ABSTRACT
Cell cycle deregulation is one of the most frequent sources of tumor development and stems from either the overexpression of positive regulators or underexpression of negative regulators. Positive regulators consist of cyclins and cyclin-dependent kinases (CDKs), and negative regulators consist of CDK inhibitors (CDKIs). There are two families of CDKIs: the INK4 family (consisting of p16 INK4a, p15 INK4b, p18INK4c, and p19INK4d) and the CIP/KIP family (consisting of p21
, p27
,
and p57
). CDKIs are a particular focus of cancer research because they can control cell proliferation, and hence serve as rational cancer therapies. In this chapter we discuss the recently discovered molecular regulation of the CIP/KIP family members.
