Metastasis causes >90% of breast cancer-related deaths. Tumor cell structures that have been
hypothesized as necessary for metastasis are invadopodia, protrusions rich in structural proteins (e.g.
Tks5), adhesion proteins (e.g. integrin ß1) and proteases (e.g. MT1-MMP), known to degrade the
extracellular matrix (ECM) proteins.
A novel, real-time imaging methodology that allows investigation of the in vivo metastatic role of
invadopodia found that cells which assemble invadopodia move at “Slow” speeds and are seen in
perivascular niches. Outside of perivascular niches, “Fast” motile cells, which do not assemble invadopodia
were observed. This method also showed that invadopodia are essential for intravasation in vivo.
Preliminary work has begun to determine which aspects of the Slow phenotype allow invadopodia
assembly. Use of novel mathematical models, in vitro microscopy and novel computational image analysis
demonstrates that whereas the Fast cells continuously locomote, the Slow cells are in either of two
oscillating states: i. Invadopodia state, in which a cell is sessile while it degrades surrounding ECM; ii.
Locomotion state, similar to a Fast cell. The oscillation dynamics appear to depend on interactions between
the ECM and its receptor integrin ß1. Importantly, the Invadopodia, but not Locomotion state, is limited to
G1 phase of the cell cycle. Release from G1-arrest amplifies invadopodia, implying that G1-arresting
therapies may promote metastasis. This project will identify the mechanisms unique to the Invadopodia
state compared to cells that only proliferate or locomote, with the idea of targeting the Invadopodia state.
Overall Hypothesis: the Invadopodia state, which is essential for metastasis, requires a
pause in both cell locomotion and cell cycle progression. The initiation and termination of the
Invadopodia state are controlled by the interaction between the ECM, invadopodia components
integrin ß1 and Tks5, as well as the cyclin-dependent kinase inhibitor p27 (expressed during G1).
Aim 1. Determine the role of the cell cycle in regulating the Invadopodia state. Using real-time
imaging of cell cycle and invadopodia markers in vitro and in vivo, this Aim tests the hypothesis that cyclin-
dependent kinases and corresponding inhibitors regulate the Invadopodia state, but not the Locomotion.
Aim 2. Determine the role of ECM-cancer cell interactions in regulating the oscillations between
Invadopodia and Locomotion states. This Aim will provide a strategy based on in vivo modification of
integrin ß1 activity on how to turn Invadopodia state ”off” towards metastatic prevention.
Significance. Invadopodia is suggested as a new candidate target for metastatic prevention. The use of
cell cycle inhibitors in patients with invadopodia may be accelerating metastatic dissemination. The long-
term goal is to predict and prevent metastasis using invadopodia.