CELL-CYCLE CONTROL, GENETIC INSTABILITY A ND CANCER

During the past years the elucidation of cell cycle regulation has rev olutionized our understanding of cancer development. Many new genes ha ve been identified which promote genetic instability when mutated. The y encode cyclins, inhibitors of cyclin-dependent kinases (CDKs) or oth er cell cycle regulators. The regulation of the CDK activities in diff erent phases of the cell cycle controls the correct process of DNA syn thesis and replication. Complex signal transduction systems, so-called checkpoints, regulate growth arrest, DNA repair and programmed cell d eath(apoptosis)and thereby prevent the formation of tumour cells. An o verview is presented on the molecular mechanisms of cell cycle control and their significance for genetic stability. The functions of protoo ncogenes (e.g., c-myc) and tumour-suppressor genes (e.g, p53) in this context is described. In particular, recent advances in the understand ing of skin carcinogenesis, the role of UV radiation and cancer therap y are discussed.