Movie S3.

SW480 colorectal cancer cells have high constitutive plasma membrane motility visible by DIC light microscopy (left panel). Addition of 40 μM ethylisopropyl amiloride (EIPA), an inhibitor of macropinocytosis, blocked membrane motility during the first hour of treatment (middle panel). Between 1 to 2 hours, membrane motility recovered somewhat, but remained less than in untreated cells (left panel). The same group of SW480 colorectal carcinoma cells was imaged before and after addition of EIPA from 0-1 and 1-2 hours at 50 millisecond intervals.