Metastasis is the cumulative result of multiple changes in tumor cells and their microenvironment that enables cellular migration and invasion into healthy host tissue. Cell migration assays enable quantitative characterisation of cells movements, adhesion, and invasion and how these are influenced by pharmacological agents. We use different techniques to study these phenomena, from endpoint assays to time-lapse microscopy approaches and complex analysis for the downstream interpretation of the cell migratory behavior.
Wound healing assay
The wound-healing assay is a simple and inexpensive method to study directional cell migration in vitro. The basic step involves creating a “wound” in a cell monolayer manually or utilizing special microplates that provide a uniform and reproducible cell-free zone (i.e. Oris™ Pro). Cells are then imaged at the beginning and at regular intervals during cell migration. It is particularly suitable for studies on the effects of cell-matrix and cell-cell interactions on cell migration. This assay is convenient and versatile and can be applied for a high throughput screen platform.
| Wound healing assay, Oris™ Pro | |
| Detection method | Brightfield, Fluorescence |
| Platform | Microscope |
| Throughput | Medium |
| Multiplexing | No |
| Measurement type | Real-time |
| Model system | Adherent 2D cell cultures |
Transwell cell migration/invasion assay
The most widely accepted cell migration technique is the Boyden Chamber assay. The classic transwell migration assay system uses a hollow plastic chamber, sealed at one end with a porous membrane. This chamber is suspended over a larger well that contains medium and/or chemoattractants. Cells are placed inside the chamber and allowed to migrate through the pores, to the other side of the membrane. To analyze cell invasion, the transwell insert membrane is coated with basement membrane ECM protein or a layer of cells such as endothelial cells. Migratory cells are then stained and directly counted in the microscope or some other indirect readout methods are used (e.g. metabolic activity assay).
| Boyden Chamber (transwell), ECMatrix™ | |
| Detection method | Fluorescence, Absorbance, Luminescence |
| Platform | Plate reader, microscope |
| Throughput | Medium |
| Multiplexing | Yes |
| Measurement type | Endpoint |
| Model system | Adherent and suspension 2D cell cultures |
Microfluidic migration device chemotaxis assay
The alternative for the transwell system are microfluidic migration devices which promote a stable diffusion-generated concentration gradient. Slides are made from plastic with high optical qualities similar to those of glass allowing for life-microscopy assays. At specific time intervals, images of the observation area can be acquired, allowing real-time monitoring and quantitative measurements of cell migration.
| µ-Slide Chemotaxis, Millicell® µ-Migration Assay | |
| Detection method | Fluorescence, Absorbance, Luminescence, Brightfield |
| Platform | Microscope, Plate reader |
| Throughput | Low |
| Multiplexing | No |
| Measurement type | Real-time |
| Model system | Adherent and suspension 2D cell cultures |