p27Kip1-stathmin interaction influences sarcoma cell migration and invasion

Emerging evidences suggest that cyclin-dependent kinase inhibitors (CKIs) can regulate cellular functions other than cell cycle progression, such as differentiation and migration. Here, we report that cytoplasmic expression of p27^kip1 affects microtubule (MT) stability following cell adhesion on extracellular matrix (ECM) constituents. This p27^kip1 activity is due to its ability to bind and impair the function of the MT-destabilizing protein stathmin. Accordingly, upregulation of p27^kip1 or downregulation of stathmin expression results in the inhibition of mesenchymal cell motility. Moreover, high stathmin and low cytoplasmic p27^kip1 expression correlate with the metastatic phenotype of human sarcomas in vivo. This study provides a functional link between proliferation and invasion of tumor cells based on diverse activities of p27^kip1 in different subcellular compartments.