Fig. 9. Quantification of CTX-FITC internalization in HeLa and CaCo-2 cells after incubation with GM1. CTX-FITC internalization to the GM130-positive Golgi (CTX-GM130 overlay; left panels) or to TfR-positive endosomes (CTX-TfR overlay; right panels) was quantified using a mask overlay assay in HeLa (A) and CaCo-2 (B) cells grown either in regular medium (GM–; speckled bars) or in the presence of 5 mM GM1 for 4 hours followed by a 4-hour chase in regular medium (GM+) and left untreated (black bars) or treated with mßCD (white bars) or genistein (grey bars), as indicated. Data for cells grown in regular medium (GM–) was taken from Fig. 5 for both the mßCD and genistein series of experiments. The increase in CTX uptake to the Golgi in GM1-supplemented HeLa and CaCo-2 cells and its inhibition by mßCD and genistein is significant as is the increased delivery of CTX to endosomes in mßCD treated CaCo-2 cells (^*P<0.01; ^**P<0.05 relative to bar to the left).