Small cell lung cancer: Circulating tumor cells of extended stage patients express a mesenchymal-epithelial transition phenotype

Small cell lung cancer unveiled: Exploring the untapped resource of circulating tumor cells-derived organoids

Small cell lung cancer (SCLC) remains a challenge in oncology due to its aggressive behavior and dismal prognosis. Despite advances in treatments, novel strategies are urgently needed. Enter liquid biopsy-a game-changer in SCLC management. This revolutionary non-invasive approach allows for the analysis of circulating tumor cells (CTCs), offering insights into tumor behavior and treatment responses. Our review focuses on a groundbreaking frontier: harnessing CTCs to create three-dimensional (3D) organoid models. These models, derived from CTCs that break away from the primary tumor or metastatic locations, hold immense potential for revolutionizing cancer research, especially in SCLC. We explore the essential conditions for successfully establishing CTC-derived organoids-a transformative approach with profound implications for personalized medicine. Our evaluation spans diverse isolation techniques, shedding light on their advantages and limitations. Furthermore, we uncover the critical factors governing the cultivation of 3D organoids from CTCs, meticulously mimicking the tumor microenvironment. This review comprehensively elucidates the molecular characterization of these organoids, showcasing their potential in identifying treatment targets and predicting responses. In essence, our review amalgamates cutting-edge methodologies for isolating CTCs, establishing transformative CTC-derived organoids, and characterizing their molecular landscape. This represents a promising frontier for advancing personalized medicine in the complex realm of SCLC management and holds significant implications for translational research.

Unique Cohorts of Salivary Gland Cancer Cells as an in-vitro Model of Circulating Tumor Cells

Introduction

The characterization of circulating tumor cells (CTC) and circulating tumor microemboli (CTM) has emerged as both a challenge to the standard view of metastasis, and as a valuable means for understanding genotypic and phenotypic variability shown even within the same cancer type. However, in the case of salivary gland neoplasms, limited data are available for the role that CTCs and CTMs play in metastasis and secondary tumor formation.ru.AQ1 In response to this, we propose that similarities between in vitro clusters of cultured salivary gland cancer cells may act as a surrogate model for in vivo CTCs and CTMs isolated from patients.

Materials and Methods

Using techniques in immunofluorescence, immunoblotting, and 2-dimensional migration, we isolated and characterized a group of cohort cells from a commercially available cell line (HTB-41). Results: Here, cells exhibited a hybrid phenotype with simultaneous expression of both epithelial and mesenchymal markers (E-cadherin, vimentin, and α-SMA). Cohort cells also exhibited increased migration in comparison to parental cells.

Conclusion

Data suggest that these isolated cell clusters may fucntion as a potential in vitro model of CTCs and CTMs.

Effect of Matrix Stiffness and Hepatocyte Growth Factor on Small Cell Lung Cancer Cells in Decellularized Extracellular Matrix-Based Hydrogels

Small cell lung cancer (SCLC) is one of lethal cancers resulting in very low 5-year-survival rate. Although its clinical treatment largely relies on chemotherapy, SCLC cell physiology in three-dimenstional (3D) matrix has been less explored. In this work, the tumor microenvironment is reconstructed with decellularized porcine pulmonary extracellular matrix (dECM) with hyaluronic acid. To modulate matrix stiffness, the methacrylate groups are introduced into both dECM and hyaluronic acid, followed by photocrosslinking with photoinitiator. The stiffness of the resulting dECM-based hydrogel covers the stiffness of normal or cancerous tissue with varying dECM content. The proliferation and cancer stem cell marker expression of encapsulated SCLC cells are promoted in a compliant hydrogel matrix, which has a low shear modulus similar to that of the normal tissue. The hepatocyte growth factor (HGF) that induces SCLC cell invasion and chemoresistance markedly increases invasiveness and gene expression levels of CD44 and Sox2 in the hydrogel matrix. In addition, HGF treatment causes higher resistance against anticancer drugs (cisplatin and paclitaxel) in the 3D microenvironment. These findings indicate that malignant SCLC can be recapitulated in a pulmonary dECM-based matrix.

Phenotyping EMT and MET cellular states in lung cancer patient liquid biopsies at a personalized level using mass cytometry

Malignant pleural effusions (MPEs) can be utilized as liquid biopsy for phenotyping malignant cells and for precision immunotherapy, yet MPEs are inadequately studied at the single-cell proteomic level. Here we leverage mass cytometry to interrogate immune and epithelial cellular profiles of primary tumors and pleural effusions (PEs) from early and late-stage non-small cell lung cancer (NSCLC) patients, with the goal of assessing epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET) states in patient specimens. By using the EMT-MET reference map PHENOSTAMP, we observe a variety of EMT states in cytokeratin positive (CK+) cells, and report for the first time MET-enriched CK+ cells in MPEs. We show that these states may be relevant to disease stage and therapy response. Furthermore, we found that the fraction of CD33+ myeloid cells in PEs was positively correlated to the fraction of CK+ cells. Longitudinal analysis of MPEs drawn 2 months apart from a patient undergoing therapy, revealed that CK+ cells acquired heterogeneous EMT features during treatment. We present this work as a feasibility study that justifies deeper characterization of EMT and MET states in malignant cells found in PEs as a promising clinical platform to better evaluate disease progression and treatment response at a personalized level.

Pan-cancer Analysis Reveals Cancer-dependent Expression of SOX17 and Associated Clinical Outcomes

BACKGROUND/AIM

SRY-box containing gene 17 (SOX17) plays a pivotal role in cancer onset and progression and is considered a potential target for cancer diagnosis and treatment. However, the expression pattern of SOX17 in cancer and its clinical relevance remains unknown. Here, we explored the relationship between the expression of SOX17 and drug response by examining SOX17 expression patterns across multiple cancer types.

MATERIALS AND METHODS

Single-cell and bulk RNA-seq analyses were used to explore the expression profile of SOX17. Analysis results were verified with qPCR and immunohistochemistry. Survival, drug response, and co-expression analyses were performed to illustrate its correlation with clinical outcomes.

RESULTS

The results revealed that abnormal expression of SOX17 is highly heterogenous across multiple cancer types, indicating that SOX17 manifests as a cancer type-dependent feature. Furthermore, the expression pattern of SOX17 is also associated with cancer prognosis in certain cancer types. Strong SOX17 expression correlates with the potency of small molecule drugs that affect PI3K/mTOR signaling. FGF18, a gene highly relevant to SOX17, is involved in the PI3K-AKT signaling pathway. Single-cell RNA-seq analysis demonstrated that SOX17 is mainly expressed in endothelial cells and barely expressed in other cells but spreads to other cell types during the development of ovarian cancer.

CONCLUSION

Our study revealed the expression pattern of SOX17 in pan-cancer through bulk and single-cell RNA-seq analyses and determined that SOX17 is related to the diagnosis, staging, and prognosis of some tumors. These findings have clinical implications and may help identify mechanistic pathways amenable to pharmacological interventions.

Repeatedly next-generation sequencing during treatment follow-up of patients with small cell lung cancer

Somatic alterations in tumors are a frequent occurrence. In small cell lung cancer (SCLC), these include mutations in the tumor suppressors TP53 and retinoblastoma (RB1). We used next generation sequencing (NGS) to study specific genetic variants and compare genetic and clinicopathological features of SCLC with healthy control genome. Ten SCLC patients receiving standard chemotherapy, between 2018 and 2019, from the First Hospital of Jilin University were included in this study. Prior patient treatment, NGS was performed using DNA isolated from blood plasma. New NGS analyses were performed after 2 and 4 treatment cycles. Four patients presented with different metastases at diagnosis. Overall, most genes tested presented missense or frameshift variants. TP53, RB1, CREBBP, FAT1 genes presented gain of stop codons. At the single-gene level, the most frequently altered genes were TP53 (8/10 patients, 80%) and RB1 (4/10 patients, 40%), followed by bromodomain containing 4 (BRD4), CREBBP, FAT1, FMS-like tyrosine kinase 3 (FLT3), KDR, poly ADP-ribose polymerase (PARP1), PIK3R2, ROS1, and splicing factor 3b subunit 1 (SF3B1) (2/10 patients, 20%). We identified 5 genes, which have not been previously reported to bear mutations in the context of SCLC. These genes include BRD4, PARP1, FLT3, KDR, and SF3B1. We observed that among the studied individuals, patients with a high number of genetic events, and in which such mutations were not eradicated after treatment, showed a worse prognosis. There has not yet been given enough attention to the above-mentioned genes in SCLC, which will have great clinical prospects for treatment.

Unraveling the Role of Epithelial-Mesenchymal Transition in Adenoid Cystic Carcinoma of the Salivary Glands: A Comprehensive Review

Salivary adenoid cystic carcinoma (SACC) is considered a challenging malignancy; it is characterized by a slow-growing nature, yet a high risk of recurrence and distant metastasis, presenting significant hurdles in its treatment and management. At present, there are no approved targeted agents available for the management of SACC and systemic chemotherapy protocols that have demonstrated efficacy remain to be elucidated. Epithelial-mesenchymal transition (EMT) is a complex process that is closely associated with tumor progression and metastasis, enabling epithelial cells to acquire mesenchymal properties, including increased mobility and invasiveness. Several molecular signaling pathways have been implicated in the regulation of EMT in SACC, and understanding these mechanisms is crucial to identifying new therapeutic targets and developing more effective treatment approaches. This manuscript aims to provide a comprehensive overview of the latest research on the role of EMT in SACC, including the molecular pathways and biomarkers involved in EMT regulation. By highlighting the most recent findings, this review offers insights into potential new therapeutic strategies that could improve the management of SACC patients, especially those with recurrent or metastatic disease.

Significance of circulating tumor cells in lung cancer: a narrative review

Background and Objective

In cancer patients, circulating tumor cells (CTCs) are employed as "Liquid Biopsy" for tumor detection, prognosis and assessment of the response to therapy. CTCs are responsible for tumor dissemination but the mechanisms involved in intravasation, survival in the circulation and extravasation at secondary sites to establish metastases are not fully characterized. In lung cancer patients, CTCs are present in very high numbers in small cell lung cancer (SCLC) that is found disseminated in most patients upon first presentation and has a dismal prognosis. This review aims at the discussion of recent work on metastatic SCLC and novel insights into the process of dissemination derived from the access to a panel of unique SCLC CTC lines.

Methods

PubMed and Euro PMC were searched from January 1st, 2015 to September 23th, 2022 using the following key words: "SCLC", "NSCLC", "CTC" and "Angiogenesis" and supplemented by data from our own work.

Key Content and Findings

Experimental and clinical data indicate that the intravasation of single, apoptotic or clustered CTCs occur via leaky neoangiogenetic vessels in the tumor core and not via crossing of the adjacent tumor stroma after EMT. Furthermore, in lung cancer only EpCAM-positive CTCs have been found to have prognostic impact. All our established SCLC CTC lines form spontaneously EpCAM-positive large and chemoresistant spheroids (tumorospheres) that may become trapped in microvessels in vivo and are suggested to extravasate by physical force. The rate-limiting step of the shedding of CTCs is most likely the presence of irregular and leaky tumor vessels or in case of SCLC, also via vessels formed by vasculogenic mimicry. Therefore, lower microvessel densities (MVD) in NSCLC can explain the relative rarity of CTCs in NSCLC versus SCLC.

Conclusions

The detection of CTCs lacks standardized techniques, is difficult in non-metastatic patients and important cell biological mechanisms of dissemination need still to be resolved, especially in respect to the actual metastasis-inducing cells. Expression of VEGF and the MVD are key prognostic indicators for tumors and ultimately, enumeration of CTCs seems to reflect neoangiogenetic vascular supply of tumors and prognosis.

Small cell lung cancer: circulating tumor cell lines and expression of mediators of angiogenesis and coagulation

Aim

Coagulation is frequently activated in cancer patients and has been correlated with an unfavorable prognosis. To evaluate whether a putative release of tissue factor (TF) by circulating tumor cells (CTCs) represents a target to impair the dissemination of small cell lung cancer (SCLC), the expression of relevant proteins in a panel of permanent SCLC and SCLC CTC cell lines that have been established at the Medical University of Vienna.

Methods

Five CTC and SCLC lines were analyzed using a TF enzyme-linked immunosorbent assay (ELISA) tests, RNA sequencing, and western blot arrays covering 55 angiogenic mediators. Furthermore, the influence of topotecan and epirubicin as well as hypoxia-like conditions on the expression of these mediators was investigated.

Results

The results demonstrate that the SCLC CTC cell lines express no significant amounts of active TF but thrombospondin-1 (TSP-1), urokinase-type plasminogen activator receptor (uPAR), vascular endothelial-derived growth factor (VEGF) and angiopoietin-2 in two cases. The major difference between the SCLC and SCLC CTC cell lines found was the loss of the expression of angiogenin in the blood-derived CTC lines. Topotecan and epirubicin decreased the expression of VEGF, whereas hypoxia-like conditions upregulated VEGF.

Conclusions

Active TF capable of triggering coagulation seems not to be expressed in SCLC CTC cell lines in significant levels and, thus, CTC-derived TF seems dispensable for dissemination. Nevertheless, all CTC lines form large spheroids, termed tumorospheres, which may become trapped in clots of the microvasculature and extravasate in this supportive microenvironment. The contribution of clotting to the protection and dissemination of CTCs in SCLC may be different from other solid tumors such as breast cancer.

Platelet-derived extracellular vesicles inhibit ferroptosis and promote distant metastasis of nasopharyngeal carcinoma by upregulating ITGB3

Nasopharyngeal carcinoma (NPC) is a malignancy with high metastatic and invasive nature. Distant metastasis contributes substantially to treatment failure and mortality in NPC. Platelets are versatile blood cells and the number of platelets is positively associated with the distant metastasis of tumor cells. However, the role and underlying mechanism of platelets responsible for the metastasis of NPC cells remain unclear. Here we found that the distant metastasis of NPC patients was positively correlated with the expression levels of integrin β3 (ITGB3) in platelet-derived extracellular vesicles (EVs) from NPC patients (P-EVs). We further revealed that EVs transfer occurred from platelets to NPC cells, mediating cell-cell communication and inducing the metastasis of NPC cells by upregulating ITGB3 expression. Mechanistically, P-EVs-upregulated ITGB3 increased SLC7A11 expression by enhancing protein stability and activating the MAPK/ERK/ATF4/Nrf2 axis, which suppressed ferroptosis, thereby facilitating the metastasis of NPC cells. NPC xenografts in mouse models further confirmed that P-EVs inhibited the ferroptosis of circulating NPC cells and promoted the distant metastasis of NPC cells. Thus, these findings elucidate a novel role of platelet-derived EVs in NPC metastasis, which not only improves our understanding of platelet-mediated tumor distant metastasis, but also has important implications in diagnosis and treatment of NPC.

NRBF2 regulates the chemoresistance of small cell lung cancer by interacting with the P62 protein in the autophagy process

Reversing chemotherapy resistance in small cell lung cancer (SCLC) is crucial to improve patient prognosis. The present study aims to investigate the underlying mechanisms in SCLC chemoresistance. We see that nuclear receptor binding factor 2 (NRBF2) is a poor prognostic factor in SCLC. The effects of NRBF2 on chemoresistance were determined in SCLC. The underlying molecular mechanisms of NRBF2 in the autophagy process in SCLC were examined. NRBF2 positively regulated autophagy, leading to drug resistance in SCLC. The MIT domain of NRBF2 directly interacted with the PB1 domain of P62. This interaction increased autophagic P62 body formation, revealing the regulatory role of NRBF2 in autophagy. Notably, NRBF2 was directly modulated by the transcription factor XRCC6. The MIT domain of NRBF2 interacts with the PB1 domain of P62 to regulate the autophagy process, resulting in SCLC chemoresistance. NRBF2 is likely a useful chemotherapy response marker and therapeutic target in SCLC.

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NRBF2 promoted the chemoresistance of SCLC in vitro and in vivo

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The chemoresistance induced by NRBF2 was mediated via autophagy in SCLC

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NRBF2 interacting with P62 contributed to autophagic P62 bodies' formation

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NRBF2 was regulated by XRCC6 via direct binding to the NRBF2 gene promoter

Comparative characteristics of small cell lung cancer and Ewing's sarcoma: a narrative review

Background and Objective

Small cell lung cancer (SCLC) and Ewing's sarcoma (ES) at the disseminated stage are not amenable to therapy and have a dismal prognosis with low survival rates. Despite representing different tumor entities, treatment for both malignancies relies on cytotoxic chemotherapy that has not considerably changed for the past decades. The genomic background has been extensively studied and found to comprise inactivation of p53 and RB1 in case of SCLC and EWSR1/FLI1 rearrangement in case of ES resulting in aggressive tumors in adults with heavy tobacco consumption and as bone tumor in juveniles, respectively. New therapeutic modalities are urgently needed to improve the outcomes of both tumor entities, especially in patients with metastatic disease or recurrences. This review summarizes the common cell biologic and clinical characteristics of difficult-to-treat SCLC and ES and discusses their refractoriness and options to improve the therapeutic efficacy.

Methods

PubMed and Euro PMC were searched from January 1^st, 2012 to January 16^th, 2022 using the following key words: "SCLC", "Ewing´s sarcoma", "Genomics" and "Chemoresistance" as well as own work.

Key Content and Findings

Therapy of SCLC and ES involves the use of undirected cytotoxic drugs in multimodal chemotherapy and administration of topotecan for 2^nd line SCLC regimens. Despite highly aggressive chemotherapies, outcomes are dismal for patients with disseminated tumors. A host of unrelated drugs and targeted therapeutics have failed to result in progress for the patients and the underlying mechanisms of chemoresistance are still not clear. Identification of chemoresistance-reversing modulators in vitro and patient-derived xenografts of SCLC and ES has not translated into new therapies.

Conclusions

The global chemoresistance of SCLC and ES may be explained by physiological resistance at the tumor level and formation of larger spheroids that contain quiescent and hypoxic tumor cells in regions that occlude therapeutics. This type of chemoresistance is difficult to overcome and prevent the accumulation of effective drug concentration at the tumor cell level to a significant degree leaving therapeutic interventions of any kind ineffective.

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

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

Cell Lines of Circulating Tumor Cells: What Is Known and What Needs to Be Resolved

The importance of circulating tumor cells (CTC) is well recognized. However, the biological characteristics of CTC in the bloodstream have not yet been examined in detail, due to the limited number of CTC cell lines currently available. Thirty-nine CTC cell lines were reported by 2021. For successful cell culturing, these CTC cell lines were reviewed. Previous studies on short-term cultures of CTC also analyzed approaches for establishing the long-term culture of CTC. Negative selection, hypoxic conditions, three-dimensional conditions, and careful management are preferable for the long-term culture of CTC. However, the establishment of CTC cell lines is dependent on the specific characteristics of each cell type. Therefore, a method to establish CTC cell lines has not yet been developed. Further efforts are needed to resolve this issue.

Epithelial-to-Mesenchymal Plasticity in Circulating Tumor Cell Lines Sequentially Derived from a Patient with Colorectal Cancer

Simple Summary

Metastasis is a complex dynamic multistep process; however, our knowledge is still limited. Very few circulating tumor cells (CTCs) are metastatic precursor cells and represent the intermediate stage of metastasis. Epithelial–mesenchymal plasticity (EMP) has crucial roles in tissue development and homeostasis, and also in metastasis formation. In this study, we explored the EMP phenotype of a unique series of CTC lines, obtained from a patient with colon cancer during the disease course and treatment, by detecting markers involved in the epithelial–mesenchymal and mesenchymal–epithelial (MET) transitions. This study shows that these colon CTC lines have acquired only few mesenchymal features to migrate and intravasate, whereas an increase of MET-related markers was observed, suggesting that metastasis-competent CTCs need to revert quickly to the epithelial phenotype to reinitiate a tumor at a distant site.

Abstract

Metastasis is a complicated and only partially understood multi-step process of cancer progression. A subset of cancer cells that can leave the primary tumor, intravasate, and circulate to reach distant organs are called circulating tumor cells (CTCs). Multiple lines of evidence suggest that in metastatic cancer cells, epithelial and mesenchymal markers are co-expressed to facilitate the cells’ ability to go back and forth between cellular states. This feature is called epithelial-to-mesenchymal plasticity (EMP). CTCs represent a unique source to understand the EMP features in metastatic cascade biology. Our group previously established and characterized nine serial CTC lines from a patient with metastatic colon cancer. Here, we assessed the expression of markers involved in epithelial–mesenchymal (EMT) and mesenchymal–epithelial (MET) transition in these unique CTC lines, to define their EMP profile. We found that the oncogenes MYC and ezrin were expressed by all CTC lines, but not SIX1, one of their common regulators (also an EMT inducer). Moreover, the MET activator GRHL2 and its putative targets were strongly expressed in all CTC lines, revealing their plasticity in favor of an increased MET state that promotes metastasis formation.

eIF3a R803K mutation mediates chemotherapy resistance by inducing cellular senescence in small cell lung cancer

Drug resistance in small cell lung cancer (SCLC) significantly affects the efficacy of chemotherapy treatment. However, due to the lack of tumor tissue samples, especially serial tumor samples during chemotherapy, the mechanism of chemotherapy resistance has not been fully studied. Circulating tumor DNA, which can be obtained in a noninvasive manner, can complement tumor sampling approaches for research in this field. We identified an SCLC patient with acquired drug resistance from 52 SCLC patients for whom follow-up data were available. By comparing somatic mutations in circulating tumor DNA before and after chemotherapy, for the first time, we found that the somatic mutation eIF3A R803K may be related to acquired chemotherapy resistance. Then, the association between the eIF3A R803K mutation and chemotherapy resistance was confirmed by samples from 254 lung cancer patients receiving chemotherapy. We found that the eIF3a R803K mutation weakened the proliferation ability of tumor cells but increased their resistance to chemotherapy. Further studies revealed that the eIF3A R803K mutation promotes cellular senescence. In addition, fisetin showed a synergistic effect with chemotherapy in eIF3A R803K mutant cells. These results suggest that the eIF3A R803K somatic mutation has the potential to predict chemotherapy resistance in SCLC. Moreover, the eIF3A R803K mutation promotes chemotherapy resistance by inducing senescence. Furthermore, a senolytic drug, fisetin, can reverse chemotherapy resistance mediated by the eIF3A R803K mutation.

Diving into the Pleural Fluid: Liquid Biopsy for Metastatic Malignant Pleural Effusions

Simple Summary

Malignant pleural effusion is a common complication arising as the natural progression of many tumors, such as lung cancer. When this occurs, the common protocol consists of analyzing the pleural fluid for the presence of malignant cells. However, on many occasions no malignant cells are found despite a clear suspicion of cancer. Thus, the current diagnostic methodology is imperfect and more precise methods for the identification of malignancy are needed. Nonetheless, these methods are often invasive, which may be counterproductive, especially for patients with poor health condition. These concerns have made clinicians consider alternative non-invasive strategies to diagnose cancer using the generally abundant pleural fluid (e.g., liquid biopsy). Thus, a liquid sample can be analyzed for the presence of cancer footprints, such as circulating malignant cells and tumor nucleic acids. Herein, we review the literature for studies considering pleural fluid as a successful source of liquid biopsy.

Abstract

Liquid biopsy is emerging as a promising non-invasive diagnostic tool for malignant pleural effusions (MPE) due to the low sensitivity of conventional pleural fluid (PF) cytological examination and the difficulty to obtain tissue biopsies, which are invasive and require procedural skills. Currently, liquid biopsy is increasingly being used for the detection of driver mutations in circulating tumor DNA (ctDNA) from plasma specimens to guide therapeutic interventions. Notably, malignant PF are richer than plasma in tumor-derived products with potential clinical usefulness, such as ctDNA, micro RNAs (miRNAs) and long non-coding RNAs (lncRNAs), and circulating tumor cells (CTC). Tumor-educated cell types, such as platelets and macrophages, have also been added to this diagnostic armamentarium. Herein, we will present an overview of the role of the preceding biomarkers, collectively known as liquid biopsy, in PF samples, as well as the main technical approaches used for their detection and quantitation, including a proper sample processing. Technical limitations of current platforms and future perspectives in the field will also be addressed. Using PF as liquid biopsy shows promise for use in current practice to facilitate the diagnosis and management of metastatic MPE.

Short-Term Ex Vivo Culture of CTCs from Advance Breast Cancer Patients: Clinical Implications

Simple Summary

Circulating tumor cells (CTCs) are responsible for metastasis, they represent tumor biology and have also predictive value for therapy monitoring and prognosis of metastatic breast cancer patients. In the blood, CTCs are found in low frequency and a small percentage of them survive. Therefore, achieving their expansion in vitro will allow performing characterization and functional analysis. In this work, we used growth factors and Nanoemulsions to support CTCs culture. We have seen that the CTCs subpopulation capable of ex vivo expanding presented mesenchymal and stem characteristics and loss of epithelial markers. Besides, CTC culture predicted progression-free survival.

Abstract

Background: Circulating tumor cells (CTC) have relevance as prognostic markers in breast cancer. However, the functional properties of CTCs or their molecular characterization have not been well-studied. Experimental models indicate that only a few cells can survive in the circulation and eventually metastasize. Thus, it is essential to identify these surviving cells capable of forming such metastases. Methods: We isolated viable CTCs from 50 peripheral blood samples obtained from 35 patients with advanced metastatic breast cancer using RosetteSep^TM for ex vivo culture. The CTCs were seeded and monitored on plates under low adherence conditions and with media supplemented with growth factors and Nanoemulsions. Phenotypic analysis was performed by immunofluorescence and gene expression analysis using RT-PCR and CTCs counting by the Cellsearch^® system. Results: We found that in 75% of samples the CTC cultures lasted more than 23 days, predicting a shorter Progression-Free Survival in these patients, independently of having ≥5 CTC by Cellsearch^®. We also observed that CTCs before and after culture showed a different gene expression profile. Conclusions: the cultivability of CTCs is a predictive factor. Furthermore, the subset of cells capable of growing ex vivo show stem or mesenchymal features and may represent the CTC population with metastatic potential in vivo.

Circulating tumor cells as a promising target for individualized drug susceptibility tests in cancer therapy

Circulating tumor cells (CTCs) play a crucial role in metastasis and became an emerging topic in today's cancer research. In addition, the analysis of CTCs in liquid biopsies will be a valuable tool for prognosis prediction and real time therapy monitoring. The characterization of CTCs may open up a new field of treatment strategy to prevent metastasis or maintain a stable disease. In 2013, the first cell cultures of CTCs have been established in vitro. Additionally, functional studies have been successfully performed over the last years. Meanwhile, more than 300 short-term CTC cultures and 42 long-term CTC cultures from a variety of tumor entities have been described. More than 45 inhibitors have already been tested for their efficacy to target CTCs in several studies in vitro as well as in xenograft mouse models in vivo. Here, we summarize the currently available data of these inhibition experiments and their effects in targeting CTCs. The results suggest that CTCs may be useful for individualized drug susceptibility testing.

Promising Role of Circulating Tumor Cells in the Management of SCLC

Small cell lung cancer is an aggressive disease for which few therapeutic options are currently available. Although patients initially respond to therapy, they rapidly relapse. Up to today, no biomarkers for guiding treatment of SCLC patients have been identified. SCLC patients rarely undergo surgery and often the available tissue samples are inadequate for biomarker analysis. Circulating tumor cells (CTCs) are rare cells in the peripheral blood that might be used as surrogates of tissue samples. Different methodological approaches have been developed for studies of CTCs in SCLC. In addition to CTC count, which might provide prognostic and predictive information, genomic and transcriptomic analyses allow the characterization of molecular profiles of CTCs and permit the study of tumor heterogeneity. The employment of CTC-derived xenografts offers complementary information to genomic analyses and CTC enumeration about the mechanisms involved in the sensitivity/resistance to treatments. Using these approaches, CTC analysis is providing relevant information on SCLC biology that might aid in the development of personalized therapeutic strategies for SCLC patients.

Ex Vivo Expansion and Drug Sensitivity Profiling of Circulating Tumor Cells from Patients with Small Cell Lung Cancer

Simple Summary

Small cell lung cancer (SCLC) is an overly aggressive cancer characterized by rapid growth, early metastatic spread, and consequently reducing overall survival. As cancer manifestations can differ uniquely between various types, the rapid proliferation of circulating tumor cells (CTC) originating from SCLC was an adequate sample resource to aid the headway in our drug screening technique. With biomarker detection of liquid biopsy as an emerging tool to assist decision-making in personalized cancer pharmacotherapy. In this study, we developed a rapid and reproducible system for preclinical drug testing via the use of a unique CTCs expansion protocol. The expanded CTCs from SCLC formed multiple types of tumorsphere structures and expressed SCLC-specific tumor markers. The drug sensitivity assessment gathered from in vitro expansion of CTCs was able to generate positive clinical therapeutic outcomes. Thus, SCLC patient-derived CTC spheroids are a useful resource for biomarker development and drug sensitivity assessment providing “real-world” therapeutic response circumstances.

Abstract

Small cell lung cancer (SCLC) represents one of the most aggressive malignancies among cancer types. Not only tumor sample availability is limited, but also the ability for tumor cells to rapidly acquire drug resistance are the rate-limiting bottlenecks for overall survival in current clinical settings. A liquid biopsy capable of capturing and enriching circulating tumor cells (CTCs), together with the possibility of drug screening, is a promising solution. Here, we illustrate the development of a highly efficient ex vivo CTC expansion system based on binary colloidal crystals substrate. Clinical samples were enrolled from 22 patients with SCLC in the study. The CTCs were enriched and expanded from the collected peripheral blood samples. Expanded cells were analyzed for protein expression and observed for drug sensitivity with the use of immunofluorescence and ATP titer evaluation, respectively. Successful CTC spheroid proliferation was established after 4 weeks within 82% of all the collected peripheral blood samples from enrolled patients. Upon immunofluorescence analysis, the enriched cells showed positive markers for EpCAM, TTF-1, synaptophysin and negative for CD45. Additionally, the expanded CTCs demonstrated marked heterogeneity in the expression of E-cadherin and N-cadherin. In a preliminary case series, the drug sensitivity of patient-derived CTC to cisplatin and etoposide was studied to see the correlation with the corresponding therapeutic outcome. In conclusion, our study demonstrates that it is possible to efficiently expand CTCs from SCLC within a clinically relevant time frame; the biomarker information generated from enriched CTCs can assist the selection of effective drugs and improve disease outcome.

Epithelial Cell Adhesion Molecule: An Anchor to Isolate Clinically Relevant Circulating Tumor Cells

In the last few decades, the epithelial cell adhesion molecule (EpCAM) has received increased attention as the main membrane marker used in many enrichment technologies to isolate circulating tumor cells (CTCs). Although there has been a great deal of progress in the implementation of EpCAM-based CTC detection technologies in medical settings, several issues continue to limit their clinical utility. The biology of EpCAM and its role are not completely understood but evidence suggests that the expression of this epithelial cell-surface protein is crucial for metastasis-competent CTCs and may not be lost completely during the epithelial-to-mesenchymal transition. In this review, we summarize the most significant advantages and disadvantages of using EpCAM as a marker for CTC enrichment and its potential biological role in the metastatic cascade.

Single-cell analyses reveal increased intratumoral heterogeneity after the onset of therapy resistance in small-cell lung cancer

The natural history of small cell lung cancer (SCLC) includes rapid evolution from chemosensitivity to chemoresistance, although mechanisms underlying this evolution remain obscure due to scarcity of post-relapse tissue samples. We generated circulating tumor cell (CTC)-derived xenografts (CDXs) from SCLC patients to study intratumoral heterogeneity (ITH) via single-cell RNAseq of chemo-sensitive and -resistant CDXs and patient CTCs. We found globally increased ITH including heterogeneous expression of therapeutic targets and potential resistance pathways, such as EMT, between cellular subpopulations following treatment-resistance. Similarly, serial profiling of patient CTCs directly from blood confirmed increased ITH post-relapse. These data suggest that treatment-resistance in SCLC is characterized by coexisting subpopulations of cells with heterogeneous gene expression leading to multiple, concurrent resistance mechanisms. These findings emphasize the need for clinical efforts to focus on rational combination therapies for treatment-naïve SCLC tumors to maximize initial responses and counteract the emergence of ITH and diverse resistance mechanisms.

[Research Advances in the Mechanism of Invasion and Metastasis of Circulating Tumor Cells in Lung Cancer]

近年来，随着液体活检技术兴起，循环肿瘤细胞（circulating tumor cell, CTC）在癌症患者的早期诊断、疗效评估及预后评价等方面显示出重要的价值。CTC的产生导致肿瘤发生远处转移及患者的预后不良。因此，阐明CTC的产生、进入循环系统及其免疫逃逸的机制尤为重要。目前，精准诊疗成为提高肺癌患者预后的重要努力方向。针对肺癌CTC有望为肺癌精准诊疗提供有力的理论依据与重要手段。现对上述热点问题的最新研究进展进行综述。

Pre-clinical models of small cell lung cancer and the validation of therapeutic targets

Introduction: Small-cell lung cancer (SCLC) is an aggressive form of lung cancer that has a dismal prognosis. One of the factors hindering therapeutic developments for SCLC is that most SCLC is not surgically resected resulting in a paucity of material for analysis. To address this, significant efforts have been made by investigators to develop pre-clinical models of SCLC allowing for downstream target identification in this difficult to treat cancer.Areas covered: In this review, we describe the current pre-clinical models that have been developed to interrogate SCLC, and outline the benefits and limitations associated with each. Using examples we show how each has been used to (i) improve our knowledge of this intractable cancer, and (ii) identify and validate potential therapeutic targets that (iii) are currently under development and testing within the clinic.Expert opinion: The large numbers of preclinical models that have been developed have dramatically improved the ways in which we can examine SCLC and test therapeutic targets/interventions. The newer models are rapidly providing novel avenues for the design and testing of new therapeutics. Despite this many of these models have inherent flaws that limit the possibility of their use for individualized therapy decision-making for SCLC.

Epithelial-mesenchymal transition may be involved in the immune evasion of circulating gastric tumor cells via downregulation of ULBP1

Background

Increasing numbers of studies have demonstrated that circulating tumor cells (CTCs) undergo a phenotypic change termed epithelial‐mesenchymal transition (EMT), and researchers have proposed that EMT might provide CTCs with increased potential to survive in the different microenvironments encountered during metastasis through various ways, such as by increasing cell survival and early colonization. However, the exact role of EMT in CTCs remains unclear.

Methods

In this study, we identified CTCs of 41 patients with gastric cancer using Cyttel‐CTC and im‐FISH (immune‐fluorescence in situ hybridization) methods, and tested the expression of EMT markers and ULBP1 (a major member of the NKG2D—natural killer [NK] group 2 member D—ligand family) on CTCs. Moreover, we investigated the relationship between the expression of EMT markers and ULBP1 on CTCs and gastric cancer cell lines.

Results

Our results showed that the CTCs of gastric cancer patients exhibited three EMT marker subtypes, and that the expression of ULBP1 was significantly lower on mesenchymal phenotypic CTCs (M⁺CTCs) than on epithelial phenotypic CTCs (E⁺CTCs). EMT induced by TGF‐β in vitro produced a similar phenomenon, and we therefore proposed that EMT might be involved in the immune evasion of CTCs from NK cells by altering the expression of ULBP1.

Conclusions

Our study indicated that EMT might play a vital role in the immune invasion of CTCs by regulating the expression of ULBP1 on CTCs. These findings could provide potential strategies for targeting the immune evasion capacity of CTCs.

Cancer stem cells and their unique role in metastatic spread

Cancer stem cells (CSC) possess abilities generally associated with embryonic or adult stem cells, especially self-renewal and differentiation, but also dormancy and cellular plasticity that allow adaption to new environmental circumstances. These abilities are ideal prerequisites for the successful establishment of metastasis. This review highlights the role of CSCs in every step of the metastatic cascade from cancer cell invasion into blood vessels, survival in the blood stream, attachment and extravasation as well as colonization of the host organ and subsequent establishment of distant macrometastasis.

Diagnostic accuracy of E-cadherin for malignanteffusions: a systematic review and meta-analysis

BACKGROUND

The differential diagnosis of malignant effusion remains a clinical challenge. We aim to summarise all relevant literature studies in order to determine the overall clinical value of E-cadherin in the diagnosis of malignant effusion by meta-analysis.

METHODS

PubMed, the Cochrane Library Database, Medline (Ovid), Web of Science, CNKI, WANFANG and WEIPU databases are thoroughly searched up to 15 March2018. The calculated pooled sensitivity, specificity, likelihood ratio (LR), diagnostic OR(DOR) and the summary receiver operating characteristic (SROC) curve were plotted.

RESULTS

A total of 15 studies were included in the analysis. The sensitivity and specificity of E-cadherin in the diagnosis of malignant effusion were determined to be high, with a sensitivity of 0.83(95%CI0.79 to 0.87) and a specificity of 0.96(95%CI0.90 to 0.98). The positive LR was determined to be 21.10(95%CI 8.54 to 52.11), the negative LR was determined to be 0.17(95% CI 0.14 to 0.22) and the DOR was determined to be 121.34(95%CI 49.11 to 299.80). The SROC curve exhibited a high overall diagnostic, with the area under the curve measured to be 0.91(95% CI 0.89 to 0.93). Subgroup analysis showed the method (cell blocks or smears), sample size (≥100 or<100), geographical location (Asia, Europe or USA) and impact factor of each article (≥3 or<3) were not the sources of overall heterogeneity.

CONCLUSION

E-cadherin exhibits very good diagnostic accuracy for the diagnosis for malignant effusion; thus, it can be helpful in the process of clinical decisions.

A Model-System to Address the Impact of Phenotypic Heterogeneity and Plasticity on the Development of Cancer Therapies

The main challenges in developing effective anti-cancer therapies stem from the highly complex and heterogeneous nature of cancer, including the presence of multiple genetically-encoded and environmentally-induced cancer cell phenotypes within an individual. This diversity can make the development of successful treatments difficult as different phenotypes can have different responses to the same treatment. The lack of model-systems that can be used to simultaneously test the effect of therapies on multiple distinct phenotypic states further contributes to this problem. To mitigate these challenges, we suggest that in vitro model-systems that consist of several genetically-related but phenotypically distinct populations can be used as proxies for the several phenotypes (including adherent and circulating tumor cells) present in a patient with advanced disease. As proof of concept, we have developed such a model and showed that different phenotypes had different responses to the same challenge (i.e., a change in extracellular pH) both in terms of sensitivity and phenotypic plasticity. We suggest that similar model-systems could be developed and used when designing novel therapeutic strategies, to address the potential impact of phenotypic heterogeneity and plasticity of cancer on the development of successful therapies. Specifically, the effect of a therapy should be considered on more than one cancer cell phenotype (to increase its effectiveness), and both cell viability as well as changes in phenotypic state (to address potential plastic responses) should be evaluated. Although we are aware of the limitations of in vitro systems, we believe that the use of established cell lines that express multiple phenotypes can provide invaluable insights into the complex interplay between therapies and cancer's heterogeneous and plastic nature.

Effects of salinomycin and niclosamide on small cell lung cancer and small cell lung cancer circulating tumor cell lines

Tumor dissemination and recurrence is attributed to highly resistant cancer stem cells (CSCs) which may constitute a fraction of circulating tumor cells (CTCs). Small cell lung cancer (SCLC) constitutes a suitable model to investigate the relation of CTCs and CSCs due to rapid tumor spread and a high number of CTCs. Expansion of five SCLC CTC lines (BHGc7, 10, 16, 26 and UHGc5) in vitro at our institution allowed for the analysis of CSC markers and cytotoxicity of the CSC-selective drugs salinomycin and niclosamide against CTC single cell suspensions or CTC spheroids/ tumorospheres (TOS). Salinomycin exerted dose-dependent cytotoxicity against the SCLC lines but, with exception of BHGc7 TOS, there was no markedly enhanced activity against TOS. Similarly, niclosamide exhibits high activity against BHGc7 TOS and UHGc5 TOS but not against the other CTC spheroids. High expression of the CSC marker CD133 was restricted to three SCLC tumor lines and the BHGc10 CTC line. All SCLC CTCs are CD24-positive but lack expression of CD44 and ABCG2 in contrast to the SCLC tumor lines which show a phenotype more similar to that of CSCs. The stem cell marker SOX2 was found in all CTC lines and SCLC GLC14/16, whereas elevated expression of Oct-3/4 and Nanog was restricted to BHGc26 and UHGc5. In conclusion, the SCLC CTCs established from patients with relapsed disease lack a typical CSC phenotype in respect to chemosensitivity to CSC-selective drugs, surface markers, expression of pluripotent stem cell and transcription factors.

Cathepsin B defines leader cells during the collective invasion of salivary adenoid cystic carcinoma

Cathepsin B (CTSB) has been reported to be involved in cancer metastasis by altering extracellular matrix (ECM) remodeling and facilitating invasion. However, the contribution of CTSB to collective cell invasion in salivary adenoid cystic carcinoma (SACC) and the underlying mechanisms remain unclear. The present study demonstrated that collective cell invasion is commonly observed in SACC without a complete epithelial-mesenchymal transition signature. CTSB was found to be overexpressed in the invasive front of SACC compared to the tumor center, and was associated with a poor prognosis of patients with SACC. Subsequently, a 3D spheroid invasion assay was established in order to recapitulate the collective cell invasion of SACC and the results revealed that CTSB was only expressed in leader cells. The knockdown of CTSB by siRNA inhibited the migration and invasion of SACC-83 cells and impaired the formation of leader cells. CTSB knockdown also disrupted cytoskeletal organization, altered cell morphology and inhibited ECM remodeling by downregulating matrix metalloproteinase-9, focal adhesion kinase and Rho/ROCK function. Therefore, the present study provides evidence that CTSB may define leader cells in SACC and is required for collective cell invasion as a potential key regulator of ECM remodeling.

Expression of Proteolytic Enzymes by Small Cell Lung Cancer Circulating Tumor Cell Lines

Small cell lung cancer (SCLC) is an aggressive type of lung cancer which disseminates vigorously and has a dismal prognosis. Metastasis of SCLC is linked to an extremely high number of circulating tumor cells (CTCs), which form chemoresistant spheroids, termed tumorospheres. Intravasation and extravasation during tumor spread requires the activity of a number of proteases to disintegrate the stroma and vascular tissue. Generation of several permanent SCLC CTC lines allowed us to screen for the expression of 35 proteases using Western blot arrays. Cell culture supernatants of two CTC lines, namely BHGc7 and 10, were analyzed for secreted proteases, including matrix metalloproteinases (MMPs), ADAM/TS, cathepsins, kallikreins, and others, and compared to proteases expressed by SCLC cell lines (GLC14, GLC16, NCI-H526 and SCLC26A). In contrast to NCI-H526 and SCLC26A, MMP-9 was highly expressed in the two CTC lines and in GLC16 derived of a relapse. Furthermore, cathepsins (S, V, X/Z/P, A and D) were highly expressed in the CTC lines, whereas ADAM/TS and kallikreins were not detectable. In conclusion, SCLC CTCs express MMP-9 and a range of cathepsins for proteolysis and, aside from tissue degradation, these enzymes are involved in cell signaling, survival, and the chemoresistance of tumor cells.

Hybrid epithelial/mesenchymal phenotypes promote metastasis and therapy resistance across carcinomas

Cancer metastasis and therapy resistance are the major unsolved clinical challenges, and account for nearly all cancer-related deaths. Both metastasis and therapy resistance are fueled by epithelial plasticity, the reversible phenotypic transitions between epithelial and mesenchymal phenotypes, including epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET). EMT and MET have been largely considered as binary processes, where cells detach from the primary tumor as individual units with many, if not all, traits of a mesenchymal cell (EMT) and then convert back to being epithelial (MET). However, recent studies have demonstrated that cells can metastasize in ways alternative to traditional EMT paradigm; for example, they can detach as clusters, and/or occupy one or more stable hybrid epithelial/mesenchymal (E/M) phenotypes that can be the end point of a transition. Such hybrid E/M cells can integrate various epithelial and mesenchymal traits and markers, facilitating collective cell migration. Furthermore, these hybrid E/M cells may possess higher tumor-initiation and metastatic potential as compared to cells on either end of the EMT spectrum. Here, we review in silico, in vitro, in vivo and clinical evidence for the existence of one or more hybrid E/M phenotype(s) in multiple carcinomas, and discuss their implications in tumor-initiation, tumor relapse, therapy resistance, and metastasis. Together, these studies drive the emerging notion that cells in a hybrid E/M phenotype may occupy 'metastatic sweet spot' in multiple subtypes of carcinomas, and pathways linked to this (these) hybrid E/M state(s) may be relevant as prognostic biomarkers as well as a promising therapeutic targets.

Will liquid biopsies improve outcomes for patients with small-cell lung cancer?

Small-cell lung cancer (SCLC) is an aggressive tumour that seeds metastases early with dismal outcomes. As expected from a disease that is closely associated with smoking, mutation burden in SCLC is high. Intratumoral and intertumoral heterogeneity is a substantial obstacle to successful treatment and the SCLC genomic landscape reveals few targets that are readily druggable. Chemotherapy elicits responses in most patients with SCLC, but their effects are short lived. Multiple clinical trials have been unsuccessful in showing positive survival outcomes and biomarkers to select patients and monitor responses to novel targeted treatments have been lacking, not least because acquisition of tumour biopsies, especially during relapse after chemotherapy, is a substantial challenge. Liquid biopsies via blood sampling in SCLC, notably circulating tumour cells and circulating free tumour DNA can be readily and repeatedly accessed, and are beginning to yield promising data to inform SCLC biology and patient treatment. Primary cell cultures and preclinical mouse models can also be derived from the relatively plentiful SCLC circulating tumour cells providing a tractable platform for SCLC translational research and drug development.

In Vitro Model-Systems to Understand the Biology and Clinical Significance of Circulating Tumor Cell Clusters

The isolation of clusters of circulating tumor cells (CTCs) from cancer patients has recently challenged the accepted view that the initiation of secondary tumors during metastasis involves the dissemination of individual cancer cells. As such clusters appear to be more aggressive than single tumor cells, CTC clusters are now considered a main player in the metastatic process, and many studies are exploring their diagnostic, prognostic, and clinical significance. However, several technical challenges limit advances in this area. Here, we suggest the use of established cancer cell lines that grow as cell clusters in suspension as a complementary approach that can help in understanding the biology of CTC clusters and their clinical significance. We argue that the many similarities between these "surrogate" clusters and the CTC clusters isolated from patients (e.g., in terms of size, morphology, heterogeneous expression of epithelial and mesenchymal markers, and type of cell-cell junctions) make these cell lines ideal systems for the development of strategies aimed at preventing or slowing down the metastatic process by targeting CTC clusters.

Beyond cell-cell adhesion: Plakoglobin and the regulation of tumorigenesis and metastasis

Plakoglobin (also known as? -catenin) is a member of the Armadillo family of proteins and a paralog of β -catenin. Plakoglobin is a component of both the adherens junctions and desmosomes, and therefore plays a vital role in the regulation of cell-cell adhesion. Similar to β -catenin, plakoglobin is capable of participating in cell signaling in addition to its role in cell-cell adhesion. In this context, β -catenin has a well-documented oncogenic potential as a component of the Wnt signaling pathway. In contrast, while some studies have suggested a tumor promoting activity of plakoglobin in a cell/malignancy specific context, it generally acts as a tumor/metastasis suppressor. How plakoglobin acts as a growth/metastasis inhibitory protein has remained, until recently, unclear. Recent evidence suggests that plakoglobin may suppress tumorigenesis and metastasis by multiple mechanisms, including the suppression of oncogenic signaling, interactions with various proteins involved in tumorigenesis and metastasis, and the regulation of the expression of genes involved in these processes. This review is primarily focused on various mechanisms by which plakoglobin may inhibit tumorigenesis and metastasis.

Transcription factor E2F1 promotes EMT by regulating ZEB2 in small cell lung cancer

BACKGROUND

Epithelial-mesenchymal transition (EMT) is an early event in tumour invasion and metastasis, and widespread and distant metastasis at early stages is the typical biological behaviour in small cell lung cancer (SCLC). Our previous reports showed that high expression of the transcription factor E2F1 was involved in the invasion and metastasis of SCLC, but the role of E2F1 in the process of EMT in SCLC is unknown.

METHODS

Immunohistochemistry was performed to evaluate the expressions of EMT related markers. Immunofluorescence was used to detect the expressions of cytoskeletal proteins and EMT related markers when E2F1 was silenced in SCLC cell lines. Adenovirus containing shRNA against E2F1 was used to knock down the E2F1 expression, and the dual luciferase reporter system was employed to clarify the regulatory relationship between E2F1 and ZEB2.

RESULTS

In this study, we observed the remodelling of cytoskeletal proteins when E2F1 was silenced in SCLC cell lines, indicating that E2F1 was involved in the EMT in SCLC. Depletion of E2F1 promoted the expression of epithelial markers (CDH1 and CTNNB1) and inhibited the expression of mesenchymal markers (VIM and CDH2) in SCLC cell lines, verifying that E2F1 promotes EMT occurrence. Next, the mechanism by which E2F1 promoted EMT was explored. Among the CDH1 related inhibitory transcriptional regulators ZEB1, ZEB2, SNAI1 and SNAI2, the expression of ZEB2 was the highest in SCLC tissue samples and was highly consistent with E2F1 expression. ChIP-seq data and dual luciferase reporter system analysis confirmed that E2F1 could regulate ZEB2 gene expression.

CONCLUSION

Our data supports that E2F1 promotes EMT by regulating ZEB2 gene expression in SCLC.

Circulating tumor cell interactions with macrophages: implications for biology and treatment

Cancer and metastasis are closely associated with inflammation. Macrophages are important effector cells in enhancing tumor proliferation, invasion and providing protection against the immune system. Despite advanced knowledge of tumor-macrophage interactions, the role of macrophages in emergence and invasion of circulating tumor cells (CTCs) is not known. A series of six CTC cell lines have been derived from blood of patients with extensive disease small cell lung cancer (ED-SCLC) in our lab, most likely representing a homogenous cell population of the actual metastasis-initiating cells (MIC) of CTCs. SCLC has an unfavorable prognosis due to rapid dissemination and early chemoresistant relapses. SCLC CTCs recruit macrophages and elicit secretion of various cytokines and the six CTC lines express chitinase-3-like-1 (CHI3L1), vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP9) in abundance. CHI3L1 is cytokine/growth factor expressed in inflammation and cancer and found to be correlated to metastasis and a dismal prognosis. In conclusion, SCLC CTCs have acquired the essential means for aggressiveness and invasion in a tumor microenvironment specifically shaped by macrophages and inflammation.

Epithelial requirement for in vitro proliferation and xenograft growth and metastasis of MDA-MB-468 human breast cancer cells: oncogenic rather than tumor-suppressive role of E-cadherin

BACKGROUND

Epithelial-to-mesenchymal transition (EMT) is associated with downregulated E-cadherin and frequently with decreased proliferation. Proliferation may be restored in secondary metastases by mesenchymal-to-epithelial transition (MET). We tested whether E-cadherin maintains epithelial proliferation in MDA-MB-468 breast cancer cells, facilitating metastatic colonization in severe combined immunodeficiency (SCID) mice.

METHODS

EMT/MET markers were assessed in xenograft tumors by immunohistochemistry. Stable E-cadherin manipulation was effected by transfection and verified by Western blotting, immunocytochemistry, and quantitative polymerase chain reaction (qPCR). Effects of E-cadherin manipulation on proliferation and chemomigration were assessed in vitro by performing sulforhodamine B assays and Transwell assays, respectively. Invasion was assessed by Matrigel outgrowth; growth in vivo was assessed in SCID mice; and EMT status was assessed by qPCR. Hypoxic response of E-cadherin knockdown cell lines was assessed by qPCR after hypoxic culture. Repeated measures analysis of variance (ANOVA), one- and two-way ANOVA with posttests, and paired Student's t tests were performed to determine significance (p < 0.05).

RESULTS

EMT occurred at the necrotic interface of MDA-MB-468 xenografts in regions of hypoxia. Extratumoral deposits (vascular and lymphatic inclusions, local and axillary nodes, and lung metastases) strongly expressed E-cadherin. MDA-MB-468 cells overexpressing E-cadherin were more proliferative and less migratory in vitro, whereas E-cadherin knockdown (short hairpin CDH1 [shCDH1]) cells were more migratory and invasive, less proliferative, and took longer to form tumors. shCDH1-MDA-MB-468 xenografts did not contain the hypoxia-induced necrotic areas observed in wild-type (WT) and shSCR-MDA-MB-468 tumors, but they did not exhibit an impaired hypoxic response in vitro. Although vimentin expression was not stimulated by E-cadherin knockdown in 2D or 3D cultures, xenografts of these cells were globally vimentin-positive rather than exhibiting regional EMT, and they expressed higher SNA1 than their in vitro counterparts. E-cadherin suppression caused a trend toward reduced lung metastasis, whereas E-cadherin overexpression resulted in the reverse trend, consistent with the increased proliferation rate and predominantly epithelial phenotype of MDA-MB-468 cells outside the primary xenograft. This was also originally observed in WT xenografts. Furthermore, we found that patients with breast cancer that expressed E-cadherin were more likely to have metastases.

CONCLUSIONS

E-cadherin expression promotes growth of primary breast tumors and conceivably the formation of metastases, supporting a role for MET in metastasis. E-cadherin needs to be reevaluated as a tumor suppressor.

Small cell lung cancer: model of circulating tumor cell tumorospheres in chemoresistance

Small cell lung cancer (SCLC) represents 15% of lung cancers and is characterized by early dissemination, development of chemoresistance and a poor prognosis. A host of diverse drugs failed invariably and its mechanisms of global chemoresistance have not been characterized so far. SCLC represents the prototype of an aggressive and highly metastatic tumor which is ultimately refractory to any treatment. High numbers of circulating tumor cells (CTCs) allowed us to establish 5 CTC cell lines (BHGc7, 10, 16, 26 and UHGc5) from patients with recurrent SCLC. These cell lines exhibit the typical SCLC markers and CTCs of all patients developed spontaneously large multicellular aggregates, termed tumorospheres. Ki67 and carbonic anhydrase 9 (CAIX) staining of tumorosphere sections revealed quiescent and hypoxic cells, respectively. Accordingly, comparison of the chemosensitivity of CTC single cell suspensions with tumorospheres demonstrated increased resistance of the clusters against chemotherapeutics commonly used for treatment of SCLC. Therefore, global chemoresistance of relapsing SCLC seems to rely on formation of large tumorospheres which reveal limited accessibility, lower growth fraction and hypoxic conditions. Since similar tumor spheroids were found in other tumor types, SCLC seems to represent a unique tumor model to study the association of CTCs, metastasis and drug resistance.

Isolation of Phenotypically Distinct Cancer Cells Using Nanoparticle-Mediated Sorting

Isolating subpopulations of heterogeneous cancer cells is an important capability for the meaningful characterization of circulating tumor cells at different stages of tumor progression and during the epithelial-to-mesenchymal transition. Here, we present a microfluidic device that can separate phenotypically distinct subpopulations of cancer cells. Magnetic nanoparticles coated with antibodies against the epithelial cell adhesion molecule (EpCAM) are used to separate breast cancer cells in the microfluidic platform. Cells are sorted into different zones on the basis of the levels of EpCAM expression, which enables the detection of cells that are losing epithelial character and becoming more mesenchymal. The phenotypic properties of the isolated cells with low and high EpCAM are then assessed using matrix-coated surfaces for collagen uptake analysis, and an NAD(P)H assay that assesses metabolic activity. We show that low-EpCAM expressing cells have higher collagen uptake and higher folate-induced NAD(P)H responses compared to those of high-EpCAM expressing cells. In addition, we tested SKBR3 cancer cells undergoing chemically induced hypoxia. The induced cells have reduced expression of EpCAM, and we find that these cells have higher collagen uptake and NAD(P)H metabolism relative to noninduced cells. This work demonstrates that nanoparticle-mediated binning facilitates the isolation of functionally distinct cell subpopulations and allows surface marker expression to be associated with invasiveness, including collagen uptake and metabolic activity.

Epithelial, mesenchymal and hybrid epithelial/mesenchymal phenotypes and their clinical relevance in cancer metastasis

Cancer metastasis occurs through local invasion of circulating tumour cells (CTCs), intravasation, transportation to distant sites, and their extravasation followed by colonisation at secondary sites. Epithelial-mesenchymal transition (EMT) is a normal developmental phenomenon, but its aberrant activation confers tumour cells with enhanced cell motility, metastatic properties, resistant to therapies and cancer stem cell (CSC) phenotype in epithelium-derived carcinoma. Experimental studies from various research papers have been reviewed to determine the factors, which interlink cancer stemness and cellular plasticity with EMT. Although existence of CSCs has been linked with EMT, nevertheless, there are controversies with the involvement of type of tumour cells, including cells with E (epithelial) and M (mesenchymal) phenotype alone or hybrid E/M phenotype in different types of cancers. Studies on CTCs with hybrid E/M phenotypes during different stages of cancer metastasis reveal strong association with tumour -initiation potential, cellular plasticity and types of cancer cells. Cells with the hybrid E/M state are strictly controlled by phenotypic stability factors coupled to core EMT decision-making circuits, miR200/ZEB and miR-34/Snail. Understanding the regulatory functions of EMT program in cancer metastasis can help us to characterise the biomarkers of prognostic and therapeutic potential. These biomarkers when targeted may act as metastatic suppressors, inhibit cellular plasticity and stemness ability of tumour cells and can block metastatic growth.

MicroRNA-200a inhibits cell growth and metastasis by targeting Foxa2 in hepatocellular carcinoma

Background: MicroRNAs (miRNAs) are a class of endogenous, small non-coding RNAs which function as essential posttranscriptional modulators of gene expression tightly involved in a wide range of diseases, including the hepatocellular carcinoma (HCC). Here, the present study was designed to investigate the expression levels and cellular roles of miR-200a in HCC. Methods: Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) was used to detect the expression levels of miR-200a in serums and cell lines. Bioinformation analysis, the luciferase reporter assay, qRT-PCR and western blotting were employed to validate Foxa2 as a direct target gene of miR-200a. Cell proliferation, migration and invasion were assessed to identify whether miR-200a could regulate the biological behaviors of HCC cells by targeting Foxa2. Results: In this study, a low level of miR-200a was observed in patients' serums and HCC cell lines. Overexpression of miR-200a in HCC cell lines reduced cell proliferation, migration and invasion. In addition, transcription factor forkhead box A2 (Foxa2) was identified as a novel target of miR-200a and downregulated at mRNA and protein levels in miR-200a overexpressed cells. Meanwhile, restoration of Foxa2 significantly reversed the tumor suppressive effects of miR-200a. Conclusions: These findings indicate that miR-200a regulates the proliferation, migration and invasion of HCC cells by targeting Foxa2, suggesting that miR-200a may function as a potential therapeutic molecular for the diagnosis and treatment of the liver cancer.

The Significance of Epithelial-to-Mesenchymal Transition for Circulating Tumor Cells

Epithelial to mesenchymal transition (EMT) is a process involved in embryonic development, but it also plays a role in remote metastasis formation in tumor diseases. During this process cells lose their epithelial features and adopt characteristics of mesenchymal cells. Thereby single tumor cells, which dissolve from the primary tumor, are enabled to invade the blood vessels and travel throughout the body as so called "circulating tumor cells" (CTCs). After leaving the blood stream the reverse process of EMT, the mesenchymal to epithelial transition (MET) helps the cells to seed in different tissues, thereby generating the bud of metastasis formation. As metastasis is the main reason for tumor-associated death, CTCs and the EMT process are in the focus of research in recent years. This review summarizes what was already found out about the molecular mechanisms driving EMT, the consequences of EMT for tumor cell detection, and suitable markers for the detection of CTCs which underwent EMT. The research work done in this field could open new roads towards combating cancer.

Metastasis: Circulating Tumor Cells in Small Cell Lung Cancer

Small cell lung cancer (SCLC) is distinguished by excessive numbers of circulating tumor cells (CTCs) in extended and recurring disease. This malignancy has a poor prognosis due to rapid emergence of chemoradioresistant relapses after first-line chemotherapy. In vitro expansion of several CTC lines allowed for a detailed study of the contribution of these cells to metastasis. Generation of CTCs involves the establishment of co-cultures and recruitment of macrophages and specific cytokines. All cell lines show E-cadherin-positive epithelial-like cells and spontaneous assembling into very large tumorospheres. Such multicellular aggregates seem to be responsible for the observed broad resistance due to limited access to drugs, quiescent cell layers, and hypoxic cores.