The cell cycle and cancer

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Abstract
Recent insights in the fields of cell cycle regulation and cancer would each alone have provided prime examples of research at the “Frontiers of Science.” However, some of the most revealing information about both topics has derived from the intersection of the two fields. The intent of this summary is to introduce the basics of the cell cycle, cancer, and their overlap, and then to describe the research from two laboratories that was presented in the session. A more comprehensive treatment of these subjects, beyond this description for a general audience, is contained in several reviews (1–5). The process of replicating DNA and dividing a cell can be described as a series of coordinated events that compose a “cell division cycle,” illustrated for mammalian cells in Fig. 1 (see legend for details). At least two types of cell cycle control mechanisms are recognized: a cascade of protein phosphorylations that relay a cell from one stage to the next and a set of checkpoints that monitor completion of critical events and delay progression to the next stage if necessary. The first type of control involves a highly regulated kinase family (2). Kinase activation generally requires association with a second subunit that is transiently expressed at the appropriate period of the cell cycle; the periodic “cyclin” subunit associates with its partner “cyclin-dependent kinase” (CDK) to create an active complex with unique substrate specificity. Regulatory phosphorylation and dephosphorylation fine-tune the activity of CDK–cyclin complexes, ensuring well-delineated transitions between cell cycle stages. In the future, additional molecular definition of the cell cycle may lead to a more intricate progression than indicated in Fig. 1. A schematic representation of the mammalian cell cycle. In each cell division cycle, chromosomes are replicated once (DNA synthesis or S-phase) and segregated to create two …