Droplet-based single circulating tumor cell protease assay
Cancers initially arise as a local organ lesion, but can spread to distant organs by shedding individual circulating tumor cells (CTCs) into the bloodstream. This process is known as metastasis and is responsible for approximately 90% of cancer related deaths [1]. Tumor cells secrete matrix metalloproteinases (MMPs) to degrade extracellular matrix (ECM) facilitating the metastasis process. This makes MMPs become the targets of many cancer drugs and biomarker selection. However, conventional assay methods based on a large cell population are insufficiently sensitive to study MMPs because many critical biological signals of individual cells are masked by the average response from a pool of heterogeneous tumor cells
In our research, we intend to study MMP secretion activity of single circulating tumor cells using droplet microfluidic platform. The single-cell MMP functional assay is achieved by encapsulating cancer cells into picoliter droplets in oil environment together with fluorescence-based substrate [2]. MMP secreted from cancer cells cleaves the polypeptide target of the substrate and release fluorophores for observation. Therefore, we can understand the MMP activity of single cells based on the change of fluorescence intensity of cell-containing droplets. The MMP secretion profile from individual CTCs can potentially help us understand cancer progression and customize treatments of every cancer patient.
Left: Illustration of single cell encapsulation process
Right: Fluorescent image of one cell-containing droplet surrounded by several empty droplets. The fluorescent intensity of cell-containing droplet is higher than empty ones due to cell-secreted MMP.
Scale bar: 50 μm
Reference:
- Mehlen, P. and A. Puisieux, Metastasis: a question of life or death. Nat Rev Cancer, 2006. 6(6): p. 449-458.
- Jing, T., et al., Jetting microfluidics with size-sorting capability for single-cell protease detection. Biosensors and Bioelectronics, 2015. 66(0): p. 19-23.
Last updated: 16 MAY 2015
Author: Tengyang Jing