Ebrahim Azizi

Sensitive capture of circulating tumour cells by functionalized graphene oxide nanosheets

The spread of cancer throughout the body is driven by circulating tumour cells (CTCs)1. These cells detach from the primary tumour and move from the blood stream to a new site of subsequent tumour growth. They also carry information about the primary tumour and have the potential to be valuable biomarkers for disease diagnosis and progression, and for the molecular characterization of certain biological properties of the tumour. However, the limited sensitivity and specificity of current methods to measure and study these cells in patient blood samples prevent the realization of their full clinical potential. The use of microfluidic devices is a promising method for isolating CTCs2, 3; however, the devices are reliant on three-dimensional structures, which limit further characterization and expansion of cells on the chip. Here we demonstrate an effective approach to isolate CTCs from blood samples of pancreatic, breast and lung cancer patients, by using functionalised graphene oxide nanosheets on a patterned gold surface. CTCs were captured with high sensitivity at low concentration of target cells (73% ± 32.4 at 3–5 cells/mL blood).

Tunable Thermal-Sensitive Polymer–Graphene Oxide Composite for Efficient Capture and Release of Viable Circulating Tumor Cells

A highly sensitive microfluidic system to capture circulating tumor cells from whole blood of cancer patients is presented. The device incorporates graphene oxide into a thermoresponsive polymer film to serve as the first step of an antibody functionalization chemistry. By decreasing the temperature, captured cells may be released for subsequent analysis.

Breast cancer stem cells: current advances and clinical implications.

There is substantial evidence that many cancers, including breast cancer, are driven by a population of cells that display stem cell properties. These cells, termed cancer stem cells (CSCs) or tumor initiating cells, not only drive tumor initiation and growth but also mediate tumor metastasis and therapeutic resistance. In this chapter, we summarize current advances in CSC research with a major focus on breast CSCs (BCSCs). We review the prevailing methods to isolate and characterize BCSCs and recent evidence documenting their cellular origins and phenotypic plasticity that enables them to transition between mesenchymal and epithelial-like states. We describe in vitro and clinical evidence that these cells mediate metastasis and treatment resistance in breast cancer, the development of novel strategies to isolate circulating tumor cells (CTCs) that contain CSCs and the use of patient-derived xenograft (PDX) models in preclinical breast cancer research. Lastly, we highlight several signaling pathways that regulate BCSC self-renewal and describe clinical implications of targeting these cells for breast cancer treatment. The development of strategies to effectively target BCSCs has the potential to significantly improve the outcomes for patients with breast cancer.

Point: Cancer Stem Cells—The Evidence Accumulates

The concept that cancers arise from “embryonic rests” and contain cell populations capable of self-renewal was proposed >100 years ago (1). Only within the past decade, however, has the accumulating research provided strong support for the cancer stem cell (CSC)2 hypothesis. This hypothesis posits that cancers arise in self-renewing cell populations and that the resulting cancers, like their normal organ counterparts, are composed of hierarchically organized cell populations. Self-renewing “cancer stem cells” maintain tumor growth and generate the diverse populations constituting the tumor bulk. The CSC hypothesis has tremendously important clinical implications.nnDespite the accelerating research in the CSC field, several aspects of CSC biology remain controversial. Despite these controversies, we argue that the preponderance of the evidence now suggests that many, if not most, human cancers follow a CSC model. Below we discuss 10 important areas that, despite controversy, provide support for a CSC model.nnA variety of markers and assays have been developed for isolating and characterizing CSCs. Interestingly, many of these markers, such as CD44, CD133, and aldehyde dehydrogenase, also are expressed in normal stem cells. Although these markers have been useful for CSC research, it is clear that the expression of these markers is highly dependent on the in vitro conditions (2) and does not always correlate with the results of functional assays. Therefore, most would agree that defining a CSC requires demonstrating that these cells are able to self-renew in vivo. It is important to acknowledge that all mouse models have limitations. Demonstration of self-renewal of human CSCs has generally involved the use of immunosuppressed mouse models. Studies of melanoma that demonstrated that tumor-initiating capacity is highly dependent on the degree of mouse immunosuppression have raised questions regarding the validity of such models (3); however, tumor-initiating cells have been prospectively isolated from mouse transgenic …

Ultra-Specific Isolation of Circulating Tumor Cells Enables Rare-Cell RNA Profiling

The clinical potential of circulating tumor cells (CTCs) in managing cancer metastasis is significant. However, low CTC isolation purities from patient blood have hindered sensitive molecular assays of these rare cells. Described herein is the ultra‐pure isolation of CTCs from patient blood samples and how this platform has enabled highly specific molecular (mRNA and miRNA) profiling of patient CTCs.

High-Throughput Microfluidic Labyrinth for the Label-free Isolation of Circulating Tumor Cells

We present Labyrinth, a label-free microfluidic device to isolate circulating tumor cells (CTCs) using the combination of long loops and sharp corners to focus both CTCs and white blood cells (WBCs) at a high throughput of 2.5xa0mL/min. The high yield (>90%) and purity (600 WBCs/mL) of Labyrinth enabled us to profile gene expression in CTCs. As proof of principle, we used previously established cancer stem cell gene signatures to profile single cells isolated from the blood of breast cancer patients. We observed heterogeneous subpopulations of CTCs expressing genes for stem cells, epithelial cells, mesenchymal cells, and cells transitioning between epithelial and mesenchymal. Labyrinth offers a cell-surface marker-independent single-cellxa0isolation platform to study heterogeneous CTC subpopulations.

Poor Prognosis Indicated by Venous Circulating Tumor Cell Clusters in Early-Stage Lung Cancers

Early detection of metastasis can be aided by circulating tumor cells (CTC), which also show potential to predict early relapse. Because of the limited CTC numbers in peripheral blood in early stages, we investigated CTCs in pulmonary vein blood accessed during surgical resection of tumors. Pulmonary vein (PV) and peripheral vein (Pe) blood specimens from patients with lung cancer were drawn during the perioperative period and assessed for CTC burden using a microfluidic device. From 108 blood samples analyzed from 36 patients, PV had significantly higher number of CTCs compared with preoperative Pe (P < 0.0001) and intraoperative Pe (P < 0.001) blood. CTC clusters with large number of CTCs were observed in 50% of patients, with PV often revealing larger clusters. Long-term surveillance indicated that presence of clusters in preoperative Pe blood predicted a trend toward poor prognosis. Gene expression analysis by RT-qPCR revealed enrichment of p53 signaling and extracellular matrix involvement in PV and Pe samples. Ki67 expression was detected in 62.5% of PV samples and 59.2% of Pe samples, with the majority (72.7%) of patients positive for Ki67 expression in PV having single CTCs as opposed to clusters. Gene ontology analysis revealed enrichment of cell migration and immune-related pathways in CTC clusters, suggesting survival advantage of clusters in circulation. Clusters display characteristics of therapeutic resistance, indicating the aggressive nature of these cells. Thus, CTCs isolated from early stages of lung cancer are predictive of poor prognosis and can be interrogated to determine biomarkers predictive of recurrence. Cancer Res; 77(18); 5194-206. ©2017 AACR.

Heterogeneity of Human Breast Stem and Progenitor Cells as Revealed by Transcriptional Profiling

Summary During development, the mammary gland undergoes extensive remodeling driven by stem cells. Breast cancers are also hierarchically organized and driven by cancer stem cells characterized by CD44+CD24low/− or aldehyde dehydrogenase (ALDH) expression. These markers identify mesenchymal and epithelial populations both capable of tumor initiation. Less is known about these populations in non-cancerous mammary glands. From RNA sequencing, ALDH+ and ALDH−CD44+CD24− human mammary cells have epithelial-like and mesenchymal-like characteristics, respectively, with some co-expressing ALDH+ and CD44+CD24− by flow cytometry. At the single-cell level, these cells have the greatest mammosphere-forming capacity and express high levels of stemness and epithelial-to-mesenchymal transition-associated genes including ID1, SOX2, TWIST1, and ZEB2. We further identify single ALDH+ cells with a hybrid epithelial/mesenchymal phenotype that express genes associated with aggressive triple-negative breast cancers. These results highlight single-cell analyses to characterize tissue heterogeneity, even in marker-enriched populations, and identify genes and pathways that define this heterogeneity.

Cancer Stem Cells and Circulating Tumor Cells: Molecular Markers, Isolation Techniques, and Clinical Implications

There is now a considerable body of evidence that many cancers are hierarchically organized and driven by a cellular component termed “cancer stem cells” (CSCs). These cells have the ability to self-renew and to generate heterogeneous populations that constitute the tumor bulk. Preclinical studies have demonstrated that CSCs mediate tumor metastasis and resistance to chemotherapy and radiation therapy. CSC biomarkers have been identified and both in vitro and mouse models have been developed to facilitate the isolation of these cells as well as the elucidation of CSC regulatory pathways. Agents targeting CSCs have now entered early phase clinical trials. The development of these clinical trials highlights the important need to develop technologies to monitor CSCs in patients. Unlike hematologic malignancies, where tumor specimens are readily obtainable, in solid tumors obtaining serial biopsies to assess CSCs is difficult. Studies suggest that circulating tumor cells (CTCs) contain a highly enriched proportion of CSCs and thus monitoring these cells in blood may provide a liquid biopsy for CSC assessment in solid tumors. In parallel with developments of efficient CTC isolation technologies, assays to molecularly characterize these cells at single cell resolution are also being developed. In this chapter we will review the current status of CSC therapeutic technologies as well as microfluidic techniques for isolation and molecular characterization of CTCs in cancer patients. If CSCs are responsible for tumor metastasis, resistance, and recurrence, development of effective CSC therapies has the potential to significantly improve the efficacy of cancer treatments.

The Promise of Single Cell Omics for Onco-therapy

Despite extensive research effort and considerable progress, the “war on cancer” that president Nixon declared in 1971 has yet to be optimally integrated into cancer therapeutics and as such cancer remains a major medical challenge for oncologists. The dynamic and complex biology of tumor cells undergoing clonal evolution generates cells with diverse degrees of drug resistance and metastatic potential. This highlights the need to be able to access this clonal density in order to develop effective therapeutics. With this prospective, early phase single cell studies are vital for thoroughly interrogating tumor heterogeneity to uncover more about cancer cell biology and to explore new therapeutic targets leading to more successful treatments. Current evidence supports the notion that clonogenic cells within the tumor mass may potentially give rise to a population of cells with unique genomic, transcriptomic and proteomic features distinct from the rest of the tumor mass. This observation can explain drug resistance after an initial period of primary tumor response. Therefore, completely abrogating or at a minimum achieving long-term, durable control over cancer requires researchers and oncologists to employ a personalized medicine approach that includes both tumor and patient-associated variables to modify current therapeutic regimens. In this review we discuss the importance of omics and in particular single cell genomics which are increasingly promising given recently developed technology advancements to facilitate exploration of cellular heterogeneity and tumor complexity.