Steven M. Santana

Functional characterization of circulating tumor cells with a prostate-cancer-specific microfluidic device.

Cancer metastasis accounts for the majority of cancer-related deaths owing to poor response to anticancer therapies. Molecular understanding of metastasis-associated drug resistance remains elusive due to the scarcity of available tumor tissue. Isolation of circulating tumor cells (CTCs) from the peripheral blood of patients has emerged as a valid alternative source of tumor tissue that can be subjected to molecular characterization. However, issues with low purity and sensitivity have impeded adoption to clinical practice. Here we report a novel method to capture and molecularly characterize CTCs isolated from castrate-resistant prostate cancer patients (CRPC) receiving taxane chemotherapy. We have developed a geometrically enhanced differential immunocapture (GEDI) microfluidic device that combines an anti-prostate specific membrane antigen (PSMA) antibody with a 3D geometry that captures CTCs while minimizing nonspecific leukocyte adhesion. Enumeration of GEDI-captured CTCs (defined as intact, nucleated PSMA+/CD45− cells) revealed a median of 54 cells per ml identified in CRPC patients versus 3 in healthy donors. Direct comparison with the commercially available CellSearch® revealed a 2–400 fold higher sensitivity achieved with the GEDI device. Confocal microscopy of patient-derived GEDI-captured CTCs identified the TMPRSS2:ERG fusion protein, while sequencing identified specific androgen receptor point mutation (T868A) in blood samples spiked with only 50 PC C4-2 cells. On-chip treatment of patient-derived CTCs with docetaxel and paclitaxel allowed monitoring of drug-target engagement by means of microtubule bundling. CTCs isolated from docetaxel-resistant CRPC patients did not show any evidence of drug activity. These measurements constitute the first functional assays of drug-target engagement in living circulating tumor cells and therefore have the potential to enable longitudinal monitoring of target response and inform the development of new anticancer agents.

Detection of Circulating Pancreas Epithelial Cells in Patients With Pancreatic Cystic Lesions

Hematogenous dissemination is thought to be a late event in cancer progression. We recently showed in a genetic model of pancreatic ductal adenocarcinoma that pancreas cells can be detected in the bloodstream before tumor formation. To confirm these findings in humans, we used microfluidic geometrically enhanced differential immunocapture to detect circulating pancreas epithelial cells in patient blood samples. We captured more than 3 circulating pancreas epithelial cells/mL in 7 of 21 (33%) patients with cystic lesions and no clinical diagnosis of cancer (Sendai criteria negative), 8 of 11 (73%) with pancreatic ductal adenocarcinoma, and in 0 of 19 patients without cysts or cancer (controls). These findings indicate that cancer cells are present in the circulation of patients before tumors are detected, which might be used in risk assessment.

Microfluidic isolation of cancer-cell-derived microvesicles from hetergeneous extracellular shed vesicle populations

Extracellular shed vesicles, including exosomes and microvesicles, are disseminated throughout the body and represent an important conduit of cell communication. Cancer-cell-derived microvesicles have potential as a cancer biomarker as they help shape the tumor microenvironment to promote the growth of the primary tumor and prime the metastatic niche. It is likely that, in cancer cell cultures, the two constituent extracellular shed vesicle subpopulations, observed in dynamic light scattering, represent an exosome population and a cancer-cell-specific microvesicle population and that extracellular shed vesicle size provides information about provenance and cargo. We have designed and implemented a novel microfluidic technology that separates microvesicles, as a function of diameter, from heterogeneous populations of cancer-cell-derived extracellular shed vesicles. We measured cargo carried by the microvesicle subpopulation processed through this microfluidic platform. Such analyses could enable future investigations to more accurately and reliably determine provenance, functional activity, and mechanisms of transformation in cancer.

Immunocapture of prostate cancer cells by use of anti-PSMA antibodies in microdevices

Patients suffering from cancer can shed tumor cells into the bloodstream, leading to one of the most important mechanisms of metastasis. As such, the capture of these cells is of great interest. Circulating tumor cells are typically extracted from circulation through positive selection with the epithelial cell-adhesion molecule (EpCAM), leading to currently unknown biases when cells are undergoing epithelial-to-mesenchymal transition. For prostate cancer, prostate-specific membrane antigen (PSMA) presents a compelling target for immunocapture, as PSMA levels increase in higher-grade cancers and metastatic disease and are specific to the prostate epithelium. This study uses monoclonal antibodies J591 and J415—antibodies that are highly specific for intact extracellular domains of PSMA on live cells—in microfluidic devices for the capture of LNCaPs, a PSMA-expressing immortalized prostate cancer cell line, over a range of concentrations and shear stresses relevant to immunocapture. Our results show that J591 outperforms J415 and a mix of the two for prostate cancer capture, and that capture performance saturates following incubation with antibody concentrations of 10 micrograms per milliliter.

Microfluidic Transport in Microdevices for Rare Cell Capture

The isolation and capture of rare cells is a problem uniquely suited to microfluidic devices, in which geometries on the cellular length scale can be engineered and a wide range of chemical functionalizations can be implemented. The performance of such devices is primarily affected by the chemical interaction between the cell and the capture surface and the mechanics of cell‐surface collision and adhesion. As rare cell‐capture technology has been summarized elsewhere (E. D. Pratt et al., Chem. Eng. Sci. 2011, 66, 1508–1522), this article focuses on the fundamental adhesion and transport mechanisms in rare cell‐capture microdevices, and explores modern device design strategies in a transport context. The biorheology and engineering parameters of cell adhesion are defined; adhesion models and reaction kinetics briefly reviewed. Transport at the microscale, including diffusion and steric interactions that result in cell motion across streamlines, is discussed. The review concludes by discussing design strategies with a focus on leveraging the underlying transport phenomena to maximize device performance.

Cancerous Epithelial Cell Lines Shed Extracellular Vesicles With a Bimodal Size Distribution that is Sensitive to Glutamine Inhibition

Extracellular shed vesicles (ESVs) facilitate a unique mode of cell-cell communication wherein vesicle uptake can induce a change in the recipient cells state. Despite the intensity of ESV research, currently reported data represent the bulk characterization of concentrated vesicle samples with little attention paid to heterogeneity. ESV populations likely represent diversity in mechanisms of formation, cargo and size. To better understand ESV subpopulations and the signaling cascades implicated in their formation, we characterize ESV size distributions to identify subpopulations in normal and cancerous epithelial cells. We have discovered that cancer cells exhibit bimodal ESV distributions, one small-diameter and another large-diameter population, suggesting that two mechanisms may govern ESV formation, an exosome population and a cancer-specific microvesicle population. Altered glutamine metabolism in cancer is thought to fuel cancer growth but may also support metastatic niche formation through microvesicle production. We describe the role of a glutaminase inhibitor, compound 968, in ESV production. We have discovered that inhibiting glutamine metabolism significantly impairs large-diameter microvesicle production in cancer cells.

Characterization of a hybrid dielectrophoresis and immunocapture microfluidic system for cancer cell capture

The capture of circulating tumor cells (CTCs) from cancer patient blood enables early clinical assessment as well as genetic and pharmacological evaluation of cancer and metastasis. Although there have been many microfluidic immunocapture and electrokinetic techniques developed for isolating rare cancer cells, these techniques are often limited by a capture performance tradeoff between high efficiency and high purity. We present the characterization of shear‐dependent cancer cell capture in a novel hybrid DEP–immunocapture system consisting of interdigitated electrodes fabricated in a Hele‐Shaw flow cell that was functionalized with a monoclonal antibody, J591, which is highly specific to prostate‐specific membrane antigen expressing prostate cancer cells. We measured the positive and negative DEP response of a prostate cancer cell line, LNCaP, as a function of applied electric field frequency, and showed that DEP can control capture performance by promoting or preventing cell interactions with immunocapture surfaces, depending on the sign and magnitude of the applied DEP force, as well as on the local shear stress experienced by cells flowing in the device. This work demonstrates that DEP and immunocapture techniques can work synergistically to improve cell capture performance, and it will aid in the design of future hybrid DEP–immunocapture systems for high‐efficiency CTC capture with enhanced purity.

Immunocapture of prostate cancer cells with anti-PSMA antibodies in microdevices

This document reports the performance of anti-PSMA monoclonal antibodies in microfludic devices for the isolation of circulating prostate cancer cells.

Abstract 4891: Molecular and functional analysis of circulating tumor cells in castrate resistant prostate cancer using a geometrically enhanced microfluidic device based on PSMA immunocapture

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Prostate cancer (PC) is the most common type of cancer in males and the second leading cause of male cancer deaths in the United States. Circulating tumor cells (CTCs) are commonly found in the blood of metastatic patients and the capture of these cells is important in the study of disease progression. We have developed a geometrically enhanced differential immunocapture (GEDI) microfluidic device coated with the prostate-specific membrane antigen (PSMA) which captures prostate CTCs with high purity and efficiency. This device is designed with a staggered obstacle array in order to maximize the capture efficiency (>80%) and purity (70%) of CTCs. We have used this device to capture, enumerate and molecularly characterize CTCs isolated from 1 ml of blood from patients with castrate resistant prostate cancer (CRPC). First, we compared the capture efficiency from 16 CRPC patients’ blood and subjected it to CTC enumeration by either the GEDI device or the FDA approved CellSearch technology (EpCAM-based immunocapture). Our results showed a 2-350 fold enrichment in CTC counts by the GEDI (range 15-1200 CTCs/ml, median 54). In addition, there was minimal false positive CTC detection in healthy donor blood analyzed by the GEDI. Next we sought to characterize the captured CTCs using multiplex immunofluorescence for proteins specific for PC like androgen receptor (AR), PSMA, TMPRSS2-ERG, EpCAM and other markers involved in epithelial to mesenchymal transition (EMT). We observed low or lack of EpCAM expression in the captured PSMA+/CD45- CTCs, concomitant with high vimentin expression, suggesting that our device may be preferentially capturing CTCs that have undergone EMT. Using the GEDI device, we are able to detect a known single point mutation in the AR using cDNA extracted from approximately 50 C4-2 cells spiked into 1 ml of blood from a healthy donor. Importantly, we have captured CTCs from different CRPC patients and treated them ex vivo with docetaxel to assess effective drug-target engagement by determining the extent of microtubule (MT) stabilization and apoptotic cell death. Our results showed non-uniform CTC response to drug treatment, such that a subset of PSMA+/CD45- CTCs showed MT bundling, indicating tumor heterogeneity and further suggesting that we can potentially use this device to predict patient response to taxane-based chemotherapy. In summary, the GEDI microfluidic device is a novel and specific technology to isolate and characterize PC CTCs at the molecular level. We plan to use this device in prospective clinical studies in order to understand the molecular basis of disease progression and response to taxane-based chemotherapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4891. doi:10.1158/1538-7445.AM2011-4891