Stathmin is a protein that is crucial for the regulation of the cell cytoskeleton and the cell cycle. This role causes it to be an oncoprotein leading to uncontrolled cell proliferation when mutated and not functioning properly. If stathmin is unable to bind to tubulin, it allows for constant microtubule assembly and therefore constant mitotic spindle assembly. With no regulation of the mitotic spindle, the cell cycle is capable of cycling uncontrollably resulting in the unregulated cell growth characteristic of cancer cells.