Under low
oxygen conditions, non-
protein thiols (NPSHs, non-
protein sulfhydryls) can effectively compete for
DNA radicals sites and hence represent a potentially important cause of radiation resistance in the clinic. Intra- and intertumoral heterogeneity of
glutathione (GSH) and
cysteine were assessed in cryostat sections of multiple biopsies obtained from 10 cervical
carcinomas by the combined use of a sensitive high-performance liquid chromatography (HPLC) method and a fluorescence image analysis technique to examine the spatial distribution of NPSHs in
tumor tissue.
Glutathione concentrations ranged from 1.98 to 4.42 mM; significant (> or =1 mM) concentrations of
cysteine, a more effective radioprotector than GSH, were found in some
tumors. By HPLC, the intratumoral heterogeneity of NPSHs was relatively small compared with the intertumoral heterogeneity. The histochemical
stain 1-(4-chloromercuryphenoylazo)-2-napthol (
mercury orange), which binds to GSH and
cysteine, was used to determine the spatial distribution of NPSHs in
tumor tissue. A comparison of NPSH levels in serial cryostat sections showed a close correlation between NPSH values determined by HPLC and
mercury orange fluorescence quantification. Using fluorescence image analysis, an approximately 2-fold increase of NPSHs in
tumor versus nonmalignant tissue was observed in the same section. Because some cervical
carcinomas contain radiobiologically important levels of
cysteine, agents that target the biochemical pathways maintaining
tumor cysteine have therapeutic potential as adjuncts to
radiotherapy in
cervix cancer patients.