Juan Pablo Gambini

In vivo imaging of astrocytosis in Alzheimer’s disease: an 11C-L-deuteriodeprenyl and PIB PET study

PurposeAstrocytosis is an important feature of the neuropathology of Alzheimer’s disease (AD), yet there is currently no way of detecting this phenomenon in vivo.MethodsIn this study we examine the retention of the positron emission tomography (PET) tracer 11C-L-deuteriodeprenyl (DED), thought to bind activated astrocytes, in 9 patients with moderate to severe AD compared with 11 healthy controls. As a measure of amyloid load, 11C-labelled Pittsburgh Compound B (PIB) retention was determined.ResultsResults show a significantly higher 11C-L-DED retention in the frontal (35.1% increase, p = 0.001), parietal (35.2%, p = 0.001), temporal (30.9%, p = 0.0001) and medial temporal lobes (22.3%, p = 0.001) in AD compared to healthy controls after blood flow correction. DED retention in the sensorimotor and occipital cortices, and in white matter and subcortical structures, did not differ between groups. There was a moderate but statistically significant (r = 0.492, p = 0.01) correlation between DED and PIB retention values.ConclusionOur conclusion is that DED may serve as an in vivo marker for astrocytosis in AD, providing a window into intermediate processes between amyloidosis and neuronal loss and a means of monitoring immunotherapy.

Evaluation of 99mTc-glucarate as a breast cancer imaging agent in a xenograft animal model.

INTRODUCTION The use of [(99m)Tc]glucarate has been reported as an infarct-avid agent with the potential for very early detection of myocardial infarction. [(99m)Tc]Glucarate has also been postulated as an agent for non-invasive detection of tumors. The aim of our study was to develop a Glucarate kit and evaluate [(99m)Tc]glucarate as a potential cancer imaging agent in female SCID mice bearing human MDA-MB-435 breast tumors. METHODS Glucarate in a kit formulation was labeled with (99m)Tc and evaluated for radiolabelling efficiency and radiochemical purity. The Glucarate kit stability was assessed by monthly quality controls. The pharmacokinetics of [(99m)Tc]glucarate were determined in female SCID mice bearing MDA-MB-435 human breast carcinoma tumors at 0.5, 1, 2, 4 and 24 h. Nuclear imaging studies were performed with a micro-single photon emission tomography (SPECT)/computed tomography (CT) system at 2 h post injection, while magnetic resonance imaging (MRI) was employed for tumor morphology analysis and metastatic deposit localization. RESULTS The Glucarate kits exhibited a stable shelf life of 6 months. [(99m)Tc]Glucarate was obtained with radiochemical purity greater than 95%. Biodistribution studies demonstrated moderate tumor uptake coupled with high renal clearance. Tumor-to-muscle ratios were 4.85 and 5.14 at 1 and 4 h post injection. MRI analysis showed tumors with dense cellular growth and moderate central necrosis. [(99m)Tc]Glucarate uptake in the primary MDA-MB-435 shoulder tumors and metastatic lesions were clearly visualized with micro-SPECT/CT imaging. CONCLUSIONS Selective tumor uptake and rapid clearance from nontarget organs makes [(99m)Tc]glucarate a potential agent for breast cancer imaging that awaits validation in a clinical trial.

[99mTc(CO)3]-Radiolabeled Bevacizumab: In vitro and in vivo Evaluation in a Melanoma Model

Introduction: Vascular endothelial growth factor (VEGF) is one of the classic factors to tumor-induced angiogenesis in several tumor types, including melanoma. Bevacizumab, a monoclonal antibody against VEGF, could be used as an imaging tool in preclinical studies. Objective: To radiolabel bevacizumab with [^99mTc(CO)₃(OH₂)₃]⁺ and evaluate it in vivo and in vitro for melanoma imaging properties. Methods: Bevacizumab was radiolabeled with [^99mTc(CO)₃(OH₂)₃]⁺ ion in saline. The radiochemical stability of the labeled antibody was assessed. The biodistribution and scintigraphy imaging of the radiolabeled antibody were evaluated in normal C57BL/6J mice and in C57BL/6J mice bearing murine B16F1 melanoma tumors. Immunoreactivity of bevacizumab to murine tumors was determined from direct immunofluorescence and immunoblotting assays. Results: We demonstrate that ^99mTc(CO)₃-bevacizumab was stable. In vivo biodistribution studies revealed that tumor uptake of ^99mTc(CO)₃-bevacizumab was 2.64 and 2.51 %ID/g at 4 and 24 h postinjection. Scintigraphy image studies showed tumor selective uptake of ^99mTc(CO)₃-bevacizumab in the tumor-bearing mice. This affinity was confirmed by immunoassays performed on B16F10 tumor samples. Conclusions:^99mTc(CO)₃-bevacizumab could be used as an approach for tumor nuclear imaging in preclinical studies. This should be useful to provide insights into the angiogenic stimulus before and after chemotherapy, which might help improve current antitumor therapy.

Development of 99mTc(CO)3-dendrimer-FITC for cancer imaging

Study of fluorophore and technetium labeling of poly(amido)-amine (PAMAM) generation 4 (G4) dendrimer and its evaluation as potential molecular imaging agent in both normal and melanoma-bearing mice, are described. Dendrimers were first conjugated with FITC (fluorescein isothiocyanate). Dendrimer-FITC was then incubated with the intermediate [(99m)Tc(CO)(3)(H(2)O)(3)](+) and purified by gel filtration. Biodistribution and scintigraphy images were performed administrating (99m)Tc(CO)(3)-dendrimer-FITC to normal mice (NM) or melanoma-bearing mice (MBM). Cryostat tissue sections from MBM mice were analyzed by confocal microscopy. Radiolabeling yield of dendrimer was approx. 90%. The (99m)Tc(CO)(3)-dendrimer-FITC complex was stable for at least 24h. Biodistribution studies in NM showed blood clearance with hepatic and renal depuration. MBM showed a similar pattern of biodistribution with high tumor uptake that allowed tumor imaging. Confocal microscopy analysis showed cytoplasmic distribution of (99m)Tc(CO)(3)-dendrimer-FITC.

Biological evaluation of glucose and deoxyglucose derivatives radiolabeled with [99mTc(CO)3(H2O)3]+ core as potential melanoma imaging agents.

Glucose 9 and 2-deoxyglucose 10 were successfully synthesized and radiolabeled with [(99m)Tc(CO)(3)(H(2)0)(3)](+) intermediate in high yield. The complexes were characterized by HPLC and its stability with histidine over time was challenged. Cell uptake and biodistribution studies in melanoma-bearing C57BL/6 mice were performed. Both compounds showed accumulation in tumor tissue with high tumor-to-muscle ratios. Thus, D-glucose- and D-2-deoxyglucose-(99m)Tc complex could be considered as agents for melanoma diagnosis.

99mTc-HYNIC octreotide in neuroblastoma

Disease status assessment of neuroblastoma patients requires computed tomography (or magnetic resonance imaging), bone scan, metaiodobenzylguanidine (MIBG) scan, bone marrow tests, and urine catecholamine measurements. There is no clinical experience concerning the evaluation of these patients by means of technetium-99m (99mTc)-somatostatin analog scintigraphy. Furthermore, these radiopharmaceuticals are promising imaging agents owing to their lower cost, availability, dosimetry, and ease of preparation. An 8-year-old boy already diagnosed with stage-IV neuroblastoma received chemotherapy. In the follow-up, after obtaining the parents’ informed consent, iodin 131 (131I)-MIBG and 99mTc-6-hydrazinopyridine-3-carboxylic acid (HYNIC)-octreotide scans were done on separate days to evaluate tumor extension. Even as the 131I-IBG scan showed mild diffuse uptake in the projection of both lung hili, the 99mTc-HYNIC-octreotide scan showed multiple axial and appendicular bone uptakes and paravertebral, abdominal, mediastinal, and supraclavicular ganglionar uptakes. The 99mTc-HYNIC-octreotide showed much more lesion extension than the 131I-MIBG. Therefore, 99mTc-HYNIC-octreotide may be a promising radiopharmaceutical for the evaluation of neuroblastoma patients. This finding justifies the pre liminary evaluation of this tracer in the context of a clinical trial.

Labeling and Biological Evaluation of 99m Tc-HYNIC-Trastuzumab as a Potential Radiopharmaceutical for In Vivo Evaluation of HER2 Expression in Breast Cancer

The amplification of HER2 gene has been described in several tumor types, mainly breast cancer with a subsequent increase in HER2 protein expression. Trastuzumab is a humanized monoclonal antibody that recognizes selectively the HER2 extracellular domain. The objective of the present work was to standardize the conjugation of Trastuzumab with Succinimidyl-hydrazinonicotinamide (HYNIC) and labeling with 99mTc to obtain 99mTc-HYNIC-Trastuzumab for use as in vivo tracer of the HER2 expression in breast cancer. The labeling procedure involved derivatization of 0.067 μmol of Trastuzumab with 0.33 μmols of HYNIC in dimethyl sulfoxide (DMSO). The mixture was incubated for 30 min. A mixture of Tricine and SnCl2.2H2O was prepared by add a solution of 44.6 μmols Tricine in 0.05 mL HCl 2.0 M and a similar volume of another solution containing 44.3 μmols SnCl2.2H2O in 0.5 mL HCl 2.0 M. Then, 0.05 mL of this mixed was added to the conjugated with 296 MBq of 99mTcO-4. The final mixture was incubated at room temperature (18-25°C) for 30 min. Radiochemical purity of the labeled solution was studied by chromatography, to evaluate 99mTc-Tricine, 99mTcO2.H2O, and free 99mTcO4−. Radiochemical purity was also evaluated by HPLC. Stability studies were tested in solution at 4°C and lyophilized at 4°C. Biodistribution studies were performed in healthy CD-1 female mice at 2, 5, and 24 h (n = 3) and CD-1 female mice spontaneous breast adenocarcinoma (n = 3). Scintigraphic images of spontaneous breast adenocarcinoma in female CD-1 mice were acquired in a gamma camera at 2, 5, and 24 h post-injection. Labeling was easily performed with high yields (>90%) and radiopharmaceutical stability for 24 h post-labeling. Stability studies revealed that antibody derivative must be lyophilized for undamaged storage. Biodistribution studies and imaging revealed excellent uptake in the tumor. Based on the results it was concluded that 99mTc-HYNIC-Trastuzumab could be a promising radiopharmaceutical for in vivo diagnosis of the HER2 status in breast with impact on treatment planning.

In vivo visualization of somatostatin receptor expression with Ga-68-DOTA-TATE PET/CT in advanced metastatic prostate cancer.

Abstract:Recently, combination therapies with somatostatin analogs have emerged as a therapeutic option for patients with androgen-independent advanced prostate cancer. Therefore, the confirmation of a sufficient number of somatostatin receptors to plan a receptor-targeted chemo- or radiation therap

Evaluation of Tricine and EDDA as Co-ligands for 99m Tc-Labeled HYNIC-MSH Analogs for Melanoma Imaging

Several radiolabeled alpha-melanocyte stimulating hormone (α-MSH) analogs have been studied for their abilities to target melanoma tumor cells through specific recognition and binding to the melanocortin receptor 1 (MCR1). In this work, a lactam bridgecyclized α-MSH analog was labeled with (99m) via the hydrazinonicotinamide (HYNIC) chelator and characterized for its melanoma tumor targeting properties. The bifunctional chelating agent HYNIC-Boc was attached to the N-terminus of the MSH peptide followed by the lactam cyclization, resulting in the HYNIC-cyc-MSH analog. The lactam cyclized peptide displayed high affinity and specificity for MC1-receptors present on B16/F1 melanoma tumor cells, exhibiting an IC50 of 6.48 nM. HYNIC-cyc-MSH was radiolabeled with (99m)Tc using two common co-ligands, tricine and EDDA. In vitro, the radiochemical stability, cell binding and efflux properties were similar between the peptides radiolabeled with tricine and EDDA as co-ligands. In vivo, biodistribution studies (n=4) demonstrated that (99m)Tc- HYNIC-cyc-MSH/tricine had superior tumor to muscle and tumor to blood ratios than (99m)Tc-HYNIC-cyc-MSH/EDDA at early time points. Planar gamma imaging of melanoma bearing mice showed that 99mTc-HYNIC-cyc-MSH/tricine was able to clearly visualize tumors, underscoring the potential utility of (99m)Tc labeled lactam cyclized MSH molecules as melanoma imaging agents.

Hybrid tracers and devices for intraoperative imaging: the future for radioguided surgery?

Radioguided surgery (RS) allows surgeons to identify tissues of interest that were preoperatively or intraoperatively marked with radiotracers. This discipline has seen major changes related to the development of new tracers, instrumentation and software. The goal of this review is to comment on current development and perspectives in the RS field. The review is based on published papers that highlight the role of RS and explore current advances such as the Guided intraOperative Scintigraphic Tumour Targeting (GOSTT) concept, which established the see, open and see strategy and propose a new one, Guided Hybrid intraOperative Specific Targeting (GHOST). We examine the development of radioactive, fluorescent and hybrid tracers and corresponding instrumentation and software to detect them and suggest ways in which these developments could be integrated. The role of hybrid tracers in RS, in particular 99mTc nanocolloid indocyanine green on sentinel node procedures, is highlighted. Labeled specific targeted peptides, antibodies and nanostructures will allow better preoperative diagnosis and intraoperative localization of tissue of interest. Photodynamic therapy could be applied during surgery to eliminate residual tumoral tissue. In the follow up, patients could be considered for treatment with targeted radiotherapy. RS has moved from open surgery to laparoscopic and robotic surgery. In each of them it is possible to add fluorescent, radioactive and hybrid modules able to detect labeled tissue of interest, while preserving healthy ones. As we have seen, RS is advancing through an interdisciplinary collaboration that will provide surgeons with new tools to improve surgical outcomes.