Short and long-term tumor cell responses to Aurora kinase inhibitors.
ABSTRACT Aurora kinases are essential for mitosis and are candidate targets of novel chemotherapeutic agents. The inhibitors ZM447439, MK-0457 (VX-680) as well as Hesperadin have been used to dissect the roles of Aurora kinases in the cell cycle and have been tested clinically for the treatment of cancer. Here we have carried out a detailed kinetic analysis of two isogenic cell lines differing in p53 function and have compared the effects of ZM447439 and VE-465 (related to MK-0457). We find that p53 is needed for efficient cell cycle arrest when Aurora kinases are inhibited by either ZM447439 or VE-465. However, the p53-induced cell cycle block is neither immediate nor absolute. ZM447439 induced the localized accumulation of gammaH2A.X indicating that p53 induction by this drug occurs in response to DNA damage. Our analysis of the long-term effects of ZM447439 indicates that cells can evade killing by the drug, but not via a classical drug-resistance mechanism. Several mechanisms to explain how cells may evade killing by Aurora kinase inhibitors are described.
Chapter: The p53 Network[show abstract] [hide abstract]
ABSTRACT: Cancer arises through a series of mutations in selected oncogenes, tumor suppressor genes, or genes involved in DNA repair or replication. The tumor suppressor gene products frequently monitor the efficiency of cellular duplication by populating checkpoints in the process of cell division. When defective, the tumor suppressor genes can lead to inherited predispositions in the development of cancers. Almost every human cancer contains mutations in the tumor suppressor pathways of p53, retinoblastoma (Rb), or both. Each of these pathways receives a complex set of signals and reports from the extracellular and intracellular environments of a cell and in response regulate “go-no go” decisions in the cell cycle. This chapter will review some of the origins of research into the p53 gene and its protein. This will form a basis for understanding the other chapters of this book and provide a foundation upon which new facts are built. It also points to important future directions for this field.03/2007: pages 1-23;
- [show abstract] [hide abstract]
ABSTRACT: Mammalian cells have been reported to have a p53-dependent tetraploidy checkpoint that blocks cell cycle progression in G1 in response to failure of cell division. In most cases where the tetraploidy checkpoint has been observed cell division was perturbed by anti-cytoskeleton drug treatments. However, other evidence argues against the existence of a tetraploidy checkpoint. Cells that have failed to divide differ from normal cells in having two nuclei, two centrosomes, a decreased surface to volume ratio, and having undergone an abortive cytokinesis. We tested each of these to determine which, if any, cause a G1 cell cycle arrest. Primary human diploid fibroblasts with intact cell cycle checkpoints were used in all experiments. Synchronized cells exhibited G1 arrest in response to division failure caused by treatment with either cytochalasin or the myosin II inhibitor blebbistatin. The role of tetraploidy, aberrant centrosome number, and increased cell size were tested by cell/cell and cell/cytoplast fusion experiments; none of these conditions resulted in G1 arrest. Instead we found that various drug treatments of the cells resulted in cellular damage, which was the likely cause of the arrest. When cytokinesis was blocked in the absence of damage-inducing drug treatments no G1 arrest was observed. We show that neither tetraploidy, aberrant centrosome number, cell size, nor failure of cytokinesis lead to G1 arrest, suggesting that there is no tetraploidy checkpoint. Rather, certain standard synchronization treatments cause damage that is the likely cause of G1 arrest. Since tetraploid cells can cycle when created with minimal manipulation, previous reports of a tetraploidy checkpoint can probably be explained by side effects of the drug treatments used to observe them.BMC Cell Biology 02/2005; 6(1):6. · 2.81 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: Based on their mechanism of action, anti-tumor drugs that target the cell cycle can be generally divided into three categories, namely, blocking DNA synthesis, causing DNA damage, and disrupting mitotic processes. In terms of mitotic inhibitors, most compounds used in the clinic impair the normal function of mitotic spindles by targeting tubulins, basic building blocks of microtubules. In vivo, these compounds often exhibit significant side effects, thus limiting their efficacy. Mitotic processes are under tight control through surveillance mechanisms commonly termed checkpoints. Defects in the regulation of these checkpoints often result in genomic instability, which predisposes the cell to malignant transformation. As cancer is the consequence of uncontrolled cell division, great efforts have been devoted to discover drugs that target mitosis, thereby halting cell division and inducing mitotic catastrophe with minimal cytotoxicity to non-dividing or normally dividing cells. This review primarily focuses on mitotic proteins that have been explored as new targets for anti-cancer drug development during the past decade.Mini Reviews in Medicinal Chemistry 09/2006; 6(8):885-95. · 2.87 Impact Factor