Lipid tethering of breast tumor cells enables real-time imaging of free-floating cell dynamics and drug response
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Kristi R. Chakrabarti1,2,3,*, James I. Andorko4,*, Rebecca A. Whipple3,5, Peipei Zhang4, Elisabeth L. Sooklal4, Stuart S. Martin2,3,5, Christopher M. Jewell3,4,6
1Medical Scientist Training Program, University of Maryland School of Medicine, Baltimore, MD 21201, USA
2Graduate Program in Molecular Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA
3Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, MD 21201, USA
4Fischell Department of Bioengineering, University of Maryland, College Park, MD 20742, USA
5Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
6Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
*These authors have contributed equally to this work
Keywords: circulating tumor cells, microtentacles, breast cancer, microfluidics, polyelectrolyte multilayers
Received: December 20, 2015 Accepted: January 26, 2016 Published: February 08, 2016
Free-floating tumor cells located in the blood of cancer patients, known as circulating tumor cells (CTCs), have become key targets for studying metastasis. However, effective strategies to study the free-floating behavior of tumor cells in vitro have been a major barrier limiting the understanding of the functional properties of CTCs. Upon extracellular-matrix (ECM) detachment, breast tumor cells form tubulin-based protrusions known as microtentacles (McTNs) that play a role in the aggregation and re-attachment of tumor cells to increase their metastatic efficiency. In this study, we have designed a strategy to spatially immobilize ECM-detached tumor cells while maintaining their free-floating character. We use polyelectrolyte multilayers deposited on microfluidic substrates to prevent tumor cell adhesion and the addition of lipid moieties to tether tumor cells to these surfaces through interactions with the cell membranes. This coating remains optically clear, allowing capture of high-resolution images and videos of McTNs on viable free-floating cells. In addition, we show that tethering allows for the real-time analysis of McTN dynamics on individual tumor cells and in response to tubulin-targeting drugs. The ability to image detached tumor cells can vastly enhance our understanding of CTCs under conditions that better recapitulate the microenvironments they encounter during metastasis.
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