In vitro and in vivo comparison of MRI chemical exchange saturation transfer (CEST) properties between native glucose and 3-O-Methyl-D-glucose in a murine tumor model.

D-Glucose and 3-O-Methyl-D-glucose (3OMG) have been shown to provide contrast in magnetic resonance imaging-chemical exchange saturation transfer (MRI-CEST) images. However, a systematic comparison between these two molecules has yet to be performed. The current study deals with the assessment of the effect of pH, saturation power level (B1 ) and magnetic field strength (B0 ) on the MRI-CEST contrast with the aim of comparing the in vivo CEST contrast detectability of these two agents in the glucoCEST procedure. Phosphate-buffered solutions of D-Glucose or 3OMG (20 mM) were prepared at different pH values and Z-spectra were acquired at several B1 levels at 37°C. In vivo glucoCEST images were obtained at 3 and 7 T over a period of 30 min after injection of D-Glucose or 3OMG (at doses of 1.5 or 3 g/kg) in a murine melanoma tumor model (n = 3-5 mice for each molecule, dose and B0 field). A markedly different pH dependence of CEST response was observed in vitro for D-Glucose and 3OMG. The glucoCEST contrast enhancement in the tumor region following intravenous administration (at the 3 g/kg dose) was comparable for both molecules: 1%-2% at 3 T and 2%-3% at 7 T. The percentage change in saturation transfer that resulted was almost constant for 3OMG over the 30-min period, whereas a significant increase was detected for D-Glucose. Our results show similar CEST contrast efficiency but different temporal kinetics for the metabolizable and the nonmetabolizable glucose derivatives in a tumor murine model when administered at the same doses.

Novel Gastrin-Releasing Peptide Receptor Targeted Near-Infrared Fluorescence Dye for Image-Guided Surgery of Prostate Cancer.

PURPOSE: Prostate cancer (PCa), the most widespread male cancer in western countries, is generally eradicated by surgery, especially if localized. However, during surgical procedures, it is not always possible to identify malignant tissues by visual inspection. Among the possible consequences, there is the formation of positive surgical margins, often associated with recurrence. In this work, the gastrin-releasing peptide receptor (GRPR), overexpressed in the prostatic carcinoma and not in healthy tissues or in benign hyperplasia (BPH), is proposed as target molecule to design a novel near-infrared fluorescent (NIRF) probe for image-guided prostatectomy. PROCEDURES: The NIRF dye Sulfo-Cy5.5 was conjugated to a Bombesin-like peptide (BBN), targeting GRPR. The final product, called BBN-Cy5.5, was characterized and tested in vitro on PC-3, DU145, and LnCAP cell lines, using unconjugated Sulfo-Cy5.5 as control. In vivo biodistribution studies were performed by optical imaging in PC-3 tumor-bearing and healthy mice. Finally, simulation of the surgical protocol was carried out. RESULTS: BBN-Cy5.5 showed high water solubility and a good relative quantum yield. The ability of the probe to recognize the GRPR, highly expressed in PC-3 cells, was tested both in vitro and in vivo, where a significant tumor accumulation was achieved 24 h post-injection. Furthermore, a distinguishable fluorescent signal was visible in mice bearing PCa, when the surgery was simulated. By contrast, low signal was found in healthy or BPH-affected mice. CONCLUSIONS: This work proposes a new NIRF probe ideal to target GRPR, biomarker of PCa. The promising data obtained suggest that the dye could allow the real-time intraoperative visualization of prostate cancer.

In Vivo Imaging of Tumor Metabolism and Acidosis by Combining PET and MRI-CEST pH Imaging.

The vast majority of cancers exhibit increased glucose uptake and glycolysis regardless of oxygen availability. This metabolic shift leads to an enhanced production of lactic acid that decreases extracellular pH (pHe), a hallmark of the tumor microenvironment. In this way, dysregulated tumor pHe and upregulated glucose metabolism are linked tightly and their relative assessment may be useful to gain understanding of the underlying biology. Here we investigated noninvasively the in vivo correlation between tumor 18F-FDG uptake and extracellular pH values in a murine model of HER2+ breast cancer. Tumor extracellular pH and perfusion were assessed by acquiring MRI-CEST (chemical exchange saturation transfer) images on a 3T scanner after intravenous administration of a pH-responsive contrast agent (iopamidol). Static PET images were recorded immediately after MRI acquisitions to quantify the extent of 18F-FDG uptake. We demonstrated the occurrence of tumor pHe changes that report on acidification of the interstitial fluid caused by an accelerated glycolysis. Combined PET and MRI-CEST images reported complementary spatial information of the altered glucose metabolism. Notably, a significant inverse correlation was found between extracellular tumor pH and 18F-FDG uptake, as a high 18F-FDG uptake corresponds to lower extracellular pH values. These results show how merging the information from 18F-FDG-uptake and extracellular pH measurements can improve characterization of the tumor microenvironment. Cancer Res; 76(22); 6463-70. ©2016 AACR.

Diolein Based Nanostructures as Targeted Theranostics.

Diolein based non-targeted theranostic nanoparticles (DO-NPs) containing 10%wt of the amphiphilic Gadolinium complex (C18)2DTPA(Gd), and targeted NPs, obtained by introducing growing amounts (3% wt, 6% wt or 10% wt) of (C18)2-Peg3000- FA in the sample composition, have been studied for their in vitro and in vivo properties. Cellular binding was studied by lCP-MS analysis of the Gadolinium content and by Surface Plasmon Resonance (SPR) assays. The best formulation in terms of selectivity towards IGROV-1 cells with respect to non-targeted DO-NPs, was that containing 3% (C18)2Peg3000- FA (P < 0.01). Cytotoxic studies and confocal microscopy analysis of IGROV-1 cells indicate high selective properties of the targeted doxorubicin (DOX) loaded NPs. Nanoparticles described here represent the first example in which a targeted carrier characterized by a stable foamy mesophase, provided by the Diolein component, combine the therapeutic effect due to the anticancer drug doxorubicin, with the imaging properties provided by paramagnetic gadolinium complexes for MRI. As evidenced by T(1w), and T(2w) MRI images and by the in vivo antitumor effect in IGROV-1 tumor-bearing mice, DO-NP3-FA/DOX provides very high therapeutic efficacy with a tumor growth regression of 80% and 50% higher as compared to the mice treated with saline solution and with Doxil, respectively.

In Vitro and In Vivo Assessment of Nonionic Iodinated Radiographic Molecules as Chemical Exchange Saturation Transfer Magnetic Resonance Imaging Tumor Perfusion Agents.

OBJECTIVES: The aim of this study was to evaluate 4 nonionic x-ray iodinated contrast agents (CAs), commonly used in radiographic procedures, as novel chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) agents by assessing their in vitro exchange properties and preliminary in vivo use as tumor enhancing agents. MATERIALS AND METHODS: The CEST properties, as function of pH (range, 5.5-7.9) and of radio frequency conditions (irradiation field strength range of 1-9 µT and time of 1-9 seconds), have been determined at 7 T and 310 K for 4 x-ray CAs commonly used in clinical settings, namely, iomeprol, iohexol, ioversol, and iodixanol. Their in vivo properties have been investigated upon intravenous injection in a murine HER2+ breast tumor model (n = 4 mice for each CA) using both computed tomography (CT) and MRI modalities. RESULTS: The prototropic exchange rates measured for the 4 investigated iodinated molecules showed strong pH dependence with base catalyzed exchange rate that was faster for monomeric compounds (20-4000 Hz in the pH range of 5.5-7.9). Computed tomography quantification showed marked (up to 2 mg I/mL concentration) and prolonged accumulation (up to 30 minutes postinjection) inside tumor regions. Among the 4 agents we tested, iohexol and ioversol display good CEST contrast properties at 7 T, and in vivo results confirmed strong and prolonged contrast enhancement of the tumors, with elevated extravasation fractions (74%-91%). A strong and significant correlation was found between CT and CEST-MRI tumor-enhanced images (R = 0.70, P < 0.01). CONCLUSIONS: The obtained results demonstrate that iohexol and ioversol, 2 commonly used radiographic compounds, can be used as MRI perfusion agents, particularly useful when serial images acquisitions are needed to complement CT information.

The one-step synthesis and surface functionalization of dumbbell-like gold-iron oxide nanoparticles: a chitosan-based nanotheranostic system.

The first one-step synthesis of dumbbell-like gold-iron oxide nanoparticles has been reported here. Surface functionalization with a biocompatible chitosan matrix allowed us to obtain a novel targetable diagnostic and therapeutic tool.

Beta-site APP cleaving enzyme up-regulation induced by 4-hydroxynonenal is mediated by stress-activated protein kinases pathways.

4-Hydroxynonenal (HNE), an aldehydic product of lipid peroxidation, up-regulates expression of the beta-site APP cleaving enzyme (BACE-1), an aspartyl protease responsible for the beta-secretase cleavage of amyloid precursor protein (AbetaPP), and results in increased levels of amyloid beta (Abeta) peptide. The mechanisms underlying this remain unclear but are of fundamental importance because prevention of BACE-1 up-regulation is viewed as an important therapeutic strategy. In this study, we exposed NT(2) neurons to a range of HNE concentrations (0.5-5 microm) that elicited an up-regulation of BACE-1 expression, a significant increase in intracellular and secreted levels of Abeta peptides as well as apoptosis involving poly-ADP ribose polymerase cleavage and activation of caspase 3. To delineate the molecular events involved in HNE-mediated BACE-1 activation, we investigated the involvement of stress-activated protein kinases (SAPK), signal transducers and activators of transcription (STAT) and serine-threonine kinase B/phosphatidylinositol phosphate 3 kinase (Akt/PtdIns3K). Using specific pharmacological inhibitors, our results show that activation of c-Jun N-terminal kinases and p38(MAPK.), but not STAT or Akt/PtdIns3K, pathways mediate the HNE-dependent up-regulation of BACE-1 expression. Therefore, HNE, an oxidative stress mediator detected in vivo in the brains of Alzheimer's disease patients, may play a pathogenetic role in Alzheimer's disease by selectively activating SAPK pathways and BACE-1 that regulate the proteolytic processing of AbetaPP.

4-Hydroxynonenal modulation of p53 family gene expression in the SK-N-BE neuroblastoma cell line.

4-Hydroxynonenal (HNE), a product of lipid peroxidation, inhibits proliferation of several tumor cells. The p53 tumor suppressor protein plays a critical role in cell cycle control, by inducing p21 expression, and in apoptosis, by inducing bax expression. Recently, two other proteins with many p53-like properties, TAp73 (p73) and TAp63 (p63), have been discovered. SK-N-BE human neuroblastoma cells express the three p53 family proteins and can be used for the study of their induction. We investigated HNE action in the control of proliferation, differentiation, and apoptosis in SK-N-BE cells and the HNE effect on the expression of p53, p63, p73, p21, bax, and G1 cyclins. Retinoic acid (RA) was used as a positive control. HNE inhibited cell proliferation without inducing differentiation; it decreased S-phase cells and increased the number of apoptotic cells. RA reduced the proportion of S-phase cells and did not induce apoptosis. HNE increased p53, p73, p63, p21, and bax expression at different time points. HNE reduced cyclin D2 expression and the phosphorylation of pRb protein. Our results demonstrated that HNE inhibits SK-N-BE cell proliferation by increasing the expression of p53 family proteins and p53 target proteins which modulate cell cycle progression and apoptosis.

Multiple signaling events in amyloid beta-induced, oxidative stress-dependent neuronal apoptosis.

Current evidence suggests that amyloid beta peptides (Abeta) may play a major role in the pathogenesis of Alzheimer's disease by eliciting oxidative stress and neuronal apoptosis. In this study we have used differentiated SK-N-BE neurons to investigate molecular mechanisms and regulatory pathways underlying apoptotic neuronal cell death elicited by Abeta(1-40) and Abeta(1-42) peptides as well as the relationships between apoptosis and oxidative stress. Abeta peptides, used at concentrations able to induce oxidative stress, elicit a classic type of neuronal apoptosis involving mitochondrial regulatory proteins and pathways (i.e. affecting Bax and Bcl-2 protein levels as well as release of cytochrome c in the cytosol), poly-ADP rybose polymerase cleavage and activation of caspase 3. This pattern of neuronal apoptosis, that is significantly prevented by alpha-tocopherol and N-acetylcysteine and completely abolished by specific inhibitors of stress-activated protein kinases (SAPK) such as JNKs and p38(MAPK), involved early elevation of p53 protein levels. Pretreatment of neurons with alpha-pifithrin, a specific p53 inhibitor, resulted in a 50-60% prevention of Abeta induced apoptosis. These results suggest that oxidative stress - mediated neuronal apoptosis induced by amyloid beta operates by eliciting a SAPK-dependent multiple regulation of pro-apoptotic mitochondrial pathways involving both p53 and bcl-2.

Oxidative stress increases expression and activity of BACE in NT2 neurons.

Recently an aspartyl protease with beta-secretase activity called BACE was identified. In the present paper we showed that BACE is modulated by the oxidative stress product 4-hydroxynonenal (HNE). Exposure of NT(2) neurons to the two classical pro-oxidant stimuli ascorbate/FeSO(4) and H(2)O(2)/FeSO(4) resulted in a significant generation of HNE, which is temporally followed by an increased production of BACE protein levels. HNE mediated BACE induction is accompanied by a proportional elevation of carboxy-terminal fragments of amyloid precursor protein. Moreover, the direct relationship between BACE induction and lipid peroxidation products was strongly confirmed by the protection exerted by a short pretreatment with alpha-tocopherol, the most important antioxidant known to prevent the formation of aldehydic end-products of lipid peroxidation, including HNE. Our results support the hypothesis that oxidative stress and A beta production are strictly interrelated events and suggest that inhibition of BACE may have a therapeutic effect synergic with antioxidant compounds.