[show abstract][hide abstract] ABSTRACT: The aim of this study was to delineate the temporal profile of adventitial microvessel (Ad-MV) formation after stenting, its relationship to arterial wall hypoxia, and the effects of a tyrosine kinase inhibitor (TKI), SU11218, on Ad-MV and in-stent intimal hyperplasia (IH).
Adventitial microvessels have been reported after arterial injury; however, the underlying stimulus for this response and its relationship to IH is unknown.
Coronary stenting was performed in 40 pigs randomized to SU11218 (n = 20) or placebo (n = 20). Vessel wall hypoxia was assessed by pimonidazole adducts and hypoxia-inducible factor (HIF)-1 alpha expression. Adventitial microvessels were quantified by three-dimensional microscopic computed tomography (3D micro CT). Intimal hyperplasia was measured by intravascular ultrasound (IVUS), 3D micro CT, and morphometry. The effects of SU11218 were assessed in vitro on smooth muscle cell (SMC) and endothelial cell (EC) functions and in vivo on Ad-MV and IH.
Hypoxia was evident in the vessel wall at 48 h and persisted for four weeks. Adventitial microvessels increased significantly at one week (24 +/- 7 microvessels/segment) and four weeks (23 +/- 7 microvessels/segment) compared with uninjured arteries (16 +/- 2 microvessels/segment; p < 0.001) and correlated with IH (r = 0.77, p < 0.001). The TKI SU11218 inhibited platelet-derived growth factor receptor-beta phosphorylation, EC and SMC DNA synthesis, and migration in a dose-dependent manner in vitro and significantly inhibited Ad-MV (16 +/- 5 vs. 23 +/- 7 microvessels/segment in placebo, p < 0.001) and produced approximately 80% reduction in IH (0.52 +/- 0.51 mm2 vs. 2.47 +/- 1.66 mm2 in placebo, p < 0.001) at four weeks in vivo.
Arterial stenting causes arterial wall hypoxia followed by Ad-MV formation. The TKI SU11218 inhibits both Ad-MV formation and IH and represents a promising therapeutic agent to prevent in-stent restenosis.
Journal of the American College of Cardiology 03/2006; 47(5):1067-75. · 14.09 Impact Factor
[show abstract][hide abstract] ABSTRACT: Point mutations constitute a major mode of oncogenic activation of the Met receptor tyrosine kinase. Met is aberrantly activated in many types of human malignancies and its deregulated activity is correlated with aggressive tumor traits such as abnormal proliferation and survival, leading to tumor growth, local invasion and metastasis. Here we report that the Met kinase inhibitor SU11274 differentially affects the kinase activity and subsequent signaling of various mutant forms of Met. Two Met variants tested, M1268T and H1112Y, were potently inhibited by 2 microM SU11274, while two other variants, L1213V and Y1248H, remained resistant under similar experimental conditions. Inhibition of the kinase altered cell proliferation, morphology and motility, while cells containing resistant mutants appeared unaffected by the compound. The basis for the sensitivity or resistance to SU11274 is discussed in terms of the position of the mutations predicted from a homology model.
[show abstract][hide abstract] ABSTRACT: Loss of the DNA-dependent protein kinase (DNA-PK) results in increased sensitivity to ionizing radiation due to inefficient repair of DNA double-strand breaks. Overexpression of DNA-PK in tumor cells conversely results in resistance to ionizing radiation. It is therefore possible that inhibition of DNA-PK will enhance the preferential killing of tumor cells by radiotherapy. Available inhibitors of DNA-PK, like wortmannin, are cytotoxic and stop the cell cycle because they inhibit phoshatidylinositol-3-kinases at 100-fold lower concentrations required to inhibit DNA-PK. In an effort to develop a specific DNA-PK inhibitor, we have characterized SU11752, from a three-substituted indolin-2-ones library. SU11752 and wortmannin were equally potent inhibitors of DNA-PK. In contrast, inhibition of the phoshatidylinositol-3-kinase p110gamma required 500-fold higher concentration of SU11752. Thus, SU11752 was a more selective inhibitor of DNA-PK than wortmannin. Inhibition kinetics and a direct assay for ATP binding showed that SU11752 inhibited DNA-PK by competing with ATP. SU11752 inhibited DNA double-strand break repair in cells and gave rise to a five-fold sensitization to ionizing radiation. At concentrations of SU11752 that inhibited DNA repair, cell cycle progression was still normal and ATM kinase activity was not inhibited. We conclude that SU11752 defines a new class of drugs that may serve as a starting point for the development of specific DNA-PK inhibitors.
[show abstract][hide abstract] ABSTRACT: The hepatocyte growth factor/scatter factor (HGF/SF) receptor, Met, mediates various cellular responses on activation with its ligand, including proliferation, survival, motility, invasion, and tubular morphogenesis. Met expression is frequently up-regulated in sarcomas and carcinomas. Experimental evidence suggests that Met activation correlates with poor clinical outcome and the likelihood of metastasis. Therefore, inhibitors of Met tyrosine kinase may be useful for the treatment of a wide variety of cancers that have spread from the primary site. We have discovered potent and selective pyrrole-indolinone Met kinase inhibitors and characterized them for their ability to inhibit HGF/SF-induced cellular responses in vitro. These compounds inhibit HGF/SF-induced receptor phosphorylation in a dose-dependent manner. They also inhibit the HGF/SF-induced motility and invasion of epithelial and carcinoma cells. Therefore, these compounds represent a class of prototype small molecules that selectively inhibit the Met kinase and could lead to identification of compounds with potential therapeutic utility in treatment of cancers.
Molecular Cancer Therapeutics 12/2003; 2(11):1085-92. · 5.60 Impact Factor
[show abstract][hide abstract] ABSTRACT: Vascular endothelial growth factor (VEGF) is a key driver of the neovascularization and vascular permeability that leads to the loss of visual acuity in diabetic retinopathy and neovascular age-related macular degeneration. Our aim was to identify an orally active, selective small molecule kinase inhibitor of vascular endothelial growth factor receptor (VEGFR)-2 with activity against both VEGF-induced angiogenesis and vascular permeability. We used a biochemical assay to identify 3-[5-methyl-2- (2-oxo-1,2-dihydro-indol-3-ylidenemethyl)-1H-pyrrol-3-yl]-proprionic acid (SU10944), a pyrrole indolinone, which is a potent ATP-competitive inhibitor of VEGFR-2 (Ki of 21 +/- 5 nM). In cellular assays, SU10944 inhibited VEGF-induced receptor autophosphorylation (IC50 of 227 +/- 80 nM) as well as downstream signaling (IC50 of 102 +/- 27 nM). In biochemical assays, SU10944 exhibits potent inhibitory activity against VEGFR-1; weak activity against other related subgroup members, including stem cell factor receptor (SCFR), platelet-derived growth factor receptor beta (PDGFRbeta), and fibroblast growth factor receptor-1 (FGFR-1); and no detectable activity against other protein tyrosine kinases such as epidermal growth factor receptor (EGFR), Src, and hepatocyte growth factor receptor. In cellular assays, the selectivity for SU10944 to inhibit VEGFR is maintained compared with other tyrosine kinases (IC50 for SCFR of 1.6 +/- 0.3 microM, for PDGFRbeta of 30.6 +/- 13.3 microM, for FGFR-1 of >50 microM, and for EGFR of >50 microM). Upon oral administration, SU10944 gave a clear dose response in the corneal micropocket model with an ED50 value for inhibition of neovascularization of approximately 30 mg/kg and a maximum inhibition of 95% at 300 mg/kg. Similarly, upon oral administration in the Miles assay, SU10944 potently inhibited VEGF-induced vascular permeability. Our data indicate that small molecule inhibitors of VEGFR signaling have the potential to ameliorate VEGF-induced neovascularization as well as vascular permeability.
Journal of Pharmacology and Experimental Therapeutics 09/2003; 306(3):838-45. · 3.89 Impact Factor
[show abstract][hide abstract] ABSTRACT: In recent decades, radiation research has concentrated primarily on the cancer cell compartment. Much less is known about the effect of ionizing radiation on the endothelial cell compartment and the complex interaction between tumor cells and their microenvironment. Here we report that ionizing radiation is a potent antiangiogenic agent that inhibits endothelial cell survival, proliferation, tube formation and invasion. Vascular endothelial growth factor (VEGF) and basic fibroblast growth factor were able to reduce the radiosensitivity of endothelial cells. Yet, it is also found that radiation induces angiogenic factor production by tumor cells that can be abrogated by the addition of antiangiogenic agents. Receptor tyrosine kinase inhibitors of Flk-1/KDR/VEGFR2, FGFR1 and PDGFR beta, SU5416, and SU6668 enhanced the antiangiogenic effects of direct radiation of the endothelial cells. In a coculture system of PC3 prostate cancer cells and endothelial cells, isolated irradiation of the PC3 cells enhanced endothelial cell invasiveness through a Matrigel matrix, which was inhibited by SU5416 and SU6668. Furthermore, ionizing radiation up-regulated VEGF and basic fibroblast growth factor in PC3 cells and VEGFR2 in endothelial cells. Together these findings suggest a radiation-inducible protective role for tumor cells in the support of their associated vasculature that may be down-regulated by coadministration of angiogenesis inhibitors. These results rationalize concurrent administration of angiogenesis inhibitors and radiotherapy in cancer treatment.
Cancer Research 08/2003; 63(13):3755-63. · 8.65 Impact Factor
[show abstract][hide abstract] ABSTRACT: HGK (hepatocyte progenitor kinase-like/germinal center kinase-like kinase) is a member of the human STE20/mitogen-activated protein kinase kinase kinase kinase family of serine/threonine kinases and is the ortholog of mouse NIK (Nck-interacting kinase). We have cloned a novel splice variant of HGK from a human tumor line and have further identified a complex family of HGK splice variants. We showed HGK to be highly expressed in most tumor cell lines relative to normal tissue. An active role for this kinase in transformation was suggested by an inhibition of H-Ras(V12)-induced focus formation by expression of inactive, dominant-negative mutants of HGK in both fibroblast and epithelial cell lines. Expression of an inactive mutant of HGK also inhibited the anchorage-independent growth of cells yet had no effect on proliferation in monolayer culture. Expression of HGK mutants modulated integrin receptor expression and had a striking effect on hepatocyte growth factor-stimulated epithelial cell invasion. Together, these results suggest an important role for HGK in cell transformation and invasiveness.
Molecular and Cellular Biology 04/2003; 23(6):2068-82. · 5.37 Impact Factor
[show abstract][hide abstract] ABSTRACT: Mutations in the Ras family of GTP binding proteins represent one of the most frequently observed genetic alterations in human
cancers. We and others have recently demonstrated that expression of Met, the tyrosine kinase receptor for hepatocyte growth
factor/scatter factor (HGF/SF), is significantly up-regulated in Ras-transformed cells. Because HGF/SF-Met signaling is proposed
to play a prominent role in tumor development and progression, we assessed the possible requirement for Met during Ras-mediated
tumor growth and metastasis. To disrupt endogenous Met signaling, we constructed dominant-negative mutants of both human and
murine Met and showed that these can inhibit HGF/SF-mediated Met signaling and cell invasion of ras-transformed cells in vitro. Moreover, ectopic expression of dominant-negative Met mutants reduced the s.c. tumor growth of ras-transformed cells and dramatically suppressed their ability to form lung metastases in vivo. Our data demonstrate that Met plays a prominent role during Ras-mediated tumor growth and metastasis, and further suggest
that agents that inhibit HGF/SF-Met signaling may represent an important therapeutic avenue for the treatment of a variety
of malignant tumors.
Proceedings of the National Academy of Sciences 09/2001; 98(19):10722-10727. · 9.74 Impact Factor
[show abstract][hide abstract] ABSTRACT: The effect of combining SU5416 with fractionated radiotherapy or with low molecular weight (LMW) heparin (dalteparin) was studied in U87 human glioblastoma xenografts in nude mice. SU5416 is antiangiogenic by a specific inhibition of the vascular endothelial growth factor receptor 2 (VEGFR-2), and heparins are assumed to bind VEGF. Both SU5416 (100 mg/kg every second day in 5 days) and 3 Gyx5 produced moderate, yet significant, growth inhibition. Tumors treated with concomitant irradiation and short-term SU5416 maintained a lower growth rate during regrowth than the other treatment groups (P=.007). Dalteparin (1000 IE/kg subcutaneously once a day) had no growth-inhibitory effect on its own, but when this LMW heparin was added to the SU5416 schedule, a significantly enhanced growth inhibition was obtained. VEGF protein content in tumors was not significantly altered by SU5416, but a significant decrease in VEGF levels was found in tumors treated with concomitant dalteparin and SU5416 compared with controls (P=.03). We conclude that: 1) an additive growth-inhibitory effect is obtained by combining SU5416 and fractionated radiotherapy; and 2) LMW heparin (dalteparin), in combination with SU5416, decreases the level of VEGF in tumors and increases the growth-inhibitory effect of SU5416.