ppi-2458 and fumagillin

Angiogenesis inhibition, long studied in the treatment of malignancies, has begun to emerge as a potential therapeutic approach in managing inflammatory arthritis, particularly rheumatoid arthritis. The growth of new vessels is required for the development of the rheumatoid pannus, which then leads to extensive synovial inflammation and joint destruction. Vascular endothelial growth factor is the best studied mediator of angiogenesis, and several therapies have been developed that specifically target this molecule. Several other angiogenesis mediators, such as the angiopoietin-TIE system, hypoxia inducible factor and integrin alpha(V)beta(3), as well as naturally occurring inhibitors of angiogenesis, are also being investigated as potential therapeutic targets. Additionally, there are a number of drugs, including paclitaxel, 2-methoxyestradiol and fumagillin analogs, that might have a role in inhibiting angiogenesis and, thus, in treating proliferative synovitis.

Topics: Angiopoietins; Cyclohexanes; Epoxy Compounds; Fatty Acids, Unsaturated; Humans; Hypoxia-Inducible Factor 1; Integrin alphaVbeta3; Neovascularization, Pathologic; O-(Chloroacetylcarbamoyl)fumagillol; Receptor, TIE-2; Sesquiterpenes; Synovitis; Tubulin Modulators; Valine; Vascular Endothelial Growth Factor A

The dependence of cell growth on methionine aminopeptidase (MetAP) function in bacteria and yeast is firmly established. Here we report experimental evidence that the control of cell proliferation in mammalian cells is directly linked and strictly dependent on the activity of both MetAP-1 and MetAP-2. The targeted downregulation of either methionine aminopeptidase MetAP-1 or MetAP-2 protein expression by small interfering RNA (siRNA) significantly inhibited the proliferation of human umbilical vein endothelial cells (HUVEC) (70%-80%), while A549 human lung carcinoma cell proliferation was less inhibited (20%-30%). The cellular levels of MetAP-2 enzyme were measured after MetAP-2 siRNA treatment and found to decrease over time from 4 to 96 h, while rapid and complete depletion of MetAP-2 enzyme activity was observed after 4 h treatment with two pharmacological inhibitors of MetAP-2, PPI-2458 and fumagillin. When HUVEC and A549 cells were treated simultaneously with MetAP-2 siRNA and PPI-2458, or fumagillin, which irreversibly inhibit MetAP-2 enzyme activity, no additive effect on maximum growth inhibition was observed. This strongly suggests that MetAP-2 is the single critical cellular enzyme affected by either MetAP-2 targeting approach. Most strikingly, despite their significantly different sensitivity to growth inhibition after targeting of either MetAP-1 or MetAP-2, HUVEC, and A549 cells, which were made functionally deficient in both MetAP-1 and MetAP-2 were completely or almost completely inhibited in their growth, respectively. This closely resembled the observed growth inhibition in genetically double-deficient map1map2 yeast strains. These results suggest that MetAP-1 and MetAP-2 have essential functions in the control of mammalian cell proliferation and that MetAP-dependent growth control is evolutionarily highly conserved.

Topics: Aminopeptidases; Cell Proliferation; Cells, Cultured; Cyclohexanes; Down-Regulation; Epithelial Cells; Epoxy Compounds; Fatty Acids, Unsaturated; Humans; Methionyl Aminopeptidases; RNA, Small Interfering; Saccharomyces cerevisiae; Sesquiterpenes; Transcription, Genetic; Umbilical Veins; Valine

The hallmark of rheumatoid arthritis (RA) is the progressive destruction of articular joints, characterized by invasive synovial hyperplasia and pathological neovascularization. Here we report that PPI-2458, a member of the fumagillin class of irreversible methionine aminopeptidase-2 (MetAP-2) inhibitors, potently inhibits the proliferation of human fibroblast-like synoviocytes (HFLS-RA), derived from RA patients, with a growth inhibitory concentration 50 (GI(50)) of 0.04 nM and a maximum inhibition of >95% at 1 nM. Human umbilical vein endothelial cells (HUVEC) are similarly inhibited in proliferation by PPI-2458 (GI(50), 0.2 nM). We developed a method to measure the level of MetAP-2 enzyme inhibition after exposure to PPI-2458 and demonstrate that growth inhibition of PPI-2458-sensitive HFLS-RA and HUVEC is linked to MetAP-2 enzyme inhibition, in a dose-dependent fashion. The secretion of several inflammatory mediators such as IL-6 and vascular endothelial growth factor from activated HFLS-RA was not inhibited by PPI-2458. The CNS toxicity profile of PPI-2458, determined by the incidence of seizures, is significantly improved over that of the parental compound TNP-470. In the rat model of peptidoglycan-polysaccharide-induced arthritis, PPI-2458 significantly attenuated paw swelling when therapeutically administered after the onset of chronic disease. We suggest that the mechanism of PPI-2458 action, highly selective and potent anti-proliferative activity on HFLS-RA and HUVEC in vitro, a significantly improved CNS toxicity profile, and marked attenuation of chronic disease in the rat peptidoglycan-polysaccharide arthritis model in vivo, positions this compound as a drug for the treatment of RA.

Topics: Aminopeptidases; Animals; Anti-Inflammatory Agents; Antirheumatic Agents; Arthritis, Rheumatoid; Cell Division; Cells, Cultured; Cyclohexanes; Down-Regulation; Endothelial Cells; Enzyme Inhibitors; Epoxy Compounds; Fatty Acids, Unsaturated; Humans; Metalloendopeptidases; Proliferating Cell Nuclear Antigen; Rats; Sesquiterpenes; Synovial Membrane; Valine