RESUMO
Pancreatic islet transplantation can be a more permanent treatment for type 1 diabetes compared to daily insulin administration. Quantitative and longitudinal noninvasive imaging of viable transplanted islets might help to further improve this novel therapy. Since islets express dopamine 2 (D2) receptors, they could be visualized by targeting this receptor. Therefore, the D2 receptor antagonist based tracer [(125/123)I][IBZM] was selected to visualize transplanted islets in a rat model. BZM was radioiodinated, and the labeling was optimized for position 3 of the aromatic ring. [(125)I]-3-IBZM was characterized in vitro using INS-1 cells and isolated islets. Subsequently, 1,000 islets were transplanted in the calf muscle of WAG/Rij rats and SPECT/CT images were acquired 6 weeks after transplantation. Finally, the graft containing muscle was dissected and analyzed immunohistochemically. Oxidative radioiodination resulted in 3 IBZM isomers with different receptor affinities. The use of 0.6 mg/mL chloramine-T hydrate resulted in high yield formation of predominantly [(125)I]-3-IBZM, the isomer harboring the highest receptor affinity. The tracer showed D2 receptor mediated binding to isolated islets in vitro. The transplant could be visualized by SPECT 6 weeks after transplantation. The transplants could be localized in the calf muscle and showed insulin and glucagon expression, indicating targeting of viable and functional islets in the transplant. Radioiodination was optimized to produce high yields of [(125)I]-3-IBZM, the isomer showing optimal D2R binding. Furthermore, [(123)I]IBZM specifically targets the D2 receptors on transplanted islets. In conclusion, this tracer shows potential for noninvasive in vivo detection of islets grafted in the muscle by D2 receptor targeting.
Assuntos
Radioisótopos do Iodo/química , Ilhotas Pancreáticas/metabolismo , Receptores Dopaminérgicos/química , Tomografia Computadorizada de Emissão de Fóton Único/métodos , Animais , Benzamidas/química , Transplante das Ilhotas Pancreáticas , Masculino , Pirrolidinas/química , RatosRESUMO
Prostate cancer (PCa) is the most common malignancy in men worldwide, leading to substantial morbidity and mortality. At present, imaging of PCa has become increasingly important for staging, restaging, and treatment selection. Until recently, choline-based positron emission tomography/computed tomography (PET/CT) represented the state-of-the-art radionuclide imaging technique for these purposes. However, its application is limited to patients with high PSA levels and Gleason scores. Prostate-specific membrane antigen (PSMA) is a promising new target for specific imaging of PCa, because it is upregulated in the majority of PCa. Moreover, PSMA can serve as a target for therapeutic applications. Currently, several small-molecule PSMA ligands with excellent in vivo tumor targeting characteristics are being investigated for their potential in theranostic applications in PCa. Here, a review of the recent developments in PSMA-based diagnostic imaging and therapy in patients with PCa with radiolabeled PSMA ligands is provided.
Assuntos
Antígenos de Superfície/análise , Antígenos de Superfície/metabolismo , Glutamato Carboxipeptidase II/análise , Glutamato Carboxipeptidase II/metabolismo , Ligantes , Neoplasias da Próstata/diagnóstico , Neoplasias da Próstata/radioterapia , Cintilografia/métodos , Radioterapia/métodos , Humanos , Masculino , Ligação ProteicaRESUMO
Glycosaminoglycan (GAG) polysaccharides have been implicated in a variety of cellular processes, and alterations in their amount and structure have been associated with diseases such as cancer. In this study, we probed 11 sugar analogs for their capacity to interfere with GAG biosynthesis. One analog, with a modification not directly involved in the glycosidic bond formation, 6F-N-acetyl-d-galactosamine (GalNAc) (Ac3), was selected for further study on its metabolic and biologic effect. Treatment of human ovarian carcinoma cells with 50 µM 6F-GalNAc (Ac3) inhibited biosynthesis of GAGs (chondroitin/dermatan sulfate by â¼50-60%, heparan sulfate by â¼35%), N-acetyl-d-glucosamine (GlcNAc)/GalNAc containing glycans recognized by the lectins Datura stramonium and peanut agglutinin (by â¼74 and â¼43%, respectively), and O-GlcNAc protein modification. With respect to function, 6F-GalNAc (Ac3) treatment inhibited growth factor signaling and reduced in vivo angiogenesis by â¼33%. Although the analog was readily transformed in cells into the uridine 5'-diphosphate (UDP)-activated form, it was not incorporated into GAGs. Rather, it strongly reduced cellular UDP-GalNAc and UDP-GlcNAc pools. Together with data from the literature, these findings indicate that nucleotide sugar depletion without incorporation is a common mechanism of sugar analogs for inhibiting GAG/glycan biosynthesis.
Assuntos
Acetilgalactosamina/análogos & derivados , Glicosaminoglicanos/biossíntese , Acetilgalactosamina/química , Acetilgalactosamina/farmacologia , Animais , Linhagem Celular , Embrião de Galinha , Fator 2 de Crescimento de Fibroblastos/metabolismo , Glicosaminoglicanos/antagonistas & inibidores , Células HeLa , Células Endoteliais da Veia Umbilical Humana , Humanos , Neovascularização Fisiológica/efeitos dos fármacos , Polissacarídeos/antagonistas & inibidores , Polissacarídeos/biossíntese , Transdução de Sinais/efeitos dos fármacos , Relação Estrutura-Atividade , Uridina Difosfato N-Acetilgalactosamina/metabolismo , Uridina Difosfato N-Acetilglicosamina/metabolismo , Fator A de Crescimento do Endotélio Vascular/metabolismoRESUMO
Heparan sulfate (HS), a long linear polysaccharide, is implicated in various steps of tumorigenesis, including angiogenesis. We successfully interfered with HS biosynthesis using a peracetylated 4-deoxy analogue of the HS constituent GlcNAc and studied the compound's metabolic fate and its effect on angiogenesis. The 4-deoxy analogue was activated intracellularly into UDP-4-deoxy-GlcNAc, and HS expression was inhibited up to â¼96% (IC50 = 16 µM). HS chain size was reduced, without detectable incorporation of the 4-deoxy analogue, likely due to reduced levels of UDP-GlcNAc and/or inhibition of glycosyltransferase activity. Comprehensive gene expression analysis revealed reduced expression of genes regulated by HS binding growth factors such as FGF-2 and VEGF. Cellular binding and signaling of these angiogenic factors was inhibited. Microinjection in zebrafish embryos strongly reduced HS biosynthesis, and angiogenesis was inhibited in both zebrafish and chicken model systems. All of these data identify 4-deoxy-GlcNAc as a potent inhibitor of HS synthesis, which hampers pro-angiogenic signaling and neo-vessel formation.
Assuntos
Regulação da Expressão Gênica/efeitos dos fármacos , Heparitina Sulfato/genética , Neovascularização Patológica/fisiopatologia , Uridina Difosfato N-Acetilglicosamina/análogos & derivados , Uridina Difosfato N-Acetilglicosamina/farmacologia , Animais , Galinhas , Regulação para Baixo/efeitos dos fármacos , Embrião não Mamífero/efeitos dos fármacos , Fator 2 de Crescimento de Fibroblastos/genética , Heparitina Sulfato/biossíntese , Heparitina Sulfato/metabolismo , Ácido Idurônico/química , Transdução de Sinais/efeitos dos fármacos , Uridina Difosfato N-Acetilglicosamina/química , Uridina Difosfato N-Acetilglicosamina/metabolismo , Fator A de Crescimento do Endotélio Vascular/genética , Peixe-ZebraRESUMO
A novel approach to a formal total synthesis of the monoterpenoid indole alkaloid (±)-tangutorine has been developed starting from an α,ß-unsaturated cyclic dehydroamino ester. Synthesis of the rather unusual trans-substituted 2,3-indoloquinolizidine substructure was accomplished via Cu(II)-mediated conjugate addition and organozinc/copper coupling as the key steps, thereby setting the stage for ring-closing metathesis to produce the quinolone substructure. Finally, Bischler-Napieralski cyclization gave rise to the pentacyclic system of (±)-tangutorine thereby realizing a formal synthesis in an overall yield of 5.2% in eight consecutive steps.
Assuntos
Alcaloides/síntese química , Carbolinas/síntese química , Monoterpenos/síntese química , Quinolizinas/síntese química , Cobre/química , Ciclização , EstereoisomerismoRESUMO
Heparan sulphate (HS) is a long, linear polysaccharide, which has a basic backbone of -beta1-4GlcA-alpha1-4GlcNAc- units. The involvement of HS in many steps of tumourigenesis, including growth and angiogenesis, makes it an appealing target for cancer therapy. To target the biosynthesis of HS by interfering with its chain elongation, a 4-deoxy analogue of N-acetyl-D-glucosamine (4-deoxy-GlcNAc) was synthesized. Using immunocytochemistry and agarose gel electrophoresis it was shown that incubation with the 4-deoxysugar resulted in a dose dependent reduction of HS expression of MV3 melanoma cells, 1 mM resulting in an almost nullified HS expression. The parent sugar GlcNAc had no effect. 4-deoxysugar treated cells were viable and proliferated at the same rate as control cells. Other glycan structures appeared to be only mildly affected, as staining by various lectins was generally not or only modestly inhibited. At 1 mM of the 4-deoxysugar, the capacity of cells to bind the HS-dependent pro-angiogenic growth factors FGF-2 and VEGF was greatly compromised. Using an in vitro angiogenesis assay, 4-deoxysugar treated endothelial cells showed a sharp reduction of FGF-2-induced sprout formation. Combined, these data indicate that an inexpensive, easily synthesized, water-soluble monosaccharide analogue can interfere with HS expression and pro-angiogenic growth factor binding.