[Cell cycle and cancer--from the tumor cell line to the patient]

In normal cells the cell cycle is precisely regulated by a set of different gene products. Cyclins move cells along into the cycle while cyclin-dependent kinase inhibitors function as cell cycle brakes. Mutations in such genes are frequent in cancer and may exert a profound effect on their biology. Overactive cyclins may push cells into inadequate cycling. Inactivation of cell cycle brakes might likewise provide a proliferation advantage to tumour cells over normal cells. Basic research in cell biology and molecular biology has greatly enlarged our knowledge in this timely field. The detection of gene alterations impinging on the cell cycle machinery in cancer is of increasing practical relevance. Mutated genes such as the inactivated p53 tumour suppressor gene may be prognostically relevant in human cancer, or predict the appropriate choice of treatment. Precise knowledge of cell cycle disturbances will eventually pave the way towards gene therapy of cancer although achievement of this goal is still in the distant future.