Abstract
Invadopodia are membrane protrusions dynamically assembled and retracted by invasive cancer cells in contact with extracellular matrix (ECM). Invadopodia are enriched for the structural proteins actin and cortactin, as well as metalloproteases such as MT1-MMP, whose function is to degrade the surrounding ECM. During metastasis, invadopodia are necessary for cancer cell intravasation and extravasation. While signaling pathways involved in the assembly and function of invadopodia are well studied, few studies address control of invadopodia dynamics and how the cell-ECM interactions contribute to cell movement. Using iterative analysis based on time-lapse microscopy and mathematical modeling of invasive cancer cell behaviors, we found that the cells oscillate between invadopodia presence and cell stasis, which we term invadopodia state and invadopodia absence during cell translocation (migration state). Our data suggests that β1-integrin-ECM binding controls the duration of each of the two states. By changing the concentration of cross-linkers in 2D and 3D cultures, we can generate ECM where 0-0.92 of total lysine residues are cross-linked. Using ECM with a range of cross-linking degrees we demonstrate that the dynamics of invadopodia-related functions have a non-linear (biphasic) relationship to ECM cross-linking. At intermediate levels of ECM cross-linking (0.39), cells exhibit rapid invadopodia protrusion-retraction cycles and rapid calcium spikes, which in turn lead to more frequent MT1-MMP delivery, causing maximal invadopodia-dependent ECM degradation. Additionally, intermediate cross-linking leads to more frequent oscillations between invadopodia and migration. In contrast, both extremely high or low levels of cross-linking lead to slower invadopodia-related dynamics and lower ECM degradation levels. Collectively, these data suggest that small physical differences in extracellular environment non-linearly translate to differences in the dynamics of cancer cell behaviors. Understanding conditions under which invadopodia can be reduced or eliminated from the tumor microenvironment by subtle environment-targeting treatments may lead to combination therapies for preventing metastatic spread.
- AFM
- Atomic Force Microscopy
- ECM
- Extracellular Matrix
- EGF
- Epidermal Growth Factor
- GTA
- Glutaraldehyde