A QUESTION OF BALANCE - THE ROLE OF CYCLIN-KINASE INHIBITORS IN DEVELOPMENT AND TUMORIGENESIS

Cyclin-kinase inhibitors (CKIs) are versatile negative regulators of c ell proliferation that function in developmental decisions, checkpoint control and tumour suppression. Phenotypic examination of mice lackin g individual CKIs has begun to reveal the specialized roles that each of these proteins play in vivo. This review focuses on what has been l earned about the role of CKIs in development and cancer through the ge neration of knockout animals. The authors discuss whether differences in knockout phenotypes between CKIs reflect differential use of these inhibitors by tile organism or a fundamental difference between the in hibitors, and suggest a balance hypothesis to explain the different ef fects observed.