Circulating tumor cells (CTCs) from metastatic breast cancer patients linked to decreased immune function and response to treatment

Biomarkers of minimal residual disease and treatment

Minimal residual disease (MRD) has been defined as a very small numbers of cancer cells that remain in the body after curative treatment. Its presence or absence will ultimately determine prognosis. With the introduction of new technologies the presence of MRD in patients with solid tumours can be detected and characterized. As MRD predicts future relapse, be it early or late treatment failure, in an otherwise asymptomatic patient its treatment and when to start treatment remains to be determined. Thus the concepts of personalized medicine using different biomarkers to classify the biological properties of MRD maybe come possible. Based on this determinations it may be possible to use targeted therapies rather than all patients with the same type of cancer receiving a standard treatment. However, it is important to understand the limitations of the different technologies, what these techniques are detecting and how they may help in the treatment of patients with cancer. The majority of published studies are in patients with metastatic cancer and there are few reports in patients with MRD. In this chapter the concept of MRD, the methods used to detect it and what treatments may be effective based on the biological characteristics of the tumour cells as determined by different biomarkers is reviewed. MRD depends on the phenotypic properties of the tumour cells to survive in their new environment and the anti-tumour immune response. This is a dynamic process and changes with time in the wake of immunosuppression caused by the tumour cells and/or the effects of treatment to select resistant tumour cells. With the use of biomarkers to typify the characteristics of MRD and the development of new drugs a personalized treatment can be designed rather than all patients given the same treatment. Patients who are initially negative for MRD may not require further treatment with liquid biopsies used to monitor the patients during follow-up in order to detect those patients who may become MRD positive. The liquid biopsy used during the follow up of MRD positive patients can be used to detect changes in the biological properties of the tumour cells and thus may need treatment changes to overcome tumour cell resistance.

Circulating tumor cells and host immunity: A tricky liaison

During their dissemination, circulating tumor cells (CTCs) steadily face the immune system, which is a key player in the whole metastatic cascade, from intravasation to the CTC colonization of distant sites. In this chapter, we will go through the description of immune cells involved in this controversial dialogue encompassing both the anti-tumor activity and the tumor-promoting and immunosuppressive function mediated by several circulating immune effectors as natural killer (NK) cells, CD4+ and CD8+ T lymphocytes, T helper 17, regulatory T cells, neutrophils, monocytes, macrophages, myeloid-derived suppressor cells, dendritic cells, and platelets. Then, we will report on the same interaction from the CTCs point of view, depicting the direct and indirect mechanisms of crosstalk with the above mentioned immune cells. Finally, we will report the recent literature evidence on the potential prognostic role of the integrated CTCs and immune cells monitoring in cancer patients management.

Immune checkpoint HLA-E:CD94-NKG2A mediates evasion of circulating tumor cells from NK cell surveillance

Circulating tumor cells (CTCs), shed by primary malignancies, function as "seeds" for distant metastasis. However, it is still largely unknown how CTCs escape immune surveillance. Here, we characterize the transcriptomes of human pancreatic ductal adenocarcinoma CTCs, primary, and metastatic lesions at single-cell scale. Cell-interaction analysis and functional studies in vitro and in vivo reveal that CTCs and natural killer (NK) cells interact via the immune checkpoint molecule pair HLA-E:CD94-NKG2A. Disruption of this interaction by blockade of NKG2A or knockdown of HLA-E expression enhances NK-mediated tumor cell killing in vitro and prevents tumor metastasis in vivo. Mechanistic studies indicate that platelet-derived RGS18 promotes the expression of HLA-E through AKT-GSK3β-CREB signaling, and overexpression of RGS18 facilitates pancreatic tumor hepatic metastasis. In conclusion, platelet-derived RGS18 protects CTCs from NK-mediated immune surveillance by engaging the immune checkpoint HLA-E:CD94-NKG2A. Interruption of the suppressive signaling prevents tumor metastasis in vivo by immune elimination of CTCs.

Harnessing NK Cells to Control Metastasis

In recent years, tumor immunotherapy has produced remarkable results in tumor treatment. Nevertheless, its effects are severely limited in patients with low or absent pre-existing T cell immunity. Accordingly, metastasis remains the major cause of tumor-associated death. On the other hand, natural killer (NK) cells have the unique ability to recognize and rapidly act against tumor cells and surveil tumor cell dissemination. The role of NK cells in metastasis prevention is undisputable as an increase in the number of these cells mostly leads to a favorable prognosis. Hence, it is reasonable to consider that successful metastasis involves evasion of NK-cell-mediated immunosurveillance. Therefore, harnessing NK cells to control metastasis is promising. Circulating tumor cells (CTCs) are the seeds for distant metastasis, and the number of CTCs detected in the blood of patients with tumor is associated with a worse prognosis, whereas NK cells can eliminate highly motile CTCs especially in the blood. Here, we review the role of NK cells during metastasis, particularly the specific interactions of NK cells with CTCs, which may provide essential clues on how to harness the power of NK cells against tumor metastasis. As a result, a new way to prevent or treat metastatic tumor may be developed.

Cancer Stem Cells and Circulatory Tumor Cells Promote Breast Cancer Metastasis

Breast cancer (BC) is a highly metastatic, pathological cancer that significantly affects women worldwide. The mortality rate of BC is related to its heterogeneity, aggressive phenotype, and metastasis. Recent studies have highlighted that the tumor microenvironment (TME) is critical for the interplay between metastasis mediators in BC. BC stem cells, tumor-derived exosomes, circulatory tumor cells (CTCs), and signaling pathways dynamically remodel the TME and promote metastasis. This review examines the cellular and molecular mechanisms governing the epithelial to mesenchymal transition (EMT) that facilitate metastasis. This review also discusses the role of cancer stem cells (CSCs), tumor-derived exosomes, and CTs in promoting BC metastasis. Furthermore, the review emphasizes major signaling pathways that mediate metastasis in BC. Finally, the interplay among CSCs, exosomes, and CTCs in mediating metastasis have been highlighted. Therefore, understanding the molecular cues that mediate the association of CSCs, exosomes, and CTCs in TME helps to optimize systemic therapy to target metastatic BC.

Circulating Tumour Cell Numbers Correlate with Platelet Count and Circulating Lymphocyte Subsets in Men with Advanced Prostate Cancer: Data from the ExPeCT Clinical Trial (CTRIAL-IE 15-21)

Simple Summary

Cancer cells (CTCs) can be found in the bloodstream in men with advanced prostate cancer. Blood platelets, which normally help the blood to clot, may help the cancer cells to spread throughout the body by preventing the body’s immune system from finding and destroying them while they are in the bloodstream. Blood samples were taken from men with prostate cancer who were involved in the ExPeCT clinical trial, some of whom were taking part in a regular exercise programme. The numbers of CTCs, platelets and immune system cells were counted and compared. Blood samples with more CTCs had higher numbers of platelets and higher numbers of some types of immune system cells. Some differences were also found in men involved in the exercise programme. This study helps to show that CTCs numbers are related to platelet and immune cell numbers in the blood.

Abstract

Interactions between circulating tumour cells (CTCs) and platelets are thought to inhibit natural killer(NK)-cell-induced lysis. We attempted to correlate CTC numbers in men with advanced prostate cancer with platelet counts and circulating lymphocyte numbers. Sixty-one ExPeCT trial participants, divided into overweight/obese and normal weight groups on the basis of a BMI ≥ 25 or <25, were randomized to participate or not in a six-month exercise programme. Blood samples at randomization, and at three and six months, were subjected to ScreenCell filtration, circulating platelet counts were obtained, and flow cytometry was performed on a subset of samples (n = 29). CTC count positively correlated with absolute total lymphocyte count (r² = 0.1709, p = 0.0258) and NK-cell count (r² = 0.49, p < 0.0001). There was also a positive correlation between platelet count and CTC count (r² = 0.094, p = 0.0001). Correlation was also demonstrated within the overweight/obese group (n = 123, p < 0.0001), the non-exercise group (n = 79, p = 0.001) and blood draw samples lacking platelet cloaking (n = 128, p < 0.0001). By flow cytometry, blood samples from the exercise group (n = 15) had a higher proportion of CD3+ T-lymphocytes (p = 0.0003) and lower proportions of B-lymphocytes (p = 0.0264) and NK-cells (p = 0.015) than the non-exercise group (n = 14). These findings suggest that CTCs engage in complex interactions with the coagulation cascade and innate immune system during intravascular transit, and they present an attractive target for directed therapy at a vulnerable stage in metastasis.

Jinfukang inhibits lung cancer metastasis by upregulating CX3CL1 to recruit NK cells to kill CTCs

ETHNOPHARMACOLOGICAL RELEVANCE

Circulating tumor cells (CTCs) play an important role in tumor metastasis and may be a target for metastasis prevention. The traditional Chinese medicine Jinfukang functions to improve immunity, prevent metastasis, and prolong lung cancer patient survival periods. Yet, whether Jinfukang prevents metastasis by regulating immune cells to clearance CTCs is still unknown.

AIM OF THE STUDY

To explore the anti-metastasis mechanism of Jinfukang from the perspective of regulating NK cells to clear CTCs.

MATERIALS AND METHODS

CTC-TJH-01 cell was treated with Jinfukang. Cytokine chip was used to detect cytokines in cell culture supernatant. Lymphocyte recruitment assay was detected by Transwell and flow cytometry. Protein expression was analysis by Western blot. LDH kit was used to detect cytotoxicity. NOD-SCID mice used for tail vein injection to study lung metastasis.

RESULTS

Jinfukang could promote the expression and secretion of the chemokine CX3CL1 by CTCs. In addition, Jinfukang could promote the recruitment of natural killer (NK) cells by CTCs and significantly increase the cytotoxic effect of NK cells on CTCs. Moreover, Jinfukang could upregulate the expression of FasL and promote the secretion of TNF-α by NK cells and that NK cells could induce the apoptosis of CTCs through the Fas/FasL signaling pathway. Finally, we confirmed that Jinfukang could promote NK cells to kill CTCs and then inhibit lung cancer metastasis in vivo. The above effects of Jinfukang could be partially reversed by an anti-CX3CL1 mAb.

CONCLUSIONS

These results suggest that Jinfukang may prevent lung cancer metastasis by enhancing the clearance of CTCs in the peripheral blood by NK cells, providing evidence for the anti-metastasis effect of Jinfukang.

The association of the neutrophil-lymphocyte ratio with the presence of minimal residual disease and outcome in patients with Stage II colon cancer treated with surgery alone

AIM

Despite curative surgery, 25% of patients with Stage II colorectal cancer will relapse due to minimal residual disease (MRD). Markers of immune function, such as the neutrophil to lymphocyte ratio (NLR), may be associated with MRD defined by bone marrow micro-metastasis (mM) and circulating tumour cells (CTCs).

METHOD

A prospective cohort study of consecutive patients with Stage II colon cancer patients attended at a single centre between 2007 and 2014. Blood and bone marrow samples were taken to detect CTCs and mM using immunocytochemistry with anti-carcinoembryonic antigen 1 month after surgery. The NLR and absolute neutrophil and lymphocyte counts were determined immediately pre-surgery and 1 month post-surgery. These were compared with the sub-types of MRD: group I MRD(-); group II mM positive and group III CTC positive. Cut-off values of the NLR of >3.0 and >5.0 were used. Follow-up was for up to 5 years or relapse and disease-free survival (DFS) was calculated using Kaplan-Meier analysis.

RESULTS

In all, 181 patients (99 women) participated. Mean age was 68 years. Median follow-up was 4.04 years: I, N = 105; II, N = 36; III, N = 40. The NLR significantly decreased post-surgery only in group I patients. The frequency of NLR >3.0 and >5.0 was significantly higher in group III; between groups I and II there was no significant difference. 5-year DFS was 98% in group I, 68% in group II and 7% in group III.

CONCLUSIONS

Patients with a significantly higher immune dysfunction had a shorter time to disease progression, a worse DFS and the presence of CTCs.

Platelets, immune cells and the coagulation cascade; friend or foe of the circulating tumour cell?

Cancer cells that transit from primary tumours into the circulatory system are known as circulating tumour cells (CTCs). These cancer cells have unique phenotypic and genotypic characteristics which allow them to survive within the circulation, subsequently extravasate and metastasise. CTCs have emerged as a useful diagnostic tool using "liquid biopsies" to report on the metastatic potential of cancers. However, CTCs by their nature interact with components of the blood circulatory system on a constant basis, influencing both their physical and morphological characteristics as well as metastatic capabilities. These properties and the associated molecular profile may provide critical diagnostic and prognostic capabilities in the clinic. Platelets interact with CTCs within minutes of their dissemination and are crucial in the formation of the initial metastatic niche. Platelets and coagulation proteins also alter the fate of a CTC by influencing EMT, promoting pro-survival signalling and aiding in evading immune cell destruction. CTCs have the capacity to directly hijack immune cells and utilise them to aid in CTC metastatic seeding processes. The disruption of CTC clusters may also offer a strategy for the treatment of advance staged cancers. Therapeutic disruption of these heterotypical interactions as well as direct CTC targeting hold great promise, especially with the advent of new immunotherapies and personalised medicines. Understanding the molecular role that platelets, immune cells and the coagulation cascade play in CTC biology will allow us to identify and characterise the most clinically relevant CTCs from patients. This will subsequently advance the clinical utility of CTCs in cancer diagnosis/prognosis.

Loss of type I IFN responsiveness impairs natural killer cell antitumor activity in breast cancer

Competent type I IFN signaling is the lynchpin of most immune surveillance mechanisms and has recently proven critical to the efficacy of several anticancer agents. Expression of the type I IFN receptor, IFNAR, underpins type I IFN responsiveness in all cells and facilitates the activation and cytotoxic potential of lymphocytes, while loss of IFNAR on lymphocytes has previously been associated with tumor progression and poor patient survival. This study underscores the importance of intact type I IFN signaling to NK cells in the regulation of tumorigenesis and metastasis, whereby ablation of NK cell IFNAR1 impairs antitumor activity and tumor clearance. Using a preclinical model of triple negative breast cancer, we identified that intact IFNAR on NK cells is required for an effective response to type I IFN-inducing immunotherapeutics that may be mediated by pathways associated with NK cell degranulation. Taken together, these data provide a rationale for considering the IFNAR status on NK cells when devising therapeutic strategies aimed at inducing systemic type I IFN signaling in breast cancer.

Increased programmed death ligand (PD-L1) and cytotoxic T-lymphocyte antigen-4 (CTLA-4) expression is associated with metastasis and poor prognosis in malignant canine mammary gland tumours

Aberrant expression of immune check point molecules, programmed death ligand (PD-L1) and cytotoxic T-lymphocyte antigen-4 (CTLA-4) has been reported in many human cancers with increased protein and gene expression correlated with an aggressive behaviour in some neoplasms. Additionally, PD-L1 blockade has been shown to be an effective therapy for some human cancers. Canine mammary gland tumours have previously been shown to produce PD-L1 protein, but there are no previous studies investigating CTLA-4 in these common canine neoplasms. The present study investigated protein and gene expression of PD-L1 and CTLA-4 using immunohistochemistry and RT-PCR in 41 histologically-malignant, outcome-known CMGTs. The PD-L1 and CTLA-4 immunostaining scores of the mammary gland tumours that subsequently metastasised were significantly higher than those of tumours which did not metastasise (PD-L1: p =  0.005, CTLA-4: p =  0.003). Gene expression of PD-L1 and CTLA-4 was also significantly higher in tumours which subsequently metastasised (PD-L1: p =  0.023, CTLA-4: p =  0.022). Further, higher PD-L1 or CTLA-4 immunostaining scores correlated with shorter survival times of dogs (PD-L1: r_s = - 0.42, p =  0.008, CTLA-4: r_s = - 0.4, p =  0.01) while PD-L1 immunostaining was independently prognostic of survival time (Δ F = 4.9, p =  0.035). These findings suggest that higher protein and gene expression of PD-L1 and CTLA-4 by tumour cells increases the chances of metastasis and measuring these proteins may predict likely neoplasm behaviour. Additionally, if increased expression of these proteins promotes metastasis, blocking PD-L1 or CTLA-4 may be beneficial to treat canine mammary gland tumours.

Single-Cell Analysis of Circulating Tumor Cells: How Far Have We Come in the -Omics Era?

Tumor cells detach from the primary tumor or metastatic sites and enter the peripheral blood, often causing metastasis. These cells, named Circulating Tumor Cells (CTCs), display the same spatial and temporal heterogeneity as the primary tumor. Since CTCs are involved in tumor progression, they represent a privileged window to disclose mechanisms of metastases, while -omic analyses at the single-cell level allow dissection of the complex relationships between the tumor subpopulations and the surrounding normal tissue. However, in addition to reporting the proof of concept that we can query CTCs to reveal tumor evolution throughout the continuum of treatment for early detection of resistance to therapy, the scientific literature has also been highlighting the disadvantages of CTCs, which hampers a routine use of this approach in clinical practice. To date, an increasing number of CTC technologies, as well as -omics methods, have been employed, mostly lacking strong comparative analyses. The rarity of CTCs also represents a major challenge, because there is no consensus regarding the minimal criteria necessary and sufficient to define an event as CTC; moreover, we cannot often compare data from of one study with that of another. Finally, the availability of an individual tumor profile undermines the traditional histology-based treatment. Applying molecular data for patient benefit implies a collective effort by biologists, bioengineers, and clinicians, to create tools to interpret molecular data and manage precision medicine in every single patient. Herein, we focus on the most recent findings in CTC −omics to learn how far we have come.

Immunostimulatory plant polysaccharides impede cancer progression and metastasis by avoiding off-target effects

An unexploited homo-polysaccharide (PSM001) isolated from the seed kernel of Kottukonam variety of Mangifera indica, demonstrated selective cytotoxicity against cancer cells both in vitro and in murine models while maintaining the immunostimulatory potential. Galactoxyloglucan (PST001) isolated from the seeds of Tamarindus indica, was previously established to be an effective anticancer and immunomodulatory agent. Cancer metastasis, with key features including invasion, migration, increased angiogenesis and colony formation is only likely to accentuate in the coming decades, considering the ground realities of the modern lifestyle and environmental factors and hence both the polysaccharides were tested towards the management of malignancy. It was a startling observation with both the biopolymers in inhibiting various processes involved in the metastatic cascade. A quick perusal of the issue at hand would throw up the promising ability of both PSM001 and PST001 to inhibit lung metastatic nodules of C57BL/6 mice wherein the combinatorial treatment of these polysaccharides with vincristine delivered superior therapeutic output. Later, vascular endothelial growth factor and multiple matrix metalloproteinases were found to be the lead players in the polysaccharide mediated metastatic inhibition. Having considered the complexities associated with the chemotherapy in metastatic cancer in terms of palpable immunosuppression, the aftermaths with the co-administration of an immunostimulatory agent which itself possess unique anticancer and anti-metastatic potentials with a potent chemotherapeutic agent will be enormously consequential.

Microfluidic Isolation of Circulating Tumor Cells and Cancer Stem-Like Cells from Patients with Pancreatic Ductal Adenocarcinoma

Background: Pancreatic ductal adenocarcinoma (PDAC) requires multimodal therapeutic approaches and disease monitoring for effective treatment. Liquid biopsy biomarkers, including circulating tumor cells (CTCs) and cancer stem-like cells (CSCs), hold promise for evaluating treatment response promptly and guiding therapeutic modifications.

Methods: From 24 patients with metastatic PDAC (stage IV, M1) undergoing active systemic treatment, we collected 78 blood samples at different time points for CTC and CSC isolation using a microfluidic platform functionalized with antibodies against a CTC biomarker, epithelial cell adhesion molecule (EpCAM), or a CSC biomarker, CD133. These isolated cells were further verified, via fluorescent staining and imaging, using cytokeratin (CK), CD45, and nucleic acid stain 4',6-diamidino-2-phenylindole (DAPI).

Results: The majority (84.4%) of patient blood samples were positive for CTCs (EpCAM⁺CK⁺CD45^-DAPI⁺) and 70.8% of patient blood samples were positive for CSCs (CD133⁺CK⁺CD45^-DAPI⁺), using the highest baseline value of healthy samples as threshold. The CTC subtypes (EpCAM⁺CK⁺CD45^-DAPI⁺CD133⁺ and EpCAM⁺CK⁺CD45^-DAPI⁺CD133^-) and CSC subtypes (CD133⁺CK⁺CD45^-DAPI⁺EpCAM⁺ and CD133⁺CK⁺CD45^-DAPI⁺EpCAM^-) were also analyzed using immunochemical methods. In several cases, CSCs exhibited cytokeratin expression that did not express EpCAM, indicating that they will not be detected using EpCAM-based isolation.

Conclusion: The microfluidic platform enabled the reliable isolation of CTCs and CSCs from PDAC patient samples, as well as their subtypes. Complementary assessment of both CTCs and CSCs appears advantageous to assess the profile of tumor progressing in some cases. This research has important implications for the application and interpretation of approved methods to detect CTCs.

Immune regulation of metastasis: mechanistic insights and therapeutic opportunities

Metastatic disease is the leading cause of death in cancer patients. Metastasis formation involves a cascade of events for which the underlying mechanisms are still poorly understood. During the metastatic cascade, cancer cells tightly interact with the immune system and they influence each other, both in the tumor microenvironment and systemically. The crosstalk between cancer and immune cells adds another layer of complexity to our understanding of metastasis formation, but at the same time opens new therapeutic opportunities for cancer patients. The intensifying development of immunotherapeutic strategies calls for a better understanding of immune regulation of metastasis in order to maximize the therapeutic benefit for patients with metastatic disease. In this Review and accompanying poster, we describe the main mechanisms of immune regulation of metastasis that have been reported to date, and present promising immunotherapeutic options that are currently available, or may become so in the near future, to tackle metastasis.

The Interplay between Circulating Tumor Cells and the Immune System: From Immune Escape to Cancer Immunotherapy

Circulating tumor cells (CTCs) have aroused increasing interest not only in mechanistic studies of metastasis, but also for translational applications, such as patient monitoring, treatment choice, and treatment change due to tumor resistance. In this review, we will assess the state of the art about the study of the interactions between CTCs and the immune system. We intend to analyze the impact that the cells of the immune system have in limiting or promoting the metastatic capability of CTCs. To this purpose, we will examine studies that correlate CTCs, immune cells, and patient prognosis, and we will also discuss relevant animal models that have contributed to the understanding of the mechanisms of immune-mediated metastasis. We will then consider some studies in which CTCs seem to play a promising role in monitoring cancer patients during immunotherapy regimens. We believe that, from an accurate and profound knowledge of the interactions between CTCs and the immune system, new immunotherapeutic strategies against cancer might emerge in the future.

Circulating tumor cells (CTCs) are associated with abnormalities in peripheral blood dendritic cells in patients with inflammatory breast cancer

CTCs are involved in tumor dissemination and are an independent prognostic factor in primary and metastatic breast cancer patients. Dendritic cells (DCs) are the most efficient antigen presenting cells and are comprised of plasmacytoid-(pDC) and myeloid-(mDC) derived DC subsets. This study aimed to correlate CTC counts with the peripheral blood DC immunophenotypes and functions of inflammatory breast cancer (IBC) patients. This study included 65 IBC patients. Peripheral blood (PB) was obtained from patients prior to starting a new line of chemotherapy for CTCs enumeration by CellSearch® and DC phenotype and function by flow cytometry; the characteristics of DCs were then correlated with CTC counts and clinical outcome. Twenty-one (32.3%) patients with CTCs ≥5 had a significantly inferior overall survival (OS) compared to patients with <5 CTCs (p=0.045). In addition, patients with ≥5 CTCs had a lower percentage of mDCs capable of producing TNF-α before or after activation through the toll-like receptor (TLR), as well as a lower percentage of mDCs producing IL-12 after TLR-activation. There was a positive correlation between CTCs counts and expression of the activation (CCR7) and costimulatory (CD86) receptors on TLR-activated mDCs and pDCs, respectively. Moreover, presence of high percentage of mDC capable to produce increased levels of TNF-α was independently associated with inferior OS (p = 0.0006). An increase in the percentage of mDC producing TNF-α might induce a pro-inflammatory environment that could play a role in determining the poor clinical outcome in IBC patients and could add further prognostic value to CTCs.

[Effects of minimally invasive versus open esophagectomy on circulating tumor cells in patients with esophageal cancer]

OBJECTIVE

To investigate the effects of minimally invasive esophagectomy (MIE) and open esophagectomy (OE) on the level of circulating tumor cells (CTCs) in patients with esophageal cancer (EC).

METHODS

A total of 73 patients with EC undergoing MIE (n=38) or OE (n=35) in our department between October, 2015 and October, 2017 were enrolled, with 10 patients with benign esophagus disease and 10 healthy volunteers as controls. The levels of CTCs in the peripheral blood of the participants were detected using CanPatrol^TM technique and analyzed for their association with the operation methods and perioperative complications.

RESULTS

CTCs were detected in 60.3% (44/73) of the EC patients but in none of the control subjects. CTC level after the surgery was significantly higher than that during the surgery, and CTC level during the surgery was significantly higher than that before surgery (P<0.001). The preoperative and intra-operative CTC levels were not significantly different between MIE and OE groups (P>0.05), but the postoperative CTC level was significantly lower in MIE group than in OE group, and postoperative increment of CTC level (from the preoperative level) was significantly lower in MIE group than in OE group (P<0.001). The total incidence of postoperative complications was significantly lower in MIE group than in OE group (28.9% vs 54.3%, P=0.023), and in both groups, CTC levels in patients with complications were significantly higher than those in patients without complications (P=0.001 and P=0.005 in MIE and OE groups, respectively).

CONCLUSION

MIE may help to reduce the number of peripheral blood CTCs early after the operation, and dynamic monitoring CTCs level assists in evaluation of the prognosis of EC patients. CTC level may serve as an indicator for monitoring the prognosis of EC.

Feasibility of a novel one-stop ISET device to capture CTCs and its clinical application

INTRODUCTION

Circulating tumor cells (CTCs) play a crucial role in cancer metastasis. In this study, we introduced a novel isolation method by size of epithelial tumor cells (ISET) device with automatic isolation and staining procedure, named one-stop ISET (osISET) and validated its feasibility to capture CTCs from cancer patients. Moreover, we aim to investigate the correlation between clinicopathologic features and CTCs in colorectal cancer (CRC) in order to explore its clinical application.

RESULTS

The capture efficiency ranged from 80.3% to 88% with tumor cells spiked into medium while 67% to 78.3% with tumor cells spiked into healthy donors' blood. In detection blood samples of 72 CRC patients, CTCs and clusters of circulating tumor cells (CTC-clusters) were detected with a positive rate of 52.8% (38/72) and 18.1% (13/72) respectively. Moreover, CTC positive rate was associated with factors of lymphatic or venous invasion, tumor depth, lymph node metastasis and TNM stage in CRC patients (p < 0.01). Lymphocyte count and neutrophil to lymphocyte ratio (NLR) were significantly different between CTC positive and negative groups (p < 0.01).

MATERIALS AND METHODS

The capture efficiency of the device was tested by spiking cancer cells (MCF-7, A549, SW480, Hela) into medium or blood samples of healthy donors. Blood samples of 72 CRC patients were detected by osISET device. The clinicopathologic characteristics of 72 CRC patients were collected and the association with CTC positive rate or CTC count were analyzed.

CONCLUSIONS

Our osISET device was feasible to capture and identify CTCs and CTC-clusters from cancer patients. In addition, our device holds a potential for application in cancer management.

A circulating tumor cell cluster-based model for tumor metastasis (Hypothesis)

Metastasis is the major cause of mortality in patients with malignancies; however, the mechanisms of tumor cell dissemination and metastasis formation are obscure. Circulating tumor cells (CTCs) are believed to be a critical step for distant metastasis and are associated with a poor patient prognosis. The precise processes of metastasis formation from CTCs are vague. In the present study, we hypothesize that two CTC cluster-based mechanisms of tumor cell inoculation in ectopic organs may be viable: i) Formation of a micro-cancer embolus due to interception of CTC clusters by small vessels; and ii) formation of micrometastasis in an extravasation-dependent or -independent manner. Pathological evidence of micro-cancer emboli is critical for the verifications of this hypothesis. If proved true, this hypothesis will provide a novel perspective for cancer metastasis and has valuable clinical implications.

Circulating and disseminated tumour cells - mechanisms of immune surveillance and escape

Metastatic spread of tumour cells is the main cause of cancer-related deaths. Understanding the mechanisms of tumour-cell dissemination has, therefore, become an important focus for cancer research. In patients with cancer, disseminated cancer cells are often detectable in the peripheral blood as circulating tumour cells (CTCs) and in the bone marrow or lymph nodes as disseminated tumour cells (DTCs). The identification and characterization of CTCs and DTCs has yielded important insights into the mechanisms of metastasis, resulting in a better understanding of the molecular alterations and profiles underlying drug resistance. Given the expanding role of immunotherapies in the treatment of cancer, interactions between tumour cells and immune cells are the subject of intense research. Theoretically, cancer cells that exit the primary tumour site - leaving the protection of the typically immunosuppressive tumour microenvironment - will be more vulnerable to attack by immune effector cells; thus, the survival of tumour cells after dissemination might be the 'Achilles' heel' of metastatic progression. In this Review, we discuss findings relating to the interactions of CTCs and DTCs with the immune system, in the context of cancer immuno-editing, evasion from immune surveillance, and formation of metastases.

Circulating Tumor Cells (CTC) Are Associated with Defects in Adaptive Immunity in Patients with Inflammatory Breast Cancer

Background: Circulating tumor cells (CTCs) play a crucial role in tumor dissemination and are prognostic in primary and metastatic breast cancer. Peripheral blood (PB) immune cells contribute to an unfavorable microenvironment for CTC survival. This study aimed to correlate CTCs with the PB T-cell immunophenotypes and functions of patients with inflammatory breast cancer (IBC).

Methods: This study included 65 IBC patients treated at the MD Anderson Cancer Center. PB was obtained from patients prior to starting a new line of chemotherapy for CTCs enumeration by CellSearch^®, and T cell phenotype and function by flow cytometry; the results were correlated with CTCs and clinical outcome.

Results: At least 1 CTC (≥1) or ≥5 CTCs was detected in 61.5% or 32.3% of patients, respectively. CTC count did not correlate with total lymphocytes; however, patients with ≥1 CTC or ≥5 CTCs had lower percentages (%) of CD3+ and CD4+ T cells compared with patients with no CTCs or <5 CTCs, respectively. Patients with ≥1 CTC had a lower percentage of T-cell receptor (TCR)-activated CD8+ T cells synthesizing TNF-α and IFN-γ and a higher percentage of T-regulatory lymphocytes compared to patients without CTCs. In multivariate analysis, tumor grade and % CD3+ T-cells were associated with ≥1 CTC, whereas ≥5 CTC was associated with tumor grade, stage, % CD3+ and % CD4+ T cells, and % TCR-activated CD8 T-cells synthesizing IL-17.

Conclusions: IBC patients with CTCs in PB had abnormalities in adaptive immunity that could potentially impact tumor cell dissemination and initiation of the metastatic cascade.

Distribution and clinical significance of circulating tumor cells in nasopharyngeal carcinoma

OBJECTIVE

Nasopharyngeal carcinoma is one of the leading malignancies with obscure etiology. Circulating tumor cells have been showed to intimately correlate with characteristics in different kinds of cancer. But links between circulating tumor cells and nasopharyngeal carcinoma were still lacking. Therefore, we explored circulating tumor cells' distribution in nasopharyngeal carcinoma and their possible associations with nasopharyngeal carcinoma.

METHODS

Firstly, we found that the positive ratio of circulating tumor cells is extremely high in four stages of nasopharyngeal carcinoma. Meanwhile, positive ratios of mesenchymal circulating tumor cells were higher in early stages of nasopharyngeal carcinoma. Apart from epithelial circulating tumor cells, total, hybrid and mesenchymal circulating tumor cells were correlated with nasopharyngeal carcinoma clinical stage.

RESULTS

Our results showed that hybrid and mesenchymal circulating tumor cells were associated with nasopharyngeal carcinoma metastasis (both distant and lymph node) and smoking. Meanwhile, hybrid circulating tumor cells expressed the highest Epstein-Barr virus proteins and deoxyribonucleic acid in three types of circulating tumor cells. Moreover, we found that Epstein-Barr virus proteins viral-caspid antigen-immunoglobulin A (VCA/IgA) and early antigen-immunoglobulin A (EA/IgA), but not Epstein-Barr virus-deoxyribonucleic acid, had a closed association with nasopharyngeal carcinoma metastasis. However, Epstein-Barr virus hallmarks failed to associate with other nasopharyngeal carcinoma characteristics. Furthermore, we confirmed that matrix metalloproteinase 9 existed in circulating tumor cells and expressed most in mesenchymal circulating tumor cells. In addition, matrix metalloproteinase 9-expressed extent in hybrid circulating tumor cells is somewhat different from epithelial and mesenchymal circulating tumor cells in matrix metalloproteinase 9-positive circulating tumor cells. Nevertheless, matrix metalloproteinase 9 had no relationship with other nasopharyngeal carcinoma characteristics. Finally, our results showed that circulating tumor cells were decreased in patients after therapies.

CONCLUSION

Taken together, circulating tumor cells were tightly correlated with nasopharyngeal carcinoma characteristics. In addition, Epstein-Barr virus was associated with nasopharyngeal carcinoma metastasis. Of note, decreased circulating tumor cells indicated a favorable curative effect in nasopharyngeal carcinoma patients.

Circulating Tumor Cells: A Window Into Tumor Development and Therapeutic Effectiveness

BACKGROUND

Circulating tumor cells (CTCs) are an important diagnostic tool for understanding the metastatic process and the development of cancer.

METHODS

This review covers the background, relevance, and potential limitations of CTCs as a measurement of cancer progression and how information derived from CTCs may affect treatment efficacy. It also highlights the difficulties of characterizing these rare cells due to the limited cell surface molecules unique to CTCs and each particular type of cancer.

RESULTS

The analysis of cancer in real time, through the measure of the number of CTCs in a " liquid" biopsy specimen, gives us the ability to monitor the therapeutic efficacy of treatments and possibly the metastatic potential of a tumor.

CONCLUSIONS

Through novel and innovative techniques yielding encouraging results, including microfluidic techniques, isolating and molecularly analyzing CTCs are becoming a reality. CTCs hold promise for understanding how tumors work and potentially aiding in their demise.

The Role of CTCs as Tumor Biomarkers

Detection of Circulating Tumor Cells (CTCs) in peripheral blood can serve as a "liquid biopsy" approach and as a source of valuable tumor markers. CTCs are rare, and thus their detection, enumeration and molecular characterization are very challenging. CTCs have the unique characteristic to be non-invasively isolated from blood and used to follow patients over time, since these cells can provide significant information for better understanding tumour biology and tumour cell dissemination. CTCs molecular characterization offers the unique potential to understand better the biology of metastasis and resistance to established therapies and their analysis presents nowadays a promising field for both advanced and early stage patients. In this chapter we focus on the latest findings concerning the clinical relevance of CTC detection and enumeration, and discuss their potential as tumor biomarkers in various types of solid cancers. We also highlight the importance of performing comparison studies between these different methodologies and external quality control systems for establishing CTCs as tumor biomarkers in the routine clinical setting.

Crosstalk between CTC, Immune System and Hypoxic Tumor Microenvironment

Accumulating evidence indicate that the behavior of tumorigenic cells is highly influenced by their microenvironment. In this regard, microenvironmental hypoxia plays a determinant role in the emergence of CTC (circulating tumor cells) and CSC (cancer stem cells). CTCs are believed to be indicators of residual disease and thus pose an increased risk of metastasis. In spite of being rare and exposed to immune attack, these cells are capable to escape the immune system of the host. Although CTC play a pivotal role in the metastatic cascade and their prognostic impact has been repeatedly demonstrated, little is known about their escape mechanisms to immune system of the host. Therefore a better knowledge of the immunogenicity of these cells and their cross talk with immune killer cells as well as with tumor microenvironment may represent an exciting new immunotherapy opportunity. In this chapter, we will discuss how hypoxia is involved in the regulation of tumor progression and induction of EMT and cancer stem cell like features. We will also illustrate the relationship between hypoxia and CTC and review how CTC interact with the cells of immune system (both innate and adaptive) in terms of their survival and EMT phenotype. We will attempt to outline how hypoxic stress may confer resistance to CTC by giving them EMT and CSC like phenotype. Finally we will discuss whether the inhibition of hypoxic signaling pathways in different compartments of the solid tumor microenvironment will have an impact on CTC number, resistant phenotype and CTC lysis by immune effectors.

Gemcitabine inhibits the micrometastasis of non-small cell lung cancer by targeting the EpCAM-positive circulating tumor cells via the HGF/cMET pathway

Recurrence and metastasis are responsible for the death of non-small cell lung cancer (NSCLC) patients. Circulating tumor cells (CTCs) in the metastatic pathway have proven to be essential. This pilot study evaluated the sensitivity of gemcitabine in micrometastasis and CTCs from NSCLC patients. EpCAM-positive CTCs were detected in forty patients with NSCLC at treatment initiation and disease evaluation time-points. EpCAM-positive CTCs were defined as EpCAM-positive and CD45-negative. Total RNA was isolated from EpCAM-enriched CTCs and cytokeratin levels were detected by PCR. The HGF/cMET pathway was evaluated in CTCs from patients with different treatments and in A549 cells. The EMT-related markers were analyzed by IHC. We further explored the predictive value of baseline CTCs in patients that were receiving different treatments. The median number of CTCs in NSCLC patients was 65 CTCs/ml more than in the healthy 23?fold (median, 5.2 CTCs/ml). The mean change in cell count was significantly different for patients with gemcitabine compared to patients with non-gemcitabine treatments (-86.28 vs. -15.23/ml; P<0.05). A significant decrease was noted in the expression of cytokeratin in the CTCs of the two groups (P<0.05). The HGF/cMET pathway was inactivated in CTCs and A549 cells treated with gemcitabine, and the cell migration and invasion abilities were inhibited by gemcitabine via the HGF/cMET pathway. Furthermore, the decreased cell migration and invasion abilities may also be involved in the inhibition of the epithelial-mesenchymal transition (EMT) by gemcitabine. At a median follow-up of 36 months, the CTC count was confirmed to be a robust prognostic marker in the NSCLC population (CTCs >151, median: 15.0 months and CTCs <151, median: 32.0 months). Additionally, the survival rate in the gemcitabine group (24 months) was better than in non-gemcitabine group (21 months), suggesting a therapeutic benefit for NSCLC patient survival with the common therapy plus gemcitabine. Gemcitabine treatment decreased EpCAM-positive CTCs in NSCLC patients and inhibited EMT by the HGF/cMET pathway.

Toll-like receptor (TLR) expression of immune system cells from metastatic breast cancer patients with circulating tumor cells

The risk posed by breast cancer represents a complex interaction among factors affecting tumor immunity of the host. Toll-like receptors (TLRs) are members of the innate immune system and generally function to attract host immune cells upon activation. However, the good intentions of TLRs are sometimes not transferred to positive long-term effects, due to their involvement in exacerbating inflammatory effects and even contributing to continued inflammation. Chronic inflammatory states are considered to favor an increased predisposition to cancer, with continuous activation of inflammatory cytokines and other hallmarks of inflammation exerting a deleterious effect. Circulating tumor cells (CTCs) are neoplastic cells present in the peripheral blood circulation that have been found to be an indicator of disease progression and long-term survival. In the present study, we examined the expression of TLRs on dendritic cells, which play a major role in eliciting anti-tumor immunity, in metastatic breast cancer patients with CTCs. Flow cytometric data showed significant differences between circulating tumor cell (CTC) positive patients and CTC negative patients in their expression of TLR2 by CD8 positive cytotoxic T cells and TLR2, TLR4, TLR3, and TLR8 by CD11c positive dendritic cells (p<0.05). Expression of TLR2, TLR4, and TLR8 was increased in CTC positive patients, whereas TLR3 expression was decreased in the dendritic cell population.

Comparative analysis of innate immune system function in metastatic breast, colorectal, and prostate cancer patients with circulating tumor cells

In recent years, circulating tumor cells (CTCs) in metastatic cancer patients have been found to be a promising biomarker to predict overall survival and tumor progression in these patients. A relatively high number of CTCs has been correlated with disease progression and poorer prognosis. This study was designed to assess innate immune system function, known to be responsible for the immune defense against developing neoplasms, in metastatic cancer patients with CTCs. Our aim is to provide a link between indication of poorer prognosis, represented by the number of CTCs to the cytotoxic activity of natural killer cells, an important component of the innate immune system, and to represent a promising expanded approach to management of metastatic cancer patients with CTCs. Seventy-four patients, with metastatic breast, colorectal, or prostate cancer, were recruited for this study. Using a flow cytometric assay, we measured natural killer (NK) cell cytotoxicity against K562 target cells; and CTCs were enumerated using the CellSearch System. Toll-like receptors 2 and 4 expression was also determined by flow cytometry. We found that within each of our three metastatic cancer patient groups, NK cell cytotoxic activity was decreased in patients with a relatively high number of CTCs in peripheral blood compared to patients with a relatively low number of CTCs. In the breast and prostate cancer group, patients with CTCs greater than 5 had decreased NK cell cytotoxicity when compared to patients with less than 5 CTCs. In the colorectal cancer group, we found that 3 or more CTCs in the blood was the level at which NK cell cytotoxicity is diminished. Additionally, we found that the toll-like receptors 2 and 4 expression was decreased in intensity in all the metastatic cancer patients when compared to the healthy controls. Furthermore, within each cancer group, the expression of both toll-like receptors was decreased in the patients with relatively high number of CTCs, i.e. greater than 5 for the breast and prostate cancer group and greater than 3 for the colorectal cancer group, compared to the patients with relatively low number, i.e. less than 5 or 3, respectively. Treatment options to increase NK cell cytotoxic activity should be considered in patients with relatively high numbers of CTCs.