Circulating tumor cells in breast cancer: fiction or reality?

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

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

Designing Multicomponent Nanosystems for Rapid Detection of Circulating Tumor Cells

Detection of circulating tumor cells (CTCs) in the blood circulation holds immense promise as it predicts the overall probability of patient survival. Therefore, CTC-based technologies are gaining prominence as a "liquid biopsy" for cancer diagnostics and prognostics. Here, we describe the design and synthesis of two distinct multicomponent magnetic nanosystems for rapid capture and detection of CTCs. The multifunctional Magneto-Dendrimeric Nano System (MDNS) composed of an anchoring dendrimer that is conjugated to multiple agents such as near infrared (NIR) fluorescent cyanine 5 NHS (Cy5), glutathione (GSH), transferrin (Tf), and iron oxide (Fe₃O₄) magnetic nanoparticle (MNP) for simultaneous tumor cell-specific affinity, multimodal high resolution confocal imaging, and cell isolation. The second nanosystem is a self-propelled microrocket that is composed of carbon nanotube (CNT), chemically conjugated with targeting ligand such as transferrin on the outer surface and Fe₃O₄ nanoparticles in the inner surface. The multicomponent nanosystems described here are highly efficient in targeting and isolating cancer cells thus benefiting early diagnosis and therapy of cancer.

CTCs in early breast cancer: A path worth taking

Circulating tumor cells (CTCs) are cellular elements of undeniable significance that spread from the tumor mass into the peripheral blood and constitute one of the main vehicles for disease diffusion. Their rarity, in addition to a number of molecular and cellular features, has severely impaired research and exploitation. CTCs have been evaluated in early breast cancer (EBC), although long from being fully accepted in this field also due to a lack of technical standardization. CTCs hold promise to be a powerful non-invasive real-time measurable biomarker in all disease stages. This hypothesis is particularly appealing in the adjuvant setting of breast cancer, as it still lacks a marker that could play a central role in monitoring disease-free intervals, predicting early relapse and guiding drug selection. This review aimed to discuss CTC characteristics and show the main results of CTC-research in EBC setting, stating the urgency to continue basic and translational research in this field to definitely translate this marker from bench to bedside.

Arterial Blood, Rather Than Venous Blood, is a Better Source for Circulating Melanoma Cells

Background

CTCs provide prognostic information and their application is under investigation in multiple tumor types. Of the multiple variables inherent in any such process, none is more important to outcome than the appropriateness of the sample source. To address this question, we investigated CTCs in paired peripheral venous and arterial blood specimens obtained from stage IV uveal melanoma patients.

Methods

Blood specimens were obtained from both common femoral arteries and antecubital veins in 17 uveal melanoma patients with multiple hepatic metastases for CTC measurements.

Finding

CTCs were detectable with greater frequency (100%) and in larger numbers (median 5, range 1 to 168) in all arterial blood specimens than in venous samples (52.9%; median 1, range 0 to 8). Patients with hepatic as well as extra-hepatic metastasis showed higher number of arterial CTCs, compared to patients with liver-only metastasis (p = 0.003). There was no significant association between the number of arterial CTCs and the tumor burden within the liver in patients who had liver-only metastases.

Interpretation

Our data indicate that arterial blood specimens might be a better source of circulating uveal melanoma cells. Although less conveniently processed, perhaps arterial blood should be evaluated as sample source for measurement of CTCs.

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CTCs were detectable in 100% of arterial blood obtained from metastatic uveal melanoma patients, while only 53% of venous blood was positive for CTCs.

CTCs have been investigated to provide prognostic information in multiple tumor types. Of the multiple variables, none is more important than the appropriateness of the sample source. Blood specimens were obtained from both femoral arteries and antecubital veins in 17 uveal melanoma patients with multiple hepatic metastases. CTCs were detectable with greater frequency (100%) and in larger numbers in all arterial blood specimens than in venous samples (52.9%). Our data indicate that arterial blood specimens might be a better source of circulating uveal melanoma cells. Although less convenient, arterial blood should be evaluated as sample source for measurement of CTCs.

Circulating tumor cells: approaches to isolation and characterization

Circulating tumor cells (CTCs) shed from primary and metastatic cancers are admixed with blood components and are thus rare, making their isolation and characterization a major technological challenge. CTCs hold the key to understanding the biology of metastasis and provide a biomarker to noninvasively measure the evolution of tumor genotypes during treatment and disease progression. Improvements in technologies to yield purer CTC populations amenable to better cellular and molecular characterization will enable a broad range of clinical applications, including early detection of disease and the discovery of biomarkers to predict treatment responses and disease progression.

Disseminated and circulating tumor cells: Role in effective cancer management

Dissemination of tumor cells from primary tumors in the circulatory system is an early event in carcinogenesis. The presence of these single disseminated tumor cells (DTC) in peripheral blood, bone marrow and distant organs is the rationale for adjuvant systemic treatment. Detection of DTC in bone marrow aspirates from breast cancer patients and other solid tumors at the primary diagnosis impacts the prognosis of disease. In peripheral blood these cells are termed as circulating tumor cells (CTC). Due to technical difficulties the clinical significance of CTC detection at early stages is less established. This review focuses on available techniques for detection of DTC and CTC, recent technical advances in development of more sensitive microfluidic methods for capture of DTC and CTC and possibilities for further detection and their potential molecular characterization. Not only the clinical significance of DTC but also the presence of cancer stem cells in dissemination clearly demonstrates the need for development of sensitive technologies allowing for definition of biomarkers and molecular targets on cells in dissemination, thus eventually leading to optimization of systemic therapies.

Circulating tumor cell analysis: technical and statistical considerations for application to the clinic

Solid cancers are a leading cause of death worldwide, primarily due to the failure of effective clinical detection and treatment of metastatic disease in distant sites. There is growing evidence that the presence of circulating tumor cells (CTCs) in the blood of cancer patients may be an important indicator of the potential for metastatic disease and poor prognosis. Technological advances have now facilitated the enumeration and characterization of CTCs using methods such as PCR, flow cytometry, image-based immunologic approaches, immunomagnetic techniques, and microchip technology. However, the rare nature of these cells requires that very sensitive and robust detection/enumeration methods be developed and validated in order to implement CTC analysis for widespread use in the clinic. This review will focus on the important technical and statistical considerations that must be taken into account when designing and implementing CTC assays, as well as the subsequent interpretation of these results for the purposes of clinical decision making.

Emerging drugs in metastatic breast cancer

BACKGROUND

Breast cancer is the most common cancer among women and comprises 26% of all cancers diagnosed in women in the United States. Among presenting patients, 3 - 6% already have metastatic disease, and 50 - 70% of the remaining patients develop systemic relapse. Recently many new drugs, particularly molecular targeted therapies, have been developed in the field.

OBJECTIVE

To review the current and emerging data on the treatment of metastatic breast cancer, with emphasis on novel therapies that show promise.

METHODS

PubMed and ASCO annual meeting abstracts were used for a literature search.

RESULTS/CONCLUSIONS

Despite improved response rates, conventional treatments still result only in transient remission in most cases. New therapeutic alternatives and new strategies to overcome drug resistance are needed to improve these results.

Circulating tumor cells (CTCs): detection methods and their clinical relevance in breast cancer

The enumeration of circulating tumor cells has long been regarded as an attractive diagnostic tool, as circulating tumor cells are thought to reflect aggressiveness of the tumor and may assist in therapeutic decisions in patients with solid malignancies. However, implementation of this assay into clinical routine has been cumbersome, as a validated test was not available until recently. Circulating tumor cells are rare events which can be detected specifically only by using a combination of surface and intracellular markers, and only recently a number of technical advances have made their reliable detection possible. Most of these new techniques rely on a combination of an enrichment and a detection step. This review addresses the assays that have been described so far in the literature, including the enrichment and detection steps and the markers used in these assays. We have focused on breast cancer as most clinical studies on CTC detection so far have been done in these patients.

Endocrine therapy for the treatment of postmenopausal women with breast cancer

The treatment of women with estrogen receptor-positive breast cancer has advanced significantly in the past decade. Tamoxifen was the gold standard hormonal therapy for breast cancer until the introduction of aromatase inhibitors and fulvestrant. Many of these new treatments are useful only for patients who are postmenopausal. There are data to support the use of these new agents both in the metastatic and adjuvant settings. Here, we briefly review the recent clinical trials supporting the use of these agents in both the adjuvant and metastatic settings. We will discuss possible mechanisms of resistance to endocrine agents that could be exploited therapeutically to improve the outcome for patients with hormone receptor-positive breast cancers.