Targeting Fibronectin for Cancer Imaging and Therapy

During cancer progression, the extracellular matrix (ECM) undergoes dramatic changes, which promote cancer cell migration and invasion. In the remodeled tumor ECM, fibronectin (FN) level is upregulated to assist tumor growth, progression, and invasion. FN serves as a central organizer of ECM molecules and mediates the crosstalk between the tumor microenvironment and cancer cells. Its upregulation is correlated with angiogenesis, cancer progression, metastasis, and drug resistance. A number of FN-targeting ligands have been developed for cancer imaging and therapy. Thus far, FN-targeting imaging agents have been tested for nuclear imaging, MRI, and fluorescence imaging, for tumor detection and localization. FN-targeting therapeutics, including nuclear medicine, chemotherapy drugs, cytokines, and photothermal moieties, were also developed in cancer therapy. Because of the prevalence of FN overexpression in cancer, FN targeting imaging agents and therapeutics have the promise of broad applications in the diagnosis, treatment, and image-guided interventions of many types of cancers. This review will summarize current understanding on the role of FN in cancer, discuss the design and development of FN-targeting agents, and highlight the applications of these FN-targeting agents in cancer imaging and therapy.

Effect of pretreatment of ezetimibe/simvastatin on arterial healing and endothelialization after drug-eluting stent implantation in a porcine coronary restenosis model

Background and Objectives

We sought to evaluate the effect of the early use of ezetimibe/simvastatin (Vytorin®) on arterial healing and endothelialization after the implantation of a drug-eluting stent (DES) in a porcine model of coronary restenosis.

Materials and Methods

A total of 20 pigs (40 coronary arteries) were randomly allocated to a pretreatment or no treatment group. The pretreatment group (n=20) received oral ezetimibe/simvastatin (10/20 mg) daily for 7 days before stenting and the no pretreatment group (n=20) did not. All pigs were treated with ezetimibe/simvastatin (10/20 mg) daily after stenting for 4 weeks. Stenting was performed using a bare-metal stent (BMS, n=10) and three types of DES: biolimus A9-eluting stent (BES, n=10), zotarolimus-eluting stent (ZES, n=10), and everolimus-eluting stents (EES, n=10). Four weeks later, pigs underwent a follow-up coronary angiography and were sacrificed for histopathologic analysis.

Results

There were no significant differences between the pretreatment and no pretreatment groups in the internal elastic lamina area, lumen area, neointima area, stenotic area, injury score, fibrin score, and inflammation score. In both groups, the fibrin score was higher in pigs with DES than in BMS, particularly in ZES and EES. The inflammatory score was not different between DES and BMS.

Conclusion

In a porcine model of coronary restenosis, pretreatment with ezetimibe/simvastatin before DES implantation failed to improve arterial healing and endothelialization compared to treatment after stenting.

Quantitative Longitudinal Imaging of Vascular Inflammation and Treatment by Ezetimibe in apoE Mice by FMT Using New Optical Imaging Biomarkers of Cathepsin Activity and α(v)β(3) Integrin

Inflammation as a core pathological event of atherosclerotic lesions is associated with the secretion of cathepsin proteases and the expression of α_vβ₃ integrin. We employed fluorescence molecular tomographic (FMT) noninvasive imaging of these molecular activities using cathepsin sensing (ProSense, CatB FAST) and α_vβ₃ integrin (IntegriSense) near-infrared fluorescence (NIRF) agents. A statistically significant increase in the ProSense and IntegriSense signal was observed within the chest region of apoE^−/− mice (P < 0.05) versus C57BL/6 mice starting 25 and 22 weeks on high cholesterol diet, respectively. In a treatment study using ezetimibe (7 mg/kg), there was a statistically significant reduction in the ProSense and CatB FAST chest signal of treated (P < 0.05) versus untreated apoE^−/− mice at 31 and 21 weeks on high cholesterol diet, respectively. The signal of ProSense and CatB FAST correlated with macrophage counts and was found associated with inflammatory cells by fluorescence microscopy and flow cytometry of cells dissociated from aortas. This report demonstrates that cathepsin and α_vβ₃ integrin NIRF agents can be used as molecular imaging biomarkers for longitudinal detection of atherosclerosis, and cathepsin agents can monitor anti-inflammatory effects of ezetimibe with applications in preclinical testing of therapeutics and potentially for early diagnosis of atherosclerosis in patients.

Local delivery of IL-2 reduces atherosclerosis via expansion of regulatory T cells

OBJECTIVE

Recent studies indicate that regulatory T cells (Tregs) attenuate murine atherosclerosis. Since interleukin (IL)-2 induces Tregs proliferation, we tested the impact of L19-IL2, a fusion antibody specific to extra-domain B of fibronectin (ED-B) containing an active human IL-2 molecule, in experimental atherosclerosis.

METHODS AND RESULTS

L19-IL2 or appropriate controls were given intravenously to 6 month old Western diet-fed apoE(-/-) mice on day 1, 3, and 5. Human IL-2 was detected on day 7 within atherosclerotic plaques of L19-IL2-treated mice, and magnetic resonance imaging of the plaques showed a significant adventitial gadolinium enhancement on day 7 and 13, suggesting microvascular leakage as a result of the pharmacodynamic activity of L19-IL2. Treatment with L19-IL2 significantly reduced the size of pre-established atherosclerotic plaques at the thoracic aorta (Sudan III stained area) and in the aortic root area (microscopic, morphometric analysis) on day 7 as compared to controls (L19, D1.3-IL2, NaCl) as well as compared to baseline (day 0). Tregs markers Foxp3 and CTLA4 were highly increased in plaques after L19-IL2 treatment compared to controls (p<0.01), whereas the macrophage marker Mac3 was significantly reduced (p<0.03). Co-treatment with IL-2-receptor blocking antibody PC61 abrogated L19-IL2-induced plaque reduction compared with IgG control (p<0.03).

CONCLUSION

L19-IL2 delivers functional IL-2 to pre-established atherosclerotic plaques of WD-fed apoE(-/-) mice resulting in significant plaque size reduction mediated by local Tregs.

Optical and magnetic resonance imaging as complementary modalities in drug discovery

Imaging has the ability to study various biological and chemical processes noninvasively in living subjects in a longitudinal way. For this reason, imaging technologies have become an integral part of the drug-discovery and development program and are commonly used in following disease processes and drug action in both preclinical and clinical stages. As the domain of imaging sciences transitions from anatomical/functional to molecular applications, the development of molecular probes becomes crucial for the advancement of the field. This review summarizes the role of two complementary techniques, magnetic resonance and fluorescence optical imaging, in drug discovery. While the first approach exploits intrinsic tissue characteristics as the source of image contrast, the second necessitates the use of appropriate probes for signal generation. The anatomical, functional, metabolic and molecular information that becomes accessible through imaging can provide invaluable insights into disease mechanisms and mechanisms of drug action.

Potential therapeutic uses for ezetimibe beyond lowering LDL-c to decrease cardiovascular events

Ezetimibe is a relatively new drug that inhibits the absorption of dietary cholesterol in the small intestine. It is a low density lipoprotein-cholesterol (LDL-C) lowering medication that acts directly on the intestine by inhibiting Niemann-Pick C1 Like1 (NPC1L1). Recently, results of the ARBITER 6-HALTS trial (Arterial Biology for the Investigation of the Treatment Effects of Reducing Cholesterol 6-HDL and LDL Treatment Strategies) and the ENHANCE trial (Ezetimibe and Simvastatin in Hypercholesterolemia Enhances Atherosclerosis Regression) showed that ezetimibe had no effect on atherosclerosis despite producing a marked decrease in LDL-C. Recent studies show a potential benefit of ezetimibe in treating insulin resistance, non-alcoholic fatty liver disease (NAFLD), gallstones and dyslipidaemia associated with chronic renal failure and organ transplantation. All of these conditions are known to be associated with an increase in risk of cardiovascular disease (CVD) and further studies are needed to assess the potential benefits of ezetimibe in these therapeutics areas.

Optical molecular imaging in atherosclerosis

Current imaging techniques focus on evaluating the anatomical structure of blood vessel wall and atherosclerotic plaque. These techniques fail to evaluate the biological processes which take place in the vessel wall and inside the plaque. Novel imaging techniques like optical imaging can evaluate the biological and cellular processes inside the plaque and provide information which can be vital for better patient risk stratification. This review highlights the various optical imaging techniques and their application in assessing biological processes in atherosclerosis.

Molecular Imaging of Cathepsin B Proteolytic Enzyme Activity Reflects the Inflammatory Component of Atherosclerotic Pathology and Can Quantitatively Demonstrate the Antiatherosclerotic Therapeutic Effects of Atorvastatin and Glucosamine

Inflammation in atherosclerotic plaques causes plaque vulnerability and rupture, leading to thromboembolic complications. Cathepsin B (CatB) proteases secreted by macrophages play a major role in plaque inflammation. We used a CatB-activatable near-infrared fluorescence (NIRF) imaging agent to demonstrate the inflammatory component in mice atheromata and the atherosclerosis-modulating effects of atorvastatin or glucosamine treatments. Apolipoprotein E knockout mice ( n = 35) were fed normal chow, a Western diet, a Western diet + atorvastatin, a Western diet + glucosamine, or a Western diet + atorvastatin + glucosamine for 14 weeks. Twenty-four hours after the intravenous injection of a CatB-activatable probe, ex vivo NIRF imaging of the aortas and brains was performed, followed by histology. The CatB-related signal, observed in the aortas but not in the cerebral arteries, correlated very well with protease activity and the presence of macrophages on histology. Animals on Western diets could be distinguished from animals on a normal diet. The antiatherosclerotic effects of atorvastatin and glucosamine could be demonstrated, with reduced CatB-related signal compared with untreated animals. Plaque populations were heterogeneous within individuals, with some plaques showing a high and others a lower CatB-related signal. These differences in signal intensity could not be predicted by visual inspection of the plaques but did correlate with histologic evidence of inflammation in every case. This suggests that vulnerable inflamed plaques can be identified by optical molecular imaging.