Co-localization of hypoxia and apoptosis in irradiated and untreated HCT116 human colon carcinoma xenografts.

HCT116 human colon carcinoma xenografts were grown in nude mice. Frozen sections of control and irradiated tumors were stained and analysed for the distribution and extent of hypoxia and apoptosis. Tissue oxygen partial pressure was measured by immunohistochemical staining of hypoxia-dependent metabolites of the 2-nitroimidazole EF5. Apoptosis was assessed using a commercial kit which stains damaged DNA. Although the apoptosis stain was unlikely to exclude other forms of cell death (necrosis, pyknosis) all staining was found to associate with regions of near anoxia.