Association between tissue hypoxia and elevated non-protein sulphydryl concentrations in human cervical carcinoma xenografts

A double staining technique was developed for the simultaneous measurement of tissue hypoxia and the concentration of non-protein sulphydryls (NPSH), based on the fluorinated nitroimidazole EF5 and the fluorescent histochemic al NPSH stain 1-(4-chloromercuriphenoylazo)-naphthol-2 (mercury orange), Cr yostat sections of tumour tissue were examined by fluorescence image analys is. using a computer-controlled microscope stage to generate large tiled fi eld images of the cut tumour surface, This method was applied to the human cervical squamous cell carcinoma lines ME180 and SiHa, grown as xenografts in severe combined immunodeficient (SCID) mice, in order to determine ii th ere is a systematic relationship between tissue hypoxia and NPSH levels. Hy poxic regions of the tumours, defined by EF5 labelling, were found to show greater NPSH concentrations relative to better oxygenated regions. This is probably due to increases in glutathione, since the ME180 and SiHa xenograf ts contained low levels of cysteine and metallothionein; the other major ce llular thiols that can bind to mercury orange, Because the effects of gluta thione on radiation and chemotherapy resistance are likely to be greater un der hypoxic conditions, these results have potentially important implicatio ns for the study of resistance mechanisms in solid tumours. (C) 1999 Cancer Research Campaign.