Looking back, to the future of circulating tumor cells

Glucose is a key driver for GLUT1-mediated nanoparticles internalization in breast cancer cells

The mesenchymal state in cancer is usually associated with poor prognosis due to the metastatic predisposition and the hyper-activated metabolism. Exploiting cell glucose metabolism we propose a new method to detect mesenchymal-like cancer cells. We demonstrate that the uptake of glucose-coated magnetic nanoparticles (MNPs) by mesenchymal-like cells remains constant when the glucose in the medium is increased from low (5.5 mM) to high (25 mM) concentration, while the MNPs uptake by epithelial-like cells is significantly reduced. These findings reveal that the glucose-shell of MNPs plays a major role in recognition of cells with high-metabolic activity. By selectively blocking the glucose transporter 1 channels we showed its involvement in the internalization process of glucose-coated MNPs. Our results suggest that glucose-coated MNPs can be used for metabolic-based assays aimed at detecting cancer cells and that can be used to selectively target cancer cells taking advantage, for instance, of the magnetic-thermotherapy.

Evaluation of epithelial-mesenchymal transitioned circulating tumor cells in patients with resectable gastric cancer: Relevance to therapy response

AIM

To evaluate the epithelial-to-mesenchymal transition (EMT) of circulating tumor cells (CTCs) in gastric cancer patients.

METHODS

We detected tumor cells for expression of four epithelial (E(+)) transcripts (keratins 8, 18, and 19 and epithelial cell adhesion molecule) and two mesenchymal (M(+)) transcripts (Vimentin and Twist) by a quantifiable, dual-colorimetric RNA-in situ hybridization assay. Between July 2014 and October 2014, 44 patients with gastric cancer were recruited for CTC evaluation. Blood samples were obtained from selected patients during the treatment course [before surgery, after surgery and at the 6(th) cycle of XELOX based chemotherapy (about 6 mo postoperatively)].

RESULTS

We found the EMT phenomenon in which there were a few biphenotypic E(+)/M(+) cells in primary human gastric cancer specimens. Of the 44 patients, the presence of CTCs was reported in 35 (79.5%) patients at baseline. Five types of cells including from exclusively E(+) CTCs to intermediate CTCs and exclusively M(+) CTCs were identified (4 patients with M(+) CTCs and 10 patients with M(+) or M(+) > E(+) CTCs). Further, a chemotherapy patient having progressive disease showed a proportional increase of mesenchymal CTCs in the post-treatment blood specimens. We used NCI-N87 cells to analyze the linearity and sensitivity of CanPatrol(TM) system and the correlation coefficient (R(2)) was 0.999.

CONCLUSION

The findings suggest that the EMT phenomenon was both in a few cells of primary tumors and abundantly in CTCs from the blood of gastric cancer patients, which might be used to monitor therapy response.

3D Silicon Microstructures: A New Tool for Evaluating Biological Aggressiveness of Tumor Cells

In this work, silicon micromachined structures (SMS), consisting of arrays of 3- μ m-thick silicon walls separated by 50- μm-deep, 5- μ m-wide gaps, were applied to investigate the behavior of eight tumor cell lines, with different origins and biological aggressiveness, in a three-dimensional (3D) microenvironment. Several cell culture experiments were performed on 3D-SMS and cells grown on silicon were stained for fluorescence microscopy analyses. Most of the tumor cell lines recognized in the literature as highly aggressive (OVCAR-5, A375, MDA-MB-231, and RPMI-7951) exhibited a great ability to enter and colonize the narrow deep gaps of the SMS, whereas less aggressive cell lines (OVCAR-3, Capan-1, MCF7, and NCI-H2126) demonstrated less penetration capability and tended to remain on top of the SMS. Quantitative image analyses of several fluorescence microscopy fields of silicon samples were performed for automatic cell recognition and count, in order to quantify the fraction of cells inside the gaps, with respect to the total number of cells in the examined field. Our results show that higher fractions of cells in the gaps are obtained with more aggressive cell lines, thus supporting in a quantitative way the observation that the behavior of tumor cells on the 3D-SMS depends on their aggressiveness level.

Macrophage-tumor cell fusions from peripheral blood of melanoma patients

Background

While the morbidity and mortality from cancer are largely attributable to its metastatic dissemination, the integral features of the cascade are not well understood. The widely accepted hypothesis is that the primary tumor microenvironment induces the epithelial-to-mesenchymal transition in cancer cells, facilitating their escape into the bloodstream, possibly accompanied by cancer stem cells. An alternative theory for metastasis involves fusion of macrophages with tumor cells (MTFs). Here we culture and characterize apparent MTFs from blood of melanoma patients.

Methods

We isolated enriched CTC populations from peripheral blood samples from melanoma patients, and cultured them. We interrogated these cultured cells for characteristic BRAF mutations, and used confocal microscopy for immunophenotyping, motility, DNA content and chromatin texture analyses, and then conducted xenograft studies using nude mice.

Findings

Morphologically, the cultured MTFs were generally large with many pseudopod extensions and lamellipodia. Ultrastructurally, the cultured MTFs appeared to be macrophages. They were rich in mitochondria and lysosomes, as well as apparent melanosomes. The cultured MTF populations were all heterogeneous with regard to DNA content, containing aneuploid and/or high-ploidy cells, and they typically showed large sheets (and/or clumps) of cytoplasmic chromatin. This cytoplasmic DNA was found within heterogeneously-sized autophagic vacuoles, which prominently contained chromatin and micronuclei. Cultured MTFs uniformly expressed pan-macrophage markers (CD14, CD68) and macrophage markers indicative of M2 polarization (CD163, CD204, CD206). They also expressed melanocyte-specific markers (ALCAM, MLANA), epithelial biomarkers (KRT, EpCAM), as well as the pro-carcinogenic cytokine MIF along with functionally related stem cell markers (CXCR4, CD44). MTF cultures from individual patients (5 of 8) contained melanoma-specific BRAF activating mutations. Chromatin texture analysis of deconvoluted images showed condensed DNA (DAPI-intense) regions similar to focal regions described in stem cell fusions. MTFs were readily apparent in vivo in all human melanomas examined, often exhibiting even higher DNA content than the cultured MTFs. When cultured MTFs were transplanted subcutaneously in nude mice, they disseminated and produced metastatic lesions at distant sites.

Conclusions and Hypothesis

Apparent MTFs are present in peripheral blood of patients with cutaneous melanomas, and they possess the ability to form metastatic lesions when transplanted into mice. We hypothesize that these MTFs arise at the periphery of primary tumors in vivo, that they readily enter the bloodstream and invade distant tissues, secreting cytokines (such as MIF) to prepare “niches” for colonization by metastasis initiating cells.

Analytical Validation and Capabilities of the Epic CTC Platform: Enrichment-Free Circulating Tumour Cell Detection and Characterization

The Epic Platform was developed for the unbiased detection and molecular characterization of circulating tumour cells (CTCs). Here, we report assay performance data, including accuracy, linearity, specificity and intra/inter-assay precision of CTC enumeration in healthy donor (HD) blood samples spiked with varying concentrations of cancer cell line controls (CLCs). Additionally, we demonstrate clinical feasibility for CTC detection in a small cohort of metastatic castrate-resistant prostate cancer (mCRPC) patients. The Epic Platform demonstrated accuracy, linearity and sensitivity for the enumeration of all CLC concentrations tested. Furthermore, we established the precision between multiple operators and slide staining batches and assay specificity showing zero CTCs detected in 18 healthy donor samples. In a clinical feasibility study, at least one traditional CTC/mL (CK+, CD45-, and intact nuclei) was detected in 89 % of 44 mCRPC samples, whereas 100 % of samples had CTCs enumerated if additional CTC subpopulations (CK-/CD45- and CK+ apoptotic CTCs) were included in the analysis. In addition to presenting Epic Platform's performance with respect to CTC enumeration, we provide examples of its integrated downstream capabilities, including protein biomarker expression and downstream genomic analyses at single cell resolution.

Circulating Tumor Cells as Potential Biomarkers in Bladder Cancer

PURPOSE

We explored the diagnostic use of circulating tumor cells in patients with neoadjuvant bladder cancer using enumeration and next generation sequencing.

MATERIALS AND METHODS

A total of 20 patients with bladder cancer who were eligible for cisplatin based neoadjuvant chemotherapy were enrolled in an institutional review board approved study. Subjects underwent blood draws at baseline and after 1 cycle of chemotherapy. A total of 11 patients with metastatic bladder cancer and 13 healthy donors were analyzed for comparison. Samples were enriched for circulating tumor cells using the novel IsoFlux™ System microfluidic collection device. Circulating tumor cell counts were analyzed for repeatability and compared with Food and Drug Administration cleared circulating tumor cells. Circulating tumor cells were also analyzed for mutational status using next generation sequencing.

RESULTS

Median circulating tumor cell counts were 13 at baseline and 5 at followup in the neoadjuvant group, 29 in the metastatic group and 2 in the healthy group. The concordance of circulating tumor cell levels, defined as low-fewer than 10, medium-11 to 30 and high-greater than 30, across replicate tubes was 100% in 15 preparations. In matched samples the IsoFlux test showed 10 or more circulating tumor cells in 4 of 9 samples (44%) while CellSearch® showed 0 of 9 (0%). At cystectomy 4 months after baseline all 3 patients (100%) with medium/high circulating tumor cell levels at baseline and followup had unfavorable pathological stage disease (T1-T4 or N+). Next generation sequencing analysis showed somatic variant detection in 4 of 8 patients using a targeted cancer panel. All 8 cases (100%) had a medium/high circulating tumor cell level with a circulating tumor cell fraction of greater than 5% purity.

CONCLUSIONS

This study demonstrates a potential role for circulating tumor cell assays in the management of bladder cancer. The IsoFlux method of circulating tumor cell detection shows increased sensitivity compared with CellSearch. A next generation sequencing assay is presented with sufficient sensitivity to detect genomic alterations in circulating tumor cells.

Clinical implications of circulating tumor cells of breast cancer patients: role of epithelial-mesenchymal plasticity

There is increasing interest in circulating tumor cells (CTCs) due to their purported role in breast cancer metastasis, and their potential as a “liquid biopsy” tool in breast cancer diagnosis and management. There are, however, questions with regards to the reliability and consistency of CTC detection and to the relationship between CTCs and prognosis, which is limiting their clinical utility. There is increasing acceptance that the ability of CTCs to alter from an epithelial to mesenchymal phenotype plays an important role in determining the metastatic potential of these cells. This review examines the phenotypic and genetic variation, which has been reported within CTC populations. Importantly, we discuss how the detection and characterization of CTCs provides additional and often differing information from that obtained from the primary tumor, and how this may be utilized in determining prognosis and treatment options. It has been shown for example that hormone receptor status often differs between the primary tumor and CTCs, which may help to explain failure of endocrine treatment. We examine how CTC status may introduce alternative treatment options and also how they may be used to monitor treatment. Finally, we discuss the most interesting current clinical trials involving CTC analysis and note further research that is required before the breast cancer “liquid biopsy” can be realized.

Crosstalk of Oncogenic Signaling Pathways during Epithelial-Mesenchymal Transition

Epithelial–mesenchymal transition (EMT) and cell transformation have been well-documented in multiple cancer cell models and are believed to be one of the earliest events in tumor progression. Genetic and epigenetic modifications shift cells toward either end of the EMT spectrum, and can be influenced by the microenvironment surrounding a tumor. EMT and mesenchymal–epithelial transition are critical to normal function and development and an intricate network of transcription factors and transcriptional regulators tightly regulates these processes. As evidenced in normal and transformed cell lines, many signaling pathways trigger EMT during development and differentiation. The signaling pathways include those triggered by different members of the transforming growth factor superfamily, epidermal growth factor, fibroblast growth factor, hepatocyte growth factor, hypoxia-inducible factor, Wnt, Notch, and many others. Functional redundancies allow cells to undergo EMT even if these key transcriptional regulators are lacking, but these same redundancies also make these pathways particularly susceptible to gain-of-function mutations or constitutive signal activation; the “forced” transition toward either a mesenchymal or epithelial phenotype.

Current challenges for detection of circulating tumor cells and cell-free circulating nucleic acids, and their characterization in non-small cell lung carcinoma patients. What is the best blood substrate for personalized medicine?

The practice of "liquid biopsy" as a diagnostic, prognostic and theranostic tool in non-small cell lung cancer (NSCLC) patients is an appealing approach, at least in theory, since it is noninvasive and easily repeated. In particular, this approach allows patient monitoring during treatment, as well as the detection of different genomic alterations that are potentially accessible to targeted therapy or are associated with treatment resistance. However, clinical routine practice is slow to adopt the liquid biopsy. Several reasons may explain this: (I) the vast number of methods described for potential detection of circulating biomarkers, without a consensus on the ideal technical approach; (II) the multiplicity of potential biomarkers for evaluation, in particular, circulating tumor cells (CTCs) vs. circulating tumor DNA (ctDNA); (III) the difficulty in controlling the pre-analytical phase to obtain robust and reproducible results; (IV) the present cost of the currently available techniques, which limits accessibility to patients; (V) the turnaround time required to obtain results that are incompatible with the urgent need for delivery of treatment. The purpose of this review is to describe the main advances in the field of CTC and ctDNA detection in NSCLC patients and to compare the main advantages and disadvantages of these two approaches.

Circulating glioma biomarkers

Validated biomarkers for patients suffering from gliomas are urgently needed for standardizing measurements of the effects of treatment in daily clinical practice and trials. Circulating body fluids offer easily accessible sources for such markers. This review highlights various categories of tumor-associated circulating biomarkers identified in blood and cerebrospinal fluid of glioma patients, including circulating tumor cells, exosomes, nucleic acids, proteins, and oncometabolites. The validation and potential clinical utility of these biomarkers is briefly discussed. Although many candidate circulating protein biomarkers were reported, none of these have reached the required validation to be introduced for clinical practice. Recent developments in tracing circulating tumor cells and their derivatives as exosomes and circulating nuclear acids may become more successful in providing useful biomarkers. It is to be expected that current technical developments will contribute to the finding and validation of circulating biomarkers.

Detection of circulating tumor cells

The increasing number of treatment options for patients with metastatic carcinomas has created an accompanying need for methods to determine if the tumor will be responsive to the intended therapy and to monitor its effectiveness. Ideally, these methods would be noninvasive and provide quantitative real-time analysis of tumor activity in a variety of carcinomas. Assessment of circulating tumor cells shed into the blood during metastasis may satisfy this need. Here we review the CellSearch technology used for the detection of circulating tumor cells and discuss potential future directions for improvements.