ABSTRACT
A high-performance liquid chromatography (HPLC) device equipped with an anion exchange column was used to isolate nca 77As from reactor irradiated natGeO2 targets. The oxidation states of the isotope 77As during the process was verified by thin layer chromatography. The radionuclidic purity of the separated fractions was checked by gamma measurements and it was found to be 99.91% for the As fraction. The elaborated method was applied to separate the isotope 74As from cyclotron irradiated natGeO2 targets too.
ABSTRACT
AIM: 5-Iodo-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl) uracil (FIAU) has been used for non-invasive monitoring of gene therapy and as an antiviral agent experimentally and in patients. However, FIAU metabolism in tumor cells is largely unknown. Here, the biological characteristics of FIAU in human leukemia and lymphoma cells in vitro and in a xenotransplant severe combined immunodeficient (SCID)-mouse model were investigated. METHODS: The susceptibility of FIAU to glycosidic bond cleavage by thymidine phosphorylase (TP) and its phosphorylation by human thymidine kinase 1 (hTK1) were examined. Cellular uptake and DNA-incorporation were determined in the leukemia cell line HL60 and the lymphoma cell line DoHH2. Biodistribution, in vivo stability of FIAU and expression of proliferation marker(67)Ki and thymidylate synthase were assessed in SCID-mice bearing HL60 xenotransplants. Cellular distribution of FIAU was imaged by microautoradiography. RESULTS: FIAU proved to be stable against degradation by TP and was phosphorylated by hTK1. Significant cellular uptake in DoHH2 and in HL60 cells was observed. The majority of intracellular [(131)I]FIAU was DNA incorporated. In vivo, moderate dehalogenation of [(131)I]FIAU was observed. Biodistribution studies showed a tumor uptake of 1.8+/-0.4% ID/g after 30 min. The half-life of [(131)I]FIAU in blood was 43+/-2 min. Microautoradiography showed a modest accumulation of [(125)I]FIAU in proliferating cells of small intestine, spleen and tumor. CONCLUSION: Despite phosphorylation by the hTK, efficient incorporation into the DNA and high in vivo stability, FIAU accumulates only moderately and transiently in proliferating cells, suggesting that FIAU is probably not appropriate for imaging of proliferation.
Subject(s)
Antiviral Agents/chemistry , Arabinofuranosyluracil/analogs & derivatives , DNA/chemistry , Animals , Antiviral Agents/pharmacokinetics , Arabinofuranosyluracil/chemistry , Arabinofuranosyluracil/pharmacokinetics , Cell Line, Tumor , Chemistry, Pharmaceutical/methods , HL-60 Cells , Humans , Mice , Mice, SCID , Neoplasm Transplantation , Phosphorylation , Thymidine Kinase/metabolism , Thymidine Phosphorylase/metabolism , Tissue DistributionABSTRACT
We used a murine tumor progression model for the evaluation of potential proliferation markers using positron emission tomography (PET). 5-[(18)F]-2'-deoxyuridine ([(18)F]FdUrd) was synthesized with >98% radiochemical purity and investigated in a pancreatic cancer model, transforming growth factor alpha transgenic mice crossbred to p53 deficient mice. Thymidylate synthase was increased already in premalignant lesions, whereas thymidine kinase 1 mRNA levels were up-regulated 4-fold in the pancreatic cancer specimen of these mice. PET imaging was performed after injection of 1 MBq of [(18)F]FdUrd and 1 MBq of [(18)F]fluoro-deoxyglucose. Animals with pancreatic cancer displayed focal uptake of both tracers. The [(18)F]FdUrd uptake ratio closely correlated with the proliferation index as evaluated in morphometric and fluorescence-activated cell sorter analysis. These results indicate the potential of our tumor model for the evaluation of PET tracers and suggest [(18)F]FdUrd as a tracer for the assessment of proliferation in vivo.
