Spatial characterization of glutathione depletion in the KHT sarcoma using flow cytometry

Intravenous administration of the fluorescent DNA stain Hoechst 33342 to tumour-bearing mice was used to label cells proportionally to their proximity from the vasculature. Flow cytometry was used to sort cells from the tumour into populations based on their Hoechst 33342-derived fluorescence. The cell populations were then assayed for their glutathione (GSH) content and their radiosensitivity. Tumours from mice pretreated with buthionine sulphoximine (BSO) were compared with untreated animals. The major findings of this study suggest that the cellular GSH concentration within tumours decreases with distance from the vasculature, and that the GSH concentration within cells from all locations in the tumour can be depleted by enzymatically inhibiting its synthesis using BSO. This depletion of GSH resulted in a small degree of hypoxic radiosensitization of cells both distal and proximal to the vasculature.