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

Ex vivo identification of circulating tumor cells in peripheral blood by fluorometric "turn on" aptamer nanoparticles

The detection of the circulating tumor cells (CTCs) detached from solid tumors has emerged as a burgeoning topic for cancer diagnosis and treatment. The conventional CTC enrichment and identification mainly rely on the specific binding of the antibodies on the capture interface of the magnetic nanoparticles with the corresponding biomarkers on the cell membranes. However, these methods could easily generate false-negative results due to the extremely low concentration of CTCs and the internal heterogeneity of the tumor cells. Herein, with the aim of selectively identifying CTCs and improving the detection accuracy in peripheral blood, we designed the fluorometric "turn on" Au nanoparticles (DHANs) with the modification of a tumor-targeted moiety, dehydroascorbic acid (DHA) and a fluorometric aptamer, which could be "switched-on" by an over-expressed intracellular protein, namely hypoxia-inducible factor-1α (HIF 1α). This novel nanoformulated detection platform demonstrated the great capacity for visualizing various CTCs in peripheral blood with significantly improved detection efficiency and sensitivity. As a result, the nanoplatform has a great potential to be further applied for CTC detection in vitro or in vivo, which holds promise for extensive CTC studies.

The Tumor Microenvironment as a Driving Force of Breast Cancer Stem Cell Plasticity

Simple Summary

Breast cancer stem cells are a subset of transformed cells that sustain tumor growth and can metastasize to secondary organs. Since metastasis accounts for most cancer deaths, it is of paramount importance to understand the cellular and molecular mechanisms that regulate this subgroup of cells. The tumor microenvironment (TME) is the habitat in which transformed cells evolve, and it is composed by many different cell types and the extracellular matrix (ECM). A body of evidence strongly indicates that microenvironmental cues modulate stemness in breast cancer, and that the coevolution of the TME and cancer stem cells determine the fate of breast tumors. In this review, we summarize the studies providing links between the TME and the breast cancer stem cell phenotype and we discuss their specific interactions with immune cell subsets, stromal cells, and the ECM.

Abstract

Tumor progression involves the co-evolution of transformed cells and the milieu in which they live and expand. Breast cancer stem cells (BCSCs) are a specialized subset of cells that sustain tumor growth and drive metastatic colonization. However, the cellular hierarchy in breast tumors is rather plastic, and the capacity to transition from one cell state to another depends not only on the intrinsic properties of transformed cells, but also on the interplay with their niches. It has become evident that the tumor microenvironment (TME) is a major player in regulating the BCSC phenotype and metastasis. The complexity of the TME is reflected in its number of players and in the interactions that they establish with each other. Multiple types of immune cells, stromal cells, and the extracellular matrix (ECM) form an intricate communication network with cancer cells, exert a highly selective pressure on the tumor, and provide supportive niches for BCSC expansion. A better understanding of the mechanisms regulating these interactions is crucial to develop strategies aimed at interfering with key BCSC niche factors, which may help reducing tumor heterogeneity and impair metastasis.

High Expression of BCAR1 by Circulating Tumor Cells and Tumor Tissues Is Predictive of a Poor Prognosis of Early-Stage Lung Adenocarcinoma Potentially Due to Regulation of Epithelial-Mesenchymal Transition

OBJECTIVE

To clarify the clinical significance of breast cancer anti-estrogen resistance protein 1 (BCAR1) expression in circulating tumor cells (CTCs) in the peripheral blood and tumor tissues in patients with early stage lung adenocarcinoma (ES-LUAD).

METHODS

The study cohort included 60 patients with stage I LUAD (50 IA and 10 IB) who underwent surgery from November 2015 to November 2018 and 31 healthy controls. The expression levels of BCAR1 and markers of epithelial-mesenchymal transition (EMT) in peripheral blood CTCs were detected using CanPatrol^TM technology before surgery, and immunohistochemical analysis was used to detect BCAR1 expression in tumor tissues collected from 40 patients. The predictive power of BCAR1 expression in CTCs and tumor tissues on disease-free survival (DFS) was analyzed. The Cancer Genome Atlas (TCGA) database was used to study BCAR1 expression and overall survival as validation. The Gene Expression Profiling Interactive Analysis online tool was used to analyze the correlations between the expression levels of BCAR1 and EMT molecular markers.

RESULTS

Both the number and detection rates of BCAR1-negative CTCs and BCAR1-positive CTCs in peripheral blood of lung cancer patients were significantly higher as compared with healthy controls (p < 0.05). BCAR1-positive CTCs more commonly co-expressed both epithelial and mesenchymal markers. Kaplan-Meier analysis demonstrated that patients with BCAR1(++) CTCs in peripheral blood before surgery were more prone to recurrence or metastasis after 2 years. COX analysis showed that patients with higher abundance of BCAR1(++) CTCs had a poorer prognosis (hazard ratio [HR] = 1.712, 95% confidence interval [CI] = 1.077-2.272, p = 0.023). Furthermore, high BCAR1 expression in tumor tissues was predictive of a poor prognosis (HR = 2.654, 95% CI = 1.239-5.686, p = 0.012), as validated by TCGA database (HR = 2.217, 95% CI = 1.069-4.595, p = 0.032). In addition, BCAR1 expression in LUAD tissues from TCGA was significantly positively correlated with the expression of both epithelial markers (e.g., ck8/18/19) and mesenchymal markers (e.g., vimentin and twist).

CONCLUSION

BCAR1 may have a "dual impact" on EMT markers in tumor tissues and CTCs due to micro-environmental disparities, resulting in important clinical significance, which can potentially guide accurate treatment of LUAD.

EMT-Induced Gemcitabine Resistance in Pancreatic Cancer Involves the Functional Loss of Equilibrative Nucleoside Transporter 1

Epithelial-mesenchymal transition (EMT) in cancer cells drives cancer chemoresistance, yet the molecular events of EMT that underpin the acquisition of chemoresistance are poorly understood. Here, we demonstrate a loss of gemcitabine chemosensitivity facilitated by human equilibrative nucleoside transporter 1 (ENT1) during EMT in pancreatic cancer and identify that cadherin switching from the epithelial (E) to neuronal (N) type, a hallmark of EMT, contributes to this loss. Our findings demonstrate that N-cadherin decreases ENT1 expression, membrane localization, and gemcitabine transport, while E-cadherin augments each of these. Besides E- and N-cadherin, another epithelial cell adhesion molecule, EpCAM, played a more prominent role in determining ENT1 membrane localization. Forced expression of EpCAM opposed cadherin switching with restored ENT1 expression, membrane localization, and gemcitabine transport in EMT-committed pancreatic cancer cells. In gemcitabine-treated mice, EpCAM-positive tumors had high ENT1 expression and reduced metastasis, whereas tumors with N-cadherin expression resisted gemcitabine treatment and formed extensive secondary metastatic nodules. Tissue microarray profiling and multiplexed IHC analysis of pancreatic cancer patient-derived primary tumors revealed EpCAM and ENT1 cell surface coexpression is favored, and ENT1 plasma membrane expression positively predicted median overall survival times in patients treated with adjuvant gemcitabine. Together, our findings identify ENT1 as an inadvertent target of EMT signaling mediated by cadherin switching and provide a mechanism by which mesenchymal pancreatic cancer cells evade gemcitabine therapy during EMT.

Circulating tumor cells in hepatocellular carcinoma: single-cell based analysis, preclinical models, and clinical applications

Circulating tumor cells (CTCs) are shed into the bloodstream from primary tumors and metastatic lesions and provide significant information about tumor progression and metastasis. CTCs contribute to tumor metastasis through the epithelial-to-mesenchymal transition (EMT). CTC clusters and stem-like phenotypes lead to a more aggressive and metastatic potential. CTCs retain the heterogeneity and imitate the nature of corresponding primary tumors. Therefore, it is important to use single-cell based analysis to obtain information on tumor heterogeneity and biology. CTCs are also good candidates for building preclinical models (especially 3D organoid cultures) for drug screening, disease modeling, genome editing, tumor immunity research, and organ-like biobank establishment. In this article, we summarize the current CTC capture technology, dissect the phenotypes associated with CTC metastasis, and review the progress in single-cell based analysis and preclinical modeling of the pattern and kinetics of CTCs. In particular, we discuss the use of CTCs to assess the progression of hepatocellular carcinoma (HCC).

Expression and function of epithelial cell adhesion molecule EpCAM: where are we after 40 years?

EpCAM (epithelial cell adhesion molecule) was discovered four decades ago as a tumor antigen on colorectal carcinomas. Owing to its frequent and high expression on carcinomas and their metastases, EpCAM serves as a prognostic marker, a therapeutic target, and an anchor molecule on circulating and disseminated tumor cells (CTCs/DTCs), which are considered the major source for metastatic cancer cells. Today, EpCAM is reckoned as a multi-functional transmembrane protein involved in the regulation of cell adhesion, proliferation, migration, stemness, and epithelial-to-mesenchymal transition (EMT) of carcinoma cells. To fulfill these functions, EpCAM is instrumental in intra- and intercellular signaling as a full-length molecule and following regulated intramembrane proteolysis, generating functionally active extra- and intracellular fragments. Intact EpCAM and its proteolytic fragments interact with claudins, CD44, E-cadherin, epidermal growth factor receptor (EGFR), and intracellular signaling components of the WNT and Ras/Raf pathways, respectively. This plethora of functions contributes to shaping intratumor heterogeneity and partial EMT, which are major determinants of the clinical outcome of carcinoma patients. EpCAM represents a marker for the epithelial status of primary and systemic tumor cells and emerges as a measure for the metastatic capacity of CTCs. Consequentially, EpCAM has reclaimed potential as a prognostic marker and target on primary and systemic tumor cells.

A New Era in Liquid Biopsy: From Genotype to Phenotype

BACKGROUND

Liquid biopsy, in which tumor cells and tumor-derived biomolecules are collected from the circulation, is an attractive strategy for the management of cancer that allows the serial monitoring of patients during treatment. The analysis of circulating DNA produced by tumors provides a means to collect genotypic information about the molecular profile of a patient's cancer. Phenotypic information, which may be highly relevant for therapeutic selection, is ideally derived from intact cells, necessitating the analysis of circulating tumor cells (CTCs).

CONTENT

Recent advances in profiling CTCs at the single-cell level are providing new ways to collect critical phenotypic information. Analysis of secreted proteins, surface proteins, and intracellular RNAs for CTCs at the single-cell level is now possible and provides a means to quantify molecular markers that are involved with the mechanism of action of the newest therapeutics. We review the latest technological advances in this area along with related breakthroughs in high-purity CTC capture and in vivo profiling approaches, and we also present a perspective on how genotypic and phenotypic information collected via liquid biopsies is being used in the clinic.

SUMMARY

Over the past 5 years, the use of liquid biopsy has been adopted in clinical medicine, representing a major paradigm shift in how molecular testing is used in cancer management. The first tests to be used are genotypic measurements of tumor mutations that affect therapeutic effectiveness. Phenotypic information is also clinically relevant and essential for monitoring proteins and RNA sequences that are involved in therapeutic response.

Correlations between circulating tumor cell phenotyping and 18F-fluorodeoxyglucose positron emission tomography uptake in non-small cell lung cancer

PURPOSE

The epithelial-to-mesenchymal transition (EMT) phenotype-based subsets of circulating tumor cells (CTCs) might be predictors of tumor progression. We evaluated the clinical properties of different phenotypic CTCs in patients with non-small cell lung cancer (NSCLC). Secondly, we explored the association between different phenotypic CTCs and the uptake of 18F-fluorodeoxyglucose (FDG) by the primary tumor on a positron emission tomographic (PET) scan.

METHODS

Venous blood samples from 34 pathologically confirmed Stage IIB-IVB NSCLC patients were collected prospectively. CTCs were immunoassayed using a SE-i·FISH®CTC kit. We identified CTCs into cytokeratin positive (CK⁺) and cytokeratin negative (CK^-) phenotypes. CTC classifications were correlated with the maximum standardized uptake value (SUVmax) measured by 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT). Overall survival (OS) and progression-free survival (PFS) curves were produced using the Kaplan-Meier method.

RESULTS

CTCs were detected in 91.2% of NSCLC patients. CTC counting was associated with TNM stage (P = 0.014) and distant metastasis (P = 0.007). The number of CK^-CTCs was also positively associated with TNM stage (P = 0.022) and distant metastasis (P = 0.007). Both total CTC counting and CK^-CTC counting did not show association with SUVmax value (P = 0.959, P = 0.903). Kaplan-Meier survival analysis demonstrated that patients with ≥ 7 CTCs had shorter OS (P = 0.003) and PFS (P = 0.001) relative to patients with < 7 CTCs). Notably, the number of CK^-CTCs can act as independent risk factors for PFS (P = 0.044) and OS (P = 0.043) in NSCLC patients. However, SUVmax value was not associated with OS (P = 0.895) and PFS (P = 0.686).

CONCLUSION

The CTC subpopulations could be useful evidence for testing metastasis and prognosis in NSCLC patients. The SUVmax value of the primary tumor was not related to prognosis in patients with NSCLC.

Relationship between circulating tumor cells undergoing EMT and short-term efficacy following interventional treatment in patients with hepatocellular carcinoma

Objective

A growing number of studies have indicated that epithelial-mesenchymal transition (EMT) phenotypes and the number of circulating tumor cells (CTCs) are significant indicators of tumor characteristics and treatment efficacy, and thus have a broad range of potential applications in the diagnosis and treatment of malignant tumors. The value of data on CTC phenotypes and CTC counts in the diagnosis of hepatocellular carcinoma (HCC) and assessment of efficacy after comprehensive interventional therapy remains unclear.

Methods

Data of 107 patients who exhibited space-occupying lesions in the liver on enhanced CT/MRI scans at the Guangdong Provincial People’s Hospital (a tertiary medical center) between August 2017 and October 2018, were retrospectively analyzed. All enrolled patients were treated with transcatheter arterial chemoembolization (TACE) combined with microwave ablation (MWA). An imFISH CTC assay was used to isolate and count CTCs with different EMT phenotypes in the patients’ peripheral blood, which facilitated an analysis of the value of CTC phenotype and CTC count data in the diagnosis or treatment of HCC.

Results

The CTC count and EMT phenotypes in HCC patients were not associated with patient characteristics such as age, sex, Hepatitis B Virus (HBV)-DNA status, alcohol consumption history, Aspartate Transaminase (AST) to Platelet Ratio Index (APRI) score, Eastern Cooperative Oncology Group (ECOG) score, Child-Pugh score, alpha-fetoprotein (AFP), number and size of tumors, vascular invasion, or metastasis (P ​> ​0.05). The CTC count and EMT phenotypes in HCC patients before treatment were not predictive of short-term efficacy (P ​> ​0.05). Comprehensive interventional therapy reduced the total CTC count and mesenchymal CTC count (P ​= ​0.034 and 0.022, respectively).

Conclusion

TACE in combination with ablation reduced the total CTC count and mesenchymal CTC count. The CTC count and EMT phenotypes may be associated with long-term efficacy.

Aneuploid Circulating Tumor-Derived Endothelial Cell (CTEC): A Novel Versatile Player in Tumor Neovascularization and Cancer Metastasis

Hematogenous and lymphogenous cancer metastases are significantly impacted by tumor neovascularization, which predominantly consists of blood vessel-relevant angiogenesis, vasculogenesis, vasculogenic mimicry, and lymphatic vessel-related lymphangiogenesis. Among the endothelial cells that make up the lining of tumor vasculature, a majority of them are tumor-derived endothelial cells (TECs), exhibiting cytogenetic abnormalities of aneuploid chromosomes. Aneuploid TECs are generated from “cancerization of stromal endothelial cells” and “endothelialization of carcinoma cells” in the hypoxic tumor microenvironment. Both processes crucially engage the hypoxia-triggered epithelial-to-mesenchymal transition (EMT) and endothelial-to-mesenchymal transition (EndoMT). Compared to the cancerization process, endothelialization of cancer cells, which comprises the fusion of tumor cells with endothelial cells and transdifferentiation of cancer cells into TECs, is the dominant pathway. Tumor-derived endothelial cells, possessing the dual properties of cancerous malignancy and endothelial vascularization ability, are thus the endothelialized cancer cells. Circulating tumor-derived endothelial cells (CTECs) are TECs shed into the peripheral circulation. Aneuploid CD31⁺ CTECs, together with their counterpart CD31^- circulating tumor cells (CTCs), constitute a unique pair of cellular circulating tumor biomarkers. This review discusses a proposed cascaded framework that focuses on the origins of TECs and CTECs in the hypoxic tumor microenvironment and their clinical implications for tumorigenesis, neovascularization, disease progression, and cancer metastasis. Aneuploid CTECs, harboring hybridized properties of malignancy, vascularization and motility, may serve as a unique target for developing a novel metastasis blockade cancer therapy.

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.

Dynamic monitoring of CD45-/CD31+/DAPI+ circulating endothelial cells aneuploid for chromosome 8 during neoadjuvant chemotherapy in locally advanced breast cancer

Background:

Neoadjuvant chemotherapy (NCT) is the standard treatment for patients with locally advanced breast cancer (LABC). The aim of this study was to verify this relationship, and to estimate the clinical value of aneuploid circulating endothelial cells (CECs) in LABC patients with different NCT responses.

Methods:

Breast cancer patients received an EC4-T4 NCT regimen. Peripheral blood mononuclear cells were obtained before NCT, and after the first and last NCT courses. A novel subtraction enrichment and immunostaining fluorescence in situ hybridization (SE-iFISH) strategy was applied for detection of circulating rare cells (CRCs). CECs (CD45–/CD31+/DAPI+) and circulating tumor cells (CTCs) with different cytogenetic abnormalities related to chromosome 8 aneuploidy were analyzed in LABC patients subjected to NCT.

Results:

A total of 41 patients were enrolled. Firstly, CD31+/EpCAM+ aneuploid endothelial-epithelial fusion cells were observed in LABC patients. Further, aneuploid CECs in the peripheral blood showed a biphasic response during NCT, as they initially increased and then decreased, whereas a strong positive correlation was observed between aneuploid CECs and CTC numbers.

Conclusion:

We determined that aneuploid CEC dynamics vary in patients with different response to chemotherapy. Elucidating the potential cross-talk between CTCs and aneuploid CECs may help characterize the process associated with the development of chemotherapy resistance and metastasis.

Prospects for Comprehensive Analyses of Circulating Tumor Cells in Tumor Biology

The comprehensive analysis of biological and clinical aspects of circulating tumor cells (CTCs) has attracted interest as a means of enabling non-invasive, real-time monitoring of cancer patients and enhancing our fundamental understanding of tumor metastasis. However, CTC populations are extremely small when compared to other cell populations in the blood, limiting our comprehension of CTC biology and their clinical utility. Recently developed proteomic and genomic techniques that require only a small amount of sample have attracted much interest and expanded the potential utility of CTCs. Cancer heterogeneity, including specific mutations, greatly impacts disease diagnosis and the choice of available therapeutic strategies. The CTC population consists primarily of cancer stem cells, and CTC subpopulations are thought to undergo epithelial-mesenchymal transition during dissemination. To better characterize tumor cell populations, we demonstrated that changes in genomic profiles identified via next-generation sequencing of liquid biopsy samples could be expanded upon to increase sensitivity without decreasing specificity by using a combination of assays with CTCs and circulating tumor DNA. To enhance our understanding of CTC biology, we developed a metabolome analysis method applicable to single CTCs. Here, we review-omics studies related to CTC analysis and discuss various clinical and biological issues related to CTCs.

MiR-524-5p Suppresses Migration, Invasion, and EMT Progression in Breast Cancer Cells Through Targeting FSTL1

Background: The effects of miR-524-5p on breast cancer (BC) have not been investigated, though studies show that miR-524-5p has an anticancer function. Thus, this study investigated the effects of miR-524-5p on BC cells and its potential molecular mechanism. Materials and Methods: The expression of miR-524-5p from the collected BC samples was determined. Cell counting kit-8 (CCK-8) assay was performed to examine the effect of miR-524-5p on BC cells viability. The target for miR-524-5p was predicted by bioinformatics and further verified by luciferase assay. Wound healing assay and transwell assay were performed to determine cell migration and invasion of BC cells. The expressions of Follistatin-like 1 (FSTL1) and related proteins in epithelial-mesenchymal transition (EMT) were detected by Western blotting and quantitative real-time polymerase chain reaction. Results: MiR-524-5p was low-expressed in BC samples, and upregulation of miR-524-5p suppressed BC cell viability, migration, and invasion. FSTL1 was predicted as a target for miR-524-5p. In addition, overexpressed FSTL1 effectively abolished the effect of miR-524-5p on inhibiting FSTL1 expression, and reversed the inhibitory effects of miR-524-5p on the migration, invasion of BC cells as well as the effect of miR-524-5p on regulating the expressions of matrix metalloproteinase 2 (MMP2), matrix metalloproteinase 9 (MMP9), E-cadherin, and N-cadherin. Conclusions: Our findings suggest that miR-524-5p targeting FSTL1 adversely affects the progression of migration, invasion, and EMT of BC cells, thus, miR-524-5p is possibly a target for BC treatment.

Circulating Tumor Cells in Early and Advanced Breast Cancer; Biology and Prognostic Value

Breast cancer metastasis is the leading cause of cancer deaths in women and is difficult to combat due to the long periods in which disseminated cells retain a potential to be re-activated and start the relapse. Assessing the number and molecular profile of circulating tumor cells (CTCs) in breast cancer patients, especially in early breast cancer, should help in identifying the possibility of relapse in time for therapeutic intervention to prevent or delay recurrence. While metastatic breast cancer is considered incurable, molecular analysis of CTCs still have a potential to define particular susceptibilities of the cells representing the current tumor burden, which may differ considerably from the cells of the primary tumor, and offer more tailored therapy to the patients. In this review we inspect the routes to metastasis and how they can be linked to specific features of CTCs, how CTC analysis may be used in therapy, and what is the current status of the research and efforts to include CTC analysis in clinical practice.

Single-Chromosomal Gains Can Function as Metastasis Suppressors and Promoters in Colon Cancer

High levels of cancer aneuploidy are frequently associated with poor prognosis. To examine the relationship between aneuploidy and cancer progression, we analyzed a series of congenic cell lines that harbor single extra chromosomes. We found that across 13 different trisomic cell lines, 12 trisomies suppressed invasiveness or were largely neutral, while a single trisomy increased metastatic behavior by triggering a partial epithelial-mesenchymal transition. In contrast, we discovered that chromosomal instability activates cGAS/STING signaling but strongly suppresses invasiveness. By analyzing patient copy-number data, we demonstrate that specific aneuploidies are associated with distinct outcomes, and the acquisition of certain aneuploidies is in fact linked with a favorable prognosis. Thus, aneuploidy is not a uniform driver of malignancy, and different aneuploidies can uniquely influence tumor progression. At the same time, the gain of a single chromosome is capable of inducing a profound cell state transition, thereby linking genomic plasticity, phenotypic plasticity, and metastasis.

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.

Fluidic Multivalent Membrane Nanointerface Enables Synergetic Enrichment of Circulating Tumor Cells with High Efficiency and Viability

The ubiquitous biomembrane interface, with its dynamic lateral fluidity, allows membrane-bound components to rearrange and localize for high-affinity multivalent ligand-receptor interactions in diverse life activities. Inspired by this, we herein engineered a fluidic multivalent nanointerface by decorating a microfluidic chip with aptamer-functionalized leukocyte membrane nanovesicles for high-performance isolation of circulating tumor cells (CTCs). This fluidic biomimetic nanointerface with active recruitment-binding afforded significant affinity enhancement by 4 orders of magnitude, exhibiting 7-fold higher capture efficiency compared to a monovalent aptamer functionalized-chip in blood. Meanwhile, this soft nanointerface inherited the biological benefits of a natural biomembrane, minimizing background blood cell adsorption and maintaining excellent CTC viability (97.6%). Using the chip, CTCs were successfully detected in all cancer patient samples tested (17/17), suggesting the high potential of this fluidity-enhanced multivalent binding strategy in clinical applications. We expect this bioengineered interface strategy will lead to the design of innovative biomimetic platforms in the biomedical field by leveraging natural cell-cell interaction with a natural biomaterial.

Metabolic classification of circulating tumor cells as a biomarker for metastasis and prognosis in breast cancer

Background

Circulating tumor cells (CTCs) has been demonstrated as a promising liquid biopsy marker for breast cancer (BC). However, the intra-patient heterogeneity of CTCs remains a challenge to clinical application. We aim at profiling aggressive CTCs subpopulation in BC utilizing the distinctive metabolic reprogramming which is a hallmark of metastatic tumor cells.

Methods

Oncomine, TCGA and Kaplan–Meier plotter databases were utilized to analyze expression and survival relevance of the previously screened metastasis-promoting metabolic markers (PGK1/G6PD) in BC patients. CTCs detection and metabolic classification were performed through micro-filtration and multiple RNA in situ hybridization using CD45 and PGK1/G6PD probes. Blood samples were collected from 64 BC patients before treatment for CTCs analysis. Patient characteristics were recorded to evaluate clinical applications of CTCs metabolic subtypes, as well as morphological EMT subtypes classified by epithelial (EpCAM/CKs) and mesenchymal (Vimentin/Twist) markers.

Results

PGK1 and G6PD expressions were up-regulated in invasive BC tissues compared with normal mammary tissues. Increased tissue expressions of PGK1 or G6PD indicated shortened overall and relapse-free survival of BC patients (P < 0.001). Blood GM⁺CTCs (DAPI⁺CD45⁻PGK1/G6PD⁺) was detectable (range 0–54 cells/5 mL) in 61.8% of tCTCs > 0 patients. Increased GM⁺CTCs number and positive rate were correlated with tumor metastasis and progression (P < 0.05). The GM⁺CTCs ≥ 2/5 mL level presented superior AUC of ROC at 0.854 (95% CI 0.741–0.968) in the diagnosis of BC metastasis (sensitivity/specificity: 66.7%/91.3%), compared with that of tCTCs (0.779) and CTCs-EMT subtypes (E-CTCs 0.645, H-CTCs 0.727 and M-CTCs 0.697). Moreover, GM⁺CTCs⁺ group had inferior survival with decreased 2 years-PFS proportion (18.5%) than GM⁺CTCs⁻ group (87.9%; P = 0.001).

Conclusions

This work establishes a PGK1/G6PD-based method for CTCs metabolic classification to identify the aggressive CTCs subpopulation. Metabolically active GM⁺CTCs subtype is suggested a favorable biomarker of distant metastasis and prognosis in BC patients.

Tumor biology and multidisciplinary strategies of oligometastasis in gastrointestinal cancers

More than 70% of gastrointestinal (GI) cancers are diagnosed with metastases, leading to poor prognosis. For some cancer patients with limited sites of metastatic tumors, the term oligometastatic disease (OMD) has been coined as opposed to systemic polymetastasis (PMD) disease. Stephan Paget first described an organ-specific pattern of metastasis in 1889, now known as the "seed and soil" theory where distinct cancer types are found to metastasize to different tumor-specific sites. Our understanding of the biology of tumor metastasis and specifically the molecular mechanisms driving their formation are still limited, in particular, as it relates to the genesis of oligometastasis. In the following review, we discuss recent advances in general understanding of this metastatic behavior including the role of specific signaling pathways, various molecular features and biomarkers, as well as the interaction of carcinoma cells with their tissue microenvironments (both primary and metastatic niches). The unique features that underlie OMD provide potential targets for localized therapy. As it relates to clinical practice, OMD is emerging as treatable with surgical resection and/or other local therapy options. Strategies currently being applied in the clinical management of OMD will be discussed including surgical, radiation-based therapy, ablation procedures, and the results of emerging clinical trials involving immunotherapy.

Clinical Evolution of Epithelial-Mesenchymal Transition in Human Carcinomas

The significance of the phenotypic plasticity afforded by epithelial-mesenchymal transition (EMT) for cancer progression and drug resistance remains to be fully elucidated in the clinic. We evaluated epithelial-mesenchymal phenotypic characteristics across a range of tumor histologies using a validated, high-resolution digital microscopic immunofluorescence assay (IFA) that incorporates β-catenin detection and cellular morphology to delineate carcinoma cells from stromal fibroblasts and that quantitates the individual and colocalized expression of the epithelial marker E-cadherin (E) and the mesenchymal marker vimentin (V) at subcellular resolution ("EMT-IFA"). We report the discovery of β-catenin+ cancer cells that coexpress E-cadherin and vimentin in core-needle biopsies from patients with various advanced metastatic carcinomas, wherein these cells are transitioning between strongly epithelial and strongly mesenchymal-like phenotypes. Treatment of carcinoma models with anticancer drugs that differ in their mechanism of action (the tyrosine kinase inhibitor pazopanib in MKN45 gastric carcinoma xenografts and the combination of tubulin-targeting agent paclitaxel with the BCR-ABL inhibitor nilotinib in MDA-MB-468 breast cancer xenografts) caused changes in the tumor epithelial-mesenchymal character. Moreover, the appearance of partial EMT or mesenchymal-like carcinoma cells in MDA-MB-468 tumors treated with the paclitaxel-nilotinib combination resulted in upregulation of cancer stem cell (CSC) markers and susceptibility to FAK inhibitor. A metastatic prostate cancer patient treated with the PARP inhibitor talazoparib exhibited similar CSC marker upregulation. Therefore, the phenotypic plasticity conferred on carcinoma cells by EMT allows for rapid adaptation to cytotoxic or molecularly targeted therapy and could create a form of acquired drug resistance that is transient in nature. SIGNIFICANCE: Despite the role of EMT in metastasis and drug resistance, no standardized assessment of EMT phenotypic heterogeneity in human carcinomas exists; the EMT-IFA allows for clinical monitoring of tumor adaptation to therapy.

Controversies around epithelial-mesenchymal plasticity in cancer metastasis

Experimental evidence accumulated over decades has implicated epithelial-mesenchymal plasticity (EMP), which collectively encompasses epithelial-mesenchymal transition and the reverse process of mesenchymal-epithelial transition, in tumour metastasis, cancer stem cell generation and maintenance, and therapeutic resistance. However, the dynamic nature of EMP processes, the apparent need to reverse mesenchymal changes for the development of macrometastases and the likelihood that only minor cancer cell subpopulations exhibit EMP at any one time have made such evidence difficult to accrue in the clinical setting. In this Perspectives article, we outline the existing preclinical and clinical evidence for EMP and reflect on recent controversies, including the failure of initial lineage-tracing experiments to confirm a major role for EMP in dissemination, and discuss accumulating data suggesting that epithelial features and/or a hybrid epithelial-mesenchymal phenotype are important in metastasis. We also highlight strategies to address the complexities of therapeutically targeting the EMP process that give consideration to its spatially and temporally divergent roles in metastasis, with the view that this will yield a potent and broad class of therapeutic agents.

An update: circulating tumor cells in head and neck cancer

Introduction: Local and distant metastatic disease occurs in approximately half of head and neck squamous cell carcinoma (HNSCC) patients, representing an ongoing cause for treatment failure. Circulating tumor cells (CTCs) are transient cancer cells which have the capacity to metastasize to distant sites such as the lungs and liver in HNSCC. When metastatic disease is radiographically evident, the patient prognosis is often poor. Therefore, methodologies to assess micrometastatic disease are needed to (1) identify patients likely to develop metastatic disease and (2) treat and monitor these patients more aggressively. Whilst CTCs are well documented in other tumor streams such as breast, colorectal cancer and prostate cancers, the data and clinical utility in HNSCC remains limited.Areas covered: Here we summarize the recent advances of CTCs and applications in HNSCC.Expert opinion: CTC enumeration can be prognostic in HNSCC; further studies are warranted to investigate the role of CTC clusters in HNSCC; CTC culture (in vivo/ex vivo) may present a possibility to expand these rare cells to a critical mass for functional testing; PD-L1 expression of HNSCC CTCs may present a means by which to determine patients likely to respond to therapy; a HNSCC CTC-specific marker is warranted.

Insights into Biological Role of LncRNAs in Epithelial-Mesenchymal Transition

Long non-coding RNAs (lncRNAs) are versatile regulators of gene expression and play crucial roles in diverse biological processes. Epithelial-mesenchymal transition (EMT) is a cellular program that drives plasticity during embryogenesis, wound healing, and malignant progression. Increasing evidence shows that lncRNAs orchestrate multiple cellular processes by modulating EMT in diverse cell types. Dysregulated lncRNAs that can impact epithelial plasticity by affecting different EMT markers and target genes have been identified. However, our understanding of the landscape of lncRNAs important in EMT is far from complete. Here, we summarize recent findings on the mechanisms and roles of lncRNAs in EMT and elaborate on how lncRNAs can modulate EMT by interacting with RNA, DNA, or proteins in epigenetic, transcriptional, and post-transcriptional regulation. This review also highlights significant EMT pathways that may be altered by diverse lncRNAs, thereby suggesting their therapeutic potential.

Autophagy and Its Relationship to Epithelial to Mesenchymal Transition: When Autophagy Inhibition for Cancer Therapy Turns Counterproductive

The manipulation of autophagy for cancer therapy has gained recent interest in clinical settings. Although inhibition of autophagy is currently being used in clinical trials for the treatment of several malignancies, autophagy has been shown to have diverse implications for normal cell homeostasis, cancer cell survival, and signaling to cells in the tumor microenvironment. Among these implications and of relevance for cancer therapy, the autophagic process is known to be involved in the regulation of protein secretion, in tumor cell immunogenicity, and in the regulation of epithelial-to-mesenchymal transition (EMT), a critical step in the process of cancer cell invasion. In this work, we have reviewed recent evidence linking autophagy to the regulation of EMT in cancer and normal epithelial cells, and have discussed important implications for the manipulation of autophagy during cancer therapy.

Notch and breast cancer metastasis: Current knowledge, new sights and targeted therapy

Breast cancer is the most common type of invasive cancer in females and metastasis is one of the major causes of breast cancer-associated mortality. Following detachment from the primary site, disseminated tumor cells (DTCs) enter the bloodstream and establish secondary colonies during the metastatic process. An increasing amount of studies have elucidated the importance of Notch signaling in breast cancer metastasis; therefore, the present review focuses on the mechanisms by which Notch contributes to the occurrence of breast cancer DTCs, increases their motility, establishes interactions with the tumor microenvironment, protects DTCs from host surveillance and finally facilitates secondary colonization. Identification of the underlying mechanisms of Notch-associated breast cancer metastasis will provide additional insights that may contribute towards the development of novel Notch-targeted therapeutic strategies, which may aid in reducing metastasis, culminating in an improved patient prognosis.