Dynamics of cancer cell filopodia characterized by super-resolution bright-field optical microscopy

We explore the dynamics of cancer cell filopodia of diameters around 200 nm by using super-resolution bright-field optical microscopy. The high contrast required by the super-resolution image-restoration process is from the nanometer topographic sensitivity of non-interferometric widefield optical profilometry, rather than fluorescence labeling. Because the image-acquisition rate of this bright-field system is 20 frames/min, fast cellular dynamics can be captured and then analyzed. We successfully observe the growth and activities of the filopodia of a CL1-0 lung cancer cell. In the culturing condition, we measure that the filopodia exhibit an average elongation rate of 90 nm/sec, and an average shrinkage rate of 75 nm/sec. With the treatment of epidermal growth factor, the elongation and shrinkage rates increase to 110 nm/sec and 100 nm/sec respectively. We also find that the treatment of epidermal growth factor raises the number of filopodia by nearly a factor of 2, which implies enhancement of cell motility.