IGF1R Endocytosis in Ewing Sarcoma Figure 3. Confocal microscopy studies of IGF1R internalization after CAV1 or clathrin interference A)/inhibition B). Ewing’s sarcoma TC71 cells were treated as described in the Material and Methods section. In comparison to control conditions (see figure 1), in the interfered/ inhibited conditions IGF1R remains retained in the membrane after ligand stimulation. Scale bar represents 20 mm. Data presented is representative of 4–6 independent experiments. doi:10.1371/journal.pone.0019846.g003 on our results, we propose that in ES, after ligand binding, IGF1R is internalized under two different mechanisms: i) one dependent on clathrin and ii) the other caveolin-dependent (figure 7). However, it was predictable that IGF1R would be internalized by clathrin-dependent mechanisms, since this mechanism had already been reported for several RTKs, including IGF1R, in PLoS ONE | www.plosone.org 5 May 2011 | Volume 6 | Issue 5 | e19846