Cancer micrometastases

Progress and challenges of sequencing and analyzing circulating tumor cells

Circulating tumor cells (CTCs) slough off primary tumor tissues and are swept away by the circulatory system. These CTCs can remain in circulation or colonize new sites, forming metastatic clones in distant organs. Recently, CTC analyses have been successfully used as effective clinical tools to monitor tumor progression and prognosis. With advances in next-generation sequencing (NGS) and single-cell sequencing (SCS) technologies, scientists can obtain the complete genome of a CTC and compare it with corresponding primary and metastatic tumors. CTC sequencing has been successfully applied to monitor genomic variations in metastatic and recurrent tumors, infer tumor evolution during treatment, and examine gene expression as well as the mechanism of the epithelial-mesenchymal transition. However, compared with cancer biopsy sequencing and circulating tumor DNA sequencing, the sequencing of CTC genomes and transcriptomes is more complex and technically difficult. Challenges include enriching pure tumor cells from a background of white blood cells, isolating and collecting cells without damaging or losing DNA and RNA, obtaining unbiased and even whole-genome and transcriptome amplification material, and accurately analyzing CTC sequencing data. Here, we review and summarize recent studies using NGS on CTCs. We mainly focus on CTC genome and transcriptome sequencing and the biological and potential clinical applications of these methodologies. Finally, we discuss challenges and future perspectives of CTC sequencing.

Prognostic value of CD133+ CD54+ CD44+ circulating tumor cells in colorectal cancer with liver metastasis

In the previous study, we had showed the expression of CD133⁺ CD54⁺ CD44⁺ cellular subpopulation of circulating tumor cells (CTCs) was significantly associated with liver metastasis of colorectal cancer (CRC). This study aimed to explore whether this subpopulation of CTCs have a prognostic value in CRC patients. Flow cytometry was used to detect the expression of cellular subpopulations of CTCs with CD133, CD54, and CD44 in 152 CRC patients, between December 2013 and October 2014. The impact of clinicopathological factors and the expression of cellular subpopulations of CTCs on overall survival were then analyzed. CRC patients with liver metastases who underwent resection of the primary tumor accompanied by surgical treatment for metastasis had a better survival than other patients (P < 0.001). The liver metastatic CRC patients with high expression of CD133⁺ CD54⁺ (P < 0.001), CD133^- CD54⁺ (P = 0.004), and CD133⁺ CD44⁺ CD54⁺ (P = 0.003) cellular subpopulations of CTCs had a worse survival than those patients with low expression. Multivariable survival analyses identified carcinoembryonic antigen levels (hazard ratio [HR] = 3.056; 95% confidence interval [CI] = 1.354-6.897; P = 0.007), treatment strategy (HR = 0.212; 95% CI = 0.056-0.808; P = 0.023), and CD133⁺ CD44⁺ CD54⁺ cellular subpopulation of CTCs (HR = 6.459; 95% CI = 1.461-28.558; P = 0.014) as independent prognostic factors for CRC patients with liver metastasis. CD133⁺ CD44⁺ CD54⁺ cellular subpopulation of CTCs has a prognostic value in CRC patients with liver metastasis, especially in the survival of CRC patients with liver metastasis who did not undergo surgical treatment for metastasis.

Subversion of NK-cell and TNFα Immune Surveillance Drives Tumor Recurrence

Understanding how incompletely cleared primary tumors transition from minimal residual disease (MRD) into treatment-resistant, immune-invisible recurrences has major clinical significance. We show here that this transition is mediated through the subversion of two key elements of innate immunosurveillance. In the first, the role of TNFα changes from an antitumor effector against primary tumors into a growth promoter for MRD. Second, whereas primary tumors induced a natural killer (NK)-mediated cytokine response characterized by low IL6 and elevated IFNγ, PD-L1hi MRD cells promoted the secretion of IL6 but minimal IFNγ, inhibiting both NK-cell and T-cell surveillance. Tumor recurrence was promoted by trauma- or infection-like stimuli inducing VEGF and TNFα, which stimulated the growth of MRD tumors. Finally, therapies that blocked PD-1, TNFα, or NK cells delayed or prevented recurrence. These data show how innate immunosurveillance mechanisms, which control infection and growth of primary tumors, are exploited by recurrent, competent tumors and identify therapeutic targets in patients with MRD known to be at high risk of relapse. Cancer Immunol Res; 5(11); 1029-45. ©2017 AACR.

Tumor-suppressive miRNA-135a inhibits breast cancer cell proliferation by targeting ELK1 and ELK3 oncogenes

Breast cancer is the most common malignant disease amongst women. miRNAs are small, non-coding RNAs that regulate gene expression, thus have the potential to play an important role during cancer development. Emerging evidence shows that miR-135a is down-regulated in breast cancer cells, but the functional roles of miR-135a in breast cancer cells remains unexplored. For this purpose, we investigated the expression of miR-135a in breast cancer cells and explored its functional role during breast cancer progression. In vitro study showed that miR-135a may be a novel tumor suppressor. Further studies showed that transcription factors ELK1 and ELK3 are direct target genes of miR-135a that modulates the suppressive function of miR-135a in breast cancer cells. Induced expression of miR-135a significantly downregulated the expression of ELK1 and ELK3 both at mRNA and protein levels. Furthermore, the effect of miR-135a in MCF-7 and T47D cells was investigated by the overexpression of miR-135a mimics. In vitro, induced expression of miR-135a in breast cancer cells inhibited cell Proliferation and clongenicity. Moreover, a luciferase activity assay revealed that miR-135a could directly target the 3'-untranslated region (3' UTRS) of ELK1 and ELK3 oncogenes. In addition, rescue experiment demonstrated that the promoted cell growth by transcription factors ELK1 and ELK3 was attenuated by the over-expression of miR-135a. Our study demonstrates that miR-135a regulates cell proliferation in breast cancer by targeting ELK1 and ELK3 oncogenes, and suggests that miR-135a potentially can act as a tumor suppressor.

Circulating tumour cell PD-L1 test for head and neck cancers

Immune checkpoint inhibitors have gained traction over the last few years in the treatment of metastatic/recurrent head and neck squamous cell carcinoma (HNSCC) patients. Monoclonal antibodies that block the programmed death 1 (PD-1) receptor and its major ligand, PD-L1, have shown durable responses and low toxicity profiles. There are currently no validated predictive biomarkers to select patients likely to respond to anti-PD-1/PD-L1 therapy to avoid unwanted side effects and to reduce healthcare expenditure. A circulating tumour cell (CTC) PD-L1 assay could be developed as a companion diagnostic tool to potentially predict the efficacy of immune checkpoint blockade treatments.

Androgen receptor expression on circulating tumor cells in metastatic breast cancer

Purpose

Methods

Results

Conclusions

Identifying cancer origin using circulating tumor cells

Circulating tumor cells (CTCs) have become an established clinical evaluation biomarker. CTC count provides a good correlation with the prognosis of cancer patients, but has only been used with known cancer patients, and has been unable to predict the origin of the CTCs. This study demonstrates the analysis of CTCs for the identification of their primary cancer source. Twelve mL blood samples were equally dispensed on 6 CMx chips, microfluidic chips coated with an anti-EpCAM-conjugated supported lipid bilayer, for CTC capture and isolation. Captured CTCs were eluted to an immunofluorescence (IF) staining panel consisting of 6 groups of antibodies: anti-panCK, anti-CK18, anti-CK7, anti-TTF-1, anti-CK20/anti-CDX2, and anti-PSA/anti-PSMA. Cancer cell lines of lung (H1975), colorectal (DLD-1, HCT-116), and prostate (PC3, DU145, LNCaP) were selected to establish the sensitivity and specificity for distinguishing CTCs from lung, colorectal, and prostate cancer. Spiking experiments performed in 2mL of culture medium or whole blood proved the CMx platform can enumerate cancer cells of lung, colorectal, and prostate. The IF panel was tested on blood samples from lung cancer patients (n = 3), colorectal cancer patients (n = 5), prostate cancer patients (n = 5), and healthy individuals (n = 12). Peripheral blood samples found panCK⁺ and CK18⁺ CTCs in lung, colorectal, and prostate cancers. CTCs expressing CK7⁺ or TTF-1⁺, (CK20/ CDX2)⁺, or (PSA/ PSMA)⁺ corresponded to lung, colorectal, or prostate cancer, respectively. In conclusion, we have designed an immunofluorescence staining panel to identify CTCs in peripheral blood to correctly identify cancer cell origin.

New insights into the metastatic behavior after breast cancer surgery, according to well-established clinicopathological variables and molecular subtypes

Despite advances in treatment, up to 30% of patients with early breast cancer (BC) experience distant disease relapse. However, a comprehensive understanding of tumor spread and site-specific recurrence patterns remains lacking. This retrospective case-control study included 103 consecutive patients with metastatic BC admitted to our institution (2000–2013). Cases were matched according to age, tumor biology, and clinicopathological features to 221 patients with non-metastatic BC (control group). The median follow-up period among the 324 eligible patients was 7.3 years. While relatively low values for sensitivity (71%) and specificity (56%) were found for axillary lymph node (ALN) involvement as an indicator of risk and pattern of distant relapse, nodal status remained the most powerful predictor of metastases (OR: 3.294; CL: 1.9–5.5). Rates of dissemination and metastatic efficiency differed according to molecular subtype. HER2-positive subtypes showed a stronger association with systemic spread (OR: 2.127; CL: 1.2–3.8) than other subgroups. Classification as Luminal or Non-Luminal showed an increased risk of lung and distant nodal recurrence, and a decreased risk in bone metastases in the Non-Luminal group (OR: 2.9, 3.345, and 0.2, respectively). Tumors with HER2 overexpression had a significantly high risk for distant relapse (OR: 2.127) compared with HER2-negative tumors and also showed higher central nervous system (CNS) and lung metastatic potential (OR: 5.6 and 2.65, respectively) and low risk of bone disease progression (OR: 0.294). Furthermore, we found significant associations between biological profiles and sites of recurrence. A new process of clinical/diagnostic staging, including molecular subtypes, could better predict the likelihood of distant relapses and their anatomical location. Recognition and appreciation of clinically distinct molecular subtypes may assist in evaluation of the probability of distant relapses and their sites. Our analysis provides new insights into management of metastatic disease behavior, to lead to an optimal disease-tailored approach and appropriate follow-up.

Molecular characterization of circulating tumor cells-from bench to bedside

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

Liquid biopsy in patients with hepatocellular carcinoma: Circulating tumor cells and cell-free nucleic acids

Hepatocellular carcinoma (HCC), with its high incidence and mortality rate, is one of the most common malignant tumors. Despite recent development of a diagnostic and treatment method, the prognosis of HCC remains poor. Therefore, to provide optimal treatment for each patient with HCC, more precise and effective biomarkers are urgently needed which could facilitate a more detailed individualized decision-making during HCC treatment, including the following; risk assessment, early cancer detection, prediction of treatment or prognostic outcome. In the blood of cancer patients, accumulating evidence about circulating tumor cells and cell-free nucleic acids has suggested their potent clinical utilities as novel biomarker. This concept, so-called “liquid biopsy” is widely known as an alternative approach to cancer tissue biopsy. This method might facilitate a more sensitive diagnosis and better decision-making by obtaining genetic and epigenetic aberrations that are closely associated with cancer initiation and progression. In this article, we review recent developments based on the available literature on both circulating tumor cells and cell-free nucleic acids in cancer patients, especially focusing on Hepatocellular carcinoma.

Cancer metastasis - tricks of the trade

Decades of cancer research have unraveled genetic, epigenetic and molecular pathways leading to plausible therapeutic targets; many of which hold great promise in improving clinical outcomes. Metastatic tumors become evident early on and are one of the major causes of cancer-related fatalities worldwide. This review depicts the sequential events of cancer metastasis. Genetic and epigenetic heterogeneity influences local tumor cell invasion, intravasation, survival in circulation, extravasation and colonization to distant sites. Each sequential event is associated with heterogeneous tumor microenvironment, gain of competence, unique population of cancer stem cells (CSCs), circulatory pathway, compatible niche and immune system support. A tight regulation of metastasis-promoting mechanisms and, in parallel, evading inhibitory mechanisms contribute to the severity and site of metastasis. A comprehensive understanding of tumor cell fate as an individual entity, as well as in combination with different promoting factors and associated molecular mechanisms, is anticipated in the coming years. This will enable scientists to depict design strategies for targeted cancer therapies.

Current approaches for avoiding the limitations of circulating tumor cells detection methods-implications for diagnosis and treatment of patients with solid tumors

Eight million people die of cancer each year and 90% of deaths are caused by systemic disease. Circulating tumor cells (CTCs) contribute to the formation of metastases and thus are the subject of extensive research and an abiding interest to biotechnology and pharmaceutical companies. Recent technological advances have resulted in greatly improved CTC detection, enumeration, expansion, and culture methods. However, despite the fact that nearly 150 years have passed since the first detection and description of CTCs in human blood and enormous technological progress that has taken place in this field, especially within the last decade, few CTC detection methods have been approved for routine clinical use. This reflects the substantial methodological problems related to the nature of these cells, their heterogeneity, and diverse metastatic potential. Here, we provide an overview of CTC phenotypes, including the plasticity of CTCs and the relevance of inflammation and cell fusion phenomena for CTC biology. We also review the literature on CTC detection methodology-its recent improvements, clinical significance, and efforts of its clinical application in cancer patients management. At present, CTC detection remains a challenging diagnostic approach as a result of numerous current methodological limitations. This is especially problematic during the early stages of the disease due to the small numbers of CTCs released into the blood of cancer patients. Nonetheless, the rapid development of novel techniques of CTC detection and enumeration in peripheral blood is expected to expedite their implementation in the clinical setting. It is of utmost importance to understand the biology of CTCs and their distinct populations as a prerequisite for achieving this ultimate goal.

Nanoparticles as Theranostic Vehicles in Experimental and Clinical Applications-Focus on Prostate and Breast Cancer

Prostate and breast cancer are the second most and most commonly diagnosed cancer in men and women worldwide, respectively. The American Cancer Society estimates that during 2016 in the USA around 430,000 individuals were diagnosed with one of these two types of cancers, and approximately 15% of them will die from the disease. In Europe, the rate of incidences and deaths are similar to those in the USA. Several different more or less successful diagnostic and therapeutic approaches have been developed and evaluated in order to tackle this issue and thereby decrease the death rates. By using nanoparticles as vehicles carrying both diagnostic and therapeutic molecular entities, individualized targeted theranostic nanomedicine has emerged as a promising option to increase the sensitivity and the specificity during diagnosis, as well as the likelihood of survival or prolonged survival after therapy. This article presents and discusses important and promising different kinds of nanoparticles, as well as imaging and therapy options, suitable for theranostic applications. The presentation of different nanoparticles and theranostic applications is quite general, but there is a special focus on prostate cancer. Some references and aspects regarding breast cancer are however also presented and discussed. Finally, the prostate cancer case is presented in more detail regarding diagnosis, staging, recurrence, metastases, and treatment options available today, followed by possible ways to move forward applying theranostics for both prostate and breast cancer based on promising experiments performed until today.

Comparison of three different methods for the detection of circulating tumor cells in mice with lung metastasis

Circulating tumor cells (CTCs) represent the key step of cancer cell dissemination. The alteration of CTCs correlates with the treatment outcome and prognosis. To enrich and identify CTCs from billions of blood cells renders a very challenging task, which triggers development of several methods, including lysis of RBC plus negative or positive enrichment using antibodies, and filter membrane or spiral microfluidics to capture CTCs. To compare the advantages of different enrichment methods for CTCs, we utilized the 4T1 breast cancer cells transfected with both green fluorescent protein (GFP) and luciferase to trace CTCs in the experimental lung metastasis model. Three methods were used to detect CTCs at the same time: bioluminescence assay, smearing method, and membrane filter method. The in vivo alive mouse imaging was used to dynamically monitor the growth of lung metastases. The sensitivity and accuracy of three detection methods were compared side-by-side. Our results showed that 1) the sensitivity of bioluminescence assay was the highest, but there was no information of CTC morphology; 2) the smearing method and membrane filter method could observe the detail of CTC morphology, such as in single or in cluster, while their sensitivity was lower than bioluminescence assay; 3) A dynamic observation at a 7-day intervals, the lung metastatic cancer grew at a log speed, while CTCs were increased at a low speed. This might be due to the activated immune cells eliminating the CTCs at a speed much faster than CTCs were generated. This comparison of three CTC detection methods in mouse model suggests that bioluminescence assay could be used in quantitative study of the effect of certain agent on the suppression of CTCs, while GFP-based morphological assays could be used to study the dissemination mechanism of CTCs. The combination of both bioluminescence assay and GFP-based assay would generate more information for quantity and quality of CTCs.

Circulating tumor cells promote the metastatic colonization of disseminated carcinoma cells by inducing systemic inflammation

Circulating tumor cells (CTCs) have been studied well in the prognosis for malignant diseases as liquid biopsy, but their contribution to tumor metastasis is not clearly defined. Here we report that CTCs could promote the metastatic colonization of disseminated carcinoma cells by inducing systemic inflammation and neutrophil recruitment to pre-metastatic organs. Depletion of neutrophils in vivo could effectively abrogate the promoting effect of CTCs on tumor cell metastasis. In the presence of CTCs, the pro-tumor function of neutrophils was augmented, whereas the antitumor function of neutrophils was suppressed. Mechanically, CTC-derived ligands for TLR2 and TLR4 (TLR2/4) induced the systemic inflammation, thus increasing the production of proinflammatory cytokines such as G-CSF and IL-6 that could induce the conversion of neutrophil function from tumor-suppressing to tumor-promoting. Moreover, CTCs induced the production of endogenous TLR2/4 ligands such as S100A8, S100A9, and SAA3, which may amplify the stimulating effect that induces the expression of proinflammatory cytokines. The promoting effect of CTCs on tumor cell metastasis could be abrogated by suppressing inflammatory response with IL-37, an anti-inflammatory cytokine, or blocking CTC-derived ligands for TLR2/4. Identification of the metastatic axis of CTCs/systemic inflammation/neutrophils may provide potential targets for preventing tumor cell metastasis.

Bone-in-culture array as a platform to model early-stage bone metastases and discover anti-metastasis therapies

The majority of breast cancer models for drug discovery are based on orthotopic or subcutaneous tumours. Therapeutic responses of metastases, especially microscopic metastases, are likely to differ from these tumours due to distinct cancer-microenvironment crosstalk in distant organs. Here, to recapitulate such differences, we established an ex vivo bone metastasis model, termed bone-in-culture array or BICA, by fragmenting mouse bones preloaded with breast cancer cells via intra-iliac artery injection. Cancer cells in BICA maintain features of in vivo bone micrometastases regarding the microenvironmental niche, gene expression profile, metastatic growth kinetics and therapeutic responses. Through a proof-of-principle drug screening using BICA, we found that danusertib, an inhibitor of the Aurora kinase family, preferentially inhibits bone micrometastases. In contrast, certain histone methyltransferase inhibitors stimulate metastatic outgrowth of indolent cancer cells, specifically in the bone. Thus, BICA can be used to investigate mechanisms involved in bone colonization and to rapidly test drug efficacies on bone micrometastases.

Human circulating and tissue gastric cancer stem cells display distinct epithelial-mesenchymal features and behaviors

INTRODUCTION

Metastasis is a leading cause of cancer-related-deaths worldwide. Recently, cancer stem cells (CSCs) have been believed to be responsible for tumor initiation and metastasis, but till now, difference of cellular features and behaviors between CSCs from tumor tissues (TCSCs) and circulation (CCSCs) remains largely unknown, which hinders the progression of targeted therapies for metastasis.

METHODS AND RESULTS

Here, we provide the features of circulating gastric cancer stem cells (CGCSCs) isolated from human gastric adenocarcinoma. The CGCSCs and TGCSCs were culture in a same serum free stem cell culture medium, however the morphology are different with each other. EMT-associated markers were measured by Immunofluorescence, Western Blotting, and RT-PCR methods, and the results indicated that the CGCSCs and TGCSCs carry different epithelial-mesenchymal features. And then, proliferation and apoptosis assays revealed that the CGCSCs exhibited characteristics of higher proliferation and resistance to apoptosis in vitro. Soft agar assay and nude mice tumorigenicity assay displayed strong tumorigenicity of CGCSCs. Finally, Matrigel invasion assays and in vivo experimental metastasis assay were also performed, which demonstrated that CGCSCs carry high invasive and metastatic capabilities than TGCSCs.

CONCLUSIONS

As expected, the CGCSCs indeed showed extremely invasive and metastatic properties. They also exhibited distinctive mesenchymal phenotypes, high self-renewal, proliferative capabilities, tumor induction and low apoptosis. Interestingly, CGCSCs show small cell-size than TGCSCs (tissue gastric cancer stem cells). The findings might help us to understand the biological characteristic of CGCSCs deeply, and give light to strategies for cancer therapies.

EMT, CSCs, and drug resistance: the mechanistic link and clinical implications

The success of anticancer therapy is usually limited by the development of drug resistance. Such acquired resistance is driven, in part, by intratumoural heterogeneity - that is, the phenotypic diversity of cancer cells co-inhabiting a single tumour mass. The introduction of the cancer stem cell (CSC) concept, which posits the presence of minor subpopulations of CSCs that are uniquely capable of seeding new tumours, has provided a framework for understanding one dimension of intratumoural heterogeneity. This concept, taken together with the identification of the epithelial-to-mesenchymal transition (EMT) programme as a critical regulator of the CSC phenotype, offers an opportunity to investigate the nature of intratumoural heterogeneity and a possible mechanistic basis for anticancer drug resistance. In fact, accumulating evidence indicates that conventional therapies often fail to eradicate carcinoma cells that have entered the CSC state via activation of the EMT programme, thereby permitting CSC-mediated clinical relapse. In this Review, we summarize our current understanding of the link between the EMT programme and the CSC state, and also discuss how this knowledge can contribute to improvements in clinical practice.

[Diagnostic Value of Folate Receptor-positive Circulating Tumor Cell in Lung Cancer: A Pilot Study]

背景与目的

评价一种通过叶酸受体(folate receptor, FR)检测循环肿瘤细胞(circulating tumor cell, CTC)的方法用于肺癌临床诊断的实用性和可行性及进一步探究CTC在肺癌术后复发的预测价值。

方法

通过免疫磁珠负向富集方法从3 mL外周血中捕获循环肿瘤细胞，再用肿瘤特异性叶酸配体-寡核苷酸偶和物标记捕获的循环肿瘤细胞，洗去没有结合的偶和物后，洗脱下特异性结合的偶合物的寡核苷酸用于定量PCR扩增分析。

结果

97例肺癌患者的CTC水平高于肺部良性疾病患者(P < 0.001)。本检测方法以8.7 Folate Units/3 mL为cutoff值，结果显示靶向PCR法对肺癌的检测灵敏度为82.5%，特异性为72.2%，特别是在Ⅰ期肺癌灵敏度达到86.8%。与其他肿瘤标志物(NSE、CEA、CYFRA21-1)比较，CTC对肺癌及Ⅰ期肺癌具有较高的诊断准确性(0.859; 95%CI: 0.779-0.939)和(0.912; 95%CI: 0.829-0.994)。5例肺癌患者术后2周内CTC水平高于cutoff值。

结论

叶酸受体阳性循环肿瘤细胞可以应用于肺癌的临床诊断，即使是对早期非小细胞肺癌(non-small cell lung cancer, NSCLC)的诊断。

Evaluation of a novel approach to circulating tumor cell isolation for cancer gene panel analysis in patients with breast cancer

Liquid biopsy isolation of circulating tumor cells (CTCs) allows the genomic analysis of CTCs, which is useful in the determination of personalized cancer therapy. In the present study, CTCs from patients with breast cancer were enriched and successfully analyzed using cancer gene panel analysis. Blood samples from 11 patients with breast cancer were collected and CTCs enriched for using size-based filtration. The enriched CTCs were analyzed using immunofluorescence staining with antibodies directed against epithelial cell adhesion molecule (EpCAM) and cluster of differentiation 45. The genomic DNA of CTCs was extracted, amplified and 50 genes screened for mutations using the Ion AmpliSeq™ Cancer Hotspot Panel v2. EpCAM staining detected CTCs in 10/11 patients and the average CTC count was 3.9 in 5 ml blood. The average purity of enriched CTCs was 14.2±29.4% and the average amount of amplified DNA was 28.6±11.9 µg. Catalogue Of Somatic Mutations In Cancer mutations were detected in the CTCs and included IDH2, TP53, NRAS, IDH1, PDGFRA, HRAS, STK11, EGFR, PTEN, MLH1, PIK3CA, CDKN2A, KIT and SMARCB1. In conclusion, a novel size-based filtration approach for the isolation of CTCs was evaluated and successfully applied for the genomic analysis of CTCs from patients with breast cancer.

Single cell sequencing: a distinct new field

Single cell sequencing (SCS) has become a new approach to study biological heterogeneity. The advancement in technologies for single cell isolation, amplification of genome/transcriptome and next-generation sequencing enables SCS to reveal the inherent properties of a single cell from the large scale of the genome, transcriptome or epigenome at high resolution. Recently, SCS has been widely applied in various clinical and research fields, such as cancer biology and oncology, immunology, microbiology, neurobiology and prenatal diagnosis. In this review, we will discuss the development of SCS methods and focus on the latest clinical and research applications of SCS.

Circulating Tumor Cells: From Theory to Nanotechnology-Based Detection

Cancer stem cells with stem-cell properties are regarded as tumor initiating cells. Sharing stem-cell properties, circulating tumor cells (CTCs) are responsible for the development of metastasis, which significant affects CTC analysis in clinical practice. Due to their extremely low occurrence in blood, however, it is challenging to enumerate and analyze CTCs. Nanotechnology is able to address the problems of insufficient capture efficiency and low purity of CTCs owing to the unique structural and functional properties of nanomaterials, showing strong promise for CTC isolation and detection. In this review, we discuss the role of stem-like CTCs in metastases, provide insight into recent progress in CTC isolation and detection approaches using various nanoplatforms, and highlight the role of nanotechnology in the advancement of CTC research.

Improving sensitivity and specificity of capturing and detecting targeted cancer cells with anti-biofouling polymer coated magnetic iron oxide nanoparticles

Detecting circulating tumor cells (CTCs) with high sensitivity and specificity is critical to management of metastatic cancers. Although immuno-magnetic technology for in vitro detection of CTCs has shown promising potential for clinical applications, the biofouling effect, i.e., non-specific adhesion of biomolecules and non-cancerous cells in complex biological samples to the surface of a device/probe, can reduce the sensitivity and specificity of cell detection. Reported herein is the application of anti-biofouling polyethylene glycol-block-allyl glycidyl ether copolymer (PEG-b-AGE) coated iron oxide nanoparticles (IONPs) to improve the separation of targeted tumor cells from aqueous phase in an external magnetic field. PEG-b-AGE coated IONPs conjugated with transferrin (Tf) exhibited significant anti-biofouling properties against non-specific protein adsorption and off-target cell uptake, thus substantially enhancing the ability to target and separate transferrin receptor (TfR) over-expressed D556 medulloblastoma cells. Tf conjugated PEG-b-AGE coated IONPs exhibited a high capture rate of targeted tumor cells (D556 medulloblastoma cell) in cell media (58.7±6.4%) when separating 100 targeted tumor cells from 1×105 non-targeted cells and 41 targeted tumor cells from 100 D556 medulloblastoma cells spiked into 1mL blood. It is demonstrated that developed nanoparticle has higher efficiency in capturing targeted cells than widely used micron-sized particles (i.e., Dynabeads®).

The liquid biopsy in lung cancer

The incidence of lung cancer has significantly increased over the last century, largely due to smoking, and remains the most common cause of cancer deaths worldwide. This is often due to lung cancer first presenting at late stages and a lack of curative therapeutic options at these later stages. Delayed diagnoses, inadequate tumor sampling, and lung cancer misdiagnoses are also not uncommon due to the limitations of the tissue biopsy. Our better understanding of the tumor microenvironment and the systemic actions of tumors, combined with the recent advent of the liquid biopsy, may allow molecular diagnostics to be done on circulating tumor markers, particularly circulating tumor DNA. Multiple liquid biopsy molecular methods are presently being examined to determine their efficacy as surrogates to the tumor tissue biopsy. This review will focus on new liquid biopsy technologies and how they may assist in lung cancer detection, diagnosis, and treatment.

Detection of Circulating Tumor Cells in Breast Cancer Patients Using Cytokeratin-19 Real-Time RT-PCR

PURPOSE

The roles of circulating tumor cells (CTCs) as predictive and prognostic factors, as well as key mediators in the metastatic cascade, have been investigated. This study aimed to validate a method to quantify CTCs in peripheral blood using a real-time reverse transcriptase polymerase chain reaction (RT-PCR) assay for cytokeratin (CK)-19 and to evaluate the utility of this assay in detecting CTCs in breast cancer patients.

MATERIALS AND METHODS

Real-time monitoring PCR of fluorescently labeled specific hybridization probes for CK-19 mRNA was established. Peripheral blood samples from 30 healthy donors, 69 patients with early breast cancer, 47 patients with locally advanced breast cancer, and 126 patients with metastatic breast cancer were prospectively obtained and analyzed for CTC detection.

RESULTS

CK-19 mRNA was not detectable in healthy subjects using the real-time RT-PCR method. The detection rates of CK-19 mRNA in breast cancer patients were 47.8% for early breast cancer (33/69), 46.8% for locally advanced breast cancer (22/47), and 61.1% for metastatic breast cancer (77/129). The detection rate of CK-19-positive CTCs in metastatic disease was slightly higher than early or locally advanced breast cancer; however, the detection rate according to disease burden was not statistically different (p=0.097). The detection rate was higher in patients with pleural metastasis (p=0.045). CTC detection was associated with poor survival (p=0.014).

CONCLUSION

A highly specific and sensitive CK-19 mRNA-based method to detect CTCs in peripheral blood in breast cancer patients can be used in further prospective studies to evaluate the predictive and prognostic importance of CTCs.

Multispectral Imaging Analysis of Circulating Tumor Cells in Negatively Enriched Peripheral Blood Samples

A variety of biomarkers are present on cells in peripheral blood of patients with a variety of disorders, including solid tumor malignancies. While rare, characterization of these cells for specific protein levels with the advanced technology proposed, will lead to future validation studies of blood samples as "liquid biopsies" for the evaluation of disease status and therapeutic response. While circulating tumor cells (CTCs) have been isolated in the blood samples of patients with solid tumors, the exact role of CTCs as clinically useful predictive markers is still debated. Current commercial technology has significant bias in that a positive selection technology is used that preassumes specific cell surface markers (such as EpCAM) are present on CTCs. However, CTCs with low EpCAM expression have been experimentally demonstrated to be more likely to be missed by this method. In contrast, this application uses a previously developed, technology that performs a purely negative enrichment methodology on peripheral blood, yielding highly enriched blood samples that contain CTCs as well as other, undefined cell types. The focus of this contribution is the use of multispectral imaging of epifluorescent, microscopic images of these enriched cells in order to help develop clinically relevant liquid biopsies from peripheral blood samples.

Enumeration and molecular characterization of circulating tumor cell using an in vivo capture system in squamous cell carcinoma of head and neck

Objective

Detection rate and isolation yield of circulating tumor cell (CTC) are low in squamous cell carcinoma of head and neck (SCCHN) with in vitro approaches due to limited sample volumes. In this study, we applied the CellCollector to capture CTC in vivo from peripheral blood.

Methods

In total, the study included 22 cases with 37 times of detection. All of the patients were newly diagnosed with locally advanced or metastatic SCCHN, including laryngocarcinoma (40.9%, 9/22) and hypopharyngeal carcinoma (59.1%, 13/22). All patients received CTC analysis before treatment. Three patients received induction chemotherapy. Sixteen patients received surgical therapy, of which 13 patients received postoperative detection. Two patients received both induction chemotherapy and surgery treatment. Patients underwent two successive CellCollector applications 24 h before and 7 d after surgical therapy. Nine healthy volunteers were enrolled as the control group. Epidermal growth factor receptor variant type III (EGFRVIII) expression was analyzed with fluorescent dye labeled antibody.

Results

With CellCollector isolation, 72.7% (16/22) of the patients were positive for ≥1 CTC (CTC; range, 1–17 cells) before treatments and 46.7% (7/15) of patients were CTC positive for ≥1 CTC (CTC; range, 1–29 cells) after surgical therapy. Moreover, the detection rate of CellCollector (82.4%, 14/17; CTC count range, 0–17) in advanced SCCHN (stage III–IV) was much higher than that in early stages (stage I–II, 40.0%, 2/5; CTC count range, 0–2) (P<0.05). EGFRVIII expression of CTC was also analyzed with fluorescence staining. One CTC^EGFRVIII-positive patient was detected from six CTC-positive patients, and the positive expression of EGFRVIII was also found in the tumor tissue of this patient.

Conclusions

In vivo detection of CTCs had high sensitivity in SCCHN, which might improve CTC application in clinic.

Detection and Enumeration of Circulating Tumor Cells with Invasive Phenotype

Circulating tumor cells (CTCs) disseminate from solid primary cancers into the peripheral blood and lymphatic vessels and can lead to metastatic tumor development; thus, CTC assays are an important clinical tool for monitoring progression and evaluating prognosis in cancer. However, CTCs are limited in number and heterogeneous in their biological and physical properties, making their detection, isolation, and enumeration a major challenge. To overcome these difficulties, novel techniques have been developed to detect and enumerate CTCs with an invasive phenotype. In this chapter, we will summarize these recently developed methods and detail two novel methods for capturing and enriching CTCs on the basis of their viability and their invasive properties.

Strategies for obtaining bone biopsy specimens from breast cancer patients - Past experience and future directions

Background

Cancer and its treatment can have multiple effects on the bone. Despite the widespread use of in vivo and in vitro models, it is still necessary to understand these effects in humans. Obtaining human bone biopsies is technically challenging and in this article we review the experiences from the Ottawa Bone Oncology Program.

Methods

A series of bone biopsy studies in breast cancer patients with and without bone metastasis have been performed. We reviewed the results of these studies and present them in a descriptive manner. We discuss lessons learned from each project and how they have affected future directions for research.

Results

Since 2009, 5 studies have been performed accruing 97 breast cancer patients. Study endpoints have ranged from comparing the yield of malignant cells from CT-guided versus standard iliac crest biopsies, to studies assessing the feasibility of micro-CT analysis on Jedhadi trephines to evaluate bisphosphonate effects on bone micro-architecture. More recently, we have assessed the feasibility of performing repeat bone biopsies in the same patient as well as evaluating the practicality of obtaining bone tissue at the time of orthopaedic surgery.

Conclusion

Human bone tissue is an important biological resource. Our experience suggests that obtaining bone biopsies is feasible and can yield adequate amount of tumour cells for many studies. However, these remain technically challenging specimens to obtain and given the rapid advances in cancer therapeutics and the use of potent adjuvant bone-targeted agents, more centres need to be involved in these types of studies.

A blood-based gene expression and signaling pathway analysis to differentiate between high and low grade gliomas

The aims of the present study were to undertake gene expression profiling of the blood of glioma patients to determine key genetic components of signaling pathways and to develop a panel of genes that could be used as a potential blood-based biomarker to differentiate between high and low grade gliomas, non-gliomas and control samples. In this study, blood samples were obtained from glioma patients, non-glioma and control subjects. Ten samples each were obtained from patients with high and low grade tumours, respectively, ten samples from non-glioma patients and twenty samples from control subjects. Total RNA was isolated from each sample after which first and second strand synthesis was performed. The resulting cRNA was then hybridized with the Agilent Whole Human Genome (4×44K) microarray chip according to the manufacturer's instructions. Universal Human Reference RNA and samples were labeled with Cy3 CTP and Cy5 CTP, respectively. Microarray data were analyzed by the Agilent Gene Spring 12.1V software using stringent criteria which included at least a 2-fold difference in gene expression between samples. Statistical analysis was performed using the unpaired Student's t-test with a P<0.01. Pathway enrichment was also performed, with key genes selected for validation using droplet digital polymerase chain reaction (ddPCR). The gene expression profiling indicated that were a substantial number of genes that were differentially expressed with more than a 2-fold change (P<0.01) between each of the four different conditions. We selected key genes within significant pathways that were analyzed through pathway enrichment. These key genes included regulators of cell proliferation, transcription factors, cytokines and tumour suppressor genes. In the present study, we showed that key genes involved in significant and well established pathways, could possibly be used as a potential blood-based biomarker to differentiate between high and low grade gliomas, non-gliomas and control samples.

EpCAM based capture detects and recovers circulating tumor cells from all subtypes of breast cancer except claudin-low

Purpose

The potential utility of circulating tumor cells (CTCs) as liquid biopsies is of great interest. We hypothesized that CTC capture using EpCAM based gating is feasible for most breast cancer subtypes.

Results

Cancer cells could be recovered from all intrinsic subtypes of breast cancer with IE/FACS, however, claudin-low cell lines showed very low capture rates compared to the four other groups (p = 0.03). IE/FACS detection of CTC mimic cells was time sensitive, emphasizing controlling for pre-analytic variables in CTC studies. Median fluorescent intensity for flow cytometry and RNA flow cell type characterization were highly correlated, predicting for CTC isolation across molecular subtypes. RNA-Seq of IE/FACS sorted single cell equivalents showed high correlation compared to bulk cell lines, and distinct gene expression signatures compared to PB.

Materials and Methods

Ten cell lines representing all major subtypes of breast cancer were spiked (as CTC mimics) into and recovered from peripheral blood (PB) using immunomagnetic enrichment followed by fluorescence-activated cell sorting (IE/FACS). Flow cytometry and RNA flow were used to quantify the expression of multiple breast cancer related markers of interest. Two different RNA-Seq technologies were used to analyze global gene expression of recovered sorted cells compared to bulk cell lines and PB.

Conclusions

EpCAM based IE/FACS detected and captured a portion of spiked cells from each of the 10 cell lines representing all breast cancer subtypes, including basal-like but not claudin-low cancers. The assay allows for the isolation of high quality RNA suitable for accurate RNA-Seq of heterogeneous rare cell populations.

Neovasculature and circulating tumor cells dual-targeting nanoparticles for the treatment of the highly-invasive breast cancer

Antiangiogenesis therapy has been served as a potent cancer treatment strategy for decades, yet disrupting neovasculature would provoke tumor cells into invasive growth and result in distal metastasis. The basic cause of cancer metastasis can be traced down to the presence of circulating tumor cells (CTCs) which detach from primary tumor site and act as 'seeds'. Epithelial cell adhesion molecule (EpCAM) is a potential biomarker for selective capture of epithelium-derived CTCs. Here, we integrated tumor neovessles-targetable ligands K237 peptide with Ep23 aptamer against EpCAM into a single drug-loaded nanoplatform using paclitaxel (PTX) as the model drug, aiming at damaging the primary tumor and neutralizing CTCs simultaneously to achieve a synergistic anti-tumor therapeutic effect. Enhanced cellular uptake, cell apoptosis-induction and cell-viability inhibition efficiency of the peptide and aptamer dual-functionalized nanoparticles (dTNP) were observed in both human umbilical vein endothelial cells (HUVEC) and 4T1 cells in vitro. Using cone-and-plate viscometer to create venous flow velocity, dTNP was also found to be able to capture CTCs under shear stress. The CTC-targeting and neutralization effect of dTNP in bloodstream and 4T1-GFP cell-derived lung metastasis mice model was confirmed via in vivo flow cytometry (IVFC), intravital imaging and confocal microscopy analysis. As a result, the orthotropic breast tumor-bearing mice administrated with PTX-loaded dTNP exhibited the optimal therapeutic effect. Taken together, the findings here provided direct evidence that the tumor neovasculature and CTCs dual-targeting drug delivery system could provide a novel modality for the treatment of highly-invasive breast cancer.

Cancer cells enter dormancy after cannibalizing mesenchymal stem/stromal cells (MSCs)

Patients with breast cancer often develop malignant regrowth of residual drug-resistant dormant tumor cells years after primary treatment, a process defined as cancer relapse. Deciphering the causal basis of tumor dormancy therefore has obvious therapeutic significance. Because cancer cell behavior is strongly influenced by stromal cells, particularly the mesenchymal stem/stromal cells (MSCs) that are actively recruited into tumor-associated stroma, we assessed the impact of MSCs on breast cancer cell (BCC) dormancy. Using 3D cocultures to mimic the cellular interactions of an emerging tumor niche, we observed that MSCs sequentially surrounded the BCCs, promoted formation of cancer spheroids, and then were internalized/degraded through a process resembling the well-documented yet ill-defined clinical phenomenon of cancer cell cannibalism. This suspected feeding behavior was less appreciable in the presence of a rho kinase inhibitor and in 2D monolayer cocultures. Notably, cannibalism of MSCs enhanced survival of BCCs deprived of nutrients but suppressed their tumorigenicity, together suggesting the cancer cells entered dormancy. Transcriptome profiles revealed that the resulting BCCs acquired a unique molecular signature enriched in prosurvival factors and tumor suppressors, as well as inflammatory mediators that demarcate the secretome of senescent cells, also referred to as the senescence-associated secretory phenotype. Overall, our results provide intriguing evidence that cancer cells under duress enter dormancy after cannibalizing MSCs. Importantly, our practical 3D coculture model could provide a valuable tool to understand the antitumor activity of MSCs and cell cannibalism further, and therefore open new therapeutic avenues for the prevention of cancer recurrence.

Spontaneous metastases in immunocompetent mice harboring a primary tumor driven by oncogene latent membrane protein 1 from Epstein-Barr virus

Background

In vitro and clinical studies suggest that the oncogene LMP1 (latent membrane protein 1) encoded by Epstein–Barr virus (EBV) plays a role in the development of nasopharyngeal carcinoma (NPC) and the formation of metastases in immunocompetent individuals. However, whether LMP1 itself is sufficient to drive these events in immunocompetent hosts remains elusive due to the lack of appropriate experimental models. The aim of this study was to study LMP1-dependent tumorigenesis and metastasis in BALB/c mice inoculated with BALB/c-3T3 cells expressing N-LMP1 (a Taiwanese NPC variant).

Methods

Following cancer cell inoculation, metastasis formation was monitored over time using PCR analysis of LMP1 as tumor marker. We also used a luciferase (Luc)-containing N-LMP1 and bioluminescent imaging (BLI) to monitor metastasis formation in a non-invasive manner.

Results

N-LMP1 appeared early in draining lymph nodes and in various distant organs before the rapid growth of the primary tumor. Lung metastasis was observed by BLI and further confirmed by histological examination. Furthermore, we detected luciferase signals in the lungs, even before the animals were sacrificed.

Conclusions

Our results demonstrate the high metastatic character of N-LMP1 in immunocompetent hosts. Systemic tumor dissemination occurs even before aggressive tumor growth at the primary site, suggesting that early treatment of primary LMP1-associated tumors and distant micro-metastases is critical to achieve positive results.

Are disseminated tumor cells in bone marrow and tumor-stroma ratio clinically applicable for patients undergoing surgical resection of primary colorectal cancer? The Leiden MRD study

Purpose

Current TNM staging does not appropriately identify high-risk colorectal cancer (CRC) patients. The aim of this study was to evaluate whether the presence of disseminated tumor cells (DTCs) in the bone marrow (BM) and the presence of stroma in the primary tumor, i.e., the tumor-stroma ratio (TSR), in patients undergoing surgical resection of primary CRC provides information relevant for disease outcome.

Methods

Patients with primary CRC (n = 125), consecutively admitted for curative resection between 2001 and 2007, were included in the study. All patients underwent BM aspiration before surgery. Detection of tumor cells was performed using immunocytochemical staining for cytokeratin (CK-ICC). The TSR was determined on diagnostic H&E stained sections of primary tumors.

Results

DTCs were detected in the BM of 23/125 patients (18 %). No association was found between BM status and overall survival (HR 0.97 (95 % CI 0.45–2.09), p = 0.93). Also, no significant difference was found in their 5-year survival rate (resp. 72 % and 68 % for BM-positive versus BM-negative patients). The TSR was found to be associated with a worse overall survival (HR 2.16, 95 % CI 1.02–4.57, p = 0.04) with 5-year survival rates of 84 % versus 62 % for stroma-low and stroma-high patients, respectively. No relation was found between the presence of DTCs and TSR.

Conclusions

Our data indicate that the presence of DTCs in the BM of CRC patients is not associated with disease outcome. The TSR was, however, found to be associated with a worse overall survival, which indicates that for CRC the tumor microenvironment plays an important role in its behavior and prognosis.

Approaches to isolation and molecular characterization of disseminated tumor cells

Micrometastatic cells in the bone marrow, now usually referred to as “disseminated tumor cells (DTCs)”, can be detected in early stage cancer patients. It has been hypothesized that DTCs represent key intermediates in the metastatic process as possible precursors of bone and visceral metastases, and are indicators of metastatic potential. Indeed, multiple clinical studies have unequivocally demonstrated the prognostic value of these cells in breast and other cancers, as DTCs have been associated with adverse outcomes, including inferior overall and disease-free survival. Despite this established clinical significance, the molecular nature of DTCs remains elusive. The complexity of the bone marrow poses a unique challenge in the isolation and direct characterization of these rare cells. However, recent advances in rare-cell technology along with technical improvements in analyzing limited cell inputs have enabled the molecular profiling of DTCs. In this review, we discuss research featuring the isolation and genomic analysis of DTCs. Emerging work on the molecular characterization of DTCs is now providing new insights into the biology of these cells.

Detection and enumeration of circulating tumor cells based on their invasive property

Circulating tumor cells (CTCs) are in limited numbers and heterogeneous, making their detection, isolation, and enumeration a major challenge. To overcome these difficulties, we developed a novel method to detect and enumerate CTCs with invasive property. Our assay consists of three simple steps: enrichment, Matrigel invasion assay, and immunostaining. We have validated this method using mouse xenograft tumor models and confirmed its utility in human cancer patients. Our method does not require special equipment and antigen expression for CTC selection, is less likely to be affected by the heterogeneity of the CTCs, and could be applicable to virtually all cancers. Most important, our method enumerates invasive CTCs, which may allow more accurate correlations with clinical outcome and treatment response compared with other CTC detection methods.

Characterization of cancer stem cells from different grades of human colorectal cancer

Colorectal cancer (CRC) is one of the most common solid tumors worldwide. Recent evidence suggests that a population of cancer cells, called cancer stem cells (CSCs), is responsible for tumor heterogeneity, invasion, metastasis, therapeutic resistance, and recurrence of CRC. The isolation and characterization of CSCs using cell surface markers have been reported previously with varying results. In this study, we investigated a panel of four putative CSC markers, CD44, CD24, CD166, and EpCAM, to define CRC-CSC. Paraffin embedded tissue samples from different grades of primary, untreated CRC were analyzed for the expression of four CSC markers CD44, CD326, CD24, and CD166, using immunohistochemistry. Flow cytometric analysis of CRC-CSC from HT29 (low grade) and HCT116 (high grade) human colorectal cancer cell lines was done. Marker-based isolation of CSC and non-CSC-bulk-tumor cells from HT29 was done using FACS, and tumor sphere assay was performed. There was a statistically significant difference (p < 0.05) in the expression of CD44, CD326, and CD166 between cases and controls. A novel cutoff distribution of CD44 and CD166 was suggested to help for better immunohistochemical analysis of CRC. Higher prevalence of CSC was seen in high-grade CRC as compared to low-grade CRC. Sorted and cultured CD44 + CD166+ cells formed tumor spheres, suggesting that these cells, having properties of self renewal and anchorage independent proliferation, were in fact CSC. Hence, CD44 and CD166 may serve as good CRC-CSC markers when used together with novel cutoff immunohistochemistry (IHC) expression levels.

Nanoroughened adhesion-based capture of circulating tumor cells with heterogeneous expression and metastatic characteristics

BACKGROUND

Circulating tumor cells (CTCs) have shown prognostic relevance in many cancer types. However, the majority of current CTC capture methods rely on positive selection techniques that require a priori knowledge about the surface protein expression of disseminated CTCs, which are known to be a dynamic population.

METHODS

We developed a microfluidic CTC capture chip that incorporated a nanoroughened glass substrate for capturing CTCs from blood samples. Our CTC capture chip utilized the differential adhesion preference of cancer cells to nanoroughened etched glass surfaces as compared to normal blood cells and thus did not depend on the physical size or surface protein expression of CTCs.

RESULTS

The microfluidic CTC capture chip was able to achieve a superior capture yield for both epithelial cell adhesion molecule positive (EpCAM+) and EpCAM- cancer cells in blood samples. Additionally, the microfluidic CTC chip captured CTCs undergoing transforming growth factor beta-induced epithelial-to-mesenchymal transition (TGF-β-induced EMT) with dynamically down-regulated EpCAM expression. In a mouse model of human breast cancer using EpCAM positive and negative cell lines, the number of CTCs captured correlated positively with the size of the primary tumor and was independent of their EpCAM expression. Furthermore, in a syngeneic mouse model of lung cancer using cell lines with differential metastasis capability, CTCs were captured from all mice with detectable primary tumors independent of the cell lines' metastatic ability.

CONCLUSIONS

The microfluidic CTC capture chip using a novel nanoroughened glass substrate is broadly applicable to capturing heterogeneous CTC populations of clinical interest independent of their surface marker expression and metastatic propensity. We were able to capture CTCs from a non-metastatic lung cancer model, demonstrating the potential of the chip to collect the entirety of CTC populations including subgroups of distinct biological and phenotypical properties. Further exploration of the biological potential of metastatic and presumably non-metastatic CTCs captured using the microfluidic chip will yield insights into their relevant differences and their effects on tumor progression and cancer outcomes.

MINDEC-An Enhanced Negative Depletion Strategy for Circulating Tumour Cell Enrichment

Most current methods of circulating tumour cell (CTC) enrichment target the epithelial protein EpCAM, which is commonly expressed in adenocarcinoma cells. However, such methods will not recover the fraction of CTCs that have a non-epithelial phenotype due to epithelial–mesenchymal transition. For phenotype-independent CTC enrichment, we developed a new enhanced negative depletion strategy—termed MINDEC—that is based on multi-marker (CD45, CD16, CD19, CD163, and CD235a/GYPA) depletion of blood cells rather than targeted enrichment of CTCs. Here we validated the performance of MINDEC using epithelial and mesenchymal cancer cell lines, demonstrating a mean recovery of 82 ± 10%, high depletion (437 ± 350 residual white blood cells (WBCs)/mL peripheral blood), linearity between spiked and recovered cells (correlation coefficient: r = 0.995), and a low detection limit (≥1 cell recovered in all four replicates spiked with 3 cells). For clinical validation of this method, we enumerated CTCs in peripheral blood samples from patients with metastatic pancreatic cancer, detecting CTCs in 15 of 21 blood samples (71%) from 9 patients. The promising performance of the MINDEC enrichment strategy in our study encourages validation in larger clinical trials.

Liquid biopsy in patients with pancreatic cancer: Circulating tumor cells and cell-free nucleic acids

Despite recent advances in surgical techniques and perioperative management, the prognosis of pancreatic cancer (PCa) remains extremely poor. To provide optimal treatment for each patient with Pca, superior biomarkers are urgently needed in all phases of management from early detection to staging, treatment monitoring, and prognosis. In the blood of patients with cancer, circulating tumor cells (CTCs) and cell-free nucleic acids (cfNAs), such as DNA, mRNA, and noncoding RNA have been recognized. In the recent years, their presence in the blood has encouraged researchers to investigate their potential use as novel blood biomarkers, and numerous studies have demonstrated their potential clinical utility as a biomarker for certain types of cancer. This concept, called “liquid biopsy” has been focused on as a less invasive, alternative approach to cancer tissue biopsy for obtaining genetic and epigenetic aberrations that contribute to oncogenesis and cancer progression. In this article, we review the available literature on CTCs and cfNAs in patients with cancer, particularly focusing on PCa, and discuss future perspectives in this field.

Prognostic Value of Circulating Tumor Cells Identified Before Surgical Resection in Nonmetastatic Breast Cancer Patients

BACKGROUND

Circulating tumor cells (CTCs) can be identified in approximately 25% of nonmetastatic breast cancer patients, and data are emerging regarding their prognostic significance. We hypothesized that CTCs identified before resection of the primary tumor would predict worse outcomes in nonmetastatic breast cancer patients.

STUDY DESIGN

We performed CTC enumerations on 509 patients with nonmetastatic breast cancer as part of an IRB-approved study. The CTCs (per 7.5 mL blood) were identified using the CellSearch System (Janssen). The presence of ≥1 CTC meeting morphologic criteria for malignancy was considered a positive result. Log-rank test and Cox regression analysis were applied to establish the association of CTCs with relapse-free and overall survival.

RESULTS

Median follow-up was 48 months and mean age was 53 years. Fifty-nine percent of patients (299 of 509) had tumors larger than 2 cm, and 46% (234 of 509) had positive lymph nodes. One hundred sixty-six patients received neoadjuvant chemotherapy (NACT) before CTC assessment, and 343 patients were chemonaïve. One or more CTC was identified in 43 of 166 (26%) NACT treated patients, and in 81 of 343 (24%) chemonaïve patients. Circulating tumor cells were not associated with tumor size, grade, or lymph node status (p = NS). Detection of 1 or more CTCs predicted decreased relapse-free (log-rank p < 0.001, hazard ratio [HR] 2.72, 95% CI 1.57 to 4.72; p < 0.001) and overall survival (log-rank p = 0.02, HR 2.29, 95% CI 1.12 to 4.67; p = 0.03) at 48 months of follow-up.

CONCLUSIONS

One or more CTCs identified before resection of the primary breast tumor predicted worse relapse-free and overall survival, irrespective of primary tumor size, grade, or lymph node positivity.

Modeling selective elimination of quiescent cancer cells from bone marrow

Patients with many types of malignancy commonly harbor quiescent disseminated tumor cells in bone marrow. These cells frequently resist chemotherapy and may persist for years before proliferating as recurrent metastases. To test for compounds that eliminate quiescent cancer cells, we established a new 384-well 3D spheroid model in which small numbers of cancer cells reversibly arrest in G1/G0 phase of the cell cycle when cultured with bone marrow stromal cells. Using dual-color bioluminescence imaging to selectively quantify viability of cancer and stromal cells in the same spheroid, we identified single compounds and combination treatments that preferentially eliminated quiescent breast cancer cells but not stromal cells. A treatment combination effective against malignant cells in spheroids also eliminated breast cancer cells from bone marrow in a mouse xenograft model. This research establishes a novel screening platform for therapies that selectively target quiescent tumor cells, facilitating identification of new drugs to prevent recurrent cancer.

Comparison between Three Promising ß-emitting Radionuclides, (67)Cu, (47)Sc and (161)Tb, with Emphasis on Doses Delivered to Minimal Residual Disease

PURPOSE: Radionuclide therapy is increasingly seen as a promising option to target minimal residual disease. Copper-67, scandium-47 and terbium-161 have a medium-energy β^- emission which is similar to that of lutetium-177, but offer the advantage of having diagnostic partner isotopes suitable for pretreatment imaging. The aim of this study was to compare the efficacy of ⁶⁷Cu, ⁴⁷Sc and ¹⁶¹Tb to irradiate small tumors.

METHODS: The absorbed dose deriving from a homogeneous distribution of ⁶⁷Cu, ⁴⁷Sc or ¹⁶¹Tb in water-density spheres was calculated with the Monte Carlo code CELLDOSE. The diameters of the spheres ranged from 5 mm to 10 µm, thus simulating micrometastases or single tumor cells. All electron emissions, including β^- spectra, Auger and conversion electrons were taken into account. Because these radionuclides differ in electron energy per decay, the simulations were run assuming that 1 MeV was released per µm³, which would result in a dose of 160 Gy if totally absorbed.

RESULTS: The absorbed dose was similar for the three radionuclides in the 5-mm sphere (146-149 Gy), but decreased differently in smaller spheres. In particular, ¹⁶¹Tb delivered higher doses compared to the other radionuclides. For instance, in the 100-µm sphere, the absorbed dose was 24.1 Gy with ⁶⁷Cu, 14.8 Gy with ⁴⁷Sc and 44.5 Gy with ¹⁶¹Tb. Auger and conversion electrons accounted for 71% of ¹⁶¹Tb dose. The largest dose differences were found in cell-sized spheres. In the 10-µm sphere, the dose delivered by ¹⁶¹Tb was 4.1 times higher than that from ⁶⁷Cu and 8.1 times that from ⁴⁷Sc.

CONCLUSION: ¹⁶¹Tb can effectively irradiate small tumors thanks to its decay spectrum that combines medium-energy β^- emission and low-energy conversion and Auger electrons. Therefore ¹⁶¹Tb might be a better candidate than ⁶⁷Cu and ⁴⁷Sc for treating minimal residual disease in a clinical setting.