CTTN and cancer: In the classical still-useful model to study invadopodia, cancer-derived cell lines or freshly isolated tumor cells from patients are plated on a 2D substratum of fluorescently labeled gelatin (denatured type I collagen) where degradative activity is concentrated in 0.5–1 μm diameter, cortactin/F-actin-rich dot-like invadopodia29 (Figure 1B).