Differential effects of buthionine sulphoximine in hypoxic and non-hypoxic regions of human cervical carcinoma xenografts

Background and Purpose: Recently we reported increased glutathione (GSH) levels in hypoxic regions of ME 180 and SiHa cervical cancer xenografts. Since this association might act synergistically to protect from radiotherapy, we examined the differential effects of the GSH depleting agent buthionine suiphoximine (BSO) in relation to tumor oxygenation. Materials and methods: The nitroimidazole EF5 was used to label tumor hypoxia. GSH levels were determined in cryostat sections using a sensitive HPLC assay and in parallel sections using fluorescence image analysis. Using a dual-labeling method, GSH levels were determined selectively in hypoxic and non-hypoxic tumor regions. Results: GSH levels were higher in hypoxic than in non-hypoxic regions of cervical carcinoma xenografts. Treatment with BSO produced a more pronounced GSH depletion in regions of hypoxia, resulting in similar post-treatment levels in hypoxic and non-hypoxic areas. Conclusions: BSO effectively depletes GSH in hypoxic microregions of tumors. These findings suggest a potential role for BSO as an adjunct to radiotherapy in cervical cancer patients. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.