Figure 5: Influence of collagen density on invadopodia formation in MDA-MB-231 cells. MDA-MB-231 cells were cultured on collagen-coated substrates for 24 hours and then fixed. (A) Cells were stained with F-actin (red) and cortactin (green). Invadopodia formation was probed by imaging cells at high magnification (40x) and checking for co-localization of actin and cortactin (white arrows). Scale bar=50 μm. (B) Quantification of the number of co-localized actin-cortactin puncta per cell revealed an increase in the number of invadopodia on higher density surfaces. Bars indicate statistical significance (*p < 0.01).