A STUDY OF CANCER CELL METASTASIS USING MICROFLUIDIC TRANSMIGRATION DEVICE Y. Fu 1,3 , A. M. J. Vandongen 2 , T. Bourouina 3 , W. T. Park 4 , M. Y. Je 4 , J. M. Tsai 4 , D. L. Kwong 4 and A. Q. Liu 1 1 School of Electrical & Electronic Engineering, Nanyang Technological University, SINGAPORE 639798 2 Duke-NUS Graduate Medical School, SINGAPORE 169857 3 ESIEE, Université Paris-Est, FRANCE 93162 4 Institute of Microelectronics, A*STAR, SINGAPORE 117658 ABSTRACT Metastasis of cancer cell was studied using microfluidic device. Migration of cells in the microchannel array mimics their transmigration in tissue capillaries during in vivo metastasis. Details of the morphological changes were recorded through high resolution imaging. Results showed that the deformation of cell nucleus is critical for the transmigration of breast cancer cell MDA-MB-231. Condensation of chromatin by drug plicamycinon significantly impaired their deformation abilities and subsequently reduced the transmigration by 2 to 3 fold for microchannel smaller than 10 μm × 5 μm. As transmigration is critical for cancer metastasis, the results will be useful in designing new anti-cancer therapy. INTRODUCTION The transmigration of cancer cells across the cellular barriers are critical steps during their metastasis. For them to trespass the narrow openings on the barriers, which might be smaller than their original sizes, cancer cells need to undergo lots of physical deformations during the process. Therefore, factors affecting their stiffness and deformability are critical to their transmigration and metastasis [1-2]. The cell nucleus consists of highly condensed chromatins and organized networks of structural proteins. The compact structure grants the nucleus with high mechanical strength [3]. Hypothesis has long existed that nuclear deformation is the primary rate- limiting step during cell transmigration [4]. Cancer cells usually have disrupted chromatin arrangement and altered nuclear morphologies as compared to normal cells [5]. Biologists have argued that these changes result in the decrease of nucleus stiffness and facilitate the transmigration of cancer cells during metastasis (Fig. 1) [6-7]. Proofing these hypotheses is difficult to be achieved on conventional platform such as Boyden chamber or other membrane-based devices. They are relatively bulky and the migration events occur too far from the surface for cell imaging. And usually each chamber consists of pores of the same diameter thus study the effect of pore dimension using the same experimental conditions on a single device is impossible [8]. In recent years, many novel devices have been created for the transmigration studies using microfluidic technology [9-11]. With advantages such as precise control of microfluidic environmental parameters and high-resolution imaging, these new platforms have provided valuable insights in the transmigration studies. In this paper, the role of nuclear deformation in the transmigration of breast cancer cell MDA-MB-231 is studied using microfluidic device. After its importance is manifested, chromatin-condensing drug is applied and their effects on the prevention of cancer cells’ transmigration are studied. DESIGN AND FABRICATION OF MICROFLUIDIC DEVICE Schematic illustration of the microfluidic transmigration device is shown in Fig. 2. It consists of two chambers linked by an array of microchannels with height of 5 μm, length of 100 μm and width ranging from 6 μm to 15 μm. Cells are grown in the upper culture chamber. When chemoattractants is applied to the bottom chamber, a concentration gradient is established along the microchannels to attract the cancer cells to migrate through. This process mimics the transmigration of cancer cells in tissue capillaries during metastasis. Drugs can be applied directly to both chambers through inlets. The microfluidic device is fabricated using standard soft-lithography techniques [12-15]. A two- step photolithography method was used to in the fabrication process. First, thin layer (5 μm) of SU-8 10 photoresist (MicroChem) was spin-coated on wafer (CEE 200, Brewer Science). After soft baking, it was exposed with the first chrome mask which defined the microchannel widths (6–15 μm) followed by the post Figure 1: Chromatin condensation and cancer cell transmigration. Cancer cells have looser chromatins, which lower nucleus stiffness than normal cells, and facilitate their transmigration during metastasis. 978-1-4673-0325-5/12/$31.00 ©2012 IEEE 773 MEMS 2012, Paris, FRANCE, 29 January - 2 February 2012