Toxicity of 3-nitronaphthalimides to V79 379A Chinese hamster cells

Fluorescent markers for hypoxic cells. A study of novel heterocyclic compounds that undergo bio-reductive binding

The bioreductive metabolism and binding of nitroaromatic compounds has been suggested as a method for the identification of hypoxic tumour cells. Bound metabolites of suitable nitroaryl compounds (and some other reducible aromatic compounds) may fluoresce, offering an alternative to radiolabelling or NMR etc. as a diagnostic method. In this paper, the synthesis of some heteroaromatic nitro-compounds is given together with the results obtained from testing of these and other mainly nitroaromatic compounds in vitro as potential bioreductive fluorescent probes for hypoxic cells in tumours. Compounds were incubated with oxygenated or hypoxic mammalian cell suspensions for various times before evaluation of the cellular fluorescence from bioreductive metabolites by fluorescence microscopy and flow cytometry. Among those compounds yielding fluorescent metabolites in cells, considerable variation in hypoxic:oxic differential fluorescence was observed. The in vitro mammalian cell test system showed several of the compounds to be sufficiently promising to merit further investigation in vivo.

Flow cytometric evaluation of hypoxic cells in solid experimental tumours using fluorescence immunodetection

Numerous methods have been proposed for the detection of hypoxic cells using nitroimidazoles labelled with both radioactive and stable isotopes where the isotopic label becomes bound as a result of reductive metabolism of the nitro group. A new probe for hypoxia, 7-(4'-(2-nitroimidazol-l-yl)-butyl)-theophylline, is described where an immunologically recognisable hapten (theophylline) is covalently linked to a 2-nitroimidazole. Bioreduction of the nitroimidazole leads to binding of bioreductive metabolites, and hence the theophylline side-chain, to intracellular molecules. Immunochemical procedures are then used to stain cells containing the bound theophylline using an FITC-conjugated anti-serum. Flow cytometric analysis of stained cells is facilitated by co-staining cellular DNA, which allows discrimination of single cells in the sample and rejection of cell clumps and debris. The alternative use of an immunoperoxidase-conjugated anti-serum has been used to demonstrate the localisation of hypoxic cells in frozen tumour sections.