Labeling of phosphorothioate antisense oligonucleotides with yttrium-90

Preparation and evaluation of APTES-PEG coated iron oxide nanoparticles conjugated to rhenium-188 labeled rituximab

Radioimmuno-conjugated (Rhenium-188 labeled Rituximab), 3-aminopropyltriethoxysilane (APTES)-polyethylene glycol (PEG) coated iron oxide nanoparticles were synthesized and then characterized. Therapeutic effect and targeting efficacy of complex were evaluated in CD20 express B cell lines and tumor bearing Balb/c mice respectively. To reach these purposes, superparamagnetic iron oxide nanoparticles (SPIONs) were synthesized using coprecipitation method and then their surface was treated with APTES for increasing retention time of SPIONs in blood circulation and amine group creation. In the next step, N-hydroxysuccinimide (NHS) ester of polyethylene glycol maleimide (NHS-PEG-Mal) was conjugated to the APTES-treated SPIONs. After radiolabeling of Rituximab antibody with Rhenium-188 (T_1/2=16.9h) using synthesized N₂S₄ chelator, it was attached to the APTES-PEG-MAL-SPIONs surface through thiol-maleimide coupling reaction. In vitro evaluation of the ¹⁸⁸ReN₂S₄-Rituximab-SPION-complex thus obtained revealed that at 24 and 48h post-treatment effective cancer cell killing had been achieved. Bio-distribution study in tumor bearing mice showed capability of this complex for targeted cancer therapy. Active and passive tumor targeting strategies were applied through incorporated anti-CD20 (Rituximab) antibody and also enhanced permeability and retention (EPR) effect of solid tumors for nanoparticles respectively.

PET and SPECT

Assessment of gene function following the completion of human genome sequencing may be done using radionuclide imaging procedures. These procedures are needed for the evaluation of genetically manipulated animals or newly designed biomolecules which require a thorough understanding of physiology, biochemistry and pharmacology. The experimental approaches will involve many new technologies, including in-vivo imaging with SPECT and PET. Nuclear medicine procedures may be applied for the determination of gene function and regulation using established and new tracers or using in-vivo reporter genes, such as genes encoding enzymes, receptors, antigens or transporters. Visualization of in-vivo reporter gene expression can be done using radiolabeled substrates, antibodies or ligands. Combinations of specific promoters and in-vivo reporter genes may deliver information about the regulation of the corresponding genes. Furthermore, protein-protein interactions and the activation of signal transduction pathways may be visualized noninvasively. The role of radiolabeled antisense molecules for the analysis of mRNA content has to be investigated. However, possible applications are therapeutic interventions using triplex oligonucleotides with therapeutic isotopes, which can be brought near to specific DNA sequences to induce DNA strand breaks at selected loci. After the identification of new genes, functional information is required to investigate the role of these genes in living organisms. This can be done by analysis of gene expression, protein-protein interaction or the biodistribution of new molecules and may result in new diagnostic and therapeutic procedures, which include visualization of and interference with gene transcription, and the development of new biomolecules to be used for diagnosis and treatment. Furthermore, the characterization of tumor cell-specific properties allows the design of new treatment modalities, such as gene therapy, which circumvent resistance mechanisms towards conventional chemotherapeutic drugs.

Modulation of tracer accumulation in malignant tumors: gene expression, gene transfer, and phage display

Assessment of gene function following the completion of human genome sequencing may be done using radionuclide imaging procedures. These procedures are needed for the evaluation of genetically manipulated animals or new designed biomolecules which requires a thorough understanding of physiology, biochemistry and pharmacology. The experimental approaches will involve many new technologies including in vivo imaging with SPECT and PET. Nuclear medicine procedures may be applied for the determination of gene function and regulation using established and new tracers or using in vivo reporter genes such as genes encoding enzymes, receptors, antigens or transporters. Visualization of in vivo reporter gene expression can be done using radiolabeled substrates, antibodies or ligands. Combinations of specific promoters and in vivo reporter genes may deliver information about the regulation of the corresponding genes. Furthermore, protein-protein interactions and activation of signal transduction pathways may be visualized non-invasively. The role of radiolabeled antisense molecules for the analysis of mRNA content has to be investigated. However, possible applications are therapeutic intervention using triplex oligonucleotides with therapeutic isotopes which can be brought near to specific DNA sequences to induce DNA strand breaks at selected loci. Imaging of labeled siRNA's makes sense if these are used for therapeutic purposes in order to assess the delivery of these new drugs to their target tissue. Finally, new biomolecules will be developed by bioengineering methods which may be used for isotope-based diagnosis and treatment of disease.

An 86Y-labeled mirror-image oligonucleotide: influence of Y-DOTA isomers on the biodistribution in rats

A mirror-image oligonucleotide (L-RNA) was radiolabeled with the positron emitting radionuclide (86)Y (t(1/2) = 14.7 h) via the bifunctional chelator approach. DOTA-modification of the L-RNA (sequence: 5'-aminohexyl UGA CUG ACU GAC-3'; MW 3975) was performed using (S)-p-SCN-Bn-DOTA. (86)Y radiolabeling of the DOTA-L-RNA produced more than one species as evidenced by HPLC radiometric detection. For the identification of the (86)Y-labeled L-RNA, the structural analogue nonradioactive precursor [Y((S)-p-NH2-Bn-DOTA)](-) was synthesized. Two coordination isomers were separated via HPLC adopting the square antiprismatic (SAP) and the twisted square antiprismatic (TSAP) geometry, respectively. Their stereochemical configuration in the solution state was assessed by NMR and circular dichroism spectroscopy. Both [Y((S)-p-NH2-Bn-DOTA)](-) isomers were converted into isothiocyanate derivatives [Y((S)-p-SCN-Bn-DOTA)](-) and conjugated to the L-RNA. The identity of the [(86)Y-DOTA]-L-RNA species was finally established by comparison of the radiometric ((86)Y) and UV-visible chromatographic profiles. Biodistribution studies in Wistar rats showed minor changes in the biodistribution profile of the [(86)Y((S)-p-NH2-Bn-DOTA)](-) complex isomers, while no significant differences were observed for the [(86)Y-DOTA]-L-RNA isomers. High renal excretions were found for the [(86)Y((S)-p-NH 2-Bn-DOTA)](-) complex isomers as well as for the L-RNA isomers.

Antitumor effects of radioiodinated antisense oligonuclide mediated by VIP receptor

A 15-mer phosphorothioate antisense oligonuclide (ASON) complementary to the translation start region of the C-myc oncogene mRNA was radioiodinated to enhance its antitumor activity, and vasoactive intestinal peptide bound covalently polylysine (VIP-polylysine) was used as a carrier to deliver the oligonucleotide into VIP receptor-positive tumor cells. The antitumor activity of radioiodinated ASON conjugated to VIP-polylysine(VIP-131I-ASON) was investigated in athymic mice bearing HT29 tumor xenografts in comparison with unconjugated radioiodinated ASON(131I-ASON), unlabelled ASON (VIP-ASON) and scrambled oligonucleotide (VIP-131I-MON) conjugated to VIP-polylysine. Conjugation 125I-ASON to VIP-polylysine resulted in a 5.6-fold decrease in the plasma clearance and a 3.4-fold increase in tumor uptake of the radiopharmaceutical. Athymic mice bearing HT29 tumor xenografts were treated with 4 weekly doses of VIP-131I-ASON and the antitumor effects were assessed by use of the slope of the tumor growth curve. VIP-131I-ASON exhibited strong antitumor effects against HT29 xenografts, decreasing tumor growth rate 9.67-, 7.90-fold more effectively than 131I-ASON and VIP-ASON at equivalent doses of ASON. Conversely, 131I-ASON, VIP-ASON or VIP-131I-MON caused no significant effect compared with the normal saline. These data indicated that use of a VIP-polylysine carrier greatly increased HT29 tumor uptake of ASON and treatment with the VIP-131I-ASON complexes resulted in tumor growth delay in human colon cancer xenograft.

Impact of functional genomics and proteomics on radionuclide imaging

The assessment of gene function following the completion of human genome sequencing may be performed using radionuclide imaging procedures. These procedures are needed for the evaluation of genetically manipulated animals or newly designed biomolecules, which requires a thorough understanding of physiology, biochemistry, and pharmacology. The experimental approaches will involve many new technologies, including in vivo imaging with single photon emission computed tomography and positron emission tomography. Nuclear medicine procedures may be applied for the determination of gene function and regulation using established and new tracers, or using in vivo reporter genes, such as genes encoding enzymes, receptors, antigens, or transporters. Visualization of in vivo reporter gene expression can be performed using radiolabeled substrates, antibodies, or ligands. Combinations of specific promoters and in vivo reporter genes may deliver information about the regulation of the corresponding genes. Furthermore, protein-protein interactions and activation of signal transduction pathways may be visualized noninvasively. The role of radiolabeled antisense molecules for the analysis of messenger ribonucleic acid (RNA) content has to be investigated. However, possible applications are therapeutic intervention using triplex oligonucleotides with therapeutic isotopes, which can be brought near to specific deoxyribonucleic acid sequences to induce deoxyribonucleic acid strand breaks at selected loci. Imaging of labeled siRNA makes sense if these are used for therapeutic purposes to assess the delivery of these new drugs to their target tissue. Pharmacogenomics will identify new surrogate markers for therapy monitoring, which may represent potential new tracers for imaging. Drug distribution studies for new therapeutic biomolecules are needed at least during preclinical stages of drug development. New treatment modalities, such as gene therapy with suicide genes, will need procedures for therapy planning and monitoring. Finally, new biomolecules will be developed by bioengineering methods, which may be used for the isotope-based diagnosis and treatment of disease.

Radionuclide imaging in the post-genomic era

The assessment of gene function, which follows the completion of human genome sequencing, may be performed using the tools of the genome program. These tools represent high-throughput methods evaluating changes in the expression of many or all genes of an organism at the same time in order to investigate genetic pathways for normal development and disease. They describe proteins on a proteome-wide scale, thereby, creating a new way of doing cell research which results in the determination of three dimensional protein structures and the description of protein networks. These descriptions may then be used for the design of new hypotheses and experiments in the traditional physiological, biochemical, and pharmacological sense. The evaluation of genetically manipulated animals or new designed biomolecules will require a thorough understanding of physiology, biochemistry, and pharmacology and the experimental approaches will involve many new technologies including in vivo imaging with SPECT and positron emission tomography (PET). Nuclear medicine procedures may be applied for the determination of gene function and regulation using established and new tracers or using in vivo reporter genes such as genes encoding enzymes, receptors, antigens, or transporters. Pharmacogenomics will identify new surrogate markers for therapy monitoring which may represent potential new tracers for imaging. Also drug distribution studies for new therapeutic biomolecules are needed at least during preclinical stages of drug development. Finally, new biomolecules will be developed by bioengineering methods, which may be used for isotope-based diagnosis and treatment of disease.

Radiolabeling morpholinos with 90Y, 111In, 188Re and 99mTc

This laboratory is investigating morpholinos (MORF), a DNA analogue, for radiopharmaceutical applications. While we routinely radiolabel with (99m)Tc, we have now labeled MORFs with (111)In, (188)Re and (90)Y in anticipation of therapeutic studies.

METHODS

A 25 mer MORF with a primary amine on the 3' equivalent end attached via a 10 member linker was conjugated with an isothiocyanate backbone derivative of DOTA (for labeling with (111)In and (90)Y) and with NHS-MAG(3) (for labeling with (188)Re and (99m)Tc). The in vitro stability of labeled MORFs were investigated and biodistribution was carried out in normal mice.

RESULTS

As evident by size exclusion HPLC, ITLC and Sep-Pak analysis, all four radiolabeled MORFs were successfully radiolabeled. In each case, the labeled MORFs showed one sharp peak in HPLC that shifted completely to earlier retention times following addition of a polymer conjugated with the complementary MORF. In saline at room temperature and in 37 degrees C serum, the radioactivity profile of (111)In, (188)Re and (99m)Tc was unchanged over 48 h while over the same period, the (90)Y profile showed a pronounced lower molecular weight peak which did not shift and was shown to be most probably due to (90)Y-DOTA resulting from radiolysis. In addition, the recovery of (188)Re on HPLC decreased as samples aged probably due to oxidation to perrhenate which was retained by the HPLC column. The biodistributions at 1, 3 and 6 h in normal mice showed no important differences among all four labels with the exception that levels of radioactivity in stomach and thyroid were higher in the case of (188)Re due to in vivo oxidation of the radiolabel to perrhenate.

CONCLUSIONS

When radiolabeled with DOTA, (90)Y-labeled MORF showed increased instabilities relative to that of (111)In and when radiolabeled with MAG(3), (188)Re showed in vitro and in vivo instabilities compared to (99m)Tc, but all labels were still largely intact after 48 h in saline or serum. Possibly because of the rapid clearance of MORFs, no important differences in biodistribution among (90)Y, (111)In and (99m)Tc labels were evident in normal mice. These strategies for labeling MORF with (90)Y and (188)Re therefore appear to be suitable for therapeutic applications although both show some evidence of instabilities.

Functional genomics and radioisotope-based imaging procedures

After the sequencing of the human genome has been completed, non-invasive imaging studies are needed to assess the function of new genes in living organisms. The evaluation of genetically manipulated animals or new designed biomolecules will require a thorough understanding of physiology, biochemistry and pharmacology, and the experimental approaches will involve many new technologies including in vivo imaging with single photon emission computed tomography (SPECT) and positron emission tomography (PET). Nuclear medicine procedures may be applied for the determination of gene function and regulation using established and new tracers or using in vivo reporter genes such as enzymes, receptors, antigens or transporters. Pharmacogenomics will identify new surrogate markers for therapy monitoring which may represent potential new tracers for imaging. Also, drug distribution studies for new therapeutic biomolecules are needed at least during preclinical stages of drug development. Clinical gene therapy needs non-invasive tools to evaluate the efficiency of gene transfer. These informations can be used for therapy planning, follow-up studies in treated tumors and as an indicator of prognosis. Therapy planning is performed by the assessment of gene expression for example using radio-labeled specific substrates to determine the activity of suicide enzymes such as the Herpes Simplex Virus thymidine kinase. Follow-up studies with single photon emission tomography or positron emission tomography may be done to evaluate early or late effects of gene therapy on tumor metabolism or proliferation. Finally, new biomolecules will be developed by bioengineering methods which may be used for isotope-based diagnosis and treatment of disease.

Cherenkov counting of yttrium-90 in the dry state; correlations with phosphorus-32 Cherenkov counting data

We present data that illustrate some advantages of Cherenkov counting for the radioassay of 90Y in the dry state and provide recommendations concerning sample counting geometry. Slightly higher detection efficiencies and figures-of-merit were obtained when counting 90Y in the dry state in polyethylene plastic counting vials compared to the counting of 90Y in 20 ml of water in borosilicate glass vials. The effects of polyethylene plastic counting vials and sample counting geometry are compared to similar data obtained in the Cherenkov counting of 32P. Data are presented to interpret the effects of polyethylene plastic and borosilicate glass on Cherenkov counting efficiency and background counts. Applications of the Cherenkov counting of 90Y and 32P in the dry state in the biological and radiopharmaceutical sciences are foreseen as well as applications in the analysis of 90Sr(90Y) and 32P in health physics and environmental monitoring.