The Tumor Suppressor Functions of p27 kip1 Include Control of the Mesenchymal/Amoeboid Transition

Abstract

ABSTRACT In many human cancers, p27 downregulation correlates with a worse prognosis, suggesting that p27 levels could represent an important determinant in cell transformation and cancer development. Using a mouse model system based on v- src -induced transformation, we show here that p27 absence is always linked to a more aggressive phenotype. When cultured in three-dimensional contexts, v- src -transformed p27-null fibroblasts undergo a morphological switch from an elongated to a rounded cell shape, accompanied by amoeboid-like morphology and motility. Importantly, the acquisition of the amoeboid motility is associated with a greater ability to move and colonize distant sites in vivo. The reintroduction of different p27 mutants in v- src -transformed p27-null cells demonstrates that the control of cell proliferation and motility represents two distinct functions of p27, both necessary for it to fully act as a tumor suppressor. Thus, we highlight here a new p27 function in driving cell plasticity that is associated with its C-terminal portion and does not depend on the control of cyclin-dependent kinase activity.