Cell Cycle and Cancer

With the emergence of new technologies, our understanding of the cell cycle and its regulation continues to grow exponentially. We now have an appreciation of the pathways and circuits that govern the normal cell-cycle progression and the cellular checkpoint responses to DNA damage and other forms of stress. In addition, the deciphering of the biochemical and genetic pathways that maintain the integrity of cell-cycle progression and cell division provides the foundation for understanding how mutations that impair these pathways can compromise cell-cycle control and lead to genomic instability and cancer. Despite the enormous complexity of these pathways, various components of the cell-cycle circuitry are beginning to prove clinically valuable as diagnostic or prognostic markers, while others are emerging as promising therapeutic anticancer targets. The pathways that lead to programmed cell death, apoptosis, are mediated by many of the same molecular players that participate in cell-cycle control and are also providing therapeutic targets for cancer. The basic strategies are to find compounds that arrest tumor cells so that they will not contribute to the growth of the tumor or to push the tumor cells into apoptosis to rid the lesion of tumor cells. Most of the proteins that have been discussed in this chapter are currently considered to be potential therapeutic targets and are under active investigation in many academic laboratories and pharmaceutical companies. Tumor cells, however, have evolved to escape most antitumor therapies, indicating that most new therapeutic approaches will have to involve combination therapies rather than a single therapeutic strategy. Nevertheless, as the cell cycle and apoptotic pathways are more thoroughly dissected, there is hope that in the near future many cancers for which we currently have no effective treatments will become manageable with concomitant improvement in quality of life.