Microsieves for the detection of circulating tumor cells in leukapheresis product in non-small cell lung cancer patients

Background

Circulating tumor cells (CTC) in non-small cell lung cancer (NSCLC) patients are a prognostic and possible therapeutic marker, but have a low frequency of appearance. Diagnostic leukapheresis (DLA) concentrates CTC and mononuclear cells from the blood. We evaluated a protocol using two VyCAP microsieves to filter DLA product of NSCLC patients and enumerate CTC, compared with CellSearch as a gold standard.

Methods

DLA was performed in NSCLC patients before starting treatment. DLA product equaling 2×10⁸ leukocytes was diluted to 9 mL with CellSearch dilution buffer in a Transfix CTC tube. Within 72 hours the sample was filtered with a 7 µm pore microsieve and subsequently over a 5µm pore microsieve. CTC were defined as nucleated cells which stained for cytokeratin, but lacked CD45 and CD16. CellSearch detected CTC in the same volume of DLA.

Results

Of 29 patients a median of 1.4 mL DLA product (range, 0.5–4.1) was filtered (2% of total product) successfully in 93% and 45% of patients using 7 and 5 µm pores, respectively. Two DLA products were unevaluable for CTC detection. Clogging of the 5 µm but not 7 µm microsieves was positively correlated with fixation time (ρ=0.51, P<0.01). VyCAP detected CTC in 44% (12/27) of DLA products. Median CTC count per mL DLA was 0 [interquartile range (IQR): 0–1]. CellSearch detected CTC in 63% of DLA products (median =0.9 CTC per mL DLA, IQR: 0–2.1). CTC counts detected by CellSearch were significantly higher compared with VyCAP (P=0.05).

Conclusions

VyCAP microsieves can identify CTC in DLA product, but workflows need to be optimized.

A microwell array platform to print and measure biomolecules produced by single cells

Here we describe a combined method to monitor the secretion of molecules produced by single cells, followed by a method to isolate the individual cells that produced these molecules. The method is based on a self-sorting microwell chip that is connected to an activated membrane that collects the produced molecules. The produced molecules are printed by diffusion in small spots onto the membrane. The location of the printed spots can be correlated to the microwell number and the cell that produced these molecules. To demonstrate the method, we used the EpCAM antibody producing hybridoma cell line VU1D9 and a genetically engineered CHO cell-line producing Her2. VU1D9 cells produced 4.6 ± 5.6 pg (mean ± SD) of EpCAM antibody per 24 h and CHO cells 6.5 ± 8.2 pg per 24 h of Herceptin antibody.

VyCAP's puncher technology for single cell identification, isolation, and analysis

Here we present the Puncher technology for the isolation of single cells. This technology combines a silicon chip with microwells, fluorescence imaging, and a punching method to isolate and transfer the single cells to standard reaction tubes. The technology is compatible with commercially available downstream workflows and instrumentation. Here we focus on the isolation of CTC but the Puncher technology can be applied to isolate single cells from liquid biopsies and more general from cell suspensions. It is especially suited for cell suspensions that contain: Cells of interest at a frequency of 1 per 10,000 or less A low total number of cells ranging from 1 to 100,000, that are present in a volume of 0.01 to 50 mL. The frequency of appearance of CTC in blood is in the order of the 1 per 10⁶ leukocytes. To be able to isolate the single CTC with the Puncher technology, enrichment of the CTC by a 3 logs reduction of the leukocytes is required. Here we describe the use of Rosettesep and Parsortix as examples of pre-enrichment methods that are compatible with the Puncher technology and further downstream applications. © 2018 International Society for Advancement of Cytometry.

Abstract 3785: Self-sorting microwells to isolate and expand single circulating tumor cells

Introduction:

Circulating tumor cells (CTCs) can be isolated from blood and serve as a source of tumor material. Expansions of CTCs may permit functional treatment-efficacy tests in combination with genetics, epigenetics and proteomics screening. We present a fast workflow to isolate, capture, grow and image cells inside a self-sorting microwell chip using the VyCAP single cell isolation platform. After seeding single cells in a microwell chip, they can grow inside the chip or can be transferred to a tissue culture plate for clonal expansion or downstream analysis.

Materials and methods:

The Rosette-Sep™ Human CD45 depletion cocktail (Stem Cell Technologies) was used to enrich spiked cells from 1 ml of fresh EDTA blood. Cells were stained with CellTrace™ violet for tracking spiked cells, calcein for live cells, ethidium bromide for dead cells, α-CD45-PERCP as negative marker and α-EpCAM-AF647 as positive marker. After density gradient separation using Ficoll-Paque™, the cell suspension was measured and quantified using flow cytometry for Rosette-Sep™ efficiency. Cell suspensions were seeded in the self-sorting microwell chips using a negative pressure of 40-70 mbar using the VyCAP Filtration system. After seeding single cells in the microwells, the chips were imaged with the VyCAP Puncher system and either placed immediately into culture medium for cell expansion or selected cells were transferred into a 96 well tissue culture plate. Cell expansion in microwell chips and plates was followed up to 14 days.

Results:

Cultured MDA-MB-231 and MCF-7 cells were single-cell-trapped in the microwells with an efficiency of 82% ± 9% and 74% ± 15% respectively, after direct filtration without enrichment. Immediately after capturing in microwells 93% of the MCF7 cells were viable. Rosette-Sep™ enriched MDA-MB-231 and MCF-7 cells with an efficiency of 73% ± 6% and 74% ± 7% respectively, when measured with flow cytometry. The Rosette-Sep™ procedure followed by capture of the MDA-MB-231 and MCF-7 cells in the microwells resulted in an efficiency of 50% ± 11% and 52% ± 11% respectively. 92% of the cells were found back in a culture plate after punching of single cells from the chip, and of these cells, 80% were alive 4 hours after punching. 82% of these cells were alive and still growing after 14 days. In total 53% of cells spiked in blood, could be found back in the cups of which after punching into individual wells, 77% were alive and growing.

Conclusion:

We present a single cell capture and isolation method for clonal expansion of viable tumor cells. The VyCAP single cell isolation platform used for these experiments provides an easy separation of the single cells from a CTC enriched cell suspension and allows on-chip expansion as well as immediate separation of the CTCs into culture plates. About 50% of spiked cells could be retrieved inside the microwell chip and of these 77% were alive after punching into individual wells of a culture plate.

Citation Format: Joost F. Swennenhuis, Kiki C. Andree, Fikri Abali, Michiel Stevens, Joska Broekmaat, Fiona F. Passanha, Cees J. van Rijn, Leon W. Terstappen. Self-sorting microwells to isolate and expand single circulating tumor cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3785. doi:10.1158/1538-7445.AM2017-3785