Invadopodia degrade ECM in the G1 phase of the cell cycle
Invadopodia are cancer cell protrusions rich in structural proteins (e.g. Tks5, cortactin) and proteases (e.g. MT1-MMP) and are responsible for degradation of the extracellular matrix (ECM). Tumor cell invasion and metastasis require cancer cells to be both proliferative and invasive, i.e. migrate through the tissue and assemble invadopodia. While several studies addressed how cell motility parameters change throughout the cell cycle, the relationship between invadopodia and cell cycle progression has not been elucidated. In this study, using invadopodia- and cell cycle- fluorescent markers, we show in 2D and 3D cell cultures, as well as in vivo, that breast carcinoma cells assemble invadopodia and invade into the surrounding ECM preferentially during the G1 phase of the cell cycle. Cells synchronized in the G0/G1 phase of the cell cycle degrade at significantly higher levels during the first 20 hours post-synchronization release. Consistent with this, mRNA and protein levels of the invadopodia key components, cortactin and MT1-MMP, peak at 14 hours post-release. Cell cycle progression is faster in cells in which invadopodia are abolished (by Tks5 knockdown), evidenced by earlier induction of cyclins A and B. A close look at the regulators of G1 revealed that the overexpression of p27kip1, but not p21cip1, causes faster turnover of invadopodia and increased ECM degradation. Furthermore, both endogenous and over-expressed p27kip1 localizes to the sites of invadopodia assembly. Taken together, these findings suggest that invadopodia function is tightly linked to cell cycle progression and is controlled by specific cell cycle regulators. Our results caution that this coordination between invasion and cell cycle must be considered when designing effective chemotherapies.