Iodoazomycin riboside (1-(5'-iodo-5'-deoxyribofuranosyl)-2-nitroimidazole), a hypoxic cell marker. I. Synthesis and in vitro characterization.
Misonidazole (MISO), a selective radiosensitizer of hypoxic cells, forms adducts with cellular biomolecules with rates which are 30-50 X higher under hypoxic as compared to aerobic conditions of incubation. This technique of sensitizer adduct formation was proposed as a possible means of measuring the hypoxic fraction of solid tumors by noninvasive procedures. Iodoazomycin riboside (5'-IAZR) and 5'-[125I]AZR were synthesized and chemically characterized. Measurements of in vitro cytotoxicity and radiosensitizing ability with EMT-6 tumor cells in vitro indicated that 5'-IAZR is approximately 3 X more toxic and effective than is azomycin riboside (AZR) and approximately 10 X more toxic and effective than is MISO. 5'-[125I]AZR was shown to selectively bind to hypoxic EMT-6 cells at rates which were 2.5-3 X faster than those of MISO. The absolute rates of binding of 5'-IAZR to hypoxic cells at concentrations of 10-100 microM are the highest observed in this laboratory for any hypoxic cell radiosensitizer tested to date. These data suggest that 5'-IAZR, when labeled with an appropriate radioisotope (e.g., 131I), might be a useful marker for hypoxic cells in solid tumors amenable to noninvasive detection. Additional studies with animal tumor models appear to be warranted.
D000818:Animals; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D051379:Mice; D009374:Neoplasms, Experimental / Q000473:pathology*; D009593:Nitroimidazoles / Q000138:chemical synthesis* / Q000494:pharmacology; D010100:Oxygen / Q000502:physiology*; D011838:Radiation-Sensitizing Agents / Q000138:chemical synthesis* / Q000494:pharmacology
D007457:Iodine Radioisotopes; D009593:Nitroimidazoles; D011838:Radiation-Sensitizing Agents; C048114:iodoazomycin riboside; D010100:Oxygen