Movie S2.

The colorectal cancer cell line SW480 has very strong constitutive endocytosis and lysosomal degradation of BSA-DQ (upper movies), while the restoration of full-length APC in SW480APC cells greatly suppressed extracellular nutrient consumption (lower movies). BSA-DQ was added to the culture medium for 15 minutes and both cultures filmed simultaneously for a further for 30 minutes. Movies of red fluorescence of degraded BSA without or with DIC brightfield are shown. The consumption of extracellular nutrients by these cancer cells must be very high, for cells were cultured in 10% serum that contains 3.5-5 mg/ml of BSA, while BSA-DQ was added in trace amounts of 5 μg/ml. These films support the view that mutation of the tumor suppressor APC causes a large increase in macropinocytosis.