In vivo and in vitro evaluation of 64 CU-labeled bombesin analogs for targeting gastrin-releasing peptide receptors on human prostate cancer [abstract]

Introduction: Gastrin-releasing peptide receptors (GRPr) are expressed in high numbers on human prostate cancer. The bombesin peptide derivative, BBN(7- 14)NH2, has high affinity and selectivity to GRPr. Therefore, Copper-64 (64Cu) radiolabeled bombesin conjugates could have potential in positron-emission tomography (PET) of human prostate cancer. Methods: In vitro assays of the NO2A bombesin conjugates and non-radioactive 63Cu-NO2A bombesin conjugates were performed in human PC-3 cells. In vivo pharmacokinetic studies of the radiolabeled 64Cu-NO2A bombesin conjugates were performed in normal CF-1 and PC-3 tumor-bearing SCID mice. In vivo, multimodal, molecular images were obtained of the radiolabeled 64Cu-NO2A bombesin conjugates in PC-3 tumor-bearing SCID mice via microPET/CT. Results: In vitro studies indicated idea uptake of the NO2A bombesin conjugates (1.99-6.24 nM), and 63Cu-NO2A bombesin conjugates (3.16-51.81 nM) in PC-3 cells. In vivo results of the 64Cu-NO2A bombesin conjugates at 1, 4, and 24 h p.i. showed affinity towards GRPr-positive tissue and effective clearance properties. Due to the favorable in vivo pharmacokinetic properties of 64Cu-NO2A bombesin conjugates, high-resolution multimodal, molecular imaging was performed via microPET/CT in aPC-3 tumor-bearing SCID mouse model. High-quality target to non-target images were obtained, with the tumors clearly visible. Conclusions: The 64Cu-NO2A bombesin conjugates showed affinity and specificity towards GRPr-positive tissues. High quality microPET images of PC-3 xenografted tumors in SCID mouse model were obtained, demonstrating the potential for PET imaging of GRPr-positive human prostate cancer tumors

Reduction of rheniumV oxo Schiff base complexes with triethylphosphine

Abstract only availablePioneering techniques for therapeutic treatment of cancers involve targeting cancer sites with strong beta-emitting radionuclides, thereby destroying the cancer cells. This is achieved by coordinating the radioisotope to a very chemically stable environment and linking it to a specific biologically active targeting molecule, which interacts with particular cancer cells. Radioactive isotopes of rhenium possess characteristics of such a nuclide. The focus of our research is to investigate two possible pathways for the reaction of [ReOX(Schiff base)] with phosphine ligands, one a mono-substituted ReV complex and one a di-substituted ReIII complex. The preferred ReIII complex is lower in oxidation state and more kinetically inert or stable relative to ReV. For practical applications it is necessary to have an extremely stable in vivo radionuclide complex which can be conjugated to a suitable biological targeting agent. The rigid sal2phen ligand, where Sal2phen is a tetradentate Schiff base ligand, was investigated to determine if the ReIII could be synthesized from the ReV starting complex [ReVOCl(Sal2phen)]. [ReVOCl(Sal2phen)] was reacted with triethylphosphine (PEt3) in attempts to yield the ReIII complex trans-[ReIII(PEt3)2(Sal2phen)][X]. Previous work indicated that the strongly reducing and strongly nucleophilic PEt3 might yield the ReV product from [ReVOCl(Sal2phen)]. The synthesized coordinated complex was reacted with an quaternary ammonium salt, ammonium hexaflurophosphate (NH4PF6), to induce crystallization of target compound [ReIII(PEt3)2(Sal2phen)][PF6]. Preliminary 1H-NMR, 31P-NMR, and infrared spectroscopy spectra indicate the formation of cis-[ReVO(PPh3)(Sal2phen)][X]. FTIR shows the presence of the Rhenium oxo group; 31P-NMR and 1H-NMR indicate the presence of ReV and a 1:1 PEt3 : Sal2phen complex. Single crystal x-ray diffraction, mass spectroscopy, and elemental analysis are additional methods of characterization.NSF-REU/NIH Program in Radiochemistr

Reduction of rhenium (V) oxo Schiff Base Complexes with triphenyl phosphine ligands

Abstract only availableOne approach to the treatment of cancer is to direct beta-emitting radionuclide to the cancer site where the radiation destroys the cancer cells. This can be achieved by coordinating the radioisotope in a very stable environment and linking it to a specific biological targeting molecule, which interacts specifically with particular cancer cells. It is necessary to have extremely stable in vivo radionuclide complexes so that limited amounts of radiation are released to other parts of the body before the radionuclide can reach the cancer cells. Isotopes of radioactive Rhenium are characteristic of such a nuclide. Our emphasis was to obtain a Rhenium (III) metal ligand complex since the lower oxidation state is more kinetically inert relative to Rhenium (V). The method employed was to first produce the ReV-ligand complex, [ReVOCl(Sal2phen)], by reacting a 1:2 molar ratio of TBA[ReVIIOCl4] to Sal2phen. Next, [ReVOCl(Sal2phen)] was reacted with three equivalents of triphenylphosphine to determine whether a mono-substituted ReV complex or a di-substituted ReIII complex was formed. After purifying the product by solvent extraction, the coordinated complex was reacted with ammonium hexaflurophoshate, NH4PF6, to induce crystallization of the target compound, [ReIII(PPh3)2(Sal2phen)][PF6]. Preliminary 1H NMR, and FT-IT spectra suggest formation of trans-[ReIII(PPh3)2(sal2phen)]PF6. The Re=O stretch at 951.36 cm-1 observed for [ReOCl(sal2phen)] in the IR spectrum is missing from our product, implying the Re (III) product has been formed.Stevens' Chemistry Progra

In vitro/in vivo assessment of novel 99mTc-bombesin conjugates in human cancer tissue [abstract]

Abstract only availableReceptor-specific, radiolabeled peptides are becoming increasingly popular as targeting vectors for the development of new diagnostic radiopharmaceuticals. The over-expression of certain receptors such as the gastrin releasing peptide receptor (GRPr) on human cancer cells makes this method of drug development a viable tool for tumor targeting in vivo. Breast, pancreatic, prostate, gastric, colon, and small-cell lung cancer have demonstrated GRPr expression. In this project, we have conjugated a diaminoproionic acid (DPR) bifunctional chelator to bombesin (BBN) peptide targeting vector by solid phase peptide synthesis. BBN is an analogue of human gastrin releasing peptide (GRP) that binds to the GRPr with high affinity and specificity. Conjugates of the general structure [DPR-(X)-BBN(7-14)NH2] (X = a series of amino acid pharmacokinetic modifiers) were purified by reverse-phase high-performance liquid chromatography and characterized by electrospray-ionization mass spectrometry. Radiolabeling investigations of with fac-[99mTc(CO)3(H2O)3]+ (Isolink®) provided for metallated conjugates of the following general structure: [99mTc(CO)3-DPR-(X)-BBN(7-14)NH2]. These new conjugates demonstrated the ability to target specific human tumors in rodent models. Subsequent radiolabeling studies of [DPR-(X)-BBN(7-14)NH2] with fac-[188Re(CO)3(H2O)3]+, the therapeutic surrogate precursor of Tc-99m, have given us the potential to treat specific human tumors via these new targeting vectors. Detailed radiolabeling protocols, in vitro cell binding studies, and in vivo biodistribution assays will be reported.Harry S. Truman Memorial VA Hospita

Radioactive materials: Winning the battle against cancer [abstract]

Abstract only availableFaculty Mentor: Dr. Silvia Jurisson, ChemistryRadiopharmaceuticals are drugs containing a radioactive atom that can be used for the treatment of certain cancers. The radiopharmaceuticals we are interested in consist of a radioactive source contained in a molecular cage and are directed to specific sites in the body via a targeting molecule. Rhenium (Re) is a useful radioactive source that can effectively kill surrounding cells with the energy it emits. It is important for the radioactive source to be secured in the molecular cage so that it will not irradiate unwanted parts of the body. A radiopharmaceutical that will more effectively irradiate the tumor may require fewer testaments, less overall discomfort, and will hopefully result in a lower cost for patients. The focus of this study was to design the cage that would effectively hold Re. Once Re was contained in the cage it was reacted with phosphine to increase its stability. Characterization methods were employed to insure that the structure had formed, but further characterization is needed. If determined stable, radioactive Re will be tested for stability in rat serum

Reducution of rhenium(V)-oxo schiff base complexesith triphenyl phosphine ligands [abstract]

Abstract only availableFaculty Mentor: Dr. Silvia Jurisson, ChemistryThe purpose of this research is to produce radiopharmaceutical drugs for the possible use in therapy and diagnosis of cancer. A radiopharmaceutical drug is composed of a radioactive element contained within chelating agent and linked to a biological targeting molecule. This can be achieved by complexing the radioisotope and conjugating the complex to a biologically active targeting molecule, such as a peptide antibody or antibody fragment. The biological targeting molecule directs radiation to specific peptides, antibodies and antibodies' fragments. The amount of dosage is limited to non-targeted tissue that occurs when free radionuclide is released from a decomposing molecule. Higher kinetic stability will maximize the localization of the radioisotope to the cancer sites and minimize the radiation dose to non-target tissues. This research was a continuation to seek the best pathway that would easily enable us to synthesize a kinetically inert metal complex [Re(Sal2Phen)] attached to a ligand. The rigid Rhenium(V)-oxo Schiff base complex is found in the following form: [ReO(Sal2Phen)Cl]. Initially salicylic aldehyde reacted with bis-2-phenlinediamine to get sal2phen. This tetradentate Schiff base ligand was reacted with TBA [ReOCl4] yielding [ReOCl(Sal2Phen)]. The reduction of Rhenium(V)-oxo core to Rhenium is obtained by reacting [ReO(Sal2Phen)Cl] with a triphenyl phosphine (PPh3) in dichloromethane and ethanol. Products obtained from this reaction were 1[Re(Sal2Phen)(PPh3)2], 2ReCl(Sal2Phen)PPh3, and 3[ReO(Sal2Phen)PPh3].Analysis of the major product were performed through crystals through mass spectrometry, hydrogen and phosphorus NMR, infrared spectra and x-ray crystallography

99mTc-DPR-SSS-BBN for diagnosis of human cancers [abstract]

Abstract only availableReceptor-specific, radiolabeled peptides have become increasingly popular as targeting vectors for the development of new diagnostic radiopharmaceuticals. The over-expression of certain receptors such as the gastrin releasing peptide receptor (GRPr) on human cancer cells makes this method of drug development a viable tool for tumor targeting in vivo. Breast, pancreatic, prostate, gastric, colon, and small-cell lung cancer have demonstrated GRPr expression. In this project, we have conjugated a diaminoproionic acid (DPR) bifunctional chelator to bombesin (BBN) peptide targeting vector by solid phase peptide synthesis. BBN is an analogue of human gastrin releasing peptide (GRP) that binds to the GRPr with high affinity and specificity. A conjugate, [DPR-SSS-BBN(7-14)NH] was purified by reverse-phase high-performance liquid chromatography and characterized by electrospray-ionization mass spectrometry. Radiolabeling investigations of with fac-[99mTc(CO)3(H2O)3]+ (Isolink®) provided for the metallated conjugate [99mTc(CO)3-DPR-SSS-BBN(7-14)NH2]. This new conjugate demonstrated the ability to target specific human tumors in rodent models. In vitro cell binding studies, and in vivo biodistribution assays will be reported.Life Sciences Undergraduate Research Opportunity Progra