tachpyr and Neoplasms

As new compounds are being evaluated for use in clinical trials involving antiangiogenic therapies, two important factors must be considered. Independent of clinical efficacy, the potential drug must be cost-effective and have reasonable ease of production. The compound endostatin (Entremed, Inc.) has recently completed two Phase I trials with minimal toxicity to the patients treated [1,2]. However, due to the difficulty and expense of producing large quantities of a recombinant protein, Entremed Inc. has experienced financial difficulties [3]. As this company's fate indicates, a drug must not only be clinically effective, but must also possess reasonable production economics. Another interesting component of compound development is selectivity. Highly selective antiangiogenic compounds such as the tyrosine kinase inhibitor SU-5416 are being replaced by less selective compounds such as SU-6668, which acts on a broader spectrum of tyrosine kinase receptors [4]. This move towards using less selective antiangiogenic compounds is based on preclinical models that demonstrate both better clinical efficacy when using less specific molecules and low response rates from the more selective compounds. With the aim of further examining broadly-acting antiangiogenic agents, the authors are currently evaluating new classes of agents that preferentially bind copper and inhibit angiogenesis. Copper has been known to be a significant target for antiangiogenic therapy for a number of years [5]. Recently, through the use of molecular techniques, the target enzymes that utilise copper as a cofactor are being elucidated. This review will describe the historical use of anticopper therapy for the treatment of Wilson's disease and evaluate some of the new anticopper compounds currently under consideration for use in antiangiogenic therapy.

Topics: Angiogenesis Inhibitors; Animals; Chelating Agents; Chelation Therapy; Copper; Corneal Neovascularization; Cyclohexylamines; Hepatolenticular Degeneration; Humans; Molybdenum; Neoplasms; Neovascularization, Pathologic; Penicillamine; Pyridines; Rabbits; Trientine

Iron is critical for cell growth and proliferation. Iron chelators are being explored for a number of clinical applications, including the treatment of neurodegenerative disorders, heart disease, and cancer. To uncover mechanisms of action of tachpyridine, a chelator currently undergoing preclinical evaluation as an anticancer agent, cell-cycle analysis was performed. Tachpyridine arrested cells at G2, a radiosensitive phase of the cell cycle, and enhanced the sensitivity of cancer cells but not nontransformed cells to ionizing radiation. G2 arrest was p53 independent and was accompanied by activation of the checkpoint kinases CHK1 and CHK2. G2 arrest was blocked by UCN-01, a CHK1 inhibitor, but proceeded in CHK2 knock-out cells, indicating a critical role for CHK1 in G2 arrest. Tachpyridine-induced cell-cycle arrest was abrogated in cells treated with caffeine, an inhibitor of the ataxia-telangiectasia mutated/ataxia-telangiectasia-mutated and Rad3-related (ATM/ATR) kinases. Further, G2 arrest proceeded in ATM-deficient cells but was blocked in ATR-deficient cells, implicating ATR as the proximal kinase in tachpyridine-mediated G2 arrest. Collectively, our results suggest that iron chelators may function as antitumor and radioenhancing agents and uncover a previously unexplored activity of iron chelators in activation of ATR and checkpoint kinases.

Topics: Ataxia Telangiectasia Mutated Proteins; Cell Cycle Proteins; Cell Division; Cell Line, Tumor; Checkpoint Kinase 1; Checkpoint Kinase 2; Chelating Agents; Cyclohexylamines; DNA-Binding Proteins; Enzyme Activation; G2 Phase; Humans; Metals; Neoplasms; Phosphorylation; Protein Kinases; Protein Serine-Threonine Kinases; Pyridines; Radiation, Ionizing; Tumor Suppressor Protein p53; Tumor Suppressor Proteins