Plasticity of disseminating cancer cells in patients with epithelial malignancies

EpCAM Signaling in Oral Cancer Stem Cells: Implications for Metastasis, Tumorigenicity, and Therapeutic Strategies

Oral cancer, a subtype of head and neck cancer, poses significant global health challenges owing to its late diagnosis and high metastatic potential. The epithelial cell adhesion molecule (EpCAM), a transmembrane glycoprotein, has emerged as a critical player in cancer biology, particularly in oral cancer stem cells (CSCs). This review highlights the multifaceted roles of EPCAM in regulating oral cancer metastasis, tumorigenicity, and resistance to therapy. EpCAM influences key pathways, including Wnt/β-catenin and EGFR, modulating CSC self-renewal, epithelial-to-mesenchymal transition (EMT), and immune evasion. Moreover, EpCAM has been implicated in metabolic reprogramming, epigenetic regulation, and crosstalk with other signaling pathways. Advances in EpCAM-targeting strategies, such as monoclonal antibodies, chimeric antigen receptor (CAR) T/NK cell therapies, and aptamer-based systems hold promise for personalized cancer therapies. However, challenges remain in understanding the precise mechanism of EpCAM in CSC biology and its translation into clinical applications. This review highlights the need for further investigation into the role of EPCAM in oral CSCs and its potential as a therapeutic target to improve patient outcomes.

Enhanced detection of circulating tumor cells using a MUC1 promoter-driven recombinant adenovirus

Introduction

Circulating tumor cells (CTCs) have attracted significant interest as a biomarker for cancer diagnosis. In this study, we judiciously constructed a recombinant MUC1-dependent adenovirus (rAdF35-MUC1) that can selectively replicate and overexpress copepod super green fluorescent proteins (copGFP) in MUC1-positive tumor cells to investigate its role in the detection of CTCs.

Methods

We conducted a comparative study between rAdF35-MUC1 and the existing hTERT-dependent adenovirus (rAdF35-hTERT). Breast cancer cell lines and healthy human peripheral blood mononuclear cells (PBMCs) were infected with both viral constructs to evaluate infection efficiency and the incidence of false-positive cells. CTC Model Samples were employed to determine detection rates, and clinical samples from breast cancer patients were analyzed to preliminarily evaluate the efficacy of CTC detection in a clinical context.

Results

In preclinical and clinical studies, rAdF35-MUC1 exhibited a significantly high detection efficiency for breast cancer cells, outperforming the existing hTERT-dependent adenovirus (rAdF35-hTERT), especially in detecting CTCs at low quantities. Moreover, rAdF35-MUC1 demonstrated reduced incidence of false positives in healthy PBMCs compared to rAdF35-hTERT.

Conclusion

In brief, rAdF35-MUC1 emerges as a potent tool for the sensitive and specific identification of CTCs derived from breast cancer patients, holding clinical translation potential for advancing cancer (early) diagnosis, treatment monitoring, and prognosis.

Measurable morphological features of single circulating tumor cells in selected solid tumors-A pilot study

Liquid biopsies developed into a range of sensitive technologies aiming to analyze for example, circulating tumor cells (CTCs) in peripheral blood, which significantly deepens understanding of the metastatic process. Nevertheless, examination of CTCs is mostly limited to their enumeration and usually only 2-3 markers-based phenotyping, not offering yet sufficient insight into their biology. In contrast, quantitative analysis of their morphological details might extend our knowledge about dissemination and even improve CTC isolation or label-free identification methods dependent on their physical features such as size, and deformability. Current study was conducted to describe CTCs' and their size, shape, presence of protrusions, and micronuclei across various types of cancers (lung, n = 29; ovarian, n = 24, breast, n = 54; and prostate, n = 33). Epithelial (pan-keratins), mesenchymal (vimentin), and two exclusion markers were used to identify CTCs and classify them into four epithelial and epithelial-mesenchymal transition-related phenotypes using standardized and throughput method, imaging flow cytometry. The morphological characteristics of CTCs, including their nuclei, such as circularity, the maximum, and minimum diagonal values were determined using an open-source software QuPath. On average, detected CTCs (n = 1156) were larger, and more irregular in shape compared to leukocytes/endothelial cells (n = 400). Epithelial and mesenchymal CTCs had the largest (median = 18.2 μm) and the smallest diameter (median = 10.4 μm), respectively. In terms of cancer-specific variations, the largest CTCs were identified in lung cancer, whereas the smallest-in prostate and breast cancers. Epithelial CTCs and those negative for both epithelial and mesenchymal markers exhibited the highest degree of elongation, whereas mesenchymal CTCs were the most irregular in shape. Protrusions and micronuclei were observed extremely rarely within CTCs of breast and prostate cancer (0.6%-0.8% of CTCs). Micronuclei were observed only in epithelial and epithelial-mesenchymal CTCs. This study underscores the significant variability in the morphological features of CTCs in relation to their phenotypic classification or even the particular organ of origin, potentially influencing for example, size-dependent CTC isolation methods. It demonstrates for the first time the morphological measurements of CTCs undergoing epithelial-mesenchymal transition, and some specific morphological details (i.e., protrusions, micronuclei) within CTCs in general.

Knowledge-map and research trends of circulating tumor cells in breast cancer: a scientometric analysis

Assessing circulating tumor cells (CTCs) in early-stage breast cancer patients can help identify relapse risk for timely interventions. Molecular analysis of CTCs can reveal vulnerabilities for personalized treatment options in metastatic breast cancer. This study aims to summarize CTCs in breast cancer research understanding and evaluate research trends. Extracted from the Web of Science Core Collection, publications on CTCs in breast cancer studies spanning from January 1, 2008, to December 21, 2023, were included. Co-authorships, references, and keywords were analyzed using Bibliometrix R packages and VOSviewer software. References and keywords burst detection were conducted with CiteSpace, and BICOMB was utilized to generate high-frequency keyword layouts. Biclustering analysis of the binary co-keyword matrix was performed using gCLUTO. 1747 articles focusing on CTCs in breast cancer were identified. The USA and the University of Texas MD Anderson Cancer Center demonstrated the highest productivity at the national and institutional levels, respectively. The journal "CANCERS" had the highest publication outputs on this subject. Pantel K emerged as the foremost author with the highest publication and co-citation counts. Analysis of co-keywords unveiled five prominent research areas concerning CTCs in breast cancer. The prognostic and predictive roles of CTCs in breast cancer have substantial implications for clinical practice. Nevertheless, precise assessment of CTCs, encompassing its quantities and attributes through advanced technologies, and its role in detecting minimal residual disease in breast cancer, continue to pose notable challenges. In conclusion, recent advancements and trends in CTCs research in breast cancer are examined through scientometric analysis in this study. The results provide valuable insights for the formulation of novel approaches in CTCs research, emphasizing the current research frontiers.

Mesenchymal Stromal Cells Increase the Natural Killer Resistance of Circulating Tumor Cells via Intercellular Signaling of cGAS-STING-IFNβ-HLA

Circulating tumor cells (CTCs) shed from primary tumors must overcome the cytotoxicity of immune cells, particularly natural killer (NK) cells, to cause metastasis. The tumor microenvironment (TME) protects tumor cells from the cytotoxicity of immune cells, which is partially executed by cancer-associated mesenchymal stromal cells (MSCs). However, the mechanisms by which MSCs influence the NK resistance of CTCs remain poorly understood. This study demonstrates that MSCs enhance the NK resistance of cancer cells in a gap junction-dependent manner, thereby promoting the survival and metastatic seeding of CTCs in immunocompromised mice. Tumor cells crosstalk with MSCs through an intercellular cGAS-cGAMP-STING signaling loop, leading to increased production of interferon-β (IFNβ) by MSCs. IFNβ reversely enhances the type I IFN (IFN-I) signaling in tumor cells and hence the expression of human leukocyte antigen class I (HLA-I) on the cell surface, protecting the tumor cells from NK cytotoxicity. Disruption of this loop reverses NK sensitivity in tumor cells and decreases tumor metastasis. Moreover, there are positive correlations between IFN-I signaling, HLA-I expression, and NK tolerance in human tumor samples. Thus, the NK-resistant signaling loop between tumor cells and MSCs may serve as a novel therapeutic target.

Presence of CD44v9-Expressing Cancer Stem Cells in Circulating Tumor Cells and Effects of Carcinoembryonic Antigen Levels on the Prognosis of Colorectal Cancer

Circulating tumor cells (CTCs) are cancer cells released from the primary tumor into the bloodstream, and contain cancer stem cells that influence tumor survival, recurrence, and metastasis. Here, we investigated CD44v9 expression in CTCs and impact of preoperative carcinoembryonic antigen (CEA) levels on colorectal cancer (CRC) prognosis. We analyzed the expression of CD44v9 mRNA in CTCs using reverse transcription-polymerase chain reaction and preoperative CEA levels in blood samples obtained from 300 patients with CRC. Subsequently, we evaluated the association of CD44v9 expression and CEA levels with clinicopathological factors. CD44v9 mRNA was expressed in 31.3% of the patients, and was significantly associated with liver metastasis. Patients with positive CD44v9 expression had a lower 5-year survival rate (62.3%) than those with negative CD44v9 expression (82.8%, p < 0.001). Cox regression analysis identified CD44v9 expression and high CEA levels (≥5 ng/mL) as poor prognostic factors, while negative CD44v9 expression and low CEA levels (<5 ng/mL) were associated with favorable prognosis (hazard ratio = 0.285, p = 0.006). These results suggest that a combination of CD44v9 mRNA expression in CTCs and serum CEA levels could serve as a valuable prognostic marker for CRC, potentially enhancing the accuracy of prognosis predictions.

Microfluidic Isolation of Disseminated Tumor Cells from the Bone Marrow of Breast Cancer Patients

Disseminated tumor cells (DTCs) in the bone marrow (BM) of breast cancer (BC) patients are putative precursors of metastatic disease, and their presence is associated with an adverse clinical outcome. To achieve the personalization of therapy on a clinical routine level, the characterization of DTCs and in vitro drug testing on DTCs are of great interest. Therefore, biobanking methods, as well as novel approaches to DTC isolation, need to be developed. In this study, we established a protocol for the biobanking of BM samples and evaluated a microfluidic-based separation system (Parsortix®) for the enrichment of cryopreserved DTCs. We were able to successfully isolate viable DTCs after the prior cryopreservation of BM samples. We calculated a significant increase of up to 90-fold in harvested DTCs with the proposed method compared to the current standard techniques, opening up new analysis possibilities for DTCs. Our advanced method further presents options for 3D DTC cultures, enabling the individualized testing of targeted therapies for BC patients. In conclusion, we present a novel approach for DTC enrichment, with possibilities for future clinical implications.

Transición epitelio – mesenquima y cáncer

Cancer cell migration and invasion are critical components of metastatic disease, the leading cause of death in cancer patients. The epithe-lium-mesenchyme-transition (EMT) and mesenchyme-epithelium-transition (MET) are pathways involved in cancer metastasis. This process involves the degradation of cell-cell and cell-extracellular matrix junctions and the subse-quent loss of regulation of binding proteins such as E-cadherin. Cells undergo a reorganization of the cytoskeleton. These alterations are associated with a change in cell shape from epithelial to mesenchymal morphology. Understand-ing EMT and MET’s molecular and cellular basis provides fundamental insights into cancer etiology and may lead to new therapeutic strategies. In this review, we discuss some of the regulatory mechanisms and pathological role of epitheli-al-mesenchymal plasticity, focusing on the knowledge about the complexity and dynamics of this phenomenon in cancer

Improved Characterization of Circulating Tumor Cells and Cancer-Associated Fibroblasts in One-Tube Assay in Breast Cancer Patients Using Imaging Flow Cytometry

Circulating tumor cells (CTCs) and circulating cancer-associated fibroblasts (cCAFs) have been individually considered strong indicators of cancer progression. However, technical limitations have prevented their simultaneous analysis in the context of CTC phenotypes different from epithelial. This study aimed to analyze CTCs and cCAFs simultaneously in the peripheral blood of 210 breast cancer patients using DAPI/pan-keratin (K)/vimentin (V)/alpha-SMA/CD29/CD45/CD31 immunofluorescent staining and novel technology-imaging flow cytometry (imFC). Single and clustered CTCs of different sizes and phenotypes (i.e., epithelial phenotype K+/V- and epithelial-mesenchymal transition (EMT)-related CTCs, such as K+/V+, K-/V+, and K-/V-) were detected in 27.6% of the samples and correlated with metastases. EMT-related CTCs interacted more frequently with normal cells and tended to occur in patients with tumors progressing during therapy, while cCAFs coincided with CTCs (mainly K+/V- and K-/V-) in seven (3.3%) patients and seemed to correlate with the presence of metastases, particularly visceral ones. This study emphasizes the advantages of imFC in the field of liquid biopsy and highlights the importance of multimarker-based analysis of different subpopulations and phenotypes of cancer progression-related cells, i.e., CTCs and cCAFs. The co-detection of CTCs and cCAFs might improve the identification of patients at higher risk of progression and their monitoring during therapy.

The Role of Liquid Biopsy in the Diagnosis and Prognosis of WHO Grade 4 Astrocytoma

Liquid biopsy, as a non-invasive diagnostic tool, has recently gained significant attention in the field of oncology. It involves the analysis of various biomarkers present in bodily fluids, such as blood or cerebrospinal fluid, to provide information about the underlying cancer. In the case of WHO grade 4 astrocytomas, liquid biopsy has the potential to significantly impact the diagnosis and prognosis of this aggressive malignant brain tumor. By detecting specific genetic mutations, such as IDH1 or EGFR, and monitoring levels of circulating tumor DNA, liquid biopsy can aid in the early detection and monitoring of disease progression. This innovative approach is gradually being acknowledged as a less invasive and cost-effective procedure for cancer diagnosis and management to improve patient outcomes and quality of life. Various kinds of biomarkers circulating in cerebrospinal fluid (CSF), such as circulating tumor cells (CTC) and different types of nucleic acids like cell-free DNA (cfDNA), cell-free RNA (ctRNA), and microRNAs (miRNA), have been identified. These biomarkers, which require dependable detection methods, are comparatively simple to obtain and allow for repeated measurements, making them significantly superior for disease monitoring. This review aims to compare the latest liquid biopsy analysis tools for both CSF and plasma in the central nervous system.

Cyclin-dependent kinase subunit2 (CKS2) promotes malignant phenotypes and epithelial-mesenchymal transition-like process in glioma by activating TGFβ/SMAD signaling

BACKGROUND

Gliomas are a group of primary intracranial tumors with high morbidity and mortality. The previous researches indicated a crucial role of CKS2 (cyclin-dependent kinases regulatory subunit 2) in hepatocellular carcinoma and breast cancer; however, little is known about the molecular mechanism of CKS2 in the tumorigenesis and epithelial-mesenchymal transition-like (EMT) process in glioma.

METHODS

Datasets for bioinformatics analysis were obtained from the GEO, TCGA and CGGA databases. qRT-PCR, western blotting (WB), and immunohistochemistry (IHC) assays were used to investigate the expression patterns of CKS2 among glioma and brain tissues. Glioma cells were transfected with small interfering RNA/overexpression plasmid against CKS2, then clone formation assay, CCK-8, wound healing, Transwell assay, and flow cytometry were performed to detect changes in cell viability, invasiveness, and the apoptosis rate. Markers of cell invasion, apoptosis, EMT and TGFβ/SMAD signaling were evaluated by WB and immunofluorescence (IF) assays.

RESULTS

We found that CKS2 overexpression correlates with poor prognosis in human glioma and knockdown of CKS2 could inhibit cell proliferation, migration, invasion, and induced apoptosis in glioma cells. Besides, we also found that knockdown of CKS2 could reverse the EMT process via modulating EMT-related molecules. Glioma cells with overexpression of CKS2 were constructed to confirmed the fact that CKS2 induced nucleocytoplasmic translocation of SMAD2/3 and activated TGFβ/SMAD pathway, then upregulated its downstream targets expression, while inhibition of TGFβ/SMAD (by TGFβ inhibitor LY2157299 or SMAD4 siRNA) could reverse the tumor-promoting effects and malignant phenotype caused by CKS2 overexpression.

CONCLUSIONS

We identified CKS2 as a critical contributor to the gliomagenesis, which might provide a novel therapeutic target for inhibiting the spread and infiltration of glioma.

Aneuploid subtypes of circulating tumor cells and circulating tumor-derived endothelial cells predict the overall survival of advanced lung cancer

Objective

This study aimed to detect circulating tumor cells (CTCs) and circulating tumor-derived endothelial cells (CTECs) in patients with advanced lung cancer, for describing the distribution characteristics of CTC and CTEC subtypes, exploring the correlation between CTC/CTEC subtypes and novel prognostic biomarkers.

Methods

A total of 52 patients with advanced lung cancer were enrolled in this study. Using the subtraction enrichment-immunofluorescence in situ hybridization (SE-iFISH) system, CTCs and CTECs derived from these patients were identified.

Results

Based on cell size, there were 49.3% small and 50.7% large CTCs, and 23.0% small and 77.0% large CTECs. Triploidy, tetraploidy, and multiploidy varied in the small and large CTCs/CTECs. Besides these three aneuploid subtypes, monoploidy was found in the small and large CTECs. Triploid and multiploid small CTCs and tetraploid large CTCs were associated with shorter overall survival (OS) in patients with advanced lung cancer. However, none of the CTECs subtypes showed a significant correlation with patient prognosis. In addition, we found strong positive correlations (P<0.0001) in the four groups including triploid small cell size CTCs and multiploid small cell size CTECs, and multiploid small cell size CTCs and monoploid small cell size CTECs. Furthermore, combined detection of the specific subtypes, including triploid small CTC and monoploid small CTEC, triploid small CTC and triploid small CTEC, and multiploid small CTC and monoploid small CTEC, were associated with poor prognosis in advanced lung cancer.

Conclusions

Aneuploid small CTCs are associated with the outcome of patients with advanced lung cancer. In particular, the combined detection of triploid small CTCs and monoploid small CTECs, triploid small CTCs and triploid small CTECs, and multiploid small CTCs and monoploid small CTECs has clinical significance for predicting prognosis in patients with advanced lung cancer.

LACTB, a Metabolic Therapeutic Target in Clinical Cancer Application

Serine beta-lactamase-like protein (LACTB) is the only mammalian mitochondrial homolog evolved from penicillin-binding proteins and β-lactamases (PBP-βLs) in bacteria. LACTB, an active-site serine protease, polymerizes into stable filaments, which are localized to the intermembrane space (IMS) of mitochondrion and involved in the submitochondrial organization, modulating mitochondrial lipid metabolism. Cancer pathogenesis and progression are relevant to the alterations in mitochondrial metabolism. Metabolic reprogramming contributes to cancer cell behavior. This article (1) evidences the clinical implications of LACTB on neoplastic cell proliferation and migration and tumor growth and metastasis as well as LACTB’s involvement in chemotherapeutic and immunotherapeutic responses; (2) sketches the structural basis for LACTB activity and function; and (3) highlights the relevant regulatory mechanisms to LACTB. The abnormal expression of LACTB has been associated with clinicopathological features of cancer tissues and outcomes of anticancer therapies. With the current pioneer researches on the tumor-suppressed function, structural basis, and regulatory mechanism of LACTB, the perspective hints at a great appeal of enzymic property, polymerization, mutation, and epigenetic and post-translational modifications in investigating LACTB’s role in cancer pathogenesis. This perspective provides novel insights for LACTB as a metabolic regulator with potential to develop targeted cancer therapies or neoadjuvant therapeutic interventions.

Detection and Characterization of Circulating Tumor Cells Using Imaging Flow Cytometry—A Perspective Study

Simple Summary

Liquid biopsy is non-invasive approach used to prognose and monitor tumor progression based on the detection and examination of metastasis-related events found in the patients’ blood (such as circulating tumor cells (CTCs), extracellular vesicles, and circulating nucleic acids). Different ultrasensitive techniques are applied to study those events and the biology of tumor dissemination, which in the future might complement standard diagnostics. Here, we suggest that CTCs analysis could be improved by the usage of imaging flow cytometry, combining advantages of both standard flow cytometry (high-scale analysis) and microscopy (high resolution) to investigate detailed features of those cells. From this perspective, we discuss the potential of this technology in the CTC field and present representative images of CTCs from breast and prostate cancer patients analyzed with this method.

Abstract

Tumor dissemination is one of the most-investigated steps of tumor progression, which in recent decades led to the rapid development of liquid biopsy aiming to analyze circulating tumor cells (CTCs), extracellular vesicles (EVs), and circulating nucleic acids in order to precisely diagnose and monitor cancer patients. Flow cytometry was considered as a method to detect CTCs; however, due to the lack of verification of the investigated cells’ identity, this method failed to reach clinical utility. Meanwhile, imaging flow cytometry combining the sensitivity and high throughput of flow cytometry and image-based detailed analysis through a high-resolution microscope might open a new avenue in CTC technologies and provide an open-platform system alternative to CellSearch^®, which is still the only gold standard in this field. Hereby, we shortly review the studies on the usage of flow cytometry in CTC identification and present our own representative images of CTCs envisioned by imaging flow cytometry providing rationale that this novel technology might be a good tool for studying tumor dissemination, and, if combined with a high CTC yield enrichment method, could upgrade CTC-based diagnostics.

Label-free enrichment of MCF7 breast cancer cells from leukocytes using continuous flow dielectrophoresis

Circulating tumor cells (CTCs) present in the bloodstream are strongly linked to the invasive behavior of cancer; therefore, their detection holds great significance for monitoring disease progression. Currently available CTC isolation tools are often based on tumor-specific antigen or cell size approaches. However, these techniques are limited due to the lack of a unique and universal marker for CTCs, and the overlapping size between CTCs and regular blood cells. Dielectrophoresis (DEP), governed by the intrinsic dielectric properties of the particles, is a promising marker-free, accurate, fast, and low-cost technique that enables the isolation of CTCs from blood cells. This study presents a continuous flow, antibody-free DEP-based microfluidic device to concentrate MCF7 breast cancer cells, a well-established CTC model, in the presence of leukocytes extracted from human blood samples. The enrichment strategy was determined according to the DEP responses of the corresponding cells, obtained in our previously reported DEP spectrum study. It was based on the positive-DEP integrated with hydrodynamic focusing under continuous flow. In the proposed device, the parylene microchannel with two inlets and outlets was built on top of rectangular and equally spaced isolated planar electrodes rotated certain degree relative to the main flow (13°). The recovery of MCF7 cells mixed with leukocytes was 74%-98% at a frequency of 1 MHz and a magnitude of 10-12 V_pp . Overall, the results revealed that the presented system successfully concentrates MCF7 cancer cells from leukocytes, ultimately verifying our DEP spectrum study, in which the enrichment frequency and separation strategy of the microfluidic system were determined.

Fusobacterium nucleatum: a new player in regulation of cancer development and therapeutic response

A dysbiosis in microbial diversity or functionality can promote disease development. Emerging preclinical and clinical evidence emphasizes the interplay between microbiota and both disease evolution and the treatment response of different cancers. One bacterium that has garnered much attention in a few cancer microbiota studies is Fusobacterium nucleaum (Fn). To provide updated knowledge of the functional role of Fn in cancer prevention and management, this review summarizes the relationship among Fn, cancer, and chemoimmunotherapy response, with the potential mechanisms of action also intensively discussed, which will benefit the development of strategies to prevent or treat cancer via Fn-based therapeutic interventions.

Circulating Tumour Cells Indicate the Presence of Residual Disease Post-Castration in Prostate Cancer Patient-Derived Xenograft Models

Castrate-resistant prostate cancer (CRPC) is the lethal form of prostate cancer. Epithelial mesenchymal plasticity (EMP) has been associated with disease progression to CRPC, and prostate cancer therapies targeting the androgen signalling axis, including androgen deprivation therapy (ADT), promote EMP. We explored effects of castration on EMP in the tumours and circulating tumour cells (CTCs) of patient-derived xenograft (PDX)-bearing castrated mice using human-specific RT-qPCR assays and immunocytochemistry. Expression of prostate epithelial cell marker KLK3 was below detection in most tumours from castrated mice (62%, 23/37 mice), consistent with its known up-regulation by androgens. Endpoint tumour size after castration varied significantly in a PDX model-specific pattern; while most tumours were castration-sensitive (BM18, LuCaP70), the majority of LuCaP105 tumours continued to grow following castration. By contrast, LuCaP96 PDX showed a mixed response to castration. CTCs were detected in 33% of LuCaP105, 43% of BM18, 47% of LuCaP70, and 54% of LuCaP96 castrated mice using RPL32 mRNA measurement in plasma. When present, CTC numbers estimated using human RPL32 expression ranged from 1 to 458 CTCs per ml blood, similar to our previous observations in non-castrated mice. In contrast to their non-castrated counterparts, there was no relationship between tumour size and CTC burden in castrated mice. Unsupervised hierarchical clustering of the gene expression profiles of CTCs collected from castrated and non-castrated mice revealed distinct CTC sub-groups within the pooled population that were classified as having mesenchymal, epithelial, or EMP hybrid gene expression profiles. The epithelial signature was only found in CTCs from non-castrated mice. Hybrid and mesenchymal signatures were detected in CTCs from both castrated and non-castrated mice, with an emphasis towards mesenchymal phenotypes in castrated mice. Post-castration serum PSA levels were either below detection or very low for all the CTC positive samples highlighting the potential usefulness of CTCs for disease monitoring after androgen ablation therapy. In summary, our study of castration effects on prostate cancer PDX CTCs showed that CTCs were often detected in the castrate setting, even in mice with no palpable tumours, and demonstrated the superior ability of CTCs to reveal residual disease over the conventional clinical biomarker serum PSA.

Circulating tumour cells in the -omics era: how far are we from achieving the 'singularity'?

Over the past decade, cancer diagnosis has expanded to include liquid biopsies in addition to tissue biopsies. Liquid biopsies can result in earlier and more accurate diagnosis and more effective monitoring of disease progression than tissue biopsies as samples can be collected frequently. Because of these advantages, liquid biopsies are now used extensively in clinical care. Liquid biopsy samples are analysed for circulating tumour cells (CTCs), cell-free DNA, RNA, proteins and exosomes. CTCs originate from the tumour, play crucial roles in metastasis and carry information on tumour heterogeneity. Multiple single-cell omics approaches allow the characterisation of the molecular makeup of CTCs. It has become evident that CTCs are robust biomarkers for predicting therapy response, clinical development of metastasis and disease progression. This review describes CTC biology, molecular heterogeneity within CTCs and the involvement of EMT in CTC dynamics. In addition, we describe the single-cell multi-omics technologies that have provided insights into the molecular features within therapy-resistant and metastasis-prone CTC populations. Functional studies coupled with integrated multi-omics analyses have the potential to identify therapies that can intervene the functions of CTCs.

Liquid Biopsy and Artificial Intelligence as Tools to Detect Signatures of Colorectal Malignancies: A Modern Approach in Patient's Stratification

Colorectal cancer (CRC) is the second most frequently diagnosed type of cancer and a major worldwide public health concern. Despite the global efforts in the development of modern therapeutic strategies, CRC prognosis is strongly correlated with the stage of the disease at diagnosis. Early detection of CRC has a huge impact in decreasing mortality while pre-lesion detection significantly reduces the incidence of the pathology. Even though the management of CRC patients is based on robust diagnostic methods such as serum tumor markers analysis, colonoscopy, histopathological analysis of tumor tissue, and imaging methods (computer tomography or magnetic resonance), these strategies still have many limitations and do not fully satisfy clinical needs due to their lack of sensitivity and/or specificity. Therefore, improvements of the current practice would substantially impact the management of CRC patients. In this view, liquid biopsy is a promising approach that could help clinicians screen for disease, stratify patients to the best treatment, and monitor treatment response and resistance mechanisms in the tumor in a regular and minimally invasive manner. Liquid biopsies allow the detection and analysis of different tumor-derived circulating markers such as cell-free nucleic acids (cfNA), circulating tumor cells (CTCs), and extracellular vesicles (EVs) in the bloodstream. The major advantage of this approach is its ability to trace and monitor the molecular profile of the patient's tumor and to predict personalized treatment in real-time. On the other hand, the prospective use of artificial intelligence (AI) in medicine holds great promise in oncology, for the diagnosis, treatment, and prognosis prediction of disease. AI has two main branches in the medical field: (i) a virtual branch that includes medical imaging, clinical assisted diagnosis, and treatment, as well as drug research, and (ii) a physical branch that includes surgical robots. This review summarizes findings relevant to liquid biopsy and AI in CRC for better management and stratification of CRC patients.

Higher platelet counts correlate to tumour progression and can be induced by intratumoural stroma in non-metastatic breast carcinomas

BACKGROUND

Platelets support tumour progression. However, their prognostic significance and relation to circulating tumour cells (CTCs) in operable breast cancer (BrCa) are still scarcely known and, thus, merit further investigation.

METHODS

Preoperative platelet counts (PCs) were compared with clinical data, CTCs, 65 serum cytokines and 770 immune-related transcripts obtained using the NanoString technology.

RESULTS

High normal PC (hPC; defined by the 75th centile cut-off) correlated with an increased number of lymph node metastases and mesenchymal CTCs in the 70 operable BrCa patients. Patients with hPC and CTC presence revealed the shortest overall survival compared to those with no CTC/any PC or even CTC/normal PC. Adverse prognostic impact of hPC was observed only in the luminal subtype, when 247 BrCa patients were analysed. hPC correlated with high content of intratumoural stroma, specifically its phenotype related to CD8+ T and resting mast cells, and an increased concentration of cytokines related to platelet activation or even production in bone marrow (i.e. APRIL, ENA78/CXCL5, HGF, IL16, IL17a, MDC/CCL22, MCP3, MMP1 and SCF).

CONCLUSIONS

Preoperative platelets evaluated alone and in combination with CTCs have prognostic potential in non-metastatic BrCa and define patients at the highest risk of disease progression, putatively benefiting from anti-platelet therapy.

Detection of circulating rare cells benefitted the diagnosis of malignant solitary pulmonary nodules

INTRODUCTION

Solitary pulmonary nodules (SPNs) are challenging in differentiating between benignancy and malignancy. Therefore, more effective non-invasive biomarkers are urgently needed. The purpose of this investigation was to examine whether circulating rare cells (CRCs) could facilitate the differentiation between benign and malignant SPNs as well as its sensitivity and specificity.

METHODS

164 patients diagnosed with SPNs, 24 healthy volunteers, and 25 patients diagnosed with advanced-stage lung cancer were included. CT/PET-CT images, serum tumor markers, and biopsy results were collected. The CRCs were examined using subtraction enrichment and immunostaining-fluorescence in situ hybridization (SE-iFISH) and their relationship with malignant or benign SPNs was analyzed.

RESULTS

The total CRC numbers from patients with malignant SPNs diagnosed by biopsy were significantly greater compared to those with benign SPNs (P < 0.0001), but not significantly different from patients with advanced lung cancer (P > 0.05). The total CRCs, with a cut-off value of 21.5 units, showed 67.6% sensitivity and 73.3% specificity [area under curve (AUC) 95% CI, 0.778 (0.666-0.889)] in discriminating benign and malignant SPNs and the triploid CRCs exhibited a high positive likelihood ratio of 8.4, which suggested that CRCs appeared to have a distinct advantage in discriminating benign and malignant SPNs compared to CT/PET-CT images and serum tumor markers and could be a potential screening indicator for lung cancer in the high-risk population.

CONCLUSIONS

SE-iFISH could effectively detect CRCs including circulating tumor cells (CTCs) and circulating tumor-derived endothelial cells (CTECs) and the detection of CRCs could benefit the differentiation of patients with benign and malignant SPNs.

Desmosomal proteins of DSC2 and PKP1 promote cancer cells survival and metastasis by increasing cluster formation in circulatory system

To study how cancer cells can withstand fluid shear stress (SS), we isolated SS-resistant breast and lung cancer cells using a microfluidic circulatory system. These SS-resistant cells showed higher abilities to form clusters, survive in circulation, and metastasize in mice. These SS-resistant cells expressed 4.2- to 5.3-fold more desmocollin-2 (DSC2) and plakophilin-1 (PKP1) proteins. The high expression of DSC2 and PKP1 facilitated cancer cells to form clusters in circulation, and also activated PI3K/AKT/Bcl-2–mediated pathway to increase cell survival. The high levels of DSC2 and PKP1 are also important for maintaining high expression of vimentin, which stimulates fibronectin/integrin β1/FAK/Src/MEK/ERK/ZEB1–mediated metastasis. Moreover, higher levels of DSC2 and PKP1 were detected in tumor samples from patients with breast and lung cancer, and their high expression was correlated with lower overall survival and worse disease progression. DSC2 and PKP1 may serve as new biomarkers for detecting and targeting metastatic circulating tumor cells.

Emerging Insights into Keratin 16 Expression during Metastatic Progression of Breast Cancer

Simple Summary

The mechanisms leading to tumor metastasis remain poorly understood, and therefore, phenotyping of circulating tumor cells from cancer patients may contribute to translating these mechanisms. In in silico analysis, high expression of keratin 16 was associated with higher tumor aggressiveness. According to our results, keratin 16 is a metastasis-associated protein that promotes EMT and acts as a positive regulator of cellular motility by reorganizing the actin cytoskeleton, which is the driving force behind disrupting intercellular adhesion and directional migration. In metastatic breast cancer patients, circulating tumor cells expressing keratin 16 were associated with shorter relapse-free survival. This is an important issue for future research to determine the exact function of keratin 16 in tumor dissemination and metastasis development by analyzing keratin 16 status in disseminating tumor cells. Furthermore, gaining a better knowledge of keratin 16’s biology would give crucial mechanistic insights that might lead to a unique treatment option.

Abstract

Keratins are the main identification markers of circulating tumor cells (CTCs); however, whether their deregulation is associated with the metastatic process is largely unknown. Previously we have shown by in silico analysis that keratin 16 (KRT16) mRNA upregulation might be associated with more aggressive cancer. Therefore, in this study, we investigated the biological role and the clinical relevance of K16 in metastatic breast cancer. By performing RT-qPCR, western blot, and immunocytochemistry, we investigated the expression patterns of K16 in metastatic breast cancer cell lines and evaluated the clinical relevance of K16 expression in CTCs of 20 metastatic breast cancer patients. High K16 protein expression was associated with an intermediate mesenchymal phenotype. Functional studies showed that K16 has a regulatory effect on EMT and overexpression of K16 significantly enhanced cell motility (p < 0.001). In metastatic breast cancer patients, 64.7% of the detected CTCs expressed K16, which was associated with shorter relapse-free survival (p = 0.0042). Our findings imply that K16 is a metastasis-associated protein that promotes EMT and acts as a positive regulator of cellular motility. Furthermore, determining K16 status in CTCs provides prognostic information that helps to identify patients whose tumors are more prone to metastasize.

Circulating Tumor Cells Undergoing the Epithelial-Mesenchymal Transition: Influence on Prognosis in Cytokeratin 19-Positive Hepatocellular Carcinoma

Purpose

The purpose of this study was to elucidate the relationship between cytokeratin 19 (CK19) expression and levels of circulating tumor cells (CTCs) in preoperative peripheral blood of patients with hepatocellular carcinoma (HCC), and the potential influence of that relationship on prognosis.

Patients and Methods

CanPatrol™ CTC-enrichment technique and in situ hybridization (ISH) were used to enrich and classify CTCs undergoing the epithelial–mesenchymal transition (EMT) from blood samples of 105 HCC patients. CK19 immunohistochemistry staining was performed on HCC tissues and compared with demographic and clinical data.

Results

In total, 27 of 105 (25.7%) HCC patients were CK19-positive. CK19-positive patients had significantly lower median tumor-free survival (TFS) than CK19-negative patients (5 vs 10 months, P = 0.047). In total, 98 (93.3%) patients showed pre-surgery peripheral blood CTCs (range: 0–76, median: 6), and 57 of 105 (54.3%) patients displayed CTC counts ≥6. Furthermore, CK19-positive patients with CTC count ≥6 showed significantly higher percentage than CK19-negative ones (77.8% vs 46.2%, P = 0.004). CK19-positive patients showed a significantly higher proportion of mesenchymal CTCs among CTCs undergoing EMT than CK19-negative patients (mean rank: 62.28 vs 49.79, P = 0.046). We also found that CK19-positive patients with high CTC count showed significantly shorter median tumor-free survival than CK19-negative patients with low CTC count (5 vs 16 months, P = 0.039).

Conclusion

High CTC count and high percentage of mesenchymal CTCs are closely related to the expression of CK19, which is associated with poor prognosis in HCC patients.

A Review of Circulating Tumour Cell Enrichment Technologies

Simple Summary

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

Abstract

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

Advancing Biomarker Development Through Convergent Engagement: Summary Report of the 2nd International Danube Symposium on Biomarker Development, Molecular Imaging and Applied Diagnostics; March 14-16, 2018; Vienna, Austria

Here, we report on the outcome of the 2nd International Danube Symposium on advanced biomarker development that was held in Vienna, Austria, in early 2018. During the meeting, cross-speciality participants assessed critical aspects of non-invasive, quantitative biomarker development in view of the need to expand our understanding of disease mechanisms and the definition of appropriate strategies both for molecular diagnostics and personalised therapies. More specifically, panelists addressed the main topics, including the current status of disease characterisation by means of non-invasive imaging, histopathology and liquid biopsies as well as strategies of gaining new understanding of disease formation, modulation and plasticity to large-scale molecular imaging as well as integrative multi-platform approaches. Highlights of the 2018 meeting included dedicated sessions on non-invasive disease characterisation, development of disease and therapeutic tailored biomarkers, standardisation and quality measures in biospecimens, new therapeutic approaches and socio-economic challenges of biomarker developments. The scientific programme was accompanied by a roundtable discussion on identification and implementation of sustainable strategies to address the educational needs in the rapidly evolving field of molecular diagnostics. The central theme that emanated from the 2nd Donau Symposium was the importance of the conceptualisation and implementation of a convergent approach towards a disease characterisation beyond lesion-counting "lumpology" for a cost-effective and patient-centric diagnosis, therapy planning, guidance and monitoring. This involves a judicious choice of diagnostic means, the adoption of clinical decision support systems and, above all, a new way of communication involving all stakeholders across modalities and specialities. Moreover, complex diseases require a comprehensive diagnosis by converging parameters from different disciplines, which will finally yield to a precise therapeutic guidance and outcome prediction. While it is attractive to focus on technical advances alone, it is important to develop a patient-centric approach, thus asking "What can we do with our expertise to help patients?"

LKB1 and cancer: The dual role of metabolic regulation

Liver kinase B1 (LKB1) is an essential serine/threonine kinase frequently associated with Peutz-Jeghers syndrome (PJS). In this review, we provide an overview of the role of LKB1 in conferring protection to cancer cells against metabolic stress and promoting cancer cell survival and invasion. This carcinogenic effect contradicts the previous conclusion that LKB1 is a tumor suppressor gene. Here we try to explain the contradictory effect of LKB1 on cancer from a metabolic perspective. Upon deletion of LKB1, cancer cells experience increased energy as well as oxidative stress, thereby causing genomic instability. Meanwhile, mutated LKB1 cooperates with other metabolic regulatory genes to promote metabolic reprogramming that subsequently facilitates adaptation to strong metabolic stress, resulting in development of a more aggressive malignant phenotype. We aim to specifically discuss the contradictory role of LKB1 in cancer by reviewing the mechanism of LKB1 with an emphasis on metabolic stress and metabolic reprogramming.

Photodynamic inactivation of circulating tumor cells: An innovative approach against metastatic cancer

The spread of a primary malignant tumor is the major reason for most of the cancer-associated deaths. To this day, treatment regimen and available drugs are still insufficient to manage these conditions. In this work, a new therapeutic concept based on photodynamic therapy (PDT) of metastasis-initiating cells is introduced. To address this issue, an experimental model was developed to simulate the movement and photodynamic inactivation of circulating tumor cells (CTCs) in vitro. Using curcumin loaded poly(lactic-co-glycolic acid) nanoparticles, a significant reduction in the cell viability of human breast cancer cells (MDA-MB-231) could be achieved after 30 min laser irradiation (λ = 447 nm, P = 100mW) under flow conditions (5 cm s^-1). Confocal laser scanning microscopy images confirmed the immediate accumulation of curcumin on the cell membrane and an increased fluorescence signal after irradiation. PDT caused time-dependent morphological cell alterations (i.e. membrane evaginations and disruption) indicating apoptosis and early necrosis. During the photoactivation of curcumin, a blue shift in the absorption spectra and a decrease in the curcumin content could be determined. This study confirms that the presented experimental model is suitable for in vitro investigations of CTCs under in vivo-like conditions, at the same time encouraging the clinical implementation of PDT as an innovative strategy against metastasis.

Prognostic value of partial EMT-related genes in head and neck squamous cell carcinoma by a bioinformatic analysis

OBJECTIVE

Recent studies have revealed that the ability of cancer cells to undergo intermediate state of epithelial-to-mesenchymal transition (EMT), partial EMT (p-EMT), poses a higher metastatic risk rather than complete EMT. Here, we examined the prognostic value of p-EMT-related genes in head and neck squamous cell carcinoma (HNSCC) by bioinformatic approaches.

MATERIALS AND METHODS

We used RNA-seq data of 519 primary HNSCC cases obtained from TCGA database. We compared the expression of p-EMT-related genes in HNSCC tissues with normal tissues. We evaluated the prognostic value of p-EMT-related genes in HNSCC cases by log-rank test. We examined the expression of p-EMT-, EMT-, and epithelial differentiation-related genes by qPCR.

RESULTS

Among p-EMT-related genes that were highly expressed in HNSCC cases, high expression of SERPINE1, ITGA5, TGFBI, P4HA2, CDH13, and LAMC2 was significantly correlated with poor survival of HNSCC patients. By gene expression pattern, HNSCC cell lines were classified into three groups: epithelial phenotype, EMT phenotype, and p-EMT phenotype.

CONCLUSIONS

Our findings suggest that p-EMT program may be involved in poor prognosis of HNSCC. SERPINE1, ITGA5, TGFBI, P4HA2, CDH13, and LAMC2 can be used for a prognostic marker. Moreover, HNSCC cells with p-EMT phenotype can be a useful model for investigating a nature of p-EMT.

Electrical Impedance Spectroscopy for Monitoring Chemoresistance of Cancer Cells

Electrical impedance spectroscopy (EIS) is an electrokinetic method that allows for the characterization of intrinsic dielectric properties of cells. EIS has emerged in the last decade as a promising method for the characterization of cancerous cells, providing information on inductance, capacitance, and impedance of cells. The individual cell behavior can be quantified using its characteristic phase angle, amplitude, and frequency measurements obtained by fitting the input frequency-dependent cellular response to a resistor-capacitor circuit model. These electrical properties will provide important information about unique biomarkers related to the behavior of these cancerous cells, especially monitoring their chemoresistivity and sensitivity to chemotherapeutics. There are currently few methods to assess drug resistant cancer cells, and therefore it is difficult to identify and eliminate drug-resistant cancer cells found in static and metastatic tumors. Establishing techniques for the real-time monitoring of changes in cancer cell phenotypes is, therefore, important for understanding cancer cell dynamics and their plastic properties. EIS can be used to monitor these changes. In this review, we will cover the theory behind EIS, other impedance techniques, and how EIS can be used to monitor cell behavior and phenotype changes within cancerous cells.

Involvement of Fusobacterium Species in Oral Cancer Progression: A Literature Review Including Other Types of Cancer

Chronic inflammation caused by infections has been suggested to be one of the most important cause of cancers. It has recently been shown that there is correlation between intestinal bacteria and cancer development including metastasis. As over 700 bacterial species exist in an oral cavity, it has been concerning that bacterial infection may cause oral cancer. However, the role of bacteria regarding tumorigenesis of oral cancer remains unclear. Several papers have shown that Fusobacterium species deriving the oral cavities, especially, play a crucial role for the development of colorectal and esophageal cancer. F. nucleatum is a well-known oral bacterium involved in formation of typical dental plaque on human teeth and causing periodontal diseases. The greatest characteristic of F. nucleatum is its ability to adhere to various bacteria and host cells. Interestingly, F. nucleatum is frequently detected in oral cancer tissues. Moreover, detection of F. nucleatum is correlated with the clinical stage of oral cancer. Although the detailed mechanism is still unclear, Fusobacterium species have been suggested to be associated with cell adhesion, tumorigenesis, epithelial-to-mesenchymal transition, inflammasomes, cell cycle, etc. in oral cancer. In this review, we introduce the reports focused on the association of Fusobacterium species with cancer development and progression including oral, esophageal, and colon cancers.

EMT-Associated Heterogeneity in Circulating Tumor Cells: Sticky Friends on the Road to Metastasis

Epithelial-mesenchymal transitions (EMTs) generate hybrid phenotypes with an enhanced ability to adapt to diverse microenvironments encountered during the metastatic spread. Accordingly, EMTs play a crucial role in the biology of circulating tumor cells (CTCs) and contribute to their heterogeneity. Here, we review major EMT-driven properties that may help hybrid Epithelial/Mesenchymal CTCs to survive in the bloodstream and accomplish early phases of metastatic colonization. We then discuss how interrogating EMT in CTCs as a companion biomarker could help refine cancer patient management, further supporting the relevance of CTCs in personalized medicine.

The promise of single-cell mechanophenotyping for clinical applications

Cancer is the second leading cause of death worldwide. Despite the immense research focused in this area, one is still not able to predict disease trajectory. To overcome shortcomings in cancer disease study and monitoring, we describe an exciting research direction: cellular mechanophenotyping. Cancer cells must overcome many challenges involving external forces from neighboring cells, the extracellular matrix, and the vasculature to survive and thrive. Identifying and understanding their mechanical behavior in response to these forces would advance our understanding of cancer. Moreover, used alongside traditional methods of immunostaining and genetic analysis, mechanophenotyping could provide a comprehensive view of a heterogeneous tumor. In this perspective, we focus on new technologies that enable single-cell mechanophenotyping. Single-cell analysis is vitally important, as mechanical stimuli from the environment may obscure the inherent mechanical properties of a cell that can change over time. Moreover, bulk studies mask the heterogeneity in mechanical properties of single cells, especially those rare subpopulations that aggressively lead to cancer progression or therapeutic resistance. The technologies on which we focus include atomic force microscopy, suspended microchannel resonators, hydrodynamic and optical stretching, and mechano-node pore sensing. These technologies are poised to contribute to our understanding of disease progression as well as present clinical opportunities.

Gauging the Impact of Cancer Treatment Modalities on Circulating Tumor Cells (CTCs)

The metastatic cascade consists of multiple complex steps, but the belief that it is a linear process is diminishing. In order to metastasize, cells must enter the blood vessels or body cavities (depending on the cancer type) via active or passive mechanisms. Once in the bloodstream and/or lymphatics, these cancer cells are now termed circulating tumor cells (CTCs). CTC numbers as well as CTC clusters have been used as a prognostic marker with higher numbers of CTCs and/or CTC clusters correlating with an unfavorable prognosis. However, we have very limited knowledge about CTC biology, including which of these cells are ultimately responsible for overt metastatic growth, but due to the fact that higher numbers of CTCs correlate with a worse prognosis; it would seem appropriate to either limit CTCs and/or their dissemination. Here, we will discuss the different cancer treatments which may inadvertently promote the mobilization of CTCs and potential CTC therapies to decrease metastasis.

Clinical Relevance of Circulating Tumor Cells in Esophageal Cancer Detected by a Combined MACS Enrichment Method

INTRODUCTION

Current modalities to predict tumor recurrence and survival in esophageal cancer are insufficient. Even in lymph node-negative patients, a locoregional and distant relapse is common. Hence, more precise staging methods are needed. So far, only the CellSearch system was used to detect circulating tumor cells (CTC) with clinical relevance in esophageal cancer patients. Studies analyzing different CTC detection assays using advanced enrichment techniques to potentially increase the sensitivity are missing.

METHODS

In this single-center, prospective study, peripheral blood samples from 90 esophageal cancer patients were obtained preoperatively and analyzed for the presence of CTCs by Magnetic Cell Separation (MACS) enrichment (combined anti-cytokeratin and anti-epithelial cell adhesion molecules (EpCAM)), with subsequent immunocytochemical staining. Data were correlated with clinicopathological parameters and patient outcomes.

RESULTS

CTCs were detected in 25.6% (23/90) of the patients by combined cytokeratin/EpCAM enrichment (0-150 CTCs/7.5 mL). No significant correlation between histopathological parameters and CTC detection was found. Survival analysis revealed that the presence of more than two CTCs correlated with significantly shorter overall survival (OS) and progression-free survival (PFS).

CONCLUSION

With the use of cytokeratin as an additional enrichment target, the CTC detection rate in esophageal cancer patients can be elevated and displays the heterogeneity of cytokeratin (CK) and EpCAM expression. The presence of >2CTCs correlated with a shorter relapse-free and overall survival in a univariate analysis, but not in a multivariate setting. Moreover, our results suggest that the CK7/8+/EpCAM+ or CK7/8+/EpCAM- CTC subtype does not lead to an advanced tumor staging tool in non-metastatic esophageal cancer (EC) patients.

Active PLK1-driven metastasis is amplified by TGF-β signaling that forms a positive feedback loop in non-small cell lung cancer

Early findings that PLK1 is highly expressed in cancer have driven an exploration of its functions in metastasis. However, whether PLK1 induces metastasis in vivo and its underlying mechanisms in NSCLC have not yet been determined. Here, we show that the expression of active PLK1 phosphorylated at T210, abundant in TGF-β-treated lung cells, potently induced metastasis in a tail-vein injection model. Active PLK1 with intact polo-box and ATP-binding domains accelerated cell motility and invasiveness by triggering EMT reprogramming, whereas a phosphomimetic version of p-S137-PLK1 did not, indicating that the phosphorylation status of PLK1 may determine the cell traits. Active PLK1-driven invasiveness upregulated TGF-β signaling and TSG6 encoded by TNFAIP6. Loss of TNFAIP6 disturbed the metastatic activity induced by active PLK1 or TGF-β. Clinical relevance shows that PLK1 and TNFAIP6 are strong predictors of poor survival rates in metastatic NSCLC patients. Therefore, we suggest that active PLK1 promotes metastasis by upregulating TGF-β signaling, which amplifies its metastatic properties by forming a positive feedback loop and that the PLK1/TGF-β-driven metastasis is effectively blocked by targeting PLK1 and TSG6, providing PLK1 and TSG6 as negative markers for prognostics and therapeutic targets in metastatic NSCLC.

Epstein-Barr Virus-Encoded Products Promote Circulating Tumor Cell Generation: A Novel Mechanism of Nasopharyngeal Carcinoma Metastasis

Epstein–Barr virus (EBV) is a specific tumorigenic factor in the pathogenesis of nasopharyngeal carcinoma (NPC). Viral products encoded by EBV (LMP1, LMP2A, EBNA1, and miRNAs) have been shown to promote NPC metastasis. EBV-encoded oncoproteins and miRNAs have been shown to induce epithelial–mesenchymal transition (EMT) indirectly by inducing EMT transcription factors (EMT-TFs). These EBV-encoded products also promote the expression of EMT-TFs through post-transcriptional regulation. EMT contributes to generation of circulating tumor cells (CTCs) in epithelial cancers. CTCs exhibit stem cell characteristics, including increased invasiveness, enhanced cell intravasation, and improved cell survival in the peripheral system. EBV may contribute NPC metastasis through promoting generation of CTCs. Furthermore, CTC karyotypes are associated with NPC staging, therapeutic sensitivity, and resistance. We summarized studies showing that EBV-encoded virus-proteins and miRNAs promote generation of NPC CTCs, and highlighted the associated mechanism. This synthesis indicated that EBV mediates NPC metastasis through generation of CTCs.

New Labyrinth Microfluidic Device Detects Circulating Tumor Cells Expressing Cancer Stem Cell Marker and Circulating Tumor Microemboli in Hepatocellular Carcinoma

Hepatocellular Carcinoma (HCC) is one of the most lethal cancers with a high mortality and recurrence rate. Circulating tumor cell (CTC) detection offers various opportunities to advance early detection and monitoring of HCC tumors which is crucial for improving patient outcome. We developed and optimized a novel Labyrinth microfluidic device to efficiently isolate CTCs from peripheral blood of HCC patients. CTCs were identified in 88.1% of the HCC patients over different tumor stages. The CTC positivity rate was significantly higher in patients with more advanced HCC stages. In addition, 71.4% of the HCC patients demonstrated CTCs positive for cancer stem cell marker, CD44, suggesting that the major population of CTCs could possess stemness properties to facilitate tumor cell survival and dissemination. Furthermore, 55% of the patients had the presence of circulating tumor microemboli (CTM) which also correlated with advanced HCC stage, indicating the association of CTM with tumor progression. Our results show effective CTC capture from HCC patients, presenting a new method for future noninvasive screening and surveillance strategies. Importantly, the detection of CTCs with stemness markers and CTM provides unique insights into the biology of CTCs and their mechanisms influencing metastasis, recurrence and therapeutic resistance.

The role of polarisation of circulating tumour cells in cancer metastasis

Metastasis is the spread of cancer cells from a primary tumour to a distant site of the body. Metastasising tumour cells have to survive and readjust to different environments, such as heterogeneous solid tissues and liquid phase in lymph- or blood circulation, which they achieve through a high degree of plasticity that renders them adaptable to varying conditions. One defining characteristic of the metastatic process is the transition of tumour cells between different polarised phenotypes, ranging from differentiated epithelial polarity to migratory front-rear polarity. Here, we review the polarisation types adopted by tumour cells during the metastatic process and describe the recently discovered single-cell polarity in liquid phase observed in circulating tumour cells. We propose that single-cell polarity constitutes a mode of polarisation of the cell cortex that is uncoupled from the intracellular polarisation machinery, which distinguishes single-cell polarity from other types of polarity identified so far. We discuss how single-cell polarity can contribute to tumour metastasis and the therapeutic potential of this new discovery.

Lung-Seeking Metastases

Metastases from different cancer types most often affect the lung parenchyma. Moreover, the lungs are among the most frequent sites of growth of metastatic masses of uncertain/unknown lineage of origin. Thus, with regards to pulmonary neoplastic parenchymal nodules, the critical issue is to determine if they are IN the lung or OF the lung. In this review, we highlight the clinical, instrumental and molecular features which characterize lung metastases, mainly focusing on recently advancing and emerging concepts regarding the metastatic niche, inflammation, angiogenesis, immune modulation and gene expression. A novel issue is related to the analysis of biomechanical forces which cooperate in the expansion of tumor masses in the lungs. We here aim to analyze the biological, genetic and pathological features of metastatic lesions to the lungs, here referred to as site of metastatic growth. This point should be a crucial part of the algorithm for a proper diagnostic and therapeutic approach in the era of personalized medicine.

Uncoupling Traditional Functionalities of Metastasis: The Parting of Ways with Real-Time Assays

The experimental evaluation of metastasis overly focuses on the gain of migratory and invasive properties, while disregarding the contributions of cellular plasticity, extra-cellular matrix heterogeneity, niche interactions, and tissue architecture. Traditional cell-based assays often restrict the inclusion of these processes and warrant the implementation of approaches that provide an enhanced spatiotemporal resolution of the metastatic cascade. Time lapse imaging represents such an underutilized approach in cancer biology, especially in the context of disease progression. The inclusion of time lapse microscopy and microfluidic devices in routine assays has recently discerned several nuances of the metastatic cascade. Our review emphasizes that a complete comprehension of metastasis in view of evolving ideologies necessitates (i) the use of appropriate, context-specific assays and understanding their inherent limitations; (ii) cautious derivation of inferences to avoid erroneous/overestimated clinical extrapolations; (iii) corroboration between multiple assay outputs to gauge metastatic potential; and (iv) the development of protocols with improved in situ implications. We further believe that the adoption of improved quantitative approaches in these assays can generate predictive algorithms that may expedite therapeutic strategies targeting metastasis via the development of disease relevant model systems. Such approaches could potentiate the restructuring of the cancer metastasis paradigm through an emphasis on the development of next-generation real-time assays.

Advances in liquid biopsy using circulating tumor cells and circulating cell-free tumor DNA for detection and monitoring of breast cancer

Overview the progress of liquid biopsy using circulating tumor cells (CTCs) and circulating cell-free tumor DNA (cfDNA) to detect and monitor breast cancer. Based on numerous research efforts, the potential value of CTCs and cfDNA in the clinical aspects of cancer has become clear. With the development of next-generation sequencing analysis and newly developed technologies, many technical issues have been resolved, making liquid biopsy widely used in clinical practice. They can be powerful tools for dynamic monitoring of tumor progression and therapeutic efficacy. In the field of breast cancer, liquid biopsy is a research hot spot in recent years, playing a key role in monitoring breast cancer metastasis, predicting disease recurrence and assessing clinical drug resistance. Liquid biopsy has the advantages of noninvasive, high sensitivity, high specificity and real-time dynamic monitoring. Still application is far from reality, but the research and application prospects of CTCs and cfDNA in breast cancer are still worth exploring and discovering. This article reviews the main techniques and applications of CTCs and cfDNA in breast cancer.

Epithelial-type systemic breast carcinoma cells with a restricted mesenchymal transition are a major source of metastasis

Carcinoma cells undergo epithelial-mesenchymal transition (EMT); however, contributions of EMT heterogeneity to disease progression remain a matter of debate. Here, we addressed the EMT status of ex vivo cultured circulating and disseminated tumor cells (CTCs/DTCs) in a syngeneic mouse model of metastatic breast cancer (MBC). Epithelial-type CTCs with a restricted mesenchymal transition had the strongest lung metastases formation ability, whereas mesenchymal-type CTCs showed limited metastatic ability. EpCAM expression served as a surrogate marker to evaluate the EMT heterogeneity of clinical samples from MBC, including metastases, CTCs, and DTCs. The proportion of epithelial-type CTCs, and especially DTCs, correlated with distant metastases and poorer outcome of patients with MBC. This study fosters our understanding of EMT in metastasis and underpins heterogeneous EMT phenotypes as important parameters for tumor prognosis and treatment. We further suggest that EpCAM-dependent CTC isolation systems will underestimate CTC numbers but will quantify clinically relevant metastatic cells.

Clinical utility of circulating non-coding RNAs - an update

Over the past decade, the amount of research and the number of publications on associations between circulating small and long non-coding RNAs (ncRNAs) and cancer have grown exponentially. Particular focus has been placed on the development of diagnostic and prognostic biomarkers to enable efficient patient management - from early detection of cancer to monitoring for disease recurrence or progression after treatment. Owing to their high abundance and stability, circulating ncRNAs have potential utility as non-invasive, blood-based biomarkers that can provide information on tumour biology and the effects of treatments, such as targeted therapies and immunotherapies. Increasing evidence highlights the roles of ncRNAs in cell-to-cell communication, with a number of ncRNAs having the capacity to regulate gene expression outside of the cell of origin through extracellular vesicle-mediated transfer to recipient cells, with implications for cancer progression and therapy resistance. Moreover, 'foreign' microRNAs (miRNAs) encoded by non-human genomes (so-called xeno-miRNAs), such as viral miRNAs, have been shown to be present in human body fluids and can be used as biomarkers. Herein, we review the latest developments in the use of circulating ncRNAs as diagnostic and prognostic biomarkers and discuss their roles in cell-to-cell communication in the context of cancer. We provide a compendium of miRNAs and long ncRNAs that have been reported in the literature to be present in human body fluids and that have the potential to be used as diagnostic and prognostic cancer biomarkers.

EGFR and HER3 expression in circulating tumor cells and tumor tissue from non-small cell lung cancer patients

Although clinically relevant, the detection rates of EpCAM positive CTCs in non-small cell lung cancer (NSCLC) are surprisingly low. To find new clinically informative markers for CTC detection in NSCLC, the expression of EGFR and HER3 was first analyzed in NSCLC tissue (n = 148). A positive EGFR and HER3 staining was observed in 52.3% and 82.7% of the primary tumors, and in 62.7% and 91.2% of brain metastases, respectively. Only 3.0% of the brain metastases samples were negative for both HER3 and EGFR proteins, indicating that the majority of metastases express these ERBB proteins, which were therefore chosen for CTC enrichment using magnetic cell-separation. Enrichment based on either EGFR or HER3 detected CTCs in 37.8% of the patients, while the combination of EGFR/HER3 enrichment with the EpCAM-based CellSearch technique detected a significantly higher number of 66.7% CTC-positive patients (Cohen’s kappa = −0.280) which underlines the existence of different CTC subpopulations in NSCLC. The malignant origin of keratin-positive/CD45-negative CTC clusters and single CTCs detected after EGFR/HER3 based enrichment was documented by the detection of NSCLC-associated mutations. In conclusion, EGFR and HER3 expression in metastasized NSCLC patients have considerable value for CTC isolation plus multiple markers can provide a novel liquid biopsy approach.

The biology and clinical potential of circulating tumor cells

Background Tumor cells can shed from the tumor, enter the circulation and travel to distant organs, where they can seed metastases. These cells are called circulating tumor cells (CTCs). The ability of CTCs to populate distant tissues and organs has led us to believe they are the primary cause of cancer metastasis. The biological properties and interaction of CTCs with other cell types during intravasation, circulation in the bloodstream, extravasation and colonization are multifaceted and include changes of CTC phenotypes that are regulated by many signaling molecules, including cytokines and chemokines. Considering a sample is readily accessible by a simple blood draw, monitoring CTC levels in the blood has exceptional implications in oncology field. A method called the liquid biopsy allows the extraction of not only CTC, but also CTC products, such as cell free DNA (cfDNA), cell free RNA (cfRNA), microRNA (miRNA) and exosomes. Conclusions The clinical utility of CTCs and their products is increasing with advances in liquid biopsy technology. Clinical applications of liquid biopsy to detect CTCs and their products are numerous and could be used for screening of the presence of the cancer in the general population, as well as for prognostic and predictive biomarkers in cancer patients. With the development of better CTC isolation technologies and clinical testing in large prospective trials, increasing clinical utility of CTCs can be expected. The understanding of their biology and interactions with other cell types, particularly with those of the immune system and the rise of immunotherapy also hold great promise for novel therapeutic possibilities.

Heterogeneity in Circulating Tumor Cells: The Relevance of the Stem-Cell Subset

The release of circulating tumor cells (CTCs) into vasculature is an early event in the metastatic process. The analysis of CTCs in patients has recently received widespread attention because of its clinical implications, particularly for precision medicine. Accumulated evidence documents a large heterogeneity in CTCs across patients. Currently, the most accepted view is that tumor cells with an intermediate phenotype between epithelial and mesenchymal have the highest plasticity. Indeed, the existence of a meta-stable or partial epithelial–mesenchymal transition (EMT) cell state, with both epithelial and mesenchymal features, can be easily reconciled with the concept of a highly plastic stem-like state. A close connection between EMT and cancer stem cells (CSC) traits, with enhanced metastatic competence and drug resistance, has also been described. Accordingly, a subset of CTCs consisting of CSC, present a stemness profile, are able to survive chemotherapy, and generate metastases after xenotransplantation in immunodeficient mice. In the present review, we discuss the current evidence connecting CTCs, EMT, and stemness. An improved understanding of the CTC/EMT/CSC connections may uncover novel therapeutic targets, irrespective of the tumor type, since most cancers seem to harbor a pool of CSCs, and disclose important mechanisms underlying tumorigenicity.

Spectrum of Epithelial-Mesenchymal Transition Phenotypes in Circulating Tumour Cells from Early Breast Cancer Patients

Circulating tumour cells (CTCs) can provide valuable prognostic information in a number of epithelial cancers. However, their detection is hampered due to their molecular heterogeneity, which can be induced by the epithelial-mesenchymal transition (EMT) process. Therefore, current knowledge about CTCs from clinical samples is often limited due to an inability to isolate wide spectrum of CTCs phenotypes. In the current work, we aimed at isolation and molecular characterization of CTCs with different EMT status in order to establish their clinical significance in early breast cancer patients. We have obtained CTCs-enriched blood fraction from 83 breast cancer patients in which we have tested the expression of epithelial, mesenchymal and general breast cancer CTCs markers (MGB1/HER2/CK19/CDH1/CDH2/VIM/PLS3), cancer stem cell markers (CD44, NANOG, ALDH1, OCT-4, CD133) and cluster formation gene (plakoglobin). We have shown that in the CTCs-positive patients, epithelial, epithelial-mesenchymal and mesenchymal CTCs markers were detected at a similar rate (in 28%, 24% and 24%, respectively). Mesenchymal CTCs were characterized by the most aggressive phenotype (significantly higher expression of CXCR4, uPAR, CD44, NANOG, p < 0.05 for all), presence of lymph node metastases (p = 0.043), larger tumour size (p = 0.023) and 7.33 higher risk of death in the multivariate analysis (95% CI 1.06–50.41, p = 0.04). Epithelial-mesenchymal subtype, believed to correspond to highly plastic and aggressive state, did not show significant impact on survival. Gene expression profile of samples with epithelial-mesenchymal CTCs group resembled pure epithelial or pure mesenchymal phenotypes, possibly underlining degree of EMT activation in particular patient’s sample. Molecular profiling of CTCs EMT phenotype provides more detailed and clinically informative results, proving the role of EMT in malignant cancer progression in early breast cancer.

Profiling Heterogeneous Circulating Tumor Cells (CTC) Populations in Pancreatic Cancer Using a Serial Microfluidic CTC Carpet Chip

Although isolation of circulating tumor cells (CTCs) from pancreatic adenocarcinoma patients is feasible, investigating their clinical utility has proven less successful than other cancers due to the limitations of epithelial cellular adhesion molecule (EpCAM)‐only based CTC assays. An integrated technology‐ and biology‐based approach using a microfluidic “Carpet Chip” is presented to study the biological relevance of heterogeneous CTC populations. Both epithelial CTCs (EpCs) and epithelial‐to‐mesenchymal transition (EMT)‐like CTCs (EMTCs) are isolated simultaneously from the whole blood of pancreatic cancer (PaCa) patients (n = 35) by separately targeting two surface markers: EpCAM and CD133. Recovery of cancer cell lines spiked into whole blood is ≥97% with >76% purity. Thirty‐four patients had ≥5 EpCs mL−1 and 35 patients had ≥15 EMTCs mL−1. Overall, significantly higher numbers of EMTCs than EpCs are recovered, reflecting the aggressive nature of PaCa. Furthermore, higher numbers of EMTCs are observed in patients with lymph node involvement compared to patients without. Gene expression profiling of CTCs from 17 patients reveals that CXCR1 is significantly upregulated in EpCs, while known stem cell markers POU5F1/Oct‐4 and MYC are upregulated in EMTCs. In conclusion, successful isolation and genomic profiling of heterogeneous CTC populations are demonstrated, revealing genetic signatures relevant to patient outcomes.