of the captured cells within 30 min by only relying on the residue Rho 6G in the MOF cavity. The captured target cells can be conveniently released from the probe using the complementary DNA sequence. These performance features of the probe were further verified by blood samples from patients of various types of tumor.

A higher platelet-to-lymphocyte ratio is prevalent in the presence of circulating tumor microemboli and is a potential prognostic factor for non-metastatic colon cancer

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A high platelet-to-lymphocyte ratio (PLR; >124) before curative surgical resection was found to be associated with reduced disease-free survival (DFS) in non-metastatic colon cancer patients.

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A high PLR was predominant among patients with circulating tumor microemboli (CTM).

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This prospective study revealed a mechanism of interaction between circulating tumor cells (CTCs) and other blood components, and implicated platelets in CTC survival.

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The present findings support the use of blood biomarkers to better identify and follow high-risk colon cancer patients.

Colorectal cancer is a common and often deadly cancer. Circulating tumor cells (CTCs) have been implicated as a potentially valuable prognosis factor. The detection of circulating tumor microemboli (CTM) and of simple blood component parameters that reflect inflammatory status, such as the platelet-to-lymphocyte ratio (PLR) and neutrophil-to-lymphocyte ratio (NLR), may provide information about tumor progression. The aim of this study was to explore the importance of CTCs, CTM, PLR, and NLR prospectively in non-metastatic colon cancer progression. CTCs were enriched using ISET^Ⓡ (Isolation by SizE of Tumor cells) and identified by immunocytochemical exclusion of leukocytes. We evaluated CTCs and blood cell parameters in a cohort of 69 stage I–III colon cancer patients (52.2% men; median age, 61 years; age range, 19–87 years) at a baseline timepoint prior to resection surgery. The median of CTC levels at baseline was 20 cells/8 mL (0–94) and higher levels were associated with CTM presence (p = 0.02). CTM were found in 18 (26.1%) patients. Of 18 stage I patients, 33.3% had CTM and of 51 stages II or III patients, 13.7% had CTM (p = 0.08). Patients with a high PLR (>124) were mostly (75.6%) diagnosed with high-risk stages II/III cancer (stages I/low-risk II, 24.4%; p = 0.014). All 8 patients that had disease recurrence during follow-up had a high PLR (p = 0.02 vs. low PLR). NLR was not significantly associated with disease stage or recurrence. The present results indicate that CTCs and PLR analyses may be clinically useful for colon cancer management and risk stratification.

Metastasis: A Bane of Breast Cancer Therapy

The underlying mechanisms of metastasis in patients with breast cancer is still poorly understood. Approximately 6% of patients with breast cancer present with metastasis at the time of diagnosis. Metastatic breast cancer is difficult to treat and patients with breast cancer with distant metastasis have a significantly lower 5-year survival rate compared to patients with localised breast cancer (27% and 99%, respectively). During breast cancer progression, tumour cells first metastasise to nearby draining lymph nodes and then to distant organs, primarily bone, lungs, liver, and brain. In this brief review, the authors discuss breast cancer metastasis, the role of epithelial–mesenchymal transition and the contributions of the immune system to the metastatic process. The authors also briefly discuss whether there is any relationship between tumour size and metastatic potential, and recent advances in treatment for metastatic breast cancer. The studies highlighted suggest that immunotherapy may play a more significant role in future patient care for metastatic breast cancer.

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

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

The Liquid Biopsy in the Management of Colorectal Cancer: An Overview

Currently, there is a crucial need for novel diagnostic and prognostic biomarkers with high specificity and sensitivity in patients with colorectal cancer. A "liquid biopsy" is characterized by the isolation of cancer-derived components, such as circulating tumor cells, circulating tumor DNA, microRNAs, long non-coding RNAs, and proteins, from peripheral blood or other body fluids and their genomic or proteomic assessment. The liquid biopsy is a minimally invasive and repeatable technique that could play a significant role in screening and diagnosis, and predict relapse and metastasis, as well as monitoring minimal residual disease and chemotherapy resistance in colorectal cancer patients. However, there are still some practical issues that need to be addressed before liquid biopsy can be widely used in clinical practice. Potential challenges may include low amounts of circulating tumor cells and circulating tumor DNA in samples, lack of pre-analytical and analytical consensus, clinical validation, and regulatory endorsement. The aim of this review was to summarize the current knowledge of the role of liquid biopsy in the management of colorectal cancer.

Liquid Biopsies to Select Patients for Perioperative Chemotherapy in Muscle-invasive Bladder Cancer: A Systematic Review

CONTEXT

Neoadjuvant chemotherapy (NAC) is considered the standard treatment for muscle-invasive bladder cancer (MIBC). However, its overall survival benefit is limited and toxicity is significant; hence, NAC has not been adopted universally.

OBJECTIVE

To systematically evaluate whether biomarkers can guide the administration of perioperative chemotherapy in MIBC patients.

EVIDENCE ACQUISITION

A systematic search of the PubMed database was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA). In total, 215 papers were screened and 22 were selected to assess the potential clinical value of circulating tumor cells (CTCs) and cell-free DNA (cfDNA) in selecting MIBC patients for perioperative chemotherapy.

EVIDENCE SYNTHESIS

We found that the presence of one or more CTCs before radical cystectomy, as determined by the CellSearch technique, is a robust marker for poor recurrence-free and overall survival. Consequently, whether NAC can be withheld in patients without the presence of CTCs is a subject of ongoing investigation. Studies investigating various approaches to detect cfDNA showed that cfDNA is present in the blood of MIBC patients, but varying results on its prognostic value have been reported. Successful cfDNA-based approaches are likely to encompass at least a multitude of genes using next-generation sequencing, as there are generally few hotspot somatic mutations in MIBC.

CONCLUSIONS

Liquid biopsies hold promise in selecting MIBC patients for perioperative chemotherapy, but instead of more proof-of-principle studies, prospective studies investigating true clinical applicability for treatment decision making are urgently needed.

PATIENT SUMMARY

Liquid biopsies appear to be a promising tool to guide the administration of chemotherapy in patients with muscle-invasive bladder cancer; however, the optimal way to implement these remains to be determined.

Engineering State-of-the-Art Plasmonic Nanomaterials for SERS-Based Clinical Liquid Biopsy Applications

Precision oncology, defined as the use of the molecular understanding of cancer to implement personalized patient treatment, is currently at the heart of revolutionizing oncology practice. Due to the need for repeated molecular tumor analyses in facilitating precision oncology, liquid biopsies, which involve the detection of noninvasive cancer biomarkers in circulation, may be a critical key. Yet, existing liquid biopsy analysis technologies are still undergoing an evolution to address the challenges of analyzing trace quantities of circulating tumor biomarkers reliably and cost effectively. Consequently, the recent emergence of cutting-edge plasmonic nanomaterials represents a paradigm shift in harnessing the unique merits of surface-enhanced Raman scattering (SERS) biosensing platforms for clinical liquid biopsy applications. Herein, an expansive review on the design/synthesis of a new generation of diverse plasmonic nanomaterials, and an updated evaluation of their demonstrated SERS-based uses in liquid biopsies, such as circulating tumor cells, tumor-derived extracellular vesicles, as well as circulating cancer proteins, and tumor nucleic acids is presented. Existing challenges impeding the clinical translation of plasmonic nanomaterials for SERS-based liquid biopsy applications are also identified, and outlooks and insights into advancing this rapidly growing field for practical patient use are provided.

Cooperative and Escaping Mechanisms between Circulating Tumor Cells and Blood Constituents

Metastasis is the leading cause of cancer-related deaths and despite measurable progress in the field, underlying mechanisms are still not fully understood. Circulating tumor cells (CTCs) disseminate within the bloodstream, where most of them die due to the attack of the immune system. On the other hand, recent evidence shows active interactions between CTCs and platelets, myeloid cells, macrophages, neutrophils, and other hematopoietic cells that secrete immunosuppressive cytokines, which aid CTCs to evade the immune system and enable metastasis. Platelets, for instance, regulate inflammation, recruit neutrophils, and cause fibrin clots, which may protect CTCs from the attack of Natural Killer cells or macrophages and facilitate extravasation. Recently, a correlation between the commensal microbiota and the inflammatory/immune tone of the organism has been stablished. Thus, the microbiota may affect the development of cancer-promoting conditions. Furthermore, CTCs may suffer phenotypic changes, as those caused by the epithelial–mesenchymal transition, that also contribute to the immune escape and resistance to immunotherapy. In this review, we discuss the findings regarding the collaborative biological events among CTCs, immune cells, and microbiome associated to immune escape and metastatic progression.

Identification of plasma exosomes long non-coding RNA HAGLR and circulating tumor cells as potential prognosis biomarkers in non-small cell lung cancer

Background

The main purpose of this study was to identify the correlation between the expression of long non-coding RNA (lncRNA) HAGLR in plasma exosomes and the detection rate of circulating tumor cells (CTCs) in patients with non-small cell lung cancer (NSCLC).

Methods

LncRNA HAGLR expression was detected in plasma exosomes of 40 patients with NSCLC and 8 healthy subjects using qRT-PCR. CTCs were enriched and separated using CTC-BIOPSY^® abnormal cell separator. The correlations between lncRNA HAGLR expression in plasma exosomes and CTCs of patients with NSCLC and clinical pathological parameters were also analyzed. Bioinformatics analyses indicated HAGLR was evidently down-regulated in NSCLC tissues when compared to normal controls. The relationship between differential expression of HAGLR with different stages of NSCLC and clinical prognosis were elucidated using corresponding statistical methods.

Results

HAGLR was significantly decreased in NSCLC, and there was obvious correlation with overall survival (P<0.05). CTCs were detected in peripheral blood of patients with NSCLC with the positive rate of 70.0%. In lung squamous cell carcinoma (LUSC), compared with the high expression group of HAGLR, the low expression group had a better overall survival (P<0.05). At the same time, the high expression of HAGLR was positively correlated with the high detection rate of CTCs (P<0.05), suggesting that the disease may have a later tumor stage, and poor prognosis.

Conclusions

lncRNA HAGLR and CTCs could be used as potential biomarkers for NSCLC metastasis risk prediction.